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