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        || !fd_ready(fd, tmo-time(NULL))
 131        || read(fd, s, 2) != 2
 132        )
 133       return FAIL;
 134     HDEBUG(D_transport|D_acl|D_v)
 135       debug_printf_indent("  SOCKS<< %02x %02x\n", s[0], s[1]);
 136     if (s[0] == AUTH_NAME_VER && s[1] == 0)
 137       {
 138       HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  socks auth OK\n");
 139       return OK;
 140       }
 141
 142     log_write(0, LOG_MAIN|LOG_PANIC, "socks auth failed");
 143     errno = EPROTO;
 144     return FAIL;
 145   }
 146 }
 147
 148
 149
 150 /* Find a suitable proxy to use from the list.
 151 Possible common code with spamd_get_server() ?
 152
 153 Return: index into proxy spec array, or -1
 154 */
 155
 156 static int
 157 socks_get_proxy(socks_opts * proxies, unsigned nproxies)
 158 {
 159 unsigned int i;
 160 socks_opts * sd;
 161 socks_opts * lim = &proxies[nproxies];
 162 long rnd, weights;
 163 unsigned pri;
 164 static BOOL srandomed = FALSE;
 165
 166 if (nproxies == 1)              /* shortcut, if we have only 1 server */
 167   return (proxies[0].is_failed ? -1 : 0);
 168
 169 /* init random */
 170 if (!srandomed)
 171   {
 172   struct timeval tv;
 173   gettimeofday(&tv, NULL);
 174   srandom((unsigned int)(tv.tv_usec/1000));
 175   srandomed = TRUE;
 176   }
 177
 178 /* scan for highest pri */
 179 for (pri = 0, sd = proxies; sd < lim; sd++)
 180   if (!sd->is_failed && sd->priority > pri)
 181     pri = sd->priority;
 182
 183 /* get sum of weights at this pri */
 184 for (weights = 0, sd = proxies; sd < lim; sd++)
 185   if (!sd->is_failed && sd->priority == pri)
 186     weights += sd->weight;
 187 if (weights == 0)       /* all servers failed */
 188   return -1;
 189
 190 for (rnd = random() % weights, i = 0; i < nproxies; i++)
 191   {
 192   sd = &proxies[i];
 193   if (!sd->is_failed && sd->priority == pri)
 194     if ((rnd -= sd->weight) <= 0)
 195       return i;
 196   }
 197
 198 log_write(0, LOG_MAIN|LOG_PANIC,
 199   "%s unknown error (memory/cpu corruption?)", __FUNCTION__);
 200 return -1;
 201 }
 202
 203
 204
 205 /* Make a connection via a socks proxy
 206
 207 Arguments:
 208  host           smtp target host
 209  host_af        address family
 210  port           remote tcp port number
 211  interface      local interface
 212  tb             transport
 213  timeout        connection timeout (zero for indefinite)
 214
 215 Return value:
 216  0 on success; -1 on failure, with errno set
 217 */
 218
 219 int
 220 socks_sock_connect(host_item * host, int host_af, int port, uschar * interface,
 221   transport_instance * tb, int timeout)
 222 {
 223 smtp_transport_options_block * ob =
 224   (smtp_transport_options_block *)tb->options_block;
 225 const uschar * proxy_list;
 226 const uschar * proxy_spec;
 227 int sep = 0;
 228 int fd;
 229 time_t tmo;
 230 const uschar * state;
 231 uschar buf[24];
 232 socks_opts proxies[32];                 /* max #proxies handled */
 233 unsigned nproxies;
 234 socks_opts * sob;
 235 unsigned size;
 236
 237 if (!timeout) timeout = 24*60*60;       /* use 1 day for "indefinite" */
 238 tmo = time(NULL) + timeout;
 239
 240 if (!(proxy_list = expand_string(ob->socks_proxy)))
 241   {
 242   log_write(0, LOG_MAIN|LOG_PANIC, "Bad expansion for socks_proxy in %s",
 243     tb->name);
 244   return -1;
 245   }
 246
 247 /* Read proxy list */
 248
 249 for (nproxies = 0;
 250         nproxies < nelem(proxies)
 251      && (proxy_spec = string_nextinlist(&proxy_list, &sep, NULL, 0));
 252      nproxies++)
 253   {
 254   int subsep = -' ';
 255   const uschar * option;
 256
 257   socks_option_defaults(sob = &proxies[nproxies]);
 258
 259   if (!(sob->proxy_host = string_nextinlist(&proxy_spec, &subsep, NULL, 0)))
 260     {
 261     /* paniclog config error */
 262     return -1;
 263     }
 264
 265   /*XXX consider global options eg. "hide socks_password = wibble" on the tpt */
 266   /* extract any further per-proxy options */
 267   while ((option = string_nextinlist(&proxy_spec, &subsep, NULL, 0)))
 268     socks_option(sob, option);
 269   }
 270
 271 /* Try proxies until a connection succeeds */
 272
 273 for(;;)
 274   {
 275   int idx;
 276   host_item proxy;
 277   int proxy_af;
 278
 279   if ((idx = socks_get_proxy(proxies, nproxies)) < 0)
 280     {
 281     HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  no proxies left\n");
 282     errno = EBUSY;
 283     return -1;
 284     }
 285   sob = &proxies[idx];
 286
 287   /* bodge up a host struct for the proxy */
 288   proxy.address = sob->proxy_host;
 289   proxy_af = Ustrchr(sob->proxy_host, ':') ? AF_INET6 : AF_INET;
 290
 291   if ((fd = smtp_sock_connect(&proxy, proxy_af, sob->port,
 292               interface, tb, sob->timeout)) >= 0)
 293     {
 294     proxy_local_address = string_copy(proxy.address);
 295     proxy_local_port = sob->port;
 296     break;
 297     }
 298
 299   log_write(0, LOG_MAIN, "%s: %s", __FUNCTION__, strerror(errno));
 300   sob->is_failed = TRUE;
 301   }
 302
 303 /* Do the socks protocol stuff */
 304 /* Send method-selection */
 305
 306 state = US"method select";
 307 HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  SOCKS>> 05 01 %02x\n", sob->auth_type);
 308 buf[0] = 5; buf[1] = 1; buf[2] = sob->auth_type;
 309 if (send(fd, buf, 3, 0) < 0)
 310   goto snd_err;
 311
 312 /* expect method response */
 313
 314 if (  !fd_ready(fd, tmo-time(NULL))
 315    || read(fd, buf, 2) != 2
 316    )
 317   goto rcv_err;
 318 HDEBUG(D_transport|D_acl|D_v)
 319   debug_printf_indent("  SOCKS<< %02x %02x\n", buf[0], buf[1]);
 320 if (  buf[0] != 5
 321    || socks_auth(fd, buf[1], sob, tmo) != OK
 322    )
 323   goto proxy_err;
 324
 325   {
 326   union sockaddr_46 sin;
 327   (void) ip_addr(&sin, host_af, host->address, port);
 328
 329   /* send connect (ipver, ipaddr, port) */
 330
 331   buf[0] = 5; buf[1] = 1; buf[2] = 0; buf[3] = host_af == AF_INET6 ? 4 : 1;
 332   #if HAVE_IPV6
 333   if (host_af == AF_INET6)
 334     {
 335     memcpy(buf+4, &sin.v6.sin6_addr,       sizeof(sin.v6.sin6_addr));
 336     memcpy(buf+4+sizeof(sin.v6.sin6_addr),
 337       &sin.v6.sin6_port, sizeof(sin.v6.sin6_port));
 338     size = 4+sizeof(sin.v6.sin6_addr)+sizeof(sin.v6.sin6_port);
 339     }
 340   else
 341   #endif
 342     {
 343     memcpy(buf+4, &sin.v4.sin_addr.s_addr, sizeof(sin.v4.sin_addr.s_addr));
 344     memcpy(buf+4+sizeof(sin.v4.sin_addr.s_addr),
 345       &sin.v4.sin_port, sizeof(sin.v4.sin_port));
 346     size = 4+sizeof(sin.v4.sin_addr.s_addr)+sizeof(sin.v4.sin_port);
 347     }
 348   }
 349
 350 state = US"connect";
 351 HDEBUG(D_transport|D_acl|D_v)
 352   {
 353   int i;
 354   debug_printf_indent("  SOCKS>>");
 355   for (i = 0; i<size; i++) debug_printf(" %02x", buf[i]);
 356   debug_printf("\n");
 357   }
 358 if (send(fd, buf, size, 0) < 0)
 359   goto snd_err;
 360
 361 /* expect conn-reply (success, local(ipver, addr, port))
 362 of same length as conn-request, or non-success fail code */
 363
 364 if (  !fd_ready(fd, tmo-time(NULL))
 365    || (size = read(fd, buf, size)) < 2
 366    )
 367   goto rcv_err;
 368 HDEBUG(D_transport|D_acl|D_v)
 369   {
 370   int i;
 371   debug_printf_indent("  SOCKS>>");
 372   for (i = 0; i<size; i++) debug_printf(" %02x", buf[i]);
 373   debug_printf("\n");
 374   }
 375 if (  buf[0] != 5
 376    || buf[1] != 0
 377    )
 378   goto proxy_err;
 379
 380 proxy_external_address = string_copy(
 381   host_ntoa(buf[3] == 4 ? AF_INET6 : AF_INET, buf+4, NULL, NULL));
 382 proxy_external_port = ntohs(*((uint16_t *)(buf + (buf[3] == 4 ? 20 : 8))));
 383 proxy_session = TRUE;
 384
 385 HDEBUG(D_transport|D_acl|D_v)
 386   debug_printf_indent("  proxy farside: [%s]:%d\n", proxy_external_address, proxy_external_port);
 387
 388 return fd;
 389
 390 snd_err:
 391   HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  proxy snd_err %s: %s\n", state, strerror(errno));
 392   return -1;
 393
 394 proxy_err:
 395   {
 396   struct socks_err * se =
 397     buf[1] > nelem(socks_errs) ? NULL : socks_errs + buf[1];
 398   HDEBUG(D_transport|D_acl|D_v)
 399     debug_printf_indent("  proxy %s: %s\n", state, se ? se->reason : US"unknown error code received");
 400   errno = se ? se->errcode : EPROTO;
 401   }
 402
 403 rcv_err:
 404   HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  proxy rcv_err %s: %s\n", state, strerror(errno));
 405   if (!errno) errno = EPROTO;
 406   else if (errno == ENOENT) errno = ECONNABORTED;
 407   return -1;
 408 }
 409
 410 #endif  /* entire file */
 411 /* vi: aw ai sw=2
 412 */