src/connection.c

   1 /*
   2  * Handle connections.
   3  *
   4  * Copyright (C) 2011  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 /* close() */
  25 #include <unistd.h>
  26 /* getaddrinfo() */
  27 #include <netdb.h>
  28 /* poll() */
  29 #include <poll.h>
  30 /* errno */
  31 #include <errno.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 4 times, first three are the error code (no %n$s!), the last is
  43  * the message. */
  44 #define HTTP_RESPONSE_FORMAT "HTTP/1.0 %s\r\n\
  45 Content-Type: text/html; charset=US-ASCII\r\n\
  46 \r\n\
  47 <!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">\n\
  48 <html>\n\
  49 <head><title>%s</title></head>\n\
  50 <body>\n\
  51 <h1>%s</h1>\n\
  52 <p>%s</p>\n\
  53 </body>\n\
  54 </html>\n"
  55
  56
  57 static int initialize_tls_session_client(int peer_socket,
  58         const char *hostname,
  59         gnutls_session_t *session,
  60         gnutls_certificate_credentials_t *x509_cred);
  61 static int initialize_tls_session_server(int peer_socket,
  62         gnutls_session_t *session,
  63         gnutls_certificate_credentials_t *x509_cred);
  64
  65 static int read_http_request(FILE *client_fd, char *request, size_t length);
  66 static void send_bad_request(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, *server_fd;
  87
  88     char buffer[MAX_REQUEST_LINE];
  89     char host[MAX_REQUEST_LINE];
  90     char port[5 + 1];
  91
  92     int version_minor; /* 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(LOG_DEBUG, "new connection");
 110
 111     server_socket = -1;
 112     client_fd = NULL;
 113     server_fd = NULL;
 114     client_session_init = 0;
 115     server_session_init = 0;
 116     client_session_started = 0;
 117     server_session_started = 0;
 118     validation_failed = 0;
 119
 120     client_fd = fdopen(client_socket, "a+");
 121     if (NULL == client_fd) {
 122         LOG_PERROR(LOG_WARNING, "fdopen(): client failed");
 123         goto out;
 124     }
 125
 126     /* Read request line (CONNECT ..) and headers (they are discarded). */
 127     result = read_http_request(client_fd, buffer, sizeof(buffer));
 128     if (-1 == result) {
 129         /* Read error. */
 130         LOG(LOG_WARNING, "read_http_request(): client read error");
 131         goto out;
 132     } else if (-2 == result) {
 133         /* EOF */
 134         LOG(LOG_WARNING, "read_http_request(): client EOF");
 135         send_bad_request(client_fd);
 136         goto out;
 137     }
 138
 139     if (0 != parse_request(buffer, host, port, &version_minor)) {
 140         LOG(LOG_WARNING, "bad request: %s", buffer);
 141         send_bad_request(client_fd);
 142         goto out;
 143     }
 144
 145     LOG(LOG_DEBUG, "target: %s:%s (HTTP 1.%d)", host, port, version_minor);
 146
 147     /* Connect to proxy server or directly to server. */
 148     if (NULL != global_proxy_host && NULL != global_proxy_port) {
 149         LOG(LOG_DEBUG, "connecting to %s:%s", global_proxy_host,
 150                                               global_proxy_port);
 151         server_socket = connect_to_host(global_proxy_host, global_proxy_port);
 152     } else {
 153         LOG(LOG_DEBUG, "connecting to %s:%s", host, port);
 154         server_socket = connect_to_host(host, port);
 155     }
 156
 157     if (-1 == server_socket) {
 158         LOG(LOG_WARNING, "failed to connect to server");
 159         send_forwarding_failure(client_fd);
 160         goto out;
 161     }
 162     server_fd = fdopen(server_socket, "a+");
 163     if (NULL == server_fd) {
 164         LOG_PERROR(LOG_WARNING, "fdopen(): server failed");
 165         send_forwarding_failure(client_fd);
 166         goto out;
 167     }
 168
 169     /* Connect to proxy if requested (command line option). */
 170     if (NULL != global_proxy_host && NULL != global_proxy_port) {
 171         fprintf(server_fd, "CONNECT %s:%s HTTP/1.0\r\n", host, port);
 172         fprintf(server_fd, "\r\n");
 173
 174         /* Read response line from proxy server. */
 175         result = read_http_request(server_fd, buffer, sizeof(buffer));
 176         if (-1 == result) {
 177             /* Read error. */
 178             LOG(LOG_WARNING, "read_http_request(): proxy read error");
 179             send_forwarding_failure(client_fd);
 180             goto out;
 181         } else if (-2 == result) {
 182             /* EOF */
 183             LOG(LOG_WARNING, "read_http_request(): proxy EOF");
 184             send_forwarding_failure(client_fd);
 185             goto out;
 186         }
 187
 188         /* Check response of proxy server. */
 189         if (0 != strncmp(buffer, "HTTP/1.0 200", 12)) {
 190             LOG(LOG_WARNING, "bad proxy response: %s", buffer);
 191             send_forwarding_failure(client_fd);
 192             goto out;
 193         }
 194     }
 195
 196     LOG(LOG_DEBUG, "connection to server established");
 197
 198     /* If the -u option is used and we don't know this hostname's server
 199      * certificate then just pass through the connection and let the client
 200      * verify the server certificate. */
 201     if (global_passthrough_unknown) {
 202         char path[1024];
 203         FILE *file = NULL;
 204
 205         if (-2 == server_certificate_path(&file, host, path, sizeof(path))) {
 206             /* We've established a connection, tell the client. */
 207             fprintf(client_fd, "HTTP/1.0 200 Connection established\r\n");
 208             fprintf(client_fd, "\r\n");
 209             fflush(client_fd);
 210
 211             LOG(LOG_DEBUG, "transferring data");
 212
 213             /* Proxy data between client and server until one side is done
 214              * (EOF or error). */
 215             transfer_data(client_socket, server_socket);
 216
 217             LOG(LOG_DEBUG, "finished transferring data");
 218
 219             goto out;
 220         }
 221         /* server_certificate_path() may have opened the file, close it. */
 222         if (NULL != file) {
 223             fclose(file);
 224         }
 225     }
 226
 227     /* Initialize TLS client credentials to talk to the server. */
 228     result = initialize_tls_session_server(server_socket, &server_session,
 229                                                           &server_x509_cred);
 230     if (0 != result) {
 231         LOG(LOG_WARNING, "initialize_tls_session_server() failed");
 232         send_forwarding_failure(client_fd);
 233         goto out;
 234     }
 235     server_session_init = 1;
 236
 237     LOG(LOG_DEBUG, "starting server TLS handshake");
 238
 239     /* Try to establish TLS handshake between us and server. */
 240     result = gnutls_handshake(server_session);
 241     if (GNUTLS_E_SUCCESS != result) {
 242         LOG(LOG_WARNING, "server TLS handshake failed: %s",
 243                          gnutls_strerror(result));
 244         send_forwarding_failure(client_fd);
 245         goto out;
 246     }
 247     server_session_started = 1;
 248
 249     LOG(LOG_DEBUG, "server TLS handshake finished");
 250
 251     /* Make sure the server certificate is valid and known. */
 252     if (0 != verify_tls_connection(server_session, host)) {
 253         LOG(LOG_ERROR, "server certificate validation failed!");
 254         /* We send the error message over our TLS connection to the client,
 255          * but with an invalid certificate. No data is transfered from/to the
 256          * target server. */
 257         validation_failed = 1;
 258     }
 259
 260     /* Initialize TLS server credentials to talk to the client. */
 261     result = initialize_tls_session_client(client_socket,
 262                                            /* use a special host if the server
 263                                             * certificate was invalid */
 264                                            (validation_failed) ? "invalid"
 265                                                                : host,
 266                                            &client_session,
 267                                            &client_x509_cred);
 268     if (0 != result) {
 269         LOG(LOG_WARNING, "initialize_tls_session_client() failed");
 270         send_forwarding_failure(client_fd);
 271         goto out;
 272     }
 273     client_session_init = 1;
 274
 275     /* We've established a connection, tell the client. */
 276     fprintf(client_fd, "HTTP/1.0 200 Connection established\r\n");
 277     fprintf(client_fd, "\r\n");
 278     fflush(client_fd);
 279
 280     LOG(LOG_DEBUG, "starting client TLS handshake");
 281
 282     /* Try to establish TLS handshake between client and us. */
 283     result = gnutls_handshake(client_session);
 284     if (GNUTLS_E_SUCCESS != result) {
 285         LOG(LOG_WARNING, "client TLS handshake failed: %s",
 286                          gnutls_strerror(result));
 287         send_forwarding_failure(client_fd);
 288         goto out;
 289     }
 290     client_session_started = 1;
 291
 292     LOG(LOG_DEBUG, "client TLS handshake finished");
 293
 294     /* Tell the client that the verification failed. Shouldn't be necessary as
 295      * the client should terminate the connection because he received the
 296      * invalid certificate but better be sure. */
 297     if (validation_failed) {
 298         tls_send_invalid_cert_message(client_session);
 299         goto out;
 300     }
 301
 302     LOG(LOG_DEBUG, "transferring TLS data");
 303
 304     /* Proxy data between client and server until one side is done (EOF or
 305      * error). */
 306     transfer_data_tls(client_socket, server_socket,
 307                       client_session, server_session);
 308
 309     LOG(LOG_DEBUG, "finished transferring TLS data");
 310
 311 out:
 312     /* Close TLS sessions if necessary. Use GNUTLS_SHUT_RDWR so the data is
 313      * reliable transmitted. */
 314     if (0 != server_session_started) {
 315         gnutls_bye(server_session, GNUTLS_SHUT_RDWR);
 316     }
 317     if (0 != client_session_started) {
 318         gnutls_bye(client_session, GNUTLS_SHUT_RDWR);
 319     }
 320     if (0 != server_session_init) {
 321         gnutls_deinit(server_session);
 322         gnutls_certificate_free_credentials(server_x509_cred);
 323     }
 324     if (0 != client_session_init) {
 325         gnutls_deinit(client_session);
 326         gnutls_certificate_free_cas(client_x509_cred);
 327         gnutls_certificate_free_keys(client_x509_cred);
 328         gnutls_certificate_free_credentials(client_x509_cred);
 329     }
 330
 331     /* Close connection to server/proxy. */
 332     if (NULL != server_fd) {
 333         fclose(server_fd);
 334     } else if (-1 != server_socket) {
 335         close(server_socket);
 336     }
 337     LOG(LOG_DEBUG, "connection to server closed");
 338     /* Close connection to client. */
 339     if (NULL != client_fd) {
 340         fclose(client_fd);
 341     } else {
 342         close(client_socket);
 343     }
 344     LOG(LOG_DEBUG, "connection to client closed");
 345
 346     LOG(LOG_DEBUG, "connection finished");
 347 }
 348
 349
 350 static int initialize_tls_session_client(int peer_socket,
 351         const char *hostname,
 352         gnutls_session_t *session,
 353         gnutls_certificate_credentials_t *x509_cred) {
 354     int result;
 355     int use_invalid_cert;
 356     char path[1024];
 357
 358     /* The "invalid" hostname is special. If it's used we send an invalid
 359      * certificate to let the client know something is wrong. */
 360     use_invalid_cert = 0 == strcmp(hostname, "invalid");
 361
 362     /* Hostname too long. */
 363     if (sizeof(path) - strlen(PROXY_SERVER_CERT_FORMAT) <= strlen(hostname)) {
 364         LOG(LOG_WARNING,
 365             "initialize_tls_session_client(): hostname too long: '%s'",
 366             hostname);
 367         return -1;
 368     }
 369     /* Try to prevent path traversals in hostnames. */
 370     if (NULL != strstr(hostname, "..")) {
 371         LOG(LOG_WARNING,
 372             "initialize_tls_session_client(): possible path traversal: '%s'",
 373             hostname);
 374         return -1;
 375     }
 376     result = snprintf(path, sizeof(path), PROXY_SERVER_CERT_FORMAT, hostname);
 377     if (result < 0) {
 378         LOG_PERROR(LOG_ERROR,
 379                    "initialize_tls_session_client(): snprintf failed");
 380         return -1;
 381     } else if ((size_t)result >= sizeof(path)) {
 382         LOG(LOG_ERROR,
 383             "initialize_tls_session_client(): snprintf buffer too short");
 384         return -1;
 385     }
 386
 387     result = gnutls_certificate_allocate_credentials(x509_cred);
 388     if (GNUTLS_E_SUCCESS != result) {
 389         LOG(LOG_ERROR,
 390             "initialize_tls_session_client(): \
 391 gnutls_certificate_allocate_credentials(): %s",
 392             gnutls_strerror(result));
 393         return -1;
 394     }
 395
 396     /* Load proxy CA file, this CA "list" is send to the client. */
 397     if (!use_invalid_cert) {
 398         result = gnutls_certificate_set_x509_trust_file(*x509_cred,
 399                                                         PROXY_CA_FILE,
 400                                                         GNUTLS_X509_FMT_PEM);
 401         if (0 >= result) {
 402             LOG(LOG_ERROR,
 403                 "initialize_tls_session_client(): can't read CA file: '%s'",
 404                 PROXY_CA_FILE);
 405             gnutls_certificate_free_credentials(*x509_cred);
 406             return -1;
 407         }
 408     }
 409     /* If the invalid hostname was specified do nothing, we use a self-signed
 410      * certificate in this case. */
 411
 412     /* And certificate for this website and proxy's private key. */
 413     if (!use_invalid_cert) {
 414         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 415                                                       path, PROXY_KEY_FILE,
 416                                                       GNUTLS_X509_FMT_PEM);
 417     /* If the invalid hostname was specified load our special "invalid"
 418      * certificate. */
 419     } else {
 420         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 421                                                       PROXY_INVALID_CERT_FILE,
 422                                                       PROXY_KEY_FILE,
 423                                                       GNUTLS_X509_FMT_PEM);
 424     }
 425     if (GNUTLS_E_SUCCESS != result) {
 426         LOG(LOG_ERROR,
 427             "initialize_tls_session_client(): \
 428 can't read server certificate ('%s') or key file ('%s'): %s",
 429             path, PROXY_KEY_FILE, gnutls_strerror(result));
 430         gnutls_certificate_free_credentials(*x509_cred);
 431         /* Could be a missing certificate. */
 432         return -2;
 433     }
 434
 435     gnutls_certificate_set_dh_params(*x509_cred, global_tls_dh_params);
 436
 437     result = gnutls_init(session, GNUTLS_SERVER);
 438     if (GNUTLS_E_SUCCESS != result) {
 439         LOG(LOG_ERROR,
 440             "initialize_tls_session_client(): gnutls_init(): %s",
 441             gnutls_strerror(result));
 442         gnutls_certificate_free_credentials(*x509_cred);
 443         return -1;
 444     }
 445     result = gnutls_priority_set(*session, global_tls_priority_cache);
 446     if (GNUTLS_E_SUCCESS != result) {
 447         LOG(LOG_ERROR,
 448             "initialize_tls_session_client(): gnutls_priority_set(): %s",
 449             gnutls_strerror(result));
 450         gnutls_deinit(*session);
 451         gnutls_certificate_free_credentials(*x509_cred);
 452         return -1;
 453     }
 454     result = gnutls_credentials_set(*session,
 455                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 456     if (GNUTLS_E_SUCCESS != result) {
 457         LOG(LOG_ERROR,
 458             "initialize_tls_session_client(): gnutls_credentials_set(): %s",
 459             gnutls_strerror(result));
 460         gnutls_deinit(*session);
 461         gnutls_certificate_free_credentials(*x509_cred);
 462         return -1;
 463     }
 464
 465     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 466
 467     return 0;
 468 }
 469 static int initialize_tls_session_server(int peer_socket,
 470         gnutls_session_t *session,
 471         gnutls_certificate_credentials_t *x509_cred) {
 472     int result;
 473
 474     result = gnutls_certificate_allocate_credentials(x509_cred);
 475     if (GNUTLS_E_SUCCESS != result) {
 476         LOG(LOG_ERROR,
 477             "initialize_tls_session_server(): \
 478 gnutls_certificate_allocate_credentials(): %s",
 479             gnutls_strerror(result));
 480         return -1;
 481     }
 482
 483     result = gnutls_init(session, GNUTLS_CLIENT);
 484     if (GNUTLS_E_SUCCESS != result) {
 485         LOG(LOG_ERROR,
 486             "initialize_tls_session_server(): gnutls_init(): %s",
 487             gnutls_strerror(result));
 488         gnutls_certificate_free_credentials(*x509_cred);
 489         return -1;
 490     }
 491     gnutls_priority_set(*session, global_tls_priority_cache);
 492     if (GNUTLS_E_SUCCESS != result) {
 493         LOG(LOG_ERROR,
 494             "initialize_tls_session_server(): gnutls_priority_set(): %s",
 495             gnutls_strerror(result));
 496         gnutls_deinit(*session);
 497         gnutls_certificate_free_credentials(*x509_cred);
 498         return -1;
 499     }
 500     result = gnutls_credentials_set(*session,
 501                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 502     if (GNUTLS_E_SUCCESS != result) {
 503         LOG(LOG_ERROR,
 504             "initialize_tls_session_server(): gnutls_credentials_set(): %s",
 505             gnutls_strerror(result));
 506         gnutls_deinit(*session);
 507         gnutls_certificate_free_credentials(*x509_cred);
 508         return -1;
 509     }
 510
 511     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 512
 513     return 0;
 514 }
 515
 516
 517 /* Read HTTP request line and headers (ignored).
 518  *
 519  * On success 0 is returned, -1 on client error, -2 on unexpected EOF.
 520  */
 521 static int read_http_request(FILE *client_fd, char *request, size_t length) {
 522     char buffer[MAX_REQUEST_LINE];
 523
 524     if (NULL == fgets(request, (int)length, client_fd)) {
 525         if (ferror(client_fd)) {
 526             LOG_PERROR(LOG_WARNING, "read_http_request(): fgets()");
 527             return -1;
 528         }
 529
 530         return -2;
 531     }
 532
 533     while (NULL != fgets(buffer, MAX_REQUEST_LINE, client_fd)) {
 534         /* End of header. */
 535         if (0 == strcmp(buffer, "\n") || 0 == strcmp(buffer, "\r\n")) {
 536             break;
 537         }
 538     }
 539     if (ferror(client_fd)) {
 540         LOG_PERROR(LOG_WARNING, "read_http_request(): fgets()");
 541         return -1;
 542     }
 543
 544     return 0;
 545 }
 546
 547 static void send_bad_request(FILE *client_fd) {
 548 #define RESPONSE_ERROR "400 Bad Request"
 549 #define RESPONSE_MSG   "Your browser sent an invalid request."
 550     fprintf(client_fd, HTTP_RESPONSE_FORMAT,
 551                        RESPONSE_ERROR, RESPONSE_ERROR, RESPONSE_ERROR,
 552                        RESPONSE_MSG);
 553 #undef RESPONSE_ERROR
 554 #undef RESPONSE_MSG
 555 }
 556 static void send_forwarding_failure(FILE *client_fd) {
 557 #define RESPONSE_ERROR "503 Forwarding failure"
 558 #define RESPONSE_MSG   "Failed to connect to server, check logs."
 559     fprintf(client_fd, HTTP_RESPONSE_FORMAT,
 560                        RESPONSE_ERROR, RESPONSE_ERROR, RESPONSE_ERROR,
 561                        RESPONSE_MSG);
 562 #undef RESPONSE_ERROR
 563 #undef RESPONSE_MSG
 564 }
 565 static void tls_send_invalid_cert_message(gnutls_session_t session) {
 566 #define RESPONSE_ERROR "500 Internal Server Error"
 567 #define RESPONSE_MSG   "Server certificate validation failed, check logs."
 568
 569     int result;
 570     char buffer[sizeof(HTTP_RESPONSE_FORMAT) - 1 /* '\0' */
 571                                              - 4 * 2 /* four %s */
 572                 + (sizeof(RESPONSE_ERROR) - 1 /* '\0' */) * 3
 573                 + sizeof(RESPONSE_MSG)    - 1 /* '\0' */
 574                 + 1 /* '\0' */];
 575
 576     result = snprintf(buffer, sizeof(buffer),
 577                       HTTP_RESPONSE_FORMAT,
 578                       RESPONSE_ERROR, RESPONSE_ERROR, RESPONSE_ERROR,
 579                       RESPONSE_MSG);
 580     if (result < 0) {
 581         LOG_PERROR(LOG_ERROR,
 582                    "tls_send_invalid_cert_message(): snprintf failed");
 583         return;
 584     } else if ((size_t)result >= sizeof(buffer)) {
 585         LOG(LOG_ERROR,
 586             "tls_send_invalid_cert_message(): snprintf buffer too short");
 587         return;
 588     }
 589
 590     gnutls_record_send(session, buffer, sizeof(buffer) - 1);
 591                                         /* don't send trailing '\0' */
 592 #undef RESPONSE_ERROR
 593 #undef RESPONSE_MSG
 594 }
 595
 596
 597 /* Transfer data between client and server sockets until one closes the
 598  * connection. */
 599 static void transfer_data(int client, int server) {
 600     struct pollfd fds[2];
 601     fds[0].fd      = client;
 602     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 603     fds[0].revents = 0;
 604     fds[1].fd      = server;
 605     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 606     fds[1].revents = 0;
 607
 608     for (;;) {
 609         int result = poll(fds, 2, -1 /* no timeout */);
 610         if (result < 0) {
 611             LOG_PERROR(LOG_ERROR, "transfer_data(): poll()");
 612             return;
 613         }
 614
 615         /* Data available from client. */
 616         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 617             if (0 != read_from_write_to(client, server)) {
 618                 /* EOF (or other error) */
 619                 break;
 620             }
 621         }
 622         /* Data available from server. */
 623         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 624             if (0 != read_from_write_to(server, client)) {
 625                 /* EOF (or other error) */
 626                 break;
 627             }
 628         }
 629
 630         /* Client closed connection. */
 631         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 632             break;
 633         }
 634         /* Server closed connection. */
 635         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 636             break;
 637         }
 638     }
 639 }
 640
 641 /* Read available data from socket from and write it to socket to. At maximum
 642  * 4096 bytes are read/written. */
 643 static int read_from_write_to(int from, int to) {
 644     ssize_t size_read;
 645     ssize_t size_written;
 646     char buffer[4096];
 647
 648     LOG(LOG_DEBUG, "read_from_write_to(): %d -> %d", from, to);
 649
 650     size_read = read(from, buffer, sizeof(buffer));
 651     if (0 > size_read) {
 652         LOG_PERROR(LOG_WARNING, "read_from_write_to(): read()");
 653         return -1;
 654     }
 655     /* EOF */
 656     if (0 == size_read) {
 657         return -1;
 658     }
 659
 660     size_written = write(to, buffer, (size_t)size_read);
 661     if (0 > size_written) {
 662         LOG_PERROR(LOG_WARNING, "read_from_write_to(): write()");
 663         return -1;
 664     }
 665     if (size_read != size_written) {
 666         LOG(LOG_ERROR, "read_from_write_to(): only written %ld of %ld bytes!",
 667                        (long int)size_written, (long int)size_read);
 668         return -1;
 669     }
 670
 671     return 0;
 672 }
 673
 674 /* Transfer data between client and server TLS connection until one closes the
 675  * connection. */
 676 static void transfer_data_tls(int client, int server,
 677                               gnutls_session_t client_session,
 678                               gnutls_session_t server_session) {
 679     size_t buffer_size;
 680
 681     struct pollfd fds[2];
 682     fds[0].fd      = client;
 683     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 684     fds[0].revents = 0;
 685     fds[1].fd      = server;
 686     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 687     fds[1].revents = 0;
 688
 689     /* Get maximum possible buffer size. */
 690     buffer_size = gnutls_record_get_max_size(client_session);
 691     LOG(LOG_DEBUG, "transfer_data_tls(): suggested buffer size: %ld",
 692                    (long int)buffer_size);
 693     if (buffer_size > gnutls_record_get_max_size(server_session)) {
 694         buffer_size = gnutls_record_get_max_size(server_session);
 695     }
 696
 697     for (;;) {
 698         int result = poll(fds, 2, -1 /* no timeout */);
 699         if (result < 0) {
 700             LOG_PERROR(LOG_ERROR, "transfer_data(): poll()");
 701             return;
 702         }
 703
 704         /* Data available from client. */
 705         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 706             if (0 != read_from_write_to_tls(client_session, server_session,
 707                                             buffer_size)) {
 708                 /* EOF (or other error) */
 709                 break;
 710             }
 711         }
 712         /* Data available from server. */
 713         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 714             if (0 != read_from_write_to_tls(server_session, client_session,
 715                                             buffer_size)) {
 716                 /* EOF (or other error) */
 717                 break;
 718             }
 719         }
 720
 721         /* Client closed connection. */
 722         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 723             break;
 724         }
 725         /* Server closed connection. */
 726         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 727             break;
 728         }
 729     }
 730 }
 731
 732 /* Read available data from session from and write to session to. */
 733 static int read_from_write_to_tls(gnutls_session_t from,
 734                                   gnutls_session_t to,
 735                                   size_t buffer_size) {
 736     ssize_t size_read;
 737     ssize_t size_written;
 738     char buffer[16384];
 739
 740     if (buffer_size > sizeof(buffer)) {
 741         buffer_size = sizeof(buffer);
 742     }
 743     LOG(LOG_DEBUG, "read_from_write_to_tls(): used buffer size: %ld",
 744                    (long int)buffer_size);
 745
 746     size_read = gnutls_record_recv(from, buffer, buffer_size);
 747     if (0 > size_read) {
 748         LOG(LOG_WARNING, "read_from_write_to_tls(): gnutls_record_recv(): %s",
 749                          gnutls_strerror((int)size_read));
 750         return -1;
 751     }
 752     /* EOF */
 753     if (0 == size_read) {
 754         return -1;
 755     }
 756
 757     size_written = gnutls_record_send(to, buffer, (size_t)size_read);
 758     if (0 > size_written) {
 759         LOG(LOG_WARNING, "read_from_write_to_tls(): gnutls_record_send(): %s",
 760                          gnutls_strerror((int)size_written));
 761         return -1;
 762     }
 763     if (size_read != size_written) {
 764         LOG(LOG_ERROR, "read_from_write_to_tls(): only written %ld of %ld bytes!",
 765                        (long int)size_written, (long int)size_read);
 766         return -1;
 767     }
 768
 769     return 0;
 770 }
 771
 772
 773 static int connect_to_host(const char *hostname, const char *port) {
 774     struct addrinfo gai_hints;
 775     struct addrinfo *gai_result;
 776     int gai_return;
 777
 778     int server_socket;
 779     struct addrinfo *server;
 780
 781     if (NULL == hostname || NULL == port) {
 782         return -1;
 783     }
 784
 785     /* Get IP of hostname server. */
 786     memset(&gai_hints, 0, sizeof(gai_hints));
 787     gai_hints.ai_family   = AF_UNSPEC;
 788     gai_hints.ai_socktype = SOCK_STREAM;
 789     gai_hints.ai_protocol = 0;
 790     gai_hints.ai_flags    = AI_NUMERICSERV /* given port is numeric */
 791                           | AI_ADDRCONFIG  /* supported by this computer */
 792                           | AI_V4MAPPED;   /* support IPv4 through IPv6 */
 793     gai_return = getaddrinfo(hostname, port, &gai_hints, &gai_result);
 794     if (0 != gai_return) {
 795         LOG_PERROR(LOG_WARNING, "connect_to_host(): getaddrinfo()");
 796         return -1;
 797     }
 798
 799     /* Now try to connect to each server returned by getaddrinfo(), use the
 800      * first successful connect. */
 801     for (server = gai_result; NULL != server; server = server->ai_next) {
 802         server_socket = socket(server->ai_family,
 803                                server->ai_socktype,
 804                                server->ai_protocol);
 805         if (-1 == server_socket) {
 806             LOG_PERROR(LOG_DEBUG, "connect_to_host(): socket(), trying next");
 807             continue;
 808         }
 809
 810         if (-1 != connect(server_socket, server->ai_addr,
 811                                          server->ai_addrlen)) {
 812             break;
 813         }
 814         LOG_PERROR(LOG_DEBUG, "connect_to_host(): connect(), trying next");
 815
 816         close(server_socket);
 817     }
 818     /* Make sure we free the result from getaddrinfo(). */
 819     freeaddrinfo(gai_result);
 820
 821     if (NULL == server) {
 822         LOG_PERROR(LOG_WARNING, "connect_to_host(): no server found, abort");
 823         return -1;
 824     }
 825
 826     return server_socket;
 827 }
 828
 829
 830 /* Parse HTTP CONNECT request string and save its parameters.
 831  *
 832  * The following format is expected: "CONNECT host:port HTTP/1.x".
 833  *
 834  * request and host must have the same size! port must be at least 6 bytes
 835  * long (5 + '\0').
 836  */
 837 static int parse_request(const char *request, char *host, char *port,
 838                                               int *version_minor) {
 839     int port_unused; /* just used to verify the port is numeric */
 840     char *position;
 841
 842     /* scanf() doesn't check spaces. */
 843     if (0 != strncmp(request, "CONNECT ", 8)) {
 844         return -1;
 845     }
 846     /* Check request and extract data, "host:port" is not yet separated. */
 847     if (2 != sscanf(request, "CONNECT %s HTTP/1.%d",
 848                              host, version_minor)) {
 849         return -1;
 850     }
 851     /* Make sure ":port" is there. */
 852     if (NULL == (position = strchr(host, ':'))) {
 853         return -1;
 854     }
 855     /* Make sure port is numeric. */
 856     if (1 != sscanf(position + 1, "%d", &port_unused)) {
 857         return -1;
 858     }
 859     /* Store it in *port. */
 860     strncpy(port, position + 1, 5);
 861     port[5] = '\0';
 862     /* And remove port from host. */
 863     *position = '\0';
 864
 865     return 0;
 866 }