| /* |
| * 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> |
| #ifdef INET6 |
| #include <sys/socket.h> |
| #endif |
| #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; |
| #ifdef __GLIBC__ |
| size_t optsize = sizeof(optbuf), ipproto; |
| #else |
| int optsize = sizeof(optbuf), ipproto; |
| #endif |
| struct protoent *ip; |
| int fd = request->fd; |
| unsigned int opt; |
| int optlen; |
| struct in_addr dummy; |
| #ifdef INET6 |
| struct sockaddr_storage ss; |
| socklen_t sslen; |
| |
| /* |
| * check if this is AF_INET socket |
| * XXX IPv6 support? |
| */ |
| sslen = sizeof(ss); |
| if (getsockname(fd, (struct sockaddr *)&ss, &sslen) < 0) { |
| syslog(LOG_ERR, "getpeername: %m"); |
| clean_exit(request); |
| } |
| if (ss.ss_family != AF_INET) |
| return; |
| #endif |
| |
| 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 |
| } |