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Do not pass "0" strings as ports to getaddrinfo because the lookups
can slow things down and we never use the service info anyway. bz
#859, patch from YOSHIFUJI Hideaki and John Devitofranceschi.  ok
deraadt@ djm@

djm belives that the reason for the "0" strings is to ensure that
it's not possible to call getaddrinfo with both host and port being
NULL.  In the case of canohost.c host is a local array.  In the
case of sshconnect.c, it's checked for null immediately before use.

In dns.c it ultimately comes from ssh.c:main() and is guaranteed to
be non-null but it's not obvious, so I added a warning message in
case it is ever passed a null.

/* $OpenBSD: canohost.c,v 1.63 2008/06/12 00:03:49 dtucker Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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 <sys/types.h>
#include <sys/socket.h>

#include <netinet/in.h>

#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>

#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, NULL, &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);
}