path: root/src/dcc.c

/*************************************************
*     Exim - an Internet mail transport agent    *
*************************************************/

/* Copyright (c) Wolfgang Breyha 2005 - 2019
 * Vienna University Computer Center
 * wbreyha@gmx.net
 * See the file NOTICE for conditions of use and distribution.
 *
 * Copyright (c) The Exim Maintainers 2015 - 2021
 */

/* Code for calling dccifd. Called from acl.c. */

#include "exim.h"
#ifdef EXPERIMENTAL_DCC
#include "dcc.h"
#include "unistd.h"

#define DCC_HEADER_LIMIT 120

int dcc_ok = 0;
int dcc_rc = 0;

/* This function takes a file descriptor and a buffer as input and
returns either 0 for success or errno in case of error. */

static int flushbuffer
(int socket, gstring *buffer)
{
int rsp;

rsp = write(socket, buffer->s, buffer->ptr);
DEBUG(D_acl)
  debug_printf("DCC: flushbuffer(): Result of the write() = %d\n", rsp);
if(rsp < 0)
  {
  DEBUG(D_acl)
    debug_printf("DCC: flushbuffer(): Error writing buffer to socket: %s\n", strerror(errno));
  return errno;
  }
DEBUG(D_acl)
  debug_printf("DCC: flushbuffer(): Wrote buffer to socket:\n%.*s\n", buffer->ptr, buffer->s);
return 0;
}

int
dcc_process(uschar **listptr)
{
int sep = 0;
const uschar *list = *listptr;
FILE *data_file;
uschar *dcc_default_ip_option = US"127.0.0.1";
uschar *dcc_helo_option = US"localhost";
uschar *xtra_hdrs = NULL;
uschar *override_client_ip  = NULL;

/* from local_scan */
int dcc_resplen, retval, sockfd, resp;
unsigned int portnr;
struct sockaddr_un  serv_addr;
struct sockaddr_in  serv_addr_in;
struct hostent *ipaddress;
uschar sockpath[128];
uschar sockip[40], client_ip[40];
gstring *dcc_headers;
gstring *sendbuf;
uschar *dcc_return_text = US"''";
struct header_line *mail_headers;
uschar *dcc_acl_options;
gstring *dcc_xtra_hdrs;
gstring *dcc_header_str;

/* grep 1st option */
if ((dcc_acl_options = string_nextinlist(&list, &sep, NULL, 0)))
  {
  /* parse 1st option */
  if (  strcmpic(dcc_acl_options, US"false") == 0
     || Ustrcmp(dcc_acl_options, "0") == 0)
    return FAIL;	/* explicitly no matching */
  }
else
  return FAIL;	/* empty means "don't match anything" */

sep = 0;

/* if we scanned this message last time, just return */
if (dcc_ok)
  return dcc_rc;

/* open the spooled body */
for (int i = 0; i < 2; i++)
  {
  uschar message_subdir[2];
  set_subdir_str(message_subdir, message_id, i);
  if ((data_file = Ufopen(
	  spool_fname(US"input", message_subdir, message_id, US"-D"), "rb")))
    break;
  }

if (!data_file)
  {
  /* error while spooling */
  log_write(0, LOG_MAIN|LOG_PANIC,
	 "DCC: error while opening spool file");
  return DEFER;
  }

/* Initialize the variables */

bzero(sockip,sizeof(sockip));
if (dccifd_address)
  {
  if (dccifd_address[0] == '/')
    Ustrncpy(sockpath, dccifd_address, sizeof(sockpath));
  else
    if( sscanf(CS dccifd_address, "%s %u", sockip, &portnr) != 2)
      {
      log_write(0, LOG_MAIN,
	"DCC: warning - invalid dccifd address: '%s'", dccifd_address);
      (void)fclose(data_file);
      return DEFER;
      }
  }

/* dcc_headers is what we send as dccifd options - see man dccifd */
/* We don't support any other option than 'header' so just copy that */
dcc_headers = string_cat(NULL, dccifd_options);
/* if $acl_m_dcc_override_client_ip is set use it */
if (((override_client_ip = expand_string(US"$acl_m_dcc_override_client_ip")) != NULL) &&
     (override_client_ip[0] != '\0'))
  {
  Ustrncpy(client_ip, override_client_ip, sizeof(client_ip)-1);
  DEBUG(D_acl)
    debug_printf("DCC: Client IP (overridden): %s\n", client_ip);
  }
else if(sender_host_address)
  {
  /* else if $sender_host_address is available use that? */
  Ustrncpy(client_ip, sender_host_address, sizeof(client_ip)-1);
  DEBUG(D_acl)
    debug_printf("DCC: Client IP (sender_host_address): %s\n", client_ip);
  }
else
  {
  /* sender_host_address is NULL which means it comes from localhost */
  Ustrncpy(client_ip, dcc_default_ip_option, sizeof(client_ip)-1);
  DEBUG(D_acl)
    debug_printf("DCC: Client IP (default): %s\n", client_ip);
  }
/* build options block */
dcc_headers = string_append(dcc_headers, 5, US"\n", client_ip, US"\nHELO ", dcc_helo_option, US"\n");

/* initialize the other variables */
mail_headers = header_list;
/* we set the default return value to DEFER */
retval = DEFER;

/* send a null return path as "<>". */
dcc_headers = string_cat (dcc_headers, *sender_address ? sender_address : US"<>");
dcc_headers = string_catn(dcc_headers, US"\n", 1);

/**************************************
 * Now creating the socket connection *
 **************************************/

/* If sockip contains an ip, we use a tcp socket, otherwise a UNIX socket */
if(Ustrcmp(sockip, ""))
  {
  ipaddress = gethostbyname(CS sockip);
  bzero(CS  &serv_addr_in, sizeof(serv_addr_in));
  serv_addr_in.sin_family = AF_INET;
  bcopy(CS ipaddress->h_addr, CS &serv_addr_in.sin_addr.s_addr, ipaddress->h_length);
  serv_addr_in.sin_port = htons(portnr);
  if ((sockfd = socket(AF_INET, SOCK_STREAM,0)) < 0)
    {
    DEBUG(D_acl)
      debug_printf("DCC: Creating TCP socket connection failed: %s\n", strerror(errno));
    log_write(0,LOG_PANIC,"DCC: Creating TCP socket connection failed: %s\n", strerror(errno));
    /* if we cannot create the socket, defer the mail */
    (void)fclose(data_file);
    return retval;
    }
  /* Now connecting the socket (INET) */
  if (connect(sockfd, (struct sockaddr *)&serv_addr_in, sizeof(serv_addr_in)) < 0)
    {
    DEBUG(D_acl)
      debug_printf("DCC: Connecting to TCP socket failed: %s\n", strerror(errno));
    log_write(0,LOG_PANIC,"DCC: Connecting to TCP socket failed: %s\n", strerror(errno));
    /* if we cannot contact the socket, defer the mail */
    (void)fclose(data_file);
    return retval;
    }
  }
else
  {
  /* connecting to the dccifd UNIX socket */
  bzero(&serv_addr, sizeof(serv_addr));
  serv_addr.sun_family = AF_UNIX;
  Ustrncpy(US serv_addr.sun_path, sockpath, sizeof(serv_addr.sun_path));
  if ((sockfd = socket(AF_UNIX, SOCK_STREAM,0)) < 0)
    {
    DEBUG(D_acl)
      debug_printf("DCC: Creating UNIX socket connection failed: %s\n", strerror(errno));
    log_write(0,LOG_PANIC,"DCC: Creating UNIX socket connection failed: %s\n", strerror(errno));
    /* if we cannot create the socket, defer the mail */
    (void)fclose(data_file);
    return retval;
    }
  /* Now connecting the socket (UNIX) */
  if (connect(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
    {
    DEBUG(D_acl)
      debug_printf("DCC: Connecting to UNIX socket failed: %s\n", strerror(errno));
    log_write(0,LOG_PANIC,"DCC: Connecting to UNIX socket failed: %s\n", strerror(errno));
    /* if we cannot contact the socket, defer the mail */
    (void)fclose(data_file);
    return retval;
    }
  }
/* the socket is open, now send the options to dccifd*/
DEBUG(D_acl)
  debug_printf("DCC: -----------------------------------\nDCC: Socket opened; now sending input\n"
	       "DCC: -----------------------------------\n");

/* let's send each of the recipients to dccifd */
for (int i = 0; i < recipients_count; i++)
  {
  DEBUG(D_acl)
    debug_printf("DCC: recipient = %s\n",recipients_list[i].address);
  dcc_headers = string_append(dcc_headers, 2, recipients_list[i].address, "\n");
  }
/* send a blank line between options and message */
dcc_headers = string_catn(dcc_headers, US"\n", 1);
/* Now we send the input buffer */
(void) string_from_gstring(dcc_headers);
DEBUG(D_acl)
  debug_printf("DCC: ***********************************\nDCC: Sending options:\n%s"
	       "DCC: ***********************************\n", dcc_headers->s);
if (flushbuffer(sockfd, dcc_headers) != 0)
  {
  (void)fclose(data_file);
  return retval;
  }

/* now send the message */
/* First send the headers */
DEBUG(D_acl)
  debug_printf("DCC: ***********************************\nDCC: Sending headers:\n");
sendbuf = string_get(8192);
sendbuf = string_catn(sendbuf, mail_headers->text, mail_headers->slen);
while((mail_headers=mail_headers->next))
  sendbuf = string_catn(sendbuf, mail_headers->text, mail_headers->slen);

/* a blank line separates header from body */
sendbuf = string_catn(sendbuf, US"\r\n", 2);
(void) string_from_gstring(sendbuf);
gstring_release_unused(sendbuf);
DEBUG(D_acl)
  debug_printf("%sDCC: ***********************************\n", sendbuf->s);
if (flushbuffer(sockfd, sendbuf) != 0)
  {
  (void)fclose(data_file);
  return retval;
  }

/* now send the body */
DEBUG(D_acl)
  debug_printf("DCC: ***********************************\nDCC: Writing body:\n");
(void)fseek(data_file, SPOOL_DATA_START_OFFSET, SEEK_SET);

gstring filebuf = { .size = big_buffer_size, .ptr = 0, .s = big_buffer };

while((filebuf.ptr = fread(filebuf.s, 1, filebuf.size, data_file)) > 0)
  if (flushbuffer(sockfd, &filebuf) != 0)
    {
    (void)fclose(data_file);
    return retval;
    }
DEBUG(D_acl)
  debug_printf("DCC: ***********************************\n");

/* shutdown() the socket */
if(shutdown(sockfd, SHUT_WR) < 0)
  {
  DEBUG(D_acl)
    debug_printf("DCC: Couldn't shutdown socket: %s\n", strerror(errno));
  log_write(0,LOG_MAIN,"DCC: Couldn't shutdown socket: %s\n", strerror(errno));
  /* If there is a problem with the shutdown()
   * defer the mail. */
  (void)fclose(data_file);
  return retval;
  }
DEBUG(D_acl)
  debug_printf("DCC: Input sent.\n"
	       "DCC: +++++++++++++++++++++++++++++++++++\n"
	       "DCC: Now receiving output from server\n"
	       "DCC: -----------------------------------\n");

/********************************
 * receiving output from dccifd *
 ********************************/

/******************************************************************
 * We should get 3 lines:                                         *
 * 1/ First line is overall result: either 'A' for Accept,        *
 *    'R' for Reject, 'S' for accept Some recipients or           *
 *    'T' for a Temporary error.                                  *
 * 2/ Second line contains the list of Accepted/Rejected          *
 *    recipients in the form AARRA (A = accepted, R = rejected).  *
 * 3/ Third line contains the X-DCC header.                       *
 ******************************************************************/

int line = 1;    /* we start at the first line of the output */
int bufoffset;

dcc_header_str = string_get(DCC_HEADER_LIMIT + 2);
/* Let's read from the socket until there's nothing left to read */
while((dcc_resplen = read(sockfd, big_buffer, big_buffer_size-1)) > 0)
  {
  /* fail on read error */
  if(dcc_resplen < 0)
    {
    DEBUG(D_acl)
      debug_printf("DCC: Error reading from socket: %s\n", strerror(errno));
    (void)fclose(data_file);
    return retval;
    }
  /* make the answer 0-terminated. only needed for debug_printf */
  DEBUG(D_acl)
    debug_printf("DCC: Length of the output buffer is: %d\nDCC: Output buffer is:\n"
		 "DCC: -----------------------------------\n%.*s\n"
		 "DCC: -----------------------------------\n", dcc_resplen, dcc_resplen, big_buffer);

  /* Now let's read each character and see what we've got */
  for(bufoffset = 0; bufoffset < dcc_resplen && line <= 2; bufoffset++)
    {
    /* First check if we reached the end of the line and
    then increment the line counter */
    if(big_buffer[bufoffset] == '\n')
      line++;
    else
      {
      /* The first character of the first line is the overall response. If
      there's another character on that line it is not correct. */
      if(line == 1)
	{
	if(bufoffset == 0)
	  {
	  /* Now get the value and set the return value accordingly */
	  switch (big_buffer[bufoffset])
	    {
	    case 'A':
	      DEBUG(D_acl)
		debug_printf("DCC: Overall result = A\treturning OK\n");
	      dcc_return_text = US"Mail accepted by DCC";
	      dcc_result = US"A";
	      retval = OK;
	      break;
	    case 'R':
	      DEBUG(D_acl)
		debug_printf("DCC: Overall result = R\treturning FAIL\n");
	      dcc_return_text = US"Rejected by DCC";
	      dcc_result = US"R";
	      retval = FAIL;
	      if(sender_host_name)
		log_write(0, LOG_MAIN, "H=%s [%s] F=<%s>: rejected by DCC",
			   sender_host_name, sender_host_address, sender_address);
	      else
		log_write(0, LOG_MAIN, "H=[%s] F=<%s>: rejected by DCC",
			   sender_host_address, sender_address);
	      break;
	    case 'S':
	      DEBUG(D_acl)
		debug_printf("DCC: Overall result  = S\treturning OK\n");
	      dcc_return_text = US"Not all recipients accepted by DCC";
	      /* Since we're in an ACL we want a global result so we accept for all */
	      dcc_result = US"A";
	      retval = OK;
	      break;
	    case 'G':
	      DEBUG(D_acl)
		debug_printf("DCC: Overall result  = G\treturning FAIL\n");
	      dcc_return_text = US"Greylisted by DCC";
	      dcc_result = US"G";
	      retval = FAIL;
	      break;
	    case 'T':
	      DEBUG(D_acl)
		debug_printf("DCC: Overall result = T\treturning DEFER\n");
	      dcc_return_text = US"Temporary error with DCC";
	      dcc_result = US"T";
	      retval = DEFER;
	      log_write(0,LOG_MAIN,"Temporary error with DCC: %s\n", big_buffer);
	      break;
	    default:
	      DEBUG(D_acl)
		debug_printf("DCC: Overall result = something else\treturning DEFER\n");
	      dcc_return_text = US"Unknown DCC response";
	      dcc_result = US"T";
	      retval = DEFER;
	      log_write(0,LOG_MAIN,"Unknown DCC response: %s\n", big_buffer);
	      break;
	    }
	}
	else
	  {
	  /* We're on the first line but not on the first character,
	   * there must be something wrong. */
	  DEBUG(D_acl) debug_printf("DCC: Line = %d but bufoffset = %d != 0"
	      "  character is %c - This is wrong!\n", line, bufoffset, big_buffer[bufoffset]);
	  log_write(0,LOG_MAIN,"Wrong header from DCC, output is %s\n", big_buffer);
	  }
	}
      else if(line == 2)
	{
	/* On the second line we get a list of answers for each recipient. We
	don't care about it because we're in an acl and take the global result. */
	}
      }
    }
  if(line > 2)
    {
    /* The third and following lines are the X-DCC header, so we store it in
    dcc_header_str up to our limit. */
    /* check if buffer contains the end of the header .."\n\n" and truncate it */
    if ((big_buffer[dcc_resplen-1] == '\n') &&
	(big_buffer[dcc_resplen-2] == '\n'))
      dcc_resplen -= 2;
    dcc_resplen -= bufoffset;
    if (dcc_header_str->ptr + dcc_resplen > DCC_HEADER_LIMIT)
      {
      dcc_resplen = DCC_HEADER_LIMIT - dcc_header_str->ptr;
      DEBUG(D_acl) debug_printf("DCC: We got more output than we can store"
			 "in the X-DCC header. Truncating at 120 characters.\n");
      }
    dcc_header_str = string_catn(dcc_header_str, &big_buffer[bufoffset], dcc_resplen);
    }
  }
/* We have read everything from the socket. make sure the header ends with "\n" */
dcc_header_str = string_catn(dcc_header_str, US"\n", 1);

(void) string_from_gstring(dcc_header_str);
/* Now let's sum up what we've got. */
DEBUG(D_acl)
  debug_printf("\nDCC: --------------------------\nDCC: Overall result = %d\n"
	       "DCC: X-DCC header: %sReturn message: %s\nDCC: dcc_result: %s\n",
		 retval, dcc_header_str->s, dcc_return_text, dcc_result);

/* We only add the X-DCC header if it starts with X-DCC */
if(!(Ustrncmp(dcc_header_str->s, "X-DCC", 5)))
  {
  dcc_header = dcc_header_str->s;
  if(dcc_direct_add_header)
    {
    header_add(' ' , "%s", dcc_header_str->s);
/* since the MIME ACL already writes the .eml file to disk without DCC Header we've to erase it */
    unspool_mbox();
    }
  }
else
  DEBUG(D_acl)
    debug_printf("DCC: Wrong format of the X-DCC header: %.*s\n", dcc_header_str->ptr, dcc_header_str->s);

/* check if we should add additional headers passed in acl_m_dcc_add_header */
if (dcc_direct_add_header)
  {
  if (((xtra_hdrs = expand_string(US"$acl_m_dcc_add_header")) != NULL) && (xtra_hdrs[0] != '\0'))
    {
    dcc_xtra_hdrs = string_cat(NULL, xtra_hdrs);
    if (dcc_xtra_hdrs->s[dcc_xtra_hdrs->ptr - 1] != '\n')
      dcc_xtra_hdrs = string_catn(dcc_xtra_hdrs, US"\n", 1);
    header_add(' ', "%s", string_from_gstring(dcc_xtra_hdrs));
    DEBUG(D_acl)
      debug_printf("DCC: adding additional headers in $acl_m_dcc_add_header: %.*s", dcc_xtra_hdrs->ptr, dcc_xtra_hdrs->s);
    }
  }

dcc_ok = 1;
/* Now return to exim main process */
DEBUG(D_acl)
  debug_printf("DCC: Before returning to exim main process:\nDCC: return_text = %s - retval = %d\n"
	       "DCC: dcc_result = %s\n", dcc_return_text, retval, dcc_result);

(void)fclose(data_file);
dcc_rc = retval;
return dcc_rc;
}

#endif