src/src/lookups/dnsdb.c

   1 /* $Cambridge: exim/src/src/lookups/dnsdb.c,v 1.2 2004/11/19 09:45:54 ph10 Exp $ */
   2
   3 /*************************************************
   4 *     Exim - an Internet mail transport agent    *
   5 *************************************************/
   6
   7 /* Copyright (c) University of Cambridge 1995 - 2004 */
   8 /* See the file NOTICE for conditions of use and distribution. */
   9
  10 #include "../exim.h"
  11 #include "lf_functions.h"
  12 #include "dnsdb.h"
  13
  14
  15
  16 /* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their
  17 header files. */
  18
  19 #ifndef T_TXT
  20 #define T_TXT 16
  21 #endif
  22
  23 /* Table of recognized DNS record types and their integer values. */
  24
  25 static char *type_names[] = {
  26   "a",
  27 #if HAVE_IPV6
  28   "aaaa",
  29   #ifdef SUPPORT_A6
  30   "a6",
  31   #endif
  32 #endif
  33   "cname",
  34   "mx",
  35   "ns",
  36   "ptr",
  37   "srv",
  38   "txt",
  39   "zns"
  40 };
  41
  42 static int type_values[] = {
  43   T_A,
  44 #if HAVE_IPV6
  45   T_AAAA,
  46   #ifdef SUPPORT_A6
  47   T_A6,
  48   #endif
  49 #endif
  50   T_CNAME,
  51   T_MX,
  52   T_NS,
  53   T_PTR,
  54   T_SRV,
  55   T_TXT,
  56   T_ZNS      /* Private type for "zone nameservers" */
  57 };
  58
  59
  60 /*************************************************
  61 *              Open entry point                  *
  62 *************************************************/
  63
  64 /* See local README for interface description. */
  65
  66 void *
  67 dnsdb_open(uschar *filename, uschar **errmsg)
  68 {
  69 filename = filename;   /* Keep picky compilers happy */
  70 errmsg = errmsg;       /* Ditto */
  71 return (void *)(-1);   /* Any non-0 value */
  72 }
  73
  74
  75
  76 /*************************************************
  77 *           Find entry point for dnsdb           *
  78 *************************************************/
  79
  80 /* See local README for interface description. */
  81
  82 int
  83 dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length,
  84   uschar **result, uschar **errmsg, BOOL *do_cache)
  85 {
  86 int rc;
  87 int size = 256;
  88 int ptr = 0;
  89 int type = T_TXT;
  90 uschar *orig_keystring = keystring;
  91 uschar *equals = Ustrchr(keystring, '=');
  92 uschar buffer[256];
  93
  94 /* Because we're the working in the search pool, we try to reclaim as much
  95 store as possible later, so we preallocate the result here */
  96
  97 uschar *yield = store_get(size);
  98
  99 dns_record *rr;
 100 dns_answer dnsa;
 101 dns_scan dnss;
 102
 103 handle = handle;           /* Keep picky compilers happy */
 104 filename = filename;
 105 length = length;
 106 do_cache = do_cache;
 107
 108 /* If the keystring contains an = this is preceded by a type name. */
 109
 110 if (equals != NULL)
 111   {
 112   int i;
 113   int len = equals - keystring;
 114   for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++)
 115     {
 116     if (len == Ustrlen(type_names[i]) &&
 117         strncmpic(keystring, US type_names[i], len) == 0)
 118       {
 119       type = type_values[i];
 120       break;
 121       }
 122     }
 123   if (i >= sizeof(type_names)/sizeof(uschar *))
 124     {
 125     *errmsg = US"unsupported DNS record type";
 126     return DEFER;
 127     }
 128   keystring += len + 1;
 129   }
 130
 131 /* If the type is PTR, we have to construct the relevant magic lookup
 132 key. This code is now in a separate function. */
 133
 134 if (type == T_PTR)
 135   {
 136   dns_build_reverse(keystring, buffer);
 137   keystring = buffer;
 138   }
 139
 140 DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", keystring);
 141
 142 /* Initialize the resolver, in case this is the first time it is used
 143 in this run. Then do the lookup and sort out the result. */
 144
 145 dns_init(FALSE, FALSE);
 146 rc = dns_special_lookup(&dnsa, keystring, type, NULL);
 147
 148 if (rc == DNS_NOMATCH || rc == DNS_NODATA) return FAIL;
 149 if (rc != DNS_SUCCEED) return DEFER;
 150
 151 /* If the lookup was a pseudo-type, change it to the correct type for searching
 152 the returned records; then search for them. */
 153
 154 if (type == T_ZNS) type = T_NS;
 155 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
 156      rr != NULL;
 157      rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
 158   {
 159   if (rr->type != type) continue;
 160
 161   /* There may be several addresses from an A6 record. Put newlines between
 162   them, just as for between several records. */
 163
 164   if (type == T_A ||
 165       #ifdef SUPPORT_A6
 166       type == T_A6 ||
 167       #endif
 168       type == T_AAAA)
 169     {
 170     dns_address *da;
 171     for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next)
 172       {
 173       if (ptr != 0) yield = string_cat(yield, &size, &ptr, US"\n", 1);
 174       yield = string_cat(yield, &size, &ptr, da->address, Ustrlen(da->address));
 175       }
 176     continue;
 177     }
 178
 179   /* Other kinds of record just have one piece of data each. */
 180
 181   if (ptr != 0) yield = string_cat(yield, &size, &ptr, US"\n", 1);
 182
 183   if (type == T_TXT)
 184     {
 185     yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1),
 186       (rr->data)[0]);
 187     }
 188   else   /* T_CNAME, T_MX, T_NS, T_PTR */
 189     {
 190     uschar s[264];
 191     uschar *p = (uschar *)(rr->data);
 192     if (type == T_MX)
 193       {
 194       int num;
 195       GETSHORT(num, p);            /* pointer is advanced */
 196       sprintf(CS s, "%d ", num);
 197       yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 198       }
 199     else if (type == T_SRV)
 200       {
 201       int num, weight, port;
 202       GETSHORT(num, p);            /* pointer is advanced */
 203       GETSHORT(weight, p);
 204       GETSHORT(port, p);
 205       sprintf(CS s, "%d %d %d ", num, weight, port);
 206       yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 207       }
 208     rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
 209       (DN_EXPAND_ARG4_TYPE)(s), sizeof(s));
 210
 211     /* If an overlong response was received, the data will have been
 212     truncated and dn_expand may fail. */
 213
 214     if (rc < 0)
 215       {
 216       log_write(0, LOG_MAIN, "host name alias list truncated for %s",
 217         orig_keystring);
 218       break;
 219       }
 220     else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 221     }
 222   }
 223
 224 yield[ptr] = 0;
 225 store_reset(yield + ptr + 1);    /* Reclaim unused */
 226 *result = yield;
 227
 228 return OK;
 229 }
 230
 231 /* End of lookups/dnsdb.c */