release/src/router/samba3/source/libads/dns.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    DNS utility library
   4    Copyright (C) Gerald (Jerry) Carter           2006.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20
  21 #include "includes.h"
  22
  23 /* AIX resolv.h uses 'class' in struct ns_rr */
  24
  25 #if defined(AIX)
  26 #  if defined(class)
  27 #    undef class
  28 #  endif
  29 #endif  /* AIX */
  30
  31 /* resolver headers */
  32
  33 #include <sys/types.h>
  34 #include <netinet/in.h>
  35 #include <arpa/nameser.h>
  36 #include <resolv.h>
  37 #include <netdb.h>
  38
  39 #define MAX_DNS_PACKET_SIZE 0xffff
  40
  41 #ifdef NS_HFIXEDSZ      /* Bind 8/9 interface */
  42 #if !defined(C_IN)      /* AIX 5.3 already defines C_IN */
  43 #  define C_IN          ns_c_in
  44 #endif
  45 #if !defined(T_A)       /* AIX 5.3 already defines T_A */
  46 #  define T_A           ns_t_a
  47 #endif
  48 #  define T_SRV         ns_t_srv
  49 #else
  50 #  ifdef HFIXEDSZ
  51 #    define NS_HFIXEDSZ HFIXEDSZ
  52 #  else
  53 #    define NS_HFIXEDSZ sizeof(HEADER)
  54 #  endif        /* HFIXEDSZ */
  55 #  ifdef PACKETSZ
  56 #    define NS_PACKETSZ PACKETSZ
  57 #  else /* 512 is usually the default */
  58 #    define NS_PACKETSZ 512
  59 #  endif        /* PACKETSZ */
  60 #  define T_SRV         33
  61 #endif
  62
  63 /*********************************************************************
  64 *********************************************************************/
  65
  66 static BOOL ads_dns_parse_query( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
  67                           uint8 **ptr, struct dns_query *q )
  68 {
  69         uint8 *p = *ptr;
  70         pstring hostname;
  71         int namelen;
  72
  73         ZERO_STRUCTP( q );
  74
  75         if ( !start || !end || !q || !*ptr)
  76                 return False;
  77
  78         /* See RFC 1035 for details. If this fails, then return. */
  79
  80         namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
  81         if ( namelen < 0 ) {
  82                 return False;
  83         }
  84         p += namelen;
  85         q->hostname = talloc_strdup( ctx, hostname );
  86
  87         /* check that we have space remaining */
  88
  89         if ( PTR_DIFF(p+4, end) > 0 )
  90                 return False;
  91
  92         q->type     = RSVAL( p, 0 );
  93         q->in_class = RSVAL( p, 2 );
  94         p += 4;
  95
  96         *ptr = p;
  97
  98         return True;
  99 }
 100
 101 /*********************************************************************
 102 *********************************************************************/
 103
 104 static BOOL ads_dns_parse_rr( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
 105                        uint8 **ptr, struct dns_rr *rr )
 106 {
 107         uint8 *p = *ptr;
 108         pstring hostname;
 109         int namelen;
 110
 111         if ( !start || !end || !rr || !*ptr)
 112                 return -1;
 113
 114         ZERO_STRUCTP( rr );
 115         /* pull the name from the answer */
 116
 117         namelen = dn_expand( start, end, p, hostname, sizeof(hostname) );
 118         if ( namelen < 0 ) {
 119                 return -1;
 120         }
 121         p += namelen;
 122         rr->hostname = talloc_strdup( ctx, hostname );
 123
 124         /* check that we have space remaining */
 125
 126         if ( PTR_DIFF(p+10, end) > 0 )
 127                 return False;
 128
 129         /* pull some values and then skip onto the string */
 130
 131         rr->type     = RSVAL(p, 0);
 132         rr->in_class = RSVAL(p, 2);
 133         rr->ttl      = RIVAL(p, 4);
 134         rr->rdatalen = RSVAL(p, 8);
 135
 136         p += 10;
 137
 138         /* sanity check the available space */
 139
 140         if ( PTR_DIFF(p+rr->rdatalen, end ) > 0 ) {
 141                 return False;
 142
 143         }
 144
 145         /* save a point to the rdata for this section */
 146
 147         rr->rdata = p;
 148         p += rr->rdatalen;
 149
 150         *ptr = p;
 151
 152         return True;
 153 }
 154
 155 /*********************************************************************
 156 *********************************************************************/
 157
 158 static BOOL ads_dns_parse_rr_srv( TALLOC_CTX *ctx, uint8 *start, uint8 *end,
 159                        uint8 **ptr, struct dns_rr_srv *srv )
 160 {
 161         struct dns_rr rr;
 162         uint8 *p;
 163         pstring dcname;
 164         int namelen;
 165
 166         if ( !start || !end || !srv || !*ptr)
 167                 return -1;
 168
 169         /* Parse the RR entry.  Coming out of the this, ptr is at the beginning
 170            of the next record */
 171
 172         if ( !ads_dns_parse_rr( ctx, start, end, ptr, &rr ) ) {
 173                 DEBUG(1,("ads_dns_parse_rr_srv: Failed to parse RR record\n"));
 174                 return False;
 175         }
 176
 177         if ( rr.type != T_SRV ) {
 178                 DEBUG(1,("ads_dns_parse_rr_srv: Bad answer type (%d)\n", rr.type));
 179                 return False;
 180         }
 181
 182         p = rr.rdata;
 183
 184         srv->priority = RSVAL(p, 0);
 185         srv->weight   = RSVAL(p, 2);
 186         srv->port     = RSVAL(p, 4);
 187
 188         p += 6;
 189
 190         namelen = dn_expand( start, end, p, dcname, sizeof(dcname) );
 191         if ( namelen < 0 ) {
 192                 DEBUG(1,("ads_dns_parse_rr_srv: Failed to uncompress name!\n"));
 193                 return False;
 194         }
 195         srv->hostname = talloc_strdup( ctx, dcname );
 196
 197         return True;
 198 }
 199
 200
 201 /*********************************************************************
 202  Sort SRV record list based on weight and priority.  See RFC 2782.
 203 *********************************************************************/
 204
 205 static int dnssrvcmp( struct dns_rr_srv *a, struct dns_rr_srv *b )
 206 {
 207         if ( a->priority == b->priority ) {
 208
 209                 /* randomize entries with an equal weight and priority */
 210                 if ( a->weight == b->weight )
 211                         return 0;
 212
 213                 /* higher weights should be sorted lower */
 214                 if ( a->weight > b->weight )
 215                         return -1;
 216                 else
 217                         return 1;
 218         }
 219
 220         if ( a->priority < b->priority )
 221                 return -1;
 222
 223         return 1;
 224 }
 225
 226 /*********************************************************************
 227  Simple wrapper for a DNS SRV query
 228 *********************************************************************/
 229
 230 NTSTATUS ads_dns_lookup_srv( TALLOC_CTX *ctx, const char *name, struct dns_rr_srv **dclist, int *numdcs )
 231 {
 232         uint8 *buffer = NULL;
 233         size_t buf_len;
 234         int resp_len = NS_PACKETSZ;
 235         struct dns_rr_srv *dcs = NULL;
 236         int query_count, answer_count, auth_count, additional_count;
 237         uint8 *p = buffer;
 238         int rrnum;
 239         int idx = 0;
 240
 241         if ( !ctx || !name || !dclist ) {
 242                 return NT_STATUS_INVALID_PARAMETER;
 243         }
 244
 245         /* Send the request.  May have to loop several times in case
 246            of large replies */
 247
 248         do {
 249                 if ( buffer )
 250                         TALLOC_FREE( buffer );
 251
 252                 buf_len = resp_len * sizeof(uint8);
 253
 254                 if ( (buffer = TALLOC_ARRAY(ctx, uint8, buf_len)) == NULL ) {
 255                         DEBUG(0,("ads_dns_lookup_srv: talloc() failed!\n"));
 256                         return NT_STATUS_NO_MEMORY;
 257                 }
 258
 259                 if ( (resp_len = res_query(name, C_IN, T_SRV, buffer, buf_len)) < 0 ) {
 260                         DEBUG(1,("ads_dns_lookup_srv: Failed to resolve %s (%s)\n", name, strerror(errno)));
 261                         TALLOC_FREE( buffer );
 262                         return NT_STATUS_UNSUCCESSFUL;
 263                 }
 264         } while ( buf_len < resp_len && resp_len < MAX_DNS_PACKET_SIZE );
 265
 266         p = buffer;
 267
 268         /* For some insane reason, the ns_initparse() et. al. routines are only
 269            available in libresolv.a, and not the shared lib.  Who knows why....
 270            So we have to parse the DNS reply ourselves */
 271
 272         /* Pull the answer RR's count from the header.  Use the NMB ordering macros */
 273
 274         query_count      = RSVAL( p, 4 );
 275         answer_count     = RSVAL( p, 6 );
 276         auth_count       = RSVAL( p, 8 );
 277         additional_count = RSVAL( p, 10 );
 278
 279         DEBUG(4,("ads_dns_lookup_srv: %d records returned in the answer section.\n",
 280                 answer_count));
 281
 282         if ( (dcs = TALLOC_ZERO_ARRAY(ctx, struct dns_rr_srv, answer_count)) == NULL ) {
 283                 DEBUG(0,("ads_dns_lookup_srv: talloc() failure for %d char*'s\n",
 284                         answer_count));
 285                 return NT_STATUS_NO_MEMORY;
 286         }
 287
 288         /* now skip the header */
 289
 290         p += NS_HFIXEDSZ;
 291
 292         /* parse the query section */
 293
 294         for ( rrnum=0; rrnum<query_count; rrnum++ ) {
 295                 struct dns_query q;
 296
 297                 if ( !ads_dns_parse_query( ctx, buffer, buffer+resp_len, &p, &q ) ) {
 298                         DEBUG(1,("ads_dns_lookup_srv: Failed to parse query record!\n"));
 299                         return NT_STATUS_UNSUCCESSFUL;
 300                 }
 301         }
 302
 303         /* now we are at the answer section */
 304
 305         for ( rrnum=0; rrnum<answer_count; rrnum++ ) {
 306                 if ( !ads_dns_parse_rr_srv( ctx, buffer, buffer+resp_len, &p, &dcs[rrnum] ) ) {
 307                         DEBUG(1,("ads_dns_lookup_srv: Failed to parse answer record!\n"));
 308                         return NT_STATUS_UNSUCCESSFUL;
 309                 }
 310         }
 311         idx = rrnum;
 312
 313         /* Parse the authority section */
 314         /* just skip these for now */
 315
 316         for ( rrnum=0; rrnum<auth_count; rrnum++ ) {
 317                 struct dns_rr rr;
 318
 319                 if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
 320                         DEBUG(1,("ads_dns_lookup_srv: Failed to parse authority record!\n"));
 321                         return NT_STATUS_UNSUCCESSFUL;
 322                 }
 323         }
 324
 325         /* Parse the additional records section */
 326
 327         for ( rrnum=0; rrnum<additional_count; rrnum++ ) {
 328                 struct dns_rr rr;
 329                 int i;
 330
 331                 if ( !ads_dns_parse_rr( ctx, buffer, buffer+resp_len, &p, &rr ) ) {
 332                         DEBUG(1,("ads_dns_lookup_srv: Failed to parse additional records section!\n"));
 333                         return NT_STATUS_UNSUCCESSFUL;
 334                 }
 335
 336                 /* only interested in A records as a shortcut for having to come
 337                    back later and lookup the name.  For multi-homed hosts, the
 338                    number of additional records and exceed the number of answer
 339                    records. */
 340
 341
 342                 if ( (rr.type != T_A) || (rr.rdatalen != 4) )
 343                         continue;
 344
 345                 for ( i=0; i<idx; i++ ) {
 346                         if ( strcmp( rr.hostname, dcs[i].hostname ) == 0 ) {
 347                                 int num_ips = dcs[i].num_ips;
 348                                 uint8 *buf;
 349                                 struct in_addr *tmp_ips;
 350
 351                                 /* allocate new memory */
 352
 353                                 if ( dcs[i].num_ips == 0 ) {
 354                                         if ( (dcs[i].ips = TALLOC_ARRAY( dcs,
 355                                                 struct in_addr, 1 )) == NULL )
 356                                         {
 357                                                 return NT_STATUS_NO_MEMORY;
 358                                         }
 359                                 } else {
 360                                         if ( (tmp_ips = TALLOC_REALLOC_ARRAY( dcs, dcs[i].ips,
 361                                                 struct in_addr, dcs[i].num_ips+1)) == NULL )
 362                                         {
 363                                                 return NT_STATUS_NO_MEMORY;
 364                                         }
 365
 366                                         dcs[i].ips = tmp_ips;
 367                                 }
 368                                 dcs[i].num_ips++;
 369
 370                                 /* copy the new IP address */
 371
 372                                 buf = (uint8*)&dcs[i].ips[num_ips].s_addr;
 373                                 memcpy( buf, rr.rdata, 4 );
 374                         }
 375                 }
 376         }
 377
 378         qsort( dcs, idx, sizeof(struct dns_rr_srv), QSORT_CAST dnssrvcmp );
 379
 380         *dclist = dcs;
 381         *numdcs = idx;
 382
 383         return NT_STATUS_OK;
 384 }
 385
 386 /********************************************************************
 387 ********************************************************************/
 388
 389 NTSTATUS ads_dns_query_dcs( TALLOC_CTX *ctx, const char *domain, struct dns_rr_srv **dclist, int *numdcs )
 390 {
 391         pstring name;
 392
 393         snprintf( name, sizeof(name), "_ldap._tcp.dc._msdcs.%s", domain );
 394
 395         return ads_dns_lookup_srv( ctx, name, dclist, numdcs );
 396 }
 397