src/src/smtp_out.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2016 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* A number of functions for driving outgoing SMTP calls. */
   9
  10
  11 #include "exim.h"
  12 #include "transports/smtp.h"
  13
  14
  15
  16 /*************************************************
  17 *           Find an outgoing interface           *
  18 *************************************************/
  19
  20 /* This function is called from the smtp transport and also from the callout
  21 code in verify.c. Its job is to expand a string to get a list of interfaces,
  22 and choose a suitable one (IPv4 or IPv6) for the outgoing address.
  23
  24 Arguments:
  25   istring    string interface setting, may be NULL, meaning "any", in
  26                which case the function does nothing
  27   host_af    AF_INET or AF_INET6 for the outgoing IP address
  28   addr       the mail address being handled (for setting errors)
  29   interface  point this to the interface
  30   msg        to add to any error message
  31
  32 Returns:     TRUE on success, FALSE on failure, with error message
  33                set in addr and transport_return set to PANIC
  34 */
  35
  36 BOOL
  37 smtp_get_interface(uschar *istring, int host_af, address_item *addr,
  38   uschar **interface, uschar *msg)
  39 {
  40 const uschar * expint;
  41 uschar *iface;
  42 int sep = 0;
  43
  44 if (!istring) return TRUE;
  45
  46 if (!(expint = expand_string(istring)))
  47   {
  48   if (expand_string_forcedfail) return TRUE;
  49   addr->transport_return = PANIC;
  50   addr->message = string_sprintf("failed to expand \"interface\" "
  51       "option for %s: %s", msg, expand_string_message);
  52   return FALSE;
  53   }
  54
  55 while (isspace(*expint)) expint++;
  56 if (*expint == 0) return TRUE;
  57
  58 while ((iface = string_nextinlist(&expint, &sep, big_buffer,
  59           big_buffer_size)))
  60   {
  61   if (string_is_ip_address(iface, NULL) == 0)
  62     {
  63     addr->transport_return = PANIC;
  64     addr->message = string_sprintf("\"%s\" is not a valid IP "
  65       "address for the \"interface\" option for %s",
  66       iface, msg);
  67     return FALSE;
  68     }
  69
  70   if (((Ustrchr(iface, ':') == NULL)? AF_INET:AF_INET6) == host_af)
  71     break;
  72   }
  73
  74 if (iface) *interface = string_copy(iface);
  75 return TRUE;
  76 }
  77
  78
  79
  80 /*************************************************
  81 *           Find an outgoing port                *
  82 *************************************************/
  83
  84 /* This function is called from the smtp transport and also from the callout
  85 code in verify.c. Its job is to find a port number. Note that getservbyname()
  86 produces the number in network byte order.
  87
  88 Arguments:
  89   rstring     raw (unexpanded) string representation of the port
  90   addr        the mail address being handled (for setting errors)
  91   port        stick the port in here
  92   msg         for adding to error message
  93
  94 Returns:      TRUE on success, FALSE on failure, with error message set
  95                 in addr, and transport_return set to PANIC
  96 */
  97
  98 BOOL
  99 smtp_get_port(uschar *rstring, address_item *addr, int *port, uschar *msg)
 100 {
 101 uschar *pstring = expand_string(rstring);
 102
 103 if (!pstring)
 104   {
 105   addr->transport_return = PANIC;
 106   addr->message = string_sprintf("failed to expand \"%s\" (\"port\" option) "
 107     "for %s: %s", rstring, msg, expand_string_message);
 108   return FALSE;
 109   }
 110
 111 if (isdigit(*pstring))
 112   {
 113   uschar *end;
 114   *port = Ustrtol(pstring, &end, 0);
 115   if (end != pstring + Ustrlen(pstring))
 116     {
 117     addr->transport_return = PANIC;
 118     addr->message = string_sprintf("invalid port number for %s: %s", msg,
 119       pstring);
 120     return FALSE;
 121     }
 122   }
 123
 124 else
 125   {
 126   struct servent *smtp_service = getservbyname(CS pstring, "tcp");
 127   if (!smtp_service)
 128     {
 129     addr->transport_return = PANIC;
 130     addr->message = string_sprintf("TCP port \"%s\" is not defined for %s",
 131       pstring, msg);
 132     return FALSE;
 133     }
 134   *port = ntohs(smtp_service->s_port);
 135   }
 136
 137 return TRUE;
 138 }
 139
 140
 141
 142
 143 int
 144 smtp_sock_connect(host_item * host, int host_af, int port, uschar * interface,
 145   transport_instance * tb, int timeout)
 146 {
 147 smtp_transport_options_block * ob =
 148   (smtp_transport_options_block *)tb->options_block;
 149 const uschar * dscp = ob->dscp;
 150 int dscp_value;
 151 int dscp_level;
 152 int dscp_option;
 153 int sock;
 154 int save_errno = 0;
 155 BOOL fastopen = FALSE;
 156
 157 #ifndef DISABLE_EVENT
 158 deliver_host_address = host->address;
 159 deliver_host_port = port;
 160 if (event_raise(tb->event_action, US"tcp:connect", NULL)) return -1;
 161 #endif
 162
 163 if ((sock = ip_socket(SOCK_STREAM, host_af)) < 0) return -1;
 164
 165 /* Set TCP_NODELAY; Exim does its own buffering. */
 166
 167 if (setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, US &on, sizeof(on)))
 168   HDEBUG(D_transport|D_acl|D_v)
 169     debug_printf_indent("failed to set NODELAY: %s ", strerror(errno));
 170
 171 /* Set DSCP value, if we can. For now, if we fail to set the value, we don't
 172 bomb out, just log it and continue in default traffic class. */
 173
 174 if (dscp && dscp_lookup(dscp, host_af, &dscp_level, &dscp_option, &dscp_value))
 175   {
 176   HDEBUG(D_transport|D_acl|D_v)
 177     debug_printf_indent("DSCP \"%s\"=%x ", dscp, dscp_value);
 178   if (setsockopt(sock, dscp_level, dscp_option, &dscp_value, sizeof(dscp_value)) < 0)
 179     HDEBUG(D_transport|D_acl|D_v)
 180       debug_printf_indent("failed to set DSCP: %s ", strerror(errno));
 181   /* If the kernel supports IPv4 and IPv6 on an IPv6 socket, we need to set the
 182   option for both; ignore failures here */
 183   if (host_af == AF_INET6 &&
 184       dscp_lookup(dscp, AF_INET, &dscp_level, &dscp_option, &dscp_value))
 185     (void) setsockopt(sock, dscp_level, dscp_option, &dscp_value, sizeof(dscp_value));
 186   }
 187
 188 #ifdef TCP_FASTOPEN
 189 if (verify_check_given_host (&ob->hosts_try_fastopen, host) == OK) fastopen = TRUE;
 190 #endif
 191
 192 /* Bind to a specific interface if requested. Caller must ensure the interface
 193 is the same type (IPv4 or IPv6) as the outgoing address. */
 194
 195 if (interface && ip_bind(sock, host_af, interface, 0) < 0)
 196   {
 197   save_errno = errno;
 198   HDEBUG(D_transport|D_acl|D_v)
 199     debug_printf_indent("unable to bind outgoing SMTP call to %s: %s", interface,
 200     strerror(errno));
 201   }
 202
 203 /* Connect to the remote host, and add keepalive to the socket before returning
 204 it, if requested. */
 205
 206 else if (ip_connect(sock, host_af, host->address, port, timeout, fastopen) < 0)
 207   save_errno = errno;
 208
 209 /* Either bind() or connect() failed */
 210
 211 if (save_errno != 0)
 212   {
 213   HDEBUG(D_transport|D_acl|D_v)
 214     {
 215     debug_printf_indent("failed: %s", CUstrerror(save_errno));
 216     if (save_errno == ETIMEDOUT)
 217       debug_printf(" (timeout=%s)", readconf_printtime(timeout));
 218     debug_printf("\n");
 219     }
 220   (void)close(sock);
 221   errno = save_errno;
 222   return -1;
 223   }
 224
 225 /* Both bind() and connect() succeeded */
 226
 227 else
 228   {
 229   union sockaddr_46 interface_sock;
 230   EXIM_SOCKLEN_T size = sizeof(interface_sock);
 231   HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("connected\n");
 232   if (getsockname(sock, (struct sockaddr *)(&interface_sock), &size) == 0)
 233     sending_ip_address = host_ntoa(-1, &interface_sock, NULL, &sending_port);
 234   else
 235     {
 236     log_write(0, LOG_MAIN | ((errno == ECONNRESET)? 0 : LOG_PANIC),
 237       "getsockname() failed: %s", strerror(errno));
 238     close(sock);
 239     return -1;
 240     }
 241   if (ob->keepalive) ip_keepalive(sock, host->address, TRUE);
 242   return sock;
 243   }
 244 }
 245
 246
 247
 248
 249
 250 void
 251 smtp_port_for_connect(host_item * host, int port)
 252 {
 253 if (host->port != PORT_NONE)
 254   {
 255   HDEBUG(D_transport|D_acl|D_v)
 256     debug_printf_indent("Transport port=%d replaced by host-specific port=%d\n", port,
 257       host->port);
 258   port = host->port;
 259   }
 260 else host->port = port;    /* Set the port actually used */
 261 }
 262
 263
 264 /*************************************************
 265 *           Connect to remote host               *
 266 *************************************************/
 267
 268 /* Create a socket, and connect it to a remote host. IPv6 addresses are
 269 detected by checking for a colon in the address. AF_INET6 is defined even on
 270 non-IPv6 systems, to enable the code to be less messy. However, on such systems
 271 host->address will always be an IPv4 address.
 272
 273 Arguments:
 274   host        host item containing name and address and port
 275   host_af     AF_INET or AF_INET6
 276   interface   outgoing interface address or NULL
 277   timeout     timeout value or 0
 278   tb          transport
 279
 280 Returns:      connected socket number, or -1 with errno set
 281 */
 282
 283 int
 284 smtp_connect(host_item *host, int host_af, uschar *interface,
 285   int timeout, transport_instance * tb)
 286 {
 287 int port = host->port;
 288 #ifdef SUPPORT_SOCKS
 289 smtp_transport_options_block * ob =
 290   (smtp_transport_options_block *)tb->options_block;
 291 #endif
 292
 293 callout_address = string_sprintf("[%s]:%d", host->address, port);
 294
 295 HDEBUG(D_transport|D_acl|D_v)
 296   {
 297   uschar * s = US" ";
 298   if (interface) s = string_sprintf(" from %s ", interface);
 299 #ifdef SUPPORT_SOCKS
 300   if (ob->socks_proxy) s = string_sprintf("%svia proxy ", s);
 301 #endif
 302   debug_printf_indent("Connecting to %s %s%s... ", host->name, callout_address, s);
 303   }
 304
 305 /* Create and connect the socket */
 306
 307 #ifdef SUPPORT_SOCKS
 308 if (ob->socks_proxy)
 309   return socks_sock_connect(host, host_af, port, interface, tb, timeout);
 310 #endif
 311
 312 return smtp_sock_connect(host, host_af, port, interface, tb, timeout);
 313 }
 314
 315
 316 /*************************************************
 317 *        Flush outgoing command buffer           *
 318 *************************************************/
 319
 320 /* This function is called only from smtp_write_command() below. It flushes
 321 the buffer of outgoing commands. There is more than one in the buffer only when
 322 pipelining.
 323
 324 Argument:
 325   outblock   the SMTP output block
 326   mode       further data expected, or plain
 327
 328 Returns:     TRUE if OK, FALSE on error, with errno set
 329 */
 330
 331 static BOOL
 332 flush_buffer(smtp_outblock * outblock, int mode)
 333 {
 334 int rc;
 335 int n = outblock->ptr - outblock->buffer;
 336 BOOL more = mode == SCMD_MORE;
 337
 338 HDEBUG(D_transport|D_acl) debug_printf_indent("cmd buf flush %d bytes%s\n", n,
 339   more ? " (more expected)" : "");
 340
 341 #ifdef SUPPORT_TLS
 342 if (tls_out.active == outblock->sock)
 343   rc = tls_write(FALSE, outblock->buffer, n, more);
 344 else
 345 #endif
 346   rc = send(outblock->sock, outblock->buffer, n,
 347 #ifdef MSG_MORE
 348             more ? MSG_MORE : 0
 349 #else
 350             0
 351 #endif
 352            );
 353
 354 if (rc <= 0)
 355   {
 356   HDEBUG(D_transport|D_acl) debug_printf_indent("send failed: %s\n", strerror(errno));
 357   return FALSE;
 358   }
 359
 360 outblock->ptr = outblock->buffer;
 361 outblock->cmd_count = 0;
 362 return TRUE;
 363 }
 364
 365
 366
 367 /*************************************************
 368 *             Write SMTP command                 *
 369 *************************************************/
 370
 371 /* The formatted command is left in big_buffer so that it can be reflected in
 372 any error message.
 373
 374 Arguments:
 375   outblock   contains buffer for pipelining, and socket
 376   mode       buffer, write-with-more-likely, write
 377   format     a format, starting with one of
 378              of HELO, MAIL FROM, RCPT TO, DATA, ".", or QUIT.
 379              If NULL, flush pipeline buffer only.
 380   ...        data for the format
 381
 382 Returns:     0 if command added to pipelining buffer, with nothing transmitted
 383             +n if n commands transmitted (may still have buffered the new one)
 384             -1 on error, with errno set
 385 */
 386
 387 int
 388 smtp_write_command(smtp_outblock * outblock, int mode, const char *format, ...)
 389 {
 390 int count;
 391 int rc = 0;
 392 va_list ap;
 393
 394 if (format)
 395   {
 396   va_start(ap, format);
 397   if (!string_vformat(big_buffer, big_buffer_size, CS format, ap))
 398     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "overlong write_command in outgoing "
 399       "SMTP");
 400   va_end(ap);
 401   count = Ustrlen(big_buffer);
 402
 403   if (count > outblock->buffersize)
 404     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "overlong write_command in outgoing "
 405       "SMTP");
 406
 407   if (count > outblock->buffersize - (outblock->ptr - outblock->buffer))
 408     {
 409     rc = outblock->cmd_count;                 /* flush resets */
 410     if (!flush_buffer(outblock, SCMD_FLUSH)) return -1;
 411     }
 412
 413   Ustrncpy(CS outblock->ptr, big_buffer, count);
 414   outblock->ptr += count;
 415   outblock->cmd_count++;
 416   count -= 2;
 417   big_buffer[count] = 0;     /* remove \r\n for error message */
 418
 419   /* We want to hide the actual data sent in AUTH transactions from reflections
 420   and logs. While authenticating, a flag is set in the outblock to enable this.
 421   The AUTH command itself gets any data flattened. Other lines are flattened
 422   completely. */
 423
 424   if (outblock->authenticating)
 425     {
 426     uschar *p = big_buffer;
 427     if (Ustrncmp(big_buffer, "AUTH ", 5) == 0)
 428       {
 429       p += 5;
 430       while (isspace(*p)) p++;
 431       while (!isspace(*p)) p++;
 432       while (isspace(*p)) p++;
 433       }
 434     while (*p != 0) *p++ = '*';
 435     }
 436
 437   HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  SMTP>> %s\n", big_buffer);
 438   }
 439
 440 if (mode != SCMD_BUFFER)
 441   {
 442   rc += outblock->cmd_count;                /* flush resets */
 443   if (!flush_buffer(outblock, mode)) return -1;
 444   }
 445
 446 return rc;
 447 }
 448
 449
 450
 451 /*************************************************
 452 *          Read one line of SMTP response        *
 453 *************************************************/
 454
 455 /* This function reads one line of SMTP response from the server host. This may
 456 not be a complete response - it could be just part of a multiline response. We
 457 have to use a buffer for incoming packets, because when pipelining or using
 458 LMTP, there may well be more than one response in a single packet. This
 459 function is called only from the one that follows.
 460
 461 Arguments:
 462   inblock   the SMTP input block (contains holding buffer, socket, etc.)
 463   buffer    where to put the line
 464   size      space available for the line
 465   timeout   the timeout to use when reading a packet
 466
 467 Returns:    length of a line that has been put in the buffer
 468             -1 otherwise, with errno set
 469 */
 470
 471 static int
 472 read_response_line(smtp_inblock *inblock, uschar *buffer, int size, int timeout)
 473 {
 474 uschar *p = buffer;
 475 uschar *ptr = inblock->ptr;
 476 uschar *ptrend = inblock->ptrend;
 477 int sock = inblock->sock;
 478
 479 /* Loop for reading multiple packets or reading another packet after emptying
 480 a previously-read one. */
 481
 482 for (;;)
 483   {
 484   int rc;
 485
 486   /* If there is data in the input buffer left over from last time, copy
 487   characters from it until the end of a line, at which point we can return,
 488   having removed any whitespace (which will include CR) at the end of the line.
 489   The rules for SMTP say that lines end in CRLF, but there are have been cases
 490   of hosts using just LF, and other MTAs are reported to handle this, so we
 491   just look for LF. If we run out of characters before the end of a line,
 492   carry on to read the next incoming packet. */
 493
 494   while (ptr < ptrend)
 495     {
 496     int c = *ptr++;
 497     if (c == '\n')
 498       {
 499       while (p > buffer && isspace(p[-1])) p--;
 500       *p = 0;
 501       inblock->ptr = ptr;
 502       return p - buffer;
 503       }
 504     *p++ = c;
 505     if (--size < 4)
 506       {
 507       *p = 0;                     /* Leave malformed line for error message */
 508       errno = ERRNO_SMTPFORMAT;
 509       return -1;
 510       }
 511     }
 512
 513   /* Need to read a new input packet. */
 514
 515   if((rc = ip_recv(sock, inblock->buffer, inblock->buffersize, timeout)) <= 0)
 516     {
 517     DEBUG(D_deliver|D_transport|D_acl)
 518       debug_printf_indent(errno ? "  SMTP(%s)<<\n" : "  SMTP(closed)<<\n",
 519         strerror(errno));
 520     break;
 521     }
 522
 523   /* Another block of data has been successfully read. Set up the pointers
 524   and let the loop continue. */
 525
 526   ptrend = inblock->ptrend = inblock->buffer + rc;
 527   ptr = inblock->buffer;
 528   DEBUG(D_transport|D_acl) debug_printf_indent("read response data: size=%d\n", rc);
 529   }
 530
 531 /* Get here if there has been some kind of recv() error; errno is set, but we
 532 ensure that the result buffer is empty before returning. */
 533
 534 *buffer = 0;
 535 return -1;
 536 }
 537
 538
 539
 540
 541
 542 /*************************************************
 543 *              Read SMTP response                *
 544 *************************************************/
 545
 546 /* This function reads an SMTP response with a timeout, and returns the
 547 response in the given buffer, as a string. A multiline response will contain
 548 newline characters between the lines. The function also analyzes the first
 549 digit of the reply code and returns FALSE if it is not acceptable. FALSE is
 550 also returned after a reading error. In this case buffer[0] will be zero, and
 551 the error code will be in errno.
 552
 553 Arguments:
 554   inblock   the SMTP input block (contains holding buffer, socket, etc.)
 555   buffer    where to put the response
 556   size      the size of the buffer
 557   okdigit   the expected first digit of the response
 558   timeout   the timeout to use, in seconds
 559
 560 Returns:    TRUE if a valid, non-error response was received; else FALSE
 561 */
 562
 563 BOOL
 564 smtp_read_response(smtp_inblock *inblock, uschar *buffer, int size, int okdigit,
 565    int timeout)
 566 {
 567 uschar *ptr = buffer;
 568 int count;
 569
 570 errno = 0;  /* Ensure errno starts out zero */
 571
 572 /* This is a loop to read and concatenate the lines that make up a multi-line
 573 response. */
 574
 575 for (;;)
 576   {
 577   if ((count = read_response_line(inblock, ptr, size, timeout)) < 0)
 578     return FALSE;
 579
 580   HDEBUG(D_transport|D_acl|D_v)
 581     debug_printf_indent("  %s %s\n", (ptr == buffer)? "SMTP<<" : "      ", ptr);
 582
 583   /* Check the format of the response: it must start with three digits; if
 584   these are followed by a space or end of line, the response is complete. If
 585   they are followed by '-' this is a multi-line response and we must look for
 586   another line until the final line is reached. The only use made of multi-line
 587   responses is to pass them back as error messages. We therefore just
 588   concatenate them all within the buffer, which should be large enough to
 589   accept any reasonable number of lines. */
 590
 591   if (count < 3 ||
 592      !isdigit(ptr[0]) ||
 593      !isdigit(ptr[1]) ||
 594      !isdigit(ptr[2]) ||
 595      (ptr[3] != '-' && ptr[3] != ' ' && ptr[3] != 0))
 596     {
 597     errno = ERRNO_SMTPFORMAT;    /* format error */
 598     return FALSE;
 599     }
 600
 601   /* If the line we have just read is a terminal line, line, we are done.
 602   Otherwise more data has to be read. */
 603
 604   if (ptr[3] != '-') break;
 605
 606   /* Move the reading pointer upwards in the buffer and insert \n between the
 607   components of a multiline response. Space is left for this by read_response_
 608   line(). */
 609
 610   ptr += count;
 611   *ptr++ = '\n';
 612   size -= count + 1;
 613   }
 614
 615 /* Return a value that depends on the SMTP return code. On some systems a
 616 non-zero value of errno has been seen at this point, so ensure it is zero,
 617 because the caller of this function looks at errno when FALSE is returned, to
 618 distinguish between an unexpected return code and other errors such as
 619 timeouts, lost connections, etc. */
 620
 621 errno = 0;
 622 return buffer[0] == okdigit;
 623 }
 624
 625 /* End of smtp_out.c */
 626 /* vi: aw ai sw=2
 627 */