Imported from /home/lorry/working-area/delta_tcp-wrappers/tcp_wrappers_7.6.tar.gz.HEADtcp_wrappers_7.6master

1 files changed, 109 insertions, 0 deletions

diff --git a/fix_options.c b/fix_options.c
new file mode 100644
index 0000000..b5e81b8
--- /dev/null
+++ b/fix_options.c
@@ -0,0 +1,109 @@
+ /*
+  * Routine to disable IP-level socket options. This code was taken from 4.4BSD
+  * rlogind and kernel source, but all mistakes in it are my fault.
+  *
+  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
+  */
+
+#ifndef lint
+static char sccsid[] = "@(#) fix_options.c 1.6 97/04/08 02:29:19";
+#endif
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <netinet/in.h>
+#include <netinet/in_systm.h>
+#include <netinet/ip.h>
+#include <netdb.h>
+#include <stdio.h>
+#include <syslog.h>
+
+#ifndef IPOPT_OPTVAL
+#define IPOPT_OPTVAL	0
+#define IPOPT_OLEN	1
+#endif
+
+#include "tcpd.h"
+
+#define BUFFER_SIZE	512		/* Was: BUFSIZ */
+
+/* fix_options - get rid of IP-level socket options */
+
+fix_options(request)
+struct request_info *request;
+{
+#ifdef IP_OPTIONS
+    unsigned char optbuf[BUFFER_SIZE / 3], *cp;
+    char    lbuf[BUFFER_SIZE], *lp;
+    int     optsize = sizeof(optbuf), ipproto;
+    struct protoent *ip;
+    int     fd = request->fd;
+    unsigned int opt;
+    int     optlen;
+    struct in_addr dummy;
+
+    if ((ip = getprotobyname("ip")) != 0)
+	ipproto = ip->p_proto;
+    else
+	ipproto = IPPROTO_IP;
+
+    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. 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.
+	 * 
+	 * 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.
+	 */
+#define ADDR_LEN sizeof(dummy.s_addr)
+
+	for (cp = optbuf + ADDR_LEN; 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));
+		shutdown(fd, 2);
+		return;
+	    }
+	    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);
+	syslog(LOG_NOTICE,
+	       "connect from %s with IP options (ignored):%s",
+	       eval_client(request), lbuf);
+	if (setsockopt(fd, ipproto, IP_OPTIONS, (char *) 0, optsize) != 0) {
+	    syslog(LOG_ERR, "setsockopt IP_OPTIONS NULL: %m");
+	    shutdown(fd, 2);
+	}
+    }
+#endif
+}