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|
/* $OpenBSD: canohost.c,v 1.66 2010/01/13 01:20:20 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 "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 <unistd.h>
#include "xmalloc.h"
#include "packet.h"
#include "log.h"
#include "canohost.h"
#include "misc.h"
static void check_ip_options(int, char *);
static char *canonical_host_ip = NULL;
static int cached_port = -1;
/*
* 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
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