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/* srv.c - DNS SRV code
* Copyright (C) 2003, 2009 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of either
*
* - the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* - the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* or both in parallel, as here.
*
* This file is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <sys/types.h>
#ifdef _WIN32
# ifdef HAVE_WINSOCK2_H
# include <winsock2.h>
# endif
# include <windows.h>
#else
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#endif
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#ifdef USE_ADNS
# include <adns.h>
# ifndef HAVE_ADNS_FREE
# define adns_free free
# endif
#endif
#include "util.h"
#include "srv.h"
/* Not every installation has gotten around to supporting SRVs
yet... */
#ifndef T_SRV
#define T_SRV 33
#endif
static int
priosort(const void *a,const void *b)
{
const struct srventry *sa=a,*sb=b;
if(sa->priority>sb->priority)
return 1;
else if(sa->priority<sb->priority)
return -1;
else
return 0;
}
int
getsrv (const char *name,struct srventry **list)
{
int srvcount=0;
u16 count;
int i, rc;
*list = NULL;
#ifdef USE_ADNS
{
adns_state state;
adns_answer *answer = NULL;
rc = adns_init (&state, adns_if_noerrprint, NULL);
if (rc)
{
log_error ("error initializing adns: %s\n", strerror (errno));
return -1;
}
rc = adns_synchronous (state, name, adns_r_srv, adns_qf_quoteok_query,
&answer);
if (rc)
{
log_error ("DNS query failed: %s\n", strerror (errno));
adns_finish (state);
return -1;
}
if (answer->status != adns_s_ok
|| answer->type != adns_r_srv || !answer->nrrs)
{
log_error ("DNS query returned an error or no records: %s (%s)\n",
adns_strerror (answer->status),
adns_errabbrev (answer->status));
adns_free (answer);
adns_finish (state);
return 0;
}
for (count = 0; count < answer->nrrs; count++)
{
struct srventry *srv = NULL;
struct srventry *newlist;
if (strlen (answer->rrs.srvha[count].ha.host) >= MAXDNAME)
{
log_info ("hostname in SRV record too long - skipped\n");
continue;
}
newlist = xtryrealloc (*list, (srvcount+1)*sizeof(struct srventry));
if (!newlist)
goto fail;
*list = newlist;
memset (&(*list)[srvcount], 0, sizeof(struct srventry));
srv = &(*list)[srvcount];
srvcount++;
srv->priority = answer->rrs.srvha[count].priority;
srv->weight = answer->rrs.srvha[count].weight;
srv->port = answer->rrs.srvha[count].port;
strcpy (srv->target, answer->rrs.srvha[count].ha.host);
}
adns_free (answer);
adns_finish (state);
}
#else /*!USE_ADNS*/
{
unsigned char answer[2048];
HEADER *header = (HEADER *)answer;
unsigned char *pt, *emsg;
int r;
u16 dlen;
r = res_query (name, C_IN, T_SRV, answer, sizeof answer);
if (r < sizeof (HEADER) || r > sizeof answer)
return -1;
if (header->rcode != NOERROR || !(count=ntohs (header->ancount)))
return 0; /* Error or no record found. */
emsg = &answer[r];
pt = &answer[sizeof(HEADER)];
/* Skip over the query */
rc = dn_skipname (pt, emsg);
if (rc == -1)
goto fail;
pt += rc + QFIXEDSZ;
while (count-- > 0 && pt < emsg)
{
struct srventry *srv=NULL;
u16 type,class;
struct srventry *newlist;
newlist = xtryrealloc (*list, (srvcount+1)*sizeof(struct srventry));
if (!newlist)
goto fail;
*list = newlist;
memset(&(*list)[srvcount],0,sizeof(struct srventry));
srv=&(*list)[srvcount];
srvcount++;
rc = dn_skipname(pt,emsg); /* the name we just queried for */
if (rc == -1)
goto fail;
pt+=rc;
/* Truncated message? */
if((emsg-pt)<16)
goto fail;
type=*pt++ << 8;
type|=*pt++;
/* We asked for SRV and got something else !? */
if(type!=T_SRV)
goto fail;
class=*pt++ << 8;
class|=*pt++;
/* We asked for IN and got something else !? */
if(class!=C_IN)
goto fail;
pt+=4; /* ttl */
dlen=*pt++ << 8;
dlen|=*pt++;
srv->priority=*pt++ << 8;
srv->priority|=*pt++;
srv->weight=*pt++ << 8;
srv->weight|=*pt++;
srv->port=*pt++ << 8;
srv->port|=*pt++;
/* Get the name. 2782 doesn't allow name compression, but
dn_expand still works to pull the name out of the
packet. */
rc = dn_expand(answer,emsg,pt,srv->target,MAXDNAME);
if (rc == 1 && srv->target[0] == 0) /* "." */
{
xfree(*list);
*list = NULL;
return 0;
}
if (rc == -1)
goto fail;
pt += rc;
/* Corrupt packet? */
if (dlen != rc+6)
goto fail;
}
}
#endif /*!USE_ADNS*/
/* Now we have an array of all the srv records. */
/* Order by priority */
qsort(*list,srvcount,sizeof(struct srventry),priosort);
/* For each priority, move the zero-weighted items first. */
for (i=0; i < srvcount; i++)
{
int j;
for (j=i;j < srvcount && (*list)[i].priority == (*list)[j].priority; j++)
{
if((*list)[j].weight==0)
{
/* Swap j with i */
if(j!=i)
{
struct srventry temp;
memcpy (&temp,&(*list)[j],sizeof(struct srventry));
memcpy (&(*list)[j],&(*list)[i],sizeof(struct srventry));
memcpy (&(*list)[i],&temp,sizeof(struct srventry));
}
break;
}
}
}
/* Run the RFC-2782 weighting algorithm. We don't need very high
quality randomness for this, so regular libc srand/rand is
sufficient. Fixme: It is a bit questionaly to reinitalize srand
- better use a gnupg fucntion for this. */
srand(time(NULL)*getpid());
for (i=0; i < srvcount; i++)
{
int j;
float prio_count=0,chose;
for (j=i; j < srvcount && (*list)[i].priority == (*list)[j].priority; j++)
{
prio_count+=(*list)[j].weight;
(*list)[j].run_count=prio_count;
}
chose=prio_count*rand()/RAND_MAX;
for (j=i;j<srvcount && (*list)[i].priority==(*list)[j].priority;j++)
{
if (chose<=(*list)[j].run_count)
{
/* Swap j with i */
if(j!=i)
{
struct srventry temp;
memcpy(&temp,&(*list)[j],sizeof(struct srventry));
memcpy(&(*list)[j],&(*list)[i],sizeof(struct srventry));
memcpy(&(*list)[i],&temp,sizeof(struct srventry));
}
break;
}
}
}
return srvcount;
fail:
xfree(*list);
*list=NULL;
return -1;
}
#ifdef TEST
int
main(int argc,char *argv[])
{
struct srventry *srv;
int rc,i;
rc=getsrv("_hkp._tcp.wwwkeys.pgp.net",&srv);
printf("Count=%d\n\n",rc);
for(i=0;i<rc;i++)
{
printf("priority=%hu\n",srv[i].priority);
printf("weight=%hu\n",srv[i].weight);
printf("port=%hu\n",srv[i].port);
printf("target=%s\n",srv[i].target);
printf("\n");
}
xfree(srv);
return 0;
}
#endif /* TEST */
/*
Local Variables:
compile-command: "cc -DTEST -I.. -I../include -Wall -g -o srv srv.c -lresolv ../tools/no-libgcrypt.o ../common/libcommon.a"
End:
*/

File Metadata

Mime Type
text/x-c
Expires
Thu, Oct 16, 4:47 AM (9 h, 50 m)
Storage Engine
local-disk
Storage Format
Raw Data
Storage Handle
27/5e/b35c393c89ff1c56baf907dfe286

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