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]\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 *scheme, *host, *path, *query; 193 char uri[256]; 194 int port; 195 int retries = 0; 196 197 SSL_CTX *ssl_ctx = NULL; 198 SSL *ssl; 199 struct bufferevent *bev; 200 struct evhttp_connection *evcon = NULL; 201 struct evhttp_request *req; 202 struct evkeyvalq *output_headers; 203 struct evbuffer *output_buffer; 204 205 int i; 206 int ret = 0; 207 enum { HTTP, HTTPS } type = HTTP; 208 209 for (i = 1; i < argc; i++) { 210 if (!strcmp("-url", argv[i])) { 211 if (i < argc - 1) { 212 url = argv[i + 1]; 213 } else { 214 syntax(); 215 goto error; 216 } 217 } else if (!strcmp("-ignore-cert", argv[i])) { 218 ignore_cert = 1; 219 } else if (!strcmp("-data", argv[i])) { 220 if (i < argc - 1) { 221 data_file = argv[i + 1]; 222 } else { 223 syntax(); 224 goto error; 225 } 226 } else if (!strcmp("-retries", argv[i])) { 227 if (i < argc - 1) { 228 retries = atoi(argv[i + 1]); 229 } else { 230 syntax(); 231 goto error; 232 } 233 } else if (!strcmp("-help", argv[i])) { 234 syntax(); 235 goto error; 236 } 237 } 238 239 if (!url) { 240 syntax(); 241 goto error; 242 } 243 244 #ifdef _WIN32 245 { 246 WORD wVersionRequested; 247 WSADATA wsaData; 248 int err; 249 250 wVersionRequested = MAKEWORD(2, 2); 251 252 err = WSAStartup(wVersionRequested, &wsaData); 253 if (err != 0) { 254 printf("WSAStartup failed with error: %d\n", err); 255 goto error; 256 } 257 } 258 #endif // _WIN32 259 260 http_uri = evhttp_uri_parse(url); 261 if (http_uri == NULL) { 262 err("malformed url"); 263 goto error; 264 } 265 266 scheme = evhttp_uri_get_scheme(http_uri); 267 if (scheme == NULL || (strcasecmp(scheme, "https") != 0 && 268 strcasecmp(scheme, "http") != 0)) { 269 err("url must be http or https"); 270 goto error; 271 } 272 273 host = evhttp_uri_get_host(http_uri); 274 if (host == NULL) { 275 err("url must have a host"); 276 goto error; 277 } 278 279 port = evhttp_uri_get_port(http_uri); 280 if (port == -1) { 281 port = (strcasecmp(scheme, "http") == 0) ? 80 : 443; 282 } 283 284 path = evhttp_uri_get_path(http_uri); 285 if (strlen(path) == 0) { 286 path = "/"; 287 } 288 289 query = evhttp_uri_get_query(http_uri); 290 if (query == NULL) { 291 snprintf(uri, sizeof(uri) - 1, "%s", path); 292 } else { 293 snprintf(uri, sizeof(uri) - 1, "%s?%s", path, query); 294 } 295 uri[sizeof(uri) - 1] = '\0'; 296 297 // Initialize OpenSSL 298 SSL_library_init(); 299 ERR_load_crypto_strings(); 300 SSL_load_error_strings(); 301 OpenSSL_add_all_algorithms(); 302 303 /* This isn't strictly necessary... OpenSSL performs RAND_poll 304 * automatically on first use of random number generator. */ 305 r = RAND_poll(); 306 if (r == 0) { 307 err_openssl("RAND_poll"); 308 goto error; 309 } 310 311 /* Create a new OpenSSL context */ 312 ssl_ctx = SSL_CTX_new(SSLv23_method()); 313 if (!ssl_ctx) { 314 err_openssl("SSL_CTX_new"); 315 goto error; 316 } 317 318 #ifndef _WIN32 319 /* TODO: Add certificate loading on Windows as well */ 320 321 /* Attempt to use the system's trusted root certificates. 322 * (This path is only valid for Debian-based systems.) */ 323 if (1 != SSL_CTX_load_verify_locations(ssl_ctx, 324 "/etc/ssl/certs/ca-certificates.crt", 325 NULL)) { 326 err_openssl("SSL_CTX_load_verify_locations"); 327 goto error; 328 } 329 /* Ask OpenSSL to verify the server certificate. Note that this 330 * does NOT include verifying that the hostname is correct. 331 * So, by itself, this means anyone with any legitimate 332 * CA-issued certificate for any website, can impersonate any 333 * other website in the world. This is not good. See "The 334 * Most Dangerous Code in the World" article at 335 * https://crypto.stanford.edu/~dabo/pubs/abstracts/ssl-client-bugs.html 336 */ 337 SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER, NULL); 338 /* This is how we solve the problem mentioned in the previous 339 * comment. We "wrap" OpenSSL's validation routine in our 340 * own routine, which also validates the hostname by calling 341 * the code provided by iSECPartners. Note that even though 342 * the "Everything You've Always Wanted to Know About 343 * Certificate Validation With OpenSSL (But Were Afraid to 344 * Ask)" paper from iSECPartners says very explicitly not to 345 * call SSL_CTX_set_cert_verify_callback (at the bottom of 346 * page 2), what we're doing here is safe because our 347 * cert_verify_callback() calls X509_verify_cert(), which is 348 * OpenSSL's built-in routine which would have been called if 349 * we hadn't set the callback. Therefore, we're just 350 * "wrapping" OpenSSL's routine, not replacing it. */ 351 SSL_CTX_set_cert_verify_callback(ssl_ctx, cert_verify_callback, 352 (void *) host); 353 #endif // not _WIN32 354 355 // Create event base 356 base = event_base_new(); 357 if (!base) { 358 perror("event_base_new()"); 359 goto error; 360 } 361 362 // Create OpenSSL bufferevent and stack evhttp on top of it 363 ssl = SSL_new(ssl_ctx); 364 if (ssl == NULL) { 365 err_openssl("SSL_new()"); 366 goto error; 367 } 368 369 #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME 370 // Set hostname for SNI extension 371 SSL_set_tlsext_host_name(ssl, host); 372 #endif 373 374 if (strcasecmp(scheme, "http") == 0) { 375 bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE); 376 } else { 377 type = HTTPS; 378 bev = bufferevent_openssl_socket_new(base, -1, ssl, 379 BUFFEREVENT_SSL_CONNECTING, 380 BEV_OPT_CLOSE_ON_FREE|BEV_OPT_DEFER_CALLBACKS); 381 } 382 383 if (bev == NULL) { 384 fprintf(stderr, "bufferevent_openssl_socket_new() failed\n"); 385 goto error; 386 } 387 388 bufferevent_openssl_set_allow_dirty_shutdown(bev, 1); 389 390 // For simplicity, we let DNS resolution block. Everything else should be 391 // asynchronous though. 392 evcon = evhttp_connection_base_bufferevent_new(base, NULL, bev, 393 host, port); 394 if (evcon == NULL) { 395 fprintf(stderr, "evhttp_connection_base_bufferevent_new() failed\n"); 396 goto error; 397 } 398 399 if (retries > 0) { 400 evhttp_connection_set_retries(evcon, retries); 401 } 402 403 // Fire off the request 404 req = evhttp_request_new(http_request_done, bev); 405 if (req == NULL) { 406 fprintf(stderr, "evhttp_request_new() failed\n"); 407 goto error; 408 } 409 410 output_headers = evhttp_request_get_output_headers(req); 411 evhttp_add_header(output_headers, "Host", host); 412 evhttp_add_header(output_headers, "Connection", "close"); 413 414 if (data_file) { 415 /* NOTE: In production code, you'd probably want to use 416 * evbuffer_add_file() or evbuffer_add_file_segment(), to 417 * avoid needless copying. */ 418 FILE * f = fopen(data_file, "rb"); 419 char buf[1024]; 420 size_t s; 421 size_t bytes = 0; 422 423 if (!f) { 424 syntax(); 425 goto error; 426 } 427 428 output_buffer = evhttp_request_get_output_buffer(req); 429 while ((s = fread(buf, 1, sizeof(buf), f)) > 0) { 430 evbuffer_add(output_buffer, buf, s); 431 bytes += s; 432 } 433 evutil_snprintf(buf, sizeof(buf)-1, "%lu", (unsigned long)bytes); 434 evhttp_add_header(output_headers, "Content-Length", buf); 435 fclose(f); 436 } 437 438 r = evhttp_make_request(evcon, req, data_file ? EVHTTP_REQ_POST : EVHTTP_REQ_GET, uri); 439 if (r != 0) { 440 fprintf(stderr, "evhttp_make_request() failed\n"); 441 goto error; 442 } 443 444 event_base_dispatch(base); 445 goto cleanup; 446 447 error: 448 ret = 1; 449 cleanup: 450 if (evcon) 451 evhttp_connection_free(evcon); 452 if (http_uri) 453 evhttp_uri_free(http_uri); 454 event_base_free(base); 455 456 if (ssl_ctx) 457 SSL_CTX_free(ssl_ctx); 458 if (type == HTTP) 459 SSL_free(ssl); 460 EVP_cleanup(); 461 ERR_free_strings(); 462 463 ERR_remove_state(0); 464 CRYPTO_cleanup_all_ex_data(); 465 466 sk_SSL_COMP_free(SSL_COMP_get_compression_methods()); 467 468 #ifdef _WIN32 469 WSACleanup(); 470 #endif 471 472 return ret; 473 } 474