2df75d71d1
Now when tcp_wrapper is enabled by inetd -wW,
several accesses which should be permitted are refused only for IPv6,
if hostname is used to decide the host to be allowed.
IPv6 users will be just upset.
About security related concern.
-All extensions are wrapped by #ifdef INET6, so people can completely
disable the extension by recompile libwrap without INET6 option.
-Access via IPv6 is not enabled by default.
People need to enable IPv6 access by changing /etc/inetd.conf at first,
by adding tcp6 and/or tcp46 entries.
-The base of patches are from KAME package and are actually daily used
for more than a year in several Japanese IPv6 environments.
-Patches are reviewed by markm.
Approved by: jkh
Submitted by: Hajimu UMEMOTO <ume@mahoroba.org>
Reviewed by: markm
Obtained from: KAME project
131 lines
3.7 KiB
C
131 lines
3.7 KiB
C
/*
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* Routine to disable IP-level socket options. This code was taken from 4.4BSD
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* rlogind and kernel source, but all mistakes in it are my fault.
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*
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* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
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*
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* $FreeBSD$
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*/
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#ifndef lint
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static char sccsid[] = "@(#) fix_options.c 1.6 97/04/08 02:29:19";
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#endif
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#include <sys/types.h>
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#include <sys/param.h>
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#ifdef INET6
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#include <sys/socket.h>
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#endif
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#include <netinet/in.h>
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#include <netinet/in_systm.h>
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#include <netinet/ip.h>
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#include <netdb.h>
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#include <stdio.h>
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#include <syslog.h>
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#ifndef IPOPT_OPTVAL
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#define IPOPT_OPTVAL 0
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#define IPOPT_OLEN 1
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#endif
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#include "tcpd.h"
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#define BUFFER_SIZE 512 /* Was: BUFSIZ */
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/* fix_options - get rid of IP-level socket options */
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fix_options(request)
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struct request_info *request;
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{
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#ifdef IP_OPTIONS
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unsigned char optbuf[BUFFER_SIZE / 3], *cp;
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char lbuf[BUFFER_SIZE], *lp;
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int optsize = sizeof(optbuf), ipproto;
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struct protoent *ip;
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int fd = request->fd;
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unsigned int opt;
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int optlen;
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struct in_addr dummy;
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#ifdef INET6
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struct sockaddr_storage ss;
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int sslen;
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/*
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* check if this is AF_INET socket
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* XXX IPv6 support?
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*/
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sslen = sizeof(ss);
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if (getsockname(fd, (struct sockaddr *)&ss, &sslen) < 0) {
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syslog(LOG_ERR, "getpeername: %m");
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clean_exit(request);
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}
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if (ss.ss_family != AF_INET)
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return;
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#endif
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if ((ip = getprotobyname("ip")) != 0)
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ipproto = ip->p_proto;
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else
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ipproto = IPPROTO_IP;
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if (getsockopt(fd, ipproto, IP_OPTIONS, (char *) optbuf, &optsize) == 0
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&& optsize != 0) {
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/*
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* Horror! 4.[34] BSD getsockopt() prepends the first-hop destination
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* address to the result IP options list when source routing options
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* are present (see <netinet/ip_var.h>), but produces no output for
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* other IP options. Solaris 2.x getsockopt() does produce output for
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* non-routing IP options, and uses the same format as BSD even when
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* the space for the destination address is unused. The code below
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* does the right thing with 4.[34]BSD derivatives and Solaris 2, but
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* may occasionally miss source routing options on incompatible
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* systems such as Linux. Their choice.
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*
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* Look for source routing options. Drop the connection when one is
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* found. Just wiping the IP options is insufficient: we would still
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* help the attacker by providing a real TCP sequence number, and the
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* attacker would still be able to send packets (blind spoofing). I
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* discussed this attack with Niels Provos, half a year before the
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* attack was described in open mailing lists.
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*
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* It would be cleaner to just return a yes/no reply and let the caller
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* decide how to deal with it. Resident servers should not terminate.
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* However I am not prepared to make changes to internal interfaces
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* on short notice.
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*/
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#define ADDR_LEN sizeof(dummy.s_addr)
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for (cp = optbuf + ADDR_LEN; cp < optbuf + optsize; cp += optlen) {
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opt = cp[IPOPT_OPTVAL];
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if (opt == IPOPT_LSRR || opt == IPOPT_SSRR) {
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syslog(LOG_WARNING,
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"refused connect from %s with IP source routing options",
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eval_client(request));
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shutdown(fd, 2);
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return;
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}
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if (opt == IPOPT_EOL)
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break;
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if (opt == IPOPT_NOP) {
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optlen = 1;
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} else {
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optlen = cp[IPOPT_OLEN];
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if (optlen <= 0) /* Do not loop! */
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break;
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}
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}
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lp = lbuf;
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for (cp = optbuf; optsize > 0; cp++, optsize--, lp += 3)
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sprintf(lp, " %2.2x", *cp);
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syslog(LOG_NOTICE,
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"connect from %s with IP options (ignored):%s",
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eval_client(request), lbuf);
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if (setsockopt(fd, ipproto, IP_OPTIONS, (char *) 0, optsize) != 0) {
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syslog(LOG_ERR, "setsockopt IP_OPTIONS NULL: %m");
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shutdown(fd, 2);
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}
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}
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#endif
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}
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