src/src/transports/smtp_socks.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) Jeremy Harris 2015 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* SOCKS version 5 proxy, client-mode */
   9
  10 #include "../exim.h"
  11 #include "smtp.h"
  12
  13 #ifdef SUPPORT_SOCKS /* entire file */
  14
  15 #ifndef nelem
  16 # define nelem(arr) (sizeof(arr)/sizeof(*arr))
  17 #endif
  18
  19
  20 /* Defaults */
  21 #define SOCKS_PORT      1080
  22 #define SOCKS_TIMEOUT   5
  23 #define SOCKS_WEIGHT    1
  24 #define SOCKS_PRIORITY  1
  25
  26 #define AUTH_NONE       0
  27 #define AUTH_NAME       2               /* user/password per RFC 1929 */
  28 #define AUTH_NAME_VER   1
  29
  30 struct socks_err
  31   {
  32   uschar *      reason;
  33   int           errcode;
  34   } socks_errs[] =
  35   {
  36     {NULL, 0},
  37     {US"general SOCKS server failure",          EIO},
  38     {US"connection not allowed by ruleset",     EACCES},
  39     {US"Network unreachable",                   ENETUNREACH},
  40     {US"Host unreachable",                      EHOSTUNREACH},
  41     {US"Connection refused",                    ECONNREFUSED},
  42     {US"TTL expired",                           ECANCELED},
  43     {US"Command not supported",                 EOPNOTSUPP},
  44     {US"Address type not supported",            EAFNOSUPPORT}
  45   };
  46
  47 typedef struct
  48   {
  49   const uschar *        proxy_host;
  50   uschar                auth_type;      /* RFC 1928 encoding */
  51   const uschar *        auth_name;
  52   const uschar *        auth_pwd;
  53   short                 port;
  54   BOOL                  is_failed;
  55   unsigned              timeout;
  56   unsigned              weight;
  57   unsigned              priority;
  58   } socks_opts;
  59
  60 static void
  61 socks_option_defaults(socks_opts * sob)
  62 {
  63 sob->proxy_host = NULL;
  64 sob->auth_type =  AUTH_NONE;
  65 sob->auth_name =  US"";
  66 sob->auth_pwd =   US"";
  67 sob->is_failed =  FALSE;
  68 sob->port =       SOCKS_PORT;
  69 sob->timeout =    SOCKS_TIMEOUT;
  70 sob->weight =     SOCKS_WEIGHT;
  71 sob->priority =   SOCKS_PRIORITY;
  72 }
  73
  74 static void
  75 socks_option(socks_opts * sob, const uschar * opt)
  76 {
  77 const uschar * s;
  78
  79 if (Ustrncmp(opt, "auth=", 5) == 0)
  80   {
  81   opt += 5;
  82   if (Ustrcmp(opt, "none") == 0)        sob->auth_type = AUTH_NONE;
  83   else if (Ustrcmp(opt, "name") == 0)   sob->auth_type = AUTH_NAME;
  84   }
  85 else if (Ustrncmp(opt, "name=", 5) == 0)
  86   sob->auth_name = opt + 5;
  87 else if (Ustrncmp(opt, "pass=", 5) == 0)
  88   sob->auth_pwd = opt + 5;
  89 else if (Ustrncmp(opt, "port=", 5) == 0)
  90   sob->port = atoi(opt + 5);
  91 else if (Ustrncmp(opt, "tmo=", 4) == 0)
  92   sob->timeout = atoi(opt + 4);
  93 else if (Ustrncmp(opt, "pri=", 4) == 0)
  94   sob->priority = atoi(opt + 4);
  95 else if (Ustrncmp(opt, "weight=", 7) == 0)
  96   sob->weight = atoi(opt + 7);
  97 return;
  98 }
  99
 100 static int
 101 socks_auth(int fd, int method, socks_opts * sob, time_t tmo)
 102 {
 103 uschar * s;
 104 int len, i, j;
 105
 106 switch(method)
 107   {
 108   default:
 109     log_write(0, LOG_MAIN|LOG_PANIC,
 110       "Unrecognised socks auth method %d", method);
 111     return FAIL;
 112   case AUTH_NONE:
 113     return OK;
 114   case AUTH_NAME:
 115     HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  socks auth NAME '%s' '%s'\n",
 116       sob->auth_name, sob->auth_pwd);
 117     i = Ustrlen(sob->auth_name);
 118     j = Ustrlen(sob->auth_pwd);
 119     s = string_sprintf("%c%c%.255s%c%.255s", AUTH_NAME_VER,
 120       i, sob->auth_name, j, sob->auth_pwd);
 121     len = i + j + 3;
 122     HDEBUG(D_transport|D_acl|D_v)
 123       {
 124       int i;
 125       debug_printf_indent("  SOCKS>>");
 126       for (i = 0; i<len; i++) debug_printf(" %02x", s[i]);
 127       debug_printf("\n");
 128       }
 129     if (send(fd, s, len, 0) < 0)
 130       return FAIL;
 131 #ifdef TCP_QUICKACK
 132     (void) setsockopt(fd, IPPROTO_TCP, TCP_QUICKACK, US &off, sizeof(off));
 133 #endif
 134     if (!fd_ready(fd, tmo-time(NULL)) || read(fd, s, 2) != 2)
 135       return FAIL;
 136     HDEBUG(D_transport|D_acl|D_v)
 137       debug_printf_indent("  SOCKS<< %02x %02x\n", s[0], s[1]);
 138     if (s[0] == AUTH_NAME_VER && s[1] == 0)
 139       {
 140       HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  socks auth OK\n");
 141       return OK;
 142       }
 143
 144     log_write(0, LOG_MAIN|LOG_PANIC, "socks auth failed");
 145     errno = EPROTO;
 146     return FAIL;
 147   }
 148 }
 149
 150
 151
 152 /* Find a suitable proxy to use from the list.
 153 Possible common code with spamd_get_server() ?
 154
 155 Return: index into proxy spec array, or -1
 156 */
 157
 158 static int
 159 socks_get_proxy(socks_opts * proxies, unsigned nproxies)
 160 {
 161 unsigned int i;
 162 socks_opts * sd;
 163 socks_opts * lim = &proxies[nproxies];
 164 long rnd, weights;
 165 unsigned pri;
 166 static BOOL srandomed = FALSE;
 167
 168 if (nproxies == 1)              /* shortcut, if we have only 1 server */
 169   return (proxies[0].is_failed ? -1 : 0);
 170
 171 /* init random */
 172 if (!srandomed)
 173   {
 174   struct timeval tv;
 175   gettimeofday(&tv, NULL);
 176   srandom((unsigned int)(tv.tv_usec/1000));
 177   srandomed = TRUE;
 178   }
 179
 180 /* scan for highest pri */
 181 for (pri = 0, sd = proxies; sd < lim; sd++)
 182   if (!sd->is_failed && sd->priority > pri)
 183     pri = sd->priority;
 184
 185 /* get sum of weights at this pri */
 186 for (weights = 0, sd = proxies; sd < lim; sd++)
 187   if (!sd->is_failed && sd->priority == pri)
 188     weights += sd->weight;
 189 if (weights == 0)       /* all servers failed */
 190   return -1;
 191
 192 for (rnd = random() % weights, i = 0; i < nproxies; i++)
 193   {
 194   sd = &proxies[i];
 195   if (!sd->is_failed && sd->priority == pri)
 196     if ((rnd -= sd->weight) <= 0)
 197       return i;
 198   }
 199
 200 log_write(0, LOG_MAIN|LOG_PANIC,
 201   "%s unknown error (memory/cpu corruption?)", __FUNCTION__);
 202 return -1;
 203 }
 204
 205
 206
 207 /* Make a connection via a socks proxy
 208
 209 Arguments:
 210  host           smtp target host
 211  host_af        address family
 212  port           remote tcp port number
 213  interface      local interface
 214  tb             transport
 215  timeout        connection timeout (zero for indefinite)
 216
 217 Return value:
 218  0 on success; -1 on failure, with errno set
 219 */
 220
 221 int
 222 socks_sock_connect(host_item * host, int host_af, int port, uschar * interface,
 223   transport_instance * tb, int timeout)
 224 {
 225 smtp_transport_options_block * ob =
 226   (smtp_transport_options_block *)tb->options_block;
 227 const uschar * proxy_list;
 228 const uschar * proxy_spec;
 229 int sep = 0;
 230 int fd;
 231 time_t tmo;
 232 const uschar * state;
 233 uschar buf[24];
 234 socks_opts proxies[32];                 /* max #proxies handled */
 235 unsigned nproxies;
 236 socks_opts * sob;
 237 unsigned size;
 238 blob early_data;
 239
 240 if (!timeout) timeout = 24*60*60;       /* use 1 day for "indefinite" */
 241 tmo = time(NULL) + timeout;
 242
 243 if (!(proxy_list = expand_string(ob->socks_proxy)))
 244   {
 245   log_write(0, LOG_MAIN|LOG_PANIC, "Bad expansion for socks_proxy in %s",
 246     tb->name);
 247   return -1;
 248   }
 249
 250 /* Read proxy list */
 251
 252 for (nproxies = 0;
 253         nproxies < nelem(proxies)
 254      && (proxy_spec = string_nextinlist(&proxy_list, &sep, NULL, 0));
 255      nproxies++)
 256   {
 257   int subsep = -' ';
 258   const uschar * option;
 259
 260   socks_option_defaults(sob = &proxies[nproxies]);
 261
 262   if (!(sob->proxy_host = string_nextinlist(&proxy_spec, &subsep, NULL, 0)))
 263     {
 264     /* paniclog config error */
 265     return -1;
 266     }
 267
 268   /*XXX consider global options eg. "hide socks_password = wibble" on the tpt */
 269   /* extract any further per-proxy options */
 270   while ((option = string_nextinlist(&proxy_spec, &subsep, NULL, 0)))
 271     socks_option(sob, option);
 272   }
 273
 274 /* Set up the socks protocol method-selection message,
 275 for sending on connection */
 276
 277 state = US"method select";
 278 buf[0] = 5; buf[1] = 1; buf[2] = sob->auth_type;
 279 early_data.data = buf;
 280 early_data.len = 3;
 281
 282 /* Try proxies until a connection succeeds */
 283
 284 for(;;)
 285   {
 286   int idx;
 287   host_item proxy;
 288   int proxy_af;
 289
 290   if ((idx = socks_get_proxy(proxies, nproxies)) < 0)
 291     {
 292     HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  no proxies left\n");
 293     errno = EBUSY;
 294     return -1;
 295     }
 296   sob = &proxies[idx];
 297
 298   /* bodge up a host struct for the proxy */
 299   proxy.address = proxy.name = sob->proxy_host;
 300   proxy_af = Ustrchr(sob->proxy_host, ':') ? AF_INET6 : AF_INET;
 301
 302   if ((fd = smtp_sock_connect(&proxy, proxy_af, sob->port,
 303               interface, tb, sob->timeout, &early_data)) >= 0)
 304     {
 305     proxy_local_address = string_copy(proxy.address);
 306     proxy_local_port = sob->port;
 307     break;
 308     }
 309
 310   log_write(0, LOG_MAIN, "%s: %s", __FUNCTION__, strerror(errno));
 311   sob->is_failed = TRUE;
 312   }
 313
 314 /* Do the socks protocol stuff */
 315
 316 HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  SOCKS>> 05 01 %02x\n", sob->auth_type);
 317
 318 /* expect method response */
 319
 320 #ifdef TCP_QUICKACK
 321 (void) setsockopt(fd, IPPROTO_TCP, TCP_QUICKACK, US &off, sizeof(off));
 322 #endif
 323
 324 if (  !fd_ready(fd, tmo-time(NULL))
 325    || read(fd, buf, 2) != 2
 326    )
 327   goto rcv_err;
 328 HDEBUG(D_transport|D_acl|D_v)
 329   debug_printf_indent("  SOCKS<< %02x %02x\n", buf[0], buf[1]);
 330 if (  buf[0] != 5
 331    || socks_auth(fd, buf[1], sob, tmo) != OK
 332    )
 333   goto proxy_err;
 334
 335   {
 336   union sockaddr_46 sin;
 337   (void) ip_addr(&sin, host_af, host->address, port);
 338
 339   /* send connect (ipver, ipaddr, port) */
 340
 341   buf[0] = 5; buf[1] = 1; buf[2] = 0; buf[3] = host_af == AF_INET6 ? 4 : 1;
 342   #if HAVE_IPV6
 343   if (host_af == AF_INET6)
 344     {
 345     memcpy(buf+4, &sin.v6.sin6_addr,       sizeof(sin.v6.sin6_addr));
 346     memcpy(buf+4+sizeof(sin.v6.sin6_addr),
 347       &sin.v6.sin6_port, sizeof(sin.v6.sin6_port));
 348     size = 4+sizeof(sin.v6.sin6_addr)+sizeof(sin.v6.sin6_port);
 349     }
 350   else
 351   #endif
 352     {
 353     memcpy(buf+4, &sin.v4.sin_addr.s_addr, sizeof(sin.v4.sin_addr.s_addr));
 354     memcpy(buf+4+sizeof(sin.v4.sin_addr.s_addr),
 355       &sin.v4.sin_port, sizeof(sin.v4.sin_port));
 356     size = 4+sizeof(sin.v4.sin_addr.s_addr)+sizeof(sin.v4.sin_port);
 357     }
 358   }
 359
 360 state = US"connect";
 361 HDEBUG(D_transport|D_acl|D_v)
 362   {
 363   int i;
 364   debug_printf_indent("  SOCKS>>");
 365   for (i = 0; i<size; i++) debug_printf(" %02x", buf[i]);
 366   debug_printf("\n");
 367   }
 368 if (send(fd, buf, size, 0) < 0)
 369   goto snd_err;
 370
 371 /* expect conn-reply (success, local(ipver, addr, port))
 372 of same length as conn-request, or non-success fail code */
 373
 374 if (  !fd_ready(fd, tmo-time(NULL))
 375    || (size = read(fd, buf, size)) < 2
 376    )
 377   goto rcv_err;
 378 HDEBUG(D_transport|D_acl|D_v)
 379   {
 380   int i;
 381   debug_printf_indent("  SOCKS>>");
 382   for (i = 0; i<size; i++) debug_printf(" %02x", buf[i]);
 383   debug_printf("\n");
 384   }
 385 if (  buf[0] != 5
 386    || buf[1] != 0
 387    )
 388   goto proxy_err;
 389
 390 proxy_external_address = string_copy(
 391   host_ntoa(buf[3] == 4 ? AF_INET6 : AF_INET, buf+4, NULL, NULL));
 392 proxy_external_port = ntohs(*((uint16_t *)(buf + (buf[3] == 4 ? 20 : 8))));
 393 proxy_session = TRUE;
 394
 395 HDEBUG(D_transport|D_acl|D_v)
 396   debug_printf_indent("  proxy farside: [%s]:%d\n", proxy_external_address, proxy_external_port);
 397
 398 return fd;
 399
 400 snd_err:
 401   HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  proxy snd_err %s: %s\n", state, strerror(errno));
 402   return -1;
 403
 404 proxy_err:
 405   {
 406   struct socks_err * se =
 407     buf[1] > nelem(socks_errs) ? NULL : socks_errs + buf[1];
 408   HDEBUG(D_transport|D_acl|D_v)
 409     debug_printf_indent("  proxy %s: %s\n", state, se ? se->reason : US"unknown error code received");
 410   errno = se ? se->errcode : EPROTO;
 411   }
 412
 413 rcv_err:
 414   HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  proxy rcv_err %s: %s\n", state, strerror(errno));
 415   if (!errno) errno = EPROTO;
 416   else if (errno == ENOENT) errno = ECONNABORTED;
 417   return -1;
 418 }
 419
 420 #endif  /* entire file */
 421 /* vi: aw ai sw=2
 422 */