usr/src/lib/libwrap/socket.c

   1 /*
   2  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
   3  * Use is subject to license terms.
   4  */
   5
   6 #pragma ident   "%Z%%M% %I%     %E% SMI"
   7
   8  /*
   9   * This module determines the type of socket (datagram, stream), the client
  10   * socket address and port, the server socket address and port. In addition,
  11   * it provides methods to map a transport address to a printable host name
  12   * or address. Socket address information results are in static memory.
  13   *
  14   * The result from the hostname lookup method is STRING_PARANOID when a host
  15   * pretends to have someone elses name, or when a host name is available but
  16   * could not be verified.
  17   *
  18   * When lookup or conversion fails the result is set to STRING_UNKNOWN.
  19   *
  20   * Diagnostics are reported through syslog(3).
  21   *
  22   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  23   */
  24
  25 static char sccsid[] = "@(#) socket.c 1.15 97/03/21 19:27:24";
  26
  27 /* System libraries. */
  28
  29 #include <sys/types.h>
  30 #include <sys/param.h>
  31 #include <sys/socket.h>
  32 #include <netinet/in.h>
  33 #include <arpa/inet.h>
  34 #include <netdb.h>
  35 #include <stdio.h>
  36 #include <syslog.h>
  37 #include <string.h>
  38
  39 extern char *inet_ntoa();
  40
  41 /* Local stuff. */
  42
  43 #include "tcpd.h"
  44
  45 /* Forward declarations. */
  46
  47 static void sock_sink();
  48
  49 #ifdef APPEND_DOT
  50
  51  /*
  52   * Speed up DNS lookups by terminating the host name with a dot. Should be
  53   * done with care. The speedup can give problems with lookups from sources
  54   * that lack DNS-style trailing dot magic, such as local files or NIS maps.
  55   */
  56
  57 static struct hostent *tcpd_gethostbyname_dot(name, af)
  58 char   *name;
  59 int af;
  60 {
  61     char    dot_name[MAXHOSTNAMELEN + 1];
  62
  63     /*
  64      * Don't append dots to unqualified names. Such names are likely to come
  65      * from local hosts files or from NIS.
  66      */
  67
  68     if (strchr(name, '.') == 0 || strlen(name) >= MAXHOSTNAMELEN - 1) {
  69         return (tcpd_gethostbyname(name, af));
  70     } else {
  71         sprintf(dot_name, "%s.", name);
  72         return (tcpd_gethostbyname(dot_name, af));
  73     }
  74 }
  75
  76 #define tcpd_gethostbyname tcpd_gethostbyname_dot
  77 #endif
  78
  79 /* sock_host - look up endpoint addresses and install conversion methods */
  80
  81 void    sock_host(request)
  82 struct request_info *request;
  83 {
  84     static struct sockaddr_gen client;
  85     static struct sockaddr_gen server;
  86     socklen_t len;
  87     char    buf[BUFSIZ];
  88     int     fd = request->fd;
  89
  90     sock_methods(request);
  91
  92     /*
  93      * Look up the client host address. Hal R. Brand <BRAND@addvax.llnl.gov>
  94      * suggested how to get the client host info in case of UDP connections:
  95      * peek at the first message without actually looking at its contents. We
  96      * really should verify that client.sin_family gets the value AF_INET,
  97      * but this program has already caused too much grief on systems with
  98      * broken library code.
  99      */
 100
 101     len = sizeof(client);
 102     if (getpeername(fd, (struct sockaddr *) & client, &len) < 0) {
 103         request->sink = sock_sink;
 104         len = sizeof(client);
 105         if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK,
 106                      (struct sockaddr *) & client, &len) < 0) {
 107             tcpd_warn("can't get client address: %m");
 108             return;                             /* give up */
 109         }
 110 #ifdef really_paranoid
 111         memset(buf, 0 sizeof(buf));
 112 #endif
 113     }
 114     sockgen_simplify(&client);
 115     request->client->sin = &client;
 116
 117     /*
 118      * Determine the server binding. This is used for client username
 119      * lookups, and for access control rules that trigger on the server
 120      * address or name.
 121      */
 122
 123     len = sizeof(server);
 124     if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) {
 125         tcpd_warn("getsockname: %m");
 126         return;
 127     }
 128     sockgen_simplify(&server);
 129     request->server->sin = &server;
 130 }
 131
 132 /* sock_hostaddr - map endpoint address to printable form */
 133
 134 void    sock_hostaddr(host)
 135 struct host_info *host;
 136 {
 137     struct sockaddr_gen *sin = host->sin;
 138
 139     if (sin != 0)
 140 #ifdef HAVE_IPV6
 141
 142         (void) inet_ntop(SGFAM(sin), SGADDRP(sin), host->addr, sizeof(host->addr));
 143 #else
 144         STRN_CPY(host->addr, inet_ntoa(sin->sg_sin.sin_addr), sizeof(host->addr));
 145 #endif
 146 }
 147
 148 /* sock_hostname - map endpoint address to host name */
 149
 150 void    sock_hostname(host)
 151 struct host_info *host;
 152 {
 153     struct sockaddr_gen *sin = host->sin;
 154     struct hostent *hp;
 155     int     i;
 156     int     herr;
 157
 158     /*
 159      * On some systems, for example Solaris 2.3, gethostbyaddr(0.0.0.0) does
 160      * not fail. Instead it returns "INADDR_ANY". Unfortunately, this does
 161      * not work the other way around: gethostbyname("INADDR_ANY") fails. We
 162      * have to special-case 0.0.0.0, in order to avoid false alerts from the
 163      * host name/address checking code below.
 164      */
 165     if (sin != 0
 166         && !SG_IS_UNSPECIFIED(sin)
 167         && (hp = gethostbyaddr(SGADDRP(sin), SGADDRSZ(sin), SGFAM(sin))) != 0) {
 168
 169         STRN_CPY(host->name, hp->h_name, sizeof(host->name));
 170
 171         /*
 172          * Verify that the address is a member of the address list returned
 173          * by gethostbyname(hostname).
 174          *
 175          * Verify also that gethostbyaddr() and gethostbyname() return the same
 176          * hostname, or rshd and rlogind may still end up being spoofed.
 177          *
 178          * On some sites, gethostbyname("localhost") returns "localhost.domain".
 179          * This is a DNS artefact. We treat it as a special case. When we
 180          * can't believe the address list from gethostbyname("localhost")
 181          * we're in big trouble anyway.
 182          */
 183
 184         if ((hp = tcpd_gethostbyname(host->name, SGFAM(sin))) == 0) {
 185
 186             /*
 187              * Unable to verify that the host name matches the address. This
 188              * may be a transient problem or a botched name server setup.
 189              */
 190
 191             tcpd_warn("can't verify hostname: gethostbyname(%s) failed",
 192                       host->name);
 193
 194         } else if (STR_NE(host->name, hp->h_name)
 195                    && STR_NE(host->name, "localhost")) {
 196
 197             /*
 198              * The gethostbyaddr() and gethostbyname() calls did not return
 199              * the same hostname. This could be a nameserver configuration
 200              * problem. It could also be that someone is trying to spoof us.
 201              */
 202
 203             tcpd_warn("host name/name mismatch: %s != %.*s",
 204                       host->name, STRING_LENGTH, hp->h_name);
 205
 206         } else {
 207 #ifdef HAVE_IPV6
 208             char buf[INET6_ADDRSTRLEN];
 209 #endif
 210
 211             /*
 212              * The address should be a member of the address list returned by
 213              * gethostbyname(). We should first verify that the h_addrtype
 214              * field is AF_INET, but this program has already caused too much
 215              * grief on systems with broken library code.
 216              */
 217
 218             for (i = 0; hp->h_addr_list[i]; i++) {
 219                 if (memcmp(hp->h_addr_list[i],
 220                            (char *) SGADDRP(sin),
 221                            SGADDRSZ(sin)) == 0) {
 222                     return;                     /* name is good, keep it */
 223                 }
 224             }
 225
 226             /*
 227              * The host name does not map to the initial address. Perhaps
 228              * someone has messed up. Perhaps someone compromised a name
 229              * server.
 230              */
 231             tcpd_warn("host name/address mismatch: %s != %.*s",
 232 #ifdef HAVE_IPV6
 233                       inet_ntop(SGFAM(sin), SGADDRP(sin), buf, sizeof(buf)),
 234 #else
 235                       inet_ntoa(sin->sg_sin.sin_addr),
 236 #endif
 237                       STRING_LENGTH, hp->h_name);
 238         }
 239         strcpy(host->name, paranoid);           /* name is bad, clobber it */
 240     }
 241 }
 242
 243 /* sock_sink - absorb unreceived IP datagram */
 244
 245 static void sock_sink(fd)
 246 int     fd;
 247 {
 248     char    buf[BUFSIZ];
 249     struct sockaddr_in sin;
 250     socklen_t size = sizeof(sin);
 251
 252     /*
 253      * Eat up the not-yet received datagram. Some systems insist on a
 254      * non-zero source address argument in the recvfrom() call below.
 255      */
 256
 257     (void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & sin, &size);
 258 }
 259
 260 /*
 261  * If we receive a V4 connection on a V6 socket, we pretend we really
 262  * got a V4 connection.
 263  */
 264 void sockgen_simplify(sg)
 265 sockaddr_gen *sg;
 266 {
 267 #ifdef HAVE_IPV6
 268     if (sg->sg_family == AF_INET6 &&
 269         IN6_IS_ADDR_V4MAPPED(&sg->sg_sin6.sin6_addr)) {
 270             struct sockaddr_in v4_addr;
 271
 272 #ifdef IN6_V4MAPPED_TO_INADDR                   /* Solaris 8 */
 273             IN6_V4MAPPED_TO_INADDR(&sg->sg_sin6.sin6_addr, &v4_addr.sin_addr);
 274 #elif defined(IN6_MAPPED_TO_V4)                 /* Solaris 8 Beta only? */
 275             IN6_MAPPED_TO_V4(&sg->sg_sin6.sin6_addr, &v4_addr.sin_addr);
 276 #else                                           /* Do it the hard way */
 277             memcpy(&v4_addr.sin_addr, ((char*) &sg->sg_sin6.sin6_addr) + 12, 4);
 278 #endif
 279             v4_addr.sin_port = sg->sg_sin6.sin6_port;
 280             v4_addr.sin_family = AF_INET;
 281             memcpy(&sg->sg_sin, &v4_addr, sizeof(v4_addr));
 282     }
 283 #else
 284     return;
 285 #endif /* HAVE_IPV6 */
 286 }