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/* $OpenBSD: canohost.c,v 1.64 2009/02/12 03:00:56 djm 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 "includes.h"
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.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 (from.ss_family == AF_INET)
check_ip_options(sock, ntop);
ipv64_normalise_mapped(&from, &fromlen);
if (from.ss_family == AF_INET6)
fromlen = sizeof(struct sockaddr_in6);
if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
NULL, 0, NI_NUMERICHOST) != 0)
fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
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)
{
#ifdef IP_OPTIONS
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);
}
#endif /* IP_OPTIONS */
}
void
ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
{
struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
struct in_addr inaddr;
u_int16_t port;
if (addr->ss_family != AF_INET6 ||
!IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
return;
debug3("Normalising mapped IPv4 in IPv6 address");
memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
port = a6->sin6_port;
memset(addr, 0, sizeof(*a4));
a4->sin_family = AF_INET;
*len = sizeof(*a4);
memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
a4->sin_port = port;
}
/*
* 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;
}
/* Work around Linux IPv6 weirdness */
if (addr.ss_family == AF_INET6)
addrlen = sizeof(struct sockaddr_in6);
ipv64_normalise_mapped(&addr, &addrlen);
/* 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. */
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;
}
}
/* Work around Linux IPv6 weirdness */
if (from.ss_family == AF_INET6)
fromlen = sizeof(struct sockaddr_in6);
/* 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);
}