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) 2002-2008 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                 memset(&hint, 0, sizeof hint);
 112
 113 #ifdef AI_NUMERICHOST
 114                 hint.ai_flags = AI_NUMERICHOST;
 115 #endif
 116                 hint.ai_socktype = SOCK_STREAM;
 117
 118                 if ((err = getaddrinfo(addr, NULL, &hint, &answer)) != 0) {
 119                         rprintf(FLOG, "malformed address %s: %s\n",
 120                                 addr, gai_strerror(err));
 121                         return name_buf;
 122                 }
 123
 124                 switch (answer->ai_family) {
 125                 case AF_INET:
 126                         ss_len = sizeof (struct sockaddr_in);
 127                         memcpy(&ss, answer->ai_addr, ss_len);
 128                         break;
 129 #ifdef INET6
 130                 case AF_INET6:
 131                         ss_len = sizeof (struct sockaddr_in6);
 132                         memcpy(&ss, answer->ai_addr, ss_len);
 133                         break;
 134 #endif
 135                 default:
 136                         exit_cleanup(RERR_SOCKETIO);
 137                 }
 138                 freeaddrinfo(answer);
 139         } else {
 140                 ss_len = sizeof ss;
 141                 client_sockaddr(fd, &ss, &ss_len);
 142         }
 143
 144         if (lookup_name(fd, &ss, ss_len, name_buf, sizeof name_buf,
 145                         port_buf, sizeof port_buf) == 0)
 146                 check_name(fd, &ss, name_buf, sizeof name_buf);
 147
 148         return name_buf;
 149 }
 150
 151
 152
 153 /**
 154  * Get the sockaddr for the client.
 155  *
 156  * If it comes in as an ipv4 address mapped into IPv6 format then we
 157  * convert it back to a regular IPv4.
 158  **/
 159 void client_sockaddr(int fd,
 160                      struct sockaddr_storage *ss,
 161                      socklen_t *ss_len)
 162 {
 163         memset(ss, 0, sizeof *ss);
 164
 165         if (getpeername(fd, (struct sockaddr *) ss, ss_len)) {
 166                 /* FIXME: Can we really not continue? */
 167                 rsyserr(FLOG, errno, "getpeername on fd%d failed", fd);
 168                 exit_cleanup(RERR_SOCKETIO);
 169         }
 170
 171 #ifdef INET6
 172         if (get_sockaddr_family(ss) == AF_INET6 &&
 173             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)ss)->sin6_addr)) {
 174                 /* OK, so ss is in the IPv6 family, but it is really
 175                  * an IPv4 address: something like
 176                  * "::ffff:10.130.1.2".  If we use it as-is, then the
 177                  * reverse lookup might fail or perhaps something else
 178                  * bad might happen.  So instead we convert it to an
 179                  * equivalent address in the IPv4 address family.  */
 180                 struct sockaddr_in6 sin6;
 181                 struct sockaddr_in *sin;
 182
 183                 memcpy(&sin6, ss, sizeof sin6);
 184                 sin = (struct sockaddr_in *)ss;
 185                 memset(sin, 0, sizeof *sin);
 186                 sin->sin_family = AF_INET;
 187                 *ss_len = sizeof (struct sockaddr_in);
 188 #ifdef HAVE_SOCKADDR_IN_LEN
 189                 sin->sin_len = *ss_len;
 190 #endif
 191                 sin->sin_port = sin6.sin6_port;
 192
 193                 /* There is a macro to extract the mapped part
 194                  * (IN6_V4MAPPED_TO_SINADDR ?), but it does not seem
 195                  * to be present in the Linux headers. */
 196                 memcpy(&sin->sin_addr, &sin6.sin6_addr.s6_addr[12],
 197                     sizeof sin->sin_addr);
 198         }
 199 #endif
 200 }
 201
 202
 203 /**
 204  * Look up a name from @p ss into @p name_buf.
 205  *
 206  * @param fd file descriptor for client socket.
 207  **/
 208 int lookup_name(int fd, const struct sockaddr_storage *ss,
 209                 socklen_t ss_len,
 210                 char *name_buf, size_t name_buf_size,
 211                 char *port_buf, size_t port_buf_size)
 212 {
 213         int name_err;
 214
 215         /* reverse lookup */
 216         name_err = getnameinfo((struct sockaddr *) ss, ss_len,
 217                                name_buf, name_buf_size,
 218                                port_buf, port_buf_size,
 219                                NI_NAMEREQD | NI_NUMERICSERV);
 220         if (name_err != 0) {
 221                 strlcpy(name_buf, default_name, name_buf_size);
 222                 rprintf(FLOG, "name lookup failed for %s: %s\n",
 223                         client_addr(fd), gai_strerror(name_err));
 224                 return name_err;
 225         }
 226
 227         return 0;
 228 }
 229
 230
 231
 232 /**
 233  * Compare an addrinfo from the resolver to a sockinfo.
 234  *
 235  * Like strcmp, returns 0 for identical.
 236  **/
 237 int compare_addrinfo_sockaddr(const struct addrinfo *ai,
 238                               const struct sockaddr_storage *ss)
 239 {
 240         int ss_family = get_sockaddr_family(ss);
 241         const char fn[] = "compare_addrinfo_sockaddr";
 242
 243         if (ai->ai_family != ss_family) {
 244                 rprintf(FLOG, "%s: response family %d != %d\n",
 245                         fn, ai->ai_family, ss_family);
 246                 return 1;
 247         }
 248
 249         /* The comparison method depends on the particular AF. */
 250         if (ss_family == AF_INET) {
 251                 const struct sockaddr_in *sin1, *sin2;
 252
 253                 sin1 = (const struct sockaddr_in *) ss;
 254                 sin2 = (const struct sockaddr_in *) ai->ai_addr;
 255
 256                 return memcmp(&sin1->sin_addr, &sin2->sin_addr,
 257                               sizeof sin1->sin_addr);
 258         }
 259
 260 #ifdef INET6
 261         if (ss_family == AF_INET6) {
 262                 const struct sockaddr_in6 *sin1, *sin2;
 263
 264                 sin1 = (const struct sockaddr_in6 *) ss;
 265                 sin2 = (const struct sockaddr_in6 *) ai->ai_addr;
 266
 267                 if (ai->ai_addrlen < sizeof (struct sockaddr_in6)) {
 268                         rprintf(FLOG, "%s: too short sockaddr_in6; length=%d\n",
 269                                 fn, (int)ai->ai_addrlen);
 270                         return 1;
 271                 }
 272
 273                 if (memcmp(&sin1->sin6_addr, &sin2->sin6_addr,
 274                            sizeof sin1->sin6_addr))
 275                         return 1;
 276
 277 #ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
 278                 if (sin1->sin6_scope_id != sin2->sin6_scope_id)
 279                         return 1;
 280 #endif
 281                 return 0;
 282         }
 283 #endif /* INET6 */
 284
 285         /* don't know */
 286         return 1;
 287 }
 288
 289
 290 /**
 291  * Do a forward lookup on @p name_buf and make sure it corresponds to
 292  * @p ss -- otherwise we may be being spoofed.  If we suspect we are,
 293  * then we don't abort the connection but just emit a warning, and
 294  * change @p name_buf to be "UNKNOWN".
 295  *
 296  * We don't do anything with the service when checking the name,
 297  * because it doesn't seem that it could be spoofed in any way, and
 298  * getaddrinfo on random service names seems to cause problems on AIX.
 299  **/
 300 int check_name(int fd,
 301                const struct sockaddr_storage *ss,
 302                char *name_buf, size_t name_buf_size)
 303 {
 304         struct addrinfo hints, *res, *res0;
 305         int error;
 306         int ss_family = get_sockaddr_family(ss);
 307
 308         memset(&hints, 0, sizeof hints);
 309         hints.ai_family = ss_family;
 310         hints.ai_flags = AI_CANONNAME;
 311         hints.ai_socktype = SOCK_STREAM;
 312         error = getaddrinfo(name_buf, NULL, &hints, &res0);
 313         if (error) {
 314                 rprintf(FLOG, "forward name lookup for %s failed: %s\n",
 315                         name_buf, gai_strerror(error));
 316                 strlcpy(name_buf, default_name, name_buf_size);
 317                 return error;
 318         }
 319
 320         /* Given all these results, we expect that one of them will be
 321          * the same as ss.  The comparison is a bit complicated. */
 322         for (res = res0; res; res = res->ai_next) {
 323                 if (!compare_addrinfo_sockaddr(res, ss))
 324                         break;  /* OK, identical */
 325         }
 326
 327         if (!res0) {
 328                 /* We hit the end of the list without finding an
 329                  * address that was the same as ss. */
 330                 rprintf(FLOG, "no known address for \"%s\": "
 331                         "spoofed address?\n", name_buf);
 332                 strlcpy(name_buf, default_name, name_buf_size);
 333         } else if (res == NULL) {
 334                 /* We hit the end of the list without finding an
 335                  * address that was the same as ss. */
 336                 rprintf(FLOG, "%s is not a known address for \"%s\": "
 337                         "spoofed address?\n", client_addr(fd), name_buf);
 338                 strlcpy(name_buf, default_name, name_buf_size);
 339         }
 340
 341         freeaddrinfo(res0);
 342         return 0;
 343 }