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 <netdb.h>
  27 #include <poll.h>
  28 #include <unistd.h>
  29
  30
  31 /* Maximum length of a HTTP request line. Longer request lines are aborted
  32  * with an error. The standard doesn't specify a maximum line length but this
  33  * should be a good limit to make processing simpler. As HTTPS is used this
  34  * doesn't limit long GET requests. */
  35 #define MAX_REQUEST_LINE 4096
  36
  37 /* Format string used to send HTTP/1.0 error responses to the client.
  38  *
  39  * %s is used 5 times, first is the error code, then additional headers, next
  40  * two are the error code (no %n$s!), the last is the message. */
  41 #define HTTP_RESPONSE_FORMAT "HTTP/1.0 %s\r\n\
  42 Content-Type: text/html; charset=US-ASCII\r\n\
  43 %s\r\n\
  44 <!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">\n\
  45 <html>\n\
  46 <head><title>%s</title></head>\n\
  47 <body>\n\
  48 <h1>%s</h1>\n\
  49 <p>%s</p>\n\
  50 </body>\n\
  51 </html>\n"
  52
  53
  54 static int initialize_tls_session_client(int peer_socket,
  55         const char *hostname,
  56         gnutls_session_t *session,
  57         gnutls_certificate_credentials_t *x509_cred);
  58 static int initialize_tls_session_server(int peer_socket,
  59         gnutls_session_t *session,
  60         gnutls_certificate_credentials_t *x509_cred);
  61
  62 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd);
  63 static int read_http_request(FILE *client_fd, char *request, size_t length);
  64 static void send_bad_request(FILE *client_fd);
  65 static void send_authentication_required(FILE *client_fd);
  66 static void send_forwarding_failure(FILE *client_fd);
  67 static void tls_send_invalid_cert_message(gnutls_session_t session);
  68
  69 static void transfer_data(int client, int server);
  70 static int read_from_write_to(int from, int to);
  71 static void transfer_data_tls(int client, int server,
  72                               gnutls_session_t client_session,
  73                               gnutls_session_t server_session);
  74 static int read_from_write_to_tls(gnutls_session_t from, gnutls_session_t to,
  75                                   size_t buffer_size);
  76
  77 static int connect_to_host(const char *hostname, const char *port);
  78
  79 static int parse_request(const char *buffer, char *host, char *port,
  80                                              int *version_minor);
  81
  82
  83 void handle_connection(int client_socket) {
  84     int server_socket;
  85     FILE *client_fd_read, *client_fd_write, *server_fd_read, *server_fd_write;
  86
  87     char buffer[MAX_REQUEST_LINE];
  88     char host[MAX_REQUEST_LINE];
  89     char port[5 + 1];
  90
  91     int version_minor; /* x in HTTP/1.x */
  92     int result;
  93
  94     /* client_x509_cred is used when talking to the client (acting as a TSL
  95      * server), server_x509_cred is used when talking to the server (acting as
  96      * a TSL client). */
  97     gnutls_certificate_credentials_t client_x509_cred, server_x509_cred;
  98
  99     gnutls_session_t client_session, server_session;
 100     /* initialize_tls_session_*() called? - used for goto out */
 101     int client_session_init, server_session_init;
 102     /* gnutls_handshake() called? - used for goto out */
 103     int client_session_started, server_session_started;
 104     /* Validation failed? If yes we need to send the special "invalid"
 105      * certificate. */
 106     int validation_failed;
 107
 108     LOG(DEBUG, "new connection");
 109
 110     server_socket = -1;
 111     client_fd_read = NULL;
 112     client_fd_write = NULL;
 113     server_fd_read = NULL;
 114     server_fd_write = NULL;
 115     client_session_init = 0;
 116     server_session_init = 0;
 117     client_session_started = 0;
 118     server_session_started = 0;
 119     validation_failed = 0;
 120
 121     if (fdopen_read_write(client_socket, &client_fd_read,
 122                                          &client_fd_write) != 0) {
 123         goto out;
 124     }
 125
 126     /* Read request line (CONNECT ..) and headers (they are discarded). */
 127     result = read_http_request(client_fd_read, buffer, sizeof(buffer));
 128     if (result == -1) {
 129         LOG(WARNING, "read_http_request(): client read error");
 130         goto out;
 131     } else if (result == -2) {
 132         LOG(WARNING, "read_http_request(): client EOF");
 133         send_bad_request(client_fd_write);
 134         goto out;
 135     } else if (result == -3) {
 136         LOG(DEBUG, "read_http_request(): proxy authentication failed");
 137         send_authentication_required(client_fd_write);
 138         goto out;
 139     }
 140
 141     if (parse_request(buffer, host, port, &version_minor) != 0) {
 142         LOG(WARNING, "bad request: %s", buffer);
 143         send_bad_request(client_fd_write);
 144         goto out;
 145     }
 146
 147     LOG(DEBUG, "target: %s:%s (HTTP 1.%d)", host, port, version_minor);
 148
 149     /* Connect to proxy server or directly to server. */
 150     if (global_proxy_host != NULL && global_proxy_port != NULL) {
 151         LOG(DEBUG, "connecting to %s:%s", global_proxy_host,
 152                                               global_proxy_port);
 153         server_socket = connect_to_host(global_proxy_host, global_proxy_port);
 154     } else {
 155         LOG(DEBUG, "connecting to %s:%s", host, port);
 156         server_socket = connect_to_host(host, port);
 157     }
 158
 159     if (server_socket < 0) {
 160         LOG(WARNING, "failed to connect to server");
 161         send_forwarding_failure(client_fd_write);
 162         goto out;
 163     }
 164     if (fdopen_read_write(server_socket, &server_fd_read,
 165                                          &server_fd_write) != 0) {
 166         send_forwarding_failure(client_fd_write);
 167         goto out;
 168     }
 169
 170     /* Connect to proxy if requested (command line option). */
 171     if (global_proxy_host != NULL && global_proxy_port != NULL) {
 172         fprintf(server_fd_write, "CONNECT %s:%s HTTP/1.0\r\n", host, port);
 173         fprintf(server_fd_write, "\r\n");
 174         fflush(server_fd_write);
 175
 176         /* Read response line from proxy server. */
 177         result = read_http_request(server_fd_read, buffer, sizeof(buffer));
 178         if (result == -1) {
 179             LOG(WARNING, "read_http_request(): proxy read error");
 180             send_forwarding_failure(client_fd_write);
 181             goto out;
 182         } else if (result == -2) {
 183             LOG(WARNING, "read_http_request(): proxy EOF");
 184             send_forwarding_failure(client_fd_write);
 185             goto out;
 186         }
 187
 188         /* Check response of proxy server. */
 189         if (strncmp(buffer, "HTTP/1.0 200", 12)) {
 190             LOG(WARNING, "bad proxy response: %s", buffer);
 191             send_forwarding_failure(client_fd_write);
 192             goto out;
 193         }
 194     }
 195
 196     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[TLSPROXY_MAX_PATH_LENGTH];
 203         FILE *file = NULL;
 204
 205         if (server_certificate_file(&file, host, path, sizeof(path)) == -2) {
 206             /* We've established a connection, tell the client. */
 207             fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
 208             fprintf(client_fd_write, "\r\n");
 209             fflush(client_fd_write);
 210
 211             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(DEBUG, "finished transferring data");
 218
 219             goto out;
 220         }
 221         /* server_certificate_file() may have opened the file, close it. */
 222         if (file != NULL) {
 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 (result != 0) {
 231         LOG(WARNING, "initialize_tls_session_server() failed");
 232         send_forwarding_failure(client_fd_write);
 233         goto out;
 234     }
 235     server_session_init = 1;
 236
 237     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 (result != GNUTLS_E_SUCCESS) {
 242         LOG(WARNING, "server TLS handshake failed: %s",
 243                          gnutls_strerror(result));
 244         send_forwarding_failure(client_fd_write);
 245         goto out;
 246     }
 247     server_session_started = 1;
 248
 249     LOG(DEBUG, "server TLS handshake finished");
 250
 251     /* Make sure the server certificate is valid and known. */
 252     if (verify_tls_connection(server_session, host) != 0) {
 253         LOG(ERROR, "server certificate validation failed!");
 254         /* We'll 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 (result != 0) {
 269         LOG(WARNING, "initialize_tls_session_client() failed");
 270         send_forwarding_failure(client_fd_write);
 271         goto out;
 272     }
 273     client_session_init = 1;
 274
 275     /* We've established a connection, tell the client. */
 276     fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
 277     fprintf(client_fd_write, "\r\n");
 278     fflush(client_fd_write);
 279
 280     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 (result != GNUTLS_E_SUCCESS) {
 285         LOG(WARNING, "client TLS handshake failed: %s",
 286                          gnutls_strerror(result));
 287         send_forwarding_failure(client_fd_write);
 288         goto out;
 289     }
 290     client_session_started = 1;
 291
 292     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(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(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 (server_session_started) {
 315         gnutls_bye(server_session, GNUTLS_SHUT_RDWR);
 316     }
 317     if (client_session_started) {
 318         gnutls_bye(client_session, GNUTLS_SHUT_RDWR);
 319     }
 320     if (server_session_init) {
 321         gnutls_deinit(server_session);
 322         gnutls_certificate_free_credentials(server_x509_cred);
 323     }
 324     if (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 (server_fd_read != NULL) {
 333         if (server_fd_write != NULL) {
 334             fclose(server_fd_write);
 335         }
 336         fclose(server_fd_read);
 337     } else if (server_socket != -1) {
 338         close(server_socket);
 339     }
 340     LOG(DEBUG, "connection to server closed");
 341     /* Close connection to client. */
 342     if (client_fd_read != NULL) {
 343         if (client_fd_write != NULL) {
 344             fclose(client_fd_write);
 345         }
 346         fclose(client_fd_read);
 347     } else {
 348         close(client_socket);
 349     }
 350     LOG(DEBUG, "connection to client closed");
 351
 352     LOG(DEBUG, "connection finished");
 353 }
 354
 355
 356 static int initialize_tls_session_client(int peer_socket,
 357         const char *hostname,
 358         gnutls_session_t *session,
 359         gnutls_certificate_credentials_t *x509_cred) {
 360     int result;
 361     int use_invalid_cert;
 362     char path[TLSPROXY_MAX_PATH_LENGTH];
 363
 364     /* The "invalid" hostname is special. If it's used we send an invalid
 365      * certificate to let the client know something is wrong. */
 366     use_invalid_cert = (!strcmp(hostname, "invalid"));
 367
 368     if (proxy_certificate_path(hostname, path, sizeof(path)) != 0) {
 369         LOG(ERROR,
 370             "initialize_tls_session_client(): \
 371 failed to get proxy certificate path");
 372         return -1;
 373     }
 374
 375     result = gnutls_certificate_allocate_credentials(x509_cred);
 376     if (result != GNUTLS_E_SUCCESS) {
 377         LOG(ERROR,
 378             "initialize_tls_session_client(): \
 379 gnutls_certificate_allocate_credentials(): %s",
 380             gnutls_strerror(result));
 381         return -1;
 382     }
 383
 384     /* Load proxy CA file, this CA "list" is send to the client. */
 385     if (!use_invalid_cert) {
 386         result = gnutls_certificate_set_x509_trust_file(*x509_cred,
 387                                                         PROXY_CA_FILE,
 388                                                         GNUTLS_X509_FMT_PEM);
 389         if (result <= 0) {
 390             LOG(ERROR,
 391                 "initialize_tls_session_client(): can't read CA file: '%s'",
 392                 PROXY_CA_FILE);
 393             gnutls_certificate_free_credentials(*x509_cred);
 394             return -1;
 395         }
 396     }
 397     /* If the invalid hostname was specified do nothing, we use a self-signed
 398      * certificate in this case. */
 399
 400     /* And certificate for this website and proxy's private key. */
 401     if (!use_invalid_cert) {
 402         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 403                                                       path, PROXY_KEY_FILE,
 404                                                       GNUTLS_X509_FMT_PEM);
 405     /* If the invalid hostname was specified load our special "invalid"
 406      * certificate. */
 407     } else {
 408         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 409                                                       PROXY_INVALID_CERT_FILE,
 410                                                       PROXY_KEY_FILE,
 411                                                       GNUTLS_X509_FMT_PEM);
 412     }
 413     if (result != GNUTLS_E_SUCCESS) {
 414         LOG(ERROR,
 415             "initialize_tls_session_client(): \
 416 can't read server certificate ('%s') or key file ('%s'): %s",
 417             path, PROXY_KEY_FILE, gnutls_strerror(result));
 418         gnutls_certificate_free_credentials(*x509_cred);
 419         /* Could be a missing certificate. */
 420         return -2;
 421     }
 422
 423     gnutls_certificate_set_dh_params(*x509_cred, global_tls_dh_params);
 424
 425     result = gnutls_init(session, GNUTLS_SERVER);
 426     if (result != GNUTLS_E_SUCCESS) {
 427         LOG(ERROR,
 428             "initialize_tls_session_client(): gnutls_init(): %s",
 429             gnutls_strerror(result));
 430         gnutls_certificate_free_credentials(*x509_cred);
 431         return -1;
 432     }
 433     result = gnutls_priority_set(*session, global_tls_priority_cache);
 434     if (result != GNUTLS_E_SUCCESS) {
 435         LOG(ERROR,
 436             "initialize_tls_session_client(): gnutls_priority_set(): %s",
 437             gnutls_strerror(result));
 438         gnutls_deinit(*session);
 439         gnutls_certificate_free_credentials(*x509_cred);
 440         return -1;
 441     }
 442     result = gnutls_credentials_set(*session,
 443                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 444     if (result != GNUTLS_E_SUCCESS) {
 445         LOG(ERROR,
 446             "initialize_tls_session_client(): gnutls_credentials_set(): %s",
 447             gnutls_strerror(result));
 448         gnutls_deinit(*session);
 449         gnutls_certificate_free_credentials(*x509_cred);
 450         return -1;
 451     }
 452
 453     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 454
 455     return 0;
 456 }
 457 static int initialize_tls_session_server(int peer_socket,
 458         gnutls_session_t *session,
 459         gnutls_certificate_credentials_t *x509_cred) {
 460     int result;
 461
 462     result = gnutls_certificate_allocate_credentials(x509_cred);
 463     if (result != GNUTLS_E_SUCCESS) {
 464         LOG(ERROR,
 465             "initialize_tls_session_server(): \
 466 gnutls_certificate_allocate_credentials(): %s",
 467             gnutls_strerror(result));
 468         return -1;
 469     }
 470
 471     result = gnutls_init(session, GNUTLS_CLIENT);
 472     if (result != GNUTLS_E_SUCCESS) {
 473         LOG(ERROR,
 474             "initialize_tls_session_server(): gnutls_init(): %s",
 475             gnutls_strerror(result));
 476         gnutls_certificate_free_credentials(*x509_cred);
 477         return -1;
 478     }
 479     result = gnutls_priority_set(*session, global_tls_priority_cache);
 480     if (result != GNUTLS_E_SUCCESS) {
 481         LOG(ERROR,
 482             "initialize_tls_session_server(): gnutls_priority_set(): %s",
 483             gnutls_strerror(result));
 484         gnutls_deinit(*session);
 485         gnutls_certificate_free_credentials(*x509_cred);
 486         return -1;
 487     }
 488     result = gnutls_credentials_set(*session,
 489                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 490     if (result != GNUTLS_E_SUCCESS) {
 491         LOG(ERROR,
 492             "initialize_tls_session_server(): gnutls_credentials_set(): %s",
 493             gnutls_strerror(result));
 494         gnutls_deinit(*session);
 495         gnutls_certificate_free_credentials(*x509_cred);
 496         return -1;
 497     }
 498
 499     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 500
 501     return 0;
 502 }
 503
 504
 505 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd) {
 506     *read_fd = fdopen(socket, "r");
 507     if (*read_fd == NULL) {
 508         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"r\") failed");
 509         return -1;
 510     }
 511
 512     *write_fd = fdopen(dup(socket), "w");
 513     if (*write_fd == NULL) {
 514         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"w\") failed");
 515         fclose(*read_fd);
 516         *read_fd = NULL; /* "tell" caller read_fd is already closed */
 517         return -1;
 518     }
 519
 520     return 0;
 521 }
 522
 523 /* Read HTTP request line and headers (ignored).
 524  *
 525  * On success 0 is returned, -1 on client error, -2 on unexpected EOF.
 526  */
 527 static int read_http_request(FILE *client_fd, char *request, size_t length) {
 528     char buffer[MAX_REQUEST_LINE];
 529     int found_proxy_authorization;
 530
 531     if (fgets(request, (int)length, client_fd) == NULL) {
 532         if (ferror(client_fd)) {
 533             LOG_PERROR(WARNING, "read_http_request(): fgets()");
 534             return -1;
 535         }
 536         /* EOF */
 537         return -2;
 538     }
 539
 540     found_proxy_authorization = 0;
 541     while (fgets(buffer, sizeof(buffer), client_fd) != NULL) {
 542         const char *authentication = "Proxy-Authorization: Basic ";
 543
 544         if (http_digest_authorization != NULL
 545                 && !strncmp(buffer, authentication, strlen(authentication))) {
 546             found_proxy_authorization = 1;
 547
 548             /* Check if the passphrase matches. */
 549             strtok(buffer, "\r\n");
 550             if (strcmp(buffer + strlen(authentication),
 551                        http_digest_authorization)) {
 552                 return -3;
 553             }
 554         }
 555
 556         /* End of header. */
 557         if (!strcmp(buffer, "\n") || !strcmp(buffer, "\r\n")) {
 558             break;
 559         }
 560     }
 561     if (ferror(client_fd)) {
 562         LOG_PERROR(WARNING, "read_http_request(): fgets()");
 563         return -1;
 564     }
 565
 566     if (http_digest_authorization != NULL && !found_proxy_authorization) {
 567         return -3;
 568     }
 569
 570     return 0;
 571 }
 572
 573 static void send_bad_request(FILE *client_fd) {
 574     const char error[] = "400 Bad Request";
 575     const char msg[]   = "Your browser sent an invalid request.";
 576     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 577     fflush(client_fd);
 578 }
 579 static void send_authentication_required(FILE *client_fd) {
 580     const char error[] = "407 Proxy Authentication Required";
 581     const char auth[]  = "Proxy-Authenticate: Basic realm=\"tlsproxy\"\r\n";
 582     const char msg[]   = "TODO";
 583     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, auth, error, error, msg);
 584     fflush(client_fd);
 585 }
 586 static void send_forwarding_failure(FILE *client_fd) {
 587     const char error[] = "503 Forwarding failure";
 588     const char msg[]   = "Failed to connect to server, check logs.";
 589     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 590     fflush(client_fd);
 591 }
 592 static void tls_send_invalid_cert_message(gnutls_session_t session) {
 593     const char error[] = "500 Internal Server Error";
 594     const char msg[]   = "Server certificate validation failed, check logs.";
 595
 596     int result;
 597     char buffer[sizeof(HTTP_RESPONSE_FORMAT)
 598                 + 3 * sizeof(error) + sizeof(msg)];
 599
 600     result = snprintf(buffer, sizeof(buffer), HTTP_RESPONSE_FORMAT,
 601                                               error, "", error, error, msg);
 602     assert(result > 0 && (size_t)result < sizeof(buffer));
 603
 604     gnutls_record_send(session, buffer, strlen(buffer));
 605 }
 606
 607
 608 /* Transfer data between client and server sockets until one closes the
 609  * connection. */
 610 static void transfer_data(int client, int server) {
 611     struct pollfd fds[2];
 612     fds[0].fd      = client;
 613     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 614     fds[0].revents = 0;
 615     fds[1].fd      = server;
 616     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 617     fds[1].revents = 0;
 618
 619     for (;;) {
 620         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 621         if (result < 0) {
 622             LOG_PERROR(ERROR, "transfer_data(): poll()");
 623             return;
 624         }
 625
 626         /* Data available from client. */
 627         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 628             if (read_from_write_to(client, server) != 0) {
 629                 /* EOF (or other error) */
 630                 break;
 631             }
 632         }
 633         /* Data available from server. */
 634         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 635             if (read_from_write_to(server, client) != 0) {
 636                 /* EOF (or other error) */
 637                 break;
 638             }
 639         }
 640
 641         /* Client closed connection. */
 642         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 643             break;
 644         }
 645         /* Server closed connection. */
 646         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 647             break;
 648         }
 649     }
 650 }
 651
 652 /* Read available data from socket from and write it to socket to. At maximum
 653  * 4096 bytes are read/written. */
 654 static int read_from_write_to(int from, int to) {
 655     ssize_t size_read;
 656     ssize_t size_written;
 657     char buffer[4096];
 658
 659     LOG(DEBUG, "read_from_write_to(): %d -> %d", from, to);
 660
 661     size_read = read(from, buffer, sizeof(buffer));
 662     if (size_read < 0) {
 663         LOG_PERROR(WARNING, "read_from_write_to(): read()");
 664         return -1;
 665     /* EOF */
 666     } else if (size_read == 0) {
 667         return -1;
 668     }
 669
 670     size_written = write(to, buffer, (size_t)size_read);
 671     if (size_written < 0) {
 672         LOG_PERROR(WARNING, "read_from_write_to(): write()");
 673         return -1;
 674     }
 675     if (size_read != size_written) {
 676         LOG(ERROR, "read_from_write_to(): only written %ld of %ld bytes!",
 677                        (long int)size_written, (long int)size_read);
 678         return -1;
 679     }
 680
 681     return 0;
 682 }
 683
 684 /* Transfer data between client and server TLS connection until one closes the
 685  * connection. */
 686 static void transfer_data_tls(int client, int server,
 687                               gnutls_session_t client_session,
 688                               gnutls_session_t server_session) {
 689     size_t buffer_size;
 690
 691     struct pollfd fds[2];
 692     fds[0].fd      = client;
 693     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 694     fds[0].revents = 0;
 695     fds[1].fd      = server;
 696     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 697     fds[1].revents = 0;
 698
 699     /* Get maximum possible buffer size. */
 700     buffer_size = gnutls_record_get_max_size(client_session);
 701     if (gnutls_record_get_max_size(server_session) < buffer_size) {
 702         buffer_size = gnutls_record_get_max_size(server_session);
 703     }
 704     LOG(DEBUG, "transfer_data_tls(): suggested buffer size: %ld",
 705                    (long int)buffer_size);
 706
 707     for (;;) {
 708         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 709         if (result < 0) {
 710             LOG_PERROR(ERROR, "transfer_data(): poll()");
 711             return;
 712         }
 713
 714         /* Data available from client. */
 715         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 716             if (read_from_write_to_tls(client_session, server_session,
 717                                        buffer_size) != 0) {
 718                 /* EOF (or other error) */
 719                 break;
 720             }
 721         }
 722         /* Data available from server. */
 723         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 724             if (read_from_write_to_tls(server_session, client_session,
 725                                        buffer_size) != 0) {
 726                 /* EOF (or other error) */
 727                 break;
 728             }
 729         }
 730
 731         /* Client closed connection. */
 732         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 733             break;
 734         }
 735         /* Server closed connection. */
 736         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 737             break;
 738         }
 739     }
 740 }
 741
 742 /* Read available data from session from and write to session to. */
 743 static int read_from_write_to_tls(gnutls_session_t from,
 744                                   gnutls_session_t to,
 745                                   size_t buffer_size) {
 746     ssize_t size_read;
 747     ssize_t size_written;
 748     char buffer[16384];
 749
 750     if (buffer_size > sizeof(buffer)) {
 751         buffer_size = sizeof(buffer);
 752     }
 753     LOG(DEBUG, "read_from_write_to_tls(): used buffer size: %ld",
 754                    (long int)buffer_size);
 755
 756     size_read = gnutls_record_recv(from, buffer, buffer_size);
 757     if (size_read < 0) {
 758         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_recv(): %s",
 759                          gnutls_strerror((int)size_read));
 760         return -1;
 761     /* EOF */
 762     } else if (size_read == 0) {
 763         return -1;
 764     }
 765
 766     size_written = gnutls_record_send(to, buffer, (size_t)size_read);
 767     if (size_written < 0) {
 768         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_send(): %s",
 769                          gnutls_strerror((int)size_written));
 770         return -1;
 771     }
 772     if (size_read != size_written) {
 773         LOG(ERROR, "read_from_write_to_tls(): only written %ld of %ld bytes!",
 774                        (long int)size_written, (long int)size_read);
 775         return -1;
 776     }
 777
 778     return 0;
 779 }
 780
 781
 782 static int connect_to_host(const char *hostname, const char *port) {
 783     struct addrinfo gai_hints;
 784     struct addrinfo *gai_result;
 785     int gai_return;
 786
 787     int server_socket;
 788     struct addrinfo *server;
 789
 790     if (hostname == NULL || port == NULL) {
 791         return -1;
 792     }
 793
 794     /* Get IP of hostname server. */
 795     memset(&gai_hints, 0, sizeof(gai_hints));
 796     gai_hints.ai_family   = AF_UNSPEC;
 797     gai_hints.ai_socktype = SOCK_STREAM;
 798     gai_hints.ai_protocol = 0;
 799     gai_hints.ai_flags    = AI_NUMERICSERV /* given port is numeric */
 800                           | AI_ADDRCONFIG  /* supported by this computer */
 801                           | AI_V4MAPPED;   /* support IPv4 through IPv6 */
 802     gai_return = getaddrinfo(hostname, port, &gai_hints, &gai_result);
 803     if (gai_return != 0) {
 804         if (gai_return == EAI_SYSTEM) {
 805             LOG_PERROR(WARNING, "connect_to_host(): getaddrinfo()");
 806         } else {
 807             LOG(WARNING, "connect_to_host(): getaddrinfo(): %s",
 808                              gai_strerror(gai_return));
 809         }
 810         return -1;
 811     }
 812
 813     /* Now try to connect to each server returned by getaddrinfo(), use the
 814      * first successful connect. */
 815     for (server = gai_result; server != NULL; server = server->ai_next) {
 816         server_socket = socket(server->ai_family,
 817                                server->ai_socktype,
 818                                server->ai_protocol);
 819         if (server_socket < 0) {
 820             LOG_PERROR(DEBUG, "connect_to_host(): socket(), trying next");
 821             continue;
 822         }
 823
 824         if (connect(server_socket, server->ai_addr, server->ai_addrlen) == 0) {
 825             break;
 826         }
 827         LOG_PERROR(DEBUG, "connect_to_host(): connect(), trying next");
 828
 829         close(server_socket);
 830     }
 831     /* Make sure we free the result from getaddrinfo(). */
 832     freeaddrinfo(gai_result);
 833
 834     if (server == NULL) {
 835         LOG_PERROR(WARNING, "connect_to_host(): no server found, abort");
 836         return -1;
 837     }
 838
 839     return server_socket;
 840 }
 841
 842
 843 /* Parse HTTP CONNECT request string and save its parameters.
 844  *
 845  * The following format is expected: "CONNECT host:port HTTP/1.x".
 846  *
 847  * request and host must have the same size! port must be at least 6 bytes
 848  * long (5 + '\0').
 849  */
 850 static int parse_request(const char *request, char *host, char *port,
 851                                               int *version_minor) {
 852     int port_unused; /* just used to verify the port is numeric */
 853     char *position;
 854
 855     /* scanf() doesn't check spaces. */
 856     if (strncmp(request, "CONNECT ", 8)) {
 857         return -1;
 858     }
 859     /* Check request and extract data, "host:port" is not yet separated. */
 860     if (sscanf(request, "CONNECT %s HTTP/1.%d", host, version_minor) != 2) {
 861         return -1;
 862     }
 863     /* Make sure ":port" is there. */
 864     if ((position = strchr(host, ':')) == NULL) {
 865         return -1;
 866     }
 867     /* Make sure port is numeric. */
 868     if (sscanf(position + 1, "%d", &port_unused) != 1) {
 869         return -1;
 870     }
 871     /* Store it in *port. */
 872     strncpy(port, position + 1, 5);
 873     port[5] = '\0';
 874     /* And remove port from host. */
 875     *position = '\0';
 876
 877     return 0;
 878 }