src/connection.c

   1 /*
   2  * Handle connections.
   3  *
   4  * Copyright (C) 2011-2014  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 <sys/socket.h>
  30 #include <unistd.h>
  31
  32 #include <gnutls/x509.h>
  33
  34
  35 /* Maximum length of a HTTP request line. Longer request lines are aborted
  36  * with an error. The standard doesn't specify a maximum line length but this
  37  * should be a good limit to make processing simpler. As HTTPS is used this
  38  * doesn't limit long GET requests. */
  39 #define MAX_REQUEST_LINE 4096
  40
  41 /* Format string used to send HTTP/1.0 error responses to the client.
  42  *
  43  * %s is used 5 times, first is the error code, then additional headers, next
  44  * two are the error code (no %n$s which is not in C98!), the last is the
  45  * message. */
  46 #define HTTP_RESPONSE_FORMAT "HTTP/1.0 %s\r\n\
  47 Content-Type: text/html; charset=US-ASCII\r\n\
  48 %s\r\n\
  49 <!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">\n\
  50 <html>\n\
  51 <head><title>%s</title></head>\n\
  52 <body>\n\
  53 <h1>%s</h1>\n\
  54 <p>%s</p>\n\
  55 </body>\n\
  56 </html>\n"
  57
  58
  59 static int initialize_tls_session_client(int peer_socket,
  60         const char *hostname,
  61         gnutls_session_t *session,
  62         gnutls_certificate_credentials_t *x509_cred);
  63 static int initialize_tls_session_server(int peer_socket,
  64         gnutls_session_t *session,
  65         gnutls_certificate_credentials_t *x509_cred);
  66 static int initialize_tls_session_both(unsigned int flags,
  67         int peer_socket,
  68         gnutls_session_t *session,
  69         gnutls_certificate_credentials_t *x509_cred);
  70
  71 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd);
  72 static int read_http_request(FILE *client_fd, char *request, size_t length);
  73 static void send_bad_request(FILE *client_fd);
  74 static void send_authentication_required(FILE *client_fd);
  75 static void send_forwarding_failure(FILE *client_fd);
  76 static void tls_send_invalid_cert_message(gnutls_session_t session);
  77
  78 static void transfer_data(int client, int server);
  79 static int read_from_write_to(int from, int to);
  80 static void transfer_data_tls(int client, int server,
  81                               gnutls_session_t client_session,
  82                               gnutls_session_t server_session);
  83 static int read_from_write_to_tls(gnutls_session_t from, gnutls_session_t to,
  84                                   size_t buffer_size);
  85
  86 static int connect_to_host(const char *hostname, const char *port);
  87
  88 static int parse_request(const char *buffer, char *host, char *port,
  89                                              int *version_minor);
  90
  91 static void log_session_information(gnutls_session_t session);
  92
  93
  94 void handle_connection(int client_socket) {
  95     int server_socket;
  96     FILE *client_fd_read, *client_fd_write, *server_fd_read, *server_fd_write;
  97
  98     char buffer[MAX_REQUEST_LINE];
  99     char host[MAX_REQUEST_LINE];
 100     char port[5 + 1];
 101
 102     int version_minor; /* x in HTTP/1.x */
 103     int result;
 104
 105     /* client_x509_cred is used when talking to the client (acting as a TLS
 106      * server), server_x509_cred is used when talking to the server (acting as
 107      * a TLS client). */
 108     gnutls_certificate_credentials_t client_x509_cred, server_x509_cred;
 109
 110     gnutls_session_t client_session, server_session;
 111     /* initialize_tls_session_*() called? - used for goto out */
 112     int client_session_init, server_session_init;
 113     /* gnutls_handshake() called? - used for goto out */
 114     int client_session_started, server_session_started;
 115     /* Validation failed? If yes we need to send the special "invalid"
 116      * certificate. */
 117     int validation_failed;
 118
 119     LOG(DEBUG1, "new connection");
 120
 121     server_socket = -1;
 122     client_fd_read = NULL;
 123     client_fd_write = NULL;
 124     server_fd_read = NULL;
 125     server_fd_write = NULL;
 126     client_session_init = 0;
 127     server_session_init = 0;
 128     client_session_started = 0;
 129     server_session_started = 0;
 130     validation_failed = 0;
 131
 132     if (fdopen_read_write(client_socket, &client_fd_read,
 133                                          &client_fd_write) != 0) {
 134         goto out;
 135     }
 136
 137     /* Read request line (CONNECT ..) and headers (they are discarded). */
 138     result = read_http_request(client_fd_read, buffer, sizeof(buffer));
 139     if (result == -1) {
 140         LOG(WARNING, "read_http_request(): client read error");
 141         goto out;
 142     } else if (result == -2) {
 143         LOG(WARNING, "read_http_request(): client EOF");
 144         send_bad_request(client_fd_write);
 145         goto out;
 146     } else if (result == -3) {
 147         LOG(WARNING, "read_http_request(): proxy authentication failed");
 148         send_authentication_required(client_fd_write);
 149         goto out;
 150     }
 151
 152     if (parse_request(buffer, host, port, &version_minor) != 0) {
 153         LOG(WARNING, "bad request: >%s<", buffer);
 154         send_bad_request(client_fd_write);
 155         goto out;
 156     }
 157
 158     LOG(DEBUG2, "target: %s:%s (HTTP 1.%d)", host, port, version_minor);
 159
 160     /* Connect to proxy server or directly to server. */
 161     if (global_proxy_host != NULL && global_proxy_port != NULL) {
 162         LOG(DEBUG1, "connecting to %s:%s", global_proxy_host,
 163                                            global_proxy_port);
 164         server_socket = connect_to_host(global_proxy_host, global_proxy_port);
 165     } else {
 166         LOG(DEBUG1, "connecting to %s:%s", host, port);
 167         server_socket = connect_to_host(host, port);
 168     }
 169
 170     if (server_socket < 0) {
 171         LOG(WARNING, "failed to connect to server");
 172         send_forwarding_failure(client_fd_write);
 173         goto out;
 174     }
 175     if (fdopen_read_write(server_socket, &server_fd_read,
 176                                          &server_fd_write) != 0) {
 177         send_forwarding_failure(client_fd_write);
 178         goto out;
 179     }
 180
 181     /* Connect to proxy if requested (command line option). */
 182     if (global_proxy_host != NULL && global_proxy_port != NULL) {
 183         fprintf(server_fd_write, "CONNECT %s:%s HTTP/1.0\r\n", host, port);
 184         fprintf(server_fd_write, "\r\n");
 185         fflush(server_fd_write);
 186
 187         /* Read response line from proxy server. */
 188         result = read_http_request(server_fd_read, buffer, sizeof(buffer));
 189         if (result == -1) {
 190             LOG(WARNING, "read_http_request(): proxy read error");
 191             send_forwarding_failure(client_fd_write);
 192             goto out;
 193         } else if (result == -2) {
 194             LOG(WARNING, "read_http_request(): proxy EOF");
 195             send_forwarding_failure(client_fd_write);
 196             goto out;
 197         }
 198
 199         /* Check response of proxy server. */
 200         if (strncmp(buffer, "HTTP/1.0 200", 12)) {
 201             LOG(WARNING, "bad proxy response: >%s<", buffer);
 202             send_forwarding_failure(client_fd_write);
 203             goto out;
 204         }
 205     }
 206
 207     LOG(DEBUG1, "connection to server established");
 208
 209     /* If the -u option is used and we don't know this hostname's server
 210      * certificate, then just pass through the connection and let the client
 211      * verify the server certificate. */
 212     if (global_passthrough_unknown) {
 213         char path[TLSPROXY_MAX_PATH_LENGTH];
 214         FILE *file = NULL;
 215
 216         if (server_certificate_file(&file, host, path, sizeof(path)) == -2) {
 217             /* We've established a connection, tell the client. */
 218             fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
 219             fprintf(client_fd_write, "\r\n");
 220             fflush(client_fd_write);
 221
 222             LOG(DEBUG1, "transferring data");
 223
 224             /* Proxy data between client and server until one side is done
 225              * (EOF or error). */
 226             transfer_data(client_socket, server_socket);
 227
 228             LOG(DEBUG1, "finished transferring data");
 229
 230             goto out;
 231         }
 232         /* server_certificate_file() may have opened the file, close it. */
 233         if (file != NULL) {
 234             fclose(file);
 235         }
 236     }
 237
 238     /* Initialize TLS client credentials to talk to the server. */
 239     result = initialize_tls_session_server(server_socket, &server_session,
 240                                                           &server_x509_cred);
 241     if (result != 0) {
 242         LOG(WARNING, "initialize_tls_session_server() failed");
 243         send_forwarding_failure(client_fd_write);
 244         goto out;
 245     }
 246     server_session_init = 1;
 247
 248     LOG(DEBUG1, "starting server TLS handshake");
 249
 250     /* Try to establish TLS handshake between us and server. */
 251     result = gnutls_handshake(server_session);
 252     if (result != GNUTLS_E_SUCCESS) {
 253         LOG(WARNING, "server TLS handshake failed: %s",
 254                      gnutls_strerror(result));
 255         send_forwarding_failure(client_fd_write);
 256         goto out;
 257     }
 258     server_session_started = 1;
 259
 260     LOG(DEBUG1, "server TLS handshake finished");
 261
 262     if (global_log_level >= LOG_DEBUG2_LEVEL) {
 263         log_session_information(server_session);
 264     }
 265
 266     /* Make sure the server certificate is valid and known. */
 267     if (verify_tls_connection(server_session, host) != 0) {
 268         LOG(ERROR, "server certificate validation failed!");
 269         /* We'll send the error message over our TLS connection to the client,
 270          * but with an invalid certificate. No data is transfered from/to the
 271          * target server. */
 272         validation_failed = 1;
 273     }
 274
 275     /* Initialize TLS server credentials to talk to the client. */
 276     result = initialize_tls_session_client(client_socket,
 277                                            /* use a special host if the server
 278                                             * certificate was invalid */
 279                                            (validation_failed) ? "invalid"
 280                                                                : host,
 281                                            &client_session,
 282                                            &client_x509_cred);
 283     if (result != 0) {
 284         LOG(WARNING, "initialize_tls_session_client() failed");
 285         send_forwarding_failure(client_fd_write);
 286         goto out;
 287     }
 288     client_session_init = 1;
 289
 290     /* We've established a connection, tell the client. */
 291     fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
 292     fprintf(client_fd_write, "\r\n");
 293     fflush(client_fd_write);
 294
 295     LOG(DEBUG1, "starting client TLS handshake");
 296
 297     /* Try to establish TLS handshake between client and us. */
 298     result = gnutls_handshake(client_session);
 299     if (result != GNUTLS_E_SUCCESS) {
 300         LOG(WARNING, "client TLS handshake failed: %s",
 301                      gnutls_strerror(result));
 302         send_forwarding_failure(client_fd_write);
 303         goto out;
 304     }
 305     client_session_started = 1;
 306
 307     LOG(DEBUG1, "client TLS handshake finished");
 308
 309     if (global_log_level >= LOG_DEBUG2_LEVEL) {
 310         log_session_information(client_session);
 311     }
 312
 313     /* Tell the client that the verification failed. Shouldn't be necessary as
 314      * the client should terminate the connection because he received the
 315      * invalid certificate but better be sure. */
 316     if (validation_failed) {
 317         tls_send_invalid_cert_message(client_session);
 318         goto out;
 319     }
 320
 321     LOG(DEBUG1, "transferring TLS data");
 322
 323     /* Proxy data between client and server until one side is done (EOF or
 324      * error). */
 325     transfer_data_tls(client_socket, server_socket,
 326                       client_session, server_session);
 327
 328     LOG(DEBUG1, "finished transferring TLS data");
 329
 330 out:
 331     /* Close TLS sessions if necessary. Use GNUTLS_SHUT_RDWR so the data is
 332      * reliable transmitted. */
 333     if (server_session_started) {
 334         /* Recent gnutls-serv (used in the test-suite) won't terminate the
 335          * connection when gnutls_bye(session, GNUTLS_SHUT_RDWR) is used
 336          * before any other data was received. If the validation failed just
 337          * close the connection without waiting for data, we won't read it
 338          * anyway.
 339          *
 340          * For verified connections GNUTLS_SHUT_RDWR is important or we might
 341          * lose data. */
 342         gnutls_bye(server_session, validation_failed ? GNUTLS_SHUT_WR
 343                                                      : GNUTLS_SHUT_RDWR);
 344     }
 345     if (client_session_started) {
 346         gnutls_bye(client_session, GNUTLS_SHUT_RDWR);
 347     }
 348     if (server_session_init) {
 349         gnutls_deinit(server_session);
 350         gnutls_certificate_free_credentials(server_x509_cred);
 351     }
 352     if (client_session_init) {
 353         gnutls_deinit(client_session);
 354         gnutls_certificate_free_credentials(client_x509_cred);
 355     }
 356
 357     /* Close connection to server/proxy. */
 358     if (server_fd_read != NULL) {
 359         if (server_fd_write != NULL) {
 360             fclose(server_fd_write);
 361         }
 362         fclose(server_fd_read);
 363     } else if (server_socket != -1) {
 364         close(server_socket);
 365     }
 366     LOG(DEBUG1, "connection to server closed");
 367     /* Close connection to client. */
 368     if (client_fd_read != NULL) {
 369         if (client_fd_write != NULL) {
 370             fclose(client_fd_write);
 371         }
 372         fclose(client_fd_read);
 373     } else {
 374         close(client_socket);
 375     }
 376     LOG(DEBUG1, "connection to client closed");
 377
 378     LOG(DEBUG1, "connection finished");
 379 }
 380
 381
 382 static int initialize_tls_session_client(int peer_socket,
 383         const char *hostname,
 384         gnutls_session_t *session,
 385         gnutls_certificate_credentials_t *x509_cred) {
 386     int result;
 387     int use_invalid_cert;
 388     char path[TLSPROXY_MAX_PATH_LENGTH];
 389
 390     /* The "invalid" hostname is special. If it's used we send an invalid
 391      * certificate to let the client know something is wrong. */
 392     use_invalid_cert = (!strcmp(hostname, "invalid"));
 393
 394     if (proxy_certificate_path(hostname, path, sizeof(path)) != 0) {
 395         LOG(ERROR,
 396             "initialize_tls_session_client(): "
 397             "failed to get proxy certificate path");
 398         return -1;
 399     }
 400
 401     result = gnutls_certificate_allocate_credentials(x509_cred);
 402     if (result != GNUTLS_E_SUCCESS) {
 403         LOG(ERROR,
 404             "initialize_tls_session_client(): "
 405             "gnutls_certificate_allocate_credentials(): %s",
 406             gnutls_strerror(result));
 407         return -1;
 408     }
 409
 410     /* Load proxy CA file, this CA "list" is send to the client. */
 411     if (!use_invalid_cert) {
 412         result = gnutls_certificate_set_x509_trust_file(*x509_cred,
 413                                                         PROXY_CA_PATH,
 414                                                         GNUTLS_X509_FMT_PEM);
 415         if (result <= 0) {
 416             LOG(ERROR,
 417                 "initialize_tls_session_client(): can't read CA file: '%s'",
 418                 PROXY_CA_PATH);
 419             gnutls_certificate_free_credentials(*x509_cred);
 420             return -1;
 421         } else if (result != 1) {
 422             /* Must contain only one CA, our proxy CA. */
 423             LOG(ERROR, "initialize_tls_session_client(): multiple CAs found");
 424             gnutls_certificate_free_credentials(*x509_cred);
 425             return -1;
 426         }
 427     }
 428     /* If the invalid hostname was specified do nothing, we use a self-signed
 429      * certificate in this case. */
 430
 431     /* And certificate for this website and proxy's private key. */
 432     if (!use_invalid_cert) {
 433         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 434                                                       path,
 435                                                       PROXY_KEY_PATH,
 436                                                       GNUTLS_X509_FMT_PEM);
 437     /* If the invalid hostname was specified load our special "invalid"
 438      * certificate. */
 439     } else {
 440         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 441                                                       PROXY_INVALID_CERT_PATH,
 442                                                       PROXY_KEY_PATH,
 443                                                       GNUTLS_X509_FMT_PEM);
 444     }
 445     if (result != GNUTLS_E_SUCCESS) {
 446         LOG(ERROR,
 447             "initialize_tls_session_client(): "
 448             "can't read server certificate ('%s') or key file ('%s'): %s",
 449             path, PROXY_KEY_PATH, gnutls_strerror(result));
 450         gnutls_certificate_free_credentials(*x509_cred);
 451         /* Could be a missing certificate. */
 452         return -2;
 453     }
 454
 455     gnutls_certificate_set_dh_params(*x509_cred, global_tls_dh_params);
 456
 457     return initialize_tls_session_both(GNUTLS_SERVER,
 458                                        peer_socket, session, x509_cred);
 459 }
 460 static int initialize_tls_session_server(int peer_socket,
 461         gnutls_session_t *session,
 462         gnutls_certificate_credentials_t *x509_cred) {
 463     int result;
 464
 465     result = gnutls_certificate_allocate_credentials(x509_cred);
 466     if (result != GNUTLS_E_SUCCESS) {
 467         LOG(ERROR,
 468             "initialize_tls_session_server(): "
 469             "gnutls_certificate_allocate_credentials(): %s",
 470             gnutls_strerror(result));
 471         return -1;
 472     }
 473
 474     return initialize_tls_session_both(GNUTLS_CLIENT,
 475                                        peer_socket, session, x509_cred);
 476 }
 477 static int initialize_tls_session_both(unsigned int flags,
 478         int peer_socket,
 479         gnutls_session_t *session,
 480         gnutls_certificate_credentials_t *x509_cred) {
 481     int result;
 482
 483     *session = NULL;
 484
 485     result = gnutls_init(session, flags);
 486     if (result != GNUTLS_E_SUCCESS) {
 487         LOG(ERROR,
 488             "initialize_tls_session_both(): gnutls_init(): %s",
 489             gnutls_strerror(result));
 490         goto err;
 491     }
 492     result = gnutls_priority_set(*session, global_tls_priority_cache);
 493     if (result != GNUTLS_E_SUCCESS) {
 494         LOG(ERROR,
 495             "initialize_tls_session_both(): gnutls_priority_set(): %s",
 496             gnutls_strerror(result));
 497         goto err;
 498     }
 499     result = gnutls_credentials_set(*session,
 500                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 501     if (result != GNUTLS_E_SUCCESS) {
 502         LOG(ERROR,
 503             "initialize_tls_session_both(): gnutls_credentials_set(): %s",
 504             gnutls_strerror(result));
 505         goto err;
 506     }
 507
 508 #ifdef HAVE_GNUTLS_TRANSPORT_SET_INT2
 509     /* gnutls_transport_set_int() is a macro. */
 510     gnutls_transport_set_int(*session, peer_socket);
 511 #else
 512     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 513 #endif
 514
 515     return 0;
 516
 517 err:
 518     if (*session) {
 519         gnutls_deinit(*session);
 520     }
 521     gnutls_certificate_free_credentials(*x509_cred);
 522     return -1;
 523 }
 524
 525
 526 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd) {
 527     *read_fd = fdopen(socket, "r");
 528     if (*read_fd == NULL) {
 529         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"r\") failed");
 530         return -1;
 531     }
 532
 533     *write_fd = fdopen(dup(socket), "w");
 534     if (*write_fd == NULL) {
 535         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"w\") failed");
 536         fclose(*read_fd);
 537         *read_fd = NULL; /* "tell" caller read_fd is already closed */
 538         return -1;
 539     }
 540
 541     return 0;
 542 }
 543
 544 /* Read HTTP request line and headers (ignored).
 545  *
 546  * On success 0 is returned, -1 on client error, -2 on unexpected EOF.
 547  */
 548 static int read_http_request(FILE *client_fd, char *request, size_t length) {
 549     char buffer[MAX_REQUEST_LINE];
 550     int found_proxy_authorization;
 551
 552     assert(length <= INT_MAX);
 553     if (fgets(request, (int)length, client_fd) == NULL) {
 554         if (ferror(client_fd)) {
 555             LOG_PERROR(WARNING, "read_http_request(): fgets()");
 556             return -1;
 557         }
 558         /* EOF */
 559         return -2;
 560     }
 561
 562     found_proxy_authorization = 0;
 563     while (fgets(buffer, sizeof(buffer), client_fd) != NULL) {
 564         const char *authentication = "Proxy-Authorization: Basic ";
 565
 566         if (global_http_digest_authorization != NULL
 567                 && !strncmp(buffer, authentication, strlen(authentication))) {
 568             found_proxy_authorization = 1;
 569
 570             /* Check if the passphrase matches. */
 571             strtok(buffer, "\r\n");
 572             if (strcmp(buffer + strlen(authentication),
 573                        global_http_digest_authorization)) {
 574                 return -3;
 575             }
 576         }
 577
 578         /* End of header. */
 579         if (!strcmp(buffer, "\n") || !strcmp(buffer, "\r\n")) {
 580             break;
 581         }
 582     }
 583     if (ferror(client_fd)) {
 584         LOG_PERROR(WARNING, "read_http_request(): fgets()");
 585         return -1;
 586     } else if (feof(client_fd)) {
 587         return -2;
 588     }
 589
 590     if (global_http_digest_authorization != NULL && !found_proxy_authorization) {
 591         return -3;
 592     }
 593
 594     return 0;
 595 }
 596
 597 static void send_bad_request(FILE *client_fd) {
 598     const char error[] = "400 Bad Request";
 599     const char msg[]   = "Your browser sent an invalid request.";
 600     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 601     fflush(client_fd);
 602 }
 603 static void send_authentication_required(FILE *client_fd) {
 604     const char error[] = "407 Proxy Authentication Required";
 605     const char auth[]  = "Proxy-Authenticate: Basic realm=\"tlsproxy\"\r\n";
 606     const char msg[]   = "TODO";
 607     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, auth, error, error, msg);
 608     fflush(client_fd);
 609 }
 610 static void send_forwarding_failure(FILE *client_fd) {
 611     const char error[] = "503 Forwarding failure";
 612     const char msg[]   = "Failed to connect to server, check logs.";
 613     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 614     fflush(client_fd);
 615 }
 616 static void tls_send_invalid_cert_message(gnutls_session_t session) {
 617     const char error[] = "500 Internal Server Error";
 618     const char msg[]   = "Server certificate validation failed, check logs.";
 619
 620     int result;
 621     ssize_t size_written;
 622     char buffer[sizeof(HTTP_RESPONSE_FORMAT)
 623                 + 3 * sizeof(error) + sizeof(msg)];
 624
 625     result = snprintf(buffer, sizeof(buffer), HTTP_RESPONSE_FORMAT,
 626                                               error, "", error, error, msg);
 627     assert(result > 0 && (size_t)result < sizeof(buffer));
 628
 629     size_written = gnutls_record_send(session, buffer, strlen(buffer));
 630     if (size_written < 0) {
 631         LOG(WARNING, "tls_send_invalid_cert_message(): "
 632                      "gnutls_record_send(): %s",
 633                      gnutls_strerror((int)size_written));
 634     }
 635     /* Just an error message, no need to check if everything was written. */
 636 }
 637
 638
 639 /* Transfer data between client and server sockets until one closes the
 640  * connection. */
 641 static void transfer_data(int client, int server) {
 642     struct pollfd fds[2];
 643     fds[0].fd      = client;
 644     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 645     fds[0].revents = 0;
 646     fds[1].fd      = server;
 647     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 648     fds[1].revents = 0;
 649
 650     LOG(DEBUG2, "transfer_data(): %d -> %d", client, server);
 651
 652     for (;;) {
 653         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 654         if (result < 0) {
 655             LOG_PERROR(ERROR, "transfer_data(): poll()");
 656             return;
 657         }
 658
 659         /* Data available from client. */
 660         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 661             if (read_from_write_to(client, server) != 0) {
 662                 /* EOF (or other error) */
 663                 break;
 664             }
 665         }
 666         /* Data available from server. */
 667         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 668             if (read_from_write_to(server, client) != 0) {
 669                 /* EOF (or other error) */
 670                 break;
 671             }
 672         }
 673
 674         /* Client closed connection. */
 675         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 676             break;
 677         }
 678         /* Server closed connection. */
 679         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 680             break;
 681         }
 682     }
 683 }
 684
 685 /* Read available data from socket from and write it to socket to. At maximum
 686  * 4096 bytes are read/written. */
 687 static int read_from_write_to(int from, int to) {
 688     ssize_t size_read;
 689     ssize_t size_written;
 690     char buffer[4096];
 691
 692     size_read = read(from, buffer, sizeof(buffer));
 693     if (size_read < 0) {
 694         LOG_PERROR(WARNING, "read_from_write_to(): read()");
 695         return -1;
 696     /* EOF */
 697     } else if (size_read == 0) {
 698         return -1;
 699     }
 700
 701     size_written = write(to, buffer, (size_t)size_read);
 702     if (size_written < 0) {
 703         LOG_PERROR(WARNING, "read_from_write_to(): write()");
 704         return -1;
 705     }
 706     if (size_read != size_written) {
 707         LOG(ERROR, "read_from_write_to(): only written %zu of %zu bytes!",
 708                    size_written, size_read);
 709         return -1;
 710     }
 711
 712     return 0;
 713 }
 714
 715 /* Transfer data between client and server TLS connection until one closes the
 716  * connection. */
 717 static void transfer_data_tls(int client, int server,
 718                               gnutls_session_t client_session,
 719                               gnutls_session_t server_session) {
 720     size_t buffer_size;
 721
 722     struct pollfd fds[2];
 723     fds[0].fd      = client;
 724     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 725     fds[0].revents = 0;
 726     fds[1].fd      = server;
 727     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 728     fds[1].revents = 0;
 729
 730     /* Get maximum possible buffer size. */
 731     buffer_size = gnutls_record_get_max_size(client_session);
 732     if (gnutls_record_get_max_size(server_session) < buffer_size) {
 733         buffer_size = gnutls_record_get_max_size(server_session);
 734     }
 735     LOG(DEBUG2, "transfer_data_tls(): suggested buffer size: %zu",
 736                 buffer_size);
 737
 738     for (;;) {
 739         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 740         if (result < 0) {
 741             LOG_PERROR(ERROR, "transfer_data(): poll()");
 742             return;
 743         }
 744
 745         /* Data available from client. */
 746         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 747             if (read_from_write_to_tls(client_session, server_session,
 748                                        buffer_size) != 0) {
 749                 /* EOF (or other error) */
 750                 break;
 751             }
 752         }
 753         /* Data available from server. */
 754         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 755             if (read_from_write_to_tls(server_session, client_session,
 756                                        buffer_size) != 0) {
 757                 /* EOF (or other error) */
 758                 break;
 759             }
 760         }
 761
 762         /* Client closed connection. */
 763         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 764             break;
 765         }
 766         /* Server closed connection. */
 767         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 768             break;
 769         }
 770     }
 771 }
 772
 773 /* Read available data from session from and write to session to. */
 774 static int read_from_write_to_tls(gnutls_session_t from,
 775                                   gnutls_session_t to,
 776                                   size_t buffer_size) {
 777     ssize_t size_read;
 778     ssize_t size_written;
 779     char buffer[16384]; /* GnuTLS default maximum */
 780
 781     if (buffer_size > sizeof(buffer)) {
 782         LOG(WARNING, "read_from_write_to_tls(): reduced buffer size to %zu",
 783                      sizeof(buffer));
 784         buffer_size = sizeof(buffer);
 785     }
 786
 787     size_read = gnutls_record_recv(from, buffer, buffer_size);
 788     if (size_read < 0) {
 789         /* Allow rehandshakes. As handshakes might be insecure make sure that
 790          * %SAFE_RENEGOTIATION is used in GnuTLS's priority string. */
 791         if (size_read == GNUTLS_E_REHANDSHAKE) {
 792             int result;
 793
 794             LOG(DEBUG1, "server requested TLS rehandshake");
 795
 796             result = gnutls_handshake(from);
 797             if (result != GNUTLS_E_SUCCESS) {
 798                 LOG(WARNING, "server TLS rehandshake failed: %s",
 799                              gnutls_strerror(result));
 800                 return -1;
 801             }
 802             return 0;
 803         }
 804
 805         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_recv(): %s",
 806                      gnutls_strerror((int)size_read));
 807         return -1;
 808     /* EOF */
 809     } else if (size_read == 0) {
 810         return -1;
 811     }
 812
 813     size_written = gnutls_record_send(to, buffer, (size_t)size_read);
 814     if (size_written < 0) {
 815         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_send(): %s",
 816                      gnutls_strerror((int)size_written));
 817         return -1;
 818     }
 819     if (size_read != size_written) {
 820         LOG(ERROR, "read_from_write_to_tls(): only written %zu of %zu bytes!",
 821                    size_written, size_read);
 822         return -1;
 823     }
 824
 825     return 0;
 826 }
 827
 828
 829 static int connect_to_host(const char *hostname, const char *port) {
 830     struct addrinfo gai_hints;
 831     struct addrinfo *gai_result;
 832     int gai_return;
 833
 834     int server_socket;
 835     struct addrinfo *server;
 836
 837     if (hostname == NULL || port == NULL) {
 838         return -1;
 839     }
 840
 841     /* Get IP of hostname server. */
 842     memset(&gai_hints, 0, sizeof(gai_hints));
 843     gai_hints.ai_family   = AF_UNSPEC;
 844     gai_hints.ai_socktype = SOCK_STREAM;
 845     gai_hints.ai_protocol = 0;
 846     gai_hints.ai_flags    = AI_NUMERICSERV /* given port is numeric */
 847 #ifdef AI_ADDRCONFIG
 848                           | AI_ADDRCONFIG  /* supported by this computer */
 849 #endif
 850                           ;
 851     gai_return = getaddrinfo(hostname, port, &gai_hints, &gai_result);
 852     if (gai_return != 0) {
 853         if (gai_return == EAI_SYSTEM) {
 854             LOG_PERROR(WARNING, "connect_to_host(): getaddrinfo()");
 855         } else {
 856             LOG(WARNING, "connect_to_host(): getaddrinfo(): %s",
 857                          gai_strerror(gai_return));
 858         }
 859         return -1;
 860     }
 861
 862     /* Now try to connect to each server returned by getaddrinfo(), use the
 863      * first successful connect. */
 864     for (server = gai_result; server != NULL; server = server->ai_next) {
 865         server_socket = socket(server->ai_family,
 866                                server->ai_socktype,
 867                                server->ai_protocol);
 868         if (server_socket < 0) {
 869             LOG_PERROR(DEBUG1, "connect_to_host(): socket(), trying next");
 870             continue;
 871         }
 872
 873         if (connect(server_socket, server->ai_addr, server->ai_addrlen) == 0) {
 874             break;
 875         }
 876         LOG_PERROR(DEBUG1, "connect_to_host(): connect(), trying next");
 877
 878         close(server_socket);
 879     }
 880     /* Make sure we free the result from getaddrinfo(). */
 881     freeaddrinfo(gai_result);
 882
 883     if (server == NULL) {
 884         LOG_PERROR(WARNING, "connect_to_host(): no server found, abort");
 885         return -1;
 886     }
 887
 888     return server_socket;
 889 }
 890
 891
 892 /* Parse HTTP CONNECT request string and save its parameters.
 893  *
 894  * The following format is expected: "CONNECT host:port HTTP/1.x".
 895  *
 896  * request and host must have the same size! port must be at least 6 bytes
 897  * long (5 + '\0').
 898  */
 899 static int parse_request(const char *request, char *host, char *port,
 900                                               int *version_minor) {
 901     int port_unused; /* just used to verify the port is numeric */
 902     char *position;
 903
 904     /* scanf() doesn't check spaces. */
 905     if (strncmp(request, "CONNECT ", 8)) {
 906         return -1;
 907     }
 908     /* Check request and extract data, "host:port" is not yet separated. */
 909     if (sscanf(request, "CONNECT %s HTTP/1.%d", host, version_minor) != 2) {
 910         return -1;
 911     }
 912     /* Make sure ":port" is there. */
 913     if ((position = strchr(host, ':')) == NULL) {
 914         return -1;
 915     }
 916     /* Make sure port is numeric. */
 917     if (sscanf(position + 1, "%d", &port_unused) != 1) {
 918         return -1;
 919     }
 920     /* Store it in *port. */
 921     strncpy(port, position + 1, 5);
 922     port[5] = '\0';
 923     /* And remove port from host. */
 924     *position = '\0';
 925
 926     return 0;
 927 }
 928
 929
 930 static void log_session_information(gnutls_session_t session) {
 931     /* From doc/examples/ex-session-info.c of GnuTLS 3.2.3's tarball and
 932      * modified, thanks. */
 933
 934     const char *tmp;
 935     gnutls_credentials_type_t cred;
 936     gnutls_kx_algorithm_t kx;
 937     int dhe, ecdh;
 938
 939     dhe = 0;
 940     ecdh = 0;
 941
 942     /* Key exchange algorithm. */
 943     kx = gnutls_kx_get(session);
 944     LOG(DEBUG2, "- key exchange: %s", gnutls_kx_get_name(kx));
 945
 946     /* Authentication type. */
 947     cred = gnutls_auth_get_type(session);
 948     switch (cred) {
 949         case GNUTLS_CRD_CERTIFICATE:
 950             if (kx == GNUTLS_KX_DHE_RSA
 951                     || kx == GNUTLS_KX_DHE_DSS) {
 952                 dhe = 1;
 953 #ifdef GNUTLS_KX_ECDHE_RSA
 954             } else if (kx == GNUTLS_KX_ECDHE_RSA
 955                     || kx == GNUTLS_KX_ECDHE_ECDSA) {
 956                 ecdh = 1;
 957 #endif
 958             }
 959             break;
 960
 961         case GNUTLS_CRD_IA:
 962         case GNUTLS_CRD_SRP:
 963         case GNUTLS_CRD_PSK:
 964         case GNUTLS_CRD_ANON:
 965         default:
 966             /* This shouldn't occur. */
 967             LOG(WARNING, "unexpected authentication method: %d", cred);
 968             break;
 969     }
 970
 971     /* Information about key exchange. */
 972     if (dhe) {
 973         LOG(DEBUG2, "- ephemeral DH using prime of %d bits",
 974                     gnutls_dh_get_prime_bits(session));
 975     } else if (ecdh) {
 976 #ifdef GNUTLS_KX_ECDHE_RSA
 977         LOG(DEBUG2, "- ephemeral ECDH using curve %s",
 978                     gnutls_ecc_curve_get_name(gnutls_ecc_curve_get(session)));
 979 #endif
 980     }
 981
 982     tmp = gnutls_protocol_get_name(gnutls_protocol_get_version(session));
 983     LOG(DEBUG2, "- protocol: %s", tmp); /* e.g. TLS 1.0 */
 984
 985     tmp = gnutls_certificate_type_get_name(gnutls_certificate_type_get(session));
 986     LOG(DEBUG2, "- certificate type: %s", tmp);
 987
 988     tmp = gnutls_compression_get_name(gnutls_compression_get(session));
 989     LOG(DEBUG2, "- compression: %s", tmp);
 990
 991     tmp = gnutls_cipher_get_name(gnutls_cipher_get(session));
 992     LOG(DEBUG2, "- cipher: %s", tmp);
 993
 994     tmp = gnutls_mac_get_name(gnutls_mac_get(session));
 995     LOG(DEBUG2, "- MAC: %s", tmp);
 996 }