fix_options.c revision 56977
144743Smarkm /* 244743Smarkm * Routine to disable IP-level socket options. This code was taken from 4.4BSD 344743Smarkm * rlogind and kernel source, but all mistakes in it are my fault. 444743Smarkm * 544743Smarkm * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 656977Sshin * 756977Sshin * $FreeBSD: head/contrib/tcp_wrappers/fix_options.c 56977 2000-02-03 10:27:03Z shin $ 844743Smarkm */ 944743Smarkm 1044743Smarkm#ifndef lint 1144743Smarkmstatic char sccsid[] = "@(#) fix_options.c 1.6 97/04/08 02:29:19"; 1244743Smarkm#endif 1344743Smarkm 1444743Smarkm#include <sys/types.h> 1544743Smarkm#include <sys/param.h> 1656977Sshin#ifdef INET6 1756977Sshin#include <sys/socket.h> 1856977Sshin#endif 1944743Smarkm#include <netinet/in.h> 2044743Smarkm#include <netinet/in_systm.h> 2144743Smarkm#include <netinet/ip.h> 2244743Smarkm#include <netdb.h> 2344743Smarkm#include <stdio.h> 2444743Smarkm#include <syslog.h> 2544743Smarkm 2644743Smarkm#ifndef IPOPT_OPTVAL 2744743Smarkm#define IPOPT_OPTVAL 0 2844743Smarkm#define IPOPT_OLEN 1 2944743Smarkm#endif 3044743Smarkm 3144743Smarkm#include "tcpd.h" 3244743Smarkm 3344743Smarkm#define BUFFER_SIZE 512 /* Was: BUFSIZ */ 3444743Smarkm 3544743Smarkm/* fix_options - get rid of IP-level socket options */ 3644743Smarkm 3744743Smarkmfix_options(request) 3844743Smarkmstruct request_info *request; 3944743Smarkm{ 4044743Smarkm#ifdef IP_OPTIONS 4144743Smarkm unsigned char optbuf[BUFFER_SIZE / 3], *cp; 4244743Smarkm char lbuf[BUFFER_SIZE], *lp; 4344743Smarkm int optsize = sizeof(optbuf), ipproto; 4444743Smarkm struct protoent *ip; 4544743Smarkm int fd = request->fd; 4644743Smarkm unsigned int opt; 4744743Smarkm int optlen; 4844743Smarkm struct in_addr dummy; 4956977Sshin#ifdef INET6 5056977Sshin struct sockaddr_storage ss; 5156977Sshin int sslen; 5244743Smarkm 5356977Sshin /* 5456977Sshin * check if this is AF_INET socket 5556977Sshin * XXX IPv6 support? 5656977Sshin */ 5756977Sshin sslen = sizeof(ss); 5856977Sshin if (getsockname(fd, (struct sockaddr *)&ss, &sslen) < 0) { 5956977Sshin syslog(LOG_ERR, "getpeername: %m"); 6056977Sshin clean_exit(request); 6156977Sshin } 6256977Sshin if (ss.ss_family != AF_INET) 6356977Sshin return; 6456977Sshin#endif 6556977Sshin 6644743Smarkm if ((ip = getprotobyname("ip")) != 0) 6744743Smarkm ipproto = ip->p_proto; 6844743Smarkm else 6944743Smarkm ipproto = IPPROTO_IP; 7044743Smarkm 7144743Smarkm if (getsockopt(fd, ipproto, IP_OPTIONS, (char *) optbuf, &optsize) == 0 7244743Smarkm && optsize != 0) { 7344743Smarkm 7444743Smarkm /* 7544743Smarkm * Horror! 4.[34] BSD getsockopt() prepends the first-hop destination 7644743Smarkm * address to the result IP options list when source routing options 7744743Smarkm * are present (see <netinet/ip_var.h>), but produces no output for 7844743Smarkm * other IP options. Solaris 2.x getsockopt() does produce output for 7944743Smarkm * non-routing IP options, and uses the same format as BSD even when 8044743Smarkm * the space for the destination address is unused. The code below 8144743Smarkm * does the right thing with 4.[34]BSD derivatives and Solaris 2, but 8244743Smarkm * may occasionally miss source routing options on incompatible 8344743Smarkm * systems such as Linux. Their choice. 8444743Smarkm * 8544743Smarkm * Look for source routing options. Drop the connection when one is 8644743Smarkm * found. Just wiping the IP options is insufficient: we would still 8744743Smarkm * help the attacker by providing a real TCP sequence number, and the 8844743Smarkm * attacker would still be able to send packets (blind spoofing). I 8944743Smarkm * discussed this attack with Niels Provos, half a year before the 9044743Smarkm * attack was described in open mailing lists. 9144743Smarkm * 9244743Smarkm * It would be cleaner to just return a yes/no reply and let the caller 9344743Smarkm * decide how to deal with it. Resident servers should not terminate. 9444743Smarkm * However I am not prepared to make changes to internal interfaces 9544743Smarkm * on short notice. 9644743Smarkm */ 9744743Smarkm#define ADDR_LEN sizeof(dummy.s_addr) 9844743Smarkm 9944743Smarkm for (cp = optbuf + ADDR_LEN; cp < optbuf + optsize; cp += optlen) { 10044743Smarkm opt = cp[IPOPT_OPTVAL]; 10144743Smarkm if (opt == IPOPT_LSRR || opt == IPOPT_SSRR) { 10244743Smarkm syslog(LOG_WARNING, 10344743Smarkm "refused connect from %s with IP source routing options", 10444743Smarkm eval_client(request)); 10544743Smarkm shutdown(fd, 2); 10644743Smarkm return; 10744743Smarkm } 10844743Smarkm if (opt == IPOPT_EOL) 10944743Smarkm break; 11044743Smarkm if (opt == IPOPT_NOP) { 11144743Smarkm optlen = 1; 11244743Smarkm } else { 11344743Smarkm optlen = cp[IPOPT_OLEN]; 11444743Smarkm if (optlen <= 0) /* Do not loop! */ 11544743Smarkm break; 11644743Smarkm } 11744743Smarkm } 11844743Smarkm lp = lbuf; 11944743Smarkm for (cp = optbuf; optsize > 0; cp++, optsize--, lp += 3) 12044743Smarkm sprintf(lp, " %2.2x", *cp); 12144743Smarkm syslog(LOG_NOTICE, 12244743Smarkm "connect from %s with IP options (ignored):%s", 12344743Smarkm eval_client(request), lbuf); 12444743Smarkm if (setsockopt(fd, ipproto, IP_OPTIONS, (char *) 0, optsize) != 0) { 12544743Smarkm syslog(LOG_ERR, "setsockopt IP_OPTIONS NULL: %m"); 12644743Smarkm shutdown(fd, 2); 12744743Smarkm } 12844743Smarkm } 12944743Smarkm#endif 13044743Smarkm} 131