1 /* 2 This is an example of how to hook up evhttp with bufferevent_ssl 3 4 It just GETs an https URL given on the command-line and prints the response 5 body to stdout. 6 7 Actually, it also accepts plain http URLs to make it easy to compare http vs 8 https code paths. 9 10 Loosely based on le-proxy.c. 11 */ 12 13 // Get rid of OSX 10.7 and greater deprecation warnings. 14 #if defined(__APPLE__) && defined(__clang__) 15 #pragma clang diagnostic ignored "-Wdeprecated-declarations" 16 #endif 17 18 #include <stdio.h> 19 #include <assert.h> 20 #include <stdlib.h> 21 #include <string.h> 22 #include <errno.h> 23 24 #ifdef _WIN32 25 #include <winsock2.h> 26 #include <ws2tcpip.h> 27 28 #define snprintf _snprintf 29 #define strcasecmp _stricmp 30 #else 31 #include <sys/socket.h> 32 #include <netinet/in.h> 33 #endif 34 35 #include <event2/bufferevent_ssl.h> 36 #include <event2/bufferevent.h> 37 #include <event2/buffer.h> 38 #include <event2/listener.h> 39 #include <event2/util.h> 40 #include <event2/http.h> 41 42 #include <openssl/ssl.h> 43 #include <openssl/err.h> 44 #include <openssl/rand.h> 45 46 #include "openssl_hostname_validation.h" 47 48 static struct event_base *base; 49 static int ignore_cert = 0; 50 51 static void 52 http_request_done(struct evhttp_request *req, void *ctx) 53 { 54 char buffer[256]; 55 int nread; 56 57 if (req == NULL) { 58 /* If req is NULL, it means an error occurred, but 59 * sadly we are mostly left guessing what the error 60 * might have been. We'll do our best... */ 61 struct bufferevent *bev = (struct bufferevent *) ctx; 62 unsigned long oslerr; 63 int printed_err = 0; 64 int errcode = EVUTIL_SOCKET_ERROR(); 65 fprintf(stderr, "some request failed - no idea which one though!\n"); 66 /* Print out the OpenSSL error queue that libevent 67 * squirreled away for us, if any. */ 68 while ((oslerr = bufferevent_get_openssl_error(bev))) { 69 ERR_error_string_n(oslerr, buffer, sizeof(buffer)); 70 fprintf(stderr, "%s\n", buffer); 71 printed_err = 1; 72 } 73 /* If the OpenSSL error queue was empty, maybe it was a 74 * socket error; let's try printing that. */ 75 if (! printed_err) 76 fprintf(stderr, "socket error = %s (%d)\n", 77 evutil_socket_error_to_string(errcode), 78 errcode); 79 return; 80 } 81 82 fprintf(stderr, "Response line: %d %s\n", 83 evhttp_request_get_response_code(req), 84 evhttp_request_get_response_code_line(req)); 85 86 while ((nread = evbuffer_remove(evhttp_request_get_input_buffer(req), 87 buffer, sizeof(buffer))) 88 > 0) { 89 /* These are just arbitrary chunks of 256 bytes. 90 * They are not lines, so we can't treat them as such. */ 91 fwrite(buffer, nread, 1, stdout); 92 } 93 } 94 95 static void 96 syntax(void) 97 { 98 fputs("Syntax:\n", stderr); 99 fputs(" https-client -url <https-url> [-data data-file.bin] [-ignore-cert] [-retries num] [-timeout sec] [-crt crt]\n", stderr); 100 fputs("Example:\n", stderr); 101 fputs(" https-client -url https://ip.appspot.com/\n", stderr); 102 } 103 104 static void 105 err(const char *msg) 106 { 107 fputs(msg, stderr); 108 } 109 110 static void 111 err_openssl(const char *func) 112 { 113 fprintf (stderr, "%s failed:\n", func); 114 115 /* This is the OpenSSL function that prints the contents of the 116 * error stack to the specified file handle. */ 117 ERR_print_errors_fp (stderr); 118 119 exit(1); 120 } 121 122 /* See http://archives.seul.org/libevent/users/Jan-2013/msg00039.html */ 123 static int cert_verify_callback(X509_STORE_CTX *x509_ctx, void *arg) 124 { 125 char cert_str[256]; 126 const char *host = (const char *) arg; 127 const char *res_str = "X509_verify_cert failed"; 128 HostnameValidationResult res = Error; 129 130 /* This is the function that OpenSSL would call if we hadn't called 131 * SSL_CTX_set_cert_verify_callback(). Therefore, we are "wrapping" 132 * the default functionality, rather than replacing it. */ 133 int ok_so_far = 0; 134 135 X509 *server_cert = NULL; 136 137 if (ignore_cert) { 138 return 1; 139 } 140 141 ok_so_far = X509_verify_cert(x509_ctx); 142 143 server_cert = X509_STORE_CTX_get_current_cert(x509_ctx); 144 145 if (ok_so_far) { 146 res = validate_hostname(host, server_cert); 147 148 switch (res) { 149 case MatchFound: 150 res_str = "MatchFound"; 151 break; 152 case MatchNotFound: 153 res_str = "MatchNotFound"; 154 break; 155 case NoSANPresent: 156 res_str = "NoSANPresent"; 157 break; 158 case MalformedCertificate: 159 res_str = "MalformedCertificate"; 160 break; 161 case Error: 162 res_str = "Error"; 163 break; 164 default: 165 res_str = "WTF!"; 166 break; 167 } 168 } 169 170 X509_NAME_oneline(X509_get_subject_name (server_cert), 171 cert_str, sizeof (cert_str)); 172 173 if (res == MatchFound) { 174 printf("https server '%s' has this certificate, " 175 "which looks good to me:\n%s\n", 176 host, cert_str); 177 return 1; 178 } else { 179 printf("Got '%s' for hostname '%s' and certificate:\n%s\n", 180 res_str, host, cert_str); 181 return 0; 182 } 183 } 184 185 int 186 main(int argc, char **argv) 187 { 188 int r; 189 190 struct evhttp_uri *http_uri = NULL; 191 const char *url = NULL, *data_file = NULL; 192 const char *crt = "/etc/ssl/certs/ca-certificates.crt"; 193 const char *scheme, *host, *path, *query; 194 char uri[256]; 195 int port; 196 int retries = 0; 197 int timeout = -1; 198 199 SSL_CTX *ssl_ctx = NULL; 200 SSL *ssl = NULL; 201 struct bufferevent *bev; 202 struct evhttp_connection *evcon = NULL; 203 struct evhttp_request *req; 204 struct evkeyvalq *output_headers; 205 struct evbuffer *output_buffer; 206 207 int i; 208 int ret = 0; 209 enum { HTTP, HTTPS } type = HTTP; 210 211 for (i = 1; i < argc; i++) { 212 if (!strcmp("-url", argv[i])) { 213 if (i < argc - 1) { 214 url = argv[i + 1]; 215 } else { 216 syntax(); 217 goto error; 218 } 219 } else if (!strcmp("-crt", argv[i])) { 220 if (i < argc - 1) { 221 crt = argv[i + 1]; 222 } else { 223 syntax(); 224 goto error; 225 } 226 } else if (!strcmp("-ignore-cert", argv[i])) { 227 ignore_cert = 1; 228 } else if (!strcmp("-data", argv[i])) { 229 if (i < argc - 1) { 230 data_file = argv[i + 1]; 231 } else { 232 syntax(); 233 goto error; 234 } 235 } else if (!strcmp("-retries", argv[i])) { 236 if (i < argc - 1) { 237 retries = atoi(argv[i + 1]); 238 } else { 239 syntax(); 240 goto error; 241 } 242 } else if (!strcmp("-timeout", argv[i])) { 243 if (i < argc - 1) { 244 timeout = atoi(argv[i + 1]); 245 } else { 246 syntax(); 247 goto error; 248 } 249 } else if (!strcmp("-help", argv[i])) { 250 syntax(); 251 goto error; 252 } 253 } 254 255 if (!url) { 256 syntax(); 257 goto error; 258 } 259 260 #ifdef _WIN32 261 { 262 WORD wVersionRequested; 263 WSADATA wsaData; 264 int err; 265 266 wVersionRequested = MAKEWORD(2, 2); 267 268 err = WSAStartup(wVersionRequested, &wsaData); 269 if (err != 0) { 270 printf("WSAStartup failed with error: %d\n", err); 271 goto error; 272 } 273 } 274 #endif // _WIN32 275 276 http_uri = evhttp_uri_parse(url); 277 if (http_uri == NULL) { 278 err("malformed url"); 279 goto error; 280 } 281 282 scheme = evhttp_uri_get_scheme(http_uri); 283 if (scheme == NULL || (strcasecmp(scheme, "https") != 0 && 284 strcasecmp(scheme, "http") != 0)) { 285 err("url must be http or https"); 286 goto error; 287 } 288 289 host = evhttp_uri_get_host(http_uri); 290 if (host == NULL) { 291 err("url must have a host"); 292 goto error; 293 } 294 295 port = evhttp_uri_get_port(http_uri); 296 if (port == -1) { 297 port = (strcasecmp(scheme, "http") == 0) ? 80 : 443; 298 } 299 300 path = evhttp_uri_get_path(http_uri); 301 if (strlen(path) == 0) { 302 path = "/"; 303 } 304 305 query = evhttp_uri_get_query(http_uri); 306 if (query == NULL) { 307 snprintf(uri, sizeof(uri) - 1, "%s", path); 308 } else { 309 snprintf(uri, sizeof(uri) - 1, "%s?%s", path, query); 310 } 311 uri[sizeof(uri) - 1] = '\0'; 312 313 #if OPENSSL_VERSION_NUMBER < 0x10100000L 314 // Initialize OpenSSL 315 SSL_library_init(); 316 ERR_load_crypto_strings(); 317 SSL_load_error_strings(); 318 OpenSSL_add_all_algorithms(); 319 #endif 320 321 /* This isn't strictly necessary... OpenSSL performs RAND_poll 322 * automatically on first use of random number generator. */ 323 r = RAND_poll(); 324 if (r == 0) { 325 err_openssl("RAND_poll"); 326 goto error; 327 } 328 329 /* Create a new OpenSSL context */ 330 ssl_ctx = SSL_CTX_new(SSLv23_method()); 331 if (!ssl_ctx) { 332 err_openssl("SSL_CTX_new"); 333 goto error; 334 } 335 336 #ifndef _WIN32 337 /* TODO: Add certificate loading on Windows as well */ 338 339 /* Attempt to use the system's trusted root certificates. 340 * (This path is only valid for Debian-based systems.) */ 341 if (1 != SSL_CTX_load_verify_locations(ssl_ctx, crt, NULL)) { 342 err_openssl("SSL_CTX_load_verify_locations"); 343 goto error; 344 } 345 /* Ask OpenSSL to verify the server certificate. Note that this 346 * does NOT include verifying that the hostname is correct. 347 * So, by itself, this means anyone with any legitimate 348 * CA-issued certificate for any website, can impersonate any 349 * other website in the world. This is not good. See "The 350 * Most Dangerous Code in the World" article at 351 * https://crypto.stanford.edu/~dabo/pubs/abstracts/ssl-client-bugs.html 352 */ 353 SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER, NULL); 354 /* This is how we solve the problem mentioned in the previous 355 * comment. We "wrap" OpenSSL's validation routine in our 356 * own routine, which also validates the hostname by calling 357 * the code provided by iSECPartners. Note that even though 358 * the "Everything You've Always Wanted to Know About 359 * Certificate Validation With OpenSSL (But Were Afraid to 360 * Ask)" paper from iSECPartners says very explicitly not to 361 * call SSL_CTX_set_cert_verify_callback (at the bottom of 362 * page 2), what we're doing here is safe because our 363 * cert_verify_callback() calls X509_verify_cert(), which is 364 * OpenSSL's built-in routine which would have been called if 365 * we hadn't set the callback. Therefore, we're just 366 * "wrapping" OpenSSL's routine, not replacing it. */ 367 SSL_CTX_set_cert_verify_callback(ssl_ctx, cert_verify_callback, 368 (void *) host); 369 #endif // not _WIN32 370 371 // Create event base 372 base = event_base_new(); 373 if (!base) { 374 perror("event_base_new()"); 375 goto error; 376 } 377 378 // Create OpenSSL bufferevent and stack evhttp on top of it 379 ssl = SSL_new(ssl_ctx); 380 if (ssl == NULL) { 381 err_openssl("SSL_new()"); 382 goto error; 383 } 384 385 #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME 386 // Set hostname for SNI extension 387 SSL_set_tlsext_host_name(ssl, host); 388 #endif 389 390 if (strcasecmp(scheme, "http") == 0) { 391 bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE); 392 } else { 393 type = HTTPS; 394 bev = bufferevent_openssl_socket_new(base, -1, ssl, 395 BUFFEREVENT_SSL_CONNECTING, 396 BEV_OPT_CLOSE_ON_FREE|BEV_OPT_DEFER_CALLBACKS); 397 } 398 399 if (bev == NULL) { 400 fprintf(stderr, "bufferevent_openssl_socket_new() failed\n"); 401 goto error; 402 } 403 404 bufferevent_openssl_set_allow_dirty_shutdown(bev, 1); 405 406 // For simplicity, we let DNS resolution block. Everything else should be 407 // asynchronous though. 408 evcon = evhttp_connection_base_bufferevent_new(base, NULL, bev, 409 host, port); 410 if (evcon == NULL) { 411 fprintf(stderr, "evhttp_connection_base_bufferevent_new() failed\n"); 412 goto error; 413 } 414 415 if (retries > 0) { 416 evhttp_connection_set_retries(evcon, retries); 417 } 418 if (timeout >= 0) { 419 evhttp_connection_set_timeout(evcon, timeout); 420 } 421 422 // Fire off the request 423 req = evhttp_request_new(http_request_done, bev); 424 if (req == NULL) { 425 fprintf(stderr, "evhttp_request_new() failed\n"); 426 goto error; 427 } 428 429 output_headers = evhttp_request_get_output_headers(req); 430 evhttp_add_header(output_headers, "Host", host); 431 evhttp_add_header(output_headers, "Connection", "close"); 432 433 if (data_file) { 434 /* NOTE: In production code, you'd probably want to use 435 * evbuffer_add_file() or evbuffer_add_file_segment(), to 436 * avoid needless copying. */ 437 FILE * f = fopen(data_file, "rb"); 438 char buf[1024]; 439 size_t s; 440 size_t bytes = 0; 441 442 if (!f) { 443 syntax(); 444 goto error; 445 } 446 447 output_buffer = evhttp_request_get_output_buffer(req); 448 while ((s = fread(buf, 1, sizeof(buf), f)) > 0) { 449 evbuffer_add(output_buffer, buf, s); 450 bytes += s; 451 } 452 evutil_snprintf(buf, sizeof(buf)-1, "%lu", (unsigned long)bytes); 453 evhttp_add_header(output_headers, "Content-Length", buf); 454 fclose(f); 455 } 456 457 r = evhttp_make_request(evcon, req, data_file ? EVHTTP_REQ_POST : EVHTTP_REQ_GET, uri); 458 if (r != 0) { 459 fprintf(stderr, "evhttp_make_request() failed\n"); 460 goto error; 461 } 462 463 event_base_dispatch(base); 464 goto cleanup; 465 466 error: 467 ret = 1; 468 cleanup: 469 if (evcon) 470 evhttp_connection_free(evcon); 471 if (http_uri) 472 evhttp_uri_free(http_uri); 473 event_base_free(base); 474 475 if (ssl_ctx) 476 SSL_CTX_free(ssl_ctx); 477 if (type == HTTP && ssl) 478 SSL_free(ssl); 479 #if OPENSSL_VERSION_NUMBER < 0x10100000L 480 EVP_cleanup(); 481 ERR_free_strings(); 482 483 #ifdef EVENT__HAVE_ERR_REMOVE_THREAD_STATE 484 ERR_remove_thread_state(NULL); 485 #else 486 ERR_remove_state(0); 487 #endif 488 CRYPTO_cleanup_all_ex_data(); 489 490 sk_SSL_COMP_free(SSL_COMP_get_compression_methods()); 491 #endif /*OPENSSL_VERSION_NUMBER < 0x10100000L */ 492 493 #ifdef _WIN32 494 WSACleanup(); 495 #endif 496 497 return ret; 498 } 499