src/src/lookups/dnsdb.c

   1 /* $Cambridge: exim/src/src/lookups/dnsdb.c,v 1.1 2004/10/07 13:10:01 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
  40 static int type_values[] = {
  41   T_A,
  42 #if HAVE_IPV6
  43   T_AAAA,
  44   #ifdef SUPPORT_A6
  45   T_A6,
  46   #endif
  47 #endif
  48   T_CNAME,
  49   T_MX,
  50   T_NS,
  51   T_PTR,
  52   T_SRV,
  53   T_TXT };
  54
  55
  56 /*************************************************
  57 *              Open entry point                  *
  58 *************************************************/
  59
  60 /* See local README for interface description. */
  61
  62 void *
  63 dnsdb_open(uschar *filename, uschar **errmsg)
  64 {
  65 filename = filename;   /* Keep picky compilers happy */
  66 errmsg = errmsg;       /* Ditto */
  67 return (void *)(-1);   /* Any non-0 value */
  68 }
  69
  70
  71
  72 /*************************************************
  73 *           Find entry point for dnsdb           *
  74 *************************************************/
  75
  76 /* See local README for interface description. */
  77
  78 int
  79 dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length,
  80   uschar **result, uschar **errmsg, BOOL *do_cache)
  81 {
  82 int rc;
  83 int size = 256;
  84 int ptr = 0;
  85 int type = T_TXT;
  86 uschar *orig_keystring = keystring;
  87 uschar *equals = Ustrchr(keystring, '=');
  88 uschar buffer[256];
  89
  90 /* Because we're the working in the search pool, we try to reclaim as much
  91 store as possible later, so we preallocate the result here */
  92
  93 uschar *yield = store_get(size);
  94
  95 dns_record *rr;
  96 dns_answer dnsa;
  97 dns_scan dnss;
  98
  99 handle = handle;           /* Keep picky compilers happy */
 100 filename = filename;
 101 length = length;
 102 do_cache = do_cache;
 103
 104 /* If the keystring contains an = this is preceded by a type name. */
 105
 106 if (equals != NULL)
 107   {
 108   int i;
 109   int len = equals - keystring;
 110   for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++)
 111     {
 112     if (len == Ustrlen(type_names[i]) &&
 113         strncmpic(keystring, US type_names[i], len) == 0)
 114       {
 115       type = type_values[i];
 116       break;
 117       }
 118     }
 119   if (i >= sizeof(type_names)/sizeof(uschar *))
 120     {
 121     *errmsg = US"unsupported DNS record type";
 122     return DEFER;
 123     }
 124   keystring += len + 1;
 125   }
 126
 127 /* If the type is PTR, we have to construct the relevant magic lookup
 128 key. This code is now in a separate function. */
 129
 130 if (type == T_PTR)
 131   {
 132   dns_build_reverse(keystring, buffer);
 133   keystring = buffer;
 134   }
 135
 136 DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", keystring);
 137
 138 /* Initialize the resolver, in case this is the first time it is used
 139 in this run. Then do the lookup and sort out the result. */
 140
 141 dns_init(FALSE, FALSE);
 142 rc = dns_lookup(&dnsa, keystring, type, NULL);
 143
 144 if (rc == DNS_NOMATCH || rc == DNS_NODATA) return FAIL;
 145 if (rc != DNS_SUCCEED) return DEFER;
 146
 147 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
 148      rr != NULL;
 149      rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
 150   {
 151   if (rr->type != type) continue;
 152
 153   /* There may be several addresses from an A6 record. Put newlines between
 154   them, just as for between several records. */
 155
 156   if (type == T_A ||
 157       #ifdef SUPPORT_A6
 158       type == T_A6 ||
 159       #endif
 160       type == T_AAAA)
 161     {
 162     dns_address *da;
 163     for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next)
 164       {
 165       if (ptr != 0) yield = string_cat(yield, &size, &ptr, US"\n", 1);
 166       yield = string_cat(yield, &size, &ptr, da->address, Ustrlen(da->address));
 167       }
 168     continue;
 169     }
 170
 171   /* Other kinds of record just have one piece of data each. */
 172
 173   if (ptr != 0) yield = string_cat(yield, &size, &ptr, US"\n", 1);
 174
 175   if (type == T_TXT)
 176     {
 177     yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1),
 178       (rr->data)[0]);
 179     }
 180   else   /* T_CNAME, T_MX, T_NS, T_PTR */
 181     {
 182     uschar s[264];
 183     uschar *p = (uschar *)(rr->data);
 184     if (type == T_MX)
 185       {
 186       int num;
 187       GETSHORT(num, p);            /* pointer is advanced */
 188       sprintf(CS s, "%d ", num);
 189       yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 190       }
 191     else if (type == T_SRV)
 192       {
 193       int num, weight, port;
 194       GETSHORT(num, p);            /* pointer is advanced */
 195       GETSHORT(weight, p);
 196       GETSHORT(port, p);
 197       sprintf(CS s, "%d %d %d ", num, weight, port);
 198       yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 199       }
 200     rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
 201       (DN_EXPAND_ARG4_TYPE)(s), sizeof(s));
 202
 203     /* If an overlong response was received, the data will have been
 204     truncated and dn_expand may fail. */
 205
 206     if (rc < 0)
 207       {
 208       log_write(0, LOG_MAIN, "host name alias list truncated for %s",
 209         orig_keystring);
 210       break;
 211       }
 212     else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 213     }
 214   }
 215
 216 yield[ptr] = 0;
 217 store_reset(yield + ptr + 1);    /* Reclaim unused */
 218 *result = yield;
 219
 220 return OK;
 221 }
 222
 223 /* End of lookups/dnsdb.c */