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 #include <gnutls/x509.h>
  32
  33
  34 /* Maximum length of a HTTP request line. Longer request lines are aborted
  35  * with an error. The standard doesn't specify a maximum line length but this
  36  * should be a good limit to make processing simpler. As HTTPS is used this
  37  * doesn't limit long GET requests. */
  38 #define MAX_REQUEST_LINE 4096
  39
  40 /* Format string used to send HTTP/1.0 error responses to the client.
  41  *
  42  * %s is used 5 times, first is the error code, then additional headers, next
  43  * two are the error code (no %n$s which is not in C98!), the last is the
  44  * message. */
  45 #define HTTP_RESPONSE_FORMAT "HTTP/1.0 %s\r\n\
  46 Content-Type: text/html; charset=US-ASCII\r\n\
  47 %s\r\n\
  48 <!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">\n\
  49 <html>\n\
  50 <head><title>%s</title></head>\n\
  51 <body>\n\
  52 <h1>%s</h1>\n\
  53 <p>%s</p>\n\
  54 </body>\n\
  55 </html>\n"
  56
  57
  58 static int initialize_tls_session_client(int peer_socket,
  59         const char *hostname,
  60         gnutls_session_t *session,
  61         gnutls_certificate_credentials_t *x509_cred);
  62 static int initialize_tls_session_server(int peer_socket,
  63         gnutls_session_t *session,
  64         gnutls_certificate_credentials_t *x509_cred);
  65 static int initialize_tls_session_both(unsigned int flags,
  66         int peer_socket,
  67         gnutls_session_t *session,
  68         gnutls_certificate_credentials_t *x509_cred);
  69
  70 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd);
  71 static int read_http_request(FILE *client_fd, char *request, size_t length);
  72 static void send_bad_request(FILE *client_fd);
  73 static void send_authentication_required(FILE *client_fd);
  74 static void send_forwarding_failure(FILE *client_fd);
  75 static void tls_send_invalid_cert_message(gnutls_session_t session);
  76
  77 static void transfer_data(int client, int server);
  78 static int read_from_write_to(int from, int to);
  79 static void transfer_data_tls(int client, int server,
  80                               gnutls_session_t client_session,
  81                               gnutls_session_t server_session);
  82 static int read_from_write_to_tls(gnutls_session_t from, gnutls_session_t to,
  83                                   size_t buffer_size);
  84
  85 static int connect_to_host(const char *hostname, const char *port);
  86
  87 static int parse_request(const char *buffer, char *host, char *port,
  88                                              int *version_minor);
  89
  90 static void log_session_information(gnutls_session_t session);
  91
  92
  93 void handle_connection(int client_socket) {
  94     int server_socket;
  95     FILE *client_fd_read, *client_fd_write, *server_fd_read, *server_fd_write;
  96
  97     char buffer[MAX_REQUEST_LINE];
  98     char host[MAX_REQUEST_LINE];
  99     char port[5 + 1];
 100
 101     int version_minor; /* x in HTTP/1.x */
 102     int result;
 103
 104     /* client_x509_cred is used when talking to the client (acting as a TSL
 105      * server), server_x509_cred is used when talking to the server (acting as
 106      * a TSL client). */
 107     gnutls_certificate_credentials_t client_x509_cred, server_x509_cred;
 108
 109     gnutls_session_t client_session, server_session;
 110     /* initialize_tls_session_*() called? - used for goto out */
 111     int client_session_init, server_session_init;
 112     /* gnutls_handshake() called? - used for goto out */
 113     int client_session_started, server_session_started;
 114     /* Validation failed? If yes we need to send the special "invalid"
 115      * certificate. */
 116     int validation_failed;
 117
 118     LOG(DEBUG1, "new connection");
 119
 120     server_socket = -1;
 121     client_fd_read = NULL;
 122     client_fd_write = NULL;
 123     server_fd_read = NULL;
 124     server_fd_write = NULL;
 125     client_session_init = 0;
 126     server_session_init = 0;
 127     client_session_started = 0;
 128     server_session_started = 0;
 129     validation_failed = 0;
 130
 131     if (fdopen_read_write(client_socket, &client_fd_read,
 132                                          &client_fd_write) != 0) {
 133         goto out;
 134     }
 135
 136     /* Read request line (CONNECT ..) and headers (they are discarded). */
 137     result = read_http_request(client_fd_read, buffer, sizeof(buffer));
 138     if (result == -1) {
 139         LOG(WARNING, "read_http_request(): client read error");
 140         goto out;
 141     } else if (result == -2) {
 142         LOG(WARNING, "read_http_request(): client EOF");
 143         send_bad_request(client_fd_write);
 144         goto out;
 145     } else if (result == -3) {
 146         LOG(WARNING, "read_http_request(): proxy authentication failed");
 147         send_authentication_required(client_fd_write);
 148         goto out;
 149     }
 150
 151     if (parse_request(buffer, host, port, &version_minor) != 0) {
 152         LOG(WARNING, "bad request: >%s<", buffer);
 153         send_bad_request(client_fd_write);
 154         goto out;
 155     }
 156
 157     LOG(DEBUG2, "target: %s:%s (HTTP 1.%d)", host, port, version_minor);
 158
 159     /* Connect to proxy server or directly to server. */
 160     if (global_proxy_host != NULL && global_proxy_port != NULL) {
 161         LOG(DEBUG1, "connecting to %s:%s", global_proxy_host,
 162                                            global_proxy_port);
 163         server_socket = connect_to_host(global_proxy_host, global_proxy_port);
 164     } else {
 165         LOG(DEBUG1, "connecting to %s:%s", host, port);
 166         server_socket = connect_to_host(host, port);
 167     }
 168
 169     if (server_socket < 0) {
 170         LOG(WARNING, "failed to connect to server");
 171         send_forwarding_failure(client_fd_write);
 172         goto out;
 173     }
 174     if (fdopen_read_write(server_socket, &server_fd_read,
 175                                          &server_fd_write) != 0) {
 176         send_forwarding_failure(client_fd_write);
 177         goto out;
 178     }
 179
 180     /* Connect to proxy if requested (command line option). */
 181     if (global_proxy_host != NULL && global_proxy_port != NULL) {
 182         fprintf(server_fd_write, "CONNECT %s:%s HTTP/1.0\r\n", host, port);
 183         fprintf(server_fd_write, "\r\n");
 184         fflush(server_fd_write);
 185
 186         /* Read response line from proxy server. */
 187         result = read_http_request(server_fd_read, buffer, sizeof(buffer));
 188         if (result == -1) {
 189             LOG(WARNING, "read_http_request(): proxy read error");
 190             send_forwarding_failure(client_fd_write);
 191             goto out;
 192         } else if (result == -2) {
 193             LOG(WARNING, "read_http_request(): proxy EOF");
 194             send_forwarding_failure(client_fd_write);
 195             goto out;
 196         }
 197
 198         /* Check response of proxy server. */
 199         if (strncmp(buffer, "HTTP/1.0 200", 12)) {
 200             LOG(WARNING, "bad proxy response: >%s<", buffer);
 201             send_forwarding_failure(client_fd_write);
 202             goto out;
 203         }
 204     }
 205
 206     LOG(DEBUG1, "connection to server established");
 207
 208     /* If the -u option is used and we don't know this hostname's server
 209      * certificate then just pass through the connection and let the client
 210      * verify the server certificate. */
 211     if (global_passthrough_unknown) {
 212         char path[TLSPROXY_MAX_PATH_LENGTH];
 213         FILE *file = NULL;
 214
 215         if (server_certificate_file(&file, host, path, sizeof(path)) == -2) {
 216             /* We've established a connection, tell the client. */
 217             fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
 218             fprintf(client_fd_write, "\r\n");
 219             fflush(client_fd_write);
 220
 221             LOG(DEBUG1, "transferring data");
 222
 223             /* Proxy data between client and server until one side is done
 224              * (EOF or error). */
 225             transfer_data(client_socket, server_socket);
 226
 227             LOG(DEBUG1, "finished transferring data");
 228
 229             goto out;
 230         }
 231         /* server_certificate_file() may have opened the file, close it. */
 232         if (file != NULL) {
 233             fclose(file);
 234         }
 235     }
 236
 237     /* Initialize TLS client credentials to talk to the server. */
 238     result = initialize_tls_session_server(server_socket, &server_session,
 239                                                           &server_x509_cred);
 240     if (result != 0) {
 241         LOG(WARNING, "initialize_tls_session_server() failed");
 242         send_forwarding_failure(client_fd_write);
 243         goto out;
 244     }
 245     server_session_init = 1;
 246
 247     LOG(DEBUG1, "starting server TLS handshake");
 248
 249     /* Try to establish TLS handshake between us and server. */
 250     result = gnutls_handshake(server_session);
 251     if (result != GNUTLS_E_SUCCESS) {
 252         LOG(WARNING, "server TLS handshake failed: %s",
 253                      gnutls_strerror(result));
 254         send_forwarding_failure(client_fd_write);
 255         goto out;
 256     }
 257     server_session_started = 1;
 258
 259     LOG(DEBUG1, "server TLS handshake finished");
 260
 261     if (global_log_level >= LOG_DEBUG2_LEVEL) {
 262         log_session_information(server_session);
 263     }
 264
 265     /* Make sure the server certificate is valid and known. */
 266     if (verify_tls_connection(server_session, host) != 0) {
 267         LOG(ERROR, "server certificate validation failed!");
 268         /* We'll send the error message over our TLS connection to the client,
 269          * but with an invalid certificate. No data is transfered from/to the
 270          * target server. */
 271         validation_failed = 1;
 272     }
 273
 274     /* Initialize TLS server credentials to talk to the client. */
 275     result = initialize_tls_session_client(client_socket,
 276                                            /* use a special host if the server
 277                                             * certificate was invalid */
 278                                            (validation_failed) ? "invalid"
 279                                                                : host,
 280                                            &client_session,
 281                                            &client_x509_cred);
 282     if (result != 0) {
 283         LOG(WARNING, "initialize_tls_session_client() failed");
 284         send_forwarding_failure(client_fd_write);
 285         goto out;
 286     }
 287     client_session_init = 1;
 288
 289     /* We've established a connection, tell the client. */
 290     fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
 291     fprintf(client_fd_write, "\r\n");
 292     fflush(client_fd_write);
 293
 294     LOG(DEBUG1, "starting client TLS handshake");
 295
 296     /* Try to establish TLS handshake between client and us. */
 297     result = gnutls_handshake(client_session);
 298     if (result != GNUTLS_E_SUCCESS) {
 299         LOG(WARNING, "client TLS handshake failed: %s",
 300                      gnutls_strerror(result));
 301         send_forwarding_failure(client_fd_write);
 302         goto out;
 303     }
 304     client_session_started = 1;
 305
 306     LOG(DEBUG1, "client TLS handshake finished");
 307
 308     if (global_log_level >= LOG_DEBUG2_LEVEL) {
 309         log_session_information(client_session);
 310     }
 311
 312     /* Tell the client that the verification failed. Shouldn't be necessary as
 313      * the client should terminate the connection because he received the
 314      * invalid certificate but better be sure. */
 315     if (validation_failed) {
 316         tls_send_invalid_cert_message(client_session);
 317         goto out;
 318     }
 319
 320     LOG(DEBUG1, "transferring TLS data");
 321
 322     /* Proxy data between client and server until one side is done (EOF or
 323      * error). */
 324     transfer_data_tls(client_socket, server_socket,
 325                       client_session, server_session);
 326
 327     LOG(DEBUG1, "finished transferring TLS data");
 328
 329 out:
 330     /* Close TLS sessions if necessary. Use GNUTLS_SHUT_RDWR so the data is
 331      * reliable transmitted. */
 332     if (server_session_started) {
 333         /* Recent gnutls-serv (used in the test-suite) won't terminate the
 334          * connection when gnutls_bye(session, GNUTLS_SHUT_RDWR) is used
 335          * before any other data was received. If the validation failed just
 336          * close the connection without waiting for data, we won't read it
 337          * anyway.
 338          *
 339          * For verified connections GNUTLS_SHUT_RDWR is important or we might
 340          * lose data. */
 341         gnutls_bye(server_session, validation_failed ? GNUTLS_SHUT_WR
 342                                                      : GNUTLS_SHUT_RDWR);
 343     }
 344     if (client_session_started) {
 345         gnutls_bye(client_session, GNUTLS_SHUT_RDWR);
 346     }
 347     if (server_session_init) {
 348         gnutls_deinit(server_session);
 349         gnutls_certificate_free_credentials(server_x509_cred);
 350     }
 351     if (client_session_init) {
 352         gnutls_deinit(client_session);
 353         gnutls_certificate_free_credentials(client_x509_cred);
 354     }
 355
 356     /* Close connection to server/proxy. */
 357     if (server_fd_read != NULL) {
 358         if (server_fd_write != NULL) {
 359             fclose(server_fd_write);
 360         }
 361         fclose(server_fd_read);
 362     } else if (server_socket != -1) {
 363         close(server_socket);
 364     }
 365     LOG(DEBUG1, "connection to server closed");
 366     /* Close connection to client. */
 367     if (client_fd_read != NULL) {
 368         if (client_fd_write != NULL) {
 369             fclose(client_fd_write);
 370         }
 371         fclose(client_fd_read);
 372     } else {
 373         close(client_socket);
 374     }
 375     LOG(DEBUG1, "connection to client closed");
 376
 377     LOG(DEBUG1, "connection finished");
 378 }
 379
 380
 381 static int initialize_tls_session_client(int peer_socket,
 382         const char *hostname,
 383         gnutls_session_t *session,
 384         gnutls_certificate_credentials_t *x509_cred) {
 385     int result;
 386     int use_invalid_cert;
 387     char path[TLSPROXY_MAX_PATH_LENGTH];
 388
 389     /* The "invalid" hostname is special. If it's used we send an invalid
 390      * certificate to let the client know something is wrong. */
 391     use_invalid_cert = (!strcmp(hostname, "invalid"));
 392
 393     if (proxy_certificate_path(hostname, path, sizeof(path)) != 0) {
 394         LOG(ERROR,
 395             "initialize_tls_session_client(): "
 396             "failed to get proxy certificate path");
 397         return -1;
 398     }
 399
 400     result = gnutls_certificate_allocate_credentials(x509_cred);
 401     if (result != GNUTLS_E_SUCCESS) {
 402         LOG(ERROR,
 403             "initialize_tls_session_client(): "
 404             "gnutls_certificate_allocate_credentials(): %s",
 405             gnutls_strerror(result));
 406         return -1;
 407     }
 408
 409     /* Load proxy CA file, this CA "list" is send to the client. */
 410     if (!use_invalid_cert) {
 411         result = gnutls_certificate_set_x509_trust_file(*x509_cred,
 412                                                         PROXY_CA_PATH,
 413                                                         GNUTLS_X509_FMT_PEM);
 414         if (result <= 0) {
 415             LOG(ERROR,
 416                 "initialize_tls_session_client(): can't read CA file: '%s'",
 417                 PROXY_CA_PATH);
 418             gnutls_certificate_free_credentials(*x509_cred);
 419             return -1;
 420         } else if (result != 1) {
 421             /* Must contain only one CA, our proxy CA. */
 422             LOG(ERROR, "initialize_tls_session_client(): multiple CAs found");
 423             gnutls_certificate_free_credentials(*x509_cred);
 424             return -1;
 425         }
 426     }
 427     /* If the invalid hostname was specified do nothing, we use a self-signed
 428      * certificate in this case. */
 429
 430     /* And certificate for this website and proxy's private key. */
 431     if (!use_invalid_cert) {
 432         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 433                                                       path,
 434                                                       PROXY_KEY_PATH,
 435                                                       GNUTLS_X509_FMT_PEM);
 436     /* If the invalid hostname was specified load our special "invalid"
 437      * certificate. */
 438     } else {
 439         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 440                                                       PROXY_INVALID_CERT_PATH,
 441                                                       PROXY_KEY_PATH,
 442                                                       GNUTLS_X509_FMT_PEM);
 443     }
 444     if (result != GNUTLS_E_SUCCESS) {
 445         LOG(ERROR,
 446             "initialize_tls_session_client(): "
 447             "can't read server certificate ('%s') or key file ('%s'): %s",
 448             path, PROXY_KEY_PATH, gnutls_strerror(result));
 449         gnutls_certificate_free_credentials(*x509_cred);
 450         /* Could be a missing certificate. */
 451         return -2;
 452     }
 453
 454     gnutls_certificate_set_dh_params(*x509_cred, global_tls_dh_params);
 455
 456     return initialize_tls_session_both(GNUTLS_SERVER,
 457                                        peer_socket, session, x509_cred);
 458 }
 459 static int initialize_tls_session_server(int peer_socket,
 460         gnutls_session_t *session,
 461         gnutls_certificate_credentials_t *x509_cred) {
 462     int result;
 463
 464     result = gnutls_certificate_allocate_credentials(x509_cred);
 465     if (result != GNUTLS_E_SUCCESS) {
 466         LOG(ERROR,
 467             "initialize_tls_session_server(): "
 468             "gnutls_certificate_allocate_credentials(): %s",
 469             gnutls_strerror(result));
 470         return -1;
 471     }
 472
 473     return initialize_tls_session_both(GNUTLS_CLIENT,
 474                                        peer_socket, session, x509_cred);
 475 }
 476 static int initialize_tls_session_both(unsigned int flags,
 477         int peer_socket,
 478         gnutls_session_t *session,
 479         gnutls_certificate_credentials_t *x509_cred) {
 480     int result;
 481
 482     *session = NULL;
 483
 484     result = gnutls_init(session, flags);
 485     if (result != GNUTLS_E_SUCCESS) {
 486         LOG(ERROR,
 487             "initialize_tls_session_both(): gnutls_init(): %s",
 488             gnutls_strerror(result));
 489         goto err;
 490     }
 491     result = gnutls_priority_set(*session, global_tls_priority_cache);
 492     if (result != GNUTLS_E_SUCCESS) {
 493         LOG(ERROR,
 494             "initialize_tls_session_both(): gnutls_priority_set(): %s",
 495             gnutls_strerror(result));
 496         goto err;
 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_both(): gnutls_credentials_set(): %s",
 503             gnutls_strerror(result));
 504         goto err;
 505     }
 506
 507 #ifdef HAVE_GNUTLS_TRANSPORT_SET_INT2
 508     /* gnutls_transport_set_int() is a macro. */
 509     gnutls_transport_set_int(*session, peer_socket);
 510 #else
 511     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 512 #endif
 513
 514     return 0;
 515
 516 err:
 517     if (*session) {
 518         gnutls_deinit(*session);
 519     }
 520     gnutls_certificate_free_credentials(*x509_cred);
 521     return -1;
 522 }
 523
 524
 525 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd) {
 526     *read_fd = fdopen(socket, "r");
 527     if (*read_fd == NULL) {
 528         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"r\") failed");
 529         return -1;
 530     }
 531
 532     *write_fd = fdopen(dup(socket), "w");
 533     if (*write_fd == NULL) {
 534         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"w\") failed");
 535         fclose(*read_fd);
 536         *read_fd = NULL; /* "tell" caller read_fd is already closed */
 537         return -1;
 538     }
 539
 540     return 0;
 541 }
 542
 543 /* Read HTTP request line and headers (ignored).
 544  *
 545  * On success 0 is returned, -1 on client error, -2 on unexpected EOF.
 546  */
 547 static int read_http_request(FILE *client_fd, char *request, size_t length) {
 548     char buffer[MAX_REQUEST_LINE];
 549     int found_proxy_authorization;
 550
 551     assert(length <= INT_MAX);
 552     if (fgets(request, (int)length, client_fd) == NULL) {
 553         if (ferror(client_fd)) {
 554             LOG_PERROR(WARNING, "read_http_request(): fgets()");
 555             return -1;
 556         }
 557         /* EOF */
 558         return -2;
 559     }
 560
 561     found_proxy_authorization = 0;
 562     while (fgets(buffer, sizeof(buffer), client_fd) != NULL) {
 563         const char *authentication = "Proxy-Authorization: Basic ";
 564
 565         if (global_http_digest_authorization != NULL
 566                 && !strncmp(buffer, authentication, strlen(authentication))) {
 567             found_proxy_authorization = 1;
 568
 569             /* Check if the passphrase matches. */
 570             strtok(buffer, "\r\n");
 571             if (strcmp(buffer + strlen(authentication),
 572                        global_http_digest_authorization)) {
 573                 return -3;
 574             }
 575         }
 576
 577         /* End of header. */
 578         if (!strcmp(buffer, "\n") || !strcmp(buffer, "\r\n")) {
 579             break;
 580         }
 581     }
 582     if (ferror(client_fd)) {
 583         LOG_PERROR(WARNING, "read_http_request(): fgets()");
 584         return -1;
 585     } else if (feof(client_fd)) {
 586         return -2;
 587     }
 588
 589     if (global_http_digest_authorization != NULL && !found_proxy_authorization) {
 590         return -3;
 591     }
 592
 593     return 0;
 594 }
 595
 596 static void send_bad_request(FILE *client_fd) {
 597     const char error[] = "400 Bad Request";
 598     const char msg[]   = "Your browser sent an invalid request.";
 599     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 600     fflush(client_fd);
 601 }
 602 static void send_authentication_required(FILE *client_fd) {
 603     const char error[] = "407 Proxy Authentication Required";
 604     const char auth[]  = "Proxy-Authenticate: Basic realm=\"tlsproxy\"\r\n";
 605     const char msg[]   = "TODO";
 606     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, auth, error, error, msg);
 607     fflush(client_fd);
 608 }
 609 static void send_forwarding_failure(FILE *client_fd) {
 610     const char error[] = "503 Forwarding failure";
 611     const char msg[]   = "Failed to connect to server, check logs.";
 612     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 613     fflush(client_fd);
 614 }
 615 static void tls_send_invalid_cert_message(gnutls_session_t session) {
 616     const char error[] = "500 Internal Server Error";
 617     const char msg[]   = "Server certificate validation failed, check logs.";
 618
 619     int result;
 620     char buffer[sizeof(HTTP_RESPONSE_FORMAT)
 621                 + 3 * sizeof(error) + sizeof(msg)];
 622
 623     result = snprintf(buffer, sizeof(buffer), HTTP_RESPONSE_FORMAT,
 624                                               error, "", error, error, msg);
 625     assert(result > 0 && (size_t)result < sizeof(buffer));
 626
 627     gnutls_record_send(session, buffer, strlen(buffer));
 628 }
 629
 630
 631 /* Transfer data between client and server sockets until one closes the
 632  * connection. */
 633 static void transfer_data(int client, int server) {
 634     struct pollfd fds[2];
 635     fds[0].fd      = client;
 636     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 637     fds[0].revents = 0;
 638     fds[1].fd      = server;
 639     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 640     fds[1].revents = 0;
 641
 642     LOG(DEBUG2, "transfer_data(): %d -> %d", client, server);
 643
 644     for (;;) {
 645         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 646         if (result < 0) {
 647             LOG_PERROR(ERROR, "transfer_data(): poll()");
 648             return;
 649         }
 650
 651         /* Data available from client. */
 652         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 653             if (read_from_write_to(client, server) != 0) {
 654                 /* EOF (or other error) */
 655                 break;
 656             }
 657         }
 658         /* Data available from server. */
 659         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 660             if (read_from_write_to(server, client) != 0) {
 661                 /* EOF (or other error) */
 662                 break;
 663             }
 664         }
 665
 666         /* Client closed connection. */
 667         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 668             break;
 669         }
 670         /* Server closed connection. */
 671         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 672             break;
 673         }
 674     }
 675 }
 676
 677 /* Read available data from socket from and write it to socket to. At maximum
 678  * 4096 bytes are read/written. */
 679 static int read_from_write_to(int from, int to) {
 680     ssize_t size_read;
 681     ssize_t size_written;
 682     char buffer[4096];
 683
 684     size_read = read(from, buffer, sizeof(buffer));
 685     if (size_read < 0) {
 686         LOG_PERROR(WARNING, "read_from_write_to(): read()");
 687         return -1;
 688     /* EOF */
 689     } else if (size_read == 0) {
 690         return -1;
 691     }
 692
 693     size_written = write(to, buffer, (size_t)size_read);
 694     if (size_written < 0) {
 695         LOG_PERROR(WARNING, "read_from_write_to(): write()");
 696         return -1;
 697     }
 698     if (size_read != size_written) {
 699         LOG(ERROR, "read_from_write_to(): only written %zu of %zu bytes!",
 700                    size_written, size_read);
 701         return -1;
 702     }
 703
 704     return 0;
 705 }
 706
 707 /* Transfer data between client and server TLS connection until one closes the
 708  * connection. */
 709 static void transfer_data_tls(int client, int server,
 710                               gnutls_session_t client_session,
 711                               gnutls_session_t server_session) {
 712     size_t buffer_size;
 713
 714     struct pollfd fds[2];
 715     fds[0].fd      = client;
 716     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 717     fds[0].revents = 0;
 718     fds[1].fd      = server;
 719     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 720     fds[1].revents = 0;
 721
 722     /* Get maximum possible buffer size. */
 723     buffer_size = gnutls_record_get_max_size(client_session);
 724     if (gnutls_record_get_max_size(server_session) < buffer_size) {
 725         buffer_size = gnutls_record_get_max_size(server_session);
 726     }
 727     LOG(DEBUG2, "transfer_data_tls(): suggested buffer size: %zu",
 728                 buffer_size);
 729
 730     for (;;) {
 731         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 732         if (result < 0) {
 733             LOG_PERROR(ERROR, "transfer_data(): poll()");
 734             return;
 735         }
 736
 737         /* Data available from client. */
 738         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 739             if (read_from_write_to_tls(client_session, server_session,
 740                                        buffer_size) != 0) {
 741                 /* EOF (or other error) */
 742                 break;
 743             }
 744         }
 745         /* Data available from server. */
 746         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 747             if (read_from_write_to_tls(server_session, client_session,
 748                                        buffer_size) != 0) {
 749                 /* EOF (or other error) */
 750                 break;
 751             }
 752         }
 753
 754         /* Client closed connection. */
 755         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 756             break;
 757         }
 758         /* Server closed connection. */
 759         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 760             break;
 761         }
 762     }
 763 }
 764
 765 /* Read available data from session from and write to session to. */
 766 static int read_from_write_to_tls(gnutls_session_t from,
 767                                   gnutls_session_t to,
 768                                   size_t buffer_size) {
 769     ssize_t size_read;
 770     ssize_t size_written;
 771     char buffer[16384]; /* GnuTLS default maximum */
 772
 773     if (buffer_size > sizeof(buffer)) {
 774         LOG(WARNING, "read_from_write_to_tls(): reduced buffer size to %zu",
 775                      sizeof(buffer));
 776         buffer_size = sizeof(buffer);
 777     }
 778
 779     size_read = gnutls_record_recv(from, buffer, buffer_size);
 780     if (size_read < 0) {
 781         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_recv(): %s",
 782                      gnutls_strerror((int)size_read));
 783         return -1;
 784     /* EOF */
 785     } else if (size_read == 0) {
 786         return -1;
 787     }
 788
 789     size_written = gnutls_record_send(to, buffer, (size_t)size_read);
 790     if (size_written < 0) {
 791         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_send(): %s",
 792                      gnutls_strerror((int)size_written));
 793         return -1;
 794     }
 795     if (size_read != size_written) {
 796         LOG(ERROR, "read_from_write_to_tls(): only written %zu of %zu bytes!",
 797                    size_written, size_read);
 798         return -1;
 799     }
 800
 801     return 0;
 802 }
 803
 804
 805 static int connect_to_host(const char *hostname, const char *port) {
 806     struct addrinfo gai_hints;
 807     struct addrinfo *gai_result;
 808     int gai_return;
 809
 810     int server_socket;
 811     struct addrinfo *server;
 812
 813     if (hostname == NULL || port == NULL) {
 814         return -1;
 815     }
 816
 817     /* Get IP of hostname server. */
 818     memset(&gai_hints, 0, sizeof(gai_hints));
 819     gai_hints.ai_family   = AF_UNSPEC;
 820     gai_hints.ai_socktype = SOCK_STREAM;
 821     gai_hints.ai_protocol = 0;
 822     gai_hints.ai_flags    = AI_NUMERICSERV /* given port is numeric */
 823                           | AI_ADDRCONFIG  /* supported by this computer */
 824                           | AI_V4MAPPED;   /* support IPv4 through IPv6 */
 825     gai_return = getaddrinfo(hostname, port, &gai_hints, &gai_result);
 826     if (gai_return != 0) {
 827         if (gai_return == EAI_SYSTEM) {
 828             LOG_PERROR(WARNING, "connect_to_host(): getaddrinfo()");
 829         } else {
 830             LOG(WARNING, "connect_to_host(): getaddrinfo(): %s",
 831                          gai_strerror(gai_return));
 832         }
 833         return -1;
 834     }
 835
 836     /* Now try to connect to each server returned by getaddrinfo(), use the
 837      * first successful connect. */
 838     for (server = gai_result; server != NULL; server = server->ai_next) {
 839         server_socket = socket(server->ai_family,
 840                                server->ai_socktype,
 841                                server->ai_protocol);
 842         if (server_socket < 0) {
 843             LOG_PERROR(DEBUG1, "connect_to_host(): socket(), trying next");
 844             continue;
 845         }
 846
 847         if (connect(server_socket, server->ai_addr, server->ai_addrlen) == 0) {
 848             break;
 849         }
 850         LOG_PERROR(DEBUG1, "connect_to_host(): connect(), trying next");
 851
 852         close(server_socket);
 853     }
 854     /* Make sure we free the result from getaddrinfo(). */
 855     freeaddrinfo(gai_result);
 856
 857     if (server == NULL) {
 858         LOG_PERROR(WARNING, "connect_to_host(): no server found, abort");
 859         return -1;
 860     }
 861
 862     return server_socket;
 863 }
 864
 865
 866 /* Parse HTTP CONNECT request string and save its parameters.
 867  *
 868  * The following format is expected: "CONNECT host:port HTTP/1.x".
 869  *
 870  * request and host must have the same size! port must be at least 6 bytes
 871  * long (5 + '\0').
 872  */
 873 static int parse_request(const char *request, char *host, char *port,
 874                                               int *version_minor) {
 875     int port_unused; /* just used to verify the port is numeric */
 876     char *position;
 877
 878     /* scanf() doesn't check spaces. */
 879     if (strncmp(request, "CONNECT ", 8)) {
 880         return -1;
 881     }
 882     /* Check request and extract data, "host:port" is not yet separated. */
 883     if (sscanf(request, "CONNECT %s HTTP/1.%d", host, version_minor) != 2) {
 884         return -1;
 885     }
 886     /* Make sure ":port" is there. */
 887     if ((position = strchr(host, ':')) == NULL) {
 888         return -1;
 889     }
 890     /* Make sure port is numeric. */
 891     if (sscanf(position + 1, "%d", &port_unused) != 1) {
 892         return -1;
 893     }
 894     /* Store it in *port. */
 895     strncpy(port, position + 1, 5);
 896     port[5] = '\0';
 897     /* And remove port from host. */
 898     *position = '\0';
 899
 900     return 0;
 901 }
 902
 903
 904 static void log_session_information(gnutls_session_t session) {
 905     /* From doc/examples/ex-session-info.c of GnuTLS 3.2.3's tarball and
 906      * modified, thanks. */
 907
 908     const char *tmp;
 909     gnutls_credentials_type_t cred;
 910     gnutls_kx_algorithm_t kx;
 911     int dhe, ecdh;
 912
 913     dhe = 0;
 914     ecdh = 0;
 915
 916     /* Key exchange algorithm. */
 917     kx = gnutls_kx_get(session);
 918     LOG(DEBUG2, "- key exchange: %s", gnutls_kx_get_name(kx));
 919
 920     /* Authentication type. */
 921     cred = gnutls_auth_get_type(session);
 922     switch (cred) {
 923         case GNUTLS_CRD_CERTIFICATE:
 924             if (kx == GNUTLS_KX_DHE_RSA
 925                     || kx == GNUTLS_KX_DHE_DSS) {
 926                 dhe = 1;
 927 #ifdef GNUTLS_KX_ECDHE_RSA
 928             } else if (kx == GNUTLS_KX_ECDHE_RSA
 929                     || kx == GNUTLS_KX_ECDHE_ECDSA) {
 930                 ecdh = 1;
 931 #endif
 932             }
 933             break;
 934
 935         case GNUTLS_CRD_IA:
 936         case GNUTLS_CRD_SRP:
 937         case GNUTLS_CRD_PSK:
 938         case GNUTLS_CRD_ANON:
 939         default:
 940             /* This shouldn't occur. */
 941             LOG(WARNING, "unexpected authentication method: %d", cred);
 942             break;
 943     }
 944
 945     /* Information about key exchange. */
 946     if (dhe) {
 947         LOG(DEBUG2, "- ephemeral DH using prime of %d bits",
 948                     gnutls_dh_get_prime_bits(session));
 949     } else if (ecdh) {
 950 #ifdef GNUTLS_KX_ECDHE_RSA
 951         LOG(DEBUG2, "- ephemeral ECDH using curve %s",
 952                     gnutls_ecc_curve_get_name(gnutls_ecc_curve_get(session)));
 953 #endif
 954     }
 955
 956     tmp = gnutls_protocol_get_name(gnutls_protocol_get_version(session));
 957     LOG(DEBUG2, "- protocol: %s", tmp); /* e.g. TLS 1.0 */
 958
 959     tmp = gnutls_certificate_type_get_name(gnutls_certificate_type_get(session));
 960     LOG(DEBUG2, "- certificate type: %s", tmp);
 961
 962     tmp = gnutls_compression_get_name(gnutls_compression_get(session));
 963     LOG(DEBUG2, "- compression: %s", tmp);
 964
 965     tmp = gnutls_cipher_get_name(gnutls_cipher_get(session));
 966     LOG(DEBUG2, "- cipher: %s", tmp);
 967
 968     tmp = gnutls_mac_get_name(gnutls_mac_get(session));
 969     LOG(DEBUG2, "- MAC: %s", tmp);
 970 }