/* $NetBSD: https-client.c,v 1.1.1.1 2017/01/31 21:14:53 christos Exp $ */ /* This is an example of how to hook up evhttp with bufferevent_ssl It just GETs an https URL given on the command-line and prints the response body to stdout. Actually, it also accepts plain http URLs to make it easy to compare http vs https code paths. Loosely based on le-proxy.c. */ // Get rid of OSX 10.7 and greater deprecation warnings. #if defined(__APPLE__) && defined(__clang__) #pragma clang diagnostic ignored "-Wdeprecated-declarations" #endif #include #include #include #include #include #ifdef _WIN32 #include #include #define snprintf _snprintf #define strcasecmp _stricmp #else #include #include #endif #include #include #include #include #include #include #include #include #include #include "openssl_hostname_validation.h" static struct event_base *base; static int ignore_cert = 0; static void http_request_done(struct evhttp_request *req, void *ctx) { char buffer[256]; int nread; if (req == NULL) { /* If req is NULL, it means an error occurred, but * sadly we are mostly left guessing what the error * might have been. We'll do our best... */ struct bufferevent *bev = (struct bufferevent *) ctx; unsigned long oslerr; int printed_err = 0; int errcode = EVUTIL_SOCKET_ERROR(); fprintf(stderr, "some request failed - no idea which one though!\n"); /* Print out the OpenSSL error queue that libevent * squirreled away for us, if any. */ while ((oslerr = bufferevent_get_openssl_error(bev))) { ERR_error_string_n(oslerr, buffer, sizeof(buffer)); fprintf(stderr, "%s\n", buffer); printed_err = 1; } /* If the OpenSSL error queue was empty, maybe it was a * socket error; let's try printing that. */ if (! printed_err) fprintf(stderr, "socket error = %s (%d)\n", evutil_socket_error_to_string(errcode), errcode); return; } fprintf(stderr, "Response line: %d %s\n", evhttp_request_get_response_code(req), evhttp_request_get_response_code_line(req)); while ((nread = evbuffer_remove(evhttp_request_get_input_buffer(req), buffer, sizeof(buffer))) > 0) { /* These are just arbitrary chunks of 256 bytes. * They are not lines, so we can't treat them as such. */ fwrite(buffer, nread, 1, stdout); } } static void syntax(void) { fputs("Syntax:\n", stderr); fputs(" https-client -url [-data data-file.bin] [-ignore-cert] [-retries num] [-timeout sec] [-crt crt]\n", stderr); fputs("Example:\n", stderr); fputs(" https-client -url https://ip.appspot.com/\n", stderr); } static void err(const char *msg) { fputs(msg, stderr); } static void err_openssl(const char *func) { fprintf (stderr, "%s failed:\n", func); /* This is the OpenSSL function that prints the contents of the * error stack to the specified file handle. */ ERR_print_errors_fp (stderr); exit(1); } #ifndef _WIN32 /* See http://archives.seul.org/libevent/users/Jan-2013/msg00039.html */ static int cert_verify_callback(X509_STORE_CTX *x509_ctx, void *arg) { char cert_str[256]; const char *host = (const char *) arg; const char *res_str = "X509_verify_cert failed"; HostnameValidationResult res = Error; /* This is the function that OpenSSL would call if we hadn't called * SSL_CTX_set_cert_verify_callback(). Therefore, we are "wrapping" * the default functionality, rather than replacing it. */ int ok_so_far = 0; X509 *server_cert = NULL; if (ignore_cert) { return 1; } ok_so_far = X509_verify_cert(x509_ctx); server_cert = X509_STORE_CTX_get_current_cert(x509_ctx); if (ok_so_far) { res = validate_hostname(host, server_cert); switch (res) { case MatchFound: res_str = "MatchFound"; break; case MatchNotFound: res_str = "MatchNotFound"; break; case NoSANPresent: res_str = "NoSANPresent"; break; case MalformedCertificate: res_str = "MalformedCertificate"; break; case Error: res_str = "Error"; break; default: res_str = "WTF!"; break; } } X509_NAME_oneline(X509_get_subject_name (server_cert), cert_str, sizeof (cert_str)); if (res == MatchFound) { printf("https server '%s' has this certificate, " "which looks good to me:\n%s\n", host, cert_str); return 1; } else { printf("Got '%s' for hostname '%s' and certificate:\n%s\n", res_str, host, cert_str); return 0; } } #endif int main(int argc, char **argv) { int r; struct evhttp_uri *http_uri = NULL; const char *url = NULL, *data_file = NULL; const char *crt = "/etc/ssl/certs/ca-certificates.crt"; const char *scheme, *host, *path, *query; char uri[256]; int port; int retries = 0; int timeout = -1; SSL_CTX *ssl_ctx = NULL; SSL *ssl = NULL; struct bufferevent *bev; struct evhttp_connection *evcon = NULL; struct evhttp_request *req; struct evkeyvalq *output_headers; struct evbuffer *output_buffer; int i; int ret = 0; enum { HTTP, HTTPS } type = HTTP; for (i = 1; i < argc; i++) { if (!strcmp("-url", argv[i])) { if (i < argc - 1) { url = argv[i + 1]; } else { syntax(); goto error; } } else if (!strcmp("-crt", argv[i])) { if (i < argc - 1) { crt = argv[i + 1]; } else { syntax(); goto error; } } else if (!strcmp("-ignore-cert", argv[i])) { ignore_cert = 1; } else if (!strcmp("-data", argv[i])) { if (i < argc - 1) { data_file = argv[i + 1]; } else { syntax(); goto error; } } else if (!strcmp("-retries", argv[i])) { if (i < argc - 1) { retries = atoi(argv[i + 1]); } else { syntax(); goto error; } } else if (!strcmp("-timeout", argv[i])) { if (i < argc - 1) { timeout = atoi(argv[i + 1]); } else { syntax(); goto error; } } else if (!strcmp("-help", argv[i])) { syntax(); goto error; } } if (!url) { syntax(); goto error; } #ifdef _WIN32 { WORD wVersionRequested; WSADATA wsaData; int err; wVersionRequested = MAKEWORD(2, 2); err = WSAStartup(wVersionRequested, &wsaData); if (err != 0) { printf("WSAStartup failed with error: %d\n", err); goto error; } } #endif // _WIN32 http_uri = evhttp_uri_parse(url); if (http_uri == NULL) { err("malformed url"); goto error; } scheme = evhttp_uri_get_scheme(http_uri); if (scheme == NULL || (strcasecmp(scheme, "https") != 0 && strcasecmp(scheme, "http") != 0)) { err("url must be http or https"); goto error; } host = evhttp_uri_get_host(http_uri); if (host == NULL) { err("url must have a host"); goto error; } port = evhttp_uri_get_port(http_uri); if (port == -1) { port = (strcasecmp(scheme, "http") == 0) ? 80 : 443; } path = evhttp_uri_get_path(http_uri); if (strlen(path) == 0) { path = "/"; } query = evhttp_uri_get_query(http_uri); if (query == NULL) { snprintf(uri, sizeof(uri) - 1, "%s", path); } else { snprintf(uri, sizeof(uri) - 1, "%s?%s", path, query); } uri[sizeof(uri) - 1] = '\0'; #if OPENSSL_VERSION_NUMBER < 0x10100000L // Initialize OpenSSL SSL_library_init(); ERR_load_crypto_strings(); SSL_load_error_strings(); OpenSSL_add_all_algorithms(); #endif /* This isn't strictly necessary... OpenSSL performs RAND_poll * automatically on first use of random number generator. */ r = RAND_poll(); if (r == 0) { err_openssl("RAND_poll"); goto error; } /* Create a new OpenSSL context */ ssl_ctx = SSL_CTX_new(SSLv23_method()); if (!ssl_ctx) { err_openssl("SSL_CTX_new"); goto error; } #ifndef _WIN32 /* TODO: Add certificate loading on Windows as well */ /* Attempt to use the system's trusted root certificates. * (This path is only valid for Debian-based systems.) */ if (1 != SSL_CTX_load_verify_locations(ssl_ctx, crt, NULL)) { err_openssl("SSL_CTX_load_verify_locations"); goto error; } /* Ask OpenSSL to verify the server certificate. Note that this * does NOT include verifying that the hostname is correct. * So, by itself, this means anyone with any legitimate * CA-issued certificate for any website, can impersonate any * other website in the world. This is not good. See "The * Most Dangerous Code in the World" article at * https://crypto.stanford.edu/~dabo/pubs/abstracts/ssl-client-bugs.html */ SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER, NULL); /* This is how we solve the problem mentioned in the previous * comment. We "wrap" OpenSSL's validation routine in our * own routine, which also validates the hostname by calling * the code provided by iSECPartners. Note that even though * the "Everything You've Always Wanted to Know About * Certificate Validation With OpenSSL (But Were Afraid to * Ask)" paper from iSECPartners says very explicitly not to * call SSL_CTX_set_cert_verify_callback (at the bottom of * page 2), what we're doing here is safe because our * cert_verify_callback() calls X509_verify_cert(), which is * OpenSSL's built-in routine which would have been called if * we hadn't set the callback. Therefore, we're just * "wrapping" OpenSSL's routine, not replacing it. */ SSL_CTX_set_cert_verify_callback(ssl_ctx, cert_verify_callback, (void *) host); #else // _WIN32 (void)crt; #endif // _WIN32 // Create event base base = event_base_new(); if (!base) { perror("event_base_new()"); goto error; } // Create OpenSSL bufferevent and stack evhttp on top of it ssl = SSL_new(ssl_ctx); if (ssl == NULL) { err_openssl("SSL_new()"); goto error; } #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME // Set hostname for SNI extension SSL_set_tlsext_host_name(ssl, host); #endif if (strcasecmp(scheme, "http") == 0) { bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE); } else { type = HTTPS; bev = bufferevent_openssl_socket_new(base, -1, ssl, BUFFEREVENT_SSL_CONNECTING, BEV_OPT_CLOSE_ON_FREE|BEV_OPT_DEFER_CALLBACKS); } if (bev == NULL) { fprintf(stderr, "bufferevent_openssl_socket_new() failed\n"); goto error; } bufferevent_openssl_set_allow_dirty_shutdown(bev, 1); // For simplicity, we let DNS resolution block. Everything else should be // asynchronous though. evcon = evhttp_connection_base_bufferevent_new(base, NULL, bev, host, port); if (evcon == NULL) { fprintf(stderr, "evhttp_connection_base_bufferevent_new() failed\n"); goto error; } if (retries > 0) { evhttp_connection_set_retries(evcon, retries); } if (timeout >= 0) { evhttp_connection_set_timeout(evcon, timeout); } // Fire off the request req = evhttp_request_new(http_request_done, bev); if (req == NULL) { fprintf(stderr, "evhttp_request_new() failed\n"); goto error; } output_headers = evhttp_request_get_output_headers(req); evhttp_add_header(output_headers, "Host", host); evhttp_add_header(output_headers, "Connection", "close"); if (data_file) { /* NOTE: In production code, you'd probably want to use * evbuffer_add_file() or evbuffer_add_file_segment(), to * avoid needless copying. */ FILE * f = fopen(data_file, "rb"); char buf[1024]; size_t s; size_t bytes = 0; if (!f) { syntax(); goto error; } output_buffer = evhttp_request_get_output_buffer(req); while ((s = fread(buf, 1, sizeof(buf), f)) > 0) { evbuffer_add(output_buffer, buf, s); bytes += s; } evutil_snprintf(buf, sizeof(buf)-1, "%lu", (unsigned long)bytes); evhttp_add_header(output_headers, "Content-Length", buf); fclose(f); } r = evhttp_make_request(evcon, req, data_file ? EVHTTP_REQ_POST : EVHTTP_REQ_GET, uri); if (r != 0) { fprintf(stderr, "evhttp_make_request() failed\n"); goto error; } event_base_dispatch(base); goto cleanup; error: ret = 1; cleanup: if (evcon) evhttp_connection_free(evcon); if (http_uri) evhttp_uri_free(http_uri); event_base_free(base); if (ssl_ctx) SSL_CTX_free(ssl_ctx); if (type == HTTP && ssl) SSL_free(ssl); #if OPENSSL_VERSION_NUMBER < 0x10100000L EVP_cleanup(); ERR_free_strings(); #ifdef EVENT__HAVE_ERR_REMOVE_THREAD_STATE ERR_remove_thread_state(NULL); #else ERR_remove_state(0); #endif CRYPTO_cleanup_all_ex_data(); sk_SSL_COMP_free(SSL_COMP_get_compression_methods()); #endif /*OPENSSL_VERSION_NUMBER < 0x10100000L */ #ifdef _WIN32 WSACleanup(); #endif return ret; }