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) 2002-2019 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
  45         if (initialised)
  46                 return addr_buf;
  47
  48         initialised = 1;
  49
  50         if (am_server) {        /* daemon over --rsh mode */
  51                 char *env_str;
  52                 strlcpy(addr_buf, "0.0.0.0", sizeof addr_buf);
  53                 if ((env_str = getenv("REMOTE_HOST")) != NULL
  54                  || (env_str = getenv("SSH_CONNECTION")) != NULL
  55                  || (env_str = getenv("SSH_CLIENT")) != NULL
  56                  || (env_str = getenv("SSH2_CLIENT")) != NULL) {
  57                         char *p;
  58                         strlcpy(addr_buf, env_str, sizeof addr_buf);
  59                         /* Truncate the value to just the IP address. */
  60                         if ((p = strchr(addr_buf, ' ')) != NULL)
  61                                 *p = '\0';
  62                 }
  63         } else {
  64                 client_sockaddr(fd, &ss, &length);
  65                 getnameinfo((struct sockaddr *)&ss, length,
  66                             addr_buf, sizeof addr_buf, NULL, 0, NI_NUMERICHOST);
  67         }
  68
  69         return addr_buf;
  70 }
  71
  72
  73 static int get_sockaddr_family(const struct sockaddr_storage *ss)
  74 {
  75         return ((struct sockaddr *) ss)->sa_family;
  76 }
  77
  78
  79 /**
  80  * Return the DNS name of the client.
  81  *
  82  * The name is statically cached so that repeated lookups are quick,
  83  * so there is a limit of one lookup per customer.
  84  *
  85  * If anything goes wrong, including the name->addr->name check, then
  86  * we just use "UNKNOWN", so you can use that value in hosts allow
  87  * lines.
  88  *
  89  * After translation from sockaddr to name we do a forward lookup to
  90  * make sure nobody is spoofing PTR records.
  91  **/
  92 char *client_name(int fd)
  93 {
  94         static char name_buf[100];
  95         static char port_buf[100];
  96         static int initialised;
  97         struct sockaddr_storage ss;
  98         socklen_t ss_len;
  99
 100         if (initialised)
 101                 return name_buf;
 102
 103         strlcpy(name_buf, default_name, sizeof name_buf);
 104         initialised = 1;
 105
 106         memset(&ss, 0, sizeof ss);
 107
 108         if (am_server) {        /* daemon over --rsh mode */
 109                 char *addr = client_addr(fd);
 110                 struct addrinfo hint, *answer;
 111                 int err;
 112
 113                 if (strcmp(addr, "0.0.0.0") == 0)
 114                         return name_buf;
 115
 116                 memset(&hint, 0, sizeof hint);
 117
 118 #ifdef AI_NUMERICHOST
 119                 hint.ai_flags = AI_NUMERICHOST;
 120 #endif
 121                 hint.ai_socktype = SOCK_STREAM;
 122
 123                 if ((err = getaddrinfo(addr, NULL, &hint, &answer)) != 0) {
 124                         rprintf(FLOG, "malformed address %s: %s\n",
 125                                 addr, gai_strerror(err));
 126                         return name_buf;
 127                 }
 128
 129                 switch (answer->ai_family) {
 130                 case AF_INET:
 131                         ss_len = sizeof (struct sockaddr_in);
 132                         memcpy(&ss, answer->ai_addr, ss_len);
 133                         break;
 134 #ifdef INET6
 135                 case AF_INET6:
 136                         ss_len = sizeof (struct sockaddr_in6);
 137                         memcpy(&ss, answer->ai_addr, ss_len);
 138                         break;
 139 #endif
 140                 default:
 141                         exit_cleanup(RERR_SOCKETIO);
 142                 }
 143                 freeaddrinfo(answer);
 144         } else {
 145                 ss_len = sizeof ss;
 146                 client_sockaddr(fd, &ss, &ss_len);
 147         }
 148
 149         if (lookup_name(fd, &ss, ss_len, name_buf, sizeof name_buf,
 150                         port_buf, sizeof port_buf) == 0)
 151                 check_name(fd, &ss, name_buf, sizeof name_buf);
 152
 153         return name_buf;
 154 }
 155
 156
 157
 158 /**
 159  * Get the sockaddr for the client.
 160  *
 161  * If it comes in as an ipv4 address mapped into IPv6 format then we
 162  * convert it back to a regular IPv4.
 163  **/
 164 void client_sockaddr(int fd,
 165                      struct sockaddr_storage *ss,
 166                      socklen_t *ss_len)
 167 {
 168         memset(ss, 0, sizeof *ss);
 169
 170         if (getpeername(fd, (struct sockaddr *) ss, ss_len)) {
 171                 /* FIXME: Can we really not continue? */
 172                 rsyserr(FLOG, errno, "getpeername on fd%d failed", fd);
 173                 exit_cleanup(RERR_SOCKETIO);
 174         }
 175
 176 #ifdef INET6
 177         if (get_sockaddr_family(ss) == AF_INET6 &&
 178             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)ss)->sin6_addr)) {
 179                 /* OK, so ss is in the IPv6 family, but it is really
 180                  * an IPv4 address: something like
 181                  * "::ffff:10.130.1.2".  If we use it as-is, then the
 182                  * reverse lookup might fail or perhaps something else
 183                  * bad might happen.  So instead we convert it to an
 184                  * equivalent address in the IPv4 address family.  */
 185                 struct sockaddr_in6 sin6;
 186                 struct sockaddr_in *sin;
 187
 188                 memcpy(&sin6, ss, sizeof sin6);
 189                 sin = (struct sockaddr_in *)ss;
 190                 memset(sin, 0, sizeof *sin);
 191                 sin->sin_family = AF_INET;
 192                 *ss_len = sizeof (struct sockaddr_in);
 193 #ifdef HAVE_SOCKADDR_IN_LEN
 194                 sin->sin_len = *ss_len;
 195 #endif
 196                 sin->sin_port = sin6.sin6_port;
 197
 198                 /* There is a macro to extract the mapped part
 199                  * (IN6_V4MAPPED_TO_SINADDR ?), but it does not seem
 200                  * to be present in the Linux headers. */
 201                 memcpy(&sin->sin_addr, &sin6.sin6_addr.s6_addr[12],
 202                     sizeof sin->sin_addr);
 203         }
 204 #endif
 205 }
 206
 207
 208 /**
 209  * Look up a name from @p ss into @p name_buf.
 210  *
 211  * @param fd file descriptor for client socket.
 212  **/
 213 int lookup_name(int fd, const struct sockaddr_storage *ss,
 214                 socklen_t ss_len,
 215                 char *name_buf, size_t name_buf_size,
 216                 char *port_buf, size_t port_buf_size)
 217 {
 218         int name_err;
 219
 220         /* reverse lookup */
 221         name_err = getnameinfo((struct sockaddr *) ss, ss_len,
 222                                name_buf, name_buf_size,
 223                                port_buf, port_buf_size,
 224                                NI_NAMEREQD | NI_NUMERICSERV);
 225         if (name_err != 0) {
 226                 strlcpy(name_buf, default_name, name_buf_size);
 227                 rprintf(FLOG, "name lookup failed for %s: %s\n",
 228                         client_addr(fd), gai_strerror(name_err));
 229                 return name_err;
 230         }
 231
 232         return 0;
 233 }
 234
 235
 236
 237 /**
 238  * Compare an addrinfo from the resolver to a sockinfo.
 239  *
 240  * Like strcmp, returns 0 for identical.
 241  **/
 242 int compare_addrinfo_sockaddr(const struct addrinfo *ai,
 243                               const struct sockaddr_storage *ss)
 244 {
 245         int ss_family = get_sockaddr_family(ss);
 246         const char fn[] = "compare_addrinfo_sockaddr";
 247
 248         if (ai->ai_family != ss_family) {
 249                 rprintf(FLOG, "%s: response family %d != %d\n",
 250                         fn, ai->ai_family, ss_family);
 251                 return 1;
 252         }
 253
 254         /* The comparison method depends on the particular AF. */
 255         if (ss_family == AF_INET) {
 256                 const struct sockaddr_in *sin1, *sin2;
 257
 258                 sin1 = (const struct sockaddr_in *) ss;
 259                 sin2 = (const struct sockaddr_in *) ai->ai_addr;
 260
 261                 return memcmp(&sin1->sin_addr, &sin2->sin_addr,
 262                               sizeof sin1->sin_addr);
 263         }
 264
 265 #ifdef INET6
 266         if (ss_family == AF_INET6) {
 267                 const struct sockaddr_in6 *sin1, *sin2;
 268
 269                 sin1 = (const struct sockaddr_in6 *) ss;
 270                 sin2 = (const struct sockaddr_in6 *) ai->ai_addr;
 271
 272                 if (ai->ai_addrlen < sizeof (struct sockaddr_in6)) {
 273                         rprintf(FLOG, "%s: too short sockaddr_in6; length=%d\n",
 274                                 fn, (int)ai->ai_addrlen);
 275                         return 1;
 276                 }
 277
 278                 if (memcmp(&sin1->sin6_addr, &sin2->sin6_addr,
 279                            sizeof sin1->sin6_addr))
 280                         return 1;
 281
 282 #ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
 283                 if (sin1->sin6_scope_id != sin2->sin6_scope_id)
 284                         return 1;
 285 #endif
 286                 return 0;
 287         }
 288 #endif /* INET6 */
 289
 290         /* don't know */
 291         return 1;
 292 }
 293
 294
 295 /**
 296  * Do a forward lookup on @p name_buf and make sure it corresponds to
 297  * @p ss -- otherwise we may be being spoofed.  If we suspect we are,
 298  * then we don't abort the connection but just emit a warning, and
 299  * change @p name_buf to be "UNKNOWN".
 300  *
 301  * We don't do anything with the service when checking the name,
 302  * because it doesn't seem that it could be spoofed in any way, and
 303  * getaddrinfo on random service names seems to cause problems on AIX.
 304  **/
 305 int check_name(int fd,
 306                const struct sockaddr_storage *ss,
 307                char *name_buf, size_t name_buf_size)
 308 {
 309         struct addrinfo hints, *res, *res0;
 310         int error;
 311         int ss_family = get_sockaddr_family(ss);
 312
 313         memset(&hints, 0, sizeof hints);
 314         hints.ai_family = ss_family;
 315         hints.ai_flags = AI_CANONNAME;
 316         hints.ai_socktype = SOCK_STREAM;
 317         error = getaddrinfo(name_buf, NULL, &hints, &res0);
 318         if (error) {
 319                 rprintf(FLOG, "forward name lookup for %s failed: %s\n",
 320                         name_buf, gai_strerror(error));
 321                 strlcpy(name_buf, default_name, name_buf_size);
 322                 return error;
 323         }
 324
 325         /* Given all these results, we expect that one of them will be
 326          * the same as ss.  The comparison is a bit complicated. */
 327         for (res = res0; res; res = res->ai_next) {
 328                 if (!compare_addrinfo_sockaddr(res, ss))
 329                         break;  /* OK, identical */
 330         }
 331
 332         if (!res0) {
 333                 /* We hit the end of the list without finding an
 334                  * address that was the same as ss. */
 335                 rprintf(FLOG, "no known address for \"%s\": "
 336                         "spoofed address?\n", name_buf);
 337                 strlcpy(name_buf, default_name, name_buf_size);
 338         } else if (res == NULL) {
 339                 /* We hit the end of the list without finding an
 340                  * address that was the same as ss. */
 341                 rprintf(FLOG, "%s is not a known address for \"%s\": "
 342                         "spoofed address?\n", client_addr(fd), name_buf);
 343                 strlcpy(name_buf, default_name, name_buf_size);
 344         }
 345
 346         freeaddrinfo(res0);
 347         return 0;
 348 }