Merge branch 'vendor/FILE'
[dragonfly.git] / contrib / tcp_wrappers / fix_options.c
CommitLineData
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1 /*
2 * Routine to disable IP-level socket options. This code was taken from 4.4BSD
3 * rlogind and kernel source, but all mistakes in it are my fault.
4 *
5 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
6 *
7 * $FreeBSD: src/contrib/tcp_wrappers/fix_options.c,v 1.2 2000/02/03 10:26:57 shin Exp $
1de703da 8 * $DragonFly: src/contrib/tcp_wrappers/fix_options.c,v 1.2 2003/06/17 04:24:06 dillon Exp $
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9 */
10
11#ifndef lint
12static char sccsid[] = "@(#) fix_options.c 1.6 97/04/08 02:29:19";
13#endif
14
15#include <sys/types.h>
16#include <sys/param.h>
17#ifdef INET6
18#include <sys/socket.h>
19#endif
20#include <netinet/in.h>
21#include <netinet/in_systm.h>
22#include <netinet/ip.h>
23#include <netdb.h>
24#include <stdio.h>
25#include <syslog.h>
26
27#ifndef IPOPT_OPTVAL
28#define IPOPT_OPTVAL 0
29#define IPOPT_OLEN 1
30#endif
31
32#include "tcpd.h"
33
34#define BUFFER_SIZE 512 /* Was: BUFSIZ */
35
36/* fix_options - get rid of IP-level socket options */
37
4051520f 38void
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39fix_options(request)
40struct request_info *request;
41{
42#ifdef IP_OPTIONS
43 unsigned char optbuf[BUFFER_SIZE / 3], *cp;
44 char lbuf[BUFFER_SIZE], *lp;
45 int optsize = sizeof(optbuf), ipproto;
46 struct protoent *ip;
47 int fd = request->fd;
48 unsigned int opt;
49 int optlen;
50 struct in_addr dummy;
51#ifdef INET6
52 struct sockaddr_storage ss;
53 int sslen;
54
55 /*
56 * check if this is AF_INET socket
57 * XXX IPv6 support?
58 */
59 sslen = sizeof(ss);
60 if (getsockname(fd, (struct sockaddr *)&ss, &sslen) < 0) {
61 syslog(LOG_ERR, "getpeername: %m");
62 clean_exit(request);
63 }
64 if (ss.ss_family != AF_INET)
65 return;
66#endif
67
68 if ((ip = getprotobyname("ip")) != 0)
69 ipproto = ip->p_proto;
70 else
71 ipproto = IPPROTO_IP;
72
73 if (getsockopt(fd, ipproto, IP_OPTIONS, (char *) optbuf, &optsize) == 0
74 && optsize != 0) {
75
76 /*
77 * Horror! 4.[34] BSD getsockopt() prepends the first-hop destination
78 * address to the result IP options list when source routing options
79 * are present (see <netinet/ip_var.h>), but produces no output for
80 * other IP options. Solaris 2.x getsockopt() does produce output for
81 * non-routing IP options, and uses the same format as BSD even when
82 * the space for the destination address is unused. The code below
83 * does the right thing with 4.[34]BSD derivatives and Solaris 2, but
84 * may occasionally miss source routing options on incompatible
85 * systems such as Linux. Their choice.
86 *
87 * Look for source routing options. Drop the connection when one is
88 * found. Just wiping the IP options is insufficient: we would still
89 * help the attacker by providing a real TCP sequence number, and the
90 * attacker would still be able to send packets (blind spoofing). I
91 * discussed this attack with Niels Provos, half a year before the
92 * attack was described in open mailing lists.
93 *
94 * It would be cleaner to just return a yes/no reply and let the caller
95 * decide how to deal with it. Resident servers should not terminate.
96 * However I am not prepared to make changes to internal interfaces
97 * on short notice.
98 */
99#define ADDR_LEN sizeof(dummy.s_addr)
100
101 for (cp = optbuf + ADDR_LEN; cp < optbuf + optsize; cp += optlen) {
102 opt = cp[IPOPT_OPTVAL];
103 if (opt == IPOPT_LSRR || opt == IPOPT_SSRR) {
104 syslog(LOG_WARNING,
105 "refused connect from %s with IP source routing options",
106 eval_client(request));
107 shutdown(fd, 2);
108 return;
109 }
110 if (opt == IPOPT_EOL)
111 break;
112 if (opt == IPOPT_NOP) {
113 optlen = 1;
114 } else {
115 optlen = cp[IPOPT_OLEN];
116 if (optlen <= 0) /* Do not loop! */
117 break;
118 }
119 }
120 lp = lbuf;
121 for (cp = optbuf; optsize > 0; cp++, optsize--, lp += 3)
122 sprintf(lp, " %2.2x", *cp);
123 syslog(LOG_NOTICE,
124 "connect from %s with IP options (ignored):%s",
125 eval_client(request), lbuf);
126 if (setsockopt(fd, ipproto, IP_OPTIONS, (char *) 0, optsize) != 0) {
127 syslog(LOG_ERR, "setsockopt IP_OPTIONS NULL: %m");
128 shutdown(fd, 2);
129 }
130 }
131#endif
132}