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1 /*
2  * Handle connections.
3  *
4  * Copyright (C) 2011-2013  Simon Ruderich
5  *
6  * This program is free software: you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation, either version 3 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
18  */
19
20 #include "tlsproxy.h"
21 #include "connection.h"
22 #include "verify.h"
23
24 #include <assert.h>
25 #include <errno.h>
26 #include <limits.h>
27 #include <netdb.h>
28 #include <poll.h>
29 #include <unistd.h>
30
31
32 /* Maximum length of a HTTP request line. Longer request lines are aborted
33  * with an error. The standard doesn't specify a maximum line length but this
34  * should be a good limit to make processing simpler. As HTTPS is used this
35  * doesn't limit long GET requests. */
36 #define MAX_REQUEST_LINE 4096
37
38 /* Format string used to send HTTP/1.0 error responses to the client.
39  *
40  * %s is used 5 times, first is the error code, then additional headers, next
41  * two are the error code (no %n$s!), the last is the message. */
42 #define HTTP_RESPONSE_FORMAT "HTTP/1.0 %s\r\n\
43 Content-Type: text/html; charset=US-ASCII\r\n\
44 %s\r\n\
45 <!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">\n\
46 <html>\n\
47 <head><title>%s</title></head>\n\
48 <body>\n\
49 <h1>%s</h1>\n\
50 <p>%s</p>\n\
51 </body>\n\
52 </html>\n"
53
54
55 static int initialize_tls_session_client(int peer_socket,
56         const char *hostname,
57         gnutls_session_t *session,
58         gnutls_certificate_credentials_t *x509_cred);
59 static int initialize_tls_session_server(int peer_socket,
60         gnutls_session_t *session,
61         gnutls_certificate_credentials_t *x509_cred);
62 static int initialize_tls_session_both(int flags,
63         int peer_socket,
64         gnutls_session_t *session,
65         gnutls_certificate_credentials_t *x509_cred);
66
67 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd);
68 static int read_http_request(FILE *client_fd, char *request, size_t length);
69 static void send_bad_request(FILE *client_fd);
70 static void send_authentication_required(FILE *client_fd);
71 static void send_forwarding_failure(FILE *client_fd);
72 static void tls_send_invalid_cert_message(gnutls_session_t session);
73
74 static void transfer_data(int client, int server);
75 static int read_from_write_to(int from, int to);
76 static void transfer_data_tls(int client, int server,
77                               gnutls_session_t client_session,
78                               gnutls_session_t server_session);
79 static int read_from_write_to_tls(gnutls_session_t from, gnutls_session_t to,
80                                   size_t buffer_size);
81
82 static int connect_to_host(const char *hostname, const char *port);
83
84 static int parse_request(const char *buffer, char *host, char *port,
85                                              int *version_minor);
86
87
88 void handle_connection(int client_socket) {
89     int server_socket;
90     FILE *client_fd_read, *client_fd_write, *server_fd_read, *server_fd_write;
91
92     char buffer[MAX_REQUEST_LINE];
93     char host[MAX_REQUEST_LINE];
94     char port[5 + 1];
95
96     int version_minor; /* x in HTTP/1.x */
97     int result;
98
99     /* client_x509_cred is used when talking to the client (acting as a TSL
100      * server), server_x509_cred is used when talking to the server (acting as
101      * a TSL client). */
102     gnutls_certificate_credentials_t client_x509_cred, server_x509_cred;
103
104     gnutls_session_t client_session, server_session;
105     /* initialize_tls_session_*() called? - used for goto out */
106     int client_session_init, server_session_init;
107     /* gnutls_handshake() called? - used for goto out */
108     int client_session_started, server_session_started;
109     /* Validation failed? If yes we need to send the special "invalid"
110      * certificate. */
111     int validation_failed;
112
113     LOG(DEBUG1, "new connection");
114
115     server_socket = -1;
116     client_fd_read = NULL;
117     client_fd_write = NULL;
118     server_fd_read = NULL;
119     server_fd_write = NULL;
120     client_session_init = 0;
121     server_session_init = 0;
122     client_session_started = 0;
123     server_session_started = 0;
124     validation_failed = 0;
125
126     if (fdopen_read_write(client_socket, &client_fd_read,
127                                          &client_fd_write) != 0) {
128         goto out;
129     }
130
131     /* Read request line (CONNECT ..) and headers (they are discarded). */
132     result = read_http_request(client_fd_read, buffer, sizeof(buffer));
133     if (result == -1) {
134         LOG(WARNING, "read_http_request(): client read error");
135         goto out;
136     } else if (result == -2) {
137         LOG(WARNING, "read_http_request(): client EOF");
138         send_bad_request(client_fd_write);
139         goto out;
140     } else if (result == -3) {
141         LOG(DEBUG1, "read_http_request(): proxy authentication failed");
142         send_authentication_required(client_fd_write);
143         goto out;
144     }
145
146     if (parse_request(buffer, host, port, &version_minor) != 0) {
147         LOG(WARNING, "bad request: >%s<", buffer);
148         send_bad_request(client_fd_write);
149         goto out;
150     }
151
152     LOG(DEBUG1, "target: %s:%s (HTTP 1.%d)", host, port, version_minor);
153
154     /* Connect to proxy server or directly to server. */
155     if (global_proxy_host != NULL && global_proxy_port != NULL) {
156         LOG(DEBUG1, "connecting to %s:%s", global_proxy_host,
157                                            global_proxy_port);
158         server_socket = connect_to_host(global_proxy_host, global_proxy_port);
159     } else {
160         LOG(DEBUG1, "connecting to %s:%s", host, port);
161         server_socket = connect_to_host(host, port);
162     }
163
164     if (server_socket < 0) {
165         LOG(WARNING, "failed to connect to server");
166         send_forwarding_failure(client_fd_write);
167         goto out;
168     }
169     if (fdopen_read_write(server_socket, &server_fd_read,
170                                          &server_fd_write) != 0) {
171         send_forwarding_failure(client_fd_write);
172         goto out;
173     }
174
175     /* Connect to proxy if requested (command line option). */
176     if (global_proxy_host != NULL && global_proxy_port != NULL) {
177         fprintf(server_fd_write, "CONNECT %s:%s HTTP/1.0\r\n", host, port);
178         fprintf(server_fd_write, "\r\n");
179         fflush(server_fd_write);
180
181         /* Read response line from proxy server. */
182         result = read_http_request(server_fd_read, buffer, sizeof(buffer));
183         if (result == -1) {
184             LOG(WARNING, "read_http_request(): proxy read error");
185             send_forwarding_failure(client_fd_write);
186             goto out;
187         } else if (result == -2) {
188             LOG(WARNING, "read_http_request(): proxy EOF");
189             send_forwarding_failure(client_fd_write);
190             goto out;
191         }
192
193         /* Check response of proxy server. */
194         if (strncmp(buffer, "HTTP/1.0 200", 12)) {
195             LOG(WARNING, "bad proxy response: %s", buffer);
196             send_forwarding_failure(client_fd_write);
197             goto out;
198         }
199     }
200
201     LOG(DEBUG1, "connection to server established");
202
203     /* If the -u option is used and we don't know this hostname's server
204      * certificate then just pass through the connection and let the client
205      * verify the server certificate. */
206     if (global_passthrough_unknown) {
207         char path[TLSPROXY_MAX_PATH_LENGTH];
208         FILE *file = NULL;
209
210         if (server_certificate_file(&file, host, path, sizeof(path)) == -2) {
211             /* We've established a connection, tell the client. */
212             fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
213             fprintf(client_fd_write, "\r\n");
214             fflush(client_fd_write);
215
216             LOG(DEBUG1, "transferring data");
217
218             /* Proxy data between client and server until one side is done
219              * (EOF or error). */
220             transfer_data(client_socket, server_socket);
221
222             LOG(DEBUG1, "finished transferring data");
223
224             goto out;
225         }
226         /* server_certificate_file() may have opened the file, close it. */
227         if (file != NULL) {
228             fclose(file);
229         }
230     }
231
232     /* Initialize TLS client credentials to talk to the server. */
233     result = initialize_tls_session_server(server_socket, &server_session,
234                                                           &server_x509_cred);
235     if (result != 0) {
236         LOG(WARNING, "initialize_tls_session_server() failed");
237         send_forwarding_failure(client_fd_write);
238         goto out;
239     }
240     server_session_init = 1;
241
242     LOG(DEBUG1, "starting server TLS handshake");
243
244     /* Try to establish TLS handshake between us and server. */
245     result = gnutls_handshake(server_session);
246     if (result != GNUTLS_E_SUCCESS) {
247         LOG(WARNING, "server TLS handshake failed: %s",
248                      gnutls_strerror(result));
249         send_forwarding_failure(client_fd_write);
250         goto out;
251     }
252     server_session_started = 1;
253
254     LOG(DEBUG1, "server TLS handshake finished");
255
256     /* Make sure the server certificate is valid and known. */
257     if (verify_tls_connection(server_session, host) != 0) {
258         LOG(ERROR, "server certificate validation failed!");
259         /* We'll send the error message over our TLS connection to the client,
260          * but with an invalid certificate. No data is transfered from/to the
261          * target server. */
262         validation_failed = 1;
263     }
264
265     /* Initialize TLS server credentials to talk to the client. */
266     result = initialize_tls_session_client(client_socket,
267                                            /* use a special host if the server
268                                             * certificate was invalid */
269                                            (validation_failed) ? "invalid"
270                                                                : host,
271                                            &client_session,
272                                            &client_x509_cred);
273     if (result != 0) {
274         LOG(WARNING, "initialize_tls_session_client() failed");
275         send_forwarding_failure(client_fd_write);
276         goto out;
277     }
278     client_session_init = 1;
279
280     /* We've established a connection, tell the client. */
281     fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
282     fprintf(client_fd_write, "\r\n");
283     fflush(client_fd_write);
284
285     LOG(DEBUG1, "starting client TLS handshake");
286
287     /* Try to establish TLS handshake between client and us. */
288     result = gnutls_handshake(client_session);
289     if (result != GNUTLS_E_SUCCESS) {
290         LOG(WARNING, "client TLS handshake failed: %s",
291                      gnutls_strerror(result));
292         send_forwarding_failure(client_fd_write);
293         goto out;
294     }
295     client_session_started = 1;
296
297     LOG(DEBUG1, "client TLS handshake finished");
298
299     /* Tell the client that the verification failed. Shouldn't be necessary as
300      * the client should terminate the connection because he received the
301      * invalid certificate but better be sure. */
302     if (validation_failed) {
303         tls_send_invalid_cert_message(client_session);
304         goto out;
305     }
306
307     LOG(DEBUG1, "transferring TLS data");
308
309     /* Proxy data between client and server until one side is done (EOF or
310      * error). */
311     transfer_data_tls(client_socket, server_socket,
312                       client_session, server_session);
313
314     LOG(DEBUG1, "finished transferring TLS data");
315
316 out:
317     /* Close TLS sessions if necessary. Use GNUTLS_SHUT_RDWR so the data is
318      * reliable transmitted. */
319     if (server_session_started) {
320         /* Recent gnutls-serv (used in the test-suite) won't terminate the
321          * connection when gnutls_bye(session, GNUTLS_SHUT_RDWR) is used
322          * before any other data was received. If the validation failed just
323          * close the connection without waiting for data, we won't read it
324          * anyway.
325          *
326          * For verified connections GNUTLS_SHUT_RDWR is important or we might
327          * lose data. */
328         gnutls_bye(server_session, validation_failed ? GNUTLS_SHUT_WR
329                                                      : GNUTLS_SHUT_RDWR);
330     }
331     if (client_session_started) {
332         gnutls_bye(client_session, GNUTLS_SHUT_RDWR);
333     }
334     if (server_session_init) {
335         gnutls_deinit(server_session);
336         gnutls_certificate_free_credentials(server_x509_cred);
337     }
338     if (client_session_init) {
339         gnutls_deinit(client_session);
340         gnutls_certificate_free_cas(client_x509_cred);
341         gnutls_certificate_free_keys(client_x509_cred);
342         gnutls_certificate_free_credentials(client_x509_cred);
343     }
344
345     /* Close connection to server/proxy. */
346     if (server_fd_read != NULL) {
347         if (server_fd_write != NULL) {
348             fclose(server_fd_write);
349         }
350         fclose(server_fd_read);
351     } else if (server_socket != -1) {
352         close(server_socket);
353     }
354     LOG(DEBUG1, "connection to server closed");
355     /* Close connection to client. */
356     if (client_fd_read != NULL) {
357         if (client_fd_write != NULL) {
358             fclose(client_fd_write);
359         }
360         fclose(client_fd_read);
361     } else {
362         close(client_socket);
363     }
364     LOG(DEBUG1, "connection to client closed");
365
366     LOG(DEBUG1, "connection finished");
367 }
368
369
370 static int initialize_tls_session_client(int peer_socket,
371         const char *hostname,
372         gnutls_session_t *session,
373         gnutls_certificate_credentials_t *x509_cred) {
374     int result;
375     int use_invalid_cert;
376     char path[TLSPROXY_MAX_PATH_LENGTH];
377
378     /* The "invalid" hostname is special. If it's used we send an invalid
379      * certificate to let the client know something is wrong. */
380     use_invalid_cert = (!strcmp(hostname, "invalid"));
381
382     if (proxy_certificate_path(hostname, path, sizeof(path)) != 0) {
383         LOG(ERROR,
384             "initialize_tls_session_client(): "
385             "failed to get proxy certificate path");
386         return -1;
387     }
388
389     result = gnutls_certificate_allocate_credentials(x509_cred);
390     if (result != GNUTLS_E_SUCCESS) {
391         LOG(ERROR,
392             "initialize_tls_session_client(): "
393             "gnutls_certificate_allocate_credentials(): %s",
394             gnutls_strerror(result));
395         return -1;
396     }
397
398     /* Load proxy CA file, this CA "list" is send to the client. */
399     if (!use_invalid_cert) {
400         result = gnutls_certificate_set_x509_trust_file(*x509_cred,
401                                                         PROXY_CA_PATH,
402                                                         GNUTLS_X509_FMT_PEM);
403         if (result <= 0) {
404             LOG(ERROR,
405                 "initialize_tls_session_client(): can't read CA file: '%s'",
406                 PROXY_CA_PATH);
407             gnutls_certificate_free_credentials(*x509_cred);
408             return -1;
409         }
410     }
411     /* If the invalid hostname was specified do nothing, we use a self-signed
412      * certificate in this case. */
413
414     /* And certificate for this website and proxy's private key. */
415     if (!use_invalid_cert) {
416         result = gnutls_certificate_set_x509_key_file(*x509_cred,
417                                                       path,
418                                                       PROXY_KEY_PATH,
419                                                       GNUTLS_X509_FMT_PEM);
420     /* If the invalid hostname was specified load our special "invalid"
421      * certificate. */
422     } else {
423         result = gnutls_certificate_set_x509_key_file(*x509_cred,
424                                                       PROXY_INVALID_CERT_PATH,
425                                                       PROXY_KEY_PATH,
426                                                       GNUTLS_X509_FMT_PEM);
427     }
428     if (result != GNUTLS_E_SUCCESS) {
429         LOG(ERROR,
430             "initialize_tls_session_client(): "
431             "can't read server certificate ('%s') or key file ('%s'): %s",
432             path, PROXY_KEY_PATH, gnutls_strerror(result));
433         gnutls_certificate_free_credentials(*x509_cred);
434         /* Could be a missing certificate. */
435         return -2;
436     }
437
438     gnutls_certificate_set_dh_params(*x509_cred, global_tls_dh_params);
439
440     return initialize_tls_session_both(GNUTLS_SERVER,
441                                        peer_socket, session, x509_cred);
442 }
443 static int initialize_tls_session_server(int peer_socket,
444         gnutls_session_t *session,
445         gnutls_certificate_credentials_t *x509_cred) {
446     int result;
447
448     result = gnutls_certificate_allocate_credentials(x509_cred);
449     if (result != GNUTLS_E_SUCCESS) {
450         LOG(ERROR,
451             "initialize_tls_session_server(): "
452             "gnutls_certificate_allocate_credentials(): %s",
453             gnutls_strerror(result));
454         return -1;
455     }
456
457     return initialize_tls_session_both(GNUTLS_CLIENT,
458                                        peer_socket, session, x509_cred);
459 }
460 static int initialize_tls_session_both(int flags,
461         int peer_socket,
462         gnutls_session_t *session,
463         gnutls_certificate_credentials_t *x509_cred) {
464     int result;
465
466     *session = NULL;
467
468     result = gnutls_init(session, flags);
469     if (result != GNUTLS_E_SUCCESS) {
470         LOG(ERROR,
471             "initialize_tls_session_both(): gnutls_init(): %s",
472             gnutls_strerror(result));
473         goto err;
474     }
475     result = gnutls_priority_set(*session, global_tls_priority_cache);
476     if (result != GNUTLS_E_SUCCESS) {
477         LOG(ERROR,
478             "initialize_tls_session_both(): gnutls_priority_set(): %s",
479             gnutls_strerror(result));
480         goto err;
481     }
482     result = gnutls_credentials_set(*session,
483                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
484     if (result != GNUTLS_E_SUCCESS) {
485         LOG(ERROR,
486             "initialize_tls_session_both(): gnutls_credentials_set(): %s",
487             gnutls_strerror(result));
488         goto err;
489     }
490
491 #ifdef HAVE_GNUTLS_TRANSPORT_SET_INT2
492     /* gnutls_transport_set_int() is a macro. */
493     gnutls_transport_set_int(*session, peer_socket);
494 #else
495     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
496 #endif
497
498     return 0;
499
500 err:
501     if (*session) {
502         gnutls_deinit(*session);
503     }
504     gnutls_certificate_free_credentials(*x509_cred);
505     return -1;
506 }
507
508
509 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd) {
510     *read_fd = fdopen(socket, "r");
511     if (*read_fd == NULL) {
512         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"r\") failed");
513         return -1;
514     }
515
516     *write_fd = fdopen(dup(socket), "w");
517     if (*write_fd == NULL) {
518         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"w\") failed");
519         fclose(*read_fd);
520         *read_fd = NULL; /* "tell" caller read_fd is already closed */
521         return -1;
522     }
523
524     return 0;
525 }
526
527 /* Read HTTP request line and headers (ignored).
528  *
529  * On success 0 is returned, -1 on client error, -2 on unexpected EOF.
530  */
531 static int read_http_request(FILE *client_fd, char *request, size_t length) {
532     char buffer[MAX_REQUEST_LINE];
533     int found_proxy_authorization;
534
535     assert(length <= INT_MAX);
536     if (fgets(request, (int)length, client_fd) == NULL) {
537         if (ferror(client_fd)) {
538             LOG_PERROR(WARNING, "read_http_request(): fgets()");
539             return -1;
540         }
541         /* EOF */
542         return -2;
543     }
544
545     found_proxy_authorization = 0;
546     while (fgets(buffer, sizeof(buffer), client_fd) != NULL) {
547         const char *authentication = "Proxy-Authorization: Basic ";
548
549         if (global_http_digest_authorization != NULL
550                 && !strncmp(buffer, authentication, strlen(authentication))) {
551             found_proxy_authorization = 1;
552
553             /* Check if the passphrase matches. */
554             strtok(buffer, "\r\n");
555             if (strcmp(buffer + strlen(authentication),
556                        global_http_digest_authorization)) {
557                 return -3;
558             }
559         }
560
561         /* End of header. */
562         if (!strcmp(buffer, "\n") || !strcmp(buffer, "\r\n")) {
563             break;
564         }
565     }
566     if (ferror(client_fd)) {
567         LOG_PERROR(WARNING, "read_http_request(): fgets()");
568         return -1;
569     }
570
571     if (global_http_digest_authorization != NULL && !found_proxy_authorization) {
572         return -3;
573     }
574
575     return 0;
576 }
577
578 static void send_bad_request(FILE *client_fd) {
579     const char error[] = "400 Bad Request";
580     const char msg[]   = "Your browser sent an invalid request.";
581     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
582     fflush(client_fd);
583 }
584 static void send_authentication_required(FILE *client_fd) {
585     const char error[] = "407 Proxy Authentication Required";
586     const char auth[]  = "Proxy-Authenticate: Basic realm=\"tlsproxy\"\r\n";
587     const char msg[]   = "TODO";
588     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, auth, error, error, msg);
589     fflush(client_fd);
590 }
591 static void send_forwarding_failure(FILE *client_fd) {
592     const char error[] = "503 Forwarding failure";
593     const char msg[]   = "Failed to connect to server, check logs.";
594     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
595     fflush(client_fd);
596 }
597 static void tls_send_invalid_cert_message(gnutls_session_t session) {
598     const char error[] = "500 Internal Server Error";
599     const char msg[]   = "Server certificate validation failed, check logs.";
600
601     int result;
602     char buffer[sizeof(HTTP_RESPONSE_FORMAT)
603                 + 3 * sizeof(error) + sizeof(msg)];
604
605     result = snprintf(buffer, sizeof(buffer), HTTP_RESPONSE_FORMAT,
606                                               error, "", error, error, msg);
607     assert(result > 0 && (size_t)result < sizeof(buffer));
608
609     gnutls_record_send(session, buffer, strlen(buffer));
610 }
611
612
613 /* Transfer data between client and server sockets until one closes the
614  * connection. */
615 static void transfer_data(int client, int server) {
616     struct pollfd fds[2];
617     fds[0].fd      = client;
618     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
619     fds[0].revents = 0;
620     fds[1].fd      = server;
621     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
622     fds[1].revents = 0;
623
624     LOG(DEBUG1, "transfer_data(): %d -> %d", client, server);
625
626     for (;;) {
627         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
628         if (result < 0) {
629             LOG_PERROR(ERROR, "transfer_data(): poll()");
630             return;
631         }
632
633         /* Data available from client. */
634         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
635             if (read_from_write_to(client, server) != 0) {
636                 /* EOF (or other error) */
637                 break;
638             }
639         }
640         /* Data available from server. */
641         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
642             if (read_from_write_to(server, client) != 0) {
643                 /* EOF (or other error) */
644                 break;
645             }
646         }
647
648         /* Client closed connection. */
649         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
650             break;
651         }
652         /* Server closed connection. */
653         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
654             break;
655         }
656     }
657 }
658
659 /* Read available data from socket from and write it to socket to. At maximum
660  * 4096 bytes are read/written. */
661 static int read_from_write_to(int from, int to) {
662     ssize_t size_read;
663     ssize_t size_written;
664     char buffer[4096];
665
666     size_read = read(from, buffer, sizeof(buffer));
667     if (size_read < 0) {
668         LOG_PERROR(WARNING, "read_from_write_to(): read()");
669         return -1;
670     /* EOF */
671     } else if (size_read == 0) {
672         return -1;
673     }
674
675     size_written = write(to, buffer, (size_t)size_read);
676     if (size_written < 0) {
677         LOG_PERROR(WARNING, "read_from_write_to(): write()");
678         return -1;
679     }
680     if (size_read != size_written) {
681         LOG(ERROR, "read_from_write_to(): only written %ld of %ld bytes!",
682                    (long int)size_written, (long int)size_read);
683         return -1;
684     }
685
686     return 0;
687 }
688
689 /* Transfer data between client and server TLS connection until one closes the
690  * connection. */
691 static void transfer_data_tls(int client, int server,
692                               gnutls_session_t client_session,
693                               gnutls_session_t server_session) {
694     size_t buffer_size;
695
696     struct pollfd fds[2];
697     fds[0].fd      = client;
698     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
699     fds[0].revents = 0;
700     fds[1].fd      = server;
701     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
702     fds[1].revents = 0;
703
704     /* Get maximum possible buffer size. */
705     buffer_size = gnutls_record_get_max_size(client_session);
706     if (gnutls_record_get_max_size(server_session) < buffer_size) {
707         buffer_size = gnutls_record_get_max_size(server_session);
708     }
709     LOG(DEBUG1, "transfer_data_tls(): suggested buffer size: %ld",
710                 (long int)buffer_size);
711
712     for (;;) {
713         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
714         if (result < 0) {
715             LOG_PERROR(ERROR, "transfer_data(): poll()");
716             return;
717         }
718
719         /* Data available from client. */
720         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
721             if (read_from_write_to_tls(client_session, server_session,
722                                        buffer_size) != 0) {
723                 /* EOF (or other error) */
724                 break;
725             }
726         }
727         /* Data available from server. */
728         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
729             if (read_from_write_to_tls(server_session, client_session,
730                                        buffer_size) != 0) {
731                 /* EOF (or other error) */
732                 break;
733             }
734         }
735
736         /* Client closed connection. */
737         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
738             break;
739         }
740         /* Server closed connection. */
741         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
742             break;
743         }
744     }
745 }
746
747 /* Read available data from session from and write to session to. */
748 static int read_from_write_to_tls(gnutls_session_t from,
749                                   gnutls_session_t to,
750                                   size_t buffer_size) {
751     ssize_t size_read;
752     ssize_t size_written;
753     char buffer[16384];
754
755     if (buffer_size > sizeof(buffer)) {
756         LOG(WARNING, "read_from_write_to_tls(): reduced buffer size to %ld",
757                      (long int)(sizeof(buffer)));
758         buffer_size = sizeof(buffer);
759     }
760
761     size_read = gnutls_record_recv(from, buffer, buffer_size);
762     if (size_read < 0) {
763         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_recv(): %s",
764                      gnutls_strerror((int)size_read));
765         return -1;
766     /* EOF */
767     } else if (size_read == 0) {
768         return -1;
769     }
770
771     size_written = gnutls_record_send(to, buffer, (size_t)size_read);
772     if (size_written < 0) {
773         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_send(): %s",
774                      gnutls_strerror((int)size_written));
775         return -1;
776     }
777     if (size_read != size_written) {
778         LOG(ERROR, "read_from_write_to_tls(): only written %ld of %ld bytes!",
779                    (long int)size_written, (long int)size_read);
780         return -1;
781     }
782
783     return 0;
784 }
785
786
787 static int connect_to_host(const char *hostname, const char *port) {
788     struct addrinfo gai_hints;
789     struct addrinfo *gai_result;
790     int gai_return;
791
792     int server_socket;
793     struct addrinfo *server;
794
795     if (hostname == NULL || port == NULL) {
796         return -1;
797     }
798
799     /* Get IP of hostname server. */
800     memset(&gai_hints, 0, sizeof(gai_hints));
801     gai_hints.ai_family   = AF_UNSPEC;
802     gai_hints.ai_socktype = SOCK_STREAM;
803     gai_hints.ai_protocol = 0;
804     gai_hints.ai_flags    = AI_NUMERICSERV /* given port is numeric */
805                           | AI_ADDRCONFIG  /* supported by this computer */
806                           | AI_V4MAPPED;   /* support IPv4 through IPv6 */
807     gai_return = getaddrinfo(hostname, port, &gai_hints, &gai_result);
808     if (gai_return != 0) {
809         if (gai_return == EAI_SYSTEM) {
810             LOG_PERROR(WARNING, "connect_to_host(): getaddrinfo()");
811         } else {
812             LOG(WARNING, "connect_to_host(): getaddrinfo(): %s",
813                          gai_strerror(gai_return));
814         }
815         return -1;
816     }
817
818     /* Now try to connect to each server returned by getaddrinfo(), use the
819      * first successful connect. */
820     for (server = gai_result; server != NULL; server = server->ai_next) {
821         server_socket = socket(server->ai_family,
822                                server->ai_socktype,
823                                server->ai_protocol);
824         if (server_socket < 0) {
825             LOG_PERROR(DEBUG1, "connect_to_host(): socket(), trying next");
826             continue;
827         }
828
829         if (connect(server_socket, server->ai_addr, server->ai_addrlen) == 0) {
830             break;
831         }
832         LOG_PERROR(DEBUG1, "connect_to_host(): connect(), trying next");
833
834         close(server_socket);
835     }
836     /* Make sure we free the result from getaddrinfo(). */
837     freeaddrinfo(gai_result);
838
839     if (server == NULL) {
840         LOG_PERROR(WARNING, "connect_to_host(): no server found, abort");
841         return -1;
842     }
843
844     return server_socket;
845 }
846
847
848 /* Parse HTTP CONNECT request string and save its parameters.
849  *
850  * The following format is expected: "CONNECT host:port HTTP/1.x".
851  *
852  * request and host must have the same size! port must be at least 6 bytes
853  * long (5 + '\0').
854  */
855 static int parse_request(const char *request, char *host, char *port,
856                                               int *version_minor) {
857     int port_unused; /* just used to verify the port is numeric */
858     char *position;
859
860     /* scanf() doesn't check spaces. */
861     if (strncmp(request, "CONNECT ", 8)) {
862         return -1;
863     }
864     /* Check request and extract data, "host:port" is not yet separated. */
865     if (sscanf(request, "CONNECT %s HTTP/1.%d", host, version_minor) != 2) {
866         return -1;
867     }
868     /* Make sure ":port" is there. */
869     if ((position = strchr(host, ':')) == NULL) {
870         return -1;
871     }
872     /* Make sure port is numeric. */
873     if (sscanf(position + 1, "%d", &port_unused) != 1) {
874         return -1;
875     }
876     /* Store it in *port. */
877     strncpy(port, position + 1, 5);
878     port[5] = '\0';
879     /* And remove port from host. */
880     *position = '\0';
881
882     return 0;
883 }