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/*
*
* 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);
}
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