/* $OpenBSD: canohost.c,v 1.62 2007/12/27 14:22:08 dtucker Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * Functions for returning the canonical host name of the remote site. * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this * software must be clearly marked as such, and if the derived work is * incompatible with the protocol description in the RFC file, it must be * called by a name other than "ssh" or "Secure Shell". */ #include #include #include #include #include #include #include #include #include #include #include "xmalloc.h" #include "packet.h" #include "log.h" #include "canohost.h" #include "misc.h" static void check_ip_options(int, char *); /* * Return the canonical name of the host at the other end of the socket. The * caller should free the returned string with xfree. */ static char * get_remote_hostname(int sock, int use_dns) { struct sockaddr_storage from; int i; socklen_t fromlen; struct addrinfo hints, *ai, *aitop; 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(sock, (struct sockaddr *)&from, &fromlen) < 0) { debug("getpeername failed: %.100s", strerror(errno)); cleanup_exit(255); } if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); if (from.ss_family == AF_INET) check_ip_options(sock, ntop); if (!use_dns) return xstrdup(ntop); debug3("Trying to reverse map address %.100s.", ntop); /* Map the IP address to a host name. */ if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), NULL, 0, NI_NAMEREQD) != 0) { /* Host name not found. Use ip address. */ return xstrdup(ntop); } /* * if reverse lookup result looks like a numeric hostname, * someone is trying to trick us by PTR record like following: * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 */ memset(&hints, 0, sizeof(hints)); hints.ai_socktype = SOCK_DGRAM; /*dummy*/ hints.ai_flags = AI_NUMERICHOST; if (getaddrinfo(name, "0", &hints, &ai) == 0) { logit("Nasty PTR record \"%s\" is set up for %s, ignoring", name, ntop); freeaddrinfo(ai); return xstrdup(ntop); } /* * 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] = (char)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) { logit("reverse mapping checking getaddrinfo for %.700s " "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); 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. */ logit("Address %.100s maps to %.600s, but this does not " "map back to the address - POSSIBLE BREAK-IN 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 */ static void check_ip_options(int sock, char *ipaddr) { u_char options[200]; char text[sizeof(options) * 3 + 1]; socklen_t option_size; u_int i; int ipproto; struct protoent *ip; if ((ip = getprotobyname("ip")) != NULL) ipproto = ip->p_proto; else ipproto = IPPROTO_IP; option_size = sizeof(options); if (getsockopt(sock, ipproto, IP_OPTIONS, options, &option_size) >= 0 && option_size != 0) { text[0] = '\0'; for (i = 0; i < option_size; i++) snprintf(text + i*3, sizeof(text) - i*3, " %2.2x", options[i]); fatal("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(int use_dns) { char *host; static char *canonical_host_name = NULL; static char *remote_ip = NULL; /* Check if we have previously retrieved name with same option. */ if (use_dns && canonical_host_name != NULL) return canonical_host_name; if (!use_dns && remote_ip != NULL) return remote_ip; /* Get the real hostname if socket; otherwise return UNKNOWN. */ if (packet_connection_is_on_socket()) host = get_remote_hostname(packet_get_connection_in(), use_dns); else host = "UNKNOWN"; if (use_dns) canonical_host_name = host; else remote_ip = host; return host; } /* * Returns the local/remote IP-address/hostname of socket as a string. * The returned string must be freed. */ static char * get_socket_address(int sock, int remote, int flags) { struct sockaddr_storage addr; socklen_t addrlen; char ntop[NI_MAXHOST]; int r; /* Get IP address of client. */ addrlen = sizeof(addr); memset(&addr, 0, sizeof(addr)); if (remote) { if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) < 0) return NULL; } else { if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) < 0) return NULL; } /* Get the address in ascii. */ if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop), NULL, 0, flags)) != 0) { error("get_socket_address: getnameinfo %d failed: %s", flags, ssh_gai_strerror(r)); return NULL; } return xstrdup(ntop); } char * get_peer_ipaddr(int sock) { char *p; if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) return p; return xstrdup("UNKNOWN"); } char * get_local_ipaddr(int sock) { char *p; if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) return p; return xstrdup("UNKNOWN"); } char * get_local_name(int sock) { return get_socket_address(sock, 0, NI_NAMEREQD); } /* * Returns the IP-address of the remote host as a string. The returned * string must not be freed. */ const char * get_remote_ipaddr(void) { static char *canonical_host_ip = NULL; /* Check whether we have cached the ipaddr. */ if (canonical_host_ip == NULL) { if (packet_connection_is_on_socket()) { canonical_host_ip = get_peer_ipaddr(packet_get_connection_in()); if (canonical_host_ip == NULL) cleanup_exit(255); } else { /* If not on socket, return UNKNOWN. */ canonical_host_ip = xstrdup("UNKNOWN"); } } return canonical_host_ip; } const char * get_remote_name_or_ip(u_int utmp_len, int use_dns) { static const char *remote = ""; if (utmp_len > 0) remote = get_canonical_hostname(use_dns); if (utmp_len == 0 || strlen(remote) > utmp_len) remote = get_remote_ipaddr(); return remote; } /* Returns the local/remote port for the socket. */ static int get_sock_port(int sock, int local) { struct sockaddr_storage from; socklen_t fromlen; char strport[NI_MAXSERV]; int r; /* Get IP address of client. */ fromlen = sizeof(from); memset(&from, 0, sizeof(from)); if (local) { if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { error("getsockname failed: %.100s", strerror(errno)); return 0; } } else { if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { debug("getpeername failed: %.100s", strerror(errno)); return -1; } } /* Return port number. */ if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, strport, sizeof(strport), NI_NUMERICSERV)) != 0) fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", ssh_gai_strerror(r)); return atoi(strport); } /* Returns remote/local port number for the current connection. */ static int get_port(int local) { /* * If the connection is not a socket, return 65535. This is * intentionally chosen to be an unprivileged port number. */ if (!packet_connection_is_on_socket()) return 65535; /* Get socket and return the port number. */ return get_sock_port(packet_get_connection_in(), local); } int get_peer_port(int sock) { return get_sock_port(sock, 0); } int get_remote_port(void) { static int port = -1; /* Cache to avoid getpeername() on a dead connection */ if (port == -1) port = get_port(0); return port; } int get_local_port(void) { return get_port(1); }