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 <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(unsigned 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(unsigned 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 }