clientname.c

   1 /*
   2  * Functions for looking up the remote name or addr of a socket.
   3  *
   4  * Copyright (C) 1992-2001 Andrew Tridgell <tridge@samba.org>
   5  * Copyright (C) 2001, 2002 Martin Pool <mbp@samba.org>
   6  * Copyright (C) 2002-2009 Wayne Davison
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 3 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, visit the http://fsf.org website.
  20  */
  21
  22 /*
  23  * This file is now converted to use the new-style getaddrinfo()
  24  * interface, which supports IPv6 but is also supported on recent
  25  * IPv4-only machines.  On systems that don't have that interface, we
  26  * emulate it using the KAME implementation.
  27  */
  28
  29 #include "rsync.h"
  30
  31 static const char default_name[] = "UNKNOWN";
  32 extern int am_server;
  33
  34
  35 /**
  36  * Return the IP addr of the client as a string
  37  **/
  38 char *client_addr(int fd)
  39 {
  40         static char addr_buf[100];
  41         static int initialised;
  42         struct sockaddr_storage ss;
  43         socklen_t length = sizeof ss;
  44         char *ssh_info, *p;
  45
  46         if (initialised)
  47                 return addr_buf;
  48
  49         initialised = 1;
  50
  51         if (am_server) {        /* daemon over --rsh mode */
  52                 strlcpy(addr_buf, "0.0.0.0", sizeof addr_buf);
  53                 if ((ssh_info = getenv("SSH_CONNECTION")) != NULL
  54                     || (ssh_info = getenv("SSH_CLIENT")) != NULL
  55                     || (ssh_info = getenv("SSH2_CLIENT")) != NULL) {
  56                         strlcpy(addr_buf, ssh_info, sizeof addr_buf);
  57                         /* Truncate the value to just the IP address. */
  58                         if ((p = strchr(addr_buf, ' ')) != NULL)
  59                                 *p = '\0';
  60                 }
  61         } else {
  62                 client_sockaddr(fd, &ss, &length);
  63                 getnameinfo((struct sockaddr *)&ss, length,
  64                             addr_buf, sizeof addr_buf, NULL, 0, NI_NUMERICHOST);
  65         }
  66
  67         return addr_buf;
  68 }
  69
  70
  71 static int get_sockaddr_family(const struct sockaddr_storage *ss)
  72 {
  73         return ((struct sockaddr *) ss)->sa_family;
  74 }
  75
  76
  77 /**
  78  * Return the DNS name of the client.
  79  *
  80  * The name is statically cached so that repeated lookups are quick,
  81  * so there is a limit of one lookup per customer.
  82  *
  83  * If anything goes wrong, including the name->addr->name check, then
  84  * we just use "UNKNOWN", so you can use that value in hosts allow
  85  * lines.
  86  *
  87  * After translation from sockaddr to name we do a forward lookup to
  88  * make sure nobody is spoofing PTR records.
  89  **/
  90 char *client_name(int fd)
  91 {
  92         static char name_buf[100];
  93         static char port_buf[100];
  94         static int initialised;
  95         struct sockaddr_storage ss;
  96         socklen_t ss_len;
  97
  98         if (initialised)
  99                 return name_buf;
 100
 101         strlcpy(name_buf, default_name, sizeof name_buf);
 102         initialised = 1;
 103
 104         memset(&ss, 0, sizeof ss);
 105
 106         if (am_server) {        /* daemon over --rsh mode */
 107                 char *addr = client_addr(fd);
 108                 struct addrinfo hint, *answer;
 109                 int err;
 110
 111                 if (strcmp(addr, "0.0.0.0") == 0)
 112                         return name_buf;
 113
 114                 memset(&hint, 0, sizeof hint);
 115
 116 #ifdef AI_NUMERICHOST
 117                 hint.ai_flags = AI_NUMERICHOST;
 118 #endif
 119                 hint.ai_socktype = SOCK_STREAM;
 120
 121                 if ((err = getaddrinfo(addr, NULL, &hint, &answer)) != 0) {
 122                         rprintf(FLOG, "malformed address %s: %s\n",
 123                                 addr, gai_strerror(err));
 124                         return name_buf;
 125                 }
 126
 127                 switch (answer->ai_family) {
 128                 case AF_INET:
 129                         ss_len = sizeof (struct sockaddr_in);
 130                         memcpy(&ss, answer->ai_addr, ss_len);
 131                         break;
 132 #ifdef INET6
 133                 case AF_INET6:
 134                         ss_len = sizeof (struct sockaddr_in6);
 135                         memcpy(&ss, answer->ai_addr, ss_len);
 136                         break;
 137 #endif
 138                 default:
 139                         exit_cleanup(RERR_SOCKETIO);
 140                 }
 141                 freeaddrinfo(answer);
 142         } else {
 143                 ss_len = sizeof ss;
 144                 client_sockaddr(fd, &ss, &ss_len);
 145         }
 146
 147         if (lookup_name(fd, &ss, ss_len, name_buf, sizeof name_buf,
 148                         port_buf, sizeof port_buf) == 0)
 149                 check_name(fd, &ss, name_buf, sizeof name_buf);
 150
 151         return name_buf;
 152 }
 153
 154
 155
 156 /**
 157  * Get the sockaddr for the client.
 158  *
 159  * If it comes in as an ipv4 address mapped into IPv6 format then we
 160  * convert it back to a regular IPv4.
 161  **/
 162 void client_sockaddr(int fd,
 163                      struct sockaddr_storage *ss,
 164                      socklen_t *ss_len)
 165 {
 166         memset(ss, 0, sizeof *ss);
 167
 168         if (getpeername(fd, (struct sockaddr *) ss, ss_len)) {
 169                 /* FIXME: Can we really not continue? */
 170                 rsyserr(FLOG, errno, "getpeername on fd%d failed", fd);
 171                 exit_cleanup(RERR_SOCKETIO);
 172         }
 173
 174 #ifdef INET6
 175         if (get_sockaddr_family(ss) == AF_INET6 &&
 176             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)ss)->sin6_addr)) {
 177                 /* OK, so ss is in the IPv6 family, but it is really
 178                  * an IPv4 address: something like
 179                  * "::ffff:10.130.1.2".  If we use it as-is, then the
 180                  * reverse lookup might fail or perhaps something else
 181                  * bad might happen.  So instead we convert it to an
 182                  * equivalent address in the IPv4 address family.  */
 183                 struct sockaddr_in6 sin6;
 184                 struct sockaddr_in *sin;
 185
 186                 memcpy(&sin6, ss, sizeof sin6);
 187                 sin = (struct sockaddr_in *)ss;
 188                 memset(sin, 0, sizeof *sin);
 189                 sin->sin_family = AF_INET;
 190                 *ss_len = sizeof (struct sockaddr_in);
 191 #ifdef HAVE_SOCKADDR_IN_LEN
 192                 sin->sin_len = *ss_len;
 193 #endif
 194                 sin->sin_port = sin6.sin6_port;
 195
 196                 /* There is a macro to extract the mapped part
 197                  * (IN6_V4MAPPED_TO_SINADDR ?), but it does not seem
 198                  * to be present in the Linux headers. */
 199                 memcpy(&sin->sin_addr, &sin6.sin6_addr.s6_addr[12],
 200                     sizeof sin->sin_addr);
 201         }
 202 #endif
 203 }
 204
 205
 206 /**
 207  * Look up a name from @p ss into @p name_buf.
 208  *
 209  * @param fd file descriptor for client socket.
 210  **/
 211 int lookup_name(int fd, const struct sockaddr_storage *ss,
 212                 socklen_t ss_len,
 213                 char *name_buf, size_t name_buf_size,
 214                 char *port_buf, size_t port_buf_size)
 215 {
 216         int name_err;
 217
 218         /* reverse lookup */
 219         name_err = getnameinfo((struct sockaddr *) ss, ss_len,
 220                                name_buf, name_buf_size,
 221                                port_buf, port_buf_size,
 222                                NI_NAMEREQD | NI_NUMERICSERV);
 223         if (name_err != 0) {
 224                 strlcpy(name_buf, default_name, name_buf_size);
 225                 rprintf(FLOG, "name lookup failed for %s: %s\n",
 226                         client_addr(fd), gai_strerror(name_err));
 227                 return name_err;
 228         }
 229
 230         return 0;
 231 }
 232
 233
 234
 235 /**
 236  * Compare an addrinfo from the resolver to a sockinfo.
 237  *
 238  * Like strcmp, returns 0 for identical.
 239  **/
 240 int compare_addrinfo_sockaddr(const struct addrinfo *ai,
 241                               const struct sockaddr_storage *ss)
 242 {
 243         int ss_family = get_sockaddr_family(ss);
 244         const char fn[] = "compare_addrinfo_sockaddr";
 245
 246         if (ai->ai_family != ss_family) {
 247                 rprintf(FLOG, "%s: response family %d != %d\n",
 248                         fn, ai->ai_family, ss_family);
 249                 return 1;
 250         }
 251
 252         /* The comparison method depends on the particular AF. */
 253         if (ss_family == AF_INET) {
 254                 const struct sockaddr_in *sin1, *sin2;
 255
 256                 sin1 = (const struct sockaddr_in *) ss;
 257                 sin2 = (const struct sockaddr_in *) ai->ai_addr;
 258
 259                 return memcmp(&sin1->sin_addr, &sin2->sin_addr,
 260                               sizeof sin1->sin_addr);
 261         }
 262
 263 #ifdef INET6
 264         if (ss_family == AF_INET6) {
 265                 const struct sockaddr_in6 *sin1, *sin2;
 266
 267                 sin1 = (const struct sockaddr_in6 *) ss;
 268                 sin2 = (const struct sockaddr_in6 *) ai->ai_addr;
 269
 270                 if (ai->ai_addrlen < sizeof (struct sockaddr_in6)) {
 271                         rprintf(FLOG, "%s: too short sockaddr_in6; length=%d\n",
 272                                 fn, (int)ai->ai_addrlen);
 273                         return 1;
 274                 }
 275
 276                 if (memcmp(&sin1->sin6_addr, &sin2->sin6_addr,
 277                            sizeof sin1->sin6_addr))
 278                         return 1;
 279
 280 #ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
 281                 if (sin1->sin6_scope_id != sin2->sin6_scope_id)
 282                         return 1;
 283 #endif
 284                 return 0;
 285         }
 286 #endif /* INET6 */
 287
 288         /* don't know */
 289         return 1;
 290 }
 291
 292
 293 /**
 294  * Do a forward lookup on @p name_buf and make sure it corresponds to
 295  * @p ss -- otherwise we may be being spoofed.  If we suspect we are,
 296  * then we don't abort the connection but just emit a warning, and
 297  * change @p name_buf to be "UNKNOWN".
 298  *
 299  * We don't do anything with the service when checking the name,
 300  * because it doesn't seem that it could be spoofed in any way, and
 301  * getaddrinfo on random service names seems to cause problems on AIX.
 302  **/
 303 int check_name(int fd,
 304                const struct sockaddr_storage *ss,
 305                char *name_buf, size_t name_buf_size)
 306 {
 307         struct addrinfo hints, *res, *res0;
 308         int error;
 309         int ss_family = get_sockaddr_family(ss);
 310
 311         memset(&hints, 0, sizeof hints);
 312         hints.ai_family = ss_family;
 313         hints.ai_flags = AI_CANONNAME;
 314         hints.ai_socktype = SOCK_STREAM;
 315         error = getaddrinfo(name_buf, NULL, &hints, &res0);
 316         if (error) {
 317                 rprintf(FLOG, "forward name lookup for %s failed: %s\n",
 318                         name_buf, gai_strerror(error));
 319                 strlcpy(name_buf, default_name, name_buf_size);
 320                 return error;
 321         }
 322
 323         /* Given all these results, we expect that one of them will be
 324          * the same as ss.  The comparison is a bit complicated. */
 325         for (res = res0; res; res = res->ai_next) {
 326                 if (!compare_addrinfo_sockaddr(res, ss))
 327                         break;  /* OK, identical */
 328         }
 329
 330         if (!res0) {
 331                 /* We hit the end of the list without finding an
 332                  * address that was the same as ss. */
 333                 rprintf(FLOG, "no known address for \"%s\": "
 334                         "spoofed address?\n", name_buf);
 335                 strlcpy(name_buf, default_name, name_buf_size);
 336         } else if (res == NULL) {
 337                 /* We hit the end of the list without finding an
 338                  * address that was the same as ss. */
 339                 rprintf(FLOG, "%s is not a known address for \"%s\": "
 340                         "spoofed address?\n", client_addr(fd), name_buf);
 341                 strlcpy(name_buf, default_name, name_buf_size);
 342         }
 343
 344         freeaddrinfo(res0);
 345         return 0;
 346 }