110 lines
3.3 KiB
C
110 lines
3.3 KiB
C
|
/*
|
||
|
|
* 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
|
||
|
|
}
|