=================================================================== RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/ssh/canohost.c,v retrieving revision 1.19 retrieving revision 1.20 diff -u -r1.19 -r1.20 --- src/usr.bin/ssh/canohost.c 2001/01/29 19:42:33 1.19 +++ src/usr.bin/ssh/canohost.c 2001/02/03 10:08:37 1.20 @@ -12,154 +12,165 @@ */ #include "includes.h" -RCSID("$OpenBSD: canohost.c,v 1.19 2001/01/29 19:42:33 markus Exp $"); +RCSID("$OpenBSD: canohost.c,v 1.20 2001/02/03 10:08:37 markus Exp $"); #include "packet.h" #include "xmalloc.h" #include "log.h" +void check_ip_options(int socket, char *ipaddr); + /* * Return the canonical name of the host at the other end of the socket. The * caller should free the returned string with xfree. */ char * -get_remote_hostname(int socket) +get_remote_hostname(int socket, int reverse_mapping_check) { struct sockaddr_storage from; int i; socklen_t fromlen; struct addrinfo hints, *ai, *aitop; - char name[MAXHOSTNAMELEN]; - char ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; + char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; /* Get IP address of client. */ fromlen = sizeof(from); memset(&from, 0, sizeof(from)); - if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) { + if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) { debug("getpeername failed: %.100s", strerror(errno)); fatal_cleanup(); } + if (from.ss_family == AF_INET) + check_ip_options(socket, ntop); + if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); /* Map the IP address to a host name. */ if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), - NULL, 0, NI_NAMEREQD) == 0) { - /* Got host name. */ - name[sizeof(name) - 1] = '\0'; - /* - * Convert it to all lowercase (which is expected by the rest - * of this software). - */ - for (i = 0; name[i]; i++) - if (isupper(name[i])) - name[i] = tolower(name[i]); - - /* - * Map it back to an IP address and check that the given - * address actually is an address of this host. This is - * necessary because anyone with access to a name server can - * define arbitrary names for an IP address. Mapping from - * name to IP address can be trusted better (but can still be - * fooled if the intruder has access to the name server of - * the domain). - */ - memset(&hints, 0, sizeof(hints)); - hints.ai_family = from.ss_family; - hints.ai_socktype = SOCK_STREAM; - if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { - log("reverse mapping checking getaddrinfo for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name); - strlcpy(name, ntop, sizeof name); - goto check_ip_options; - } - /* Look for the address from the list of addresses. */ - for (ai = aitop; ai; ai = ai->ai_next) { - if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, - sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && - (strcmp(ntop, ntop2) == 0)) - break; - } - freeaddrinfo(aitop); - /* If we reached the end of the list, the address was not there. */ - if (!ai) { - /* Address not found for the host name. */ - log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!", - ntop, name); - strlcpy(name, ntop, sizeof name); - goto check_ip_options; - } - /* Address was found for the host name. We accept the host name. */ - } else { - /* Host name not found. Use ascii representation of the address. */ - strlcpy(name, ntop, sizeof name); - log("Could not reverse map address %.100s.", name); + NULL, 0, NI_NAMEREQD) != 0) { + /* Host name not found. Use ip address. */ + log("Could not reverse map address %.100s.", ntop); + return xstrdup(ntop); } -check_ip_options: - + /* Got host name. */ + name[sizeof(name) - 1] = '\0'; /* - * If IP options are supported, make sure there are none (log and - * disconnect them if any are found). Basically we are worried about - * source routing; it can be used to pretend you are somebody - * (ip-address) you are not. That itself may be "almost acceptable" - * under certain circumstances, but rhosts autentication is useless - * if source routing is accepted. Notice also that if we just dropped - * source routing here, the other side could use IP spoofing to do - * rest of the interaction and could still bypass security. So we - * exit here if we detect any IP options. + * Convert it to all lowercase (which is expected by the rest + * of this software). */ - /* IP options -- IPv4 only */ - if (from.ss_family == AF_INET) { - u_char options[200], *ucp; - char text[1024], *cp; - socklen_t option_size; - int ipproto; - struct protoent *ip; + for (i = 0; name[i]; i++) + if (isupper(name[i])) + name[i] = tolower(name[i]); - if ((ip = getprotobyname("ip")) != NULL) - ipproto = ip->p_proto; - else - ipproto = IPPROTO_IP; - option_size = sizeof(options); - if (getsockopt(socket, ipproto, IP_OPTIONS, (char *) options, - &option_size) >= 0 && option_size != 0) { - cp = text; - /* Note: "text" buffer must be at least 3x as big as options. */ - for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3) - sprintf(cp, " %2.2x", *ucp); - log("Connection from %.100s with IP options:%.800s", - ntop, text); - packet_disconnect("Connection from %.100s with IP options:%.800s", - ntop, text); - } + if (!reverse_mapping_check) + return xstrdup(name); + /* + * Map it back to an IP address and check that the given + * address actually is an address of this host. This is + * necessary because anyone with access to a name server can + * define arbitrary names for an IP address. Mapping from + * name to IP address can be trusted better (but can still be + * fooled if the intruder has access to the name server of + * the domain). + */ + memset(&hints, 0, sizeof(hints)); + hints.ai_family = from.ss_family; + hints.ai_socktype = SOCK_STREAM; + if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { + log("reverse mapping checking getaddrinfo for %.700s " + "failed - POSSIBLE BREAKIN ATTEMPT!", name); + return xstrdup(ntop); } - + /* Look for the address from the list of addresses. */ + for (ai = aitop; ai; ai = ai->ai_next) { + if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, + sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && + (strcmp(ntop, ntop2) == 0)) + break; + } + freeaddrinfo(aitop); + /* If we reached the end of the list, the address was not there. */ + if (!ai) { + /* Address not found for the host name. */ + log("Address %.100s maps to %.600s, but this does not " + "map back to the address - POSSIBLE BREAKIN ATTEMPT!", + ntop, name); + return xstrdup(ntop); + } return xstrdup(name); } /* + * If IP options are supported, make sure there are none (log and + * disconnect them if any are found). Basically we are worried about + * source routing; it can be used to pretend you are somebody + * (ip-address) you are not. That itself may be "almost acceptable" + * under certain circumstances, but rhosts autentication is useless + * if source routing is accepted. Notice also that if we just dropped + * source routing here, the other side could use IP spoofing to do + * rest of the interaction and could still bypass security. So we + * exit here if we detect any IP options. + */ +/* IPv4 only */ +void +check_ip_options(int socket, char *ipaddr) +{ + u_char options[200], *ucp; + char text[1024], *cp; + socklen_t option_size; + int ipproto; + struct protoent *ip; + + if ((ip = getprotobyname("ip")) != NULL) + ipproto = ip->p_proto; + else + ipproto = IPPROTO_IP; + option_size = sizeof(options); + if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options, + &option_size) >= 0 && option_size != 0) { + cp = text; + /* Note: "text" buffer must be at least 3x as big as options. */ + for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3) + sprintf(cp, " %2.2x", *ucp); + log("Connection from %.100s with IP options:%.800s", + ipaddr, text); + packet_disconnect("Connection from %.100s with IP options:%.800s", + ipaddr, text); + } +} + +/* * Return the canonical name of the host in the other side of the current * connection. The host name is cached, so it is efficient to call this * several times. */ const char * -get_canonical_hostname() +get_canonical_hostname(int reverse_mapping_check) { static char *canonical_host_name = NULL; + static int reverse_mapping_checked = 0; - /* Check if we have previously retrieved this same name. */ - if (canonical_host_name != NULL) - return canonical_host_name; + /* Check if we have previously retrieved name with same option. */ + if (canonical_host_name != NULL) { + if (reverse_mapping_checked != reverse_mapping_check) + xfree(canonical_host_name); + else + return canonical_host_name; + } /* Get the real hostname if socket; otherwise return UNKNOWN. */ if (packet_connection_is_on_socket()) - canonical_host_name = get_remote_hostname(packet_get_connection_in()); + canonical_host_name = get_remote_hostname( + packet_get_connection_in(), reverse_mapping_check); else canonical_host_name = xstrdup("UNKNOWN"); + reverse_mapping_checked = reverse_mapping_check; return canonical_host_name; }