crypto/openssh-3.8.1p1/canohost.c

   1 /*
   2  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   3  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   4  *                    All rights reserved
   5  * Functions for returning the canonical host name of the remote site.
   6  *
   7  * As far as I am concerned, the code I have written for this software
   8  * can be used freely for any purpose.  Any derived versions of this
   9  * software must be clearly marked as such, and if the derived work is
  10  * incompatible with the protocol description in the RFC file, it must be
  11  * called by a name other than "ssh" or "Secure Shell".
  12  */
  13
  14 #include "includes.h"
  15 RCSID("$OpenBSD: canohost.c,v 1.38 2003/09/23 20:17:11 markus Exp $");
  16
  17 #include "packet.h"
  18 #include "xmalloc.h"
  19 #include "log.h"
  20 #include "canohost.h"
  21
  22 static void check_ip_options(int, char *);
  23 static void ipv64_normalise_mapped(struct sockaddr_storage *, socklen_t *);
  24
  25 /*
  26  * Return the canonical name of the host at the other end of the socket. The
  27  * caller should free the returned string with xfree.
  28  */
  29
  30 static char *
  31 get_remote_hostname(int socket, int use_dns)
  32 {
  33         struct sockaddr_storage from;
  34         int i;
  35         socklen_t fromlen;
  36         struct addrinfo hints, *ai, *aitop;
  37         char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
  38
  39         /* Get IP address of client. */
  40         fromlen = sizeof(from);
  41         memset(&from, 0, sizeof(from));
  42         if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0) {
  43                 debug("getpeername failed: %.100s", strerror(errno));
  44                 cleanup_exit(255);
  45         }
  46
  47         if (from.ss_family == AF_INET)
  48                 check_ip_options(socket, ntop);
  49
  50         ipv64_normalise_mapped(&from, &fromlen);
  51
  52         if (from.ss_family == AF_INET6)
  53                 fromlen = sizeof(struct sockaddr_in6);
  54
  55         if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
  56             NULL, 0, NI_NUMERICHOST) != 0)
  57                 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
  58
  59         if (!use_dns)
  60                 return xstrdup(ntop);
  61
  62         debug3("Trying to reverse map address %.100s.", ntop);
  63         /* Map the IP address to a host name. */
  64         if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
  65             NULL, 0, NI_NAMEREQD) != 0) {
  66                 /* Host name not found.  Use ip address. */
  67                 return xstrdup(ntop);
  68         }
  69
  70         /*
  71          * if reverse lookup result looks like a numeric hostname,
  72          * someone is trying to trick us by PTR record like following:
  73          *      1.1.1.10.in-addr.arpa.  IN PTR  2.3.4.5
  74          */
  75         memset(&hints, 0, sizeof(hints));
  76         hints.ai_socktype = SOCK_DGRAM; /*dummy*/
  77         hints.ai_flags = AI_NUMERICHOST;
  78         if (getaddrinfo(name, "0", &hints, &ai) == 0) {
  79                 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
  80                     name, ntop);
  81                 freeaddrinfo(ai);
  82                 return xstrdup(ntop);
  83         }
  84
  85         /*
  86          * Convert it to all lowercase (which is expected by the rest
  87          * of this software).
  88          */
  89         for (i = 0; name[i]; i++)
  90                 if (isupper(name[i]))
  91                         name[i] = tolower(name[i]);
  92         /*
  93          * Map it back to an IP address and check that the given
  94          * address actually is an address of this host.  This is
  95          * necessary because anyone with access to a name server can
  96          * define arbitrary names for an IP address. Mapping from
  97          * name to IP address can be trusted better (but can still be
  98          * fooled if the intruder has access to the name server of
  99          * the domain).
 100          */
 101         memset(&hints, 0, sizeof(hints));
 102         hints.ai_family = from.ss_family;
 103         hints.ai_socktype = SOCK_STREAM;
 104         if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
 105                 logit("reverse mapping checking getaddrinfo for %.700s "
 106                     "failed - POSSIBLE BREAKIN ATTEMPT!", name);
 107                 return xstrdup(ntop);
 108         }
 109         /* Look for the address from the list of addresses. */
 110         for (ai = aitop; ai; ai = ai->ai_next) {
 111                 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
 112                     sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
 113                     (strcmp(ntop, ntop2) == 0))
 114                                 break;
 115         }
 116         freeaddrinfo(aitop);
 117         /* If we reached the end of the list, the address was not there. */
 118         if (!ai) {
 119                 /* Address not found for the host name. */
 120                 logit("Address %.100s maps to %.600s, but this does not "
 121                     "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
 122                     ntop, name);
 123                 return xstrdup(ntop);
 124         }
 125         return xstrdup(name);
 126 }
 127
 128 /*
 129  * If IP options are supported, make sure there are none (log and
 130  * disconnect them if any are found).  Basically we are worried about
 131  * source routing; it can be used to pretend you are somebody
 132  * (ip-address) you are not. That itself may be "almost acceptable"
 133  * under certain circumstances, but rhosts autentication is useless
 134  * if source routing is accepted. Notice also that if we just dropped
 135  * source routing here, the other side could use IP spoofing to do
 136  * rest of the interaction and could still bypass security.  So we
 137  * exit here if we detect any IP options.
 138  */
 139 /* IPv4 only */
 140 static void
 141 check_ip_options(int socket, char *ipaddr)
 142 {
 143 #ifdef IP_OPTIONS
 144         u_char options[200];
 145         char text[sizeof(options) * 3 + 1];
 146         socklen_t option_size;
 147         int i, ipproto;
 148         struct protoent *ip;
 149
 150         if ((ip = getprotobyname("ip")) != NULL)
 151                 ipproto = ip->p_proto;
 152         else
 153                 ipproto = IPPROTO_IP;
 154         option_size = sizeof(options);
 155         if (getsockopt(socket, ipproto, IP_OPTIONS, options,
 156             &option_size) >= 0 && option_size != 0) {
 157                 text[0] = '\0';
 158                 for (i = 0; i < option_size; i++)
 159                         snprintf(text + i*3, sizeof(text) - i*3,
 160                             " %2.2x", options[i]);
 161                 logit("Connection from %.100s with IP options:%.800s",
 162                     ipaddr, text);
 163                 packet_disconnect("Connection from %.100s with IP options:%.800s",
 164                     ipaddr, text);
 165         }
 166 #endif /* IP_OPTIONS */
 167 }
 168
 169 static void
 170 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
 171 {
 172         struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
 173         struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
 174         struct in_addr inaddr;
 175         u_int16_t port;
 176
 177         if (addr->ss_family != AF_INET6 ||
 178             !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
 179                 return;
 180
 181         debug3("Normalising mapped IPv4 in IPv6 address");
 182
 183         memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
 184         port = a6->sin6_port;
 185
 186         memset(addr, 0, sizeof(*a4));
 187
 188         a4->sin_family = AF_INET;
 189         *len = sizeof(*a4);
 190         memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
 191         a4->sin_port = port;
 192 }
 193
 194 /*
 195  * Return the canonical name of the host in the other side of the current
 196  * connection.  The host name is cached, so it is efficient to call this
 197  * several times.
 198  */
 199
 200 const char *
 201 get_canonical_hostname(int use_dns)
 202 {
 203         static char *canonical_host_name = NULL;
 204         static int use_dns_done = 0;
 205
 206         /* Check if we have previously retrieved name with same option. */
 207         if (canonical_host_name != NULL) {
 208                 if (use_dns_done != use_dns)
 209                         xfree(canonical_host_name);
 210                 else
 211                         return canonical_host_name;
 212         }
 213
 214         /* Get the real hostname if socket; otherwise return UNKNOWN. */
 215         if (packet_connection_is_on_socket())
 216                 canonical_host_name = get_remote_hostname(
 217                     packet_get_connection_in(), use_dns);
 218         else
 219                 canonical_host_name = xstrdup("UNKNOWN");
 220
 221         use_dns_done = use_dns;
 222         return canonical_host_name;
 223 }
 224
 225 /*
 226  * Returns the local/remote IP-address/hostname of socket as a string.
 227  * The returned string must be freed.
 228  */
 229 static char *
 230 get_socket_address(int socket, int remote, int flags)
 231 {
 232         struct sockaddr_storage addr;
 233         socklen_t addrlen;
 234         char ntop[NI_MAXHOST];
 235
 236         /* Get IP address of client. */
 237         addrlen = sizeof(addr);
 238         memset(&addr, 0, sizeof(addr));
 239
 240         if (remote) {
 241                 if (getpeername(socket, (struct sockaddr *)&addr, &addrlen)
 242                     < 0)
 243                         return NULL;
 244         } else {
 245                 if (getsockname(socket, (struct sockaddr *)&addr, &addrlen)
 246                     < 0)
 247                         return NULL;
 248         }
 249
 250         /* Work around Linux IPv6 weirdness */
 251         if (addr.ss_family == AF_INET6)
 252                 addrlen = sizeof(struct sockaddr_in6);
 253
 254         /* Get the address in ascii. */
 255         if (getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop),
 256             NULL, 0, flags) != 0) {
 257                 error("get_socket_address: getnameinfo %d failed", flags);
 258                 return NULL;
 259         }
 260         return xstrdup(ntop);
 261 }
 262
 263 char *
 264 get_peer_ipaddr(int socket)
 265 {
 266         char *p;
 267
 268         if ((p = get_socket_address(socket, 1, NI_NUMERICHOST)) != NULL)
 269                 return p;
 270         return xstrdup("UNKNOWN");
 271 }
 272
 273 char *
 274 get_local_ipaddr(int socket)
 275 {
 276         char *p;
 277
 278         if ((p = get_socket_address(socket, 0, NI_NUMERICHOST)) != NULL)
 279                 return p;
 280         return xstrdup("UNKNOWN");
 281 }
 282
 283 char *
 284 get_local_name(int socket)
 285 {
 286         return get_socket_address(socket, 0, NI_NAMEREQD);
 287 }
 288
 289 /*
 290  * Returns the IP-address of the remote host as a string.  The returned
 291  * string must not be freed.
 292  */
 293
 294 const char *
 295 get_remote_ipaddr(void)
 296 {
 297         static char *canonical_host_ip = NULL;
 298
 299         /* Check whether we have cached the ipaddr. */
 300         if (canonical_host_ip == NULL) {
 301                 if (packet_connection_is_on_socket()) {
 302                         canonical_host_ip =
 303                             get_peer_ipaddr(packet_get_connection_in());
 304                         if (canonical_host_ip == NULL)
 305                                 cleanup_exit(255);
 306                 } else {
 307                         /* If not on socket, return UNKNOWN. */
 308                         canonical_host_ip = xstrdup("UNKNOWN");
 309                 }
 310         }
 311         return canonical_host_ip;
 312 }
 313
 314 const char *
 315 get_remote_name_or_ip(u_int utmp_len, int use_dns)
 316 {
 317         static const char *remote = "";
 318         if (utmp_len > 0)
 319                 remote = get_canonical_hostname(use_dns);
 320         if (utmp_len == 0 || strlen(remote) > utmp_len)
 321                 remote = get_remote_ipaddr();
 322         return remote;
 323 }
 324
 325 /* Returns the local/remote port for the socket. */
 326
 327 static int
 328 get_sock_port(int sock, int local)
 329 {
 330         struct sockaddr_storage from;
 331         socklen_t fromlen;
 332         char strport[NI_MAXSERV];
 333
 334         /* Get IP address of client. */
 335         fromlen = sizeof(from);
 336         memset(&from, 0, sizeof(from));
 337         if (local) {
 338                 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
 339                         error("getsockname failed: %.100s", strerror(errno));
 340                         return 0;
 341                 }
 342         } else {
 343                 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
 344                         debug("getpeername failed: %.100s", strerror(errno));
 345                         cleanup_exit(255);
 346                 }
 347         }
 348
 349         /* Work around Linux IPv6 weirdness */
 350         if (from.ss_family == AF_INET6)
 351                 fromlen = sizeof(struct sockaddr_in6);
 352
 353         /* Return port number. */
 354         if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
 355             strport, sizeof(strport), NI_NUMERICSERV) != 0)
 356                 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
 357         return atoi(strport);
 358 }
 359
 360 /* Returns remote/local port number for the current connection. */
 361
 362 static int
 363 get_port(int local)
 364 {
 365         /*
 366          * If the connection is not a socket, return 65535.  This is
 367          * intentionally chosen to be an unprivileged port number.
 368          */
 369         if (!packet_connection_is_on_socket())
 370                 return 65535;
 371
 372         /* Get socket and return the port number. */
 373         return get_sock_port(packet_get_connection_in(), local);
 374 }
 375
 376 int
 377 get_peer_port(int sock)
 378 {
 379         return get_sock_port(sock, 0);
 380 }
 381
 382 int
 383 get_remote_port(void)
 384 {
 385         return get_port(0);
 386 }
 387
 388 int
 389 get_local_port(void)
 390 {
 391         return get_port(1);
 392 }