Add real securenets support. By default, ypserv now uses /var/yp/securenets

in the same was as the SunOS ypserv (same format, described in ypserv man
page). If the user wants tcpwrapper style access control, they can
recompile ypserv to use that instead. This way we get securenets without
having to ship libwrap.a and tcpd.h with core FreeBSD distribution.

If /var/yp/securenets doesn't exist, ypserv allows all connections.

5 files changed, 228 insertions, 39 deletions

diff --git a/usr.sbin/ypserv/yp_access.c b/usr.sbin/ypserv/yp_access.c
index cdd69ef..7efb880 100644
--- a/usr.sbin/ypserv/yp_access.c
+++ b/usr.sbin/ypserv/yp_access.c
@@ -32,18 +32,25 @@
  */
 
 #include <rpc/rpc.h>
+#include <rpcsvc/yp.h>
+#include <rpcsvc/yppasswd.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <sys/stat.h>
 #include <paths.h>
+#include <errno.h>
 #include <sys/param.h>
 #include "yp_extern.h"
 #ifdef TCP_WRAPPER
 #include "tcpd.h"
 #endif
 
+#ifndef lint
+static const char rcsid[] = "$Id$";
+#endif
+
 extern int debug;
 
 char *yp_procs[] = {	"ypproc_null" ,
@@ -60,6 +67,99 @@ char *yp_procs[] = {	"ypproc_null" ,
 			"ypproc_maplist"
 		   };
 
+#ifdef TCP_WRAPPER
+void load_securenets()
+{
+}
+#else
+struct securenet {
+	struct in_addr net;
+	struct in_addr mask;
+	struct securenet *next;
+};
+
+struct securenet *securenets;
+
+#define LINEBUFSZ 1024
+
+/*
+ * Read /var/yp/securenets file and initialize the securenets
+ * list. If the file doesn't exist, we set up a dummy entry that
+ * allows all hosts to connect.
+ */
+void load_securenets()
+{
+	FILE *fp;
+	char path[MAXPATHLEN + 2];
+	char linebuf[1024 + 2];
+	struct securenet *tmp;
+
+	/*
+	 * If securenets is not NULL, we are being called to reload
+	 * the list; free the existing list before re-reading the
+	 * securenets file.
+	 */
+	if (securenets != NULL) {
+		while(securenets) {
+			tmp = securenets->next;
+			free(securenets->net);
+			free(securenets->mask);
+			free(securenets);
+			securenets = tmp;
+		}
+	}
+
+	snprintf(path, MAXPATHLEN, "%s/securenets", yp_dir);
+
+	if ((fp = fopen(path, "r")) == NULL) {
+		if (errno == ENOENT) {
+			securenets = (struct securenet *)malloc(sizeof(struct securenet));
+			securenets->net.s_addr = INADDR_ANY;
+			securenets->mask.s_addr = INADDR_BROADCAST;
+			securenets->next = NULL;
+			return;
+		} else {
+			yp_error("fopen(%s) failed: %s", path, strerror(errno));
+			exit(1);
+		}
+	}
+
+	securenets = NULL;
+
+	while(fgets(linebuf, LINEBUFSZ, fp)) {
+		char addr1[20], addr2[20];
+
+		if (linebuf[0] == '#')
+			continue;
+		if (sscanf(linebuf, "%s %s", addr1, addr2) < 2) {
+			yp_error("badly formatted securenets entry: %s",
+							linebuf);
+			continue;
+		}
+
+		tmp = (struct securenet *)malloc(sizeof(struct securenet));
+
+		if (!inet_aton((char *)&addr1, (struct in_addr *)&tmp->net)) {
+			yp_error("badly formatted securenets entry: %s", addr1);
+			free(tmp);
+			continue;
+		}
+
+		if (!inet_aton((char *)&addr2, (struct in_addr *)&tmp->mask)) {
+			yp_error("badly formatted securenets entry: %s", addr2);
+			free(tmp);
+			continue;
+		}
+
+		tmp->next = securenets;
+		securenets = tmp;
+	}
+
+	fclose(fp);
+	
+}
+#endif
+
 /*
  * Access control functions.
  *
@@ -71,10 +171,19 @@ char *yp_procs[] = {	"ypproc_null" ,
  *   assume that the caller is root and allow the RPC to succeed. If it
  *   isn't access is denied.
  *
- * - If we are compiled with the tcpwrapper package, we also check to see
- *   if the host makes it past the libwrap checks and deny access if it
- *   doesn't. Host address checks are disabled if not compiled with the
- *   tcp_wrapper package.
+ * - The client's IP address is checked against the securenets rules.
+ *   There are two kinds of securenets support: the built-in support,
+ *   which is very simple and depends on the presense of a
+ *   /var/yp/securenets file, and tcp-wrapper support, which requires
+ *   Wietse Venema's libwrap.a and tcpd.h. (Since the tcp-wrapper
+ *   package does not ship with FreeBSD, we use the built-in support
+ *   by default. Users can recompile the server the tcp-wrapper library
+ *   if they already have it installed and want to use hosts.allow and
+ *   hosts.deny to control access instead od having a seperate securenets
+ *   file.)
+ *
+ *   If no /var/yp/securenets file is present, the host access checks
+ *   are bypassed and all hosts are allowed to connect.
  *
  * The yp_validdomain() functions checks the domain specified by the caller
  * to make sure it's actually served by this server. This is more a sanity
@@ -87,15 +196,19 @@ int yp_access(map, rqstp)
 	const struct svc_req *rqstp;
 {
 	struct sockaddr_in *rqhost;
-#ifdef TCP_WRAPPER
 	int status = 0;
 	unsigned long oldaddr;
+#ifndef TCP_WRAPPER
+	struct securenet *tmp;
 #endif
 
 	rqhost = svc_getcaller(rqstp->rq_xprt);
 
 	if (debug) {
 		yp_error("Procedure %s called from %s:%d",
+			/* Hack to allow rpc.yppasswdd to use this routine */
+			rqstp->rq_prog == YPPASSWDPROG ?
+			"yppasswdproc_update" :
 			yp_procs[rqstp->rq_proc], inet_ntoa(rqhost->sin_addr),
 			ntohs(rqhost->sin_port));
 		if (map != NULL)
@@ -104,24 +217,41 @@ int yp_access(map, rqstp)
 
 	/* Check the map name if one was supplied. */
 	if (map != NULL) {
-		if (strstr(map, "master.passwd.") && ntohs(rqhost->sin_port) > 1023) {
+		if ((strstr(map, "master.passwd.") ||
+		    rqstp->rq_proc == YPPROC_XFR) &&
+		    ntohs(rqhost->sin_port) > 1023) {
 			yp_error("Access to %s denied -- client not privileged", map);
 			return(1);
 		}
 	}
 
 #ifdef TCP_WRAPPER
-	/* Check client address if TCP_WRAPPER is enalbled. */
 	status = hosts_ctl(progname, STRING_UNKNOWN,
-			   inet_ntoa(rqhost->sin_addr, "");
+			   inet_ntoa(rqhost->sin_addr), "");
+#else
+	tmp = securenets;
+	while(tmp) {
+		if (((rqhost->sin_addr.s_addr & ~tmp->mask.s_addr)
+		    | tmp->net.s_addr) == rqhost->sin_addr.s_addr) {
+			status = 1;
+			break;
+		}
+		tmp = tmp->next;
+	}
+#endif
 
-	if (!status && rqhost->sin_addr.s_addr != oldaddr) {
-		yp_error("connect from %s:%d refused",
-			  inet_ntoa(rqhost->sin_addr), ntohs(rqhost->sin_port));
-		oldaddr = rqhost->sin_addr.s_addr;
+	if (!status) {
+		if (rqhost->sin_addr.s_addr != oldaddr) {
+			yp_error("connect from %s:%d to procedure %s refused",
+					inet_ntoa(rqhost->sin_addr),
+					ntohs(rqhost->sin_port),
+					rqstp->rq_prog == YPPASSWDPROG ?
+					"yppasswdproc_update" :
+					yp_procs[rqstp->rq_proc]);
+			oldaddr = rqhost->sin_addr.s_addr;
+		}
 		return(1);
 	}
-#endif
 	return(0);
 
 }
@@ -134,7 +264,7 @@ int yp_validdomain(domain)
 
 	if (domain == NULL || strstr(domain, "binding") ||
 	    !strcmp(domain, ".") || !strcmp(domain, "..") ||
-	    strchr(domain, '/'))
+	    strchr(domain, '/') || strlen(domain) > YPMAXDOMAIN)
 		return(1);
 
 	snprintf(dompath, sizeof(dompath), "%s/%s", yp_dir, domain);
diff --git a/usr.sbin/ypserv/yp_extern.h b/usr.sbin/ypserv/yp_extern.h
index e94d253..9e5a39f 100644
--- a/usr.sbin/ypserv/yp_extern.h
+++ b/usr.sbin/ypserv/yp_extern.h
@@ -29,7 +29,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: yp_extern.h,v 1.1.1.1 1995/12/16 20:54:17 wpaul Exp $
+ *	$Id: yp_extern.h,v 1.2 1995/12/23 21:35:30 wpaul Exp $
  */
 #include <stdio.h>
 #include <string.h>
@@ -72,3 +72,4 @@ extern char	*yp_dnsaddr __P(( const char * ));
 extern int	yp_access __P((const char *, const struct svc_req * ));
 extern int	yp_validdomain __P((const char * ));
 extern DB	*yp_open_db __P(( const char *, const char *));
+extern void	load_securenets __P(( void ));
diff --git a/usr.sbin/ypserv/yp_main.c b/usr.sbin/ypserv/yp_main.c
index 94956b7..17296dc 100644
--- a/usr.sbin/ypserv/yp_main.c
+++ b/usr.sbin/ypserv/yp_main.c
@@ -29,7 +29,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: yp_main.c,v 1.1.1.1 1995/12/16 20:54:17 wpaul Exp $
+ *	$Id: yp_main.c,v 1.2 1995/12/23 21:35:32 wpaul Exp $
  */
 
 /*
@@ -65,7 +65,7 @@
 
 #define	_RPCSVC_CLOSEDOWN 120
 #ifndef lint
-static char rcsid[] = "$Id: yp_main.c,v 1.1.1.1 1995/12/16 20:54:17 wpaul Exp $";
+static char rcsid[] = "$Id: yp_main.c,v 1.2 1995/12/23 21:35:32 wpaul Exp $";
 #endif /* not lint */
 int _rpcpmstart;		/* Started by a port monitor ? */
 static int _rpcfdtype;
@@ -147,6 +147,11 @@ static void reaper(sig)
 {
 	int status;
 
+	if (sig == SIGHUP) {
+		load_securenets();
+		return;
+	}
+
 	if (sig == SIGCHLD) {
 		while (wait3(&status, WNOHANG, NULL) > 0)
 			children--;
@@ -223,6 +228,8 @@ main(argc, argv)
 		}
 	}
 
+	load_securenets();
+
 	if (getsockname(0, (struct sockaddr *)&saddr, &asize) == 0) {
 		int ssize = sizeof (int);
 
diff --git a/usr.sbin/ypserv/yp_server.c b/usr.sbin/ypserv/yp_server.c
index 3ac7e2e..dfe6eef 100644
--- a/usr.sbin/ypserv/yp_server.c
+++ b/usr.sbin/ypserv/yp_server.c
@@ -45,7 +45,7 @@
 #include <rpc/rpc.h>
 
 #ifndef lint
-static char rcsid[] = "$Id: yp_server.c,v 1.3 1996/01/10 16:07:39 wpaul Exp $";
+static char rcsid[] = "$Id: yp_server.c,v 1.2 1995/12/23 21:35:35 wpaul Exp $";
 #endif /* not lint */
 
 int forked = 0;
@@ -408,6 +408,9 @@ ypproc_clear_2_svc(void *argp, struct svc_req *rqstp)
 	if (yp_access(NULL, (struct svc_req *)rqstp))
 		return (NULL);
 
+	/* Re-read the securenets database for the hell of it. */
+	load_securenets();
+
 	result = &rval;
 	return((void *) &result);
 }
diff --git a/usr.sbin/ypserv/ypserv.8 b/usr.sbin/ypserv/ypserv.8
index 953eea5..e878d2b 100644
--- a/usr.sbin/ypserv/ypserv.8
+++ b/usr.sbin/ypserv/ypserv.8
@@ -28,7 +28,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"	$Id: ypserv.8,v 1.2 1996/01/30 13:52:50 mpp Exp $
+.\"	$Id: ypserv.8,v 1.1.1.1 1995/12/16 20:54:17 wpaul Exp $
 .\"
 .Dd February 4, 1995
 .Dt YPSERV 8
@@ -68,7 +68,7 @@ using the
 command. The clients must also run
 .Xr ypbind 8
 in order to attach to a particular server, since it is possible to
-have several servers within a single NIS domain.
+have serveral servers within a single NIS domain.
 .Pp
 The databases distributed by
 .Nm ypserv
@@ -114,7 +114,7 @@ To make up for this, the FreeBSD version of
 handles the
 .Pa master.passwd.byname
 and
-.Pa master.passwd.byuid
+.Pa master.basswd.byuid
 maps in a special way. When the server receives a request to access
 either of these two maps, it will check the TCP port from which the
 request originated and return an error if the port number is greater
@@ -125,7 +125,7 @@ Any requests made by non-privileged users are therefore rejected.
 .Pp
 Furthermore, the
 .Xr getpwent 3
-routines in FreeBSD's standard C library will only attempt to retrieve
+routines in FreeBSD's standard C libarary will only attempt to retrieve
 data from the
 .Pa master.passwd.byname
 and
@@ -167,15 +167,58 @@ This will cause the standard
 and
 .Pa passwd.byuid
 maps to be generated with valid encrypted password fields, which is
-necessary in order for non-FreeBSD clients to perform user
+neccesary in order for non-FreeBSD clients to perform user
 authentication through NIS.
 .El
 .Pp
 .Ss Security
+In general, any remote user can issue an RPC to
+.Nm ypserv
+and retrieve the contents of your NIS maps, provided the remote user
+knows your domain name. To prevent such unauthorized transactions,
+.Nm ypserv
+supports a feature called
+.Pa securenets
+which can be used to restrict access to a given set of hosts.
+At startup,
+.Nm ypserv
+will attempt to load the securenets information from a file
+called
+.Nm /var/yp/securenets .
+(Note that this path varies depending on the path specified with
+the
+.Fl p
+option, which is explained below.) This file contains entries
+that consist of a network specification and a network mask separated
+by white space.
+Lines starting with ``#'' are considered to be comments. A
+sample securenets file might look like this:
+.Bd -unfilled -offset indent
+# allow connections from local host -- mandatory
+127.0.0.1     255.255.255.255
+# allow connections from any host
+# on the 129.168.128.0 network
+192.168.128.0 255.255.255.0
+# allow connections from any host
+# between 10.0.0.0 to 10.0.15.255
+10.0.0.0      255.255.240.0
+.Ed
+.Pp
+If
+.Nm ypserv
+receives a request from an address that matches one of these rules,
+it will process the request normally. If the address fails to match
+a rule, the request will be ignored and a warning message will be
+logged. If the
+.Pa /var/yp/securenets
+file does not exist,
 .Nm ypserv
-has support for Wietse Venema's
+will allow connections from any host.
+.Pp
+.Nm Ypserv
+also has support for Wietse Venema's
 .Pa tcpwrapper
-package built in, though it is not compiled in by default since
+package, though it is not compiled in by default since
 the
 .Pa tcpwrapper
 package is not distributed with FreeBSD. However, if you have
@@ -184,14 +227,17 @@ and
 .Nm tcpd.h ,
 you can easily recompile
 .Nm ypserv
-with them, thereby enabling its 'securenets' features: you can
-configure
-.Nm ypserv
-to only handle requests from machines listed
-in the
-.Pa tcpwrapper
-configuration files, which would help limit vulnerability to the
-first limitation listed above.
+with them. This allows the administrator to use the tcpwrapper
+configuration files (
+.Pa /etc/hosts.allow
+and
+.Pa /etc/hosts.deny )
+for access control instead of
+.Pa /var/yp/securenets .
+.Pp
+Note: while both of these access control mechanisms provide some
+security, they, like the privileged port test, are both vulnerable
+to ``IP spoofing'' attacks.
 .Pp
 .Ss NIS servers that are also NIS clients
 Care must be taken when running
@@ -236,7 +282,7 @@ will construct a fake database record and return it to the client,
 thereby making it seem as though the client's yp_match request
 succeeded.
 .Pp
-This feature is provided for compatibility with SunOS 4.1.x,
+This feature is provided for compatiblity with SunOS 4.1.x,
 which has brain-damaged resolver functions in its standard C
 library that depend on NIS for hostname and address resolution.
 FreeBSD's resolver can be configured to do DNS
@@ -250,7 +296,7 @@ using the
 .Xr syslog 3
 facility. In debug mode, the server does not background
 itself and prints extra status messages to stderr for each
-request that it receives. Also, while running in debug mode,
+request that it revceives. Also, while running in debug mode,
 .Nm ypserv
 will not spawn any additional subprocesses as it normally does
 when handling yp_all requests or doing DNS lookups. (These actions
@@ -289,15 +335,17 @@ within the filesystem.
 The NIS maps.
 .It Pa /etc/host.conf
 Resolver configuration file.
+.It Pa /var/yp/securenets
+Host access control file
 .El
 .Sh SEE ALSO
-.Xr ypcat 1 ,
-.Xr db 3 ,
-.Xr yp 4 ,
 .Xr ypbind 8 ,
 .Xr yppasswdd 8 ,
 .Xr yppush 8 ,
-.Xr ypxfr 8
+.Xr ypxfr 8 ,
+.Xr ypcat 1 ,
+.Xr yp 8 ,
+.Xr db 3
 .Sh AUTHOR
 Bill Paul <wpaul@ctr.columbia.edu>
 .Sh HISTORY