crypto/external/bsd/openssh/dist/canohost.c

   1 /*      $NetBSD: canohost.c,v 1.1.1.2 2009/12/27 01:06:50 christos Exp $        */
   2 /* $OpenBSD: canohost.c,v 1.65 2009/05/27 06:31:25 andreas Exp $ */
   3 /*
   4  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   5  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   6  *                    All rights reserved
   7  * Functions for returning the canonical host name of the remote site.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  */
  15
  16 #include "includes.h"
  17 __RCSID("$NetBSD: canohost.c,v 1.2 2009/06/07 22:38:46 christos Exp $");
  18 #include <sys/types.h>
  19 #include <sys/socket.h>
  20
  21 #include <netinet/in.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 #include <time.h>
  31
  32 #include "xmalloc.h"
  33 #include "packet.h"
  34 #include "log.h"
  35 #include "canohost.h"
  36 #include "misc.h"
  37
  38 static void check_ip_options(int, char *);
  39 static char *canonical_host_ip = NULL;
  40 static int cached_port = -1;
  41
  42 /*
  43  * Return the canonical name of the host at the other end of the socket. The
  44  * caller should free the returned string with xfree.
  45  */
  46
  47 static char *
  48 get_remote_hostname(int sock, int use_dns)
  49 {
  50         struct sockaddr_storage from;
  51         int i;
  52         socklen_t fromlen;
  53         struct addrinfo hints, *ai, *aitop;
  54         char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
  55
  56         /* Get IP address of client. */
  57         fromlen = sizeof(from);
  58         memset(&from, 0, sizeof(from));
  59         if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
  60                 debug("getpeername failed: %.100s", strerror(errno));
  61                 cleanup_exit(255);
  62         }
  63
  64         if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
  65             NULL, 0, NI_NUMERICHOST) != 0)
  66                 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
  67
  68         if (from.ss_family == AF_INET)
  69                 check_ip_options(sock, ntop);
  70
  71         if (!use_dns)
  72                 return xstrdup(ntop);
  73
  74         debug3("Trying to reverse map address %.100s.", ntop);
  75         /* Map the IP address to a host name. */
  76         if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
  77             NULL, 0, NI_NAMEREQD) != 0) {
  78                 /* Host name not found.  Use ip address. */
  79                 return xstrdup(ntop);
  80         }
  81
  82         /*
  83          * if reverse lookup result looks like a numeric hostname,
  84          * someone is trying to trick us by PTR record like following:
  85          *      1.1.1.10.in-addr.arpa.  IN PTR  2.3.4.5
  86          */
  87         memset(&hints, 0, sizeof(hints));
  88         hints.ai_socktype = SOCK_DGRAM; /*dummy*/
  89         hints.ai_flags = AI_NUMERICHOST;
  90         if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
  91                 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
  92                     name, ntop);
  93                 freeaddrinfo(ai);
  94                 return xstrdup(ntop);
  95         }
  96
  97         /*
  98          * Convert it to all lowercase (which is expected by the rest
  99          * of this software).
 100          */
 101         for (i = 0; name[i]; i++)
 102                 if (isupper((unsigned char)name[i]))
 103                         name[i] = (char)tolower((unsigned char)name[i]);
 104         /*
 105          * Map it back to an IP address and check that the given
 106          * address actually is an address of this host.  This is
 107          * necessary because anyone with access to a name server can
 108          * define arbitrary names for an IP address. Mapping from
 109          * name to IP address can be trusted better (but can still be
 110          * fooled if the intruder has access to the name server of
 111          * the domain).
 112          */
 113         memset(&hints, 0, sizeof(hints));
 114         hints.ai_family = from.ss_family;
 115         hints.ai_socktype = SOCK_STREAM;
 116         if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
 117                 logit("reverse mapping checking getaddrinfo for %.700s "
 118                     "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
 119                 return xstrdup(ntop);
 120         }
 121         /* Look for the address from the list of addresses. */
 122         for (ai = aitop; ai; ai = ai->ai_next) {
 123                 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
 124                     sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
 125                     (strcmp(ntop, ntop2) == 0))
 126                                 break;
 127         }
 128         freeaddrinfo(aitop);
 129         /* If we reached the end of the list, the address was not there. */
 130         if (!ai) {
 131                 /* Address not found for the host name. */
 132                 logit("Address %.100s maps to %.600s, but this does not "
 133                     "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
 134                     ntop, name);
 135                 return xstrdup(ntop);
 136         }
 137         return xstrdup(name);
 138 }
 139
 140 /*
 141  * If IP options are supported, make sure there are none (log and
 142  * disconnect them if any are found).  Basically we are worried about
 143  * source routing; it can be used to pretend you are somebody
 144  * (ip-address) you are not. That itself may be "almost acceptable"
 145  * under certain circumstances, but rhosts autentication is useless
 146  * if source routing is accepted. Notice also that if we just dropped
 147  * source routing here, the other side could use IP spoofing to do
 148  * rest of the interaction and could still bypass security.  So we
 149  * exit here if we detect any IP options.
 150  */
 151 /* IPv4 only */
 152 static void
 153 check_ip_options(int sock, char *ipaddr)
 154 {
 155         u_char options[200];
 156         char text[sizeof(options) * 3 + 1];
 157         socklen_t option_size;
 158         u_int i;
 159         int ipproto;
 160         struct protoent *ip;
 161
 162         if ((ip = getprotobyname("ip")) != NULL)
 163                 ipproto = ip->p_proto;
 164         else
 165                 ipproto = IPPROTO_IP;
 166         option_size = sizeof(options);
 167         if (getsockopt(sock, ipproto, IP_OPTIONS, options,
 168             &option_size) >= 0 && option_size != 0) {
 169                 text[0] = '\0';
 170                 for (i = 0; i < option_size; i++)
 171                         snprintf(text + i*3, sizeof(text) - i*3,
 172                             " %2.2x", options[i]);
 173                 fatal("Connection from %.100s with IP options:%.800s",
 174                     ipaddr, text);
 175         }
 176 }
 177
 178 /*
 179  * Return the canonical name of the host in the other side of the current
 180  * connection.  The host name is cached, so it is efficient to call this
 181  * several times.
 182  */
 183
 184 const char *
 185 get_canonical_hostname(int use_dns)
 186 {
 187         char *host;
 188         static char *canonical_host_name = NULL;
 189         static char *remote_ip = NULL;
 190
 191         /* Check if we have previously retrieved name with same option. */
 192         if (use_dns && canonical_host_name != NULL)
 193                 return canonical_host_name;
 194         if (!use_dns && remote_ip != NULL)
 195                 return remote_ip;
 196
 197         /* Get the real hostname if socket; otherwise return UNKNOWN. */
 198         if (packet_connection_is_on_socket())
 199                 host = get_remote_hostname(packet_get_connection_in(), use_dns);
 200         else
 201                 host = "UNKNOWN";
 202
 203         if (use_dns)
 204                 canonical_host_name = host;
 205         else
 206                 remote_ip = host;
 207         return host;
 208 }
 209
 210 /*
 211  * Returns the local/remote IP-address/hostname of socket as a string.
 212  * The returned string must be freed.
 213  */
 214 static char *
 215 get_socket_address(int sock, int remote, int flags)
 216 {
 217         struct sockaddr_storage addr;
 218         socklen_t addrlen;
 219         char ntop[NI_MAXHOST];
 220         int r;
 221
 222         /* Get IP address of client. */
 223         addrlen = sizeof(addr);
 224         memset(&addr, 0, sizeof(addr));
 225
 226         if (remote) {
 227                 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
 228                     < 0)
 229                         return NULL;
 230         } else {
 231                 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
 232                     < 0)
 233                         return NULL;
 234         }
 235         /* Get the address in ascii. */
 236         if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
 237             sizeof(ntop), NULL, 0, flags)) != 0) {
 238                 error("get_socket_address: getnameinfo %d failed: %s", flags,
 239                     ssh_gai_strerror(r));
 240                 return NULL;
 241         }
 242         return xstrdup(ntop);
 243 }
 244
 245 char *
 246 get_peer_ipaddr(int sock)
 247 {
 248         char *p;
 249
 250         if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
 251                 return p;
 252         return xstrdup("UNKNOWN");
 253 }
 254
 255 char *
 256 get_local_ipaddr(int sock)
 257 {
 258         char *p;
 259
 260         if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
 261                 return p;
 262         return xstrdup("UNKNOWN");
 263 }
 264
 265 char *
 266 get_local_name(int sock)
 267 {
 268         return get_socket_address(sock, 0, NI_NAMEREQD);
 269 }
 270
 271 void
 272 clear_cached_addr(void)
 273 {
 274         if (canonical_host_ip != NULL) {
 275                 xfree(canonical_host_ip);
 276                 canonical_host_ip = NULL;
 277         }
 278         cached_port = -1;
 279 }
 280
 281 /*
 282  * Returns the IP-address of the remote host as a string.  The returned
 283  * string must not be freed.
 284  */
 285
 286 const char *
 287 get_remote_ipaddr(void)
 288 {
 289         /* Check whether we have cached the ipaddr. */
 290         if (canonical_host_ip == NULL) {
 291                 if (packet_connection_is_on_socket()) {
 292                         canonical_host_ip =
 293                             get_peer_ipaddr(packet_get_connection_in());
 294                         if (canonical_host_ip == NULL)
 295                                 cleanup_exit(255);
 296                 } else {
 297                         /* If not on socket, return UNKNOWN. */
 298                         canonical_host_ip = xstrdup("UNKNOWN");
 299                 }
 300         }
 301         return canonical_host_ip;
 302 }
 303
 304 const char *
 305 get_remote_name_or_ip(u_int utmp_len, int use_dns)
 306 {
 307         static const char *remote = "";
 308         if (utmp_len > 0)
 309                 remote = get_canonical_hostname(use_dns);
 310         if (utmp_len == 0 || strlen(remote) > utmp_len)
 311                 remote = get_remote_ipaddr();
 312         return remote;
 313 }
 314
 315 /* Returns the local/remote port for the socket. */
 316
 317 int
 318 get_sock_port(int sock, int local)
 319 {
 320         struct sockaddr_storage from;
 321         socklen_t fromlen;
 322         char strport[NI_MAXSERV];
 323         int r;
 324
 325         /* Get IP address of client. */
 326         fromlen = sizeof(from);
 327         memset(&from, 0, sizeof(from));
 328         if (local) {
 329                 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
 330                         error("getsockname failed: %.100s", strerror(errno));
 331                         return 0;
 332                 }
 333         } else {
 334                 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
 335                         debug("getpeername failed: %.100s", strerror(errno));
 336                         return -1;
 337                 }
 338         }
 339         /* Return port number. */
 340         if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
 341             strport, sizeof(strport), NI_NUMERICSERV)) != 0)
 342                 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
 343                     ssh_gai_strerror(r));
 344         return atoi(strport);
 345 }
 346
 347 /* Returns remote/local port number for the current connection. */
 348
 349 static int
 350 get_port(int local)
 351 {
 352         /*
 353          * If the connection is not a socket, return 65535.  This is
 354          * intentionally chosen to be an unprivileged port number.
 355          */
 356         if (!packet_connection_is_on_socket())
 357                 return 65535;
 358
 359         /* Get socket and return the port number. */
 360         return get_sock_port(packet_get_connection_in(), local);
 361 }
 362
 363 int
 364 get_peer_port(int sock)
 365 {
 366         return get_sock_port(sock, 0);
 367 }
 368
 369 int
 370 get_remote_port(void)
 371 {
 372         /* Cache to avoid getpeername() on a dead connection */
 373         if (cached_port == -1)
 374                 cached_port = get_port(0);
 375
 376         return cached_port;
 377 }
 378
 379 int
 380 get_local_port(void)
 381 {
 382         return get_port(1);
 383 }