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
http_request_done(struct evhttp_request * req,void * ctx)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
syntax(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
err(const char * msg)104 err(const char *msg)
105 {
106 fputs(msg, stderr);
107 }
108
109 static void
err_openssl(const char * func)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 /* See http://archives.seul.org/libevent/users/Jan-2013/msg00039.html */
cert_verify_callback(X509_STORE_CTX * x509_ctx,void * arg)122 static int cert_verify_callback(X509_STORE_CTX *x509_ctx, void *arg)
123 {
124 char cert_str[256];
125 const char *host = (const char *) arg;
126 const char *res_str = "X509_verify_cert failed";
127 HostnameValidationResult res = Error;
128
129 /* This is the function that OpenSSL would call if we hadn't called
130 * SSL_CTX_set_cert_verify_callback(). Therefore, we are "wrapping"
131 * the default functionality, rather than replacing it. */
132 int ok_so_far = 0;
133
134 X509 *server_cert = NULL;
135
136 if (ignore_cert) {
137 return 1;
138 }
139
140 ok_so_far = X509_verify_cert(x509_ctx);
141
142 server_cert = X509_STORE_CTX_get_current_cert(x509_ctx);
143
144 if (ok_so_far) {
145 res = validate_hostname(host, server_cert);
146
147 switch (res) {
148 case MatchFound:
149 res_str = "MatchFound";
150 break;
151 case MatchNotFound:
152 res_str = "MatchNotFound";
153 break;
154 case NoSANPresent:
155 res_str = "NoSANPresent";
156 break;
157 case MalformedCertificate:
158 res_str = "MalformedCertificate";
159 break;
160 case Error:
161 res_str = "Error";
162 break;
163 default:
164 res_str = "WTF!";
165 break;
166 }
167 }
168
169 X509_NAME_oneline(X509_get_subject_name (server_cert),
170 cert_str, sizeof (cert_str));
171
172 if (res == MatchFound) {
173 printf("https server '%s' has this certificate, "
174 "which looks good to me:\n%s\n",
175 host, cert_str);
176 return 1;
177 } else {
178 printf("Got '%s' for hostname '%s' and certificate:\n%s\n",
179 res_str, host, cert_str);
180 return 0;
181 }
182 }
183
184 #ifdef _WIN32
185 static int
add_cert_for_store(X509_STORE * store,const char * name)186 add_cert_for_store(X509_STORE *store, const char *name)
187 {
188 HCERTSTORE sys_store = NULL;
189 PCCERT_CONTEXT ctx = NULL;
190 int r = 0;
191
192 sys_store = CertOpenSystemStore(0, name);
193 if (!sys_store) {
194 err("failed to open system certificate store");
195 return -1;
196 }
197 while ((ctx = CertEnumCertificatesInStore(sys_store, ctx))) {
198 X509 *x509 = d2i_X509(NULL, (unsigned char const **)&ctx->pbCertEncoded,
199 ctx->cbCertEncoded);
200 if (x509) {
201 X509_STORE_add_cert(store, x509);
202 X509_free(x509);
203 } else {
204 r = -1;
205 err_openssl("d2i_X509");
206 break;
207 }
208 }
209 CertCloseStore(sys_store, 0);
210 return r;
211 }
212 #endif
213
214 int
main(int argc,char ** argv)215 main(int argc, char **argv)
216 {
217 int r;
218 struct event_base *base = NULL;
219 struct evhttp_uri *http_uri = NULL;
220 const char *url = NULL, *data_file = NULL;
221 const char *crt = NULL;
222 const char *scheme, *host, *path, *query;
223 char uri[256];
224 int port;
225 int retries = 0;
226 int timeout = -1;
227
228 SSL_CTX *ssl_ctx = NULL;
229 SSL *ssl = NULL;
230 struct bufferevent *bev;
231 struct evhttp_connection *evcon = NULL;
232 struct evhttp_request *req;
233 struct evkeyvalq *output_headers;
234 struct evbuffer *output_buffer;
235
236 int i;
237 int ret = 0;
238 enum { HTTP, HTTPS } type = HTTP;
239
240 for (i = 1; i < argc; i++) {
241 if (!strcmp("-url", argv[i])) {
242 if (i < argc - 1) {
243 url = argv[i + 1];
244 } else {
245 syntax();
246 goto error;
247 }
248 } else if (!strcmp("-crt", argv[i])) {
249 if (i < argc - 1) {
250 crt = argv[i + 1];
251 } else {
252 syntax();
253 goto error;
254 }
255 } else if (!strcmp("-ignore-cert", argv[i])) {
256 ignore_cert = 1;
257 } else if (!strcmp("-data", argv[i])) {
258 if (i < argc - 1) {
259 data_file = argv[i + 1];
260 } else {
261 syntax();
262 goto error;
263 }
264 } else if (!strcmp("-retries", argv[i])) {
265 if (i < argc - 1) {
266 retries = atoi(argv[i + 1]);
267 } else {
268 syntax();
269 goto error;
270 }
271 } else if (!strcmp("-timeout", argv[i])) {
272 if (i < argc - 1) {
273 timeout = atoi(argv[i + 1]);
274 } else {
275 syntax();
276 goto error;
277 }
278 } else if (!strcmp("-help", argv[i])) {
279 syntax();
280 goto error;
281 }
282 }
283
284 if (!url) {
285 syntax();
286 goto error;
287 }
288
289 #ifdef _WIN32
290 {
291 WORD wVersionRequested;
292 WSADATA wsaData;
293 int err;
294
295 wVersionRequested = MAKEWORD(2, 2);
296
297 err = WSAStartup(wVersionRequested, &wsaData);
298 if (err != 0) {
299 printf("WSAStartup failed with error: %d\n", err);
300 goto error;
301 }
302 }
303 #endif // _WIN32
304
305 http_uri = evhttp_uri_parse(url);
306 if (http_uri == NULL) {
307 err("malformed url");
308 goto error;
309 }
310
311 scheme = evhttp_uri_get_scheme(http_uri);
312 if (scheme == NULL || (strcasecmp(scheme, "https") != 0 &&
313 strcasecmp(scheme, "http") != 0)) {
314 err("url must be http or https");
315 goto error;
316 }
317
318 host = evhttp_uri_get_host(http_uri);
319 if (host == NULL) {
320 err("url must have a host");
321 goto error;
322 }
323
324 port = evhttp_uri_get_port(http_uri);
325 if (port == -1) {
326 port = (strcasecmp(scheme, "http") == 0) ? 80 : 443;
327 }
328
329 path = evhttp_uri_get_path(http_uri);
330 if (strlen(path) == 0) {
331 path = "/";
332 }
333
334 query = evhttp_uri_get_query(http_uri);
335 if (query == NULL) {
336 snprintf(uri, sizeof(uri) - 1, "%s", path);
337 } else {
338 snprintf(uri, sizeof(uri) - 1, "%s?%s", path, query);
339 }
340 uri[sizeof(uri) - 1] = '\0';
341
342 #if (OPENSSL_VERSION_NUMBER < 0x10100000L) || \
343 (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x20700000L)
344 // Initialize OpenSSL
345 SSL_library_init();
346 ERR_load_crypto_strings();
347 SSL_load_error_strings();
348 OpenSSL_add_all_algorithms();
349 #endif
350
351 /* This isn't strictly necessary... OpenSSL performs RAND_poll
352 * automatically on first use of random number generator. */
353 r = RAND_poll();
354 if (r == 0) {
355 err_openssl("RAND_poll");
356 goto error;
357 }
358
359 /* Create a new OpenSSL context */
360 ssl_ctx = SSL_CTX_new(SSLv23_method());
361 if (!ssl_ctx) {
362 err_openssl("SSL_CTX_new");
363 goto error;
364 }
365
366 if (crt == NULL) {
367 X509_STORE *store;
368 /* Attempt to use the system's trusted root certificates. */
369 store = SSL_CTX_get_cert_store(ssl_ctx);
370 #ifdef _WIN32
371 if (add_cert_for_store(store, "CA") < 0 ||
372 add_cert_for_store(store, "AuthRoot") < 0 ||
373 add_cert_for_store(store, "ROOT") < 0) {
374 goto error;
375 }
376 #else // _WIN32
377 if (X509_STORE_set_default_paths(store) != 1) {
378 err_openssl("X509_STORE_set_default_paths");
379 goto error;
380 }
381 #endif // _WIN32
382 } else {
383 if (SSL_CTX_load_verify_locations(ssl_ctx, crt, NULL) != 1) {
384 err_openssl("SSL_CTX_load_verify_locations");
385 goto error;
386 }
387 }
388 /* Ask OpenSSL to verify the server certificate. Note that this
389 * does NOT include verifying that the hostname is correct.
390 * So, by itself, this means anyone with any legitimate
391 * CA-issued certificate for any website, can impersonate any
392 * other website in the world. This is not good. See "The
393 * Most Dangerous Code in the World" article at
394 * https://crypto.stanford.edu/~dabo/pubs/abstracts/ssl-client-bugs.html
395 */
396 SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER, NULL);
397 /* This is how we solve the problem mentioned in the previous
398 * comment. We "wrap" OpenSSL's validation routine in our
399 * own routine, which also validates the hostname by calling
400 * the code provided by iSECPartners. Note that even though
401 * the "Everything You've Always Wanted to Know About
402 * Certificate Validation With OpenSSL (But Were Afraid to
403 * Ask)" paper from iSECPartners says very explicitly not to
404 * call SSL_CTX_set_cert_verify_callback (at the bottom of
405 * page 2), what we're doing here is safe because our
406 * cert_verify_callback() calls X509_verify_cert(), which is
407 * OpenSSL's built-in routine which would have been called if
408 * we hadn't set the callback. Therefore, we're just
409 * "wrapping" OpenSSL's routine, not replacing it. */
410 SSL_CTX_set_cert_verify_callback(ssl_ctx, cert_verify_callback,
411 (void *) host);
412
413 // Create event base
414 base = event_base_new();
415 if (!base) {
416 perror("event_base_new()");
417 goto error;
418 }
419
420 // Create OpenSSL bufferevent and stack evhttp on top of it
421 ssl = SSL_new(ssl_ctx);
422 if (ssl == NULL) {
423 err_openssl("SSL_new()");
424 goto error;
425 }
426
427 #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
428 // Set hostname for SNI extension
429 SSL_set_tlsext_host_name(ssl, host);
430 #endif
431
432 if (strcasecmp(scheme, "http") == 0) {
433 bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE);
434 } else {
435 type = HTTPS;
436 bev = bufferevent_openssl_socket_new(base, -1, ssl,
437 BUFFEREVENT_SSL_CONNECTING,
438 BEV_OPT_CLOSE_ON_FREE|BEV_OPT_DEFER_CALLBACKS);
439 }
440
441 if (bev == NULL) {
442 fprintf(stderr, "bufferevent_openssl_socket_new() failed\n");
443 goto error;
444 }
445
446 bufferevent_openssl_set_allow_dirty_shutdown(bev, 1);
447
448 // For simplicity, we let DNS resolution block. Everything else should be
449 // asynchronous though.
450 evcon = evhttp_connection_base_bufferevent_new(base, NULL, bev,
451 host, port);
452 if (evcon == NULL) {
453 fprintf(stderr, "evhttp_connection_base_bufferevent_new() failed\n");
454 goto error;
455 }
456
457 if (retries > 0) {
458 evhttp_connection_set_retries(evcon, retries);
459 }
460 if (timeout >= 0) {
461 evhttp_connection_set_timeout(evcon, timeout);
462 }
463
464 // Fire off the request
465 req = evhttp_request_new(http_request_done, bev);
466 if (req == NULL) {
467 fprintf(stderr, "evhttp_request_new() failed\n");
468 goto error;
469 }
470
471 output_headers = evhttp_request_get_output_headers(req);
472 evhttp_add_header(output_headers, "Host", host);
473 evhttp_add_header(output_headers, "Connection", "close");
474
475 if (data_file) {
476 /* NOTE: In production code, you'd probably want to use
477 * evbuffer_add_file() or evbuffer_add_file_segment(), to
478 * avoid needless copying. */
479 FILE * f = fopen(data_file, "rb");
480 char buf[1024];
481 size_t s;
482 size_t bytes = 0;
483
484 if (!f) {
485 syntax();
486 goto error;
487 }
488
489 output_buffer = evhttp_request_get_output_buffer(req);
490 while ((s = fread(buf, 1, sizeof(buf), f)) > 0) {
491 evbuffer_add(output_buffer, buf, s);
492 bytes += s;
493 }
494 evutil_snprintf(buf, sizeof(buf)-1, "%lu", (unsigned long)bytes);
495 evhttp_add_header(output_headers, "Content-Length", buf);
496 fclose(f);
497 }
498
499 r = evhttp_make_request(evcon, req, data_file ? EVHTTP_REQ_POST : EVHTTP_REQ_GET, uri);
500 if (r != 0) {
501 fprintf(stderr, "evhttp_make_request() failed\n");
502 goto error;
503 }
504
505 event_base_dispatch(base);
506 goto cleanup;
507
508 error:
509 ret = 1;
510 cleanup:
511 if (evcon)
512 evhttp_connection_free(evcon);
513 if (http_uri)
514 evhttp_uri_free(http_uri);
515 if (base)
516 event_base_free(base);
517
518 if (ssl_ctx)
519 SSL_CTX_free(ssl_ctx);
520 if (type == HTTP && ssl)
521 SSL_free(ssl);
522 #if (OPENSSL_VERSION_NUMBER < 0x10100000L) || \
523 (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x20700000L)
524 EVP_cleanup();
525 ERR_free_strings();
526
527 #if OPENSSL_VERSION_NUMBER < 0x10000000L
528 ERR_remove_state(0);
529 #else
530 ERR_remove_thread_state(NULL);
531 #endif
532
533 CRYPTO_cleanup_all_ex_data();
534
535 sk_SSL_COMP_free(SSL_COMP_get_compression_methods());
536 #endif /* (OPENSSL_VERSION_NUMBER < 0x10100000L) || \
537 (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x20700000L) */
538
539 #ifdef _WIN32
540 WSACleanup();
541 #endif
542
543 return ret;
544 }
545