src/connection.c

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