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

/* Copyright (c) Tom Kistner <tom@duncanthrax.net> 2003-2015 */
/* License: GPL */

/* Code for matching regular expressions against headers and body.
 Called from acl.c. */

#include "exim.h"
#ifdef WITH_CONTENT_SCAN
#include <unistd.h>
#include <sys/mman.h>

/* Structure to hold a list of Regular expressions */
typedef struct pcre_list {
  pcre *re;
  uschar *pcre_text;
  struct pcre_list *next;
} pcre_list;

uschar regex_match_string_buffer[1024];

extern FILE *mime_stream;
extern uschar *mime_current_boundary;

static pcre_list *
compile(const uschar * list)
{
  int sep = 0;
  uschar *regex_string;
  uschar regex_string_buffer[1024];
  const char *pcre_error;
  int pcre_erroffset;
  pcre_list *re_list_head = NULL;
  pcre_list *ri;

  /* precompile our regexes */
  while ((regex_string = string_nextinlist(&list, &sep,
                                           regex_string_buffer,
                                           sizeof(regex_string_buffer))) != NULL) {
    pcre *re;

    /* parse option */
    if ( (strcmpic(regex_string,US"false") == 0) ||
         (Ustrcmp(regex_string,"0") == 0) )
      continue;				/* explicitly no matching */

    /* compile our regular expression */
    if (!(re = pcre_compile( CS regex_string,
                       0, &pcre_error, &pcre_erroffset, NULL ))) {
      log_write(0, LOG_MAIN,
           "regex acl condition warning - error in regex '%s': %s at offset %d, skipped.",
	   regex_string, pcre_error, pcre_erroffset);
      continue;
    }

    ri = store_get(sizeof(pcre_list));
    ri->re = re;
    ri->pcre_text = string_copy(regex_string);
    ri->next = re_list_head;
    re_list_head = ri;
  }
  return re_list_head;
}

static int
matcher(pcre_list * re_list_head, uschar * linebuffer, int len)
{
  pcre_list * ri;

  for(ri = re_list_head; ri; ri = ri->next)
    {
    int ovec[3*(REGEX_VARS+1)];
    int n, nn;

    /* try matcher on the line */
    n = pcre_exec(ri->re, NULL,
	 CS linebuffer, len, 0, 0,
	 ovec, nelem(ovec));
    if (n > 0)
      {
      Ustrncpy(regex_match_string_buffer, ri->pcre_text, 1023);
      regex_match_string = regex_match_string_buffer;

      for (nn = 1; nn < n; nn++)
	regex_vars[nn-1] =
	  string_copyn(linebuffer + ovec[nn*2], ovec[nn*2+1] - ovec[nn*2]);

      return OK;
      }
    }
  return FAIL;
}

int
regex(const uschar **listptr)
{
  unsigned long mbox_size;
  FILE *mbox_file;
  pcre_list *re_list_head;
  uschar *linebuffer;
  long f_pos = 0;
  int ret = FAIL;

  /* reset expansion variable */
  regex_match_string = NULL;

  if (mime_stream == NULL) {			/* We are in the DATA ACL */
    mbox_file = spool_mbox(&mbox_size, NULL);
    if (mbox_file == NULL) {			/* error while spooling */
      log_write(0, LOG_MAIN|LOG_PANIC,
             "regex acl condition: error while creating mbox spool file");
      return DEFER;
    }
  }
  else {
    f_pos = ftell(mime_stream);
    mbox_file = mime_stream;
  }

  /* precompile our regexes */
  if (!(re_list_head = compile(*listptr)))
    return FAIL;			/* no regexes -> nothing to do */

  /* match each line against all regexes */
  linebuffer = store_get(32767);
  while (fgets(CS linebuffer, 32767, mbox_file) != NULL) {

    if (  mime_stream && mime_current_boundary		/* check boundary */
       && Ustrncmp(linebuffer,"--",2) == 0
       && Ustrncmp((linebuffer+2),mime_current_boundary,Ustrlen(mime_current_boundary)) == 0)
	break;						/* found boundary */

    if ((ret = matcher(re_list_head, linebuffer, (int)Ustrlen(linebuffer))) == OK)
      goto done;
  }
  /* no matches ... */

done:
  if (mime_stream == NULL)
    (void)fclose(mbox_file);
  else {
    clearerr(mime_stream);
    fseek(mime_stream,f_pos,SEEK_SET);
  };

  return ret;
}


int
mime_regex(const uschar **listptr)
{
  pcre_list *re_list_head = NULL;
  FILE *f;
  uschar *mime_subject = NULL;
  int mime_subject_len = 0;
  int ret;

  /* reset expansion variable */
  regex_match_string = NULL;

  /* precompile our regexes */
  if (!(re_list_head = compile(*listptr)))
    return FAIL;			/* no regexes -> nothing to do */

  /* check if the file is already decoded */
  if (mime_decoded_filename == NULL) {
    const uschar *empty = US"";
    /* no, decode it first */
    mime_decode(&empty);
    if (mime_decoded_filename == NULL) {
      /* decoding failed */
      log_write(0, LOG_MAIN,
           "mime_regex acl condition warning - could not decode MIME part to file.");
      return DEFER;
    }
  }

  /* open file */
  if (!(f = fopen(CS mime_decoded_filename, "rb"))) {
    log_write(0, LOG_MAIN,
         "mime_regex acl condition warning - can't open '%s' for reading.",
	 mime_decoded_filename);
    return DEFER;
  }

  /* get 32k memory */
  mime_subject = (uschar *)store_get(32767);

  mime_subject_len = fread(mime_subject, 1, 32766, f);

  ret = matcher(re_list_head, mime_subject, mime_subject_len);
  (void)fclose(f);
  return ret;
}

#endif /* WITH_CONTENT_SCAN */