contrib/tcp_wrappers/socket.c

   1  /*
   2   * This module determines the type of socket (datagram, stream), the client
   3   * socket address and port, the server socket address and port. In addition,
   4   * it provides methods to map a transport address to a printable host name
   5   * or address. Socket address information results are in static memory.
   6   *
   7   * The result from the hostname lookup method is STRING_PARANOID when a host
   8   * pretends to have someone elses name, or when a host name is available but
   9   * could not be verified.
  10   *
  11   * When lookup or conversion fails the result is set to STRING_UNKNOWN.
  12   *
  13   * Diagnostics are reported through syslog(3).
  14   *
  15   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  16   *
  17   * $FreeBSD: src/contrib/tcp_wrappers/socket.c,v 1.2.2.3 2001/07/04 20:18:11 kris Exp $
  18   */
  19
  20 /* System libraries. */
  21
  22 #include <sys/types.h>
  23 #include <sys/param.h>
  24 #include <sys/socket.h>
  25 #include <netinet/in.h>
  26 #include <netdb.h>
  27 #include <stdio.h>
  28 #include <syslog.h>
  29 #include <string.h>
  30
  31 #ifdef INET6
  32 #ifndef NI_WITHSCOPEID
  33 #define NI_WITHSCOPEID  0
  34 #endif
  35 #else
  36 extern char *inet_ntoa();
  37 #endif
  38
  39 /* Local stuff. */
  40
  41 #include "tcpd.h"
  42
  43 /* Forward declarations. */
  44
  45 static void sock_sink();
  46
  47 #ifdef APPEND_DOT
  48
  49  /*
  50   * Speed up DNS lookups by terminating the host name with a dot. Should be
  51   * done with care. The speedup can give problems with lookups from sources
  52   * that lack DNS-style trailing dot magic, such as local files or NIS maps.
  53   */
  54
  55 static struct hostent *gethostbyname_dot(name)
  56 char   *name;
  57 {
  58     char    dot_name[MAXHOSTNAMELEN + 1];
  59
  60     /*
  61      * Don't append dots to unqualified names. Such names are likely to come
  62      * from local hosts files or from NIS.
  63      */
  64
  65     if (strchr(name, '.') == 0 || strlen(name) >= MAXHOSTNAMELEN - 1) {
  66         return (gethostbyname(name));
  67     } else {
  68         sprintf(dot_name, "%s.", name);
  69         return (gethostbyname(dot_name));
  70     }
  71 }
  72
  73 #define gethostbyname gethostbyname_dot
  74 #endif
  75
  76 /* sock_host - look up endpoint addresses and install conversion methods */
  77
  78 void    sock_host(request)
  79 struct request_info *request;
  80 {
  81 #ifdef INET6
  82     static struct sockaddr_storage client;
  83     static struct sockaddr_storage server;
  84 #else
  85     static struct sockaddr_in client;
  86     static struct sockaddr_in server;
  87 #endif
  88     int     len;
  89     char    buf[BUFSIZ];
  90     int     fd = request->fd;
  91
  92     sock_methods(request);
  93
  94     /*
  95      * Look up the client host address. Hal R. Brand <BRAND@addvax.llnl.gov>
  96      * suggested how to get the client host info in case of UDP connections:
  97      * peek at the first message without actually looking at its contents. We
  98      * really should verify that client.sin_family gets the value AF_INET,
  99      * but this program has already caused too much grief on systems with
 100      * broken library code.
 101      */
 102
 103     len = sizeof(client);
 104     if (getpeername(fd, (struct sockaddr *) & client, &len) < 0) {
 105         request->sink = sock_sink;
 106         len = sizeof(client);
 107         if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK,
 108                      (struct sockaddr *) & client, &len) < 0) {
 109             tcpd_warn("can't get client address: %m");
 110             return;                             /* give up */
 111         }
 112 #ifdef really_paranoid
 113         memset(buf, 0 sizeof(buf));
 114 #endif
 115     }
 116 #ifdef INET6
 117     request->client->sin = (struct sockaddr *)&client;
 118 #else
 119     request->client->sin = &client;
 120 #endif
 121
 122     /*
 123      * Determine the server binding. This is used for client username
 124      * lookups, and for access control rules that trigger on the server
 125      * address or name.
 126      */
 127
 128     len = sizeof(server);
 129     if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) {
 130         tcpd_warn("getsockname: %m");
 131         return;
 132     }
 133 #ifdef INET6
 134     request->server->sin = (struct sockaddr *)&server;
 135 #else
 136     request->server->sin = &server;
 137 #endif
 138 }
 139
 140 /* sock_hostaddr - map endpoint address to printable form */
 141
 142 void    sock_hostaddr(host)
 143 struct host_info *host;
 144 {
 145 #ifdef INET6
 146     struct sockaddr *sin = host->sin;
 147     int salen;
 148
 149     if (!sin)
 150         return;
 151 #ifdef SIN6_LEN
 152     salen = sin->sa_len;
 153 #else
 154     salen = (sin->sa_family == AF_INET) ? sizeof(struct sockaddr_in)
 155                                         : sizeof(struct sockaddr_in6);
 156 #endif
 157     getnameinfo(sin, salen, host->addr, sizeof(host->addr),
 158                 NULL, 0, NI_NUMERICHOST | NI_WITHSCOPEID);
 159 #else
 160     struct sockaddr_in *sin = host->sin;
 161
 162     if (sin != 0)
 163         STRN_CPY(host->addr, inet_ntoa(sin->sin_addr), sizeof(host->addr));
 164 #endif
 165 }
 166
 167 /* sock_hostname - map endpoint address to host name */
 168
 169 void    sock_hostname(host)
 170 struct host_info *host;
 171 {
 172 #ifdef INET6
 173     struct sockaddr *sin = host->sin;
 174     struct sockaddr_in sin4;
 175     struct addrinfo hints, *res, *res0 = NULL;
 176     int salen, alen, err = 1;
 177     char *ap = NULL, *rap, hname[NI_MAXHOST];
 178
 179     if (sin != NULL) {
 180         if (sin->sa_family == AF_INET6) {
 181             struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sin;
 182
 183             if (IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr)) {
 184                 memset(&sin4, 0, sizeof(sin4));
 185 #ifdef SIN6_LEN
 186                 sin4.sin_len = sizeof(sin4);
 187 #endif
 188                 sin4.sin_family = AF_INET;
 189                 sin4.sin_port = sin6->sin6_port;
 190                 sin4.sin_addr.s_addr = *(u_int32_t *)&sin6->sin6_addr.s6_addr[12];
 191                 sin = (struct sockaddr *)&sin4;
 192             }
 193         }
 194         switch (sin->sa_family) {
 195         case AF_INET:
 196             ap = (char *)&((struct sockaddr_in *)sin)->sin_addr;
 197             alen = sizeof(struct in_addr);
 198             salen = sizeof(struct sockaddr_in);
 199             break;
 200         case AF_INET6:
 201             ap = (char *)&((struct sockaddr_in6 *)sin)->sin6_addr;
 202             alen = sizeof(struct in6_addr);
 203             salen = sizeof(struct sockaddr_in6);
 204             break;
 205         default:
 206             break;
 207         }
 208         if (ap)
 209             err = getnameinfo(sin, salen, hname, sizeof(hname),
 210                               NULL, 0, NI_WITHSCOPEID | NI_NAMEREQD);
 211     }
 212     if (!err) {
 213
 214         STRN_CPY(host->name, hname, sizeof(host->name));
 215
 216         /* reject numeric addresses */
 217         memset(&hints, 0, sizeof(hints));
 218         hints.ai_family = sin->sa_family;
 219         hints.ai_socktype = SOCK_STREAM;
 220         hints.ai_flags = AI_PASSIVE | AI_CANONNAME | AI_NUMERICHOST;
 221         if ((err = getaddrinfo(host->name, NULL, &hints, &res0)) == 0) {
 222             freeaddrinfo(res0);
 223             tcpd_warn("host name/name mismatch: "
 224                       "reverse lookup results in non-FQDN %s",
 225                       host->name);
 226             strcpy(host->name, paranoid);       /* name is bad, clobber it */
 227         }
 228         err = !err;
 229     }
 230     if (!err) {
 231         /* we are now sure that this is non-numeric */
 232
 233         /*
 234          * Verify that the address is a member of the address list returned
 235          * by gethostbyname(hostname).
 236          *
 237          * Verify also that gethostbyaddr() and gethostbyname() return the same
 238          * hostname, or rshd and rlogind may still end up being spoofed.
 239          *
 240          * On some sites, gethostbyname("localhost") returns "localhost.domain".
 241          * This is a DNS artefact. We treat it as a special case. When we
 242          * can't believe the address list from gethostbyname("localhost")
 243          * we're in big trouble anyway.
 244          */
 245
 246         memset(&hints, 0, sizeof(hints));
 247         hints.ai_family = sin->sa_family;
 248         hints.ai_socktype = SOCK_STREAM;
 249         hints.ai_flags = AI_PASSIVE | AI_CANONNAME;
 250         if (getaddrinfo(host->name, NULL, &hints, &res0) != 0) {
 251
 252             /*
 253              * Unable to verify that the host name matches the address. This
 254              * may be a transient problem or a botched name server setup.
 255              */
 256
 257             tcpd_warn("can't verify hostname: getaddrinfo(%s, %s) failed",
 258                       host->name,
 259                       (sin->sa_family == AF_INET) ? "AF_INET" : "AF_INET6");
 260
 261         } else if ((res0->ai_canonname == NULL
 262                     || STR_NE(host->name, res0->ai_canonname))
 263                    && STR_NE(host->name, "localhost")) {
 264
 265             /*
 266              * The gethostbyaddr() and gethostbyname() calls did not return
 267              * the same hostname. This could be a nameserver configuration
 268              * problem. It could also be that someone is trying to spoof us.
 269              */
 270
 271             tcpd_warn("host name/name mismatch: %s != %.*s",
 272                       host->name, STRING_LENGTH,
 273                       (res0->ai_canonname == NULL) ? "" : res0->ai_canonname);
 274
 275         } else {
 276
 277             /*
 278              * The address should be a member of the address list returned by
 279              * gethostbyname(). We should first verify that the h_addrtype
 280              * field is AF_INET, but this program has already caused too much
 281              * grief on systems with broken library code.
 282              */
 283
 284             for (res = res0; res; res = res->ai_next) {
 285                 if (res->ai_family != sin->sa_family)
 286                     continue;
 287                 switch (res->ai_family) {
 288                 case AF_INET:
 289                     rap = (char *)&((struct sockaddr_in *)res->ai_addr)->sin_addr;
 290                     break;
 291                 case AF_INET6:
 292                     /* need to check scope_id */
 293                     if (((struct sockaddr_in6 *)sin)->sin6_scope_id !=
 294                         ((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) {
 295                         continue;
 296                     }
 297                     rap = (char *)&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr;
 298                     break;
 299                 default:
 300                     continue;
 301                 }
 302                 if (memcmp(rap, ap, alen) == 0) {
 303                     freeaddrinfo(res0);
 304                     return;                     /* name is good, keep it */
 305                 }
 306             }
 307
 308             /*
 309              * The host name does not map to the initial address. Perhaps
 310              * someone has messed up. Perhaps someone compromised a name
 311              * server.
 312              */
 313
 314             getnameinfo(sin, salen, hname, sizeof(hname),
 315                         NULL, 0, NI_NUMERICHOST | NI_WITHSCOPEID);
 316             tcpd_warn("host name/address mismatch: %s != %.*s",
 317                       hname, STRING_LENGTH,
 318                       (res0->ai_canonname == NULL) ? "" : res0->ai_canonname);
 319         }
 320         strcpy(host->name, paranoid);           /* name is bad, clobber it */
 321         if (res0)
 322             freeaddrinfo(res0);
 323     }
 324 #else /* INET6 */
 325     struct sockaddr_in *sin = host->sin;
 326     struct hostent *hp;
 327     int     i;
 328
 329     /*
 330      * On some systems, for example Solaris 2.3, gethostbyaddr(0.0.0.0) does
 331      * not fail. Instead it returns "INADDR_ANY". Unfortunately, this does
 332      * not work the other way around: gethostbyname("INADDR_ANY") fails. We
 333      * have to special-case 0.0.0.0, in order to avoid false alerts from the
 334      * host name/address checking code below.
 335      */
 336     if (sin != 0 && sin->sin_addr.s_addr != 0
 337         && (hp = gethostbyaddr((char *) &(sin->sin_addr),
 338                                sizeof(sin->sin_addr), AF_INET)) != 0) {
 339
 340         STRN_CPY(host->name, hp->h_name, sizeof(host->name));
 341
 342         /*
 343          * Verify that the address is a member of the address list returned
 344          * by gethostbyname(hostname).
 345          *
 346          * Verify also that gethostbyaddr() and gethostbyname() return the same
 347          * hostname, or rshd and rlogind may still end up being spoofed.
 348          *
 349          * On some sites, gethostbyname("localhost") returns "localhost.domain".
 350          * This is a DNS artefact. We treat it as a special case. When we
 351          * can't believe the address list from gethostbyname("localhost")
 352          * we're in big trouble anyway.
 353          */
 354
 355         if ((hp = gethostbyname(host->name)) == 0) {
 356
 357             /*
 358              * Unable to verify that the host name matches the address. This
 359              * may be a transient problem or a botched name server setup.
 360              */
 361
 362             tcpd_warn("can't verify hostname: gethostbyname(%s) failed",
 363                       host->name);
 364
 365         } else if (STR_NE(host->name, hp->h_name)
 366                    && STR_NE(host->name, "localhost")) {
 367
 368             /*
 369              * The gethostbyaddr() and gethostbyname() calls did not return
 370              * the same hostname. This could be a nameserver configuration
 371              * problem. It could also be that someone is trying to spoof us.
 372              */
 373
 374             tcpd_warn("host name/name mismatch: %s != %.*s",
 375                       host->name, STRING_LENGTH, hp->h_name);
 376
 377         } else {
 378
 379             /*
 380              * The address should be a member of the address list returned by
 381              * gethostbyname(). We should first verify that the h_addrtype
 382              * field is AF_INET, but this program has already caused too much
 383              * grief on systems with broken library code.
 384              */
 385
 386             for (i = 0; hp->h_addr_list[i]; i++) {
 387                 if (memcmp(hp->h_addr_list[i],
 388                            (char *) &sin->sin_addr,
 389                            sizeof(sin->sin_addr)) == 0)
 390                     return;                     /* name is good, keep it */
 391             }
 392
 393             /*
 394              * The host name does not map to the initial address. Perhaps
 395              * someone has messed up. Perhaps someone compromised a name
 396              * server.
 397              */
 398
 399             tcpd_warn("host name/address mismatch: %s != %.*s",
 400                       inet_ntoa(sin->sin_addr), STRING_LENGTH, hp->h_name);
 401         }
 402         strcpy(host->name, paranoid);           /* name is bad, clobber it */
 403     }
 404 #endif /* INET6 */
 405 }
 406
 407 /* sock_sink - absorb unreceived IP datagram */
 408
 409 static void sock_sink(fd)
 410 int     fd;
 411 {
 412     char    buf[BUFSIZ];
 413 #ifdef INET6
 414     struct sockaddr_storage sin;
 415 #else
 416     struct sockaddr_in sin;
 417 #endif
 418     int     size = sizeof(sin);
 419
 420     /*
 421      * Eat up the not-yet received datagram. Some systems insist on a
 422      * non-zero source address argument in the recvfrom() call below.
 423      */
 424
 425     (void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & sin, &size);
 426 }