crypto/openssh-4/canohost.c

   1 /* $OpenBSD: canohost.c,v 1.61 2006/08/03 03:34:41 deraadt 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
  36 static void check_ip_options(int, char *);
  37
  38 /*
  39  * Return the canonical name of the host at the other end of the socket. The
  40  * caller should free the returned string with xfree.
  41  */
  42
  43 static char *
  44 get_remote_hostname(int sock, int use_dns)
  45 {
  46         struct sockaddr_storage from;
  47         int i;
  48         socklen_t fromlen;
  49         struct addrinfo hints, *ai, *aitop;
  50         char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
  51
  52         /* Get IP address of client. */
  53         fromlen = sizeof(from);
  54         memset(&from, 0, sizeof(from));
  55         if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
  56                 debug("getpeername failed: %.100s", strerror(errno));
  57                 cleanup_exit(255);
  58         }
  59
  60         if (from.ss_family == AF_INET)
  61                 check_ip_options(sock, ntop);
  62
  63         ipv64_normalise_mapped(&from, &fromlen);
  64
  65         if (from.ss_family == AF_INET6)
  66                 fromlen = sizeof(struct sockaddr_in6);
  67
  68         if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
  69             NULL, 0, NI_NUMERICHOST) != 0)
  70                 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
  71
  72         if (!use_dns)
  73                 return xstrdup(ntop);
  74
  75         debug3("Trying to reverse map address %.100s.", ntop);
  76         /* Map the IP address to a host name. */
  77         if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
  78             NULL, 0, NI_NAMEREQD) != 0) {
  79                 /* Host name not found.  Use ip address. */
  80                 return xstrdup(ntop);
  81         }
  82
  83         /*
  84          * if reverse lookup result looks like a numeric hostname,
  85          * someone is trying to trick us by PTR record like following:
  86          *      1.1.1.10.in-addr.arpa.  IN PTR  2.3.4.5
  87          */
  88         memset(&hints, 0, sizeof(hints));
  89         hints.ai_socktype = SOCK_DGRAM; /*dummy*/
  90         hints.ai_flags = AI_NUMERICHOST;
  91         if (getaddrinfo(name, "0", &hints, &ai) == 0) {
  92                 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
  93                     name, ntop);
  94                 freeaddrinfo(ai);
  95                 return xstrdup(ntop);
  96         }
  97
  98         /*
  99          * Convert it to all lowercase (which is expected by the rest
 100          * of this software).
 101          */
 102         for (i = 0; name[i]; i++)
 103                 if (isupper(name[i]))
 104                         name[i] = (char)tolower(name[i]);
 105         /*
 106          * Map it back to an IP address and check that the given
 107          * address actually is an address of this host.  This is
 108          * necessary because anyone with access to a name server can
 109          * define arbitrary names for an IP address. Mapping from
 110          * name to IP address can be trusted better (but can still be
 111          * fooled if the intruder has access to the name server of
 112          * the domain).
 113          */
 114         memset(&hints, 0, sizeof(hints));
 115         hints.ai_family = from.ss_family;
 116         hints.ai_socktype = SOCK_STREAM;
 117         if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
 118                 logit("reverse mapping checking getaddrinfo for %.700s "
 119                     "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
 120                 return xstrdup(ntop);
 121         }
 122         /* Look for the address from the list of addresses. */
 123         for (ai = aitop; ai; ai = ai->ai_next) {
 124                 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
 125                     sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
 126                     (strcmp(ntop, ntop2) == 0))
 127                                 break;
 128         }
 129         freeaddrinfo(aitop);
 130         /* If we reached the end of the list, the address was not there. */
 131         if (!ai) {
 132                 /* Address not found for the host name. */
 133                 logit("Address %.100s maps to %.600s, but this does not "
 134                     "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
 135                     ntop, name);
 136                 return xstrdup(ntop);
 137         }
 138         return xstrdup(name);
 139 }
 140
 141 /*
 142  * If IP options are supported, make sure there are none (log and
 143  * disconnect them if any are found).  Basically we are worried about
 144  * source routing; it can be used to pretend you are somebody
 145  * (ip-address) you are not. That itself may be "almost acceptable"
 146  * under certain circumstances, but rhosts autentication is useless
 147  * if source routing is accepted. Notice also that if we just dropped
 148  * source routing here, the other side could use IP spoofing to do
 149  * rest of the interaction and could still bypass security.  So we
 150  * exit here if we detect any IP options.
 151  */
 152 /* IPv4 only */
 153 static void
 154 check_ip_options(int sock, char *ipaddr)
 155 {
 156 #ifdef IP_OPTIONS
 157         u_char options[200];
 158         char text[sizeof(options) * 3 + 1];
 159         socklen_t option_size;
 160         u_int i;
 161         int ipproto;
 162         struct protoent *ip;
 163
 164         if ((ip = getprotobyname("ip")) != NULL)
 165                 ipproto = ip->p_proto;
 166         else
 167                 ipproto = IPPROTO_IP;
 168         option_size = sizeof(options);
 169         if (getsockopt(sock, ipproto, IP_OPTIONS, options,
 170             &option_size) >= 0 && option_size != 0) {
 171                 text[0] = '\0';
 172                 for (i = 0; i < option_size; i++)
 173                         snprintf(text + i*3, sizeof(text) - i*3,
 174                             " %2.2x", options[i]);
 175                 fatal("Connection from %.100s with IP options:%.800s",
 176                     ipaddr, text);
 177         }
 178 #endif /* IP_OPTIONS */
 179 }
 180
 181 void
 182 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
 183 {
 184         struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
 185         struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
 186         struct in_addr inaddr;
 187         u_int16_t port;
 188
 189         if (addr->ss_family != AF_INET6 ||
 190             !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
 191                 return;
 192
 193         debug3("Normalising mapped IPv4 in IPv6 address");
 194
 195         memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
 196         port = a6->sin6_port;
 197
 198         memset(addr, 0, sizeof(*a4));
 199
 200         a4->sin_family = AF_INET;
 201         *len = sizeof(*a4);
 202         memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
 203         a4->sin_port = port;
 204 }
 205
 206 /*
 207  * Return the canonical name of the host in the other side of the current
 208  * connection.  The host name is cached, so it is efficient to call this
 209  * several times.
 210  */
 211
 212 const char *
 213 get_canonical_hostname(int use_dns)
 214 {
 215         char *host;
 216         static char *canonical_host_name = NULL;
 217         static char *remote_ip = NULL;
 218
 219         /* Check if we have previously retrieved name with same option. */
 220         if (use_dns && canonical_host_name != NULL)
 221                 return canonical_host_name;
 222         if (!use_dns && remote_ip != NULL)
 223                 return remote_ip;
 224
 225         /* Get the real hostname if socket; otherwise return UNKNOWN. */
 226         if (packet_connection_is_on_socket())
 227                 host = get_remote_hostname(packet_get_connection_in(), use_dns);
 228         else
 229                 host = "UNKNOWN";
 230
 231         if (use_dns)
 232                 canonical_host_name = host;
 233         else
 234                 remote_ip = host;
 235         return host;
 236 }
 237
 238 /*
 239  * Returns the local/remote IP-address/hostname of socket as a string.
 240  * The returned string must be freed.
 241  */
 242 static char *
 243 get_socket_address(int sock, int remote, int flags)
 244 {
 245         struct sockaddr_storage addr;
 246         socklen_t addrlen;
 247         char ntop[NI_MAXHOST];
 248         int r;
 249
 250         /* Get IP address of client. */
 251         addrlen = sizeof(addr);
 252         memset(&addr, 0, sizeof(addr));
 253
 254         if (remote) {
 255                 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
 256                     < 0)
 257                         return NULL;
 258         } else {
 259                 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
 260                     < 0)
 261                         return NULL;
 262         }
 263
 264         /* Work around Linux IPv6 weirdness */
 265         if (addr.ss_family == AF_INET6)
 266                 addrlen = sizeof(struct sockaddr_in6);
 267
 268         ipv64_normalise_mapped(&addr, &addrlen);
 269
 270         /* Get the address in ascii. */
 271         if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
 272             sizeof(ntop), NULL, 0, flags)) != 0) {
 273                 error("get_socket_address: getnameinfo %d failed: %s", flags,
 274                     r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
 275                 return NULL;
 276         }
 277         return xstrdup(ntop);
 278 }
 279
 280 char *
 281 get_peer_ipaddr(int sock)
 282 {
 283         char *p;
 284
 285         if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
 286                 return p;
 287         return xstrdup("UNKNOWN");
 288 }
 289
 290 char *
 291 get_local_ipaddr(int sock)
 292 {
 293         char *p;
 294
 295         if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
 296                 return p;
 297         return xstrdup("UNKNOWN");
 298 }
 299
 300 char *
 301 get_local_name(int sock)
 302 {
 303         return get_socket_address(sock, 0, NI_NAMEREQD);
 304 }
 305
 306 /*
 307  * Returns the IP-address of the remote host as a string.  The returned
 308  * string must not be freed.
 309  */
 310
 311 const char *
 312 get_remote_ipaddr(void)
 313 {
 314         static char *canonical_host_ip = NULL;
 315
 316         /* Check whether we have cached the ipaddr. */
 317         if (canonical_host_ip == NULL) {
 318                 if (packet_connection_is_on_socket()) {
 319                         canonical_host_ip =
 320                             get_peer_ipaddr(packet_get_connection_in());
 321                         if (canonical_host_ip == NULL)
 322                                 cleanup_exit(255);
 323                 } else {
 324                         /* If not on socket, return UNKNOWN. */
 325                         canonical_host_ip = xstrdup("UNKNOWN");
 326                 }
 327         }
 328         return canonical_host_ip;
 329 }
 330
 331 const char *
 332 get_remote_name_or_ip(u_int utmp_len, int use_dns)
 333 {
 334         static const char *remote = "";
 335         if (utmp_len > 0)
 336                 remote = get_canonical_hostname(use_dns);
 337         if (utmp_len == 0 || strlen(remote) > utmp_len)
 338                 remote = get_remote_ipaddr();
 339         return remote;
 340 }
 341
 342 /* Returns the local/remote port for the socket. */
 343
 344 static int
 345 get_sock_port(int sock, int local)
 346 {
 347         struct sockaddr_storage from;
 348         socklen_t fromlen;
 349         char strport[NI_MAXSERV];
 350         int r;
 351
 352         /* Get IP address of client. */
 353         fromlen = sizeof(from);
 354         memset(&from, 0, sizeof(from));
 355         if (local) {
 356                 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
 357                         error("getsockname failed: %.100s", strerror(errno));
 358                         return 0;
 359                 }
 360         } else {
 361                 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
 362                         debug("getpeername failed: %.100s", strerror(errno));
 363                         return -1;
 364                 }
 365         }
 366
 367         /* Work around Linux IPv6 weirdness */
 368         if (from.ss_family == AF_INET6)
 369                 fromlen = sizeof(struct sockaddr_in6);
 370
 371         /* Return port number. */
 372         if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
 373             strport, sizeof(strport), NI_NUMERICSERV)) != 0)
 374                 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
 375                     r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
 376         return atoi(strport);
 377 }
 378
 379 /* Returns remote/local port number for the current connection. */
 380
 381 static int
 382 get_port(int local)
 383 {
 384         /*
 385          * If the connection is not a socket, return 65535.  This is
 386          * intentionally chosen to be an unprivileged port number.
 387          */
 388         if (!packet_connection_is_on_socket())
 389                 return 65535;
 390
 391         /* Get socket and return the port number. */
 392         return get_sock_port(packet_get_connection_in(), local);
 393 }
 394
 395 int
 396 get_peer_port(int sock)
 397 {
 398         return get_sock_port(sock, 0);
 399 }
 400
 401 int
 402 get_remote_port(void)
 403 {
 404         static int port = -1;
 405
 406         /* Cache to avoid getpeername() on a dead connection */
 407         if (port == -1)
 408                 port = get_port(0);
 409
 410         return port;
 411 }
 412
 413 int
 414 get_local_port(void)
 415 {
 416         return get_port(1);
 417 }