tor-smtp/tor-smtp.c

   1 /*
   2  * tor-smtp
   3  *
   4  * Copyright (c) 2006 Johannes Berg <johannes@sipsolutions.net>
   5  *
   6  * The bidicopy() routine is from OpenBSD's netcat rewrite, plus patches
   7  * from the fedora project.
   8  *
   9  * Copyright (c) 2001 Eric Jackson <ericj@monkey.org>
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  *
  15  * 1. Redistributions of source code must retain the above copyright
  16  *   notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *   notice, this list of conditions and the following disclaimer in the
  19  *   documentation and/or other materials provided with the distribution.
  20  * 3. The name of the author may not be used to endorse or promote products
  21  *   derived from this software without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
  24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  25  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  26  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  27  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  28  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  29  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  30  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  31  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  32  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  33  */
  34 #include <sys/types.h>
  35 #include <sys/socket.h>
  36 #include <netdb.h>
  37 #include <stdlib.h>
  38 #include <sys/poll.h>
  39 #include <stdio.h>
  40 #include <string.h>
  41 #include <errno.h>
  42 #include <unistd.h>
  43 #include <sys/time.h>
  44 #include <time.h>
  45 #include <syslog.h>
  46 /* for BSD: htons is in there: */
  47 #include <arpa/inet.h>
  48 #include "atomicio.h"
  49
  50 //#define DEBUG(str,args...) fprintf(stderr, str, ##args);
  51 #define DEBUG(str,args...) do {} while(0)
  52
  53 int read_bytes_timeout(int fd, char *buf, int bytes, int timeout)
  54 {
  55 # define DEBUG_RETURN(str,args...) do { DEBUG(str, ##args); return 0; } while (0)
  56         struct pollfd pollfd = { .fd = fd, .events = POLLIN };
  57         struct timeval tv_start, tv_now;
  58         int got = 0, tmp;
  59
  60         gettimeofday(&tv_start, NULL);
  61
  62         while (got < bytes && timeout >= 0) {
  63                 if (poll(&pollfd, 1, timeout*1000) <= 0)
  64                         DEBUG_RETURN("poll failed: %d (got %d)\n", errno, got);
  65                 gettimeofday(&tv_now, NULL);
  66                 timeout -= tv_now.tv_sec - tv_start.tv_sec;
  67                 tv_start = tv_now;
  68
  69                 tmp = read(fd, buf+got, bytes-got);
  70                 if (tmp <= 0)
  71                         DEBUG_RETURN("read failed: %d\n", errno);
  72                 got += tmp;
  73         }
  74         return bytes;
  75 #undef DEBUG_RETURN
  76 }
  77
  78 int connect_via_tor(const char *tor_server, const char *tor_port,
  79                     const char *remote_server, short remote_port)
  80 {
  81         int fd;
  82         struct addrinfo *res = NULL;
  83         char socks_init[] = { 5, 1, 0 };
  84         char buf[255+7]; /* must be less than 255+7+1 bytes long */
  85         int remote_server_len = strlen(remote_server);
  86
  87         if (remote_server_len > sizeof(buf)-7/*5 leading bytes and port */)
  88                 return -1;
  89
  90         fd = socket(PF_INET, SOCK_STREAM, 0);
  91         if (fd == -1) {
  92                 DEBUG("failed to create socket\n");
  93                 return -1;
  94         }
  95
  96 #define DEBUG_OUT(str, args...) do { DEBUG(str,##args); goto out_close; } while (0)
  97
  98         if (getaddrinfo(tor_server, tor_port, NULL, &res))
  99                 DEBUG_OUT("getaddrinfo\n");
 100         if (!res)
 101                 DEBUG_OUT("getaddrinfo returned empty set\n");
 102
 103         if (connect(fd, res->ai_addr, res->ai_addrlen))
 104                 DEBUG_OUT("failed to connect\n");
 105
 106         /* now that we are connected, set up SOCKS */
 107         if (write(fd, &socks_init, sizeof(socks_init)) != sizeof(socks_init))
 108                 goto out_close;
 109         if (!read_bytes_timeout(fd, &buf[0], 2, 120))
 110                 goto out_close;
 111         if (buf[0] != 5 || buf[1] != 0)
 112                 goto out_close;
 113
 114         buf[0] = 5;
 115         buf[1] = 1;
 116         buf[2] = 0;
 117         buf[3] = 3;
 118         buf[4] = remote_server_len;
 119         strcpy(buf+5, remote_server);
 120         *(short*) (buf+5+remote_server_len) = htons(remote_port);
 121         if (write(fd, buf, 5+remote_server_len+2) != 5+remote_server_len+2)
 122                 goto out_close;
 123         if (!read_bytes_timeout(fd, buf, 4, 120))
 124                 goto out_close;
 125         if (buf[0] != 5 || buf[1] != 0)
 126                 goto out_close;
 127         /* read rest of the response */
 128         switch(buf[3]) {
 129         case 1:
 130                 if (!read_bytes_timeout(fd, buf, 6, 120))
 131                         goto out_close;
 132                 break;
 133         /* TODO handle other responses */
 134         }
 135         freeaddrinfo(res);
 136
 137         return fd;
 138  out_close:
 139         close(fd);
 140         return -1;
 141 }
 142
 143 /* read at most buflen characters into buffer,
 144  * until linefeed is encountered.
 145  * NB: if more characters are received they are discarded!
 146  */
 147 int readline(int fd, char *buf, int buflen, int timeout)
 148 {
 149 # define DEBUG_RETURN(str,args...) do { DEBUG(str, ##args); return 0; } while (0)
 150         struct pollfd pollfd = { .fd = fd, .events = POLLIN };
 151         struct timeval tv_start, tv_now;
 152         int got = 0, tmp;
 153         char *match;
 154
 155         gettimeofday(&tv_start, NULL);
 156
 157         while (got < buflen && timeout >= 0) {
 158                 if (poll(&pollfd, 1, timeout*1000) <= 0)
 159                         DEBUG_RETURN("poll failed: %d (got %d)\n", errno, got);
 160                 gettimeofday(&tv_now, NULL);
 161                 timeout -= tv_now.tv_sec - tv_start.tv_sec;
 162                 tv_start = tv_now;
 163
 164                 tmp = read(fd, buf+got, buflen-got);
 165                 if (tmp <= 0)
 166                         DEBUG_RETURN("read failed: %d\n", errno);
 167                 match = memchr(buf+got, '\n', tmp);
 168                 if (match) {
 169                         if (*(match-1) == '\r')
 170                                 match--;
 171                         *match = '\0';
 172                         return match-buf;
 173                 }
 174                 got += tmp;
 175         }
 176         return -1;
 177 #undef DEBUG_RETURN
 178 }
 179
 180 /*
 181  * readwrite()
 182  * Loop that polls on the network file descriptor and stdin.
 183  */
 184 void
 185 bidicopy(int nfd)
 186 {
 187         struct pollfd pfd[2];
 188         unsigned char buf[8192];
 189         int n, wfd = fileno(stdin);
 190         int lfd = fileno(stdout);
 191         int plen;
 192
 193         plen = 1024;
 194
 195         /* Setup Network FD */
 196         pfd[0].fd = nfd;
 197         pfd[0].events = POLLIN;
 198
 199         /* Set up STDIN FD. */
 200         pfd[1].fd = wfd;
 201         pfd[1].events = POLLIN;
 202
 203         while (pfd[0].fd != -1) {
 204                 if ((n = poll(pfd, 2, -1)) < 0) {
 205                         close(nfd);
 206                         return;
 207                 }
 208
 209                 if (n == 0)
 210                         return;
 211
 212                 if (pfd[0].revents & POLLIN) {
 213                         if ((n = read(nfd, buf, plen)) < 0)
 214                                 return;
 215                         else if (n == 0) {
 216                                 goto shutdown_rd;
 217                         } else {
 218                                 if (atomicio(vwrite, lfd, buf, n) != n)
 219                                         return;
 220                         }
 221                 }
 222                 else if (pfd[0].revents & POLLHUP) {
 223                 shutdown_rd:
 224                         shutdown(nfd, SHUT_RD);
 225                         pfd[0].fd = -1;
 226                         pfd[0].events = 0;
 227                 }
 228
 229                 if (1) {
 230                     if(pfd[1].revents & POLLIN) {
 231                         if ((n = read(wfd, buf, plen)) < 0)
 232                                 return;
 233                         else if (n == 0) {
 234                                 goto shutdown_wr;
 235                         } else {
 236                                 if (atomicio(vwrite, nfd, buf, n) != n)
 237                                         return;
 238                         }
 239                     }
 240                     else if (pfd[1].revents & POLLHUP) {
 241                     shutdown_wr:
 242                         shutdown(nfd, SHUT_WR);
 243                         pfd[1].fd = -1;
 244                         pfd[1].events = 0;
 245                     }
 246                 }
 247         }
 248 }
 249
 250 int main(int argc, char **argv)
 251 {
 252         char *tor_server = "localhost";
 253         char *tor_port = "9050";
 254         char *remote_server = NULL;
 255         char *tmp;
 256         char local_onion[255];
 257         char buf[255], buf2[255];
 258         int linelen;
 259         int fd;
 260
 261         if (argc >= 2)
 262                 tor_server = argv[1];
 263         if (argc >= 3)
 264                 tor_port = argv[2];
 265         if (argc > 3 || (tor_server && (!strcasecmp(tor_server, "--help") || !strcasecmp(tor_server, "-h")))) {
 266                 fprintf(stderr, "tor-smtp [tor-server] [tor-port]\n");
 267                 fprintf(stderr, "     (default localhost 9050)\n");
 268                 return 2;
 269         }
 270
 271         openlog("tor-smtp", LOG_PID, LOG_MAIL);
 272
 273         printf("220 Welcome\r\n");
 274         fflush(stdout);
 275
 276  command:
 277         if ((linelen = readline(0, buf, sizeof(buf), 30)) < 0) {
 278                 printf("421 connection timed out\r\n");
 279                 fflush(stdout);
 280                 return 0;
 281         }
 282         if (linelen < 4) {
 283                 goto invalid;
 284         }
 285         if (!strncasecmp("QUIT", buf, 4)) {
 286                 printf("221 closing connection\r\n");
 287                 fflush(stdout);
 288                 return 0;
 289         }
 290         if (!strncasecmp("EHLO ", buf, 5) || !strncasecmp("HELO ", buf, 5))
 291                 goto helo_continue;
 292  invalid:
 293         printf("500 invalid command\r\n");
 294         fflush(stdout);
 295         goto command;
 296
 297  helo_continue:
 298         tmp = strtok(buf+5, " ");
 299         if (!tmp) {
 300                 printf("500 invalid EHLO/HELO: missing local name\n");
 301                 fflush(stdout);
 302                 goto command;
 303         }
 304         remote_server = strtok(NULL, " ");
 305         if (!remote_server) {
 306                 printf("500 invalid EHLO/HELO: missing remote name\n");
 307                 goto command;
 308         }
 309         strncpy(local_onion, tmp, sizeof(local_onion));
 310         fd = connect_via_tor(tor_server, tor_port, remote_server, 25);
 311         if (fd < 0) {
 312                 printf("421 could not connect\r\n");
 313                 fflush(stdout);
 314                 syslog(LOG_WARNING, "tor connection to %s failed",
 315                        remote_server);
 316                 return 0;
 317         }
 318
 319         linelen = readline(fd, buf2, sizeof(buf2), 120);
 320         if (linelen < 0) {
 321                 printf("421 could not connect\r\n");
 322                 fflush(stdout);
 323                 syslog(LOG_WARNING, "no welcome message from %s", remote_server);
 324                 return 0;
 325         }
 326         if (strncmp("220 ", buf2, 4)) {
 327                 printf("421 server seems to not like us\r\n");
 328                 DEBUG("answer was: %s\n", buf2);
 329                 fflush(stdout);
 330                 return 0;
 331         }
 332
 333         strncpy(buf+5, local_onion, sizeof(buf)-5);
 334         linelen = strlen(buf);
 335         *(buf+linelen) = '\r';
 336         *(buf+linelen+1) = '\n';
 337         write(fd, buf, linelen+2);
 338
 339         close(2); /* get rid of stderr */
 340         /* now "all" we have to do is do a bidirectional copy of fd and stdio */
 341         bidicopy(fd);
 342         return 0;
 343 }