xref: /lighttpd1.4/src/mod_mbedtls.c (revision 9570cc2f)

/*
 * mod_mbedtls - mbedTLS support for lighttpd
 *
 * Copyright(c) 2020 Glenn Strauss gstrauss()gluelogic.com  All rights reserved
 * License: BSD 3-clause (same as lighttpd)
 */
/*
 * reference:
 * https://tls.mbed.org/high-level-design
 * https://tls.mbed.org/tech-updates/blog/mbedtls-2.0-defaults-best-practices
 * mbedTLS header files (mbedtls/ssl.h and others) are extremely well-documented
 * https://tls.mbed.org/api/  (generated from mbedTLS headers and code)
 *
 * mbedTLS limitations:
 * - mbedTLS does not currently support TLSv1.3
 * - mbedTLS does not currently support OCSP
 *   https://tls.mbed.org/discussions/feature-request/ocsp-stapling
 *   TLS/DTLS: OCSP Stapling support #880
 *   https://github.com/ARMmbed/mbedtls/issues/880
 *   Add support for writing OCSP requests and parsing OCSP responses #1197
 *   https://github.com/ARMmbed/mbedtls/issues/1197
 *
 * future possible enhancements to lighttpd mod_mbedtls:
 * - session cache (though session tickets are implemented)
 *     sample code in mbedtls:programs/ssl/ssl_server2.c
 *
 * Note: session tickets are disabled by default
 *   If enabled, mbedtls rotates the session ticket key according to 2x timeout
 *   set with mbedtls_ssl_ticket_setup() (currently 43200 sec in mod_mbedtls).
 *   This is fine for use with a single lighttpd instance, but with multiple
 *   lighttpd workers, no coordinated STEK (server ticket encryption key)
 *   rotation occurs other than by (some external job) restarting lighttpd.
 *   Restarting lighttpd generates a new key that is shared by lighttpd workers
 *   for the lifetime of the new key.  If the rotation period expires and
 *   lighttpd has not been restarted, lighttpd workers will generate new
 *   independent keys, making session tickets less effective for session
 *   resumption, since clients have a lower chance for future connections to
 *   reach the same lighttpd worker.  However, things will still work, and a new
 *   session will be created if session resumption fails.  Admins should plan to
 *   restart lighttpd at least every 24 hours if session tickets are enabled and
 *   multiple lighttpd workers are configured.
 */
#include "first.h"

#include <errno.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>      /* vsnprintf() */
#include <string.h>
#include <unistd.h>

#include <mbedtls/ctr_drbg.h>
#include <mbedtls/dhm.h>
#include <mbedtls/error.h>
#include <mbedtls/entropy.h>
#include <mbedtls/oid.h>
#include <mbedtls/pem.h>
#include <mbedtls/ssl.h>
#include <mbedtls/ssl_internal.h> /* struct mbedtls_ssl_transform */
#include <mbedtls/x509.h>
#include <mbedtls/x509_crt.h>
#include <mbedtls/version.h>

#if MBEDTLS_VERSION_NUMBER >= 0x02040000 /* mbedtls 2.04.0 */
#include <mbedtls/net_sockets.h>
#else
#include <mbedtls/net.h>
#endif

#if defined(MBEDTLS_SSL_TICKET_C)
#include <mbedtls/ssl_ticket.h>
#endif

#ifndef MBEDTLS_X509_CRT_PARSE_C
#error "lighttpd requires that mbedtls be built with MBEDTLS_X509_CRT_PARSE_C"
#endif

#include "base.h"
#include "http_header.h"
#include "log.h"
#include "plugin.h"

typedef struct {
    /* SNI per host: with COMP_SERVER_SOCKET, COMP_HTTP_SCHEME, COMP_HTTP_HOST */
    mbedtls_pk_context ssl_pemfile_pkey;/* parsed private key structure */
    mbedtls_x509_crt ssl_pemfile_x509;  /* parsed public key structure */
    const buffer *ssl_pemfile;
    const buffer *ssl_privkey;
    int8_t need_chain;
} plugin_cert;

typedef struct {
    mbedtls_ssl_config *ssl_ctx;        /* context shared between mbedtls_ssl_CONTEXT structures */
    int *ciphersuites;
    mbedtls_ecp_group_id *curves;
} plugin_ssl_ctx;

typedef struct {
    mbedtls_ssl_config *ssl_ctx;        /* output from network_init_ssl() */
    int *ciphersuites;                  /* output from network_init_ssl() */
    mbedtls_ecp_group_id *curves;       /* output from network_init_ssl() */

    /*(used only during startup; not patched)*/
    unsigned char ssl_enabled; /* only interesting for setting up listening sockets. don't use at runtime */
    unsigned char ssl_honor_cipher_order; /* determine SSL cipher in server-preferred order, not client-order */
    unsigned char ssl_empty_fragments;
    unsigned char ssl_use_sslv2;
    unsigned char ssl_use_sslv3;
    const buffer *ssl_cipher_list;
    const buffer *ssl_dh_file;
    const buffer *ssl_ec_curve;
    const buffer *ssl_acme_tls_1;
    array *ssl_conf_cmd;

    /*(copied from plugin_data for socket ssl_ctx config)*/
    plugin_cert *pc;
    mbedtls_pk_context *ssl_pemfile_pkey; /* parsed private key structure */
    mbedtls_x509_crt *ssl_pemfile_x509;   /* parsed public key structure */
    mbedtls_x509_crt *ssl_ca_file;
    const buffer *ssl_pemfile;
    const buffer *ssl_privkey;
    unsigned char ssl_session_ticket;
    unsigned char ssl_verifyclient;
    unsigned char ssl_verifyclient_enforce;
    unsigned char ssl_verifyclient_depth;
} plugin_config_socket; /*(used at startup during configuration)*/

typedef struct {
    /* SNI per host: w/ COMP_SERVER_SOCKET, COMP_HTTP_SCHEME, COMP_HTTP_HOST */
    plugin_cert *pc;
    mbedtls_pk_context *ssl_pemfile_pkey; /* parsed private key structure */
    mbedtls_x509_crt *ssl_pemfile_x509;   /* parsed public key structure */
    const buffer *ssl_pemfile;
    mbedtls_x509_crt *ssl_ca_file;
    mbedtls_x509_crt *ssl_ca_dn_file;
    mbedtls_x509_crl *ssl_ca_crl_file;

    unsigned char ssl_verifyclient;
    unsigned char ssl_verifyclient_enforce;
    unsigned char ssl_verifyclient_depth;
    unsigned char ssl_verifyclient_export_cert;
    unsigned char ssl_read_ahead;
    unsigned char ssl_log_noise;
    unsigned char ssl_disable_client_renegotiation;
    const buffer *ssl_verifyclient_username;
    const buffer *ssl_acme_tls_1;
} plugin_config;

typedef struct {
    PLUGIN_DATA;
    plugin_ssl_ctx *ssl_ctxs;
    plugin_config defaults;
    server *srv;
    /* NIST counter-mode deterministic random byte generator */
    mbedtls_ctr_drbg_context ctr_drbg;
    /* entropy collection and state management */
    mbedtls_entropy_context entropy;
  #if defined(MBEDTLS_SSL_SESSION_TICKETS)
    mbedtls_ssl_ticket_context ticket_ctx;
  #endif
} plugin_data;

static int ssl_is_init;
/* need assigned p->id for deep access of module handler_ctx for connection
 *   i.e. handler_ctx *hctx = r->plugin_ctx[plugin_data_singleton->id]; */
static plugin_data *plugin_data_singleton;
#define LOCAL_SEND_BUFSIZE MBEDTLS_SSL_MAX_CONTENT_LEN
static char *local_send_buffer;

typedef struct {
    mbedtls_ssl_context ssl;      /* mbedtls request/connection context */
    request_st *r;
    connection *con;
    int8_t request_env_patched;
    int8_t close_notify;
    unsigned short alpn;
    int handshake_done;
    size_t pending_write;
    plugin_config conf;
    buffer *tmp_buf;
    mbedtls_pk_context *acme_tls_1_pkey;
    mbedtls_x509_crt *acme_tls_1_x509;
} handler_ctx;


static handler_ctx *
handler_ctx_init (void)
{
    handler_ctx *hctx = calloc(1, sizeof(*hctx));
    force_assert(hctx);
    return hctx;
}


static void
handler_ctx_free (handler_ctx *hctx)
{
    mbedtls_ssl_free(&hctx->ssl);
    if (hctx->acme_tls_1_pkey) {
        mbedtls_pk_free(hctx->acme_tls_1_pkey);
        free(hctx->acme_tls_1_pkey);
    }
    if (hctx->acme_tls_1_x509) {
        mbedtls_x509_crt_free(hctx->acme_tls_1_x509);
        free(hctx->acme_tls_1_x509);
    }
    free(hctx);
}


#ifdef MBEDTLS_ERROR_C
__attribute_cold__
static void elog(log_error_st * const errh,
                 const char * const file, const int line,
                 const int rc, const char * const msg)
{
    /* error logging convenience function that decodes mbedtls result codes */
    char buf[256];
    mbedtls_strerror(rc, buf, sizeof(buf));
    log_error(errh, file, line, "MTLS: %s: %s (-0x%04x)", msg, buf, -rc);
}
#else
#define elog(errh, file, line, rc, msg) \
    log_error((errh), (file), (line), "MTLS: %s: (-0x%04x)", (msg), -(rc))
#endif


__attribute_cold__
__attribute_format__((__printf__, 5, 6))
static void elogf(log_error_st * const errh,
                  const char * const file, const int line,
                  const int rc, const char * const fmt, ...)
{
    char msg[1024];
    va_list ap;
    va_start(ap, fmt);
    vsnprintf(msg, sizeof(msg), fmt, ap);
    va_end(ap);
    elog(errh, file, line, rc, msg);
}


INIT_FUNC(mod_mbedtls_init)
{
    plugin_data_singleton = (plugin_data *)calloc(1, sizeof(plugin_data));
  #if defined(MBEDTLS_SSL_SESSION_TICKETS)
    mbedtls_ssl_ticket_init(&plugin_data_singleton->ticket_ctx);
  #endif
    return plugin_data_singleton;
}


static int mod_mbedtls_init_once_mbedtls (server *srv)
{
    if (ssl_is_init) return 1;
    ssl_is_init = 1;

    plugin_data * const p = plugin_data_singleton;
    mbedtls_ctr_drbg_init(&p->ctr_drbg); /* init empty NSIT random num gen */
    mbedtls_entropy_init(&p->entropy);   /* init empty entropy collection struct
                                               .. could add sources here too */

    int rc =                                      /* init RNG */
      mbedtls_ctr_drbg_seed(&p->ctr_drbg,         /* random number generator */
                            mbedtls_entropy_func, /* default entropy func */
                            &p->entropy,          /* entropy context */
                            NULL, 0);             /* no personalization data */
    if (0 != rc) {
        elog(srv->errh, __FILE__,__LINE__, rc,
             "Init of random number generator failed");
        return 0;
    }

    local_send_buffer = malloc(LOCAL_SEND_BUFSIZE);
    force_assert(NULL != local_send_buffer);

    return 1;
}


static void mod_mbedtls_free_mbedtls (void)
{
    if (!ssl_is_init) return;

    plugin_data * const p = plugin_data_singleton;
    mbedtls_ctr_drbg_free(&p->ctr_drbg);
    mbedtls_entropy_free(&p->entropy);
  #if defined(MBEDTLS_SSL_SESSION_TICKETS)
    mbedtls_ssl_ticket_free(&p->ticket_ctx);
  #endif

    free(local_send_buffer);
    ssl_is_init = 0;
}


static void
mod_mbedtls_free_config (server *srv, plugin_data * const p)
{
    if (NULL != p->ssl_ctxs) {
        mbedtls_ssl_config * const ssl_ctx_global_scope = p->ssl_ctxs->ssl_ctx;
        /* free ssl_ctx from $SERVER["socket"] (if not copy of global scope) */
        for (uint32_t i = 1; i < srv->config_context->used; ++i) {
            plugin_ssl_ctx * const s = p->ssl_ctxs + i;
            if (s->ssl_ctx && s->ssl_ctx != ssl_ctx_global_scope) {
                mbedtls_ssl_config_free(s->ssl_ctx);
                free(s->ciphersuites);
                free(s->curves);
            }
        }
        /* free ssl_ctx from global scope */
        if (ssl_ctx_global_scope) {
            mbedtls_ssl_config_free(ssl_ctx_global_scope);
            free(p->ssl_ctxs[0].ciphersuites);
            free(p->ssl_ctxs[0].curves);
        }
        free(p->ssl_ctxs);
    }

    if (NULL == p->cvlist) return;
    /* (init i to 0 if global context; to 1 to skip empty global context) */
    for (int i = !p->cvlist[0].v.u2[1], used = p->nconfig; i < used; ++i) {
        config_plugin_value_t *cpv = p->cvlist + p->cvlist[i].v.u2[0];
        for (; -1 != cpv->k_id; ++cpv) {
            switch (cpv->k_id) {
              case 0: /* ssl.pemfile */
                if (cpv->vtype == T_CONFIG_LOCAL) {
                    plugin_cert *pc = cpv->v.v;
                    mbedtls_pk_free(&pc->ssl_pemfile_pkey);
                    mbedtls_x509_crt_free(&pc->ssl_pemfile_x509);
                }
                break;
              case 2: /* ssl.ca-file */
              case 3: /* ssl.ca-dn-file */
                if (cpv->vtype == T_CONFIG_LOCAL) {
                    mbedtls_x509_crt *cacert = cpv->v.v;
                    mbedtls_x509_crt_free(cacert);
                    free(cacert);
                }
                break;
              case 4: /* ssl.ca-dn-file */
                if (cpv->vtype == T_CONFIG_LOCAL) {
                    mbedtls_x509_crl *crl = cpv->v.v;
                    mbedtls_x509_crl_free(crl);
                    free(crl);
                }
                break;
              default:
                break;
            }
        }
    }
}


FREE_FUNC(mod_mbedtls_free)
{
    plugin_data *p = p_d;
    if (NULL == p->srv) return;
    mod_mbedtls_free_config(p->srv, p);
    mod_mbedtls_free_mbedtls();
}


static void
mod_mbedtls_merge_config_cpv (plugin_config * const pconf, const config_plugin_value_t * const cpv)
{
    switch (cpv->k_id) { /* index into static config_plugin_keys_t cpk[] */
      case 0: /* ssl.pemfile */
        if (cpv->vtype == T_CONFIG_LOCAL)
            pconf->pc = cpv->v.v;
        break;
      case 1: /* ssl.privkey */
        break;
      case 2: /* ssl.ca-file */
        if (cpv->vtype == T_CONFIG_LOCAL)
            pconf->ssl_ca_file = cpv->v.v;
        break;
      case 3: /* ssl.ca-dn-file */
        if (cpv->vtype == T_CONFIG_LOCAL)
            pconf->ssl_ca_dn_file = cpv->v.v;
        break;
      case 4: /* ssl.ca-crl-file */
        if (cpv->vtype == T_CONFIG_LOCAL)
            pconf->ssl_ca_dn_file = cpv->v.v;
        break;
      case 5: /* ssl.read-ahead */
        pconf->ssl_read_ahead = (0 != cpv->v.u);
        break;
      case 6: /* ssl.disable-client-renegotiation */
        pconf->ssl_disable_client_renegotiation = (0 != cpv->v.u);
        break;
      case 7: /* ssl.verifyclient.activate */
        pconf->ssl_verifyclient = (0 != cpv->v.u);
        break;
      case 8: /* ssl.verifyclient.enforce */
        pconf->ssl_verifyclient_enforce = (0 != cpv->v.u);
        break;
      case 9: /* ssl.verifyclient.depth */
        pconf->ssl_verifyclient_depth = (unsigned char)cpv->v.shrt;
        break;
      case 10:/* ssl.verifyclient.username */
        pconf->ssl_verifyclient_username = cpv->v.b;
        break;
      case 11:/* ssl.verifyclient.exportcert */
        pconf->ssl_verifyclient_export_cert = (0 != cpv->v.u);
        break;
      case 12:/* ssl.acme-tls-1 */
        pconf->ssl_acme_tls_1 = cpv->v.b;
        break;
      case 13:/* debug.log-ssl-noise */
        pconf->ssl_log_noise = (unsigned char)cpv->v.shrt;
        break;
      default:/* should not happen */
        return;
    }
}


static void
mod_mbedtls_merge_config(plugin_config * const pconf, const config_plugin_value_t *cpv)
{
    do {
        mod_mbedtls_merge_config_cpv(pconf, cpv);
    } while ((++cpv)->k_id != -1);
}


static void
mod_mbedtls_patch_config (request_st * const r, plugin_config * const pconf)
{
    plugin_data * const p = plugin_data_singleton;
    memcpy(pconf, &p->defaults, sizeof(plugin_config));
    for (int i = 1, used = p->nconfig; i < used; ++i) {
        if (config_check_cond(r, (uint32_t)p->cvlist[i].k_id))
            mod_mbedtls_merge_config(pconf, p->cvlist + p->cvlist[i].v.u2[0]);
    }
}


__attribute_pure__
static int
mod_mbedtls_crt_is_self_issued (const mbedtls_x509_crt * const crt)
{
    const mbedtls_x509_buf * const issuer  = &crt->issuer_raw;
    const mbedtls_x509_buf * const subject = &crt->subject_raw;
    return subject->len == issuer->len
        && 0 == memcmp(issuer->p, subject->p, subject->len);
}


static int
mod_mbedtls_construct_crt_chain (mbedtls_x509_crt *leaf, mbedtls_x509_crt *store, log_error_st *errh)
{
    /* Historically, openssl will use the cert chain in (SSL_CTX *) if a cert
     * does not have a chain configured in (SSL *).  While similar behavior
     * could be achieved with mbedtls_x509_crt_parse_file(crt, ssl_ca_file->ptr)
     * instead attempt to do better and build a proper, ordered cert chain. */

    if (leaf->next) return 0; /*(presume chain has already been provided)*/
    if (store == NULL) return 0;/*(unable to proceed; chain may be incomplete)*/

    /* attempt to construct certificate chain from certificate store */
    for (mbedtls_x509_crt *crt = leaf; crt; ) {
        const mbedtls_x509_buf * const issuer = &crt->issuer_raw;

        /*(walk entire store in case certs are not properly sorted)*/
        for (crt = store; crt; crt = crt->next) {
            /* The raw issuer/subject data (DER) is used for quick comparison */
            /* (see comments in mod_mbedtls_verify_cb())*/
            const mbedtls_x509_buf * const subject = &crt->subject_raw;
            if (issuer->len != subject->len
                || 0 != memcmp(subject->p, issuer->p, issuer->len)) continue;

            /* root cert is end condition; omit from chain of intermediates */
            if (mod_mbedtls_crt_is_self_issued(crt))
                return 0;

            int rc =
          #if MBEDTLS_VERSION_NUMBER >= 0x02110000 /* mbedtls 2.17.0 */
              /* save memory by eliding copy of already-loaded raw DER */
              mbedtls_x509_crt_parse_der_nocopy(leaf, crt->raw.p, crt->raw.len);
          #else
              mbedtls_x509_crt_parse_der(leaf, crt->raw.p, crt->raw.len);
          #endif
            if (0 != rc) { /*(failure not unexpected since already parsed)*/
                elog(errh, __FILE__, __LINE__, rc, "cert copy failed");
                return rc;
            }
            break;
        }
    }

    return 0; /*(no error, though cert chain may or may not be complete)*/
}


static int
mod_mbedtls_verify_cb (void *arg, mbedtls_x509_crt *crt, int depth, uint32_t *flags)
{
    handler_ctx * const hctx = (handler_ctx *)arg;

    if (depth > hctx->conf.ssl_verifyclient_depth) {
        log_error(hctx->r->conf.errh, __FILE__, __LINE__,
                  "MTLS: client cert chain too long");
        *flags |= MBEDTLS_X509_BADCERT_OTHER; /* cert chain too long */
    }
    else if (0 == depth && NULL != hctx->conf.ssl_ca_dn_file) {
        /* verify that client cert is issued by CA in ssl.ca-dn-file
         * if both ssl.ca-dn-file and ssl.ca-file were configured */
        /* The raw issuer/subject data (DER) is used for quick comparison. */
        const size_t len = crt->issuer_raw.len;
        mbedtls_x509_crt *chain = hctx->conf.ssl_ca_dn_file;
        do {
          #if 0 /* x509_name_cmp() is not a public func in mbedtls */
            if (0 == x509_name_cmp(&crt->issuer, &chain->subject))
                break;
          #else
            if (len == chain->subject_raw.len
                && 0 == memcmp(chain->subject_raw.p, crt->issuer_raw.p, len))
                break;
          #endif
        } while ((chain = chain->next));

        if (NULL == chain)
            *flags |= MBEDTLS_X509_BADCERT_NOT_TRUSTED;
    }
    if (*flags & MBEDTLS_X509_BADCERT_NOT_TRUSTED) {
        log_error(hctx->r->conf.errh, __FILE__, __LINE__,
                  "MTLS: client cert not trusted");
    }

    return 0;
}


#ifdef MBEDTLS_SSL_SERVER_NAME_INDICATION
static int
mod_mbedtls_SNI (void *arg, mbedtls_ssl_context *ssl, const unsigned char *servername, size_t len)
{
    handler_ctx * const hctx = (handler_ctx *) arg;
    buffer_copy_string(&hctx->r->uri.scheme, "https");

    request_st * const r = hctx->r;
    if (len >= 1024) { /*(expecting < 256; TLSEXT_MAXLEN_host_name is 255)*/
        log_error(r->conf.errh, __FILE__, __LINE__,
                  "MTLS: SNI name too long %.*s", (int)len, servername);
        return MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO;
    }

    /* use SNI to patch mod_mbedtls config and then reset COMP_HTTP_HOST */
    buffer_copy_string_len(&r->uri.authority, (const char *)servername, len);
    buffer_to_lower(&r->uri.authority);
  #if 0
    /*(r->uri.authority used below for configuration before request read;
     * revisit for h2)*/
    if (0 != http_request_host_policy(&r->uri.authority,
                                      r->conf.http_parseopts, 443))
        return MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO;
  #endif

    const buffer * const ssl_pemfile = hctx->conf.pc->ssl_pemfile;

    r->conditional_is_valid |= (1 << COMP_HTTP_SCHEME)
                            |  (1 << COMP_HTTP_HOST);

    mod_mbedtls_patch_config(r, &hctx->conf);
    /* reset COMP_HTTP_HOST so that conditions re-run after request hdrs read */
    /*(done in configfile-glue.c:config_cond_cache_reset() after request hdrs read)*/
    /*config_cond_cache_reset_item(r, COMP_HTTP_HOST);*/
    /*buffer_clear(&r->uri.authority);*/

    /*(compare strings as ssl.pemfile might repeat same file in lighttpd.conf
     * and mod_mbedtls does not attempt to de-dup)*/
    if (!buffer_is_equal(hctx->conf.pc->ssl_pemfile, ssl_pemfile)) {
        /* if needed, attempt to construct certificate chain for server cert */
        if (hctx->conf.pc->need_chain) {
            hctx->conf.pc->need_chain = 0; /*(attempt once to complete chain)*/
            mbedtls_x509_crt *ssl_cred = &hctx->conf.pc->ssl_pemfile_x509;
            mbedtls_x509_crt *store = hctx->conf.ssl_ca_file;
            if (!mod_mbedtls_construct_crt_chain(ssl_cred, store, r->conf.errh))
                return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
        }
        /* reconfigure to use SNI-specific cert */
        int rc =
          mbedtls_ssl_set_hs_own_cert(ssl,
                                      &hctx->conf.pc->ssl_pemfile_x509,
                                      &hctx->conf.pc->ssl_pemfile_pkey);
        if (0 != rc) {
            elogf(r->conf.errh, __FILE__, __LINE__, rc,
                  "failed to set SNI certificate for TLS server name %s",
                  r->uri.authority.ptr);
            return MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO;
        }
    }

    return 0;
}
#endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */


static int
mod_mbedtls_conf_verify (handler_ctx *hctx, mbedtls_ssl_config *ssl_ctx)
{
    if (NULL == hctx->conf.ssl_ca_file) {
        log_error(hctx->r->conf.errh, __FILE__, __LINE__,
          "MTLS: can't verify client without ssl.ca-file "
          "for TLS server name %s",
          hctx->r->uri.authority.ptr);
        return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
    }

    /* send ssl_ca_dn_file (if set) in client certificate request
     * (later changed to ssl_ca_file before client certificate verification) */
    mbedtls_x509_crt *ca_certs = hctx->conf.ssl_ca_dn_file
                               ? hctx->conf.ssl_ca_dn_file
                               : hctx->conf.ssl_ca_file;

    mbedtls_ssl_context * const ssl = &hctx->ssl;
    mbedtls_ssl_set_hs_ca_chain(ssl, ca_certs, hctx->conf.ssl_ca_crl_file);
  #if MBEDTLS_VERSION_NUMBER >= 0x02120000 /* mbedtls 2.18.0 */
    mbedtls_ssl_set_verify(ssl, mod_mbedtls_verify_cb, hctx);
  #else
    mbedtls_ssl_conf_verify(ssl_ctx, mod_mbedtls_verify_cb, hctx);
  #endif
    return 0;
}


static void *
network_mbedtls_load_pemfile (server *srv, const buffer *pemfile, const buffer *privkey)
{
    mbedtls_x509_crt ssl_pemfile_x509;   /* parsed public key structure */
    mbedtls_pk_context ssl_pemfile_pkey; /* parsed private key structure */
    int rc;

    mbedtls_x509_crt_init(&ssl_pemfile_x509); /* init cert structure */
    rc = mbedtls_x509_crt_parse_file(&ssl_pemfile_x509, pemfile->ptr);
    if (0 != rc) {
        elogf(srv->errh, __FILE__, __LINE__, rc,
              "PEM file cert read failed (%s)", pemfile->ptr);
        return NULL;
    }

    mbedtls_pk_init(&ssl_pemfile_pkey);  /* init private key context */
    rc = mbedtls_pk_parse_keyfile(&ssl_pemfile_pkey, privkey->ptr, NULL);
    if (0 != rc) {
        elogf(srv->errh, __FILE__, __LINE__, rc,
              "PEM file private key read failed %s", privkey->ptr);
        mbedtls_x509_crt_free(&ssl_pemfile_x509);
        return NULL;
    }

    rc = mbedtls_pk_check_pair(&ssl_pemfile_x509.pk, &ssl_pemfile_pkey);
    if (0 != rc) {
        elogf(srv->errh, __FILE__, __LINE__, rc,
              "PEM cert and private key did not verify (%s) (%s)",
              pemfile->ptr, privkey->ptr);
        mbedtls_pk_free(&ssl_pemfile_pkey);
        mbedtls_x509_crt_free(&ssl_pemfile_x509);
        return NULL;
    }

    plugin_cert *pc = malloc(sizeof(plugin_cert));
    force_assert(pc);
    pc->ssl_pemfile_pkey = ssl_pemfile_pkey;
    pc->ssl_pemfile_x509 = ssl_pemfile_x509;
    pc->ssl_pemfile = pemfile;
    pc->ssl_privkey = privkey;
    pc->need_chain = (ssl_pemfile_x509.next == NULL
                      && !mod_mbedtls_crt_is_self_issued(&ssl_pemfile_x509));
    mbedtls_platform_zeroize(&ssl_pemfile_pkey, sizeof(ssl_pemfile_pkey));
    return pc;
}


#ifdef MBEDTLS_SSL_ALPN

static int
mod_mbedtls_acme_tls_1 (handler_ctx *hctx)
{
    buffer * const b = hctx->tmp_buf;
    const buffer * const name = &hctx->r->uri.authority;
    log_error_st * const errh = hctx->r->conf.errh;
    mbedtls_x509_crt *ssl_pemfile_x509 = NULL;
    mbedtls_pk_context *ssl_pemfile_pkey = NULL;
    size_t len;
    int rc = MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO;

    /* check if acme-tls/1 protocol is enabled (path to dir of cert(s) is set)*/
    if (buffer_string_is_empty(hctx->conf.ssl_acme_tls_1))
        return 0; /*(should not happen)*/
    buffer_copy_buffer(b, hctx->conf.ssl_acme_tls_1);
    buffer_append_slash(b);

    /* check if SNI set server name (required for acme-tls/1 protocol)
     * and perform simple path checks for no '/'
     * and no leading '.' (e.g. ignore "." or ".." or anything beginning '.') */
    if (buffer_string_is_empty(name))   return rc;
    if (NULL != strchr(name->ptr, '/')) return rc;
    if (name->ptr[0] == '.')            return rc;
  #if 0
    if (0 != http_request_host_policy(name,hctx->r->conf.http_parseopts,443))
        return rc;
  #endif
    buffer_append_string_buffer(b, name);
    len = buffer_string_length(b);

    do {
        buffer_append_string_len(b, CONST_STR_LEN(".crt.pem"));
        ssl_pemfile_x509 = malloc(sizeof(*ssl_pemfile_x509));
        force_assert(ssl_pemfile_x509);
        mbedtls_x509_crt_init(ssl_pemfile_x509); /* init cert structure */
        rc = mbedtls_x509_crt_parse_file(ssl_pemfile_x509, b->ptr);
        if (0 != rc) {
            elogf(errh, __FILE__, __LINE__, rc,
                  "Failed to load acme-tls/1 pemfile: %s", b->ptr);
            break;
        }

        buffer_string_set_length(b, len); /*(remove ".crt.pem")*/
        buffer_append_string_len(b, CONST_STR_LEN(".key.pem"));
        ssl_pemfile_pkey = malloc(sizeof(*ssl_pemfile_pkey));
        force_assert(ssl_pemfile_pkey);
        mbedtls_pk_init(ssl_pemfile_pkey);  /* init private key context */
        rc = mbedtls_pk_parse_keyfile(ssl_pemfile_pkey, b->ptr, NULL);
        if (0 != rc) {
            elogf(errh, __FILE__, __LINE__, rc,
                  "Failed to load acme-tls/1 pemfile: %s", b->ptr);
            break;
        }

        rc = mbedtls_ssl_set_hs_own_cert(&hctx->ssl,
                                         ssl_pemfile_x509, ssl_pemfile_pkey);
        if (0 != rc) {
            elogf(errh, __FILE__, __LINE__, rc,
                  "failed to set acme-tls/1 certificate for TLS server "
                  "name %s", name->ptr);
            break;
        }

        hctx->acme_tls_1_pkey = ssl_pemfile_pkey; /* save ptr and free later */
        hctx->acme_tls_1_x509 = ssl_pemfile_x509; /* save ptr and free later */
        return 0;

    } while (0);

    if (ssl_pemfile_pkey) {
        mbedtls_pk_free(ssl_pemfile_pkey);
        free(ssl_pemfile_pkey);
    }
    if (ssl_pemfile_x509) {
        mbedtls_x509_crt_free(ssl_pemfile_x509);
        free(ssl_pemfile_x509);
    }

    return rc;
}


enum {
  MOD_MBEDTLS_ALPN_HTTP11      = 1
 ,MOD_MBEDTLS_ALPN_HTTP10      = 2
 ,MOD_MBEDTLS_ALPN_H2          = 3
 ,MOD_MBEDTLS_ALPN_ACME_TLS_1  = 4
};


static int
mod_mbedtls_alpn_select_cb (handler_ctx *hctx, const char *in)
{
    const int n = (int)strlen(in);
    const int i = 0;
    unsigned short proto;

    switch (n) {
     #if 0
      case 2:  /* "h2" */
        if (in[i] == 'h' && in[i+1] == '2') {
            proto = MOD_MBEDTLS_ALPN_H2;
            break;
        }
        return 0;
     #endif
      case 8:  /* "http/1.1" "http/1.0" */
        if (0 == memcmp(in+i, "http/1.", 7)) {
            if (in[i+7] == '1') {
                proto = MOD_MBEDTLS_ALPN_HTTP11;
                break;
            }
            if (in[i+7] == '0') {
                proto = MOD_MBEDTLS_ALPN_HTTP10;
                break;
            }
        }
        return 0;
      case 10: /* "acme-tls/1" */
        if (0 == memcmp(in+i, "acme-tls/1", 10)) {
            int rc = mod_mbedtls_acme_tls_1(hctx);
            if (0 == rc) {
                proto = MOD_MBEDTLS_ALPN_ACME_TLS_1;
                break;
            }
            return rc;
        }
        return 0;
      default:
        return 0;
    }

    hctx->alpn = proto;
    return 0;
}

#endif /* MBEDTLS_SSL_ALPN */


static int
mod_mbedtls_ssl_conf_ciphersuites (server *srv, plugin_config_socket *s, buffer *ciphersuites, const buffer *cipherstring);


static int
mod_mbedtls_ssl_conf_curves(server *srv, plugin_config_socket *s, const buffer *curvelist);


static void
mod_mbedtls_ssl_conf_proto (server *srv, plugin_config_socket *s, const buffer *b, int max);


static int
mod_mbedtls_ssl_conf_cmd (server *srv, plugin_config_socket *s)
{
    /* reference:
     * https://www.openssl.org/docs/man1.1.1/man3/SSL_CONF_cmd.html */
    int rc = 0;
    buffer *cipherstring = NULL;
    buffer *ciphersuites = NULL;

    for (size_t i = 0; i < s->ssl_conf_cmd->used; ++i) {
        data_string *ds = (data_string *)s->ssl_conf_cmd->data[i];
        if (buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("CipherString")))
            cipherstring = &ds->value;
        else if (buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("Ciphersuites")))
            ciphersuites = &ds->value;
        else if (buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("Curves"))
              || buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("Groups"))) {
            if (!mod_mbedtls_ssl_conf_curves(srv, s, &ds->value))
                rc = -1;
        }
        else if (buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("MaxProtocol")))
            mod_mbedtls_ssl_conf_proto(srv, s, &ds->value, 1); /* max */
        else if (buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("MinProtocol")))
            mod_mbedtls_ssl_conf_proto(srv, s, &ds->value, 0); /* min */
        else if (buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("Protocol"))) {
            /* openssl config for Protocol=... is complex and deprecated */
            log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: ssl.openssl.ssl-conf-cmd %s ignored; "
                      "use MinProtocol=... and MaxProtocol=... instead",
                      ds->key.ptr);
        }
        else if (buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("Options"))) {
            for (char *v = ds->value.ptr, *e; *v; v = e) {
                while (*v == ' ' || *v == '\t' || *v == ',') ++v;
                int flag = 1;
                if (*v == '-') {
                    flag = 0;
                    ++v;
                }
                for (e = v; light_isalpha(*e); ++e) ;
                switch ((int)(e-v)) {
                  case 11:
                    if (buffer_eq_icase_ssn(v, "Compression", 11)) {
                        /* mbedtls defaults to no record compression unless
                         * mbedtls is built with MBEDTLS_ZLIB_SUPPORT, which
                         * is deprecated and slated for removal*/
                        if (!flag) continue;
                    }
                    break;
                  case 13:
                    if (buffer_eq_icase_ssn(v, "SessionTicket", 13)) {
                        s->ssl_session_ticket = flag;
                        continue;
                    }
                    break;
                  case 16:
                    if (buffer_eq_icase_ssn(v, "ServerPreference", 16)) {
                        /* Note: The server uses its own preferences
                         * over the preference of the client unless
                         * MBEDTLS_SSL_SRV_RESPECT_CLIENT_PREFERENCE defined! */
                        s->ssl_honor_cipher_order = flag;
                        continue;
                    }
                    break;
                  default:
                    break;
                }
                /* warn if not explicitly handled or ignored above */
                if (!flag) --v;
                log_error(srv->errh, __FILE__, __LINE__,
                          "MTLS: ssl.openssl.ssl-conf-cmd Options %.*s ignored",
                          (int)(e-v), v);
            }
        }
      #if 0
        else if (buffer_eq_icase_slen(&ds->key, CONST_STR_LEN("..."))) {
        }
      #endif
        else {
            /* warn if not explicitly handled or ignored above */
            log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: ssl.openssl.ssl-conf-cmd %s ignored",
                      ds->key.ptr);
        }
    }

    if (!mod_mbedtls_ssl_conf_ciphersuites(srv, s, ciphersuites, cipherstring))
        rc = -1;

    return rc;
}


static int
network_init_ssl (server *srv, plugin_config_socket *s, plugin_data *p)
{
    int rc;

    s->ssl_ctx = malloc(sizeof(mbedtls_ssl_config));
    force_assert(s->ssl_ctx);
    mbedtls_ssl_config_init(s->ssl_ctx);

    /* set the RNG in the ssl config context, using the default random func */
    mbedtls_ssl_conf_rng(s->ssl_ctx, mbedtls_ctr_drbg_random, &p->ctr_drbg);

    /* mbedtls defaults to disable client renegotiation
     * mbedtls defaults to no record compression unless mbedtls is built
     *   with MBEDTLS_ZLIB_SUPPORT, which is deprecated and slated for removal
     * MBEDTLS_SSL_PRESET_SUITEB is stricter than MBEDTLS_SSL_PRESET_DEFAULT
     * (and is attempted to be supported in mod_mbedtls_ssl_conf_ciphersuites())
     * explanation: https://github.com/ARMmbed/mbedtls/issues/1591
     * reference: RFC 6460 */
    rc = mbedtls_ssl_config_defaults(s->ssl_ctx,
                                     MBEDTLS_SSL_IS_SERVER,
                                     MBEDTLS_SSL_TRANSPORT_STREAM,
                                     MBEDTLS_SSL_PRESET_DEFAULT);
    if (0 != rc) {
        elog(srv->errh, __FILE__,__LINE__, rc,
             "Init of ssl config context defaults failed");
        return -1;
    }

    /* mbedtls defaults minimum accepted SSL/TLS protocol version TLS v1.0
     * use of SSL v3 should be avoided, and SSL v2 is not supported */
    if (s->ssl_use_sslv3)
        mbedtls_ssl_conf_min_version(s->ssl_ctx, MBEDTLS_SSL_MAJOR_VERSION_3,
                                                 MBEDTLS_SSL_MINOR_VERSION_0);

    if (!buffer_string_is_empty(s->ssl_cipher_list)) {
        if (!mod_mbedtls_ssl_conf_ciphersuites(srv,s,NULL,s->ssl_cipher_list))
            return -1;
    }

    if (!buffer_string_is_empty(s->ssl_dh_file)) {
        mbedtls_dhm_context dhm;
        mbedtls_dhm_init(&dhm);
        rc = mbedtls_dhm_parse_dhmfile(&dhm, s->ssl_dh_file->ptr);
        if (0 != rc)
            elogf(srv->errh, __FILE__,__LINE__, rc,
                 "mbedtls_dhm_parse_dhmfile() %s", s->ssl_dh_file->ptr);
        else {
            rc = mbedtls_ssl_conf_dh_param_ctx(s->ssl_ctx, &dhm);
            if (0 != rc)
                elogf(srv->errh, __FILE__,__LINE__, rc,
                     "mbedtls_ssl_conf_dh_param_ctx() %s", s->ssl_dh_file->ptr);
        }
        mbedtls_dhm_free(&dhm);
        if (0 != rc)
            return -1;
    }

    if (!buffer_string_is_empty(s->ssl_ec_curve)) {
        if (!mod_mbedtls_ssl_conf_curves(srv, s, s->ssl_ec_curve))
            return -1;
    }

    /* if needed, attempt to construct certificate chain for server cert */
    if (s->pc->need_chain) {
        s->pc->need_chain = 0; /*(attempt once to complete chain)*/
        if (!mod_mbedtls_construct_crt_chain(s->ssl_pemfile_x509,
                                             s->ssl_ca_file, srv->errh))
            return -1;
    }

    rc = mbedtls_ssl_conf_own_cert(s->ssl_ctx,
                                   s->ssl_pemfile_x509, s->ssl_pemfile_pkey);
    if (0 != rc) {
        elogf(srv->errh, __FILE__, __LINE__, rc,
              "PEM cert and private key did not verify (%s) (%s)",
              s->ssl_pemfile->ptr, s->ssl_privkey->ptr);
        return -1;
    }

  #ifdef MBEDTLS_SSL_ALPN
    /* https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#alpn-protocol-ids */
    static const char *alpn_protos_http_acme[] = {
      "http/1.1"
     ,"http/1.0"
     ,"acme-tls/1"
     ,NULL
    };
    static const char *alpn_protos_http[] = {
      "http/1.1"
     ,"http/1.0"
     ,NULL
    };
    const char **alpn_protos = (!buffer_string_is_empty(s->ssl_acme_tls_1))
      ? alpn_protos_http_acme
      : alpn_protos_http;
    rc = mbedtls_ssl_conf_alpn_protocols(s->ssl_ctx, alpn_protos);
    if (0 != rc) {
        elog(srv->errh, __FILE__, __LINE__, rc, "error setting ALPN protocols");
        return -1;
    }
  #endif

    if (!s->ssl_use_sslv3 && !s->ssl_use_sslv2)
        mod_mbedtls_ssl_conf_proto(srv, s, NULL, 0); /* min */

    if (s->ssl_conf_cmd && s->ssl_conf_cmd->used) {
        if (0 != mod_mbedtls_ssl_conf_cmd(srv, s)) return -1;
    }

    /* server preference is used (default) unless mbedtls is built with
     * MBEDTLS_SSL_SRV_RESPECT_CLIENT_PREFERENCE defined (not default) */
  #ifndef MBEDTLS_SSL_SRV_RESPECT_CLIENT_PREFERENCE
    if (!s->ssl_honor_cipher_order)
        log_error(srv->errh, __FILE__, __LINE__,
          "MTLS: "
          "ignoring ssl.honor-cipher-order; mbedtls uses server preference "
          "unless mbedtls built MBEDTLS_SSL_SRV_RESPECT_CLIENT_PREFERENCE");
  #else
    if (s->ssl_honor_cipher_order)
        log_error(srv->errh, __FILE__, __LINE__,
          "MTLS: "
          "ignoring ssl.honor-cipher-order; mbedtls uses client preference "
          "since mbedtls built MBEDTLS_SSL_SRV_RESPECT_CLIENT_PREFERENCE");
  #endif

  #if defined(MBEDTLS_SSL_SESSION_TICKETS)
    if (s->ssl_session_ticket && !p->ticket_ctx.ticket_lifetime) { /*init once*/
        rc = mbedtls_ssl_ticket_setup(&p->ticket_ctx, mbedtls_ctr_drbg_random,
                                      &p->ctr_drbg, MBEDTLS_CIPHER_AES_256_GCM,
                                      43200); /* ticket timeout: 12 hours */
        if (0 != rc) {
            elog(srv->errh, __FILE__,__LINE__, rc,
                 "mbedtls_ssl_ticket_setup()");
            return -1;
        }
    }

   #if defined(MBEDTLS_SSL_TICKET_C)
    if (s->ssl_session_ticket)
        mbedtls_ssl_conf_session_tickets_cb(s->ssl_ctx,
                                            mbedtls_ssl_ticket_write,
                                            mbedtls_ssl_ticket_parse,
                                            &p->ticket_ctx);
   #endif
  #endif /* MBEDTLS_SSL_SESSION_TICKETS */

    return 0;
}


static int
mod_mbedtls_set_defaults_sockets(server *srv, plugin_data *p)
{
    static const config_plugin_keys_t cpk[] = {
      { CONST_STR_LEN("ssl.engine"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.cipher-list"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.honor-cipher-order"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.dh-file"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.ec-curve"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.openssl.ssl-conf-cmd"),
        T_CONFIG_ARRAY_KVSTRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.pemfile"), /* included to process global scope */
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.empty-fragments"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.use-sslv2"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.use-sslv3"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ NULL, 0,
        T_CONFIG_UNSET,
        T_CONFIG_SCOPE_UNSET }
    };
    static const buffer default_ssl_cipher_list = { CONST_STR_LEN("HIGH"), 0 };

    p->ssl_ctxs = calloc(srv->config_context->used, sizeof(plugin_ssl_ctx));
    force_assert(p->ssl_ctxs);

    int rc = HANDLER_GO_ON;
    plugin_data_base srvplug;
    memset(&srvplug, 0, sizeof(srvplug));
    plugin_data_base * const ps = &srvplug;
    if (!config_plugin_values_init(srv, ps, cpk, "mod_mbedtls"))
        return HANDLER_ERROR;

    plugin_config_socket defaults;
    memset(&defaults, 0, sizeof(defaults));
  #ifndef MBEDTLS_SSL_SRV_RESPECT_CLIENT_PREFERENCE
    defaults.ssl_honor_cipher_order = 1;
  #endif
    defaults.ssl_session_ticket     = 0; /* disabled by default */
    defaults.ssl_cipher_list = &default_ssl_cipher_list;

    /* process and validate config directives for global and $SERVER["socket"]
     * (init i to 0 if global context; to 1 to skip empty global context) */
    for (int i = !ps->cvlist[0].v.u2[1]; i < ps->nconfig; ++i) {
        config_cond_info cfginfo;
        config_get_config_cond_info(&cfginfo, (uint32_t)ps->cvlist[i].k_id);
        int is_socket_scope = (0 == i || cfginfo.comp == COMP_SERVER_SOCKET);
        int count_not_engine = 0;

        plugin_config_socket conf;
        memcpy(&conf, &defaults, sizeof(conf));

        /*(preserve prior behavior; not inherited)*/
        /*(forcing inheritance might break existing configs where SSL is enabled
         * by default in the global scope, but not $SERVER["socket"]=="*:80") */
        conf.ssl_enabled = 0;

        config_plugin_value_t *cpv = ps->cvlist + ps->cvlist[i].v.u2[0];
        for (; -1 != cpv->k_id; ++cpv) {
            /* ignore ssl.pemfile (k_id=10); included to process global scope */
            if (!is_socket_scope && cpv->k_id != 10) {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: %s is valid only in global scope or "
                  "$SERVER[\"socket\"] condition", cpk[cpv->k_id].k);
                continue;
            }
            ++count_not_engine;
            switch (cpv->k_id) {
              case 0: /* ssl.engine */
                conf.ssl_enabled = (0 != cpv->v.u);
                --count_not_engine;
                break;
              case 1: /* ssl.cipher-list */
                conf.ssl_cipher_list = cpv->v.b;
                break;
              case 2: /* ssl.honor-cipher-order */
                conf.ssl_honor_cipher_order = (0 != cpv->v.u);
                break;
              case 3: /* ssl.dh-file */
                conf.ssl_dh_file = cpv->v.b;
                break;
              case 4: /* ssl.ec-curve */
                conf.ssl_ec_curve = cpv->v.b;
                break;
              case 5: /* ssl.openssl.ssl-conf-cmd */
                *(const array **)&conf.ssl_conf_cmd = cpv->v.a;
                break;
              case 6: /* ssl.pemfile */
                /* ignore here; included to process global scope when
                 * ssl.pemfile is set, but ssl.engine is not "enable" */
                break;
              case 7: /* ssl.empty-fragments */
                conf.ssl_empty_fragments = (0 != cpv->v.u);
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: ignoring ssl.empty-fragments; openssl-specific "
                  "counter-measure against a SSL 3.0/TLS 1.0 protocol "
                  "vulnerability affecting CBC ciphers, which cannot be handled"
                  " by some broken (Microsoft) SSL implementations.");
                break;
              case 8: /* ssl.use-sslv2 */
                conf.ssl_use_sslv2 = (0 != cpv->v.u);
                log_error(srv->errh, __FILE__, __LINE__, "MTLS: "
                  "ssl.use-sslv2 is deprecated and will soon be removed.  "
                  "Many modern TLS libraries no longer support SSLv2.");
                break;
              case 9: /* ssl.use-sslv3 */
                conf.ssl_use_sslv3 = (0 != cpv->v.u);
                log_error(srv->errh, __FILE__, __LINE__, "MTLS: "
                  "ssl.use-sslv3 is deprecated and will soon be removed.  "
                  "Many modern TLS libraries no longer support SSLv3.  "
                  "If needed, use: "
                  "ssl.openssl.ssl-conf-cmd = (\"MinProtocol\" => \"SSLv3\")");
                break;
              default:/* should not happen */
                break;
            }
        }
        if (HANDLER_GO_ON != rc) break;
        if (0 == i) memcpy(&defaults, &conf, sizeof(conf));

        if (0 != i && !conf.ssl_enabled) continue;

        /* fill plugin_config_socket with global context then $SERVER["socket"]
         * only for directives directly in current $SERVER["socket"] condition*/

        /*conf.ssl_pemfile_pkey       = p->defaults.ssl_pemfile_pkey;*/
        /*conf.ssl_pemfile_x509       = p->defaults.ssl_pemfile_x509;*/
        conf.ssl_verifyclient         = p->defaults.ssl_verifyclient;
        conf.ssl_verifyclient_enforce = p->defaults.ssl_verifyclient_enforce;
        conf.ssl_verifyclient_depth   = p->defaults.ssl_verifyclient_depth;
        conf.ssl_acme_tls_1           = p->defaults.ssl_acme_tls_1;

        int sidx = ps->cvlist[i].k_id;
        for (int j = !p->cvlist[0].v.u2[1]; j < p->nconfig; ++j) {
            if (p->cvlist[j].k_id != sidx) continue;
            /*if (0 == sidx) break;*//*(repeat to get ssl_pemfile,ssl_privkey)*/
            cpv = p->cvlist + p->cvlist[j].v.u2[0];
            for (; -1 != cpv->k_id; ++cpv) {
                ++count_not_engine;
                switch (cpv->k_id) {
                  case 0: /* ssl.pemfile */
                    if (cpv->vtype == T_CONFIG_LOCAL) {
                        plugin_cert *pc = cpv->v.v;
                        conf.pc               = pc;
                        conf.ssl_pemfile_pkey = &pc->ssl_pemfile_pkey;
                        conf.ssl_pemfile_x509 = &pc->ssl_pemfile_x509;
                        conf.ssl_pemfile      = pc->ssl_pemfile;
                        conf.ssl_privkey      = pc->ssl_privkey;
                    }
                    break;
                  case 2: /* ssl.ca-file */
                    if (cpv->vtype == T_CONFIG_LOCAL)
                        conf.ssl_ca_file = cpv->v.v;
                    break;
                  case 7: /* ssl.verifyclient.activate */
                    conf.ssl_verifyclient = (0 != cpv->v.u);
                    break;
                  case 8: /* ssl.verifyclient.enforce */
                    conf.ssl_verifyclient_enforce = (0 != cpv->v.u);
                    break;
                  case 9: /* ssl.verifyclient.depth */
                    conf.ssl_verifyclient_depth = (unsigned char)cpv->v.shrt;
                    break;
                  case 13:/* ssl.acme-tls-1 */
                    conf.ssl_acme_tls_1 = cpv->v.b;
                    break;
                  default:
                    break;
                }
            }
            break;
        }

        if (NULL == conf.ssl_pemfile_x509) {
            if (0 == i && !conf.ssl_enabled) continue;
            if (0 != i) {
                /* inherit ssl settings from global scope
                 * (if only ssl.engine = "enable" and no other ssl.* settings)
                 * (This is for convenience when defining both IPv4 and IPv6
                 *  and desiring to inherit the ssl config from global context
                 *  without having to duplicate the directives)*/
                if (count_not_engine) {
                    log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: ssl.pemfile has to be set in same "
                      "$SERVER[\"socket\"] scope as other ssl.* directives, "
                      "unless only ssl.engine is set, inheriting ssl.* from "
                      "global scope");
                    rc = HANDLER_ERROR;
                    continue;
                }
                plugin_ssl_ctx * const s = p->ssl_ctxs + sidx;
                *s = *p->ssl_ctxs;/*(copy struct of ssl_ctx from global scope)*/
                continue;
            }
            /* PEM file is required */
            log_error(srv->errh, __FILE__, __LINE__,
              "MTLS: ssl.pemfile has to be set when ssl.engine = \"enable\"");
            rc = HANDLER_ERROR;
            continue;
        }

        /* (initialize once if module enabled) */
        if (!mod_mbedtls_init_once_mbedtls(srv)) {
            rc = HANDLER_ERROR;
            break;
        }

        /* configure ssl_ctx for socket */

        /*conf.ssl_ctx = NULL;*//*(filled by network_init_ssl() even on error)*/
        if (0 == network_init_ssl(srv, &conf, p)) {
            plugin_ssl_ctx * const s = p->ssl_ctxs + sidx;
            s->ssl_ctx            = conf.ssl_ctx;
            s->ciphersuites       = conf.ciphersuites;
            s->curves             = conf.curves;
        }
        else {
            mbedtls_ssl_config_free(conf.ssl_ctx);
            free(conf.ciphersuites);
            free(conf.curves);
            rc = HANDLER_ERROR;
        }
    }

    free(srvplug.cvlist);
    return rc;
}


SETDEFAULTS_FUNC(mod_mbedtls_set_defaults)
{
    static const config_plugin_keys_t cpk[] = {
      { CONST_STR_LEN("ssl.pemfile"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.privkey"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.ca-file"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.ca-dn-file"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.ca-crl-file"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.read-ahead"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.disable-client-renegotiation"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.verifyclient.activate"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.verifyclient.enforce"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.verifyclient.depth"),
        T_CONFIG_SHORT,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.verifyclient.username"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.verifyclient.exportcert"),
        T_CONFIG_BOOL,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("ssl.acme-tls-1"),
        T_CONFIG_STRING,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ CONST_STR_LEN("debug.log-ssl-noise"),
        T_CONFIG_SHORT,
        T_CONFIG_SCOPE_CONNECTION }
     ,{ NULL, 0,
        T_CONFIG_UNSET,
        T_CONFIG_SCOPE_UNSET }
    };

    plugin_data * const p = p_d;
    p->srv = srv;
    if (!config_plugin_values_init(srv, p, cpk, "mod_mbedtls"))
        return HANDLER_ERROR;

    /* process and validate config directives
     * (init i to 0 if global context; to 1 to skip empty global context) */
    for (int i = !p->cvlist[0].v.u2[1]; i < p->nconfig; ++i) {
        config_plugin_value_t *cpv = p->cvlist + p->cvlist[i].v.u2[0];
        config_plugin_value_t *pemfile = NULL;
        config_plugin_value_t *privkey = NULL;
        for (; -1 != cpv->k_id; ++cpv) {
            switch (cpv->k_id) {
              case 0: /* ssl.pemfile */
                if (!buffer_string_is_empty(cpv->v.b)) pemfile = cpv;
                break;
              case 1: /* ssl.privkey */
                if (!buffer_string_is_empty(cpv->v.b)) privkey = cpv;
                break;
              case 2: /* ssl.ca-file */
              case 3: /* ssl.ca-dn-file */
               #if 0 /* defer; not necessary for pemfile parsing */
                if (!mod_mbedtls_init_once_mbedtls(srv)) return HANDLER_ERROR;
               #endif
                if (!buffer_string_is_empty(cpv->v.b)) {
                    mbedtls_x509_crt *cacert = calloc(1, sizeof(*cacert));
                    force_assert(cacert);
                    mbedtls_x509_crt_init(cacert);
                    int rc = mbedtls_x509_crt_parse_file(cacert, cpv->v.b->ptr);
                    if (0 == rc) {
                        cpv->vtype = T_CONFIG_LOCAL;
                        cpv->v.v = cacert;
                    }
                    else {
                        elogf(srv->errh, __FILE__, __LINE__, rc,
                              "%s = %s", cpk[cpv->k_id].k, cpv->v.b->ptr);
                        mbedtls_x509_crt_free(cacert);
                        free(cacert);
                        return HANDLER_ERROR;
                    }
                }
                break;
              case 4: /* ssl.ca-crl-file */
                if (!buffer_string_is_empty(cpv->v.b)) {
                    mbedtls_x509_crl *crl = malloc(sizeof(*crl));
                    force_assert(crl);
                    mbedtls_x509_crl_init(crl);
                    int rc = mbedtls_x509_crl_parse_file(crl, cpv->v.b->ptr);
                    if (0 == rc) {
                        cpv->vtype = T_CONFIG_LOCAL;
                        cpv->v.v = crl;
                    }
                    else {
                        elogf(srv->errh, __FILE__, __LINE__, rc,
                              "CRL file read failed (%s)", cpv->v.b->ptr);
                        free(crl);
                        return HANDLER_ERROR;
                    }
                }
                break;
              case 5: /* ssl.read-ahead */
              case 6: /* ssl.disable-client-renegotiation */
              case 7: /* ssl.verifyclient.activate */
              case 8: /* ssl.verifyclient.enforce */
                break;
              case 9: /* ssl.verifyclient.depth */
                if (cpv->v.shrt > 255) {
                    log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: %s is absurdly large (%hu); limiting to 255",
                      cpk[cpv->k_id].k, cpv->v.shrt);
                    cpv->v.shrt = 255;
                }
                break;
              case 10:/* ssl.verifyclient.username */
              case 11:/* ssl.verifyclient.exportcert */
              case 12:/* ssl.acme-tls-1 */
              case 13:/* debug.log-ssl-noise */
                break;
              default:/* should not happen */
                break;
            }
        }

        if (pemfile) {
            if (NULL == privkey) privkey = pemfile;
            pemfile->v.v =
              network_mbedtls_load_pemfile(srv, pemfile->v.b, privkey->v.b);
            if (pemfile->v.v)
                pemfile->vtype = T_CONFIG_LOCAL;
            else
                return HANDLER_ERROR;
        }
    }

    p->defaults.ssl_verifyclient = 0;
    p->defaults.ssl_verifyclient_enforce = 1;
    p->defaults.ssl_verifyclient_depth = 9;
    p->defaults.ssl_verifyclient_export_cert = 0;
    p->defaults.ssl_disable_client_renegotiation = 1;
    p->defaults.ssl_read_ahead = 0;

    /* initialize p->defaults from global config context */
    if (p->nconfig > 0 && p->cvlist->v.u2[1]) {
        const config_plugin_value_t *cpv = p->cvlist + p->cvlist->v.u2[0];
        if (-1 != cpv->k_id)
            mod_mbedtls_merge_config(&p->defaults, cpv);
    }

  #ifndef MBEDTLS_ERROR_C
    log_error(srv->errh, __FILE__, __LINE__,
              "MTLS: No error strings available. "
              "Compile mbedtls with MBEDTLS_ERROR_C to enable.");
  #endif

    return mod_mbedtls_set_defaults_sockets(srv, p);
}


static int
load_next_chunk (request_st * const r, chunkqueue * const cq, off_t max_bytes,
                 const char ** const data, size_t * const data_len)
{
    chunk *c = cq->first;

    /* local_send_buffer is a static buffer of size (LOCAL_SEND_BUFSIZE)
     *
     * buffer is allocated once, is NOT realloced (note: not thread-safe)
     * */

    force_assert(NULL != c);

    switch (c->type) {
    case MEM_CHUNK:
        *data = NULL;
        *data_len = 0;
        do {
            size_t have;

            force_assert(c->offset >= 0
                         && c->offset <= (off_t)buffer_string_length(c->mem));

            have = buffer_string_length(c->mem) - c->offset;

            /* copy small mem chunks into single large buffer
             * before mbedtls_ssl_write() to reduce number times
             * write() called underneath mbedtls_ssl_write() and
             * potentially reduce number of packets generated if TCP_NODELAY */
            if (*data_len) {
                size_t space = LOCAL_SEND_BUFSIZE - *data_len;
                if (have > space)
                    have = space;
                if (have > (size_t)max_bytes - *data_len)
                    have = (size_t)max_bytes - *data_len;
                if (*data != local_send_buffer) {
                    memcpy(local_send_buffer, *data, *data_len);
                    *data = local_send_buffer;
                }
                memcpy(local_send_buffer+*data_len,c->mem->ptr+c->offset,have);
                *data_len += have;
                continue;
            }

            if ((off_t) have > max_bytes) have = max_bytes;

            *data = c->mem->ptr + c->offset;
            *data_len = have;
        } while ((c = c->next) && c->type == MEM_CHUNK
                 && *data_len < LOCAL_SEND_BUFSIZE
                 && (off_t) *data_len < max_bytes);
        return 0;

    case FILE_CHUNK:
        if (0 != chunkqueue_open_file_chunk(cq, r->conf.errh)) return -1;

        {
            off_t offset, toSend;

            force_assert(c->offset >= 0 && c->offset <= c->file.length);
            offset = c->file.start + c->offset;
            toSend = c->file.length - c->offset;

            if (toSend > LOCAL_SEND_BUFSIZE) toSend = LOCAL_SEND_BUFSIZE;
            if (toSend > max_bytes) toSend = max_bytes;

            if (-1 == lseek(c->file.fd, offset, SEEK_SET)) {
                log_perror(r->conf.errh, __FILE__, __LINE__, "lseek");
                return -1;
            }
            if (-1 == (toSend = read(c->file.fd, local_send_buffer, toSend))) {
                log_perror(r->conf.errh, __FILE__, __LINE__, "read");
                return -1;
            }

            *data = local_send_buffer;
            *data_len = toSend;
        }
        return 0;
    }

    return -1;
}


__attribute_cold__
static int
mod_mbedtls_ssl_write_err(connection *con, handler_ctx *hctx, int wr, size_t wr_len)
{
    switch (wr) {
      case MBEDTLS_ERR_SSL_WANT_READ:
        con->is_readable = -1;
        break; /* try again later */
      case MBEDTLS_ERR_SSL_WANT_WRITE:
        con->is_writable = -1;
        break; /* try again later */
      case MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS:
      case MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS:
        break; /* try again later */
      case MBEDTLS_ERR_NET_CONN_RESET:
        if (hctx->conf.ssl_log_noise)
            elog(hctx->r->conf.errh, __FILE__, __LINE__, wr,
                 "peer closed connection");
        return -1;
      default:
        elog(hctx->r->conf.errh, __FILE__, __LINE__, wr, __func__);
        return -1;
    }

    if (0 != hctx->ssl.out_left)  /* partial write; save attempted wr_len */
        hctx->pending_write = wr_len;

    return 0; /* try again later */
}


static int
mod_mbedtls_close_notify(handler_ctx *hctx);


static int
connection_write_cq_ssl (connection *con, chunkqueue *cq, off_t max_bytes)
{
    request_st * const r = &con->request;
    handler_ctx *hctx = r->plugin_ctx[plugin_data_singleton->id];
    mbedtls_ssl_context * const ssl = &hctx->ssl;

    if (hctx->pending_write) {
        int wr = (int)hctx->pending_write;
        if (0 != ssl->out_left) {
            /*(would prefer mbedtls_ssl_flush_output() from ssl_internal.h)*/
            size_t data_len = hctx->pending_write;
            wr = mbedtls_ssl_write(ssl, NULL, data_len);
            if (wr <= 0)
                return mod_mbedtls_ssl_write_err(con, hctx, wr, data_len);
            max_bytes -= wr;
        }
        hctx->pending_write = 0;
        chunkqueue_mark_written(cq, wr);
    }

    if (0 != hctx->close_notify) return mod_mbedtls_close_notify(hctx);

    chunkqueue_remove_finished_chunks(cq);

    const int lim = mbedtls_ssl_get_max_out_record_payload(ssl);
    if (lim < 0) return mod_mbedtls_ssl_write_err(con, hctx, lim, 0);

    while (max_bytes > 0 && NULL != cq->first) {
        const char *data;
        size_t data_len;
        int wr;

        if (0 != load_next_chunk(r, cq, max_bytes, &data, &data_len)) return -1;

        /* mbedtls_ssl_write() copies the data, up to max record size, but if
         * (temporarily) unable to write the entire record, it is documented
         * that the caller must call mbedtls_ssl_write() again, later, with the
         * same arguments.  This appears to be because mbedtls_ssl_context does
         * not keep track of the original size of the caller data that
         * mbedtls_ssl_write() attempted to write (and may have transformed to
         * a different size).  The func may return MBEDTLS_ERR_SSL_WANT_READ or
         * MBEDTLS_ERR_SSL_WANT_WRITE to indicate that the caller should wait
         * for the fd to be readable/writable before calling the func again,
         * which is why those (temporary) errors are returned instead of telling
         * the caller that the data was successfully copied.  When the record is
         * written successfully, the return value is supposed to indicate the
         * number of (originally submitted) bytes written, but since that value
         * is unknown (not saved), the caller's len parameter is reflected back,
         * which is why the caller must call the func again with the same args.
         * Additionally, to be accurate, the size must fit into a record which
         * is why we restrict ourselves to sending max out record payload each
         * iteration.
         */

        int wr_total = 0;
        do {
            size_t wr_len = (data_len > (size_t)lim) ? (size_t)lim : data_len;
            wr = mbedtls_ssl_write(ssl, (const unsigned char *)data, wr_len);
            if (wr <= 0) {
                if (wr_total) chunkqueue_mark_written(cq, wr_total);
                return mod_mbedtls_ssl_write_err(con, hctx, wr, wr_len);
            }
            wr_total += wr;
            data += wr;
        } while ((data_len -= wr));
        chunkqueue_mark_written(cq, wr_total);
        max_bytes -= wr_total;
    }

    return 0;
}


static int
mod_mbedtls_ssl_handshake (handler_ctx *hctx)
{
    int rc = 0;

    /* overwrite callback with hctx each time we enter here, before handshake
     * (Some callbacks are on mbedtls_ssl_config, not mbedtls_ssl_context)
     * (Not thread-safe if config (mbedtls_ssl_config *ssl_ctx) is shared)
     * (XXX: there is probably a better way to do this...) */
    /* (alternative: save ssl_ctx in hctx in mod_mbedtls_handle_con_accept()) */
    mbedtls_ssl_config *ssl_ctx;
    *(const mbedtls_ssl_config **)&ssl_ctx = hctx->ssl.conf;
  #ifdef MBEDTLS_SSL_SERVER_NAME_INDICATION
    mbedtls_ssl_conf_sni(ssl_ctx, mod_mbedtls_SNI, hctx);
  #endif

    if (hctx->ssl.state < MBEDTLS_SSL_SERVER_HELLO) {
        while (hctx->ssl.state != MBEDTLS_SSL_SERVER_HELLO
            && hctx->ssl.state != MBEDTLS_SSL_HANDSHAKE_OVER) {
            rc = mbedtls_ssl_handshake_step(&hctx->ssl);
            if (0 != rc) break;
        }
        if (0 == rc && hctx->ssl.state == MBEDTLS_SSL_SERVER_HELLO) {
          #ifdef MBEDTLS_SSL_ALPN
            if (!buffer_string_is_empty(hctx->conf.ssl_acme_tls_1)) {
                const char *alpn = mbedtls_ssl_get_alpn_protocol(&hctx->ssl);
                if (NULL != alpn)
                    rc = mod_mbedtls_alpn_select_cb(hctx, alpn);
            }
          #endif
        }
    }

    /* overwrite callback with hctx each time we enter here, before handshake
     * (Some callbacks are on mbedtls_ssl_config, not mbedtls_ssl_context)
     * (Not thread-safe if config (mbedtls_ssl_config *ssl_ctx) is shared)
     * (XXX: there is probably a better way to do this...) */
    if (0 == rc && hctx->conf.ssl_verifyclient
        && hctx->ssl.state >= MBEDTLS_SSL_SERVER_HELLO  /*(after SNI and ALPN)*/
        && hctx->ssl.state <= MBEDTLS_SSL_SERVER_HELLO_DONE
        && hctx->alpn != MOD_MBEDTLS_ALPN_ACME_TLS_1) { /*(not "acme-tls/1")*/
        int mode = (hctx->conf.ssl_verifyclient_enforce)
          ? MBEDTLS_SSL_VERIFY_REQUIRED
          : MBEDTLS_SSL_VERIFY_OPTIONAL;
        mbedtls_ssl_set_hs_authmode(&hctx->ssl, mode);
        while (hctx->ssl.state != MBEDTLS_SSL_CERTIFICATE_REQUEST
            && hctx->ssl.state != MBEDTLS_SSL_HANDSHAKE_OVER) {
            rc = mbedtls_ssl_handshake_step(&hctx->ssl);
            if (0 != rc) break;
        }
        if (0 == rc && hctx->ssl.state == MBEDTLS_SSL_CERTIFICATE_REQUEST) {
            rc = mod_mbedtls_conf_verify(hctx, ssl_ctx);
            if (0 == rc)
                rc = mbedtls_ssl_handshake_step(&hctx->ssl);
            /* reconfigure CA trust chain after sending client certificate
             * request (if ssl_ca_dn_file is set), before client certificate
             * verification (MBEDTLS_SSL_CERTIFICATE_VERIFY) */
            if (0 == rc && hctx->conf.ssl_ca_dn_file
                && hctx->ssl.state == MBEDTLS_SSL_SERVER_HELLO_DONE) {
                mbedtls_ssl_context * const ssl = &hctx->ssl;
                mbedtls_x509_crt *ca_certs = hctx->conf.ssl_ca_file;
                mbedtls_x509_crl *ca_crl = hctx->conf.ssl_ca_crl_file;
                mbedtls_ssl_set_hs_ca_chain(ssl, ca_certs, ca_crl);
            }
        }
    }

    if (0 == rc && hctx->ssl.state != MBEDTLS_SSL_HANDSHAKE_OVER) {
        rc = mbedtls_ssl_handshake(&hctx->ssl);
    }

    switch (rc) {
      case 0:
        hctx->handshake_done = 1;
       #ifdef MBEDTLS_SSL_ALPN
        if (hctx->alpn == MOD_MBEDTLS_ALPN_ACME_TLS_1) {
            /* Once TLS handshake is complete, return -1 to result in
             * CON_STATE_ERROR so that socket connection is quickly closed */
            return -1;
        }
        hctx->alpn = 0;
       #endif
        return 1; /* continue reading */
      case MBEDTLS_ERR_SSL_WANT_WRITE:
        hctx->con->is_writable = -1;
        __attribute_fallthrough__
      case MBEDTLS_ERR_SSL_WANT_READ:
        hctx->con->is_readable = 0;
        return 0;
      case MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS:
      case MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS:
        return 0;
      case MBEDTLS_ERR_SSL_CLIENT_RECONNECT:
        return -1;
      case MBEDTLS_ERR_NET_CONN_RESET:
      case MBEDTLS_ERR_SSL_CONN_EOF:
        if (!hctx->conf.ssl_log_noise) return -1;
        __attribute_fallthrough__
      default:
        elog(hctx->r->conf.errh, __FILE__, __LINE__, rc, __func__);
        return -1;
    }
}


static int
connection_read_cq_ssl (connection *con, chunkqueue *cq, off_t max_bytes)
{
    request_st * const r = &con->request;
    handler_ctx *hctx = r->plugin_ctx[plugin_data_singleton->id];
    int len;
    char *mem = NULL;
    size_t mem_len = 0;

    UNUSED(max_bytes);

    if (0 != hctx->close_notify) return mod_mbedtls_close_notify(hctx);

    if (!hctx->handshake_done) {
        int rc = mod_mbedtls_ssl_handshake(hctx);
        if (1 != rc) return rc; /* !hctx->handshake_done; not done, or error */
    }

    do {
        len = mbedtls_ssl_get_bytes_avail(&hctx->ssl);
        mem_len = len < 2048 ? 2048 : (size_t)len;
        chunk * const ckpt = cq->last;
        mem = chunkqueue_get_memory(cq, &mem_len);

        len = mbedtls_ssl_read(&hctx->ssl, (unsigned char *)mem, mem_len);
        if (len > 0) {
            chunkqueue_use_memory(cq, ckpt, len);
            con->bytes_read += len;
        } else {
            chunkqueue_use_memory(cq, ckpt, 0);
        }
    } while (len > 0
             && mbedtls_ssl_check_pending(&hctx->ssl));

    if (len < 0) {
        int rc = len;
        switch (rc) {
          case MBEDTLS_ERR_SSL_WANT_WRITE:
            con->is_writable = -1;
            __attribute_fallthrough__
          case MBEDTLS_ERR_SSL_WANT_READ:
            con->is_readable = 0;
            return 0;
          case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
          case MBEDTLS_ERR_SSL_CONN_EOF:
            /* XXX: future: save state to avoid future read after response? */
            con->is_readable = 0;
            r->keep_alive = 0;
            return -2;
          case MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS:
          case MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS:
            return 0;
          case MBEDTLS_ERR_SSL_CLIENT_RECONNECT:
            return -1;
          case MBEDTLS_ERR_NET_CONN_RESET:
            if (!hctx->conf.ssl_log_noise) return -1;
            __attribute_fallthrough__
          default:
            elog(r->conf.errh, __FILE__, __LINE__, rc, "Reading mbedtls");
            return -1;
        }
    } else if (len == 0) {
        con->is_readable = 0;
        /* the other end closed the connection -> KEEP-ALIVE */

        return -2;
    } else {
        return 0;
    }
}


static void
mod_mbedtls_debug_cb(void *ctx, int level,
                     const char *file, int line,
                     const char *str)
{
    if (level < (intptr_t)ctx) /* level */
        log_error(plugin_data_singleton->srv->errh,file,line,"MTLS: %s",str);
}


CONNECTION_FUNC(mod_mbedtls_handle_con_accept)
{
    server_socket *srv_sock = con->srv_socket;
    if (!srv_sock->is_ssl) return HANDLER_GO_ON;

    plugin_data *p = p_d;
    handler_ctx * const hctx = handler_ctx_init();
    request_st * const r = &con->request;
    hctx->r = r;
    hctx->con = con;
    hctx->tmp_buf = con->srv->tmp_buf;
    r->plugin_ctx[p->id] = hctx;

    plugin_ssl_ctx * const s = p->ssl_ctxs + srv_sock->sidx;
    mbedtls_ssl_init(&hctx->ssl);
    int rc = mbedtls_ssl_setup(&hctx->ssl, s->ssl_ctx);
    if (0 == rc) {
        con->network_read = connection_read_cq_ssl;
        con->network_write = connection_write_cq_ssl;
        con->proto_default_port = 443; /* "https" */
        mod_mbedtls_patch_config(r, &hctx->conf);
    }
    else {
        elog(r->conf.errh, __FILE__, __LINE__, rc, "ssl_setup() failed");
        return HANDLER_ERROR;
    }

    mbedtls_ssl_set_bio(&hctx->ssl, (mbedtls_net_context *)&con->fd,
                        mbedtls_net_send, mbedtls_net_recv, NULL);

    /* (mbedtls_ssl_config *) is shared across multiple connections, which may
     * overlap, and so this debug setting is not reset upon connection close.
     * Once enabled, debug hook will remain so for this mbedtls_ssl_config */
    if (hctx->conf.ssl_log_noise)  /* volume level for debug message callback */
        mbedtls_ssl_conf_dbg(s->ssl_ctx, mod_mbedtls_debug_cb,
                             (void *)(intptr_t)hctx->conf.ssl_log_noise);

    /* (mbedtls_ssl_config *) is shared across multiple connections, which may
     * overlap, and so renegotiation setting is not reset upon connection close.
     * Once enabled, renegotiation will remain so for this mbedtls_ssl_config.
     * mbedtls defaults to disable client renegotiation
     *   (MBEDTLS_SSL_RENEGOTIATION_DISABLED)
     * and it is recommended to leave it disabled (lighttpd mbedtls default) */
    if (!hctx->conf.ssl_disable_client_renegotiation)
        mbedtls_ssl_conf_renegotiation(s->ssl_ctx,
                                       MBEDTLS_SSL_RENEGOTIATION_ENABLED);

    return HANDLER_GO_ON;
}


static void
mod_mbedtls_detach(handler_ctx *hctx)
{
    /* step aside from further SSL processing
     * (used after handle_connection_shut_wr hook) */
    /* future: might restore prior network_read and network_write fn ptrs */
    hctx->con->is_ssl_sock = 0;
    /* if called after handle_connection_shut_wr hook, shutdown SHUT_WR */
    if (-1 == hctx->close_notify) shutdown(hctx->con->fd, SHUT_WR);
    hctx->close_notify = 1;
}


CONNECTION_FUNC(mod_mbedtls_handle_con_shut_wr)
{
    request_st * const r = &con->request;
    plugin_data *p = p_d;
    handler_ctx *hctx = r->plugin_ctx[p->id];
    if (NULL == hctx) return HANDLER_GO_ON;

    hctx->close_notify = -2;
    if (hctx->handshake_done) {
        mod_mbedtls_close_notify(hctx);
    }
    else {
        mod_mbedtls_detach(hctx);
    }

    return HANDLER_GO_ON;
}


static int
mod_mbedtls_close_notify (handler_ctx *hctx)
{
    if (1 == hctx->close_notify) return -2;

    int rc = mbedtls_ssl_close_notify(&hctx->ssl);
    switch (rc) {
      case 0:
        mod_mbedtls_detach(hctx);
        return -2;
      case MBEDTLS_ERR_SSL_WANT_READ:
      case MBEDTLS_ERR_SSL_WANT_WRITE:
        return 0;
      default:
        elog(hctx->r->conf.errh, __FILE__, __LINE__, rc,
             "mbedtls_ssl_close_notify()");
        mbedtls_ssl_session_reset(&hctx->ssl);
        mod_mbedtls_detach(hctx);
        return -1;
    }
}


CONNECTION_FUNC(mod_mbedtls_handle_con_close)
{
    request_st * const r = &con->request;
    plugin_data *p = p_d;
    handler_ctx *hctx = r->plugin_ctx[p->id];
    if (NULL != hctx) {
        if (1 != hctx->close_notify)
            mod_mbedtls_close_notify(hctx); /*(one final try)*/
        handler_ctx_free(hctx);
        r->plugin_ctx[p->id] = NULL;
    }

    return HANDLER_GO_ON;
}


#if defined(MBEDTLS_PEM_WRITE_C)
__attribute_noinline__
static void
https_add_ssl_client_cert (request_st * const r, const mbedtls_x509_crt * const peer)
{
    #define PEM_BEGIN_CRT "-----BEGIN CERTIFICATE-----\n"
    #define PEM_END_CRT   "-----END CERTIFICATE-----\n"
    unsigned char buf[4096];
    size_t olen;
    if (0 == mbedtls_pem_write_buffer(PEM_BEGIN_CRT, PEM_END_CRT,
                                      peer->raw.p, peer->raw.len,
                                      buf, sizeof(buf), &olen))
        http_header_env_set(r,
                            CONST_STR_LEN("SSL_CLIENT_CERT"),
                            (char *)buf, olen);
}
#endif


static void
https_add_ssl_client_entries (request_st * const r, handler_ctx * const hctx)
{
    /* Note: starting with mbedtls-2.17.0, peer cert is not available here if
     * MBEDTLS_SSL_KEEP_PEER_CERTIFICATE *is not* defined at compile time,
     * though default behavior is to have it defined.  However, since earlier
     * versions do keep the cert, but not set this define, attempt to retrieve
     * the peer cert and check for NULL before using it. */
    const mbedtls_x509_crt *crt = mbedtls_ssl_get_peer_cert(&hctx->ssl);
    buffer * const tb = r->tmp_buf;
    char buf[512];
    int n;

    uint32_t rc = (NULL != crt)
      ? mbedtls_ssl_get_verify_result(&hctx->ssl)
      : 0xFFFFFFFF;
    if (0xFFFFFFFF == rc) { /*(e.g. no cert, or verify result not available)*/
        http_header_env_set(r,
                            CONST_STR_LEN("SSL_CLIENT_VERIFY"),
                            CONST_STR_LEN("NONE"));
        return;
    }
    else if (0 != rc) {
        /* get failure string and translate newline to ':', removing last one */
        n = mbedtls_x509_crt_verify_info(buf, sizeof(buf), "", rc);
        buffer_copy_string_len(tb, CONST_STR_LEN("FAILED:"));
        if (n > 0) {
            for (char *nl = buf; NULL != (nl = strchr(nl, '\n')); ++nl)
                nl[0] = ('\0' == nl[1] ? (--n, '\0') : ':');
            buffer_append_string_len(tb, buf, n);
        }
        http_header_env_set(r,
                            CONST_STR_LEN("SSL_CLIENT_VERIFY"),
                            CONST_BUF_LEN(tb));
        return;
    }
    else {
        http_header_env_set(r,
                            CONST_STR_LEN("SSL_CLIENT_VERIFY"),
                            CONST_STR_LEN("SUCCESS"));
    }

    n = mbedtls_x509_dn_gets(buf, sizeof(buf), &crt->subject);
    if (n > 0 && n < (int)sizeof(buf)) {
        http_header_env_set(r,
                            CONST_STR_LEN("SSL_CLIENT_S_DN"),
                            buf, n);
    }

    /* add components of client Subject DN */
    /* code block is similar to mbedtls_x509_dn_gets() */
    /*(reuse buf; sizeof(buf) > MBEDTLS_X509_MAX_DN_NAME_SIZE, which is 256)*/
    buffer_copy_string_len(tb, CONST_STR_LEN("SSL_CLIENT_S_DN_"));
    const mbedtls_x509_name *name = &crt->subject;
    while (name != NULL) {
        if (!name->oid.p) {
            name = name->next;
            continue;
        }

        const char *short_name = NULL;
        if (0 != mbedtls_oid_get_attr_short_name(&name->oid, &short_name))
            continue;
        buffer_string_set_length(tb, sizeof("SSL_CLIENT_S_DN_")-1);
        buffer_append_string(tb, short_name);

        const mbedtls_x509_name *nm = name;
        n = 0;
        do {
            if (nm != name && n < (int)sizeof(buf)-1)
                buf[n++] = ',';
            for (size_t i = 0; i < nm->val.len && n < (int)sizeof(buf)-1; ++n) {
                unsigned char c = nm->val.p[i];
                buf[n] = (c < 32 || c == 127 || (c > 128 && c < 160)) ? '?' : c;
            }
            buf[n] = '\0';
        } while (nm->next_merged && nm->next && (nm = nm->next));
        if (n == sizeof(buf)-1)
            while (nm->next_merged && nm->next) nm = nm->next;
        name = nm->next;

        http_header_env_set(r,
                            CONST_BUF_LEN(tb),
                            buf, n);
    }

    n = mbedtls_x509_serial_gets(buf, sizeof(buf), &crt->serial);
    if (n > 0 && n < (int)sizeof(buf)) {
        http_header_env_set(r,
                            CONST_STR_LEN("SSL_CLIENT_M_SERIAL"),
                            buf, n);
    }

    if (!buffer_string_is_empty(hctx->conf.ssl_verifyclient_username)) {
        /* pick one of the exported values as "REMOTE_USER", for example
         *   ssl.verifyclient.username = "SSL_CLIENT_S_DN_UID"
         * or
         *   ssl.verifyclient.username = "SSL_CLIENT_S_DN_emailAddress"
         */
        const buffer *varname = hctx->conf.ssl_verifyclient_username;
        const buffer *vb = http_header_env_get(r, CONST_BUF_LEN(varname));
        if (vb) { /* same as http_auth.c:http_auth_setenv() */
            http_header_env_set(r,
                                CONST_STR_LEN("REMOTE_USER"),
                                CONST_BUF_LEN(vb));
            http_header_env_set(r,
                                CONST_STR_LEN("AUTH_TYPE"),
                                CONST_STR_LEN("SSL_CLIENT_VERIFY"));
        }
    }

  #if defined(MBEDTLS_PEM_WRITE_C)
    /* if (NULL != crt) (e.g. not PSK-based ciphersuite) */
    if (hctx->conf.ssl_verifyclient_export_cert && NULL != crt)
        https_add_ssl_client_cert(r, crt);
  #endif
}


static void
http_cgi_ssl_env (request_st * const r, handler_ctx * const hctx)
{
  #if 1
    /* XXX: reaching into ssl_internal.h here for mbedtls_ssl_transform */
    const mbedtls_cipher_info_t *cipher_info =
      hctx->ssl.transform->cipher_ctx_enc.cipher_info;
  #else
    const mbedtls_ssl_ciphersuite_t *ciphersuite_info =
      mbedtls_ssl_ciphersuite_from_id(hctx->ssl.session->ciphersuite);
    const mbedtls_cipher_info_t *cipher_info =
      mbedtls_cipher_info_from_type(ciphersuite_info->cipher);
  #endif
    const char *s;

    s = mbedtls_ssl_get_version(&hctx->ssl);
    http_header_env_set(r, CONST_STR_LEN("SSL_PROTOCOL"), s, strlen(s));

    /*s = ciphersuite_info->name;*/ /*mbedtls_ssl_get_ciphersuite(&hctx->ssl);*/
    s = cipher_info->name;
    http_header_env_set(r, CONST_STR_LEN("SSL_CIPHER"), s, strlen(s));

    if (cipher_info != NULL) {
        /* SSL_CIPHER_ALGKEYSIZE - Number of cipher bits (possible) */
        /* SSL_CIPHER_USEKEYSIZE - Number of cipher bits (actually used) */
        /* XXX: is usekeysize correct? XXX: reaching into ssl_internal.h here */
        int usekeysize = hctx->ssl.transform->cipher_ctx_enc.key_bitlen;
        unsigned int algkeysize = cipher_info->key_bitlen;
        char buf[LI_ITOSTRING_LENGTH];
        http_header_env_set(r, CONST_STR_LEN("SSL_CIPHER_USEKEYSIZE"),
                            buf, li_itostrn(buf, sizeof(buf), usekeysize));
        http_header_env_set(r, CONST_STR_LEN("SSL_CIPHER_ALGKEYSIZE"),
                            buf, li_utostrn(buf, sizeof(buf), algkeysize));
    }
}


REQUEST_FUNC(mod_mbedtls_handle_request_env)
{
    plugin_data *p = p_d;
    handler_ctx *hctx = r->plugin_ctx[p->id];
    if (NULL == hctx) return HANDLER_GO_ON;
    if (hctx->request_env_patched) return HANDLER_GO_ON;
    hctx->request_env_patched = 1;

    http_cgi_ssl_env(r, hctx);
    if (hctx->conf.ssl_verifyclient) {
        https_add_ssl_client_entries(r, hctx);
    }

    return HANDLER_GO_ON;
}


REQUEST_FUNC(mod_mbedtls_handle_uri_raw)
{
    /* mod_mbedtls must be loaded prior to mod_auth
     * if mod_mbedtls is configured to set REMOTE_USER based on client cert */
    /* mod_mbedtls must be loaded after mod_extforward
     * if mod_mbedtls config is based on lighttpd.conf remote IP conditional
     * using remote IP address set by mod_extforward, *unless* PROXY protocol
     * is enabled with extforward.hap-PROXY = "enable", in which case the
     * reverse is true: mod_extforward must be loaded after mod_mbedtls */
    plugin_data *p = p_d;
    handler_ctx *hctx = r->plugin_ctx[p->id];
    if (NULL == hctx) return HANDLER_GO_ON;

    mod_mbedtls_patch_config(r, &hctx->conf);
    if (hctx->conf.ssl_verifyclient) {
        mod_mbedtls_handle_request_env(r, p);
    }

    return HANDLER_GO_ON;
}


REQUEST_FUNC(mod_mbedtls_handle_request_reset)
{
    plugin_data *p = p_d;
    handler_ctx *hctx = r->plugin_ctx[p->id];
    if (NULL == hctx) return HANDLER_GO_ON;

    hctx->request_env_patched = 0;
    return HANDLER_GO_ON;
}


int mod_mbedtls_plugin_init (plugin *p);
int mod_mbedtls_plugin_init (plugin *p)
{
    p->version      = LIGHTTPD_VERSION_ID;
    p->name         = "mbedtls";
    p->init         = mod_mbedtls_init;
    p->cleanup      = mod_mbedtls_free;
    p->priv_defaults= mod_mbedtls_set_defaults;

    p->handle_connection_accept  = mod_mbedtls_handle_con_accept;
    p->handle_connection_shut_wr = mod_mbedtls_handle_con_shut_wr;
    p->handle_connection_close   = mod_mbedtls_handle_con_close;
    p->handle_uri_raw            = mod_mbedtls_handle_uri_raw;
    p->handle_request_env        = mod_mbedtls_handle_request_env;
    p->connection_reset          = mod_mbedtls_handle_request_reset;

    return 0;
}


/* cipher suites (taken from mbedtls/ssl_ciphersuites.[ch]) */

static const int suite_CHACHAPOLY_ephemeral[] = {
    /* Chacha-Poly ephemeral suites */
    MBEDTLS_TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256
};

static const int suite_AES_256_ephemeral[] = {
    /* All AES-256 ephemeral suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CCM_8
};

static const int suite_CAMELLIA_256_ephemeral[] = {
    /* All CAMELLIA-256 ephemeral suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
};

static const int suite_ARIA_256_ephemeral[] = {
    /* All ARIA-256 ephemeral suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_256_CBC_SHA384
};

static const int suite_AES_128_ephemeral[] = {
    /* All AES-128 ephemeral suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CCM_8
};

static const int suite_CAMELLIA_128_ephemeral[] = {
    /* All CAMELLIA-128 ephemeral suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
};

static const int suite_ARIA_128_ephemeral[] = {
    /* All ARIA-128 ephemeral suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_128_CBC_SHA256
};

static const int suite_PSK_ephemeral[] = {
    /* The PSK ephemeral suites */
    MBEDTLS_TLS_ECDHE_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CCM,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_PSK_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_256_CBC_SHA384,

    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CCM,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_128_CBC_SHA256
};

#if 0
static const int suite_ECJPAKE[] = {
    /* The ECJPAKE suite */
    MBEDTLS_TLS_ECJPAKE_WITH_AES_128_CCM_8
};
#endif

static const int suite_AES_256[] = {
    /* All AES-256 suites */
    MBEDTLS_TLS_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_RSA_WITH_AES_256_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_AES_256_CCM_8
};

static const int suite_CAMELLIA_256[] = {
    /* All CAMELLIA-256 suites */
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_256_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_256_CBC_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_CAMELLIA_256_CBC_SHA384
};

static const int suite_ARIA_256[] = {
    /* All ARIA-256 suites */
    MBEDTLS_TLS_ECDH_ECDSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_WITH_ARIA_256_CBC_SHA384
};

static const int suite_AES_128[] = {
    /* All AES-128 suites */
    MBEDTLS_TLS_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_AES_128_CCM_8
};

static const int suite_CAMELLIA_128[] = {
    /* All CAMELLIA-128 suites */
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_128_CBC_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_CAMELLIA_128_CBC_SHA256
};

static const int suite_ARIA_128[] = {
    /* All ARIA-128 suites */
    MBEDTLS_TLS_ECDH_ECDSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_ARIA_128_CBC_SHA256
};

static const int suite_RSA_PSK[] = {
    /* The RSA PSK suites */
    MBEDTLS_TLS_RSA_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_256_CBC_SHA384,

    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_128_CBC_SHA256
};

static const int suite_PSK[] = {
    /* The PSK suites */
    MBEDTLS_TLS_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_256_CCM,
    MBEDTLS_TLS_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_PSK_WITH_ARIA_256_CBC_SHA384,

    MBEDTLS_TLS_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_128_CCM,
    MBEDTLS_TLS_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_PSK_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_PSK_WITH_ARIA_128_CBC_SHA256
};

static const int suite_3DES[] = {
    /* 3DES suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDHE_PSK_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_PSK_WITH_3DES_EDE_CBC_SHA
};

static const int suite_RC4[] = {
    /* RC4 suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_ECDHE_PSK_WITH_RC4_128_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_RC4_128_SHA,
    MBEDTLS_TLS_RSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_RSA_WITH_RC4_128_MD5,
    MBEDTLS_TLS_ECDH_RSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_RC4_128_SHA,
    MBEDTLS_TLS_PSK_WITH_RC4_128_SHA
};

static const int suite_weak[] = {
    /* Weak suites */
    MBEDTLS_TLS_DHE_RSA_WITH_DES_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_DES_CBC_SHA
};

static const int suite_null[] = {
    /* NULL suites */
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_NULL_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_NULL_SHA,
    MBEDTLS_TLS_ECDHE_PSK_WITH_NULL_SHA384,
    MBEDTLS_TLS_ECDHE_PSK_WITH_NULL_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_NULL_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_NULL_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_NULL_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_NULL_SHA,

    MBEDTLS_TLS_RSA_WITH_NULL_SHA256,
    MBEDTLS_TLS_RSA_WITH_NULL_SHA,
    MBEDTLS_TLS_RSA_WITH_NULL_MD5,
    MBEDTLS_TLS_ECDH_RSA_WITH_NULL_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_NULL_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_NULL_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_NULL_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_NULL_SHA,
    MBEDTLS_TLS_PSK_WITH_NULL_SHA384,
    MBEDTLS_TLS_PSK_WITH_NULL_SHA256,
    MBEDTLS_TLS_PSK_WITH_NULL_SHA
};

/* TLSv1.2 cipher list (supported in mbedtls)
 * marked with minimum version MBEDTLS_SSL_MINOR_VERSION_3 in
 *   ciphersuite_definitions[] and then sorted by ciphersuite_preference[]
 *   from mbedtls library/ssl_ciphersuites.c */
static const int suite_TLSv12[] = {
    MBEDTLS_TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CCM,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_PSK_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CCM,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECJPAKE_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_RSA_WITH_AES_256_CBC_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_256_CBC_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_128_CBC_SHA256,
    MBEDTLS_TLS_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_256_CCM,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_256_GCM_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_PSK_WITH_ARIA_256_CBC_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_128_CCM,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_128_GCM_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_PSK_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_PSK_WITH_ARIA_128_CBC_SHA256
};

/* TLSv1.0 cipher list (supported in mbedtls)
 * marked with minimum version MBEDTLS_SSL_MINOR_VERSION_1 in
 *   ciphersuite_definitions[] and then sorted by ciphersuite_preference[]
 *   from mbedtls library/ssl_ciphersuites.c */
/* XXX: intentionally not including overlapping eNULL ciphers */
static const int suite_TLSv10[] = {
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDH_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDHE_PSK_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_ECDHE_PSK_WITH_RC4_128_SHA,
    MBEDTLS_TLS_ECDH_RSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_ECDH_ECDSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_RC4_128_SHA
};

/* SSLv3 cipher list (supported in mbedtls)
 * marked with minimum version MBEDTLS_SSL_MINOR_VERSION_0 in
 *   ciphersuite_definitions[] and then sorted by ciphersuite_preference[]
 *   from mbedtls library/ssl_ciphersuites.c */
/* XXX: intentionally not including overlapping eNULL ciphers */
static const int suite_SSLv3[] = {
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_256_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_128_CBC_SHA,
    MBEDTLS_TLS_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_PSK_WITH_3DES_EDE_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_RC4_128_SHA,
    MBEDTLS_TLS_RSA_WITH_RC4_128_SHA,
    MBEDTLS_TLS_RSA_WITH_RC4_128_MD5,
    MBEDTLS_TLS_PSK_WITH_RC4_128_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_DES_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_DES_CBC_SHA
};

/* HIGH cipher list (mapped from openssl list to mbedtls) */
static const int suite_HIGH[] = {
    MBEDTLS_TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_DHE_RSA_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA,
    MBEDTLS_TLS_ECDHE_ECDSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CCM,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_ECDHE_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CCM,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_DHE_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_ECDHE_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_DHE_PSK_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_DHE_PSK_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_WITH_AES_256_CCM,
    MBEDTLS_TLS_RSA_WITH_AES_256_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_256_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_256_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_128_CCM,
    MBEDTLS_TLS_RSA_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_WITH_CAMELLIA_128_CBC_SHA,
    MBEDTLS_TLS_RSA_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_RSA_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_RSA_PSK_WITH_ARIA_128_GCM_SHA256,
    MBEDTLS_TLS_PSK_WITH_CHACHA20_POLY1305_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_256_GCM_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_256_CCM,
    MBEDTLS_TLS_PSK_WITH_AES_256_CBC_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_256_CBC_SHA,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_256_CBC_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_256_CCM_8,
    MBEDTLS_TLS_PSK_WITH_ARIA_256_GCM_SHA384,
    MBEDTLS_TLS_PSK_WITH_AES_128_GCM_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_128_CCM,
    MBEDTLS_TLS_PSK_WITH_AES_128_CBC_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_128_CBC_SHA,
    MBEDTLS_TLS_PSK_WITH_CAMELLIA_128_CBC_SHA256,
    MBEDTLS_TLS_PSK_WITH_AES_128_CCM_8,
    MBEDTLS_TLS_PSK_WITH_ARIA_128_GCM_SHA256,
};


/* true if RC4 or weak or NULL cipher suite
 *   (These ciphersuites are excluded from openssl "DEFAULT")
 * This is a subset of ciphers excluded for mod_openssl "!aNULL:!eNULL:!EXP" */
static int
mod_mbedtls_ssl_is_weak_ciphersuite (int id)
{
    for (uint32_t i = 0; i < sizeof(suite_RC4)/sizeof(suite_RC4[0]); ++i) {
        if (id == suite_RC4[i]) return 1;
    }
    for (uint32_t i = 0; i < sizeof(suite_weak)/sizeof(suite_weak[0]); ++i) {
        if (id == suite_weak[i]) return 1;
    }
    for (uint32_t i = 0; i < sizeof(suite_null)/sizeof(suite_null[0]); ++i) {
        if (id == suite_null[i]) return 1;
    }
    return 0;
}


static int
mod_mbedtls_ssl_DEFAULT_ciphersuite (server *srv, int *ids, int nids, int idsz)
{
    /* obtain default ciphersuite list and filter out weak or NULL */
    const int *dids = mbedtls_ssl_list_ciphersuites();
    int i = 0;
    while (dids[i] != 0) ++i;

    if (i >= idsz - (nids + 1)) {
        log_error(srv->errh, __FILE__, __LINE__,
          "MTLS: error: too many ciphersuites during list expand");
        return -1;
    }

    for (i = 0; dids[i] != 0; ++i) {
        if (!mod_mbedtls_ssl_is_weak_ciphersuite(dids[i]))
            ids[++nids] = dids[i];
    }

    return nids;
}


static int
mod_mbedtls_ssl_append_ciphersuite (server *srv, int *ids, int nids, int idsz, const int *x, int xsz)
{
    if (xsz >= idsz - (nids + 1)) {
        log_error(srv->errh, __FILE__, __LINE__,
          "MTLS: error: too many ciphersuites during list expand");
        return -1;
    }

    for (int i = 0; i < xsz; ++i)
        ids[++nids] = x[i];

    return nids;
}


static int
mod_mbedtls_ssl_conf_ciphersuites (server *srv, plugin_config_socket *s, buffer *ciphersuites, const buffer *cipherstring)
{
    /* reference: https://www.openssl.org/docs/man1.1.1/man1/ciphers.html
     * Attempt to parse *some* keywords from Ciphersuites and CipherString
     * !!! openssl uses a *different* naming scheme than does mbedTLS !!!
     * Since Ciphersuites in openssl takes only TLSv1.3 suites, and mbedTLS
     * does not currently support TLSv1.3, mapping of those names is not
     * currently provided.  Note that CipherString does allow cipher suites to
     * be listed, and this code does not currently attempt to provide mapping */

    char n[128]; /*(most ciphersuite names are about 40 chars)*/
    int ids[512];
    int nids = -1;
    const int idsz = (int)(sizeof(ids)/sizeof(*ids)-1);
    int crt_profile_default = 0;

    if (ciphersuites) {
        buffer *b = ciphersuites;
        buffer_to_upper(b); /*(ciphersuites are all uppercase (currently))*/
        for (const char *p, *e = b->ptr-1; e && (e = strchr((p = e+1),':')); ) {
            size_t len = e ? (size_t)(e - p) : strlen(p);
            if (len >= sizeof(n)) {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: skipped ciphersuite; too long: %.*s",
                  (int)len, p);
                continue;
            }
            memcpy(n, p, len);
            n[len] = '\0';

            int id = mbedtls_ssl_get_ciphersuite_id(n);
            if (0 == id) {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: skipped ciphersuite; not recognized: %.*s",
                  (int)len, n);
                continue;
            }

            /* allow any ciphersuite if explicitly listed, even weak or eNULL */
          #if 0
            if (mod_mbedtls_ssl_is_weak_ciphersuite(id)) {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: skipped ciphersuite; weak or NULL suite: %.*s",
                  (int)len, n);
                continue;
            }
          #endif

            if (nids >= idsz) {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: skipped ciphersuite; too many listed: %.*s",
                  (int)len, n);
                continue;
            }

            ids[++nids] = id;
        }
    }

    /* XXX: openssl config for CipherString=... is excessively complex.
     * If there is a need to enable specific ciphersuites, then that
     * can be accomplished with mod_mbedtls by specifying the list in
     * Ciphersuites=... in the ssl.openssl.ssl-conf-cmd directive.
     * (Alternatively, build mbedtls with specific set of cipher suites
     *  or modify mod_mbedtls code to specify the precise list).
     *
     * The tokens parsed here are a quick attempt to handle a few cases
     *
     * XXX: not done: could make a list of ciphers with bitflag of attributes
     *      to make future combining easier */
    if (cipherstring) {
        const buffer *b = cipherstring;
        const char *e = b->ptr;

        /* XXX: not done: no checking for duplication of ciphersuites
         * even if tokens overlap or are repeated */

        /* XXX: not done: might walk string and build up exclude list of !xxxxx
         * ciphersuites and walk string again, excluding as result list built */

        /* manually handle first token, since one-offs apply */
        /* (openssl syntax NOT fully supported) */
        int default_suite = 0;
        if (0 == strncmp(e, "!ALL", 4) || 0 == strncmp(e, "-ALL", 4)) {
            /* "!ALL" excluding all ciphers does not make sense; ignore */
            e += sizeof("!ALL")-1; /* same as sizeof("-ALL")-1 */
        }
        else if (0 == strncmp(e, CONST_STR_LEN("!DEFAULT"))
              || 0 == strncmp(e, CONST_STR_LEN("-DEFAULT"))) {
            /* "!DEFAULT" excluding default ciphers is empty list; no effect */
            e += sizeof("!DEFAULT")-1; /* same as sizeof("-DEFAULT")-1 */
        }
        else if (0 == strncmp(e, CONST_STR_LEN("DEFAULT"))) {
            e += sizeof("DEFAULT")-1;
            default_suite = 1;
        }
        else if (0 == /* effectively the same as "DEFAULT" */
                 strncmp(e, CONST_STR_LEN("ALL:!COMPLEMENTOFDEFAULT:!eNULL"))) {
            e += sizeof("ALL:!COMPLEMENTOFDEFAULT:!eNULL")-1;
            default_suite = 1;
        }
        else if (0 == strncmp(e, CONST_STR_LEN("SUITEB128"))
              || 0 == strncmp(e, CONST_STR_LEN("SUITEB128ONLY"))
              || 0 == strncmp(e, CONST_STR_LEN("SUITEB192"))) {
            mbedtls_ssl_conf_cert_profile(s->ssl_ctx,
                                          &mbedtls_x509_crt_profile_suiteb);
            /* re-initialize mbedtls_ssl_config defaults */
            mbedtls_mpi_free(&s->ssl_ctx->dhm_P);
            mbedtls_mpi_free(&s->ssl_ctx->dhm_G);
            int rc = mbedtls_ssl_config_defaults(s->ssl_ctx,
                                                 MBEDTLS_SSL_IS_SERVER,
                                                 MBEDTLS_SSL_TRANSPORT_STREAM,
                                                 MBEDTLS_SSL_PRESET_SUITEB);
            if (0 != rc) {
                elog(srv->errh, __FILE__,__LINE__, rc,
                     "Init of ssl config context SUITEB defaults failed");
                return 0;
            }
            e += (0 == strncmp(e, CONST_STR_LEN("SUITEB128ONLY")))
                 ? sizeof("SUITEB128ONLY")-1
                 : sizeof("SUITEB128")-1;
            if (*e)
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: ignoring cipher string after SUITEB: %s", e);
            return 1;
        }

        if (e != b->ptr && *e != ':' && *e != '\0') {
            log_error(srv->errh, __FILE__, __LINE__,
              "MTLS: error: missing support for cipher list: %s", b->ptr);
            return 0;
        }

        if (default_suite) {
            crt_profile_default = 1;
            nids =
              mod_mbedtls_ssl_DEFAULT_ciphersuite(srv, ids, nids, idsz);
            if (-1 == nids) return 0;
        }

        /* not handled: "ALL" is "DEFAULT" and "RC4" */
        /* not handled: "COMPLEMENTOFALL" is "eNULL" */

        int rc = 1;
        if (e == b->ptr || *e == '\0') --e; /*initial condition for loop below*/
        for (const char *p; e && (e = strchr((p = e+1),':')); ) {
            size_t len = e ? (size_t)(e - p) : strlen(p);
            if (len >= sizeof(n)) {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: skipped ciphersuite; too long: %.*s",
                  (int)len, p);
                continue;
            }
            char c = (*p == '!' || *p == '-' || *p == '+') ? *p : 0;
            size_t nlen = c ? len-1 : len;
            memcpy(n, c ? p+1 : p, nlen);
            n[nlen] = '\0';

            /* not handled: !xxxxx -xxxxx and most +xxxxx */
            if (c) {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: error: missing support for cipher list: %s", b->ptr);
            }

            /* ignore @STRENGTH sorting and ignore @SECLEVEL=n */
            char *a = strchr(n, '@');
            if (a) {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: ignored %s in %.*s", a, (int)len, p);
                *a = '\0';
                nlen = (size_t)(a - n);
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("TLSv1.2"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_TLSv12,
                         (int)(sizeof(suite_TLSv12)/sizeof(*suite_TLSv12)));
                if (-1 == nids) return 0;
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("TLSv1.0"))) {
                crt_profile_default = 1;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_TLSv10,
                         (int)(sizeof(suite_TLSv10)/sizeof(*suite_TLSv10)));
                if (-1 == nids) return 0;
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("SSLv3"))) {
                crt_profile_default = 1;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_SSLv3,
                         (int)(sizeof(suite_SSLv3)/sizeof(*suite_SSLv3)));
                if (-1 == nids) return 0;
                continue;
            }

            /* handle a popular recommendations
             *   ssl.cipher-list = "EECDH+AESGCM:EDH+AESGCM"
             *   ssl.cipher-list = "AES256+EECDH:AES256+EDH"
             * which uses AES hardware acceleration built into popular CPUs */
            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("ECDHE+AESGCM"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("EECDH+AESGCM"))) {
                if (nids + 4 >= idsz) {
                    log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: error: too many ciphersuites during list expand");
                    return 0;
                }
                ids[++nids] = MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384;
                ids[++nids] = MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384;
                ids[++nids] = MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256;
                ids[++nids] = MBEDTLS_TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256;
                continue;
            }
            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("DHE+AESGCM"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("EDH+AESGCM"))) {
                if (nids + 2 >= idsz) {
                    log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: error: too many ciphersuites during list expand");
                    return 0;
                }
                ids[++nids] = MBEDTLS_TLS_DHE_RSA_WITH_AES_256_GCM_SHA384;
                ids[++nids] = MBEDTLS_TLS_DHE_RSA_WITH_AES_128_GCM_SHA256;
                continue;
            }
            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("AES256+EECDH"))) {
                if (nids + 8 >= idsz) {
                    log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: error: too many ciphersuites during list expand");
                    return 0;
                }
                ids[++nids] = MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384;
                ids[++nids] = MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384;
                ids[++nids] = MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CCM;
                ids[++nids] = MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384;
                ids[++nids] = MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384;
                ids[++nids] = MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA;
                ids[++nids] = MBEDTLS_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA;
                ids[++nids] = MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8;
                continue;
            }
            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("AES256+EDH"))) {
                if (nids + 5 >= idsz) {
                    log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: error: too many ciphersuites during list expand");
                    return 0;
                }
                ids[++nids] = MBEDTLS_TLS_DHE_RSA_WITH_AES_256_GCM_SHA384;
                ids[++nids] = MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CCM;
                ids[++nids] = MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CBC_SHA256;
                ids[++nids] = MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CBC_SHA;
                ids[++nids] = MBEDTLS_TLS_DHE_RSA_WITH_AES_256_CCM_8;
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("HIGH"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_HIGH,
                         (int)(sizeof(suite_HIGH)/sizeof(*suite_HIGH)));
                if (-1 == nids) return 0;
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("AES256"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("AES"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_AES_256_ephemeral,
                         (int)(sizeof(suite_AES_256_ephemeral)
                              /sizeof(*suite_AES_256_ephemeral)));
                if (-1 == nids) return 0;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_AES_256,
                         (int)(sizeof(suite_AES_256)/sizeof(*suite_AES_256)));
                if (-1 == nids) return 0;
                /* XXX: not done: AES256 PSK suites */
                if (nlen == sizeof("AES256")-1) continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("AES128"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("AES"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_AES_128_ephemeral,
                         (int)(sizeof(suite_AES_128_ephemeral)
                              /sizeof(*suite_AES_128_ephemeral)));
                if (-1 == nids) return 0;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_AES_128,
                         (int)(sizeof(suite_AES_128)/sizeof(*suite_AES_128)));
                if (-1 == nids) return 0;
                /* XXX: not done: AES128 PSK suites */
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("CAMELLIA256"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("CAMELLIA"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_CAMELLIA_256_ephemeral,
                         (int)(sizeof(suite_CAMELLIA_256_ephemeral)
                              /sizeof(*suite_CAMELLIA_256_ephemeral)));
                if (-1 == nids) return 0;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_CAMELLIA_256,
                         (int)(sizeof(suite_CAMELLIA_256)
                              /sizeof(*suite_CAMELLIA_256)));
                if (-1 == nids) return 0;
                /* XXX: not done: CAMELLIA256 PSK suites */
                if (nlen == sizeof("CAMELLIA256")-1) continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("CAMELLIA128"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("CAMELLIA"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_CAMELLIA_128_ephemeral,
                         (int)(sizeof(suite_CAMELLIA_128_ephemeral)
                              /sizeof(*suite_CAMELLIA_128_ephemeral)));
                if (-1 == nids) return 0;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_CAMELLIA_128,
                         (int)(sizeof(suite_CAMELLIA_128)
                              /sizeof(*suite_CAMELLIA_128)));
                if (-1 == nids) return 0;
                /* XXX: not done: CAMELLIA128 PSK suites */
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("ARIA256"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("ARIA"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_ARIA_256_ephemeral,
                         (int)(sizeof(suite_ARIA_256_ephemeral)
                              /sizeof(*suite_ARIA_256_ephemeral)));
                if (-1 == nids) return 0;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_ARIA_256,
                         (int)(sizeof(suite_ARIA_256)/sizeof(*suite_ARIA_256)));
                if (-1 == nids) return 0;
                /* XXX: not done: ARIA256 PSK suites */
                if (nlen == sizeof("ARIA256")-1) continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("ARIA128"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("ARIA"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_ARIA_128_ephemeral,
                         (int)(sizeof(suite_ARIA_128_ephemeral)
                              /sizeof(*suite_ARIA_128_ephemeral)));
                if (-1 == nids) return 0;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_ARIA_128,
                         (int)(sizeof(suite_ARIA_128)/sizeof(*suite_ARIA_128)));
                if (-1 == nids) return 0;
                /* XXX: not done: ARIA128 PSK suites */
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("CHACHA20"))) {
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_CHACHAPOLY_ephemeral,
                         (int)(sizeof(suite_CHACHAPOLY_ephemeral)
                              /sizeof(*suite_CHACHAPOLY_ephemeral)));
                if (-1 == nids) return 0;
                /* XXX: not done: CHACHA20 PSK suites */
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("PSK"))) {
                /* XXX: intentionally not including overlapping eNULL ciphers */
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_PSK_ephemeral,
                         (int)(sizeof(suite_PSK_ephemeral)
                              /sizeof(*suite_PSK_ephemeral)));
                if (-1 == nids) return 0;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_RSA_PSK,
                         (int)(sizeof(suite_RSA_PSK)/sizeof(*suite_RSA_PSK)));
                if (-1 == nids) return 0;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_PSK,
                         (int)(sizeof(suite_PSK)/sizeof(*suite_PSK)));
                if (-1 == nids) return 0;
                continue;
            }

            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("3DES"))) {
                crt_profile_default = 1;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_3DES,
                         (int)(sizeof(suite_3DES)/sizeof(*suite_3DES)));
                if (-1 == nids) return 0;
                continue;
            }

            /* not recommended, but permitted if explicitly requested */
            /* "RC4" is same as openssl "COMPLEMENTOFALL" */
            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("RC4"))) {
                crt_profile_default = 1;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_RC4,
                         (int)(sizeof(suite_RC4)/sizeof(*suite_RC4)));
                if (-1 == nids) return 0;
                continue;
            }

            /* not recommended, but permitted if explicitly requested */
            if (buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("NULL"))
             || buffer_eq_icase_ss(n, nlen, CONST_STR_LEN("eNULL"))) {
                crt_profile_default = 1;
                nids = mod_mbedtls_ssl_append_ciphersuite(srv, ids, nids, idsz,
                         suite_null,
                         (int)(sizeof(suite_null)/sizeof(*suite_null)));
                if (-1 == nids) return 0;
                continue;
            }

            if (*e != ':' && *e != '\0') {
                log_error(srv->errh, __FILE__, __LINE__,
                  "MTLS: error: missing support for cipher list: %.*s",
                  (int)len, p);
                rc = 0;
                continue;
            }
        }
        if (0 == rc) return 0;
    }

    if (-1 == nids) {
        /* Do not set a default if ssl.cipher-list was set (and we are
         * are processing ssl.openssl.ssl-conf-cmd, not ssl.cipher-list) */
        if (cipherstring != s->ssl_cipher_list
            && !buffer_string_is_empty(s->ssl_cipher_list))
            return 1;

        /* obtain default ciphersuite list and filter out RC4, weak, and NULL */
        nids =
          mod_mbedtls_ssl_DEFAULT_ciphersuite(srv, ids, nids,
                                              sizeof(ids)/sizeof(*ids));
        if (-1 == nids) return 0;
    }

    ids[++nids] = 0; /* terminate list */
    ++nids;

    if (!crt_profile_default)
        mbedtls_ssl_conf_cert_profile(s->ssl_ctx,
                                      &mbedtls_x509_crt_profile_next);

    /* ciphersuites list must be persistent for lifetime of mbedtls_ssl_config*/
    s->ciphersuites = malloc(nids * sizeof(int));
    force_assert(s->ciphersuites);
    memcpy(s->ciphersuites, ids, nids * sizeof(int));

    mbedtls_ssl_conf_ciphersuites(s->ssl_ctx, s->ciphersuites);
    return 1;
}


static int
mod_mbedtls_ssl_append_curve (server *srv, mbedtls_ecp_group_id *ids, int nids, int idsz, const mbedtls_ecp_group_id id)
{
    if (1 >= idsz - (nids + 1)) {
        log_error(srv->errh, __FILE__, __LINE__,
          "MTLS: error: too many curves during list expand");
        return -1;
    }

    ids[++nids] = id;

    return nids;
}


static int
mod_mbedtls_ssl_conf_curves(server *srv, plugin_config_socket *s, const buffer *curvelist)
{
    mbedtls_ecp_group_id ids[512];
    int nids = -1;
    const int idsz = (int)(sizeof(ids)/sizeof(*ids)-1);
    const mbedtls_ecp_curve_info * const curve_info = mbedtls_ecp_curve_list();

    const buffer * const b = curvelist;
    for (const char *n, *e = b->ptr-1; e && (e = strchr((n = e+1),':')); ) {
        size_t len = e ? (size_t)(e - n) : strlen(n);
        /* similar to mbedtls_ecp_curve_info_from_name() */
        const mbedtls_ecp_curve_info *info;
        for (info = curve_info; info->grp_id != MBEDTLS_ECP_DP_NONE; ++info) {
            if (0 == strncmp(info->name, n, len) && info->name[len] == '\0')
                break;
        }
        if (info->grp_id == MBEDTLS_ECP_DP_NONE) {
            log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: unrecognized curve: %.*s; ignored", (int)len, n);
            continue;
        }

        nids = mod_mbedtls_ssl_append_curve(srv, ids, nids, idsz, info->grp_id);
        if (-1 == nids) return 0;
    }

    /* XXX: mod_openssl configures "prime256v1" if curve list not specified,
     * but mbedtls provides a list of supported curves if not explicitly set */
    if (-1 == nids) return 1; /* empty list; no-op */

    ids[++nids] = MBEDTLS_ECP_DP_NONE; /* terminate list */
    ++nids;

    /* curves list must be persistent for lifetime of mbedtls_ssl_config */
    s->curves = malloc(nids * sizeof(mbedtls_ecp_group_id));
    force_assert(s->curves);
    memcpy(s->curves, ids, nids * sizeof(mbedtls_ecp_group_id));

    mbedtls_ssl_conf_curves(s->ssl_ctx, s->curves);
    return 1;
}


static void
mod_mbedtls_ssl_conf_proto (server *srv, plugin_config_socket *s, const buffer *b, int max)
{
    int v = MBEDTLS_SSL_MINOR_VERSION_3; /* default: TLS v1.2 */
    if (NULL == b) /* default: min TLSv1.2, max TLSv1.2 */
        v = max ? MBEDTLS_SSL_MINOR_VERSION_3 : MBEDTLS_SSL_MINOR_VERSION_3;
    else if (buffer_eq_icase_slen(b, CONST_STR_LEN("None"))) /*"disable" limit*/
        v = max
          ? MBEDTLS_SSL_MINOR_VERSION_3  /* TLS v1.2 */
          : s->ssl_use_sslv3
              ? MBEDTLS_SSL_MINOR_VERSION_0  /* SSL v3.0 */
              : MBEDTLS_SSL_MINOR_VERSION_1; /* TLS v1.0 */
    else if (buffer_eq_icase_slen(b, CONST_STR_LEN("SSLv3")))
        v = MBEDTLS_SSL_MINOR_VERSION_0; /* SSL v3.0 */
    else if (buffer_eq_icase_slen(b, CONST_STR_LEN("TLSv1.0")))
        v = MBEDTLS_SSL_MINOR_VERSION_1; /* TLS v1.0 */
    else if (buffer_eq_icase_slen(b, CONST_STR_LEN("TLSv1.1")))
        v = MBEDTLS_SSL_MINOR_VERSION_2; /* TLS v1.1 */
    else if (buffer_eq_icase_slen(b, CONST_STR_LEN("TLSv1.2")))
        v = MBEDTLS_SSL_MINOR_VERSION_3; /* TLS v1.2 */
    else {
        if (buffer_eq_icase_slen(b, CONST_STR_LEN("TLSv1.3")))
            log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: ssl.openssl.ssl-conf-cmd %s TLSv1.3 not supported "
                      "by mod_mbedtls; using TLSv1.2",
                      max ? "MaxProtocol" : "MinProtocol");
        else if (buffer_eq_icase_slen(b, CONST_STR_LEN("DTLSv1"))
                 || buffer_eq_icase_slen(b, CONST_STR_LEN("DTLSv1.2"))) {
            log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: ssl.openssl.ssl-conf-cmd %s %s ignored",
                      max ? "MaxProtocol" : "MinProtocol", b->ptr);
            return;
        }
        else {
            log_error(srv->errh, __FILE__, __LINE__,
                      "MTLS: ssl.openssl.ssl-conf-cmd %s %s invalid; ignored",
                      max ? "MaxProtocol" : "MinProtocol", b->ptr);
            return;
        }
    }

    max
      ? mbedtls_ssl_conf_max_version(s->ssl_ctx,MBEDTLS_SSL_MAJOR_VERSION_3,v)
      : mbedtls_ssl_conf_min_version(s->ssl_ctx,MBEDTLS_SSL_MAJOR_VERSION_3,v);
}