Fix DHCPv6 address allocation for some pathalogical cases.

CHANGELOG

@@ -1,3 +1,19 @@
+version 2.64
+            Handle DHCP FQDN options with all flag bits zero and
+            --dhcp-client-update set. Thanks to Bernd Krumbroeck for
+            spotting the problem.
+
+	    Finesse the check for /etc/hosts names which conflict with
+	    DHCP names. Previously a name/address pair in /etc/hosts
+	    which didn't match the name/address of a DHCP lease would
+	    generate a warning. Now that only happesn if there is not
+	    also a match. This allows multiple addresses for a name in 
+	    /etc/hosts with one of them assigned via DHCP.
+
+	    Fix broken vendor-option processing for BOOTP. Thanks to
+	    Hans-Joachim Baader for the bug report.
+
+
 version 2.63
             Do duplicate dhcp-host address check in --test mode.
 

bld/get-version

@@ -8,6 +8,8 @@
 # which has a set of references substituted into it by git.
 # If we can find one which matches $v[0-9].* then we assume it's
 # a version-number tag, else we just use the whole string.
+# If there is more than one v[0-9].* tag, sort them and use the
+# first. This favours, eg v2.63 over 2.63rc6.
 
 if which git >/dev/null 2>&1 && [ -d $1/.git ]; then
      cd $1; git describe
@@ -18,7 +20,7 @@ else
      vers=`cat $1/VERSION | sed 's/[(), ]/,/ g' | tr ',' '\n' | grep $v[0-9]`
 
      if [ $? -eq 0 ]; then
-         echo "${vers}" | head -n 1 | sed 's/^v//'
+         echo "${vers}" | sort | head -n 1 | sed 's/^v//'
      else
          cat $1/VERSION
      fi

debian/changelog

@@ -1,3 +1,25 @@
+dnsmasq (2.64-1) unstable; urgency=low
+
+   * New upstream.
+
+ -- Simon Kelley <simon@thekelleys.org.uk>  Tue, 4 Sep 2012 21:50:22 +0000
+
+dnsmasq (2.63-3) unstable; urgency=low
+
+   * Move adduser dependency to dnsmasq-base. (closes: #686694)
+
+ -- Simon Kelley <simon@thekelleys.org.uk>  Tue, 4 Sep 2012 21:44:15 +0000
+
+dnsmasq (2.63-2) unstable; urgency=low
+
+   * Fix version script to report correct version.
+   * Unbotch move of dbus config file by using correct versions in
+     Replaces: and Breaks: lines. (closes: #685204)
+   * Create dnsmasq user in dnsmasq-base so that Dbus doesn't complain if
+     only dnsmasq-base is installed. (closes: #685987)
+
+ -- Simon Kelley <simon@thekelleys.org.uk>  Tue, 28 Aug 2012 16:18:35 +0000
+
 dnsmasq (2.63-1) unstable; urgency=low
 
    * New upstream.

debian/control

@@ -7,7 +7,7 @@ Standards-Version: 3.9.3
 
 Package: dnsmasq
 Architecture: all
-Depends: netbase, adduser, dnsmasq-base(>= ${source:Version})
+Depends: netbase, dnsmasq-base(>= ${source:Version})
 Suggests: resolvconf
 Conflicts: resolvconf (<<1.15)
 Description: Small caching DNS proxy and DHCP/TFTP server
@@ -22,9 +22,9 @@ Description: Small caching DNS proxy and DHCP/TFTP server
 
 Package: dnsmasq-base
 Architecture: any
-Depends: ${shlibs:Depends}
-Breaks: dnsmasq (<< 2.62-3)
-Replaces: dnsmasq (<< 2.62-3)
+Depends: adduser, ${shlibs:Depends}
+Breaks: dnsmasq (<< 2.63-1~)
+Replaces: dnsmasq (<< 2.63-1~)
 Description: Small caching DNS proxy and DHCP/TFTP server
  This package contains the dnsmasq executable and documentation, but
  not the infrastructure required to run it as a system daemon. For

debian/dnsmasq-base.postinst

@@ -0,0 +1,24 @@
+#!/bin/sh
+set -e
+
+# Create the dnsmasq user in dnsmasq-base, so that Dbus doesn't complain.
+      
+# create a user to run as (code stolen from dovecot-common)
+if [ "$1" = "configure" ]; then
+  if [ -z "`id -u dnsmasq 2> /dev/null`" ]; then
+    adduser --system  --home /var/lib/misc --gecos "dnsmasq" \
+            --no-create-home --disabled-password \
+            --quiet dnsmasq || true
+  fi
+
+  # Make the directory where we keep the pid file - this
+  # has to be owned by "dnsmasq" so that the file can be unlinked.
+  # This is only actually used by the dnsmasq binary package, not
+  # dnsmasq-base, but it's much easier to create it here so that
+  # we don't have synchronisation issues with the creation of the
+  # dnsmasq user. 
+  if [ ! -d /var/run/dnsmasq ]; then
+    mkdir /var/run/dnsmasq
+    chown dnsmasq:nogroup /var/run/dnsmasq
+  fi
+fi

debian/dnsmasq-base.postrm

@@ -0,0 +1,11 @@
+#!/bin/sh
+set -e
+
+if [ purge = "$1" ]; then
+   if [ -x "$(command -v deluser)" ]; then
+     deluser --quiet --system dnsmasq > /dev/null || true
+  else
+     echo >&2 "not removing dnsmasq system account because deluser command was not found"
+  fi
+  rm -rf /var/run/dnsmasq
+fi

debian/postinst

@@ -1,27 +1,6 @@
 #!/bin/sh
 set -e
 
-# create a user to run as (code stolen from dovecot-common)
-if [ "$1" = "configure" ]; then
-  if [ -z "`id -u dnsmasq 2> /dev/null`" ]; then
-    adduser --system  --home /var/lib/misc --gecos "dnsmasq" \
-            --no-create-home --disabled-password \
-            --quiet dnsmasq || true
-  fi
-
-  # Make the directory where we keep the pid file - this
-  # has to be owned by "dnsmasq" do that the file can be unlinked.
-  if [ ! -d /var/run/dnsmasq ]; then
-    mkdir /var/run/dnsmasq
-    chown dnsmasq:nogroup /var/run/dnsmasq
-  fi
-
-  # handle new location of pidfile during an upgrade
-  if [ -e /var/run/dnsmasq.pid ]; then
-      mv /var/run/dnsmasq.pid /var/run/dnsmasq
-  fi
-fi
-
 if [ -x /etc/init.d/dnsmasq ]; then
    update-rc.d dnsmasq defaults 15 85 >/dev/null
 
@@ -40,10 +19,4 @@ if [ -x /etc/init.d/dnsmasq ]; then
    fi
 fi
 
-# dpkg can botch the change of /usr/share/doc/dnsmasq from
-# directory to symlink. Fix up here.
-if [ ! -h /usr/share/doc/dnsmasq ] && { rmdir /usr/share/doc/dnsmasq; }; then
-   cd /usr/share/doc/
-   ln -s /usr/share/doc/dnsmasq-base dnsmasq
-fi
 

debian/postrm

@@ -3,10 +3,4 @@ set -e
 
 if [ purge = "$1" ]; then
    update-rc.d dnsmasq remove >/dev/null
-   if [ -x "$(command -v deluser)" ]; then
-     deluser --quiet --system dnsmasq > /dev/null || true
-  else
-     echo >&2 "not removing dnsmasq system account because deluser command was not found"
-  fi
-  rm -rf /var/run/dnsmasq
 fi

debian/rules

@@ -129,6 +129,8 @@ ifeq (,$(findstring nodocs,$(DEB_BUILD_OPTIONS)))
 	gzip -9 debian/base/usr/share/doc/$(package)/DBus-interface	
 endif
 	install -m 644 debian/dnsmasq-base.conffiles debian/base/DEBIAN/conffiles
+	install -m 755 debian/dnsmasq-base.postinst debian/base/DEBIAN/postinst
+	install -m 755 debian/dnsmasq-base.postrm  debian/base/DEBIAN/postrm
 	install -m 644 debian/changelog debian/base/usr/share/doc/$(package)/changelog.Debian
 	gzip -9 debian/base/usr/share/doc/$(package)/changelog.Debian
 	install -m 644 debian/readme debian/base/usr/share/doc/$(package)/README.Debian

src/cache.c

@@ -1042,7 +1042,7 @@ static void add_dhcp_cname(struct crec *target, time_t ttd)
 void cache_add_dhcp_entry(char *host_name, int prot,
 			  struct all_addr *host_address, time_t ttd) 
 {
-  struct crec *crec = NULL;
+  struct crec *crec = NULL, *fail_crec = NULL;
   unsigned short flags = F_IPV4;
   int in_hosts = 0;
   size_t addrlen = sizeof(struct in_addr);
@@ -1055,28 +1055,21 @@ void cache_add_dhcp_entry(char *host_name, int prot,
     }
 #endif
   
+  inet_ntop(prot, host_address, daemon->addrbuff, ADDRSTRLEN);
+  
   while ((crec = cache_find_by_name(crec, host_name, 0, flags | F_CNAME)))
     {
       /* check all addresses associated with name */
       if (crec->flags & F_HOSTS)
 	{
-	  /* if in hosts, don't need DHCP record */
-	  in_hosts = 1;
-	  
-	  inet_ntop(prot, host_address, daemon->addrbuff, ADDRSTRLEN);
 	  if (crec->flags & F_CNAME)
 	    my_syslog(MS_DHCP | LOG_WARNING, 
 		      _("%s is a CNAME, not giving it to the DHCP lease of %s"),
 		      host_name, daemon->addrbuff);
-	  else if (memcmp(&crec->addr.addr, host_address, addrlen) != 0)
-	    {
-	      inet_ntop(prot, &crec->addr.addr, daemon->namebuff, MAXDNAME);
-	      my_syslog(MS_DHCP | LOG_WARNING, 
-			_("not giving name %s to the DHCP lease of %s because "
-			  "the name exists in %s with address %s"), 
-			host_name, daemon->addrbuff,
-			record_source(crec->uid), daemon->namebuff);
-	    }	  
+	  else if (memcmp(&crec->addr.addr, host_address, addrlen) == 0)
+	    in_hosts = 1;
+	  else
+	    fail_crec = crec;
 	}
       else if (!(crec->flags & F_DHCP))
 	{
@@ -1086,21 +1079,34 @@ void cache_add_dhcp_entry(char *host_name, int prot,
 	}
     }
   
-   if (in_hosts)
+  /* if in hosts, don't need DHCP record */
+  if (in_hosts)
     return;
-
-   if ((crec = cache_find_by_addr(NULL, (struct all_addr *)host_address, 0, flags)))
-     {
-       if (crec->flags & F_NEG)
-	 {
-	   flags |= F_REVERSE;
-	   cache_scan_free(NULL, (struct all_addr *)host_address, 0, flags);
-	 }
-     }
-   else
-      flags |= F_REVERSE;
-   
-   if ((crec = dhcp_spare))
+  
+  /* Name in hosts, address doesn't match */
+  if (fail_crec)
+    {
+      inet_ntop(prot, &fail_crec->addr.addr, daemon->namebuff, MAXDNAME);
+      my_syslog(MS_DHCP | LOG_WARNING, 
+		_("not giving name %s to the DHCP lease of %s because "
+		  "the name exists in %s with address %s"), 
+		host_name, daemon->addrbuff,
+		record_source(fail_crec->uid), daemon->namebuff);
+      return;
+    }	  
+  
+  if ((crec = cache_find_by_addr(NULL, (struct all_addr *)host_address, 0, flags)))
+    {
+      if (crec->flags & F_NEG)
+	{
+	  flags |= F_REVERSE;
+	  cache_scan_free(NULL, (struct all_addr *)host_address, 0, flags);
+	}
+    }
+  else
+    flags |= F_REVERSE;
+  
+  if ((crec = dhcp_spare))
     dhcp_spare = dhcp_spare->next;
   else /* need new one */
     crec = whine_malloc(sizeof(struct crec));

src/dnsmasq.c

@@ -383,15 +383,48 @@ int main (int argc, char **argv)
       /* write pidfile _after_ forking ! */
       if (daemon->runfile)
 	{
-	  FILE *pidfile;
+	  int fd, err = 0;
+
+	  sprintf(daemon->namebuff, "%d\n", (int) getpid());
+
+	  /* Explanation: Some installations of dnsmasq (eg Debian/Ubuntu) locate the pid-file
+	     in a directory which is writable by the non-privileged user that dnsmasq runs as. This
+	     allows the daemon to delete the file as part of its shutdown. This is a security hole to the 
+	     extent that an attacker running as the unprivileged  user could replace the pidfile with a 
+	     symlink, and have the target of that symlink overwritten as root next time dnsmasq starts. 
+
+	     The folowing code first deletes any existing file, and then opens it with the O_EXCL flag,
+	     ensuring that the open() fails should there be any existing file (because the unlink() failed, 
+	     or an attacker exploited the race between unlink() and open()). This ensures that no symlink
+	     attack can succeed. 
+
+	     Any compromise of the non-privileged user still theoretically allows the pid-file to be
+	     replaced whilst dnsmasq is running. The worst that could allow is that the usual 
+	     "shutdown dnsmasq" shell command could be tricked into stopping any other process.
+
+	     Note that if dnsmasq is started as non-root (eg for testing) it silently ignores 
+	     failure to write the pid-file.
+	  */
+
+	  unlink(daemon->runfile); 
 	  
-	  /* only complain if started as root */
-	  if ((pidfile = fopen(daemon->runfile, "w")))
+	  if ((fd = open(daemon->runfile, O_WRONLY|O_CREAT|O_TRUNC|O_EXCL, S_IWUSR|S_IRUSR|S_IRGRP|S_IROTH)) == -1)
 	    {
-	      fprintf(pidfile, "%d\n", (int) getpid());
-	      fclose(pidfile);
+	      /* only complain if started as root */
+	      if (getuid() == 0)
+		err = 1;
 	    }
-	  else if (getuid() == 0)
+	  else
+	    {
+	      if (!read_write(fd, (unsigned char *)daemon->namebuff, strlen(daemon->namebuff), 0))
+		err = 1;
+	      
+	      while (!err && close(fd) == -1)
+		if (!retry_send())
+		  err = 1;
+	    }
+
+	  if (err)
 	    {
 	      send_event(err_pipe[1], EVENT_PIDFILE, errno, daemon->runfile);
 	      _exit(0);
@@ -607,7 +640,7 @@ int main (int argc, char **argv)
 	      end = &dhcp_tmp->end6;
 	      struct in6_addr subnet = dhcp_tmp->start6;
 	      setaddr6part(&subnet, 0);
-	      inet_ntop(AF_INET6, &subnet, daemon->addrbuff, 256);
+	      inet_ntop(AF_INET6, &subnet, daemon->dhcp_buff2, 256);
 	    }
 #endif
 	  
@@ -620,10 +653,8 @@ int main (int argc, char **argv)
 	      prettyprint_time(p, dhcp_tmp->lease_time);
 	    }
 	  
-	  if (daemon->dhcp_buff)
-	    inet_ntop(family, start, daemon->dhcp_buff, 256);
-	  if (daemon->dhcp_buff3)
-	    inet_ntop(family, end, daemon->dhcp_buff3, 256);
+	  inet_ntop(family, start, daemon->dhcp_buff, 256);
+	  inet_ntop(family, end, daemon->dhcp_buff3, 256);
 	  if ((dhcp_tmp->flags & CONTEXT_DHCP) || family == AF_INET) 
 	    my_syslog(MS_DHCP | LOG_INFO, 
 		      (dhcp_tmp->flags & CONTEXT_RA_STATELESS) ? 
@@ -637,7 +668,7 @@ int main (int argc, char **argv)
 
 	  if (dhcp_tmp->flags & CONTEXT_RA_NAME)
 	    my_syslog(MS_DHCP | LOG_INFO, _("DHCPv4-derived IPv6 names on %s"), 
-		      daemon->addrbuff);
+		      daemon->dhcp_buff2);
 	  if (dhcp_tmp->flags & (CONTEXT_RA_ONLY | CONTEXT_RA_NAME | CONTEXT_RA_STATELESS))
 	    {
 	      if (!(dhcp_tmp->flags & CONTEXT_DEPRECATE))
@@ -647,7 +678,7 @@ int main (int argc, char **argv)
 		  prettyprint_time(p, dhcp_tmp->lease_time > 7200 ? dhcp_tmp->lease_time : 7200);
 		}
 	      my_syslog(MS_DHCP | LOG_INFO, _("SLAAC on %s %s"), 
-			daemon->addrbuff, daemon->namebuff);
+			daemon->dhcp_buff2, daemon->namebuff);
 	    }
 	}
       

src/dnsmasq.h

@@ -992,6 +992,7 @@ struct dhcp_lease *lease4_allocate(struct in_addr addr);
 struct dhcp_lease *lease6_allocate(struct in6_addr *addrp, int lease_type);
 struct dhcp_lease *lease6_find(unsigned char *clid, int clid_len, 
 			       int lease_type, int iaid, struct in6_addr *addr);
+void lease6_filter(int lease_type, int iaid, struct dhcp_context *context);
 struct dhcp_lease *lease6_find_by_addr(struct in6_addr *net, int prefix, u64 addr);
 u64 lease_find_max_addr6(struct dhcp_context *context);
 void lease_ping_reply(struct in6_addr *sender, unsigned char *packet, char *interface);

src/lease.c

@@ -562,18 +562,31 @@ struct dhcp_lease *lease6_find(unsigned char *clid, int clid_len,
 	   memcmp(clid, lease->clid, clid_len) != 0))
 	continue;
       
-      if (clid || addr)
-	{
-	  lease->flags |= LEASE_USED;
-	  return lease;
-	}
-      else 
-	lease->flags &= ~LEASE_USED;
+      lease->flags |= LEASE_USED;
+      return lease;
     }
   
   return NULL;
 }
 
+void lease6_filter(int lease_type, int iaid, struct dhcp_context *context)
+{
+  struct dhcp_lease *lease;
+  
+  for (lease = leases; lease; lease = lease->next)
+    {
+      /* reset "USED flag */
+      lease->flags &= ~LEASE_USED;
+      
+      if (!(lease->flags & lease_type) || lease->hwaddr_type != iaid)
+	continue;
+      
+      /* leases on the wrong interface get filtered out here */
+      if (!address6_available(context, (struct in6_addr *)&lease->hwaddr, NULL))
+	lease->flags |= LEASE_USED;
+    }
+}
+
 struct dhcp_lease *lease6_find_by_addr(struct in6_addr *net, int prefix, u64 addr)
 {
   struct dhcp_lease *lease;

src/rfc2131.c

@@ -493,8 +493,9 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 	      lease_set_interface(lease, int_index, now);
 	      
 	      clear_packet(mess, end);
+	      match_vendor_opts(NULL, daemon->dhcp_opts); /* clear flags */
 	      do_options(context, mess, end, NULL, hostname, get_domain(mess->yiaddr), 
-			 netid, subnet_addr, 0, 0, 0, NULL, 0, now);
+			 netid, subnet_addr, 0, 0, -1, NULL, 0, now);
 	    }
 	}
       
@@ -515,11 +516,22 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
       op += 3;
       pp = op;
       
-      /* Always force update, since the client has no way to do it itself. */
-      if (!option_bool(OPT_FQDN_UPDATE) && !(fqdn_flags & 0x01))
-	fqdn_flags |= 0x03;
-
-      fqdn_flags &= ~0x08;
+      /* NB, the following always sets at least one bit */
+      if (option_bool(OPT_FQDN_UPDATE))
+	{
+	  if (fqdn_flags & 0x01)
+	    {
+	      fqdn_flags |= 0x02; /* set O */
+	      fqdn_flags &= ~0x01; /* clear S */
+	    }
+	  fqdn_flags |= 0x08; /* set N */
+	}
+      else 
+	{
+	  if (!(fqdn_flags & 0x01))
+	    fqdn_flags |= 0x03; /* set S and O */
+	  fqdn_flags &= ~0x08; /* clear N */
+	}
       
       if (fqdn_flags & 0x04)
 	while (*op != 0 && ((op + (*op) + 1) - pp) < len)
@@ -2261,7 +2273,7 @@ static void do_options(struct dhcp_context *context,
 	  
 	  if ((p = free_space(mess, end, OPTION_CLIENT_FQDN, len)))
 	    {
-	      *(p++) = fqdn_flags;
+	      *(p++) = fqdn_flags & 0x0f; /* MBZ bits to zero */ 
 	      *(p++) = 255;
 	      *(p++) = 255;
 

src/rfc3315.c

@@ -497,7 +497,7 @@ static int dhcp6_no_relay(int msg_type, struct in6_addr *link_address, struct dh
 	    ia_option =  opt6_find(opt6_ptr(opt, ia_type == OPTION6_IA_NA ? 12 : 4), ia_end, OPTION6_IAADDR, 24);
 	    
 	    /* reset "USED" flags on leases */
-	    lease6_find(NULL, 0, ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, NULL);
+	    lease6_filter(ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, context);
 	    
 	    o = new_opt6(ia_type);
 	    put_opt6_long(iaid);
@@ -570,7 +570,12 @@ static int dhcp6_no_relay(int msg_type, struct in6_addr *link_address, struct dh
 			  my_syslog(MS_DHCP | LOG_WARNING, _("not using configured address %s because it was previously declined"), 
 				    daemon->addrbuff);
 			else
-			  addrp = &config->addr6;			 
+			  {
+			    addrp = &config->addr6;
+			    /* may have existing lease for this address */
+			    lease = lease6_find(clid, clid_len, 
+						ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, addrp); 
+			  }
 		      }
 		    
 		    /* existing lease */
@@ -832,7 +837,7 @@ static int dhcp6_no_relay(int msg_type, struct in6_addr *link_address, struct dh
 	    iacntr = save_counter(-1); 
 	    
 	    /* reset "USED" flags on leases */
-	    lease6_find(NULL, 0, ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, NULL);
+	    lease6_filter(ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, context);
 	    
 	    ia_option = opt6_ptr(opt, ia_type == OPTION6_IA_NA ? 12 : 4);
 	    ia_end = opt6_ptr(opt, opt6_len(opt));
@@ -1036,7 +1041,7 @@ static int dhcp6_no_relay(int msg_type, struct in6_addr *link_address, struct dh
 	    ia_option = opt6_ptr(opt, ia_type == OPTION6_IA_NA ? 12 : 4);
 	    
 	    /* reset "USED" flags on leases */
-	    lease6_find(NULL, 0, ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, NULL);
+	    lease6_filter(ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, context);
 		
 	    for (ia_option = opt6_find(ia_option, ia_end, OPTION6_IAADDR, 24);
 		 ia_option;
@@ -1115,7 +1120,7 @@ static int dhcp6_no_relay(int msg_type, struct in6_addr *link_address, struct dh
 	    ia_option = opt6_ptr(opt, ia_type == OPTION6_IA_NA ? 12 : 4);
 	    
 	    /* reset "USED" flags on leases */
-	    lease6_find(NULL, 0, ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, NULL);
+	    lease6_filter(ia_type == OPTION6_IA_NA ? LEASE_NA : LEASE_TA, iaid, context);
 		
 	    for (ia_option = opt6_find(ia_option, ia_end, OPTION6_IAADDR, 24);
 		 ia_option;