src/src/lookups/dnsdb.c

   1 /* $Cambridge: exim/src/src/lookups/dnsdb.c,v 1.5 2004/11/25 14:31:28 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   "mxh",
  36   "ns",
  37   "ptr",
  38   "srv",
  39   "txt",
  40   "zns"
  41 };
  42
  43 static int type_values[] = {
  44   T_A,
  45 #if HAVE_IPV6
  46   T_AAAA,
  47   #ifdef SUPPORT_A6
  48   T_A6,
  49   #endif
  50 #endif
  51   T_CNAME,
  52   T_MX,
  53   T_MXH,     /* Private type for "MX hostnames" */
  54   T_NS,
  55   T_PTR,
  56   T_SRV,
  57   T_TXT,
  58   T_ZNS      /* Private type for "zone nameservers" */
  59 };
  60
  61
  62 /*************************************************
  63 *              Open entry point                  *
  64 *************************************************/
  65
  66 /* See local README for interface description. */
  67
  68 void *
  69 dnsdb_open(uschar *filename, uschar **errmsg)
  70 {
  71 filename = filename;   /* Keep picky compilers happy */
  72 errmsg = errmsg;       /* Ditto */
  73 return (void *)(-1);   /* Any non-0 value */
  74 }
  75
  76
  77
  78 /*************************************************
  79 *           Find entry point for dnsdb           *
  80 *************************************************/
  81
  82 /* See local README for interface description. The query in the "keystring" may
  83 consist of a number of parts.
  84
  85 (a) If the first significant character is '>' then the next character is the
  86 separator character that is used when multiple records are found. The default
  87 separator is newline.
  88
  89 (b) If the next sequence of characters is a sequence of letters and digits
  90 followed by '=', it is interpreted as the name of the DNS record type. The
  91 default is "A".
  92
  93 (c) Then there follows list of domain names. This is a generalized Exim list,
  94 which may start with '<' in order to set a specific separator. The default
  95 separator, as always, is colon. */
  96
  97 int
  98 dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length,
  99   uschar **result, uschar **errmsg, BOOL *do_cache)
 100 {
 101 int rc;
 102 int size = 256;
 103 int ptr = 0;
 104 int sep = 0;
 105 int type = T_TXT;
 106 int failrc = FAIL;
 107 uschar *outsep = US"\n";
 108 uschar *equals, *domain;
 109 uschar buffer[256];
 110
 111 /* Because we're the working in the search pool, we try to reclaim as much
 112 store as possible later, so we preallocate the result here */
 113
 114 uschar *yield = store_get(size);
 115
 116 dns_record *rr;
 117 dns_answer dnsa;
 118 dns_scan dnss;
 119
 120 handle = handle;           /* Keep picky compilers happy */
 121 filename = filename;
 122 length = length;
 123 do_cache = do_cache;
 124
 125 /* If the string starts with '>' we change the output separator */
 126
 127 while (isspace(*keystring)) keystring++;
 128 if (*keystring == '>')
 129   {
 130   outsep = keystring + 1;
 131   keystring += 2;
 132   while (isspace(*keystring)) keystring++;
 133   }
 134
 135 /* If the keystring contains an = this must be preceded by a valid type name. */
 136
 137 if ((equals = Ustrchr(keystring, '=')) != NULL)
 138   {
 139   int i, len;
 140   uschar *tend = equals;
 141
 142   while (tend > keystring && isspace(tend[-1])) tend--;
 143   len = tend - keystring;
 144
 145   for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++)
 146     {
 147     if (len == Ustrlen(type_names[i]) &&
 148         strncmpic(keystring, US type_names[i], len) == 0)
 149       {
 150       type = type_values[i];
 151       break;
 152       }
 153     }
 154
 155   if (i >= sizeof(type_names)/sizeof(uschar *))
 156     {
 157     *errmsg = US"unsupported DNS record type";
 158     return DEFER;
 159     }
 160
 161   keystring = equals + 1;
 162   while (isspace(*keystring)) keystring++;
 163   }
 164
 165 /* Initialize the resolver in case this is the first time it has been used. */
 166
 167 dns_init(FALSE, FALSE);
 168
 169 /* The remainder of the string must be a list of domains. As long as the lookup
 170 for at least one of them succeeds, we return success. Failure means that none
 171 of them were found.
 172
 173 The original implementation did not support a list of domains. Adding the list
 174 feature is compatible, except in one case: when PTR records are being looked up
 175 for a single IPv6 address. Fortunately, we can hack in a compatibility feature
 176 here: If the type is PTR and no list separator is specified, and the entire
 177 remaining string is valid as an IP address, set an impossible separator so that
 178 it is treated as one item. */
 179
 180 if (type == T_PTR && keystring[0] != '<' &&
 181     string_is_ip_address(keystring, NULL) > 0)
 182   sep = -1;
 183
 184 /* Now scan the list and do a lookup for each item */
 185
 186 while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer)))
 187         != NULL)
 188   {
 189   uschar rbuffer[256];
 190   int searchtype = (type == T_ZNS)? T_NS :          /* record type we want */
 191                    (type == T_MXH)? T_MX : type;
 192
 193   /* If the type is PTR, we have to construct the relevant magic lookup
 194   key. This code is now in a separate function. */
 195
 196   if (type == T_PTR)
 197     {
 198     dns_build_reverse(domain, rbuffer);
 199     domain = rbuffer;
 200     }
 201
 202   DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain);
 203
 204   /* Do the lookup and sort out the result. There are two special types that
 205   are handled specially: T_ZNS and T_MXH. The former is handled in a special
 206   lookup function so that the facility could be used from other parts of the
 207   Exim code. The latter affects only what happens later on in this function,
 208   but for tidiness it is handled in a similar way. If the lookup fails,
 209   continue with the next domain. In the case of DEFER, adjust the final
 210   "nothing found" result, but carry on to the next domain. */
 211
 212   rc = dns_special_lookup(&dnsa, domain, type, NULL);
 213
 214   if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
 215   if (rc != DNS_SUCCEED)
 216     {
 217     failrc = DEFER;
 218     continue;
 219     }
 220
 221   /* Search the returned records */
 222
 223   for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
 224        rr != NULL;
 225        rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
 226     {
 227     if (rr->type != searchtype) continue;
 228
 229     /* There may be several addresses from an A6 record. Put the configured
 230     separator between them, just as for between several records. However, A6
 231     support is not normally configured these days. */
 232
 233     if (type == T_A ||
 234         #ifdef SUPPORT_A6
 235         type == T_A6 ||
 236         #endif
 237         type == T_AAAA)
 238       {
 239       dns_address *da;
 240       for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next)
 241         {
 242         if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
 243         yield = string_cat(yield, &size, &ptr, da->address,
 244           Ustrlen(da->address));
 245         }
 246       continue;
 247       }
 248
 249     /* Other kinds of record just have one piece of data each, but there may be
 250     several of them, of course. */
 251
 252     if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
 253
 254     if (type == T_TXT)
 255       {
 256       yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1),
 257         (rr->data)[0]);
 258       }
 259     else   /* T_CNAME, T_MX, T_MXH, T_NS, T_SRV, T_PTR */
 260       {
 261       int num;
 262       uschar s[264];
 263       uschar *p = (uschar *)(rr->data);
 264
 265       if (type == T_MXH)
 266         {
 267         /* mxh ignores the priority number and includes only the hostnames */
 268         GETSHORT(num, p);            /* pointer is advanced */
 269         }
 270       else if (type == T_MX)
 271         {
 272         GETSHORT(num, p);            /* pointer is advanced */
 273         sprintf(CS s, "%d ", num);
 274         yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 275         }
 276       else if (type == T_SRV)
 277         {
 278         int weight, port;
 279         GETSHORT(num, p);            /* pointer is advanced */
 280         GETSHORT(weight, p);
 281         GETSHORT(port, p);
 282         sprintf(CS s, "%d %d %d ", num, weight, port);
 283         yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 284         }
 285
 286       rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
 287         (DN_EXPAND_ARG4_TYPE)(s), sizeof(s));
 288
 289       /* If an overlong response was received, the data will have been
 290       truncated and dn_expand may fail. */
 291
 292       if (rc < 0)
 293         {
 294         log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
 295           "domain=%s", dns_text_type(type), domain);
 296         break;
 297         }
 298       else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
 299       }
 300     }    /* Loop for list of returned records */
 301   }      /* Loop for list of domains */
 302
 303 /* Reclaim unused memory */
 304
 305 store_reset(yield + ptr + 1);
 306
 307 /* If ptr == 0 we have not found anything. Otherwise, insert the terminating
 308 zero and return the result. */
 309
 310 if (ptr == 0) return failrc;
 311 yield[ptr] = 0;
 312 *result = yield;
 313 return OK;
 314 }
 315
 316 /* End of lookups/dnsdb.c */