* http.c (connect_server): Use DNS SRV to get a server list. Fail over to

A records if necessary.

* Makefile.am, srv.h, srv.c: New DNS SRV handling code.

5 files changed, 387 insertions, 55 deletions

diff --git a/util/ChangeLog b/util/ChangeLog
index 035126606..b8c0a83a3 100644
--- a/util/ChangeLog
+++ b/util/ChangeLog
@@ -1,3 +1,10 @@
+2003-03-11  David Shaw  <[email protected]>
+
+	* http.c (connect_server): Use DNS SRV to get a server list.  Fail
+	over to A records if necessary.
+
+	* Makefile.am, srv.h, srv.c: New DNS SRV handling code.
+
 2003-02-22  David Shaw  <[email protected]>
 
 	* ttyio.c (tty_print_utf8_string, tty_print_utf8_string2): Use 0
diff --git a/util/Makefile.am b/util/Makefile.am
index b3c1e26e0..8853ac86b 100644
--- a/util/Makefile.am
+++ b/util/Makefile.am
@@ -27,14 +27,15 @@ EXTRA_libutil_a_SOURCES = regcomp.c regex.c regexec.c regex_internal.c regex_int
 #libutil_a_LDFLAGS =
 libutil_a_SOURCES = g10u.c logger.c fileutil.c miscutil.c strgutil.c  \
 		     ttyio.c  argparse.c memory.c secmem.c errors.c iobuf.c \
-		     dotlock.c http.c simple-gettext.c w32reg.c
+		     dotlock.c http.c srv.h srv.c simple-gettext.c w32reg.c
 
 libutil_a_DEPENDENCIES = @REGEX_O@
 libutil_a_LIBADD = @REGEX_O@
 
 http-test:  http.c
-	gcc -DHAVE_CONFIG_H -I. -I. -I.. $(INCLUDES) -g -Wall -DTEST \
-	    -o http-test http.c libutil.a ../mpi/libmpi.a @INTLLIBS@
-
-
+	gcc -DHAVE_CONFIG_H -I. -I. -I.. $(INCLUDES) $(LDFLAGS) -g -Wall \
+	    -DTEST -o http-test http.c libutil.a @INTLLIBS@ @SRVLIBS@ @CAPLIBS@
 
+srv-test:  srv.c
+	gcc -DHAVE_CONFIG_H -I. -I. -I.. $(INCLUDES) $(LDFLAGS) -g -Wall \
+	    -DTEST -o srv-test srv.c libutil.a @INTLLIBS@ @SRVLIBS@ @CAPLIBS@
diff --git a/util/http.c b/util/http.c
index fa3d512e9..4cc31e3c0 100644
--- a/util/http.c
+++ b/util/http.c
@@ -42,8 +42,8 @@
 #include "util.h"
 #include "iobuf.h"
 #include "i18n.h"
-
 #include "http.h"
+#include "srv.h"
 
 #ifdef __riscos__
   #define HTTP_PROXY_ENV           "GnuPG$HttpProxy"
@@ -80,7 +80,7 @@ static int send_request( HTTP_HD hd );
 static byte *build_rel_path( PARSED_URI uri );
 static int parse_response( HTTP_HD hd );
 
-static int connect_server( const char *server, ushort port );
+static int connect_server(const char *server, ushort port, unsigned int flags);
 static int write_server( int sock, const char *data, size_t length );
 
 #ifdef __MINGW32__
@@ -494,11 +494,11 @@ send_request( HTTP_HD hd )
 	    return G10ERR_NETWORK;
 	}
 	hd->sock = connect_server( *uri->host? uri->host : "localhost",
-				    uri->port? uri->port : 80 );
+				   uri->port? uri->port : 80, 0 );
 	release_parsed_uri( uri );
     }
     else
-	hd->sock = connect_server( server, port );
+      hd->sock = connect_server( server, port, hd->flags );
 
     if( hd->sock == -1 )
 	return G10ERR_NETWORK;
@@ -707,19 +707,17 @@ start_server()
 #endif
 
 
-
 static int
-connect_server( const char *server, ushort port )
+connect_server( const char *server, ushort port, unsigned int flags )
 {
-  int sock,i=0;
+  int sock,srv,srvcount=0;
   struct sockaddr_in addr;
   struct hostent *host=NULL;
-  unsigned long l;
+  struct srventry *srvlist=NULL;
 
   memset(&addr,0,sizeof(addr));
 
   addr.sin_family = AF_INET;
-  addr.sin_port = htons(port);
 
 #ifdef __MINGW32__
   init_sockets ();
@@ -740,63 +738,100 @@ connect_server( const char *server, ushort port )
 #ifdef __MINGW32__
   /* Win32 gethostbyname doesn't handle IP addresses internally, so we
      try inet_addr first on that platform only. */
-  if((l=inet_addr(server))==SOCKET_ERROR)
-#endif
-    if((host=gethostbyname(server))==NULL)
-      {
-#ifdef __MINGW32__
-	log_error("%s: host not found: ec=%d\n",server,(int)WSAGetLastError());
-#else
-	log_error("%s: host not found\n",server);
-#endif
-	sock_close(sock);
-	return -1;
-      }
-
-  if(host)
+  if((addr.sin_addr.s_addr=inet_addr(server))!=SOCKET_ERROR)
     {
-      if(host->h_addrtype != AF_INET)
-	{
-	  log_error ("%s: unknown address family\n", server);
-	  sock_close(sock);
-	  return -1;
-        }
+      addr.sin_port = htons(port);
 
-      if(host->h_length != 4 )
+      if(connect(sock,(struct sockaddr *)&addr,sizeof(addr))==0)
+	return sock;
+      else
 	{
-	  log_error ("%s: illegal address length\n", server);
 	  sock_close(sock);
 	  return -1;
 	}
+    }
+#endif
 
-      /* Try all A records until one responds. */
-      while(host->h_addr_list[i])
-	{
-	  memcpy(&addr.sin_addr,host->h_addr_list[i],host->h_length);
-
-	  if(connect(sock,(struct sockaddr *)&addr,sizeof(addr))==0)
-	    break;
+#ifdef USE_DNS_SRV
+  /* Do the SRV thing */
+  if(flags&HTTP_FLAG_TRY_SRV)
+    {
+      /* We're using SRV, so append the tags */
+      char srvname[MAXDNAME];
 
-	  i++;
-	}
+      strcpy(srvname,"_hkp._tcp.");
+      strncat(srvname,server,MAXDNAME-11);
+      srvname[MAXDNAME-1]='\0';
+      srvcount=getsrv(srvname,&srvlist);
+    }
+#endif
 
-      if(host->h_addr_list[i]==0)
-	{
-	  sock_close(sock);
-	  return -1;
-	}
+  if(srvlist==NULL)
+    {
+      /* Either we're not using SRV, or the SRV lookup failed.  Make
+	 up a fake SRV record. */
+      srvlist=m_alloc_clear(sizeof(struct srventry));
+      srvlist->port=port;
+      strncpy(srvlist->target,server,MAXDNAME);
+      srvcount=1;
     }
-  else
+
+  for(srv=0;srv<srvcount;srv++)
     {
-      memcpy(&addr.sin_addr,&l,sizeof(l));
+      int i=0;
 
-      if(connect(sock,(struct sockaddr *)&addr,sizeof(addr))!=0)
+      addr.sin_port = htons(srvlist[srv].port);
+
+      if((host=gethostbyname(srvlist[srv].target))==NULL)
+	continue;
+
+      if(host)
 	{
-	  sock_close(sock);
-	  return -1;
+	  if(host->h_addrtype != AF_INET)
+	    {
+	      log_error ("%s: unknown address family\n", srvlist[srv].target);
+	      sock_close(sock);
+	      m_free(srvlist);
+	      return -1;
+	    }
+
+	  if(host->h_length != 4 )
+	    {
+	      log_error ("%s: illegal address length\n", srvlist[srv].target);
+	      sock_close(sock);
+	      m_free(srvlist);
+	      return -1;
+	    }
+
+	  /* Try all A records until one responds. */
+	  while(host->h_addr_list[i])
+	    {
+	      memcpy(&addr.sin_addr,host->h_addr_list[i],host->h_length);
+
+	      if(connect(sock,(struct sockaddr *)&addr,sizeof(addr))==0)
+		break;
+
+	      i++;
+	    }
+
+	  if(host->h_addr_list[i])
+	    break;
 	}
     }
 
+  m_free(srvlist);
+
+  if(!host)
+    {
+#ifdef __MINGW32__
+      log_error("%s: host not found: ec=%d\n",server,(int)WSAGetLastError());
+#else
+      log_error("%s: host not found\n",server);
+#endif
+      sock_close(sock);
+      return -1;
+    }
+
     return sock;
 }
 
diff --git a/util/srv.c b/util/srv.c
new file mode 100644
index 000000000..8fc0ca0de
--- /dev/null
+++ b/util/srv.c
@@ -0,0 +1,246 @@
+/* srv.c - DNS SRV code
+ * Copyright (C) 2003 Free Software Foundation, Inc.
+ *
+ * This file is part of GNUPG.
+ *
+ * GNUPG is free software; you can redistribute it and/or modify
+ * it under the terms of 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.
+ *
+ * GNUPG 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#include <config.h>
+#ifdef USE_DNS_SRV
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "memory.h"
+#include "types.h"
+#include "srv.h"
+
+#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)
+{
+  char answer[PACKETSZ];
+  int r,srvcount=0;
+  char *pt,*emsg;
+  u16 count,dlen;
+
+  *list=NULL;
+
+  r=res_query(name,C_IN,T_SRV,answer,PACKETSZ);
+  if(r<sizeof(HEADER))
+    return -1;
+
+  if((((HEADER *)answer)->rcode)==NOERROR &&
+     (count=ntohs(((HEADER *)answer)->ancount)))
+    {
+      int i,rc;
+
+      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;
+
+	  *list=m_realloc(*list,(srvcount+1)*sizeof(struct srventry));
+	  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) /* "." */
+	    goto noanswer;
+	  if(rc==-1)
+	    goto fail;
+	  pt+=rc;
+	  /* Corrupt packet? */
+	  if(dlen!=rc+6)
+	    goto fail;
+
+#if 0
+	  printf("count=%d\n",srvcount);
+	  printf("priority=%d\n",srv->priority);
+	  printf("weight=%d\n",srv->weight);
+	  printf("port=%d\n",srv->port);
+	  printf("target=%s\n",srv->target);
+#endif
+	}
+
+      /* 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. */
+      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;
+
+ noanswer:
+  m_free(*list);
+  *list=NULL;
+  return 0;
+
+ fail:
+  m_free(*list);
+  *list=NULL;
+  return -1;
+}
+
+#endif /* USE_DNS_SRV */
+
+#ifdef TEST
+int
+main(int argc,char *argv[])
+{
+  struct srventry *srv;
+  int rc,i;
+
+  rc=getsrv("_hkp._tcp.pgp.net",&srv);
+  printf("Count=%d\n\n",rc);
+  for(i=0;i<rc;i++)
+    {
+      printf("priority=%d\n",srv[i].priority);
+      printf("weight=%d\n",srv[i].weight);
+      printf("port=%d\n",srv[i].port);
+      printf("target=%s\n",srv[i].target);
+      printf("\n");
+    }
+
+  m_free(srv);
+
+  return 0;
+}
+#endif /* TEST */
diff --git a/util/srv.h b/util/srv.h
new file mode 100644
index 000000000..518151f71
--- /dev/null
+++ b/util/srv.h
@@ -0,0 +1,43 @@
+/* srv.h
+ * Copyright (C) 2003 Free Software Foundation, Inc.
+ *
+ * This file is part of GNUPG.
+ *
+ * GNUPG is free software; you can redistribute it and/or modify
+ * it under the terms of 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.
+ *
+ * GNUPG 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#ifndef _SRV_H_
+#define _SRV_H_
+
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+
+#ifndef MAXDNAME
+#define MAXDNAME 1025
+#endif
+
+struct srventry
+{
+  uint16_t priority;
+  uint16_t weight;
+  uint16_t port;
+  int run_count;
+  char target[MAXDNAME];
+};
+
+int getsrv(const char *name,struct srventry **list);
+
+#endif /* !_SRV_H_ */