From: deraadt <deraadt@openbsd.org>
Date: Fri, 4 Apr 1997 09:06:28 +0000 (+0000)
Subject: do source routing check correctly; this could use a test
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=a398bd1ff9e229d0e5860a4fe0eb8a2a0e07f28f;p=openbsd

do source routing check correctly; this could use a test
---

diff --git a/lib/libwrap/fix_options.c b/lib/libwrap/fix_options.c
index 619f1469952..48e95972de4 100644
--- a/lib/libwrap/fix_options.c
+++ b/lib/libwrap/fix_options.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: fix_options.c,v 1.1 1997/02/26 03:06:51 downsj Exp $	*/
+/*	$OpenBSD: fix_options.c,v 1.2 1997/04/04 09:06:28 deraadt Exp $	*/
 
  /*
   * Routine to disable IP-level socket options. This code was taken from 4.4BSD
@@ -11,7 +11,7 @@
 #if 0
 static char sccsid[] = "@(#) fix_options.c 1.4 97/02/12 02:13:22";
 #else
-static char rcsid[] = "$OpenBSD: fix_options.c,v 1.1 1997/02/26 03:06:51 downsj Exp $";
+static char rcsid[] = "$OpenBSD: fix_options.c,v 1.2 1997/04/04 09:06:28 deraadt Exp $";
 #endif
 #endif
 
@@ -20,6 +20,7 @@ static char rcsid[] = "$OpenBSD: fix_options.c,v 1.1 1997/02/26 03:06:51 downsj
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
+#include <netinet/ip_var.h>
 #include <netinet/ip.h>
 #include <netdb.h>
 #include <stdio.h>
@@ -41,85 +42,44 @@ fix_options(request)
 struct request_info *request;
 {
 #ifdef IP_OPTIONS
-    unsigned char optbuf[BUFFER_SIZE / 3], *cp;
-    char    lbuf[BUFFER_SIZE], *lp;
+    struct ipoption optbuf;
+    char    lbuf[BUFFER_SIZE], *lp, *cp;
     int     optsize = sizeof(optbuf), ipproto;
     struct protoent *ip;
     int     fd = request->fd;
     unsigned int opt;
-    int     optlen;
-    unsigned char *first_option = optbuf;
+    int     optlen, i;
 
     if ((ip = getprotobyname("ip")) != 0)
 	ipproto = ip->p_proto;
     else
 	ipproto = IPPROTO_IP;
 
-    if (getsockopt(fd, ipproto, IP_OPTIONS, (char *) optbuf, &optsize) == 0
+    if (getsockopt(fd, ipproto, IP_OPTIONS, (char *) &optbuf, &optsize) == 0
 	&& optsize != 0) {
 
 	/*
-	 * Horror! 4.[34] BSD getsockopt() prepends the first-hop destination
-	 * address to the result IP options list when source routing options
-	 * are present (see <netinet/ip_var.h>), but produces no output for
-	 * other IP options. Solaris 2.x getsockopt() does produce output for
-	 * non-routing IP options, and uses the same format as BSD even when
-	 * the space for the destination address is unused. However, we must
-	 * be prepared to deal with systems that return the options only. The
-	 * code below does the right thing with 4.[34]BSD derivatives and
-	 * Solaris 2, but may occasionally miss source routing options on
-	 * incompatible systems such as Linux. Their choice.
+	 * Properly deal with source routing entries.  The original code
+	 * here was wrong.
 	 */
-#define ADDR_LEN sizeof(struct in_addr)
-
-	for (cp = optbuf + ADDR_LEN; cp < optbuf + optsize; cp++) {
-	    opt = cp[IPOPT_OPTVAL];
-	    if (opt != IPOPT_NOP) {
-		if (opt == IPOPT_RR
-		    || opt == IPOPT_TS
-		    || opt == IPOPT_SECURITY
-		    || opt == IPOPT_LSRR
-		    || opt == IPOPT_SATID
-		    || opt == IPOPT_SSRR)
-		    first_option = cp;
-		break;
-	    }
+	for (i = 0; (void *)&optbuf.ipopt_list[i] - (void *)&optbuf <
+	    optsize; ) {
+		u_char c = (u_char)optbuf.ipopt_list[i];
+		if (c == IPOPT_LSRR || c == IPOPT_SSRR) {
+			syslog(LOG_WARNING,
+			   "refused connect from %s with IP source routing options",
+			       eval_client(request));
+			clean_exit(request);
+		}
+		if (c == IPOPT_EOL)
+			break;
+		i += (c == IPOPT_NOP) ? 1 : (u_char)optbuf.ipopt_list[i+1];
 	}
 
-	/*
-	 * Look for source routing options. Drop the connection when one is
-	 * found. Just wiping the IP options is insufficient: we would still
-	 * help the attacker by providing a real TCP sequence number, and the
-	 * attacker would still be able to send packets (blind spoofing). I
-	 * discussed this attack with Niels Provos, half a year before the
-	 * attack was described in open mailing lists.
-	 * 
-	 * It would be cleaner to just return a yes/no reply and let the caller
-	 * decide how to deal with it. Resident servers should not terminate.
-	 * However I am not prepared to make changes to internal interfaces
-	 * on short notice.
-	 */
-	for (cp = first_option; cp < optbuf + optsize; cp += optlen) {
-	    opt = cp[IPOPT_OPTVAL];
-	    if (opt == IPOPT_LSRR || opt == IPOPT_SSRR) {
-		syslog(LOG_WARNING,
-		   "refused connect from %s with IP source routing options",
-		       eval_client(request));
-		clean_exit(request);
-	    }
-	    if (opt == IPOPT_EOL)
-		break;
-	    if (opt == IPOPT_NOP) {
-		optlen = 1;
-	    } else {
-		optlen = cp[IPOPT_OLEN];
-		if (optlen <= 0)		/* Do not loop! */
-		    break;
-	    }
-	}
 	lp = lbuf;
-	for (cp = optbuf; optsize > 0; cp++, optsize--, lp += 3)
-	    sprintf(lp, " %2.2x", *cp);
+	for (cp = (char *)&optbuf; optsize > 0 && lp < &lbuf[sizeof lbuf-1];
+	    cp++, optsize--, lp += 3)
+		sprintf(lp, " %2.2x", *cp);
 	syslog(LOG_NOTICE,
 	       "connect from %s with IP options (ignored):%s",
 	       eval_client(request), lbuf);