/* * * canohost.c * * Author: Tatu Ylonen * * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * * Created: Sun Jul 2 17:52:22 1995 ylo * * Functions for returning the canonical host name of the remote site. * */ #include "includes.h" RCSID("$Id: canohost.c,v 1.8 1999/11/24 19:53:44 markus Exp $"); #include "packet.h" #include "xmalloc.h" #include "ssh.h" /* * 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) { struct sockaddr_in from; int fromlen, i; struct hostent *hp; char name[MAXHOSTNAMELEN]; /* Get IP address of client. */ fromlen = sizeof(from); memset(&from, 0, sizeof(from)); if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) { debug("getpeername failed: %.100s", strerror(errno)); fatal_cleanup(); } /* Map the IP address to a host name. */ hp = gethostbyaddr((char *) &from.sin_addr, sizeof(struct in_addr), from.sin_family); if (hp) { /* Got host name, find canonic host name. */ if (strchr(hp->h_name, '.') != 0) strlcpy(name, hp->h_name, sizeof(name)); else if (hp->h_aliases != 0 && hp->h_aliases[0] != 0 && strchr(hp->h_aliases[0], '.') != 0) strlcpy(name, hp->h_aliases[0], sizeof(name)); else strlcpy(name, hp->h_name, sizeof(name)); /* * 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). */ hp = gethostbyname(name); if (!hp) { log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name); strlcpy(name, inet_ntoa(from.sin_addr), sizeof name); goto check_ip_options; } /* Look for the address from the list of addresses. */ for (i = 0; hp->h_addr_list[i]; i++) if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr)) == 0) break; /* * If we reached the end of the list, the address was not * there. */ if (!hp->h_addr_list[i]) { /* 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!", inet_ntoa(from.sin_addr), name); strlcpy(name, inet_ntoa(from.sin_addr), 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, inet_ntoa(from.sin_addr), sizeof name); log("Could not reverse map address %.100s.", name); } check_ip_options: /* * 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. */ { unsigned char options[200], *ucp; char text[1024], *cp; int option_size, ipproto; struct protoent *ip; if ((ip = getprotobyname("ip")) != NULL) ipproto = ip->p_proto; else ipproto = IPPROTO_IP; option_size = sizeof(options); if (getsockopt(0, 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", inet_ntoa(from.sin_addr), text); packet_disconnect("Connection from %.100s with IP options:%.800s", inet_ntoa(from.sin_addr), text); } } return xstrdup(name); } static char *canonical_host_name = NULL; static char *canonical_host_ip = NULL; /* * 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() { /* Check if we have previously retrieved this same name. */ if (canonical_host_name != NULL) return canonical_host_name; /* Get the real hostname if socket; otherwise return UNKNOWN. */ if (packet_get_connection_in() == packet_get_connection_out()) canonical_host_name = get_remote_hostname(packet_get_connection_in()); else canonical_host_name = xstrdup("UNKNOWN"); return canonical_host_name; } /* * Returns the IP-address of the remote host as a string. The returned * string need not be freed. */ const char * get_remote_ipaddr() { struct sockaddr_in from; int fromlen, socket; /* Check whether we have chached the name. */ if (canonical_host_ip != NULL) return canonical_host_ip; /* If not a socket, return UNKNOWN. */ if (packet_get_connection_in() != packet_get_connection_out()) { canonical_host_ip = xstrdup("UNKNOWN"); return canonical_host_ip; } /* Get client socket. */ socket = packet_get_connection_in(); /* Get IP address of client. */ fromlen = sizeof(from); memset(&from, 0, sizeof(from)); if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) { debug("getpeername failed: %.100s", strerror(errno)); fatal_cleanup(); } /* Get the IP address in ascii. */ canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr)); /* Return ip address string. */ return canonical_host_ip; } /* Returns the port of the peer of the socket. */ int get_peer_port(int sock) { struct sockaddr_in from; int fromlen; /* 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)); fatal_cleanup(); } /* Return port number. */ return ntohs(from.sin_port); } /* Returns the port number of the remote host. */ int get_remote_port() { int socket; /* * If the connection is not a socket, return 65535. This is * intentionally chosen to be an unprivileged port number. */ if (packet_get_connection_in() != packet_get_connection_out()) return 65535; /* Get client socket. */ socket = packet_get_connection_in(); /* Get and return the peer port number. */ return get_peer_port(socket); }