src/regex.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) Tom Kistner <tom@duncanthrax.net> 2003-2015
   6  * License: GPL
   7  * Copyright (c) The Exim Maintainers 2016 - 2018
   8  */
   9
  10 /* Code for matching regular expressions against headers and body.
  11  Called from acl.c. */
  12
  13 #include "exim.h"
  14 #ifdef WITH_CONTENT_SCAN
  15 #include <unistd.h>
  16 #include <sys/mman.h>
  17
  18 /* Structure to hold a list of Regular expressions */
  19 typedef struct pcre_list {
  20   pcre *re;
  21   uschar *pcre_text;
  22   struct pcre_list *next;
  23 } pcre_list;
  24
  25 uschar regex_match_string_buffer[1024];
  26
  27 extern FILE *mime_stream;
  28 extern uschar *mime_current_boundary;
  29
  30 static pcre_list *
  31 compile(const uschar * list)
  32 {
  33 int sep = 0;
  34 uschar *regex_string;
  35 const char *pcre_error;
  36 int pcre_erroffset;
  37 pcre_list *re_list_head = NULL;
  38 pcre_list *ri;
  39
  40 /* precompile our regexes */
  41 while ((regex_string = string_nextinlist(&list, &sep, NULL, 0)))
  42   if (strcmpic(regex_string, US"false") != 0 && Ustrcmp(regex_string, "0") != 0)
  43     {
  44     pcre *re;
  45
  46     /* compile our regular expression */
  47     if (!(re = pcre_compile( CS regex_string,
  48                        0, &pcre_error, &pcre_erroffset, NULL )))
  49       {
  50       log_write(0, LOG_MAIN,
  51            "regex acl condition warning - error in regex '%s': %s at offset %d, skipped.",
  52            regex_string, pcre_error, pcre_erroffset);
  53       continue;
  54       }
  55
  56     ri = store_get(sizeof(pcre_list));
  57     ri->re = re;
  58     ri->pcre_text = regex_string;
  59     ri->next = re_list_head;
  60     re_list_head = ri;
  61     }
  62 return re_list_head;
  63 }
  64
  65 static int
  66 matcher(pcre_list * re_list_head, uschar * linebuffer, int len)
  67 {
  68 pcre_list * ri;
  69
  70 for(ri = re_list_head; ri; ri = ri->next)
  71   {
  72   int ovec[3*(REGEX_VARS+1)];
  73   int n, nn;
  74
  75   /* try matcher on the line */
  76   n = pcre_exec(ri->re, NULL, CS linebuffer, len, 0, 0, ovec, nelem(ovec));
  77   if (n > 0)
  78     {
  79     Ustrncpy(regex_match_string_buffer, ri->pcre_text,
  80               sizeof(regex_match_string_buffer)-1);
  81     regex_match_string = regex_match_string_buffer;
  82
  83     for (nn = 1; nn < n; nn++)
  84       regex_vars[nn-1] =
  85         string_copyn(linebuffer + ovec[nn*2], ovec[nn*2+1] - ovec[nn*2]);
  86
  87     return OK;
  88     }
  89   }
  90 return FAIL;
  91 }
  92
  93 int
  94 regex(const uschar **listptr)
  95 {
  96 unsigned long mbox_size;
  97 FILE *mbox_file;
  98 pcre_list *re_list_head;
  99 uschar *linebuffer;
 100 long f_pos = 0;
 101 int ret = FAIL;
 102
 103 /* reset expansion variable */
 104 regex_match_string = NULL;
 105
 106 if (!mime_stream)                               /* We are in the DATA ACL */
 107   {
 108   if (!(mbox_file = spool_mbox(&mbox_size, NULL, NULL)))
 109     {                                           /* error while spooling */
 110     log_write(0, LOG_MAIN|LOG_PANIC,
 111            "regex acl condition: error while creating mbox spool file");
 112     return DEFER;
 113     }
 114   }
 115 else
 116   {
 117   if ((f_pos = ftell(mime_stream)) < 0)
 118     {
 119     log_write(0, LOG_MAIN|LOG_PANIC,
 120            "regex acl condition: mime_stream: %s", strerror(errno));
 121     return DEFER;
 122     }
 123   mbox_file = mime_stream;
 124   }
 125
 126 /* precompile our regexes */
 127 if (!(re_list_head = compile(*listptr)))
 128   return FAIL;                  /* no regexes -> nothing to do */
 129
 130 /* match each line against all regexes */
 131 linebuffer = store_get(32767);
 132 while (fgets(CS linebuffer, 32767, mbox_file))
 133   {
 134   if (  mime_stream && mime_current_boundary            /* check boundary */
 135      && Ustrncmp(linebuffer, "--", 2) == 0
 136      && Ustrncmp((linebuffer+2), mime_current_boundary,
 137                   Ustrlen(mime_current_boundary)) == 0)
 138       break;                                            /* found boundary */
 139
 140   if ((ret = matcher(re_list_head, linebuffer, (int)Ustrlen(linebuffer))) == OK)
 141     goto done;
 142   }
 143 /* no matches ... */
 144
 145 done:
 146 if (!mime_stream)
 147   (void)fclose(mbox_file);
 148 else
 149   {
 150   clearerr(mime_stream);
 151   if (fseek(mime_stream, f_pos, SEEK_SET) == -1)
 152     {
 153     log_write(0, LOG_MAIN|LOG_PANIC,
 154            "regex acl condition: mime_stream: %s", strerror(errno));
 155     clearerr(mime_stream);
 156     }
 157   }
 158
 159 return ret;
 160 }
 161
 162
 163 int
 164 mime_regex(const uschar **listptr)
 165 {
 166 pcre_list *re_list_head = NULL;
 167 FILE *f;
 168 uschar *mime_subject = NULL;
 169 int mime_subject_len = 0;
 170 int ret;
 171
 172 /* reset expansion variable */
 173 regex_match_string = NULL;
 174
 175 /* precompile our regexes */
 176 if (!(re_list_head = compile(*listptr)))
 177   return FAIL;                  /* no regexes -> nothing to do */
 178
 179 /* check if the file is already decoded */
 180 if (!mime_decoded_filename)
 181   {                             /* no, decode it first */
 182   const uschar *empty = US"";
 183   mime_decode(&empty);
 184   if (!mime_decoded_filename)
 185     {                           /* decoding failed */
 186     log_write(0, LOG_MAIN,
 187        "mime_regex acl condition warning - could not decode MIME part to file");
 188     return DEFER;
 189     }
 190   }
 191
 192 /* open file */
 193 if (!(f = fopen(CS mime_decoded_filename, "rb")))
 194   {
 195   log_write(0, LOG_MAIN,
 196        "mime_regex acl condition warning - can't open '%s' for reading",
 197        mime_decoded_filename);
 198   return DEFER;
 199   }
 200
 201 /* get 32k memory */
 202 mime_subject = store_get(32767);
 203
 204 mime_subject_len = fread(mime_subject, 1, 32766, f);
 205
 206 ret = matcher(re_list_head, mime_subject, mime_subject_len);
 207 (void)fclose(f);
 208 return ret;
 209 }
 210
 211 #endif /* WITH_CONTENT_SCAN */