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_forwarding_failure(FILE *client_fd);
  66 static void tls_send_invalid_cert_message(gnutls_session_t session);
  67
  68 static void transfer_data(int client, int server);
  69 static int read_from_write_to(int from, int to);
  70 static void transfer_data_tls(int client, int server,
  71                               gnutls_session_t client_session,
  72                               gnutls_session_t server_session);
  73 static int read_from_write_to_tls(gnutls_session_t from, gnutls_session_t to,
  74                                   size_t buffer_size);
  75
  76 static int connect_to_host(const char *hostname, const char *port);
  77
  78 static int parse_request(const char *buffer, char *host, char *port,
  79                                              int *version_minor);
  80
  81
  82 void handle_connection(int client_socket) {
  83     int server_socket;
  84     FILE *client_fd_read, *client_fd_write, *server_fd_read, *server_fd_write;
  85
  86     char buffer[MAX_REQUEST_LINE];
  87     char host[MAX_REQUEST_LINE];
  88     char port[5 + 1];
  89
  90     int version_minor; /* x in HTTP/1.x */
  91     int result;
  92
  93     /* client_x509_cred is used when talking to the client (acting as a TSL
  94      * server), server_x509_cred is used when talking to the server (acting as
  95      * a TSL client). */
  96     gnutls_certificate_credentials_t client_x509_cred, server_x509_cred;
  97
  98     gnutls_session_t client_session, server_session;
  99     /* initialize_tls_session_*() called? - used for goto out */
 100     int client_session_init, server_session_init;
 101     /* gnutls_handshake() called? - used for goto out */
 102     int client_session_started, server_session_started;
 103     /* Validation failed? If yes we need to send the special "invalid"
 104      * certificate. */
 105     int validation_failed;
 106
 107     LOG(DEBUG, "new connection");
 108
 109     server_socket = -1;
 110     client_fd_read = NULL;
 111     client_fd_write = NULL;
 112     server_fd_read = NULL;
 113     server_fd_write = 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     if (fdopen_read_write(client_socket, &client_fd_read,
 121                                          &client_fd_write) != 0) {
 122         goto out;
 123     }
 124
 125     /* Read request line (CONNECT ..) and headers (they are discarded). */
 126     result = read_http_request(client_fd_read, buffer, sizeof(buffer));
 127     if (result == -1) {
 128         LOG(WARNING, "read_http_request(): client read error");
 129         goto out;
 130     } else if (result == -2) {
 131         LOG(WARNING, "read_http_request(): client EOF");
 132         send_bad_request(client_fd_write);
 133         goto out;
 134     }
 135
 136     if (parse_request(buffer, host, port, &version_minor) != 0) {
 137         LOG(WARNING, "bad request: %s", buffer);
 138         send_bad_request(client_fd_write);
 139         goto out;
 140     }
 141
 142     LOG(DEBUG, "target: %s:%s (HTTP 1.%d)", host, port, version_minor);
 143
 144     /* Connect to proxy server or directly to server. */
 145     if (global_proxy_host != NULL && global_proxy_port != NULL) {
 146         LOG(DEBUG, "connecting to %s:%s", global_proxy_host,
 147                                               global_proxy_port);
 148         server_socket = connect_to_host(global_proxy_host, global_proxy_port);
 149     } else {
 150         LOG(DEBUG, "connecting to %s:%s", host, port);
 151         server_socket = connect_to_host(host, port);
 152     }
 153
 154     if (server_socket == -1) {
 155         LOG(WARNING, "failed to connect to server");
 156         send_forwarding_failure(client_fd_write);
 157         goto out;
 158     }
 159     if (fdopen_read_write(server_socket, &server_fd_read,
 160                                          &server_fd_write) != 0) {
 161         send_forwarding_failure(client_fd_write);
 162         goto out;
 163     }
 164
 165     /* Connect to proxy if requested (command line option). */
 166     if (global_proxy_host != NULL && global_proxy_port != NULL) {
 167         fprintf(server_fd_write, "CONNECT %s:%s HTTP/1.0\r\n", host, port);
 168         fprintf(server_fd_write, "\r\n");
 169         fflush(server_fd_write);
 170
 171         /* Read response line from proxy server. */
 172         result = read_http_request(server_fd_read, buffer, sizeof(buffer));
 173         if (result == -1) {
 174             LOG(WARNING, "read_http_request(): proxy read error");
 175             send_forwarding_failure(client_fd_write);
 176             goto out;
 177         } else if (result == -2) {
 178             LOG(WARNING, "read_http_request(): proxy EOF");
 179             send_forwarding_failure(client_fd_write);
 180             goto out;
 181         }
 182
 183         /* Check response of proxy server. */
 184         if (strncmp(buffer, "HTTP/1.0 200", 12)) {
 185             LOG(WARNING, "bad proxy response: %s", buffer);
 186             send_forwarding_failure(client_fd_write);
 187             goto out;
 188         }
 189     }
 190
 191     LOG(DEBUG, "connection to server established");
 192
 193     /* If the -u option is used and we don't know this hostname's server
 194      * certificate then just pass through the connection and let the client
 195      * verify the server certificate. */
 196     if (global_passthrough_unknown) {
 197         char path[TLSPROXY_MAX_PATH_LENGTH];
 198         FILE *file = NULL;
 199
 200         if (server_certificate_file(&file, host, path, sizeof(path)) == -2) {
 201             /* We've established a connection, tell the client. */
 202             fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
 203             fprintf(client_fd_write, "\r\n");
 204             fflush(client_fd_write);
 205
 206             LOG(DEBUG, "transferring data");
 207
 208             /* Proxy data between client and server until one side is done
 209              * (EOF or error). */
 210             transfer_data(client_socket, server_socket);
 211
 212             LOG(DEBUG, "finished transferring data");
 213
 214             goto out;
 215         }
 216         /* server_certificate_file() may have opened the file, close it. */
 217         if (file != NULL) {
 218             fclose(file);
 219         }
 220     }
 221
 222     /* Initialize TLS client credentials to talk to the server. */
 223     result = initialize_tls_session_server(server_socket, &server_session,
 224                                                           &server_x509_cred);
 225     if (result != 0) {
 226         LOG(WARNING, "initialize_tls_session_server() failed");
 227         send_forwarding_failure(client_fd_write);
 228         goto out;
 229     }
 230     server_session_init = 1;
 231
 232     LOG(DEBUG, "starting server TLS handshake");
 233
 234     /* Try to establish TLS handshake between us and server. */
 235     result = gnutls_handshake(server_session);
 236     if (result != GNUTLS_E_SUCCESS) {
 237         LOG(WARNING, "server TLS handshake failed: %s",
 238                          gnutls_strerror(result));
 239         send_forwarding_failure(client_fd_write);
 240         goto out;
 241     }
 242     server_session_started = 1;
 243
 244     LOG(DEBUG, "server TLS handshake finished");
 245
 246     /* Make sure the server certificate is valid and known. */
 247     if (verify_tls_connection(server_session, host) != 0) {
 248         LOG(ERROR, "server certificate validation failed!");
 249         /* We'll send the error message over our TLS connection to the client,
 250          * but with an invalid certificate. No data is transfered from/to the
 251          * target server. */
 252         validation_failed = 1;
 253     }
 254
 255     /* Initialize TLS server credentials to talk to the client. */
 256     result = initialize_tls_session_client(client_socket,
 257                                            /* use a special host if the server
 258                                             * certificate was invalid */
 259                                            (validation_failed) ? "invalid"
 260                                                                : host,
 261                                            &client_session,
 262                                            &client_x509_cred);
 263     if (result != 0) {
 264         LOG(WARNING, "initialize_tls_session_client() failed");
 265         send_forwarding_failure(client_fd_write);
 266         goto out;
 267     }
 268     client_session_init = 1;
 269
 270     /* We've established a connection, tell the client. */
 271     fprintf(client_fd_write, "HTTP/1.0 200 Connection established\r\n");
 272     fprintf(client_fd_write, "\r\n");
 273     fflush(client_fd_write);
 274
 275     LOG(DEBUG, "starting client TLS handshake");
 276
 277     /* Try to establish TLS handshake between client and us. */
 278     result = gnutls_handshake(client_session);
 279     if (result != GNUTLS_E_SUCCESS) {
 280         LOG(WARNING, "client TLS handshake failed: %s",
 281                          gnutls_strerror(result));
 282         send_forwarding_failure(client_fd_write);
 283         goto out;
 284     }
 285     client_session_started = 1;
 286
 287     LOG(DEBUG, "client TLS handshake finished");
 288
 289     /* Tell the client that the verification failed. Shouldn't be necessary as
 290      * the client should terminate the connection because he received the
 291      * invalid certificate but better be sure. */
 292     if (validation_failed) {
 293         tls_send_invalid_cert_message(client_session);
 294         goto out;
 295     }
 296
 297     LOG(DEBUG, "transferring TLS data");
 298
 299     /* Proxy data between client and server until one side is done (EOF or
 300      * error). */
 301     transfer_data_tls(client_socket, server_socket,
 302                       client_session, server_session);
 303
 304     LOG(DEBUG, "finished transferring TLS data");
 305
 306 out:
 307     /* Close TLS sessions if necessary. Use GNUTLS_SHUT_RDWR so the data is
 308      * reliable transmitted. */
 309     if (server_session_started) {
 310         gnutls_bye(server_session, GNUTLS_SHUT_RDWR);
 311     }
 312     if (client_session_started) {
 313         gnutls_bye(client_session, GNUTLS_SHUT_RDWR);
 314     }
 315     if (server_session_init) {
 316         gnutls_deinit(server_session);
 317         gnutls_certificate_free_credentials(server_x509_cred);
 318     }
 319     if (client_session_init) {
 320         gnutls_deinit(client_session);
 321         gnutls_certificate_free_cas(client_x509_cred);
 322         gnutls_certificate_free_keys(client_x509_cred);
 323         gnutls_certificate_free_credentials(client_x509_cred);
 324     }
 325
 326     /* Close connection to server/proxy. */
 327     if (server_fd_read != NULL) {
 328         if (server_fd_write != NULL) {
 329             fclose(server_fd_write);
 330         }
 331         fclose(server_fd_read);
 332     } else if (server_socket != -1) {
 333         close(server_socket);
 334     }
 335     LOG(DEBUG, "connection to server closed");
 336     /* Close connection to client. */
 337     if (client_fd_read != NULL) {
 338         if (client_fd_write != NULL) {
 339             fclose(client_fd_write);
 340         }
 341         fclose(client_fd_read);
 342     } else {
 343         close(client_socket);
 344     }
 345     LOG(DEBUG, "connection to client closed");
 346
 347     LOG(DEBUG, "connection finished");
 348 }
 349
 350
 351 static int initialize_tls_session_client(int peer_socket,
 352         const char *hostname,
 353         gnutls_session_t *session,
 354         gnutls_certificate_credentials_t *x509_cred) {
 355     int result;
 356     int use_invalid_cert;
 357     char path[TLSPROXY_MAX_PATH_LENGTH];
 358
 359     /* The "invalid" hostname is special. If it's used we send an invalid
 360      * certificate to let the client know something is wrong. */
 361     use_invalid_cert = (!strcmp(hostname, "invalid"));
 362
 363     if (proxy_certificate_path(hostname, path, sizeof(path)) != 0) {
 364         LOG(ERROR,
 365             "initialize_tls_session_client(): \
 366 failed to get proxy certificate path");
 367         return -1;
 368     }
 369
 370     result = gnutls_certificate_allocate_credentials(x509_cred);
 371     if (result != GNUTLS_E_SUCCESS) {
 372         LOG(ERROR,
 373             "initialize_tls_session_client(): \
 374 gnutls_certificate_allocate_credentials(): %s",
 375             gnutls_strerror(result));
 376         return -1;
 377     }
 378
 379     /* Load proxy CA file, this CA "list" is send to the client. */
 380     if (!use_invalid_cert) {
 381         result = gnutls_certificate_set_x509_trust_file(*x509_cred,
 382                                                         PROXY_CA_FILE,
 383                                                         GNUTLS_X509_FMT_PEM);
 384         if (result <= 0) {
 385             LOG(ERROR,
 386                 "initialize_tls_session_client(): can't read CA file: '%s'",
 387                 PROXY_CA_FILE);
 388             gnutls_certificate_free_credentials(*x509_cred);
 389             return -1;
 390         }
 391     }
 392     /* If the invalid hostname was specified do nothing, we use a self-signed
 393      * certificate in this case. */
 394
 395     /* And certificate for this website and proxy's private key. */
 396     if (!use_invalid_cert) {
 397         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 398                                                       path, PROXY_KEY_FILE,
 399                                                       GNUTLS_X509_FMT_PEM);
 400     /* If the invalid hostname was specified load our special "invalid"
 401      * certificate. */
 402     } else {
 403         result = gnutls_certificate_set_x509_key_file(*x509_cred,
 404                                                       PROXY_INVALID_CERT_FILE,
 405                                                       PROXY_KEY_FILE,
 406                                                       GNUTLS_X509_FMT_PEM);
 407     }
 408     if (result != GNUTLS_E_SUCCESS) {
 409         LOG(ERROR,
 410             "initialize_tls_session_client(): \
 411 can't read server certificate ('%s') or key file ('%s'): %s",
 412             path, PROXY_KEY_FILE, gnutls_strerror(result));
 413         gnutls_certificate_free_credentials(*x509_cred);
 414         /* Could be a missing certificate. */
 415         return -2;
 416     }
 417
 418     gnutls_certificate_set_dh_params(*x509_cred, global_tls_dh_params);
 419
 420     result = gnutls_init(session, GNUTLS_SERVER);
 421     if (result != GNUTLS_E_SUCCESS) {
 422         LOG(ERROR,
 423             "initialize_tls_session_client(): gnutls_init(): %s",
 424             gnutls_strerror(result));
 425         gnutls_certificate_free_credentials(*x509_cred);
 426         return -1;
 427     }
 428     result = gnutls_priority_set(*session, global_tls_priority_cache);
 429     if (result != GNUTLS_E_SUCCESS) {
 430         LOG(ERROR,
 431             "initialize_tls_session_client(): gnutls_priority_set(): %s",
 432             gnutls_strerror(result));
 433         gnutls_deinit(*session);
 434         gnutls_certificate_free_credentials(*x509_cred);
 435         return -1;
 436     }
 437     result = gnutls_credentials_set(*session,
 438                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 439     if (result != GNUTLS_E_SUCCESS) {
 440         LOG(ERROR,
 441             "initialize_tls_session_client(): gnutls_credentials_set(): %s",
 442             gnutls_strerror(result));
 443         gnutls_deinit(*session);
 444         gnutls_certificate_free_credentials(*x509_cred);
 445         return -1;
 446     }
 447
 448     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 449
 450     return 0;
 451 }
 452 static int initialize_tls_session_server(int peer_socket,
 453         gnutls_session_t *session,
 454         gnutls_certificate_credentials_t *x509_cred) {
 455     int result;
 456
 457     result = gnutls_certificate_allocate_credentials(x509_cred);
 458     if (result != GNUTLS_E_SUCCESS) {
 459         LOG(ERROR,
 460             "initialize_tls_session_server(): \
 461 gnutls_certificate_allocate_credentials(): %s",
 462             gnutls_strerror(result));
 463         return -1;
 464     }
 465
 466     result = gnutls_init(session, GNUTLS_CLIENT);
 467     if (result != GNUTLS_E_SUCCESS) {
 468         LOG(ERROR,
 469             "initialize_tls_session_server(): gnutls_init(): %s",
 470             gnutls_strerror(result));
 471         gnutls_certificate_free_credentials(*x509_cred);
 472         return -1;
 473     }
 474     result = gnutls_priority_set(*session, global_tls_priority_cache);
 475     if (result != GNUTLS_E_SUCCESS) {
 476         LOG(ERROR,
 477             "initialize_tls_session_server(): gnutls_priority_set(): %s",
 478             gnutls_strerror(result));
 479         gnutls_deinit(*session);
 480         gnutls_certificate_free_credentials(*x509_cred);
 481         return -1;
 482     }
 483     result = gnutls_credentials_set(*session,
 484                                     GNUTLS_CRD_CERTIFICATE, *x509_cred);
 485     if (result != GNUTLS_E_SUCCESS) {
 486         LOG(ERROR,
 487             "initialize_tls_session_server(): gnutls_credentials_set(): %s",
 488             gnutls_strerror(result));
 489         gnutls_deinit(*session);
 490         gnutls_certificate_free_credentials(*x509_cred);
 491         return -1;
 492     }
 493
 494     gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
 495
 496     return 0;
 497 }
 498
 499
 500 static int fdopen_read_write(int socket, FILE **read_fd, FILE **write_fd) {
 501     *read_fd = fdopen(socket, "r");
 502     if (*read_fd == NULL) {
 503         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"r\") failed");
 504         return -1;
 505     }
 506
 507     *write_fd = fdopen(dup(socket), "w");
 508     if (*write_fd == NULL) {
 509         LOG_PERROR(WARNING, "fdopen_read_write(): fdopen(\"w\") failed");
 510         fclose(*read_fd);
 511         *read_fd = NULL; /* "tell" caller read_fd is already closed */
 512         return -1;
 513     }
 514
 515     return 0;
 516 }
 517
 518 /* Read HTTP request line and headers (ignored).
 519  *
 520  * On success 0 is returned, -1 on client error, -2 on unexpected EOF.
 521  */
 522 static int read_http_request(FILE *client_fd, char *request, size_t length) {
 523     char buffer[MAX_REQUEST_LINE];
 524
 525     if (fgets(request, (int)length, client_fd) == NULL) {
 526         if (ferror(client_fd)) {
 527             LOG_PERROR(WARNING, "read_http_request(): fgets()");
 528             return -1;
 529         }
 530         /* EOF */
 531         return -2;
 532     }
 533
 534     while (fgets(buffer, sizeof(buffer), client_fd) != NULL) {
 535         /* End of header. */
 536         if (!strcmp(buffer, "\n") || !strcmp(buffer, "\r\n")) {
 537             break;
 538         }
 539     }
 540     if (ferror(client_fd)) {
 541         LOG_PERROR(WARNING, "read_http_request(): fgets()");
 542         return -1;
 543     }
 544
 545     return 0;
 546 }
 547
 548 static void send_bad_request(FILE *client_fd) {
 549     const char error[] = "400 Bad Request";
 550     const char msg[]   = "Your browser sent an invalid request.";
 551     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 552     fflush(client_fd);
 553 }
 554 static void send_forwarding_failure(FILE *client_fd) {
 555     const char error[] = "503 Forwarding failure";
 556     const char msg[]   = "Failed to connect to server, check logs.";
 557     fprintf(client_fd, HTTP_RESPONSE_FORMAT, error, "", error, error, msg);
 558     fflush(client_fd);
 559 }
 560 static void tls_send_invalid_cert_message(gnutls_session_t session) {
 561     const char error[] = "500 Internal Server Error";
 562     const char msg[]   = "Server certificate validation failed, check logs.";
 563
 564     int result;
 565     char buffer[sizeof(HTTP_RESPONSE_FORMAT)
 566                 + 3 * sizeof(error) + sizeof(msg)];
 567
 568     result = snprintf(buffer, sizeof(buffer), HTTP_RESPONSE_FORMAT,
 569                                               error, "", error, error, msg);
 570     assert(result > 0 && (size_t)result < sizeof(buffer));
 571
 572     gnutls_record_send(session, buffer, strlen(buffer));
 573 }
 574
 575
 576 /* Transfer data between client and server sockets until one closes the
 577  * connection. */
 578 static void transfer_data(int client, int server) {
 579     struct pollfd fds[2];
 580     fds[0].fd      = client;
 581     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 582     fds[0].revents = 0;
 583     fds[1].fd      = server;
 584     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 585     fds[1].revents = 0;
 586
 587     for (;;) {
 588         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 589         if (result < 0) {
 590             LOG_PERROR(ERROR, "transfer_data(): poll()");
 591             return;
 592         }
 593
 594         /* Data available from client. */
 595         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 596             if (read_from_write_to(client, server) != 0) {
 597                 /* EOF (or other error) */
 598                 break;
 599             }
 600         }
 601         /* Data available from server. */
 602         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 603             if (read_from_write_to(server, client) != 0) {
 604                 /* EOF (or other error) */
 605                 break;
 606             }
 607         }
 608
 609         /* Client closed connection. */
 610         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 611             break;
 612         }
 613         /* Server closed connection. */
 614         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 615             break;
 616         }
 617     }
 618 }
 619
 620 /* Read available data from socket from and write it to socket to. At maximum
 621  * 4096 bytes are read/written. */
 622 static int read_from_write_to(int from, int to) {
 623     ssize_t size_read;
 624     ssize_t size_written;
 625     char buffer[4096];
 626
 627     LOG(DEBUG, "read_from_write_to(): %d -> %d", from, to);
 628
 629     size_read = read(from, buffer, sizeof(buffer));
 630     if (size_read < 0) {
 631         LOG_PERROR(WARNING, "read_from_write_to(): read()");
 632         return -1;
 633     /* EOF */
 634     } else if (size_read == 0) {
 635         return -1;
 636     }
 637
 638     size_written = write(to, buffer, (size_t)size_read);
 639     if (size_written < 0) {
 640         LOG_PERROR(WARNING, "read_from_write_to(): write()");
 641         return -1;
 642     }
 643     if (size_read != size_written) {
 644         LOG(ERROR, "read_from_write_to(): only written %ld of %ld bytes!",
 645                        (long int)size_written, (long int)size_read);
 646         return -1;
 647     }
 648
 649     return 0;
 650 }
 651
 652 /* Transfer data between client and server TLS connection until one closes the
 653  * connection. */
 654 static void transfer_data_tls(int client, int server,
 655                               gnutls_session_t client_session,
 656                               gnutls_session_t server_session) {
 657     size_t buffer_size;
 658
 659     struct pollfd fds[2];
 660     fds[0].fd      = client;
 661     fds[0].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 662     fds[0].revents = 0;
 663     fds[1].fd      = server;
 664     fds[1].events  = POLLIN | POLLPRI | POLLHUP | POLLERR;
 665     fds[1].revents = 0;
 666
 667     /* Get maximum possible buffer size. */
 668     buffer_size = gnutls_record_get_max_size(client_session);
 669     if (gnutls_record_get_max_size(server_session) < buffer_size) {
 670         buffer_size = gnutls_record_get_max_size(server_session);
 671     }
 672     LOG(DEBUG, "transfer_data_tls(): suggested buffer size: %ld",
 673                    (long int)buffer_size);
 674
 675     for (;;) {
 676         int result = poll(fds, 2 /* fd count */, -1 /* no timeout */);
 677         if (result < 0) {
 678             LOG_PERROR(ERROR, "transfer_data(): poll()");
 679             return;
 680         }
 681
 682         /* Data available from client. */
 683         if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
 684             if (read_from_write_to_tls(client_session, server_session,
 685                                        buffer_size) != 0) {
 686                 /* EOF (or other error) */
 687                 break;
 688             }
 689         }
 690         /* Data available from server. */
 691         if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
 692             if (read_from_write_to_tls(server_session, client_session,
 693                                        buffer_size) != 0) {
 694                 /* EOF (or other error) */
 695                 break;
 696             }
 697         }
 698
 699         /* Client closed connection. */
 700         if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
 701             break;
 702         }
 703         /* Server closed connection. */
 704         if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
 705             break;
 706         }
 707     }
 708 }
 709
 710 /* Read available data from session from and write to session to. */
 711 static int read_from_write_to_tls(gnutls_session_t from,
 712                                   gnutls_session_t to,
 713                                   size_t buffer_size) {
 714     ssize_t size_read;
 715     ssize_t size_written;
 716     char buffer[16384];
 717
 718     if (buffer_size > sizeof(buffer)) {
 719         buffer_size = sizeof(buffer);
 720     }
 721     LOG(DEBUG, "read_from_write_to_tls(): used buffer size: %ld",
 722                    (long int)buffer_size);
 723
 724     size_read = gnutls_record_recv(from, buffer, buffer_size);
 725     if (size_read < 0) {
 726         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_recv(): %s",
 727                          gnutls_strerror((int)size_read));
 728         return -1;
 729     /* EOF */
 730     } else if (size_read == 0) {
 731         return -1;
 732     }
 733
 734     size_written = gnutls_record_send(to, buffer, (size_t)size_read);
 735     if (size_written < 0) {
 736         LOG(WARNING, "read_from_write_to_tls(): gnutls_record_send(): %s",
 737                          gnutls_strerror((int)size_written));
 738         return -1;
 739     }
 740     if (size_read != size_written) {
 741         LOG(ERROR, "read_from_write_to_tls(): only written %ld of %ld bytes!",
 742                        (long int)size_written, (long int)size_read);
 743         return -1;
 744     }
 745
 746     return 0;
 747 }
 748
 749
 750 static int connect_to_host(const char *hostname, const char *port) {
 751     struct addrinfo gai_hints;
 752     struct addrinfo *gai_result;
 753     int gai_return;
 754
 755     int server_socket;
 756     struct addrinfo *server;
 757
 758     if (hostname == NULL || port == NULL) {
 759         return -1;
 760     }
 761
 762     /* Get IP of hostname server. */
 763     memset(&gai_hints, 0, sizeof(gai_hints));
 764     gai_hints.ai_family   = AF_UNSPEC;
 765     gai_hints.ai_socktype = SOCK_STREAM;
 766     gai_hints.ai_protocol = 0;
 767     gai_hints.ai_flags    = AI_NUMERICSERV /* given port is numeric */
 768                           | AI_ADDRCONFIG  /* supported by this computer */
 769                           | AI_V4MAPPED;   /* support IPv4 through IPv6 */
 770     gai_return = getaddrinfo(hostname, port, &gai_hints, &gai_result);
 771     if (gai_return != 0) {
 772         if (gai_return == EAI_SYSTEM) {
 773             LOG_PERROR(WARNING, "connect_to_host(): getaddrinfo()");
 774         } else {
 775             LOG(WARNING, "connect_to_host(): getaddrinfo(): %s",
 776                              gai_strerror(gai_return));
 777         }
 778         return -1;
 779     }
 780
 781     /* Now try to connect to each server returned by getaddrinfo(), use the
 782      * first successful connect. */
 783     for (server = gai_result; server != NULL; server = server->ai_next) {
 784         server_socket = socket(server->ai_family,
 785                                server->ai_socktype,
 786                                server->ai_protocol);
 787         if (server_socket == -1) {
 788             LOG_PERROR(DEBUG, "connect_to_host(): socket(), trying next");
 789             continue;
 790         }
 791
 792         if (connect(server_socket, server->ai_addr, server->ai_addrlen) != -1) {
 793             break;
 794         }
 795         LOG_PERROR(DEBUG, "connect_to_host(): connect(), trying next");
 796
 797         close(server_socket);
 798     }
 799     /* Make sure we free the result from getaddrinfo(). */
 800     freeaddrinfo(gai_result);
 801
 802     if (server == NULL) {
 803         LOG_PERROR(WARNING, "connect_to_host(): no server found, abort");
 804         return -1;
 805     }
 806
 807     return server_socket;
 808 }
 809
 810
 811 /* Parse HTTP CONNECT request string and save its parameters.
 812  *
 813  * The following format is expected: "CONNECT host:port HTTP/1.x".
 814  *
 815  * request and host must have the same size! port must be at least 6 bytes
 816  * long (5 + '\0').
 817  */
 818 static int parse_request(const char *request, char *host, char *port,
 819                                               int *version_minor) {
 820     int port_unused; /* just used to verify the port is numeric */
 821     char *position;
 822
 823     /* scanf() doesn't check spaces. */
 824     if (strncmp(request, "CONNECT ", 8)) {
 825         return -1;
 826     }
 827     /* Check request and extract data, "host:port" is not yet separated. */
 828     if (sscanf(request, "CONNECT %s HTTP/1.%d", host, version_minor) != 2) {
 829         return -1;
 830     }
 831     /* Make sure ":port" is there. */
 832     if ((position = strchr(host, ':')) == NULL) {
 833         return -1;
 834     }
 835     /* Make sure port is numeric. */
 836     if (sscanf(position + 1, "%d", &port_unused) != 1) {
 837         return -1;
 838     }
 839     /* Store it in *port. */
 840     strncpy(port, position + 1, 5);
 841     port[5] = '\0';
 842     /* And remove port from host. */
 843     *position = '\0';
 844
 845     return 0;
 846 }