canohost.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  *
  * canohost.c
  *
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  *
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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 1.6 1999/12/18 09:57:40 damien 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;

 /* Returns 1 if remote host is connected via socket, 0 if not. */

 int
 peer_connection_is_on_socket()
 {
 	struct sockaddr_in from;
 	int fromlen;
 	int in = packet_get_connection_in();
 	int out = packet_get_connection_out();

 	/* filedescriptors in and out are the same, so it's a socket */
 	if (in == out)
 		return 1;
 	fromlen = sizeof(from);
 	memset(&from, 0, sizeof(from));
 	if (getpeername(in, (struct sockaddr *) & from, &fromlen) < 0)
 		return 0;
 	if (from.sin_family != AF_INET)
 		return 0;

 	return 1;
 }

 /*
  * 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 (peer_connection_is_on_socket())
 		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 (!peer_connection_is_on_socket()) {
 		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 (!peer_connection_is_on_socket())
 		return 65535;

 	/* Get client socket. */
 	socket = packet_get_connection_in();

 	/* Get and return the peer port number. */
 	return get_peer_port(socket);
 }
	/*
	*
	* canohost.c
	*
	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	*
	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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 1.6 1999/12/18 09:57:40 damien 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;

	/* Returns 1 if remote host is connected via socket, 0 if not. */

	int
	peer_connection_is_on_socket()
	{
	struct sockaddr_in from;
	int fromlen;
	int in = packet_get_connection_in();
	int out = packet_get_connection_out();

	/* filedescriptors in and out are the same, so it's a socket */
	if (in == out)
	return 1;
	fromlen = sizeof(from);
	memset(&from, 0, sizeof(from));
	if (getpeername(in, (struct sockaddr *) & from, &fromlen) < 0)
	return 0;
	if (from.sin_family != AF_INET)
	return 0;

	return 1;
	}

	/*
	* 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 (peer_connection_is_on_socket())
	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 (!peer_connection_is_on_socket()) {
	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 (!peer_connection_is_on_socket())
	return 65535;

	/* Get client socket. */
	socket = packet_get_connection_in();

	/* Get and return the peer port number. */
	return get_peer_port(socket);
	}