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       more-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
 337 HDEBUG(D_transport|D_acl) debug_printf_indent("cmd buf flush %d bytes%s\n", n,
 338   mode == SCMD_MORE ? " (more expected)" : "");
 339
 340 #ifdef SUPPORT_TLS
 341 if (tls_out.active == outblock->sock)
 342   rc = tls_write(FALSE, outblock->buffer, n);
 343 else
 344 #endif
 345   rc = send(outblock->sock, outblock->buffer, n,
 346 #ifdef MSG_MORE
 347             mode == SCMD_MORE ? MSG_MORE : 0
 348 #else
 349             0
 350 #endif
 351            );
 352
 353 if (rc <= 0)
 354   {
 355   HDEBUG(D_transport|D_acl) debug_printf_indent("send failed: %s\n", strerror(errno));
 356   return FALSE;
 357   }
 358
 359 outblock->ptr = outblock->buffer;
 360 outblock->cmd_count = 0;
 361 return TRUE;
 362 }
 363
 364
 365
 366 /*************************************************
 367 *             Write SMTP command                 *
 368 *************************************************/
 369
 370 /* The formatted command is left in big_buffer so that it can be reflected in
 371 any error message.
 372
 373 Arguments:
 374   outblock   contains buffer for pipelining, and socket
 375   mode       buffer, write-with-more-likely, write
 376   format     a format, starting with one of
 377              of HELO, MAIL FROM, RCPT TO, DATA, ".", or QUIT.
 378              If NULL, flush pipeline buffer only.
 379   ...        data for the format
 380
 381 Returns:     0 if command added to pipelining buffer, with nothing transmitted
 382             +n if n commands transmitted (may still have buffered the new one)
 383             -1 on error, with errno set
 384 */
 385
 386 int
 387 smtp_write_command(smtp_outblock * outblock, int mode, const char *format, ...)
 388 {
 389 int count;
 390 int rc = 0;
 391 va_list ap;
 392
 393 if (format)
 394   {
 395   va_start(ap, format);
 396   if (!string_vformat(big_buffer, big_buffer_size, CS format, ap))
 397     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "overlong write_command in outgoing "
 398       "SMTP");
 399   va_end(ap);
 400   count = Ustrlen(big_buffer);
 401
 402   if (count > outblock->buffersize)
 403     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "overlong write_command in outgoing "
 404       "SMTP");
 405
 406   if (count > outblock->buffersize - (outblock->ptr - outblock->buffer))
 407     {
 408     rc = outblock->cmd_count;                 /* flush resets */
 409     if (!flush_buffer(outblock, SCMD_FLUSH)) return -1;
 410     }
 411
 412   Ustrncpy(CS outblock->ptr, big_buffer, count);
 413   outblock->ptr += count;
 414   outblock->cmd_count++;
 415   count -= 2;
 416   big_buffer[count] = 0;     /* remove \r\n for error message */
 417
 418   /* We want to hide the actual data sent in AUTH transactions from reflections
 419   and logs. While authenticating, a flag is set in the outblock to enable this.
 420   The AUTH command itself gets any data flattened. Other lines are flattened
 421   completely. */
 422
 423   if (outblock->authenticating)
 424     {
 425     uschar *p = big_buffer;
 426     if (Ustrncmp(big_buffer, "AUTH ", 5) == 0)
 427       {
 428       p += 5;
 429       while (isspace(*p)) p++;
 430       while (!isspace(*p)) p++;
 431       while (isspace(*p)) p++;
 432       }
 433     while (*p != 0) *p++ = '*';
 434     }
 435
 436   HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  SMTP>> %s\n", big_buffer);
 437   }
 438
 439 if (mode != SCMD_BUFFER)
 440   {
 441   rc += outblock->cmd_count;                /* flush resets */
 442   if (!flush_buffer(outblock, mode)) return -1;
 443   }
 444
 445 return rc;
 446 }
 447
 448
 449
 450 /*************************************************
 451 *          Read one line of SMTP response        *
 452 *************************************************/
 453
 454 /* This function reads one line of SMTP response from the server host. This may
 455 not be a complete response - it could be just part of a multiline response. We
 456 have to use a buffer for incoming packets, because when pipelining or using
 457 LMTP, there may well be more than one response in a single packet. This
 458 function is called only from the one that follows.
 459
 460 Arguments:
 461   inblock   the SMTP input block (contains holding buffer, socket, etc.)
 462   buffer    where to put the line
 463   size      space available for the line
 464   timeout   the timeout to use when reading a packet
 465
 466 Returns:    length of a line that has been put in the buffer
 467             -1 otherwise, with errno set
 468 */
 469
 470 static int
 471 read_response_line(smtp_inblock *inblock, uschar *buffer, int size, int timeout)
 472 {
 473 uschar *p = buffer;
 474 uschar *ptr = inblock->ptr;
 475 uschar *ptrend = inblock->ptrend;
 476 int sock = inblock->sock;
 477
 478 /* Loop for reading multiple packets or reading another packet after emptying
 479 a previously-read one. */
 480
 481 for (;;)
 482   {
 483   int rc;
 484
 485   /* If there is data in the input buffer left over from last time, copy
 486   characters from it until the end of a line, at which point we can return,
 487   having removed any whitespace (which will include CR) at the end of the line.
 488   The rules for SMTP say that lines end in CRLF, but there are have been cases
 489   of hosts using just LF, and other MTAs are reported to handle this, so we
 490   just look for LF. If we run out of characters before the end of a line,
 491   carry on to read the next incoming packet. */
 492
 493   while (ptr < ptrend)
 494     {
 495     int c = *ptr++;
 496     if (c == '\n')
 497       {
 498       while (p > buffer && isspace(p[-1])) p--;
 499       *p = 0;
 500       inblock->ptr = ptr;
 501       return p - buffer;
 502       }
 503     *p++ = c;
 504     if (--size < 4)
 505       {
 506       *p = 0;                     /* Leave malformed line for error message */
 507       errno = ERRNO_SMTPFORMAT;
 508       return -1;
 509       }
 510     }
 511
 512   /* Need to read a new input packet. */
 513
 514   if((rc = ip_recv(sock, inblock->buffer, inblock->buffersize, timeout)) <= 0)
 515     {
 516     DEBUG(D_deliver|D_transport|D_acl)
 517       debug_printf_indent(errno ? "  SMTP(%s)<<\n" : "  SMTP(closed)<<\n",
 518         strerror(errno));
 519     break;
 520     }
 521
 522   /* Another block of data has been successfully read. Set up the pointers
 523   and let the loop continue. */
 524
 525   ptrend = inblock->ptrend = inblock->buffer + rc;
 526   ptr = inblock->buffer;
 527   DEBUG(D_transport|D_acl) debug_printf_indent("read response data: size=%d\n", rc);
 528   }
 529
 530 /* Get here if there has been some kind of recv() error; errno is set, but we
 531 ensure that the result buffer is empty before returning. */
 532
 533 *buffer = 0;
 534 return -1;
 535 }
 536
 537
 538
 539
 540
 541 /*************************************************
 542 *              Read SMTP response                *
 543 *************************************************/
 544
 545 /* This function reads an SMTP response with a timeout, and returns the
 546 response in the given buffer, as a string. A multiline response will contain
 547 newline characters between the lines. The function also analyzes the first
 548 digit of the reply code and returns FALSE if it is not acceptable. FALSE is
 549 also returned after a reading error. In this case buffer[0] will be zero, and
 550 the error code will be in errno.
 551
 552 Arguments:
 553   inblock   the SMTP input block (contains holding buffer, socket, etc.)
 554   buffer    where to put the response
 555   size      the size of the buffer
 556   okdigit   the expected first digit of the response
 557   timeout   the timeout to use, in seconds
 558
 559 Returns:    TRUE if a valid, non-error response was received; else FALSE
 560 */
 561
 562 BOOL
 563 smtp_read_response(smtp_inblock *inblock, uschar *buffer, int size, int okdigit,
 564    int timeout)
 565 {
 566 uschar *ptr = buffer;
 567 int count;
 568
 569 errno = 0;  /* Ensure errno starts out zero */
 570
 571 /* This is a loop to read and concatenate the lines that make up a multi-line
 572 response. */
 573
 574 for (;;)
 575   {
 576   if ((count = read_response_line(inblock, ptr, size, timeout)) < 0)
 577     return FALSE;
 578
 579   HDEBUG(D_transport|D_acl|D_v)
 580     debug_printf_indent("  %s %s\n", (ptr == buffer)? "SMTP<<" : "      ", ptr);
 581
 582   /* Check the format of the response: it must start with three digits; if
 583   these are followed by a space or end of line, the response is complete. If
 584   they are followed by '-' this is a multi-line response and we must look for
 585   another line until the final line is reached. The only use made of multi-line
 586   responses is to pass them back as error messages. We therefore just
 587   concatenate them all within the buffer, which should be large enough to
 588   accept any reasonable number of lines. */
 589
 590   if (count < 3 ||
 591      !isdigit(ptr[0]) ||
 592      !isdigit(ptr[1]) ||
 593      !isdigit(ptr[2]) ||
 594      (ptr[3] != '-' && ptr[3] != ' ' && ptr[3] != 0))
 595     {
 596     errno = ERRNO_SMTPFORMAT;    /* format error */
 597     return FALSE;
 598     }
 599
 600   /* If the line we have just read is a terminal line, line, we are done.
 601   Otherwise more data has to be read. */
 602
 603   if (ptr[3] != '-') break;
 604
 605   /* Move the reading pointer upwards in the buffer and insert \n between the
 606   components of a multiline response. Space is left for this by read_response_
 607   line(). */
 608
 609   ptr += count;
 610   *ptr++ = '\n';
 611   size -= count + 1;
 612   }
 613
 614 /* Return a value that depends on the SMTP return code. On some systems a
 615 non-zero value of errno has been seen at this point, so ensure it is zero,
 616 because the caller of this function looks at errno when FALSE is returned, to
 617 distinguish between an unexpected return code and other errors such as
 618 timeouts, lost connections, etc. */
 619
 620 errno = 0;
 621 return buffer[0] == okdigit;
 622 }
 623
 624 /* End of smtp_out.c */
 625 /* vi: aw ai sw=2
 626 */