crypto/openssh/canohost.c

   1 /* $OpenBSD: canohost.c,v 1.64 2009/02/12 03:00:56 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Functions for returning the canonical host name of the remote site.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  */
  14
  15 #include "includes.h"
  16
  17 #include <sys/types.h>
  18 #include <sys/socket.h>
  19
  20 #include <netinet/in.h>
  21 #include <arpa/inet.h>
  22
  23 #include <ctype.h>
  24 #include <errno.h>
  25 #include <netdb.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <stdarg.h>
  30
  31 #include "xmalloc.h"
  32 #include "packet.h"
  33 #include "log.h"
  34 #include "canohost.h"
  35 #include "misc.h"
  36
  37 static void check_ip_options(int, char *);
  38
  39 /*
  40  * Return the canonical name of the host at the other end of the socket. The
  41  * caller should free the returned string with xfree.
  42  */
  43
  44 static char *
  45 get_remote_hostname(int sock, int use_dns)
  46 {
  47         struct sockaddr_storage from;
  48         int i;
  49         socklen_t fromlen;
  50         struct addrinfo hints, *ai, *aitop;
  51         char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
  52
  53         /* Get IP address of client. */
  54         fromlen = sizeof(from);
  55         memset(&from, 0, sizeof(from));
  56         if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
  57                 debug("getpeername failed: %.100s", strerror(errno));
  58                 cleanup_exit(255);
  59         }
  60
  61         if (from.ss_family == AF_INET)
  62                 check_ip_options(sock, ntop);
  63
  64         ipv64_normalise_mapped(&from, &fromlen);
  65
  66         if (from.ss_family == AF_INET6)
  67                 fromlen = sizeof(struct sockaddr_in6);
  68
  69         if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
  70             NULL, 0, NI_NUMERICHOST) != 0)
  71                 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
  72
  73         if (!use_dns)
  74                 return xstrdup(ntop);
  75
  76         debug3("Trying to reverse map address %.100s.", ntop);
  77         /* Map the IP address to a host name. */
  78         if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
  79             NULL, 0, NI_NAMEREQD) != 0) {
  80                 /* Host name not found.  Use ip address. */
  81                 return xstrdup(ntop);
  82         }
  83
  84         /*
  85          * if reverse lookup result looks like a numeric hostname,
  86          * someone is trying to trick us by PTR record like following:
  87          *      1.1.1.10.in-addr.arpa.  IN PTR  2.3.4.5
  88          */
  89         memset(&hints, 0, sizeof(hints));
  90         hints.ai_socktype = SOCK_DGRAM; /*dummy*/
  91         hints.ai_flags = AI_NUMERICHOST;
  92         if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
  93                 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
  94                     name, ntop);
  95                 freeaddrinfo(ai);
  96                 return xstrdup(ntop);
  97         }
  98
  99         /*
 100          * Convert it to all lowercase (which is expected by the rest
 101          * of this software).
 102          */
 103         for (i = 0; name[i]; i++)
 104                 if (isupper(name[i]))
 105                         name[i] = (char)tolower(name[i]);
 106         /*
 107          * Map it back to an IP address and check that the given
 108          * address actually is an address of this host.  This is
 109          * necessary because anyone with access to a name server can
 110          * define arbitrary names for an IP address. Mapping from
 111          * name to IP address can be trusted better (but can still be
 112          * fooled if the intruder has access to the name server of
 113          * the domain).
 114          */
 115         memset(&hints, 0, sizeof(hints));
 116         hints.ai_family = from.ss_family;
 117         hints.ai_socktype = SOCK_STREAM;
 118         if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
 119                 logit("reverse mapping checking getaddrinfo for %.700s "
 120                     "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
 121                 return xstrdup(ntop);
 122         }
 123         /* Look for the address from the list of addresses. */
 124         for (ai = aitop; ai; ai = ai->ai_next) {
 125                 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
 126                     sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
 127                     (strcmp(ntop, ntop2) == 0))
 128                                 break;
 129         }
 130         freeaddrinfo(aitop);
 131         /* If we reached the end of the list, the address was not there. */
 132         if (!ai) {
 133                 /* Address not found for the host name. */
 134                 logit("Address %.100s maps to %.600s, but this does not "
 135                     "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
 136                     ntop, name);
 137                 return xstrdup(ntop);
 138         }
 139         return xstrdup(name);
 140 }
 141
 142 /*
 143  * If IP options are supported, make sure there are none (log and
 144  * disconnect them if any are found).  Basically we are worried about
 145  * source routing; it can be used to pretend you are somebody
 146  * (ip-address) you are not. That itself may be "almost acceptable"
 147  * under certain circumstances, but rhosts autentication is useless
 148  * if source routing is accepted. Notice also that if we just dropped
 149  * source routing here, the other side could use IP spoofing to do
 150  * rest of the interaction and could still bypass security.  So we
 151  * exit here if we detect any IP options.
 152  */
 153 /* IPv4 only */
 154 static void
 155 check_ip_options(int sock, char *ipaddr)
 156 {
 157 #ifdef IP_OPTIONS
 158         u_char options[200];
 159         char text[sizeof(options) * 3 + 1];
 160         socklen_t option_size;
 161         u_int i;
 162         int ipproto;
 163         struct protoent *ip;
 164
 165         if ((ip = getprotobyname("ip")) != NULL)
 166                 ipproto = ip->p_proto;
 167         else
 168                 ipproto = IPPROTO_IP;
 169         option_size = sizeof(options);
 170         if (getsockopt(sock, ipproto, IP_OPTIONS, options,
 171             &option_size) >= 0 && option_size != 0) {
 172                 text[0] = '\0';
 173                 for (i = 0; i < option_size; i++)
 174                         snprintf(text + i*3, sizeof(text) - i*3,
 175                             " %2.2x", options[i]);
 176                 fatal("Connection from %.100s with IP options:%.800s",
 177                     ipaddr, text);
 178         }
 179 #endif /* IP_OPTIONS */
 180 }
 181
 182 void
 183 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
 184 {
 185         struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
 186         struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
 187         struct in_addr inaddr;
 188         u_int16_t port;
 189
 190         if (addr->ss_family != AF_INET6 ||
 191             !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
 192                 return;
 193
 194         debug3("Normalising mapped IPv4 in IPv6 address");
 195
 196         memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
 197         port = a6->sin6_port;
 198
 199         memset(addr, 0, sizeof(*a4));
 200
 201         a4->sin_family = AF_INET;
 202         *len = sizeof(*a4);
 203         memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
 204         a4->sin_port = port;
 205 }
 206
 207 /*
 208  * Return the canonical name of the host in the other side of the current
 209  * connection.  The host name is cached, so it is efficient to call this
 210  * several times.
 211  */
 212
 213 const char *
 214 get_canonical_hostname(int use_dns)
 215 {
 216         char *host;
 217         static char *canonical_host_name = NULL;
 218         static char *remote_ip = NULL;
 219
 220         /* Check if we have previously retrieved name with same option. */
 221         if (use_dns && canonical_host_name != NULL)
 222                 return canonical_host_name;
 223         if (!use_dns && remote_ip != NULL)
 224                 return remote_ip;
 225
 226         /* Get the real hostname if socket; otherwise return UNKNOWN. */
 227         if (packet_connection_is_on_socket())
 228                 host = get_remote_hostname(packet_get_connection_in(), use_dns);
 229         else
 230                 host = "UNKNOWN";
 231
 232         if (use_dns)
 233                 canonical_host_name = host;
 234         else
 235                 remote_ip = host;
 236         return host;
 237 }
 238
 239 /*
 240  * Returns the local/remote IP-address/hostname of socket as a string.
 241  * The returned string must be freed.
 242  */
 243 static char *
 244 get_socket_address(int sock, int remote, int flags)
 245 {
 246         struct sockaddr_storage addr;
 247         socklen_t addrlen;
 248         char ntop[NI_MAXHOST];
 249         int r;
 250
 251         /* Get IP address of client. */
 252         addrlen = sizeof(addr);
 253         memset(&addr, 0, sizeof(addr));
 254
 255         if (remote) {
 256                 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
 257                     < 0)
 258                         return NULL;
 259         } else {
 260                 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
 261                     < 0)
 262                         return NULL;
 263         }
 264
 265         /* Work around Linux IPv6 weirdness */
 266         if (addr.ss_family == AF_INET6)
 267                 addrlen = sizeof(struct sockaddr_in6);
 268
 269         ipv64_normalise_mapped(&addr, &addrlen);
 270
 271         /* Get the address in ascii. */
 272         if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
 273             sizeof(ntop), NULL, 0, flags)) != 0) {
 274                 error("get_socket_address: getnameinfo %d failed: %s", flags,
 275                     ssh_gai_strerror(r));
 276                 return NULL;
 277         }
 278         return xstrdup(ntop);
 279 }
 280
 281 char *
 282 get_peer_ipaddr(int sock)
 283 {
 284         char *p;
 285
 286         if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
 287                 return p;
 288         return xstrdup("UNKNOWN");
 289 }
 290
 291 char *
 292 get_local_ipaddr(int sock)
 293 {
 294         char *p;
 295
 296         if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
 297                 return p;
 298         return xstrdup("UNKNOWN");
 299 }
 300
 301 char *
 302 get_local_name(int sock)
 303 {
 304         return get_socket_address(sock, 0, NI_NAMEREQD);
 305 }
 306
 307 /*
 308  * Returns the IP-address of the remote host as a string.  The returned
 309  * string must not be freed.
 310  */
 311
 312 const char *
 313 get_remote_ipaddr(void)
 314 {
 315         static char *canonical_host_ip = NULL;
 316
 317         /* Check whether we have cached the ipaddr. */
 318         if (canonical_host_ip == NULL) {
 319                 if (packet_connection_is_on_socket()) {
 320                         canonical_host_ip =
 321                             get_peer_ipaddr(packet_get_connection_in());
 322                         if (canonical_host_ip == NULL)
 323                                 cleanup_exit(255);
 324                 } else {
 325                         /* If not on socket, return UNKNOWN. */
 326                         canonical_host_ip = xstrdup("UNKNOWN");
 327                 }
 328         }
 329         return canonical_host_ip;
 330 }
 331
 332 const char *
 333 get_remote_name_or_ip(u_int utmp_len, int use_dns)
 334 {
 335         static const char *remote = "";
 336         if (utmp_len > 0)
 337                 remote = get_canonical_hostname(use_dns);
 338         if (utmp_len == 0 || strlen(remote) > utmp_len)
 339                 remote = get_remote_ipaddr();
 340         return remote;
 341 }
 342
 343 /* Returns the local/remote port for the socket. */
 344
 345 int
 346 get_sock_port(int sock, int local)
 347 {
 348         struct sockaddr_storage from;
 349         socklen_t fromlen;
 350         char strport[NI_MAXSERV];
 351         int r;
 352
 353         /* Get IP address of client. */
 354         fromlen = sizeof(from);
 355         memset(&from, 0, sizeof(from));
 356         if (local) {
 357                 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
 358                         error("getsockname failed: %.100s", strerror(errno));
 359                         return 0;
 360                 }
 361         } else {
 362                 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
 363                         debug("getpeername failed: %.100s", strerror(errno));
 364                         return -1;
 365                 }
 366         }
 367
 368         /* Work around Linux IPv6 weirdness */
 369         if (from.ss_family == AF_INET6)
 370                 fromlen = sizeof(struct sockaddr_in6);
 371
 372         /* Return port number. */
 373         if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
 374             strport, sizeof(strport), NI_NUMERICSERV)) != 0)
 375                 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
 376                     ssh_gai_strerror(r));
 377         return atoi(strport);
 378 }
 379
 380 /* Returns remote/local port number for the current connection. */
 381
 382 static int
 383 get_port(int local)
 384 {
 385         /*
 386          * If the connection is not a socket, return 65535.  This is
 387          * intentionally chosen to be an unprivileged port number.
 388          */
 389         if (!packet_connection_is_on_socket())
 390                 return 65535;
 391
 392         /* Get socket and return the port number. */
 393         return get_sock_port(packet_get_connection_in(), local);
 394 }
 395
 396 int
 397 get_peer_port(int sock)
 398 {
 399         return get_sock_port(sock, 0);
 400 }
 401
 402 int
 403 get_remote_port(void)
 404 {
 405         static int port = -1;
 406
 407         /* Cache to avoid getpeername() on a dead connection */
 408         if (port == -1)
 409                 port = get_port(0);
 410
 411         return port;
 412 }
 413
 414 int
 415 get_local_port(void)
 416 {
 417         return get_port(1);
 418 }