clientname.c

   1 /* -*- c-file-style: "linux" -*-
   2
   3    rsync -- fast file replication program
   4
   5    Copyright (C) 1992-2001 by Andrew Tridgell <tridge@samba.org>
   6    Copyright (C) 2001, 2002 by Martin Pool <mbp@samba.org>
   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 2 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
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 /**
  24  * @file clientname.c
  25  *
  26  * Functions for looking up the remote name or addr of a socket.
  27  *
  28  * This file is now converted to use the new-style getaddrinfo()
  29  * interface, which supports IPv6 but is also supported on recent
  30  * IPv4-only machines.  On systems that don't have that interface, we
  31  * emulate it using the KAME implementation.
  32  **/
  33
  34 #include "rsync.h"
  35
  36 static const char default_name[] = "UNKNOWN";
  37 extern int am_daemon;
  38 extern int am_server;
  39
  40
  41 /**
  42  * Return the IP addr of the client as a string
  43  **/
  44 char *client_addr(int fd)
  45 {
  46         struct sockaddr_storage ss;
  47         socklen_t length = sizeof ss;
  48         char *ssh_client, *p;
  49         int len;
  50         static char addr_buf[100];
  51         static int initialised;
  52
  53         if (initialised) return addr_buf;
  54
  55         initialised = 1;
  56
  57         if (am_server) {
  58                 /* daemon over --rsh mode */
  59                 strcpy(addr_buf, "0.0.0.0");
  60                 if ((ssh_client = getenv("SSH_CLIENT")) != NULL) {
  61                         /* truncate SSH_CLIENT to just IP address */
  62                         p = strchr(ssh_client, ' ');
  63                         if (p) {
  64                                 len = MIN((unsigned int) (p - ssh_client),
  65                                                 sizeof(addr_buf) - 1);
  66                                 strncpy(addr_buf, ssh_client, len);
  67                                 *(addr_buf + len) = '\0';
  68                         }
  69                 }
  70         } else {
  71                 client_sockaddr(fd, &ss, &length);
  72                 getnameinfo((struct sockaddr *)&ss, length,
  73                             addr_buf, sizeof addr_buf, NULL, 0, NI_NUMERICHOST);
  74         }
  75
  76         return addr_buf;
  77 }
  78
  79
  80 static int get_sockaddr_family(const struct sockaddr_storage *ss)
  81 {
  82         return ((struct sockaddr *) ss)->sa_family;
  83 }
  84
  85
  86 /**
  87  * Return the DNS name of the client.
  88  *
  89  * The name is statically cached so that repeated lookups are quick,
  90  * so there is a limit of one lookup per customer.
  91  *
  92  * If anything goes wrong, including the name->addr->name check, then
  93  * we just use "UNKNOWN", so you can use that value in hosts allow
  94  * lines.
  95  *
  96  * After translation from sockaddr to name we do a forward lookup to
  97  * make sure nobody is spoofing PTR records.
  98  **/
  99 char *client_name(int fd)
 100 {
 101         static char name_buf[100];
 102         static char port_buf[100];
 103         static int initialised;
 104         struct sockaddr_storage ss, *ssp;
 105         struct sockaddr_in sin;
 106 #ifdef INET6
 107         struct sockaddr_in6 sin6;
 108 #endif
 109         socklen_t ss_len;
 110
 111         if (initialised) return name_buf;
 112
 113         strcpy(name_buf, default_name);
 114         initialised = 1;
 115
 116         if (am_server) {
 117                 /* daemon over --rsh mode */
 118
 119                 char *addr = client_addr(fd);
 120 #ifdef INET6
 121                 int dots = 0;
 122                 char *p;
 123
 124                 for (p = addr; *p && (dots <= 3); p++) {
 125                     if (*p == '.')
 126                         dots++;
 127                 }
 128                 if (dots > 3) {
 129                         /* more than 4 parts to IP address, must be ipv6 */
 130                         ssp = (struct sockaddr_storage *) &sin6;
 131                         ss_len = sizeof sin6;
 132                         memset(ssp, 0, ss_len);
 133                         inet_pton(AF_INET6, addr, &sin6.sin6_addr);
 134                         sin6.sin6_family = AF_INET6;
 135                 } else
 136 #endif
 137                 {
 138                         ssp = (struct sockaddr_storage *) &sin;
 139                         ss_len = sizeof sin;
 140                         memset(ssp, 0, ss_len);
 141                         inet_pton(AF_INET, addr, &sin.sin_addr);
 142                         sin.sin_family = AF_INET;
 143                 }
 144
 145         } else {
 146                 ss_len = sizeof ss;
 147                 ssp = &ss;
 148
 149                 client_sockaddr(fd, &ss, &ss_len);
 150
 151         }
 152
 153         if (!lookup_name(fd, ssp, ss_len, name_buf, sizeof name_buf,
 154                         port_buf, sizeof port_buf))
 155                 check_name(fd, ssp, name_buf);
 156
 157         return name_buf;
 158 }
 159
 160
 161
 162 /**
 163  * Get the sockaddr for the client.
 164  *
 165  * If it comes in as an ipv4 address mapped into IPv6 format then we
 166  * convert it back to a regular IPv4.
 167  **/
 168 void client_sockaddr(int fd,
 169                      struct sockaddr_storage *ss,
 170                      socklen_t *ss_len)
 171 {
 172         memset(ss, 0, sizeof(*ss));
 173
 174         if (getpeername(fd, (struct sockaddr *) ss, ss_len)) {
 175                 /* FIXME: Can we really not continue? */
 176                 rprintf(FERROR, RSYNC_NAME ": getpeername on fd%d failed: %s\n",
 177                         fd, strerror(errno));
 178                 exit_cleanup(RERR_SOCKETIO);
 179         }
 180
 181 #ifdef INET6
 182         if (get_sockaddr_family(ss) == AF_INET6 &&
 183             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)ss)->sin6_addr)) {
 184                 /* OK, so ss is in the IPv6 family, but it is really
 185                  * an IPv4 address: something like
 186                  * "::ffff:10.130.1.2".  If we use it as-is, then the
 187                  * reverse lookup might fail or perhaps something else
 188                  * bad might happen.  So instead we convert it to an
 189                  * equivalent address in the IPv4 address family.  */
 190                 struct sockaddr_in6 sin6;
 191                 struct sockaddr_in *sin;
 192
 193                 memcpy(&sin6, ss, sizeof(sin6));
 194                 sin = (struct sockaddr_in *)ss;
 195                 memset(sin, 0, sizeof(*sin));
 196                 sin->sin_family = AF_INET;
 197                 *ss_len = sizeof(struct sockaddr_in);
 198 #ifdef HAVE_SOCKADDR_LEN
 199                 sin->sin_len = *ss_len;
 200 #endif
 201                 sin->sin_port = sin6.sin6_port;
 202
 203                 /* There is a macro to extract the mapped part
 204                  * (IN6_V4MAPPED_TO_SINADDR ?), but it does not seem
 205                  * to be present in the Linux headers. */
 206                 memcpy(&sin->sin_addr, &sin6.sin6_addr.s6_addr[12],
 207                         sizeof(sin->sin_addr));
 208         }
 209 #endif
 210 }
 211
 212
 213 /**
 214  * Look up a name from @p ss into @p name_buf.
 215  *
 216  * @param fd file descriptor for client socket.
 217  **/
 218 int lookup_name(int fd, const struct sockaddr_storage *ss,
 219                 socklen_t ss_len,
 220                 char *name_buf, size_t name_buf_len,
 221                 char *port_buf, size_t port_buf_len)
 222 {
 223         int name_err;
 224
 225         /* reverse lookup */
 226         name_err = getnameinfo((struct sockaddr *) ss, ss_len,
 227                                name_buf, name_buf_len,
 228                                port_buf, port_buf_len,
 229                                NI_NAMEREQD | NI_NUMERICSERV);
 230         if (name_err != 0) {
 231                 strcpy(name_buf, default_name);
 232                 rprintf(FERROR, RSYNC_NAME ": name lookup failed for %s: %s\n",
 233                         client_addr(fd),
 234                         gai_strerror(name_err));
 235                 return name_err;
 236         }
 237
 238         return 0;
 239 }
 240
 241
 242
 243 /**
 244  * Compare an addrinfo from the resolver to a sockinfo.
 245  *
 246  * Like strcmp, returns 0 for identical.
 247  **/
 248 int compare_addrinfo_sockaddr(const struct addrinfo *ai,
 249                               const struct sockaddr_storage *ss)
 250 {
 251         int ss_family = get_sockaddr_family(ss);
 252         const char fn[] = "compare_addrinfo_sockaddr";
 253
 254         if (ai->ai_family != ss_family) {
 255                 rprintf(FERROR,
 256                         "%s: response family %d != %d\n",
 257                         fn, ai->ai_family, ss_family);
 258                 return 1;
 259         }
 260
 261         /* The comparison method depends on the particular AF. */
 262         if (ss_family == AF_INET) {
 263                 const struct sockaddr_in *sin1, *sin2;
 264
 265                 sin1 = (const struct sockaddr_in *) ss;
 266                 sin2 = (const struct sockaddr_in *) ai->ai_addr;
 267
 268                 return memcmp(&sin1->sin_addr, &sin2->sin_addr,
 269                               sizeof sin1->sin_addr);
 270         }
 271 #ifdef INET6
 272         else if (ss_family == AF_INET6) {
 273                 const struct sockaddr_in6 *sin1, *sin2;
 274
 275                 sin1 = (const struct sockaddr_in6 *) ss;
 276                 sin2 = (const struct sockaddr_in6 *) ai->ai_addr;
 277
 278                 if (ai->ai_addrlen < sizeof(struct sockaddr_in6)) {
 279                         rprintf(FERROR,
 280                                 "%s: too short sockaddr_in6; length=%d\n",
 281                                 fn, ai->ai_addrlen);
 282                         return 1;
 283                 }
 284
 285                 if (memcmp(&sin1->sin6_addr, &sin2->sin6_addr,
 286                            sizeof sin1->sin6_addr))
 287                         return 1;
 288
 289 #ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
 290                 if (sin1->sin6_scope_id != sin2->sin6_scope_id)
 291                         return 1;
 292 #endif
 293                 return 0;
 294         }
 295 #endif /* INET6 */
 296         else {
 297                 /* don't know */
 298                 return 1;
 299         }
 300 }
 301
 302
 303 /**
 304  * Do a forward lookup on @p name_buf and make sure it corresponds to
 305  * @p ss -- otherwise we may be being spoofed.  If we suspect we are,
 306  * then we don't abort the connection but just emit a warning, and
 307  * change @p name_buf to be "UNKNOWN".
 308  *
 309  * We don't do anything with the service when checking the name,
 310  * because it doesn't seem that it could be spoofed in any way, and
 311  * getaddrinfo on random service names seems to cause problems on AIX.
 312  **/
 313 int check_name(int fd,
 314                const struct sockaddr_storage *ss,
 315                char *name_buf)
 316 {
 317         struct addrinfo hints, *res, *res0;
 318         int error;
 319         int ss_family = get_sockaddr_family(ss);
 320
 321         memset(&hints, 0, sizeof(hints));
 322         hints.ai_family = ss_family;
 323         hints.ai_flags = AI_CANONNAME;
 324         hints.ai_socktype = SOCK_STREAM;
 325         error = getaddrinfo(name_buf, NULL, &hints, &res0);
 326         if (error) {
 327                 rprintf(FERROR,
 328                         RSYNC_NAME ": forward name lookup for %s failed: %s\n",
 329                         name_buf, gai_strerror(error));
 330                 strcpy(name_buf, default_name);
 331                 return error;
 332         }
 333
 334
 335         /* Given all these results, we expect that one of them will be
 336          * the same as ss.  The comparison is a bit complicated. */
 337         for (res = res0; res; res = res->ai_next) {
 338                 if (!compare_addrinfo_sockaddr(res, ss))
 339                         break;  /* OK, identical */
 340         }
 341
 342         if (!res0) {
 343                 /* We hit the end of the list without finding an
 344                  * address that was the same as ss. */
 345                 rprintf(FERROR, RSYNC_NAME
 346                         ": no known address for \"%s\": "
 347                         "spoofed address?\n",
 348                         name_buf);
 349                 strcpy(name_buf, default_name);
 350         } else if (res == NULL) {
 351                 /* We hit the end of the list without finding an
 352                  * address that was the same as ss. */
 353                 rprintf(FERROR, RSYNC_NAME
 354                         ": %s is not a known address for \"%s\": "
 355                         "spoofed address?\n",
 356                         client_addr(fd),
 357                         name_buf);
 358                 strcpy(name_buf, default_name);
 359         }
 360
 361         freeaddrinfo(res0);
 362         return 0;
 363 }
 364