mirror of git://git.gnupg.org/gnupg.git
332 lines
8.2 KiB
C
332 lines
8.2 KiB
C
/* srv.c - DNS SRV code
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* Copyright (C) 2003, 2009 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of either
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*
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* - the GNU Lesser General Public License as published by the Free
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* Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* or
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*
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* - the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at
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* your option) any later version.
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*
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* or both in parallel, as here.
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*
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* This file is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <config.h>
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#include <sys/types.h>
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#ifdef _WIN32
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#include <windows.h>
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#else
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#include <netinet/in.h>
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#include <arpa/nameser.h>
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#include <resolv.h>
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#endif
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#include <unistd.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#ifdef USE_ADNS
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# include <adns.h>
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# ifndef HAVE_ADNS_FREE
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# define adns_free free
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# endif
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#endif
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#include "util.h"
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#include "srv.h"
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/* Not every installation has gotten around to supporting SRVs
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yet... */
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#ifndef T_SRV
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#define T_SRV 33
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#endif
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static int
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priosort(const void *a,const void *b)
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{
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const struct srventry *sa=a,*sb=b;
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if(sa->priority>sb->priority)
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return 1;
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else if(sa->priority<sb->priority)
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return -1;
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else
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return 0;
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}
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int
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getsrv (const char *name,struct srventry **list)
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{
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int srvcount=0;
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u16 count;
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int i, rc;
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*list = NULL;
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#ifdef USE_ADNS
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{
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adns_state state;
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adns_answer *answer = NULL;
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rc = adns_init (&state, adns_if_noerrprint, NULL);
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if (rc)
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{
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log_error ("error initializing adns: %s\n", strerror (errno));
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return -1;
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}
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rc = adns_synchronous (state, name, adns_r_srv, adns_qf_quoteok_query,
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&answer);
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if (rc)
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{
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log_error ("DNS query failed: %s\n", strerror (errno));
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adns_finish (state);
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return -1;
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}
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if (answer->status != adns_s_ok
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|| answer->type != adns_r_srv || !answer->nrrs)
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{
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log_error ("DNS query returned an error or no records: %s (%s)\n",
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adns_strerror (answer->status),
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adns_errabbrev (answer->status));
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adns_free (answer);
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adns_finish (state);
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return 0;
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}
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for (count = 0; count < answer->nrrs; count++)
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{
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struct srventry *srv = NULL;
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struct srventry *newlist;
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if (strlen (answer->rrs.srvha[count].ha.host) >= MAXDNAME)
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{
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log_info ("hostname in SRV record too long - skipped\n");
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continue;
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}
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newlist = xtryrealloc (*list, (srvcount+1)*sizeof(struct srventry));
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if (!newlist)
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goto fail;
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*list = newlist;
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memset (&(*list)[srvcount], 0, sizeof(struct srventry));
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srv = &(*list)[srvcount];
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srvcount++;
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srv->priority = answer->rrs.srvha[count].priority;
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srv->weight = answer->rrs.srvha[count].weight;
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srv->port = answer->rrs.srvha[count].port;
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strcpy (srv->target, answer->rrs.srvha[count].ha.host);
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}
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adns_free (answer);
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adns_finish (state);
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}
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#else /*!USE_ADNS*/
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{
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unsigned char answer[2048];
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HEADER *header = (HEADER *)answer;
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unsigned char *pt, *emsg;
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int r;
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u16 dlen;
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r = res_query (name, C_IN, T_SRV, answer, sizeof answer);
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if (r < sizeof (HEADER) || r > sizeof answer)
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return -1;
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if (header->rcode != NOERROR || !(count=ntohs (header->ancount)))
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return 0; /* Error or no record found. */
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emsg = &answer[r];
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pt = &answer[sizeof(HEADER)];
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/* Skip over the query */
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rc = dn_skipname (pt, emsg);
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if (rc == -1)
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goto fail;
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pt += rc + QFIXEDSZ;
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while (count-- > 0 && pt < emsg)
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{
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struct srventry *srv=NULL;
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u16 type,class;
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struct srventry *newlist;
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newlist = xtryrealloc (*list, (srvcount+1)*sizeof(struct srventry));
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if (!newlist)
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goto fail;
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*list = newlist;
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memset(&(*list)[srvcount],0,sizeof(struct srventry));
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srv=&(*list)[srvcount];
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srvcount++;
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rc = dn_skipname(pt,emsg); /* the name we just queried for */
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if (rc == -1)
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goto fail;
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pt+=rc;
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/* Truncated message? */
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if((emsg-pt)<16)
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goto fail;
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type=*pt++ << 8;
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type|=*pt++;
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/* We asked for SRV and got something else !? */
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if(type!=T_SRV)
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goto fail;
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class=*pt++ << 8;
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class|=*pt++;
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/* We asked for IN and got something else !? */
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if(class!=C_IN)
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goto fail;
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pt+=4; /* ttl */
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dlen=*pt++ << 8;
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dlen|=*pt++;
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srv->priority=*pt++ << 8;
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srv->priority|=*pt++;
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srv->weight=*pt++ << 8;
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srv->weight|=*pt++;
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srv->port=*pt++ << 8;
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srv->port|=*pt++;
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/* Get the name. 2782 doesn't allow name compression, but
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dn_expand still works to pull the name out of the
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packet. */
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rc = dn_expand(answer,emsg,pt,srv->target,MAXDNAME);
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if (rc == 1 && srv->target[0] == 0) /* "." */
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{
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xfree(*list);
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*list = NULL;
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return 0;
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}
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if (rc == -1)
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goto fail;
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pt += rc;
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/* Corrupt packet? */
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if (dlen != rc+6)
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goto fail;
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}
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}
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#endif /*!USE_ADNS*/
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/* Now we have an array of all the srv records. */
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/* Order by priority */
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qsort(*list,srvcount,sizeof(struct srventry),priosort);
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/* For each priority, move the zero-weighted items first. */
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for (i=0; i < srvcount; i++)
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{
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int j;
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for (j=i;j < srvcount && (*list)[i].priority == (*list)[j].priority; j++)
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{
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if((*list)[j].weight==0)
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{
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/* Swap j with i */
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if(j!=i)
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{
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struct srventry temp;
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memcpy (&temp,&(*list)[j],sizeof(struct srventry));
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memcpy (&(*list)[j],&(*list)[i],sizeof(struct srventry));
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memcpy (&(*list)[i],&temp,sizeof(struct srventry));
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}
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break;
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}
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}
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}
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/* Run the RFC-2782 weighting algorithm. We don't need very high
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quality randomness for this, so regular libc srand/rand is
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sufficient. Fixme: It is a bit questionaly to reinitalize srand
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- better use a gnupg fucntion for this. */
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srand(time(NULL)*getpid());
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for (i=0; i < srvcount; i++)
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{
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int j;
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float prio_count=0,chose;
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for (j=i; j < srvcount && (*list)[i].priority == (*list)[j].priority; j++)
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{
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prio_count+=(*list)[j].weight;
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(*list)[j].run_count=prio_count;
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}
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chose=prio_count*rand()/RAND_MAX;
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for (j=i;j<srvcount && (*list)[i].priority==(*list)[j].priority;j++)
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{
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if (chose<=(*list)[j].run_count)
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{
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/* Swap j with i */
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if(j!=i)
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{
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struct srventry temp;
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memcpy(&temp,&(*list)[j],sizeof(struct srventry));
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memcpy(&(*list)[j],&(*list)[i],sizeof(struct srventry));
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memcpy(&(*list)[i],&temp,sizeof(struct srventry));
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}
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break;
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}
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}
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}
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return srvcount;
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fail:
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xfree(*list);
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*list=NULL;
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return -1;
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}
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#ifdef TEST
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int
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main(int argc,char *argv[])
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{
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struct srventry *srv;
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int rc,i;
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rc=getsrv("_hkp._tcp.wwwkeys.pgp.net",&srv);
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printf("Count=%d\n\n",rc);
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for(i=0;i<rc;i++)
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{
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printf("priority=%hu\n",srv[i].priority);
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printf("weight=%hu\n",srv[i].weight);
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printf("port=%hu\n",srv[i].port);
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printf("target=%s\n",srv[i].target);
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printf("\n");
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}
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xfree(srv);
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return 0;
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}
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#endif /* TEST */
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/*
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Local Variables:
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compile-command: "cc -DTEST -I.. -I../include -Wall -g -o srv srv.c -lresolv ../tools/no-libgcrypt.o ../jnlib/libjnlib.a"
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End:
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*/
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