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 int ignore_cert = 0; 49 50 static void 51 http_request_done(struct evhttp_request *req, void *ctx) 52 { 53 char buffer[256]; 54 int nread; 55 56 if (!req || !evhttp_request_get_response_code(req)) { 57 /* If req is NULL, it means an error occurred, but 58 * sadly we are mostly left guessing what the error 59 * might have been. We'll do our best... */ 60 struct bufferevent *bev = (struct bufferevent *) ctx; 61 unsigned long oslerr; 62 int printed_err = 0; 63 int errcode = EVUTIL_SOCKET_ERROR(); 64 fprintf(stderr, "some request failed - no idea which one though!\n"); 65 /* Print out the OpenSSL error queue that libevent 66 * squirreled away for us, if any. */ 67 while ((oslerr = bufferevent_get_openssl_error(bev))) { 68 ERR_error_string_n(oslerr, buffer, sizeof(buffer)); 69 fprintf(stderr, "%s\n", buffer); 70 printed_err = 1; 71 } 72 /* If the OpenSSL error queue was empty, maybe it was a 73 * socket error; let's try printing that. */ 74 if (! printed_err) 75 fprintf(stderr, "socket error = %s (%d)\n", 76 evutil_socket_error_to_string(errcode), 77 errcode); 78 return; 79 } 80 81 fprintf(stderr, "Response line: %d %s\n", 82 evhttp_request_get_response_code(req), 83 evhttp_request_get_response_code_line(req)); 84 85 while ((nread = evbuffer_remove(evhttp_request_get_input_buffer(req), 86 buffer, sizeof(buffer))) 87 > 0) { 88 /* These are just arbitrary chunks of 256 bytes. 89 * They are not lines, so we can't treat them as such. */ 90 fwrite(buffer, nread, 1, stdout); 91 } 92 } 93 94 static void 95 syntax(void) 96 { 97 fputs("Syntax:\n", stderr); 98 fputs(" https-client -url <https-url> [-data data-file.bin] [-ignore-cert] [-retries num] [-timeout sec] [-crt crt]\n", stderr); 99 fputs("Example:\n", stderr); 100 fputs(" https-client -url https://ip.appspot.com/\n", stderr); 101 } 102 103 static void 104 err(const char *msg) 105 { 106 fputs(msg, stderr); 107 } 108 109 static void 110 err_openssl(const char *func) 111 { 112 fprintf (stderr, "%s failed:\n", func); 113 114 /* This is the OpenSSL function that prints the contents of the 115 * error stack to the specified file handle. */ 116 ERR_print_errors_fp (stderr); 117 118 exit(1); 119 } 120 121 #ifndef _WIN32 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 #endif 185 186 int 187 main(int argc, char **argv) 188 { 189 int r; 190 struct event_base *base = NULL; 191 struct evhttp_uri *http_uri = NULL; 192 const char *url = NULL, *data_file = NULL; 193 const char *crt = NULL; 194 const char *scheme, *host, *path, *query; 195 char uri[256]; 196 int port; 197 int retries = 0; 198 int timeout = -1; 199 200 SSL_CTX *ssl_ctx = NULL; 201 SSL *ssl = NULL; 202 struct bufferevent *bev; 203 struct evhttp_connection *evcon = NULL; 204 struct evhttp_request *req; 205 struct evkeyvalq *output_headers; 206 struct evbuffer *output_buffer; 207 208 int i; 209 int ret = 0; 210 enum { HTTP, HTTPS } type = HTTP; 211 212 for (i = 1; i < argc; i++) { 213 if (!strcmp("-url", argv[i])) { 214 if (i < argc - 1) { 215 url = argv[i + 1]; 216 } else { 217 syntax(); 218 goto error; 219 } 220 } else if (!strcmp("-crt", argv[i])) { 221 if (i < argc - 1) { 222 crt = argv[i + 1]; 223 } else { 224 syntax(); 225 goto error; 226 } 227 } else if (!strcmp("-ignore-cert", argv[i])) { 228 ignore_cert = 1; 229 } else if (!strcmp("-data", argv[i])) { 230 if (i < argc - 1) { 231 data_file = argv[i + 1]; 232 } else { 233 syntax(); 234 goto error; 235 } 236 } else if (!strcmp("-retries", argv[i])) { 237 if (i < argc - 1) { 238 retries = atoi(argv[i + 1]); 239 } else { 240 syntax(); 241 goto error; 242 } 243 } else if (!strcmp("-timeout", argv[i])) { 244 if (i < argc - 1) { 245 timeout = atoi(argv[i + 1]); 246 } else { 247 syntax(); 248 goto error; 249 } 250 } else if (!strcmp("-help", argv[i])) { 251 syntax(); 252 goto error; 253 } 254 } 255 256 if (!url) { 257 syntax(); 258 goto error; 259 } 260 261 #ifdef _WIN32 262 { 263 WORD wVersionRequested; 264 WSADATA wsaData; 265 int err; 266 267 wVersionRequested = MAKEWORD(2, 2); 268 269 err = WSAStartup(wVersionRequested, &wsaData); 270 if (err != 0) { 271 printf("WSAStartup failed with error: %d\n", err); 272 goto error; 273 } 274 } 275 #endif // _WIN32 276 277 http_uri = evhttp_uri_parse(url); 278 if (http_uri == NULL) { 279 err("malformed url"); 280 goto error; 281 } 282 283 scheme = evhttp_uri_get_scheme(http_uri); 284 if (scheme == NULL || (strcasecmp(scheme, "https") != 0 && 285 strcasecmp(scheme, "http") != 0)) { 286 err("url must be http or https"); 287 goto error; 288 } 289 290 host = evhttp_uri_get_host(http_uri); 291 if (host == NULL) { 292 err("url must have a host"); 293 goto error; 294 } 295 296 port = evhttp_uri_get_port(http_uri); 297 if (port == -1) { 298 port = (strcasecmp(scheme, "http") == 0) ? 80 : 443; 299 } 300 301 path = evhttp_uri_get_path(http_uri); 302 if (strlen(path) == 0) { 303 path = "/"; 304 } 305 306 query = evhttp_uri_get_query(http_uri); 307 if (query == NULL) { 308 snprintf(uri, sizeof(uri) - 1, "%s", path); 309 } else { 310 snprintf(uri, sizeof(uri) - 1, "%s?%s", path, query); 311 } 312 uri[sizeof(uri) - 1] = '\0'; 313 314 #if (OPENSSL_VERSION_NUMBER < 0x10100000L) || \ 315 (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x20700000L) 316 // Initialize OpenSSL 317 SSL_library_init(); 318 ERR_load_crypto_strings(); 319 SSL_load_error_strings(); 320 OpenSSL_add_all_algorithms(); 321 #endif 322 323 /* This isn't strictly necessary... OpenSSL performs RAND_poll 324 * automatically on first use of random number generator. */ 325 r = RAND_poll(); 326 if (r == 0) { 327 err_openssl("RAND_poll"); 328 goto error; 329 } 330 331 /* Create a new OpenSSL context */ 332 ssl_ctx = SSL_CTX_new(SSLv23_method()); 333 if (!ssl_ctx) { 334 err_openssl("SSL_CTX_new"); 335 goto error; 336 } 337 338 #ifndef _WIN32 339 /* TODO: Add certificate loading on Windows as well */ 340 341 if (crt == NULL) { 342 X509_STORE *store; 343 /* Attempt to use the system's trusted root certificates. */ 344 store = SSL_CTX_get_cert_store(ssl_ctx); 345 if (X509_STORE_set_default_paths(store) != 1) { 346 err_openssl("X509_STORE_set_default_paths"); 347 goto error; 348 } 349 } else { 350 if (SSL_CTX_load_verify_locations(ssl_ctx, crt, NULL) != 1) { 351 err_openssl("SSL_CTX_load_verify_locations"); 352 goto error; 353 } 354 } 355 /* Ask OpenSSL to verify the server certificate. Note that this 356 * does NOT include verifying that the hostname is correct. 357 * So, by itself, this means anyone with any legitimate 358 * CA-issued certificate for any website, can impersonate any 359 * other website in the world. This is not good. See "The 360 * Most Dangerous Code in the World" article at 361 * https://crypto.stanford.edu/~dabo/pubs/abstracts/ssl-client-bugs.html 362 */ 363 SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER, NULL); 364 /* This is how we solve the problem mentioned in the previous 365 * comment. We "wrap" OpenSSL's validation routine in our 366 * own routine, which also validates the hostname by calling 367 * the code provided by iSECPartners. Note that even though 368 * the "Everything You've Always Wanted to Know About 369 * Certificate Validation With OpenSSL (But Were Afraid to 370 * Ask)" paper from iSECPartners says very explicitly not to 371 * call SSL_CTX_set_cert_verify_callback (at the bottom of 372 * page 2), what we're doing here is safe because our 373 * cert_verify_callback() calls X509_verify_cert(), which is 374 * OpenSSL's built-in routine which would have been called if 375 * we hadn't set the callback. Therefore, we're just 376 * "wrapping" OpenSSL's routine, not replacing it. */ 377 SSL_CTX_set_cert_verify_callback(ssl_ctx, cert_verify_callback, 378 (void *) host); 379 #else // _WIN32 380 (void)crt; 381 #endif // _WIN32 382 383 // Create event base 384 base = event_base_new(); 385 if (!base) { 386 perror("event_base_new()"); 387 goto error; 388 } 389 390 // Create OpenSSL bufferevent and stack evhttp on top of it 391 ssl = SSL_new(ssl_ctx); 392 if (ssl == NULL) { 393 err_openssl("SSL_new()"); 394 goto error; 395 } 396 397 #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME 398 // Set hostname for SNI extension 399 SSL_set_tlsext_host_name(ssl, host); 400 #endif 401 402 if (strcasecmp(scheme, "http") == 0) { 403 bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE); 404 } else { 405 type = HTTPS; 406 bev = bufferevent_openssl_socket_new(base, -1, ssl, 407 BUFFEREVENT_SSL_CONNECTING, 408 BEV_OPT_CLOSE_ON_FREE|BEV_OPT_DEFER_CALLBACKS); 409 } 410 411 if (bev == NULL) { 412 fprintf(stderr, "bufferevent_openssl_socket_new() failed\n"); 413 goto error; 414 } 415 416 bufferevent_openssl_set_allow_dirty_shutdown(bev, 1); 417 418 // For simplicity, we let DNS resolution block. Everything else should be 419 // asynchronous though. 420 evcon = evhttp_connection_base_bufferevent_new(base, NULL, bev, 421 host, port); 422 if (evcon == NULL) { 423 fprintf(stderr, "evhttp_connection_base_bufferevent_new() failed\n"); 424 goto error; 425 } 426 427 if (retries > 0) { 428 evhttp_connection_set_retries(evcon, retries); 429 } 430 if (timeout >= 0) { 431 evhttp_connection_set_timeout(evcon, timeout); 432 } 433 434 // Fire off the request 435 req = evhttp_request_new(http_request_done, bev); 436 if (req == NULL) { 437 fprintf(stderr, "evhttp_request_new() failed\n"); 438 goto error; 439 } 440 441 output_headers = evhttp_request_get_output_headers(req); 442 evhttp_add_header(output_headers, "Host", host); 443 evhttp_add_header(output_headers, "Connection", "close"); 444 445 if (data_file) { 446 /* NOTE: In production code, you'd probably want to use 447 * evbuffer_add_file() or evbuffer_add_file_segment(), to 448 * avoid needless copying. */ 449 FILE * f = fopen(data_file, "rb"); 450 char buf[1024]; 451 size_t s; 452 size_t bytes = 0; 453 454 if (!f) { 455 syntax(); 456 goto error; 457 } 458 459 output_buffer = evhttp_request_get_output_buffer(req); 460 while ((s = fread(buf, 1, sizeof(buf), f)) > 0) { 461 evbuffer_add(output_buffer, buf, s); 462 bytes += s; 463 } 464 evutil_snprintf(buf, sizeof(buf)-1, "%lu", (unsigned long)bytes); 465 evhttp_add_header(output_headers, "Content-Length", buf); 466 fclose(f); 467 } 468 469 r = evhttp_make_request(evcon, req, data_file ? EVHTTP_REQ_POST : EVHTTP_REQ_GET, uri); 470 if (r != 0) { 471 fprintf(stderr, "evhttp_make_request() failed\n"); 472 goto error; 473 } 474 475 event_base_dispatch(base); 476 goto cleanup; 477 478 error: 479 ret = 1; 480 cleanup: 481 if (evcon) 482 evhttp_connection_free(evcon); 483 if (http_uri) 484 evhttp_uri_free(http_uri); 485 if (base) 486 event_base_free(base); 487 488 if (ssl_ctx) 489 SSL_CTX_free(ssl_ctx); 490 if (type == HTTP && ssl) 491 SSL_free(ssl); 492 #if (OPENSSL_VERSION_NUMBER < 0x10100000L) || \ 493 (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x20700000L) 494 EVP_cleanup(); 495 ERR_free_strings(); 496 497 #if OPENSSL_VERSION_NUMBER < 0x10000000L 498 ERR_remove_state(0); 499 #else 500 ERR_remove_thread_state(NULL); 501 #endif 502 503 CRYPTO_cleanup_all_ex_data(); 504 505 sk_SSL_COMP_free(SSL_COMP_get_compression_methods()); 506 #endif /* (OPENSSL_VERSION_NUMBER < 0x10100000L) || \ 507 (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x20700000L) */ 508 509 #ifdef _WIN32 510 WSACleanup(); 511 #endif 512 513 return ret; 514 } 515