1262566Sdes/* $OpenBSD: canohost.c,v 1.70 2014/01/19 04:17:29 dtucker Exp $ */ 257429Smarkm/* 357429Smarkm * Author: Tatu Ylonen <ylo@cs.hut.fi> 457429Smarkm * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 557429Smarkm * All rights reserved 657429Smarkm * Functions for returning the canonical host name of the remote site. 760573Skris * 865674Skris * As far as I am concerned, the code I have written for this software 965674Skris * can be used freely for any purpose. Any derived versions of this 1065674Skris * software must be clearly marked as such, and if the derived work is 1165674Skris * incompatible with the protocol description in the RFC file, it must be 1265674Skris * called by a name other than "ssh" or "Secure Shell". 1357429Smarkm */ 1457429Smarkm 1557429Smarkm#include "includes.h" 1657429Smarkm 17162856Sdes#include <sys/types.h> 18162856Sdes#include <sys/socket.h> 19162856Sdes 20162856Sdes#include <netinet/in.h> 21162856Sdes#include <arpa/inet.h> 22162856Sdes 23162856Sdes#include <errno.h> 24162856Sdes#include <netdb.h> 25162856Sdes#include <stdio.h> 26162856Sdes#include <stdlib.h> 27162856Sdes#include <string.h> 28162856Sdes#include <stdarg.h> 29204917Sdes#include <unistd.h> 30162856Sdes 31162856Sdes#include "xmalloc.h" 3257429Smarkm#include "packet.h" 3376262Sgreen#include "log.h" 3476262Sgreen#include "canohost.h" 35181111Sdes#include "misc.h" 3657429Smarkm 3792559Sdesstatic void check_ip_options(int, char *); 38197679Sdesstatic char *canonical_host_ip = NULL; 39197679Sdesstatic int cached_port = -1; 4076262Sgreen 4157429Smarkm/* 4257429Smarkm * Return the canonical name of the host at the other end of the socket. The 43255767Sdes * caller should free the returned string. 4457429Smarkm */ 4557429Smarkm 4692559Sdesstatic char * 47137019Sdesget_remote_hostname(int sock, int use_dns) 4857429Smarkm{ 4957429Smarkm struct sockaddr_storage from; 5057429Smarkm socklen_t fromlen; 5157429Smarkm struct addrinfo hints, *ai, *aitop; 5276262Sgreen char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST]; 5357429Smarkm 5457429Smarkm /* Get IP address of client. */ 5557429Smarkm fromlen = sizeof(from); 5657429Smarkm memset(&from, 0, sizeof(from)); 57137019Sdes if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 5857429Smarkm debug("getpeername failed: %.100s", strerror(errno)); 59126277Sdes cleanup_exit(255); 6057429Smarkm } 6176262Sgreen 62162856Sdes if (from.ss_family == AF_INET) 63162856Sdes check_ip_options(sock, ntop); 64162856Sdes 65126277Sdes ipv64_normalise_mapped(&from, &fromlen); 6698941Sdes 67113911Sdes if (from.ss_family == AF_INET6) 68113911Sdes fromlen = sizeof(struct sockaddr_in6); 6998941Sdes 7057429Smarkm if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop), 7192559Sdes NULL, 0, NI_NUMERICHOST) != 0) 7257429Smarkm fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed"); 7357429Smarkm 74124211Sdes if (!use_dns) 75124211Sdes return xstrdup(ntop); 76124211Sdes 7776262Sgreen debug3("Trying to reverse map address %.100s.", ntop); 7857429Smarkm /* Map the IP address to a host name. */ 7957429Smarkm if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 8092559Sdes NULL, 0, NI_NAMEREQD) != 0) { 8176262Sgreen /* Host name not found. Use ip address. */ 8276262Sgreen return xstrdup(ntop); 8357429Smarkm } 8457429Smarkm 8576262Sgreen /* 86124211Sdes * if reverse lookup result looks like a numeric hostname, 87124211Sdes * someone is trying to trick us by PTR record like following: 88124211Sdes * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 89124211Sdes */ 90124211Sdes memset(&hints, 0, sizeof(hints)); 91124211Sdes hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 92124211Sdes hints.ai_flags = AI_NUMERICHOST; 93181111Sdes if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 94124211Sdes logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 95124211Sdes name, ntop); 96124211Sdes freeaddrinfo(ai); 97124211Sdes return xstrdup(ntop); 98124211Sdes } 99124211Sdes 100262566Sdes /* Names are stores in lowercase. */ 101262566Sdes lowercase(name); 102262566Sdes 103124211Sdes /* 10476262Sgreen * Map it back to an IP address and check that the given 10576262Sgreen * address actually is an address of this host. This is 10676262Sgreen * necessary because anyone with access to a name server can 10776262Sgreen * define arbitrary names for an IP address. Mapping from 10876262Sgreen * name to IP address can be trusted better (but can still be 10976262Sgreen * fooled if the intruder has access to the name server of 11076262Sgreen * the domain). 11157429Smarkm */ 11276262Sgreen memset(&hints, 0, sizeof(hints)); 11376262Sgreen hints.ai_family = from.ss_family; 11476262Sgreen hints.ai_socktype = SOCK_STREAM; 11576262Sgreen if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 116124211Sdes logit("reverse mapping checking getaddrinfo for %.700s " 117162856Sdes "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); 11876262Sgreen return xstrdup(ntop); 11957429Smarkm } 12076262Sgreen /* Look for the address from the list of addresses. */ 12176262Sgreen for (ai = aitop; ai; ai = ai->ai_next) { 12276262Sgreen if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 12376262Sgreen sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 12476262Sgreen (strcmp(ntop, ntop2) == 0)) 12576262Sgreen break; 12676262Sgreen } 12776262Sgreen freeaddrinfo(aitop); 12876262Sgreen /* If we reached the end of the list, the address was not there. */ 12976262Sgreen if (!ai) { 13076262Sgreen /* Address not found for the host name. */ 131124211Sdes logit("Address %.100s maps to %.600s, but this does not " 132157019Sdes "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", 13376262Sgreen ntop, name); 13476262Sgreen return xstrdup(ntop); 13576262Sgreen } 13657429Smarkm return xstrdup(name); 13757429Smarkm} 13857429Smarkm 13957429Smarkm/* 14076262Sgreen * If IP options are supported, make sure there are none (log and 14176262Sgreen * disconnect them if any are found). Basically we are worried about 14276262Sgreen * source routing; it can be used to pretend you are somebody 14376262Sgreen * (ip-address) you are not. That itself may be "almost acceptable" 14476262Sgreen * under certain circumstances, but rhosts autentication is useless 14576262Sgreen * if source routing is accepted. Notice also that if we just dropped 14676262Sgreen * source routing here, the other side could use IP spoofing to do 14776262Sgreen * rest of the interaction and could still bypass security. So we 14876262Sgreen * exit here if we detect any IP options. 14976262Sgreen */ 15076262Sgreen/* IPv4 only */ 15192559Sdesstatic void 152137019Sdescheck_ip_options(int sock, char *ipaddr) 15376262Sgreen{ 154124211Sdes#ifdef IP_OPTIONS 15576262Sgreen u_char options[200]; 15676262Sgreen char text[sizeof(options) * 3 + 1]; 157262566Sdes socklen_t option_size, i; 158149753Sdes int ipproto; 15976262Sgreen struct protoent *ip; 16076262Sgreen 16176262Sgreen if ((ip = getprotobyname("ip")) != NULL) 16276262Sgreen ipproto = ip->p_proto; 16376262Sgreen else 16476262Sgreen ipproto = IPPROTO_IP; 16576262Sgreen option_size = sizeof(options); 166137019Sdes if (getsockopt(sock, ipproto, IP_OPTIONS, options, 16776262Sgreen &option_size) >= 0 && option_size != 0) { 16876262Sgreen text[0] = '\0'; 16976262Sgreen for (i = 0; i < option_size; i++) 17076262Sgreen snprintf(text + i*3, sizeof(text) - i*3, 17176262Sgreen " %2.2x", options[i]); 172157019Sdes fatal("Connection from %.100s with IP options:%.800s", 17376262Sgreen ipaddr, text); 17476262Sgreen } 175124211Sdes#endif /* IP_OPTIONS */ 17676262Sgreen} 17776262Sgreen 178147005Sdesvoid 179126277Sdesipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len) 180126277Sdes{ 181126277Sdes struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr; 182126277Sdes struct sockaddr_in *a4 = (struct sockaddr_in *)addr; 183126277Sdes struct in_addr inaddr; 184126277Sdes u_int16_t port; 185126277Sdes 186149753Sdes if (addr->ss_family != AF_INET6 || 187126277Sdes !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr)) 188126277Sdes return; 189126277Sdes 190126277Sdes debug3("Normalising mapped IPv4 in IPv6 address"); 191126277Sdes 192126277Sdes memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr)); 193126277Sdes port = a6->sin6_port; 194126277Sdes 195264377Sdes memset(a4, 0, sizeof(*a4)); 196126277Sdes 197126277Sdes a4->sin_family = AF_INET; 198126277Sdes *len = sizeof(*a4); 199126277Sdes memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr)); 200126277Sdes a4->sin_port = port; 201126277Sdes} 202126277Sdes 20376262Sgreen/* 20457429Smarkm * Return the canonical name of the host in the other side of the current 20557429Smarkm * connection. The host name is cached, so it is efficient to call this 20657429Smarkm * several times. 20757429Smarkm */ 20857429Smarkm 20957429Smarkmconst char * 210124211Sdesget_canonical_hostname(int use_dns) 21157429Smarkm{ 212157019Sdes char *host; 21357429Smarkm static char *canonical_host_name = NULL; 214157019Sdes static char *remote_ip = NULL; 21557429Smarkm 21676262Sgreen /* Check if we have previously retrieved name with same option. */ 217157019Sdes if (use_dns && canonical_host_name != NULL) 218157019Sdes return canonical_host_name; 219157019Sdes if (!use_dns && remote_ip != NULL) 220157019Sdes return remote_ip; 22157429Smarkm 22257429Smarkm /* Get the real hostname if socket; otherwise return UNKNOWN. */ 22357429Smarkm if (packet_connection_is_on_socket()) 224157019Sdes host = get_remote_hostname(packet_get_connection_in(), use_dns); 22557429Smarkm else 226157019Sdes host = "UNKNOWN"; 22757429Smarkm 228157019Sdes if (use_dns) 229157019Sdes canonical_host_name = host; 230157019Sdes else 231157019Sdes remote_ip = host; 232157019Sdes return host; 23357429Smarkm} 23457429Smarkm 23557429Smarkm/* 236113911Sdes * Returns the local/remote IP-address/hostname of socket as a string. 237113911Sdes * The returned string must be freed. 23857429Smarkm */ 23992559Sdesstatic char * 240137019Sdesget_socket_address(int sock, int remote, int flags) 24157429Smarkm{ 24276262Sgreen struct sockaddr_storage addr; 24376262Sgreen socklen_t addrlen; 24457429Smarkm char ntop[NI_MAXHOST]; 245147005Sdes int r; 24657429Smarkm 24776262Sgreen /* Get IP address of client. */ 24876262Sgreen addrlen = sizeof(addr); 24976262Sgreen memset(&addr, 0, sizeof(addr)); 25057429Smarkm 25176262Sgreen if (remote) { 252137019Sdes if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) 253106130Sdes < 0) 25476262Sgreen return NULL; 25576262Sgreen } else { 256137019Sdes if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) 257106130Sdes < 0) 25876262Sgreen return NULL; 25957429Smarkm } 260113911Sdes 261113911Sdes /* Work around Linux IPv6 weirdness */ 262113911Sdes if (addr.ss_family == AF_INET6) 263113911Sdes addrlen = sizeof(struct sockaddr_in6); 264113911Sdes 265147005Sdes ipv64_normalise_mapped(&addr, &addrlen); 266147005Sdes 26776262Sgreen /* Get the address in ascii. */ 268147005Sdes if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, 269147005Sdes sizeof(ntop), NULL, 0, flags)) != 0) { 270147005Sdes error("get_socket_address: getnameinfo %d failed: %s", flags, 271181111Sdes ssh_gai_strerror(r)); 27276262Sgreen return NULL; 27357429Smarkm } 27476262Sgreen return xstrdup(ntop); 27576262Sgreen} 27657429Smarkm 27776262Sgreenchar * 278137019Sdesget_peer_ipaddr(int sock) 27976262Sgreen{ 280106130Sdes char *p; 281106130Sdes 282137019Sdes if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) 283106130Sdes return p; 284106130Sdes return xstrdup("UNKNOWN"); 28576262Sgreen} 28657429Smarkm 28776262Sgreenchar * 288137019Sdesget_local_ipaddr(int sock) 28976262Sgreen{ 290106130Sdes char *p; 291106130Sdes 292137019Sdes if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) 293106130Sdes return p; 294106130Sdes return xstrdup("UNKNOWN"); 29557429Smarkm} 29657429Smarkm 29776262Sgreenchar * 298204917Sdesget_local_name(int fd) 29976262Sgreen{ 300204917Sdes char *host, myname[NI_MAXHOST]; 301204917Sdes 302204917Sdes /* Assume we were passed a socket */ 303204917Sdes if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL) 304204917Sdes return host; 305204917Sdes 306204917Sdes /* Handle the case where we were passed a pipe */ 307204917Sdes if (gethostname(myname, sizeof(myname)) == -1) { 308204917Sdes verbose("get_local_name: gethostname: %s", strerror(errno)); 309204917Sdes } else { 310204917Sdes host = xstrdup(myname); 311204917Sdes } 312204917Sdes 313204917Sdes return host; 31476262Sgreen} 31576262Sgreen 316197679Sdesvoid 317197679Sdesclear_cached_addr(void) 318197679Sdes{ 319255767Sdes free(canonical_host_ip); 320255767Sdes canonical_host_ip = NULL; 321197679Sdes cached_port = -1; 322197679Sdes} 323197679Sdes 32462101Sgreen/* 32576262Sgreen * Returns the IP-address of the remote host as a string. The returned 32676262Sgreen * string must not be freed. 32762101Sgreen */ 32862101Sgreen 32962101Sgreenconst char * 33092559Sdesget_remote_ipaddr(void) 33162101Sgreen{ 33276262Sgreen /* Check whether we have cached the ipaddr. */ 33376262Sgreen if (canonical_host_ip == NULL) { 33476262Sgreen if (packet_connection_is_on_socket()) { 33576262Sgreen canonical_host_ip = 33676262Sgreen get_peer_ipaddr(packet_get_connection_in()); 33776262Sgreen if (canonical_host_ip == NULL) 338126277Sdes cleanup_exit(255); 33976262Sgreen } else { 34076262Sgreen /* If not on socket, return UNKNOWN. */ 34176262Sgreen canonical_host_ip = xstrdup("UNKNOWN"); 34276262Sgreen } 34362101Sgreen } 34476262Sgreen return canonical_host_ip; 34576262Sgreen} 34662101Sgreen 34776262Sgreenconst char * 348124211Sdesget_remote_name_or_ip(u_int utmp_len, int use_dns) 34976262Sgreen{ 35076262Sgreen static const char *remote = ""; 35176262Sgreen if (utmp_len > 0) 352124211Sdes remote = get_canonical_hostname(use_dns); 35376262Sgreen if (utmp_len == 0 || strlen(remote) > utmp_len) 35476262Sgreen remote = get_remote_ipaddr(); 35576262Sgreen return remote; 35662101Sgreen} 35762101Sgreen 35857429Smarkm/* Returns the local/remote port for the socket. */ 35957429Smarkm 360192595Sdesint 36157429Smarkmget_sock_port(int sock, int local) 36257429Smarkm{ 36357429Smarkm struct sockaddr_storage from; 36457429Smarkm socklen_t fromlen; 36557429Smarkm char strport[NI_MAXSERV]; 366147005Sdes int r; 36757429Smarkm 36857429Smarkm /* Get IP address of client. */ 36957429Smarkm fromlen = sizeof(from); 37057429Smarkm memset(&from, 0, sizeof(from)); 37157429Smarkm if (local) { 37257429Smarkm if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) { 37357429Smarkm error("getsockname failed: %.100s", strerror(errno)); 37457429Smarkm return 0; 37557429Smarkm } 37657429Smarkm } else { 377113911Sdes if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) { 37857429Smarkm debug("getpeername failed: %.100s", strerror(errno)); 379149753Sdes return -1; 38057429Smarkm } 38157429Smarkm } 382113911Sdes 383113911Sdes /* Work around Linux IPv6 weirdness */ 384113911Sdes if (from.ss_family == AF_INET6) 385113911Sdes fromlen = sizeof(struct sockaddr_in6); 386113911Sdes 38757429Smarkm /* Return port number. */ 388147005Sdes if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, 389147005Sdes strport, sizeof(strport), NI_NUMERICSERV)) != 0) 390147005Sdes fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s", 391181111Sdes ssh_gai_strerror(r)); 39257429Smarkm return atoi(strport); 39357429Smarkm} 39457429Smarkm 39557429Smarkm/* Returns remote/local port number for the current connection. */ 39657429Smarkm 39792559Sdesstatic int 39857429Smarkmget_port(int local) 39957429Smarkm{ 40057429Smarkm /* 40157429Smarkm * If the connection is not a socket, return 65535. This is 40257429Smarkm * intentionally chosen to be an unprivileged port number. 40357429Smarkm */ 40457429Smarkm if (!packet_connection_is_on_socket()) 40557429Smarkm return 65535; 40657429Smarkm 40757429Smarkm /* Get socket and return the port number. */ 40857429Smarkm return get_sock_port(packet_get_connection_in(), local); 40957429Smarkm} 41057429Smarkm 41160573Skrisint 41257429Smarkmget_peer_port(int sock) 41357429Smarkm{ 41457429Smarkm return get_sock_port(sock, 0); 41557429Smarkm} 41657429Smarkm 41760573Skrisint 41892559Sdesget_remote_port(void) 41957429Smarkm{ 420137019Sdes /* Cache to avoid getpeername() on a dead connection */ 421197679Sdes if (cached_port == -1) 422197679Sdes cached_port = get_port(0); 423137019Sdes 424197679Sdes return cached_port; 42557429Smarkm} 42657429Smarkm 42757429Smarkmint 42892559Sdesget_local_port(void) 42957429Smarkm{ 43057429Smarkm return get_port(1); 43157429Smarkm} 432