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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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(DEBUG1, "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         /* Recent gnutls-serv (used in the test-suite) won't terminate the
 317          * connection when gnutls_bye(session, GNUTLS_SHUT_RDWR) is used
 318          * before any other data was received. If the validation failed just
 319          * close the connection without waiting for data, we won't read it
 320          * anyway.
 321          *
 322          * For verified connections GNUTLS_SHUT_RDWR is important or we might
 323          * lose data. */
 324         gnutls_bye(server_session, validation_failed ? GNUTLS_SHUT_WR
 325                                                      : GNUTLS_SHUT_RDWR);
 326     }
 327     if (client_session_started) {
 328         gnutls_bye(client_session, GNUTLS_SHUT_RDWR);
 329     }
 330     if (server_session_init) {
 331         gnutls_deinit(server_session);
 332         gnutls_certificate_free_credentials(server_x509_cred);
 333     }
 334     if (client_session_init) {
 335         gnutls_deinit(client_session);
 336         gnutls_certificate_free_cas(client_x509_cred);
 337         gnutls_certificate_free_keys(client_x509_cred);
 338         gnutls_certificate_free_credentials(client_x509_cred);
 339     }
 340
 341     /* Close connection to server/proxy. */
 342     if (server_fd_read != NULL) {
 343         if (server_fd_write != NULL) {
 344             fclose(server_fd_write);
 345         }
 346         fclose(server_fd_read);
 347     } else if (server_socket != -1) {
 348         close(server_socket);
 349     }
 350     LOG(DEBUG1, "connection to server closed");
 351     /* Close connection to client. */
 352     if (client_fd_read != NULL) {
 353         if (client_fd_write != NULL) {
 354             fclose(client_fd_write);
 355         }
 356         fclose(client_fd_read);
 357     } else {
 358         close(client_socket);
 359     }
 360     LOG(DEBUG1, "connection to client closed");
 361
 362     LOG(DEBUG1, "connection finished");
 363 }
 364
 365
 366 static int initialize_tls_session_client(int peer_socket,
 367         const char *hostname,
 368         gnutls_session_t *session,
 369         gnutls_certificate_credentials_t *x509_cred) {
 370     int result;
 371     int use_invalid_cert;
 372     char path[TLSPROXY_MAX_PATH_LENGTH];
 373
 374     /* The "invalid" hostname is special. If it's used we send an invalid
 375      * certificate to let the client know something is wrong. */
 376     use_invalid_cert = (!strcmp(hostname, "invalid"));
 377
 378     if (proxy_certificate_path(hostname, path, sizeof(path)) != 0) {
 379         LOG(ERROR,
 380             "initialize_tls_session_client(): "
 381             "failed to get proxy certificate path");
 382         return -1;
 383     }
 384
 385     result = gnutls_certificate_allocate_credentials(x509_cred);
 386     if (result != GNUTLS_E_SUCCESS) {
 387         LOG(ERROR,
 388             "initialize_tls_session_client(): "
 389             "gnutls_certificate_allocate_credentials(): %s",
 390             gnutls_strerror(result));
 391         return -1;
 392     }
 393
 394     /* Load proxy CA file, this CA "list" is send to the client. */
 395     if (!use_invalid_cert) {
 396         result = gnutls_certificate_set_x509_trust_file(*x509_cred,
 397                                                         PROXY_CA_FILE,
 398                                                         GNUTLS_X509_FMT_PEM);
 399         if (result <= 0) {
 400             LOG(ERROR,
 401                 "initialize_tls_session_client(): can't read CA file: '%s'",
 402                 PROXY_CA_FILE);
 403             gnutls_certificate_free_credentials(*x509_cred);
 404             return -1;
 405         }
 406     }
 407     /* If the invalid hostname was specified do nothing, we use a self-signed
 408      * certificate in this case. */
 409
 410     /* And certificate for this website and proxy's private key. */
 411     if (!use_invalid_cert) {
 412         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 413                                                       path, PROXY_KEY_FILE,
 414                                                       GNUTLS_X509_FMT_PEM);
 415     /* If the invalid hostname was specified load our special "invalid"
 416      * certificate. */
 417     } else {
 418         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 419                                                       PROXY_INVALID_CERT_FILE,
 420                                                       PROXY_KEY_FILE,
 421                                                       GNUTLS_X509_FMT_PEM);
 422     }
 423     if (result != GNUTLS_E_SUCCESS) {
 424         LOG(ERROR,
 425             "initialize_tls_session_client(): "
 426             "can't read server certificate ('%s') or key file ('%s'): %s",
 427             path, PROXY_KEY_FILE, gnutls_strerror(result));
 428         gnutls_certificate_free_credentials(*x509_cred);
 429         /* Could be a missing certificate. */
 430         return -2;
 431     }
 432
 433     gnutls_certificate_set_dh_params(*x509_cred, global_tls_dh_params);
 434
 435     result = gnutls_init(session, GNUTLS_SERVER);
 436     if (result != GNUTLS_E_SUCCESS) {
 437         LOG(ERROR,
 438             "initialize_tls_session_client(): gnutls_init(): %s",
 439             gnutls_strerror(result));
 440         gnutls_certificate_free_credentials(*x509_cred);
 441         return -1;
 442     }
 443     result = gnutls_priority_set(*session, global_tls_priority_cache);
 444     if (result != GNUTLS_E_SUCCESS) {
 445         LOG(ERROR,
 446             "initialize_tls_session_client(): gnutls_priority_set(): %s",
 447             gnutls_strerror(result));
 448         gnutls_deinit(*session);
 449         gnutls_certificate_free_credentials(*x509_cred);
 450         return -1;
 451     }
 452     result = gnutls_credentials_set(*session,
 453                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 454     if (result != GNUTLS_E_SUCCESS) {
 455         LOG(ERROR,
 456             "initialize_tls_session_client(): gnutls_credentials_set(): %s",
 457             gnutls_strerror(result));
 458         gnutls_deinit(*session);
 459         gnutls_certificate_free_credentials(*x509_cred);
 460         return -1;
 461     }
 462
 463     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 464
 465     return 0;
 466 }
 467 static int initialize_tls_session_server(int peer_socket,
 468         gnutls_session_t *session,
 469         gnutls_certificate_credentials_t *x509_cred) {
 470     int result;
 471
 472     result = gnutls_certificate_allocate_credentials(x509_cred);
 473     if (result != GNUTLS_E_SUCCESS) {
 474         LOG(ERROR,
 475             "initialize_tls_session_server(): "
 476             "gnutls_certificate_allocate_credentials(): %s",
 477             gnutls_strerror(result));
 478         return -1;
 479     }
 480
 481     result = gnutls_init(session, GNUTLS_CLIENT);
 482     if (result != GNUTLS_E_SUCCESS) {
 483         LOG(ERROR,
 484             "initialize_tls_session_server(): gnutls_init(): %s",
 485             gnutls_strerror(result));
 486         gnutls_certificate_free_credentials(*x509_cred);
 487         return -1;
 488     }
 489     result = gnutls_priority_set(*session, global_tls_priority_cache);
 490     if (result != GNUTLS_E_SUCCESS) {
 491         LOG(ERROR,
 492             "initialize_tls_session_server(): gnutls_priority_set(): %s",
 493             gnutls_strerror(result));
 494         gnutls_deinit(*session);
 495         gnutls_certificate_free_credentials(*x509_cred);
 496         return -1;
 497     }
 498     result = gnutls_credentials_set(*session,
 499                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 500     if (result != GNUTLS_E_SUCCESS) {
 501         LOG(ERROR,
 502             "initialize_tls_session_server(): gnutls_credentials_set(): %s",
 503             gnutls_strerror(result));
 504         gnutls_deinit(*session);
 505         gnutls_certificate_free_credentials(*x509_cred);
 506         return -1;
 507     }
 508
 509     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 510
 511     return 0;
 512 }
 513
 514
 515 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd) {
 516     *read_fd = fdopen(socket, "r");
 517     if (*read_fd == NULL) {
 518         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"r\") failed");
 519         return -1;
 520     }
 521
 522     *write_fd = fdopen(dup(socket), "w");
 523     if (*write_fd == NULL) {
 524         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"w\") failed");
 525         fclose(*read_fd);
 526         *read_fd = NULL; /* "tell" caller read_fd is already closed */
 527         return -1;
 528     }
 529
 530     return 0;
 531 }
 532
 533 /* Read HTTP request line and headers (ignored).
 534  *
 535  * On success 0 is returned, -1 on client error, -2 on unexpected EOF.
 536  */
 537 static int read_http_request(FILE *client_fd, char *request, size_t length) {
 538     char buffer[MAX_REQUEST_LINE];
 539     int found_proxy_authorization;
 540
 541     assert(length <= INT_MAX);
 542     if (fgets(request, (int)length, client_fd) == NULL) {
 543         if (ferror(client_fd)) {
 544             LOG_PERROR(WARNING, "read_http_request(): fgets()");
 545             return -1;
 546         }
 547         /* EOF */
 548         return -2;
 549     }
 550
 551     found_proxy_authorization = 0;
 552     while (fgets(buffer, sizeof(buffer), client_fd) != NULL) {
 553         const char *authentication = "Proxy-Authorization: Basic ";
 554
 555         if (http_digest_authorization != NULL
 556                 && !strncmp(buffer, authentication, strlen(authentication))) {
 557             found_proxy_authorization = 1;
 558
 559             /* Check if the passphrase matches. */
 560             strtok(buffer, "\r\n");
 561             if (strcmp(buffer + strlen(authentication),
 562                        http_digest_authorization)) {
 563                 return -3;
 564             }
 565         }
 566
 567         /* End of header. */
 568         if (!strcmp(buffer, "\n") || !strcmp(buffer, "\r\n")) {
 569             break;
 570         }
 571     }
 572     if (ferror(client_fd)) {
 573         LOG_PERROR(WARNING, "read_http_request(): fgets()");
 574         return -1;
 575     }
 576
 577     if (http_digest_authorization != NULL && !found_proxy_authorization) {
 578         return -3;
 579     }
 580
 581     return 0;
 582 }
 583
 584 static void send_bad_request(FILE *client_fd) {
 585     const char error[] = "400 Bad Request";
 586     const char msg[]   = "Your browser sent an invalid request.";
 587     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 588     fflush(client_fd);
 589 }
 590 static void send_authentication_required(FILE *client_fd) {
 591     const char error[] = "407 Proxy Authentication Required";
 592     const char auth[]  = "Proxy-Authenticate: Basic realm=\"tlsproxy\"\r\n";
 593     const char msg[]   = "TODO";
 594     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, auth, error, error, msg);
 595     fflush(client_fd);
 596 }
 597 static void send_forwarding_failure(FILE *client_fd) {
 598     const char error[] = "503 Forwarding failure";
 599     const char msg[]   = "Failed to connect to server, check logs.";
 600     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 601     fflush(client_fd);
 602 }
 603 static void tls_send_invalid_cert_message(gnutls_session_t session) {
 604     const char error[] = "500 Internal Server Error";
 605     const char msg[]   = "Server certificate validation failed, check logs.";
 606
 607     int result;
 608     char buffer[sizeof(HTTP_RESPONSE_FORMAT)
 609                 + 3 * sizeof(error) + sizeof(msg)];
 610
 611     result = snprintf(buffer, sizeof(buffer), HTTP_RESPONSE_FORMAT,
 612                                               error, "", error, error, msg);
 613     assert(result > 0 && (size_t)result < sizeof(buffer));
 614
 615     gnutls_record_send(session, buffer, strlen(buffer));
 616 }
 617
 618
 619 /* Transfer data between client and server sockets until one closes the
 620  * connection. */
 621 static void transfer_data(int client, int server) {
 622     struct pollfd fds[2];
 623     fds[0].fd      = client;
 624     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 625     fds[0].revents = 0;
 626     fds[1].fd      = server;
 627     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 628     fds[1].revents = 0;
 629
 630     LOG(DEBUG1, "transfer_data(): %d -> %d", client, server);
 631
 632     for (;;) {
 633         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 634         if (result < 0) {
 635             LOG_PERROR(ERROR, "transfer_data(): poll()");
 636             return;
 637         }
 638
 639         /* Data available from client. */
 640         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 641             if (read_from_write_to(client, server) != 0) {
 642                 /* EOF (or other error) */
 643                 break;
 644             }
 645         }
 646         /* Data available from server. */
 647         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 648             if (read_from_write_to(server, client) != 0) {
 649                 /* EOF (or other error) */
 650                 break;
 651             }
 652         }
 653
 654         /* Client closed connection. */
 655         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 656             break;
 657         }
 658         /* Server closed connection. */
 659         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 660             break;
 661         }
 662     }
 663 }
 664
 665 /* Read available data from socket from and write it to socket to. At maximum
 666  * 4096 bytes are read/written. */
 667 static int read_from_write_to(int from, int to) {
 668     ssize_t size_read;
 669     ssize_t size_written;
 670     char buffer[4096];
 671
 672     size_read = read(from, buffer, sizeof(buffer));
 673     if (size_read < 0) {
 674         LOG_PERROR(WARNING, "read_from_write_to(): read()");
 675         return -1;
 676     /* EOF */
 677     } else if (size_read == 0) {
 678         return -1;
 679     }
 680
 681     size_written = write(to, buffer, (size_t)size_read);
 682     if (size_written < 0) {
 683         LOG_PERROR(WARNING, "read_from_write_to(): write()");
 684         return -1;
 685     }
 686     if (size_read != size_written) {
 687         LOG(ERROR, "read_from_write_to(): only written %ld of %ld bytes!",
 688                    (long int)size_written, (long int)size_read);
 689         return -1;
 690     }
 691
 692     return 0;
 693 }
 694
 695 /* Transfer data between client and server TLS connection until one closes the
 696  * connection. */
 697 static void transfer_data_tls(int client, int server,
 698                               gnutls_session_t client_session,
 699                               gnutls_session_t server_session) {
 700     size_t buffer_size;
 701
 702     struct pollfd fds[2];
 703     fds[0].fd      = client;
 704     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 705     fds[0].revents = 0;
 706     fds[1].fd      = server;
 707     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 708     fds[1].revents = 0;
 709
 710     /* Get maximum possible buffer size. */
 711     buffer_size = gnutls_record_get_max_size(client_session);
 712     if (gnutls_record_get_max_size(server_session) < buffer_size) {
 713         buffer_size = gnutls_record_get_max_size(server_session);
 714     }
 715     LOG(DEBUG1, "transfer_data_tls(): suggested buffer size: %ld",
 716                 (long int)buffer_size);
 717
 718     for (;;) {
 719         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 720         if (result < 0) {
 721             LOG_PERROR(ERROR, "transfer_data(): poll()");
 722             return;
 723         }
 724
 725         /* Data available from client. */
 726         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 727             if (read_from_write_to_tls(client_session, server_session,
 728                                        buffer_size) != 0) {
 729                 /* EOF (or other error) */
 730                 break;
 731             }
 732         }
 733         /* Data available from server. */
 734         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 735             if (read_from_write_to_tls(server_session, client_session,
 736                                        buffer_size) != 0) {
 737                 /* EOF (or other error) */
 738                 break;
 739             }
 740         }
 741
 742         /* Client closed connection. */
 743         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 744             break;
 745         }
 746         /* Server closed connection. */
 747         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 748             break;
 749         }
 750     }
 751 }
 752
 753 /* Read available data from session from and write to session to. */
 754 static int read_from_write_to_tls(gnutls_session_t from,
 755                                   gnutls_session_t to,
 756                                   size_t buffer_size) {
 757     ssize_t size_read;
 758     ssize_t size_written;
 759     char buffer[16384];
 760
 761     if (buffer_size > sizeof(buffer)) {
 762         LOG(WARNING, "read_from_write_to_tls(): reduced buffer size to %ld",
 763                      (long int)(sizeof(buffer)));
 764         buffer_size = sizeof(buffer);
 765     }
 766
 767     size_read = gnutls_record_recv(from, buffer, buffer_size);
 768     if (size_read < 0) {
 769         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_recv(): %s",
 770                      gnutls_strerror((int)size_read));
 771         return -1;
 772     /* EOF */
 773     } else if (size_read == 0) {
 774         return -1;
 775     }
 776
 777     size_written = gnutls_record_send(to, buffer, (size_t)size_read);
 778     if (size_written < 0) {
 779         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_send(): %s",
 780                      gnutls_strerror((int)size_written));
 781         return -1;
 782     }
 783     if (size_read != size_written) {
 784         LOG(ERROR, "read_from_write_to_tls(): only written %ld of %ld bytes!",
 785                    (long int)size_written, (long int)size_read);
 786         return -1;
 787     }
 788
 789     return 0;
 790 }
 791
 792
 793 static int connect_to_host(const char *hostname, const char *port) {
 794     struct addrinfo gai_hints;
 795     struct addrinfo *gai_result;
 796     int gai_return;
 797
 798     int server_socket;
 799     struct addrinfo *server;
 800
 801     if (hostname == NULL || port == NULL) {
 802         return -1;
 803     }
 804
 805     /* Get IP of hostname server. */
 806     memset(&gai_hints, 0, sizeof(gai_hints));
 807     gai_hints.ai_family   = AF_UNSPEC;
 808     gai_hints.ai_socktype = SOCK_STREAM;
 809     gai_hints.ai_protocol = 0;
 810     gai_hints.ai_flags    = AI_NUMERICSERV /* given port is numeric */
 811                           | AI_ADDRCONFIG  /* supported by this computer */
 812                           | AI_V4MAPPED;   /* support IPv4 through IPv6 */
 813     gai_return = getaddrinfo(hostname, port, &gai_hints, &gai_result);
 814     if (gai_return != 0) {
 815         if (gai_return == EAI_SYSTEM) {
 816             LOG_PERROR(WARNING, "connect_to_host(): getaddrinfo()");
 817         } else {
 818             LOG(WARNING, "connect_to_host(): getaddrinfo(): %s",
 819                          gai_strerror(gai_return));
 820         }
 821         return -1;
 822     }
 823
 824     /* Now try to connect to each server returned by getaddrinfo(), use the
 825      * first successful connect. */
 826     for (server = gai_result; server != NULL; server = server->ai_next) {
 827         server_socket = socket(server->ai_family,
 828                                server->ai_socktype,
 829                                server->ai_protocol);
 830         if (server_socket < 0) {
 831             LOG_PERROR(DEBUG1, "connect_to_host(): socket(), trying next");
 832             continue;
 833         }
 834
 835         if (connect(server_socket, server->ai_addr, server->ai_addrlen) == 0) {
 836             break;
 837         }
 838         LOG_PERROR(DEBUG1, "connect_to_host(): connect(), trying next");
 839
 840         close(server_socket);
 841     }
 842     /* Make sure we free the result from getaddrinfo(). */
 843     freeaddrinfo(gai_result);
 844
 845     if (server == NULL) {
 846         LOG_PERROR(WARNING, "connect_to_host(): no server found, abort");
 847         return -1;
 848     }
 849
 850     return server_socket;
 851 }
 852
 853
 854 /* Parse HTTP CONNECT request string and save its parameters.
 855  *
 856  * The following format is expected: "CONNECT host:port HTTP/1.x".
 857  *
 858  * request and host must have the same size! port must be at least 6 bytes
 859  * long (5 + '\0').
 860  */
 861 static int parse_request(const char *request, char *host, char *port,
 862                                               int *version_minor) {
 863     int port_unused; /* just used to verify the port is numeric */
 864     char *position;
 865
 866     /* scanf() doesn't check spaces. */
 867     if (strncmp(request, "CONNECT ", 8)) {
 868         return -1;
 869     }
 870     /* Check request and extract data, "host:port" is not yet separated. */
 871     if (sscanf(request, "CONNECT %s HTTP/1.%d", host, version_minor) != 2) {
 872         return -1;
 873     }
 874     /* Make sure ":port" is there. */
 875     if ((position = strchr(host, ':')) == NULL) {
 876         return -1;
 877     }
 878     /* Make sure port is numeric. */
 879     if (sscanf(position + 1, "%d", &port_unused) != 1) {
 880         return -1;
 881     }
 882     /* Store it in *port. */
 883     strncpy(port, position + 1, 5);
 884     port[5] = '\0';
 885     /* And remove port from host. */
 886     *position = '\0';
 887
 888     return 0;
 889 }