235 lines
7.0 KiB
C
235 lines
7.0 KiB
C
/*
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canohost.c
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Author: Tatu Ylonen <ylo@cs.hut.fi>
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Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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All rights reserved
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Created: Sun Jul 2 17:52:22 1995 ylo
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Functions for returning the canonical host name of the remote site.
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*/
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#include "includes.h"
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RCSID("$Id: canohost.c,v 1.1 1999/10/27 03:42:43 damien Exp $");
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#include "packet.h"
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#include "xmalloc.h"
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#include "ssh.h"
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/* Return the canonical name of the host at the other end of the socket.
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The caller should free the returned string with xfree. */
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char *get_remote_hostname(int socket)
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{
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struct sockaddr_in from;
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int fromlen, i;
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struct hostent *hp;
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char name[MAXHOSTNAMELEN];
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/* Get IP address of client. */
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fromlen = sizeof(from);
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memset(&from, 0, sizeof(from));
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if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0)
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{
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error("getpeername failed: %.100s", strerror(errno));
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strlcpy(name, "UNKNOWN", sizeof name);
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goto check_ip_options;
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}
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/* Map the IP address to a host name. */
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hp = gethostbyaddr((char *)&from.sin_addr, sizeof(struct in_addr),
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from.sin_family);
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if (hp)
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{
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/* Got host name, find canonic host name. */
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if (strchr(hp->h_name, '.') != 0)
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strlcpy(name, hp->h_name, sizeof(name));
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else if (hp->h_aliases != 0
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&& hp->h_aliases[0] != 0
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&& strchr(hp->h_aliases[0], '.') != 0)
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strlcpy(name, hp->h_aliases[0], sizeof(name));
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else
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strlcpy(name, hp->h_name, sizeof(name));
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/* Convert it to all lowercase (which is expected by the rest of this
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software). */
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for (i = 0; name[i]; i++)
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if (isupper(name[i]))
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name[i] = tolower(name[i]);
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/* Map it back to an IP address and check that the given address actually
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is an address of this host. This is necessary because anyone with
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access to a name server can define arbitrary names for an IP address.
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Mapping from name to IP address can be trusted better (but can still
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be fooled if the intruder has access to the name server of the
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domain). */
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hp = gethostbyname(name);
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if (!hp)
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{
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log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
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strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
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goto check_ip_options;
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}
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/* Look for the address from the list of addresses. */
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for (i = 0; hp->h_addr_list[i]; i++)
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if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr))
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== 0)
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break;
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/* If we reached the end of the list, the address was not there. */
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if (!hp->h_addr_list[i])
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{
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/* Address not found for the host name. */
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log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!",
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inet_ntoa(from.sin_addr), name);
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strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
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goto check_ip_options;
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}
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/* Address was found for the host name. We accept the host name. */
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}
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else
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{
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/* Host name not found. Use ascii representation of the address. */
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strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
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log("Could not reverse map address %.100s.", name);
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}
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check_ip_options:
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/* If IP options are supported, make sure there are none (log and clear
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them if any are found). Basically we are worried about source routing;
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it can be used to pretend you are somebody (ip-address) you are not.
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That itself may be "almost acceptable" under certain circumstances,
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but rhosts autentication is useless if source routing is accepted.
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Notice also that if we just dropped source routing here, the other
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side could use IP spoofing to do rest of the interaction and could still
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bypass security. So we exit here if we detect any IP options. */
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{
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unsigned char options[200], *ucp;
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char text[1024], *cp;
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int option_size, ipproto;
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struct protoent *ip;
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if ((ip = getprotobyname("ip")) != NULL)
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ipproto = ip->p_proto;
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else
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ipproto = IPPROTO_IP;
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option_size = sizeof(options);
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if (getsockopt(0, ipproto, IP_OPTIONS, (char *)options,
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&option_size) >= 0 && option_size != 0)
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{
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cp = text;
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/* Note: "text" buffer must be at least 3x as big as options. */
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for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
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sprintf(cp, " %2.2x", *ucp);
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log("Connection from %.100s with IP options:%.800s",
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inet_ntoa(from.sin_addr), text);
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packet_disconnect("Connection from %.100s with IP options:%.800s",
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inet_ntoa(from.sin_addr), text);
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}
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}
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return xstrdup(name);
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}
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static char *canonical_host_name = NULL;
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static char *canonical_host_ip = NULL;
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/* Return the canonical name of the host in the other side of the current
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connection. The host name is cached, so it is efficient to call this
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several times. */
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const char *get_canonical_hostname()
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{
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/* Check if we have previously retrieved this same name. */
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if (canonical_host_name != NULL)
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return canonical_host_name;
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/* Get the real hostname if socket; otherwise return UNKNOWN. */
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if (packet_get_connection_in() == packet_get_connection_out())
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canonical_host_name = get_remote_hostname(packet_get_connection_in());
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else
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canonical_host_name = xstrdup("UNKNOWN");
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return canonical_host_name;
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}
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/* Returns the IP-address of the remote host as a string. The returned
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string need not be freed. */
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const char *get_remote_ipaddr()
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{
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struct sockaddr_in from;
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int fromlen, socket;
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/* Check if we have previously retrieved this same name. */
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if (canonical_host_ip != NULL)
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return canonical_host_ip;
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/* If not a socket, return UNKNOWN. */
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if (packet_get_connection_in() != packet_get_connection_out())
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{
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canonical_host_ip = xstrdup("UNKNOWN");
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return canonical_host_ip;
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}
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/* Get client socket. */
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socket = packet_get_connection_in();
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/* Get IP address of client. */
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fromlen = sizeof(from);
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memset(&from, 0, sizeof(from));
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if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0)
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{
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error("getpeername failed: %.100s", strerror(errno));
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return NULL;
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}
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/* Get the IP address in ascii. */
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canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr));
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/* Return ip address string. */
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return canonical_host_ip;
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}
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/* Returns the port of the peer of the socket. */
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int get_peer_port(int sock)
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{
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struct sockaddr_in from;
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int fromlen;
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/* Get IP address of client. */
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fromlen = sizeof(from);
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memset(&from, 0, sizeof(from));
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if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0)
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{
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error("getpeername failed: %.100s", strerror(errno));
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return 0;
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}
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/* Return port number. */
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return ntohs(from.sin_port);
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}
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/* Returns the port number of the remote host. */
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int get_remote_port()
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{
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int socket;
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/* If the connection is not a socket, return 65535. This is intentionally
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chosen to be an unprivileged port number. */
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if (packet_get_connection_in() != packet_get_connection_out())
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return 65535;
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/* Get client socket. */
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socket = packet_get_connection_in();
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/* Get and return the peer port number. */
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return get_peer_port(socket);
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}
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