src/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), FALSE);
  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 for(pcre_list * ri = re_list_head; ri; ri = ri->next)
  69   {
  70   int ovec[3*(REGEX_VARS+1)];
  71   int n;
  72
  73   /* try matcher on the line */
  74   if ((n = pcre_exec(ri->re, NULL, CS linebuffer, len, 0, 0, ovec, nelem(ovec))) > 0)
  75     {
  76     Ustrncpy(regex_match_string_buffer, ri->pcre_text,
  77               sizeof(regex_match_string_buffer)-1);
  78     regex_match_string = regex_match_string_buffer;
  79
  80     for (int nn = 1; nn < n; nn++)
  81       regex_vars[nn-1] =
  82         string_copyn(linebuffer + ovec[nn*2], ovec[nn*2+1] - ovec[nn*2]);
  83
  84     return OK;
  85     }
  86   }
  87 return FAIL;
  88 }
  89
  90 int
  91 regex(const uschar **listptr)
  92 {
  93 unsigned long mbox_size;
  94 FILE *mbox_file;
  95 pcre_list *re_list_head;
  96 uschar *linebuffer;
  97 long f_pos = 0;
  98 int ret = FAIL;
  99
 100 /* reset expansion variable */
 101 regex_match_string = NULL;
 102
 103 if (!mime_stream)                               /* We are in the DATA ACL */
 104   {
 105   if (!(mbox_file = spool_mbox(&mbox_size, NULL, NULL)))
 106     {                                           /* error while spooling */
 107     log_write(0, LOG_MAIN|LOG_PANIC,
 108            "regex acl condition: error while creating mbox spool file");
 109     return DEFER;
 110     }
 111   }
 112 else
 113   {
 114   if ((f_pos = ftell(mime_stream)) < 0)
 115     {
 116     log_write(0, LOG_MAIN|LOG_PANIC,
 117            "regex acl condition: mime_stream: %s", strerror(errno));
 118     return DEFER;
 119     }
 120   mbox_file = mime_stream;
 121   }
 122
 123 /* precompile our regexes */
 124 if (!(re_list_head = compile(*listptr)))
 125   return FAIL;                  /* no regexes -> nothing to do */
 126
 127 /* match each line against all regexes */
 128 linebuffer = store_get(32767, TRUE);    /* tainted */
 129 while (fgets(CS linebuffer, 32767, mbox_file))
 130   {
 131   if (  mime_stream && mime_current_boundary            /* check boundary */
 132      && Ustrncmp(linebuffer, "--", 2) == 0
 133      && Ustrncmp((linebuffer+2), mime_current_boundary,
 134                   Ustrlen(mime_current_boundary)) == 0)
 135       break;                                            /* found boundary */
 136
 137   if ((ret = matcher(re_list_head, linebuffer, (int)Ustrlen(linebuffer))) == OK)
 138     goto done;
 139   }
 140 /* no matches ... */
 141
 142 done:
 143 if (!mime_stream)
 144   (void)fclose(mbox_file);
 145 else
 146   {
 147   clearerr(mime_stream);
 148   if (fseek(mime_stream, f_pos, SEEK_SET) == -1)
 149     {
 150     log_write(0, LOG_MAIN|LOG_PANIC,
 151            "regex acl condition: mime_stream: %s", strerror(errno));
 152     clearerr(mime_stream);
 153     }
 154   }
 155
 156 return ret;
 157 }
 158
 159
 160 int
 161 mime_regex(const uschar **listptr)
 162 {
 163 pcre_list *re_list_head = NULL;
 164 FILE *f;
 165 uschar *mime_subject = NULL;
 166 int mime_subject_len = 0;
 167 int ret;
 168
 169 /* reset expansion variable */
 170 regex_match_string = NULL;
 171
 172 /* precompile our regexes */
 173 if (!(re_list_head = compile(*listptr)))
 174   return FAIL;                  /* no regexes -> nothing to do */
 175
 176 /* check if the file is already decoded */
 177 if (!mime_decoded_filename)
 178   {                             /* no, decode it first */
 179   const uschar *empty = US"";
 180   mime_decode(&empty);
 181   if (!mime_decoded_filename)
 182     {                           /* decoding failed */
 183     log_write(0, LOG_MAIN,
 184        "mime_regex acl condition warning - could not decode MIME part to file");
 185     return DEFER;
 186     }
 187   }
 188
 189 /* open file */
 190 if (!(f = fopen(CS mime_decoded_filename, "rb")))
 191   {
 192   log_write(0, LOG_MAIN,
 193        "mime_regex acl condition warning - can't open '%s' for reading",
 194        mime_decoded_filename);
 195   return DEFER;
 196   }
 197
 198 /* get 32k memory, tainted */
 199 mime_subject = store_get(32767, TRUE);
 200
 201 mime_subject_len = fread(mime_subject, 1, 32766, f);
 202
 203 ret = matcher(re_list_head, mime_subject, mime_subject_len);
 204 (void)fclose(f);
 205 return ret;
 206 }
 207
 208 #endif /* WITH_CONTENT_SCAN */