/*      $NetBSD: socket.c,v 1.19 2012/03/21 10:10:37 matt Exp $ */

/*
 * This module determines the type of socket (datagram, stream), the client
 * socket address and port, the server socket address and port. In addition,
 * it provides methods to map a transport address to a printable host name
 * or address. Socket address information results are in static memory.
 *
 * The result from the hostname lookup method is STRING_PARANOID when a host
 * pretends to have someone elses name, or when a host name is available but
 * could not be verified.
 *
 * When lookup or conversion fails the result is set to STRING_UNKNOWN.
 *
 * Diagnostics are reported through syslog(3).
 *
 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
 */

#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#) socket.c 1.15 97/03/21 19:27:24";
#else
__RCSID("$NetBSD: socket.c,v 1.19 2012/03/21 10:10:37 matt Exp $");
#endif
#endif

/* System libraries. */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <syslog.h>
#include <string.h>
#include <arpa/inet.h>

/* Local stuff. */

#include "tcpd.h"

/* Forward declarations. */

#ifdef APPEND_DOT
static const char *append_dot __P((const char *));
#endif
static void sock_sink __P((int));

#ifdef APPEND_DOT
/*
 * Speed up DNS lookups by terminating the host name with a dot. Should be
 * done with care. The speedup can give problems with lookups from sources
 * that lack DNS-style trailing dot magic, such as local files or NIS maps.
 */

static const char *
append_dot(name)
const char *name;
{
   static char hbuf[MAXHOSTNAMELEN + 1];

   /*
    * Don't append dots to unqualified names. Such names are likely to come
    * from local hosts files or from NIS.
    */

   if (strchr(name, '.') == 0 || strlen(name) + 2 > sizeof(hbuf))
       strlcpy(hbuf, name, sizeof(hbuf));
   else
       (void)snprintf(hbuf, sizeof(hbuf), "%s.", name);
   return hbuf;
}
#endif

/* sock_host - look up endpoint addresses and install conversion methods */

void
sock_host(struct request_info *request)
{
   static struct sockaddr_storage client;
   static struct sockaddr_storage server;
   socklen_t     len;
   char    buf[BUFSIZ];
   int     fd = request->fd;

   sock_methods(request);

   /*
    * Look up the client host address. Hal R. Brand <[email protected]>
    * suggested how to get the client host info in case of UDP connections:
    * peek at the first message without actually looking at its contents. We
    * really should verify that client.sin_family gets the value AF_INET,
    * but this program has already caused too much grief on systems with
    * broken library code.
    *
    * XXX the last sentence is untrue as we support AF_INET6 as well :-)
    */

   if (request->client->sin == NULL) {
       len = sizeof(client);
       if (getpeername(fd, (struct sockaddr *)(void *)& client, &len) < 0) {
           request->sink = sock_sink;
           len = sizeof(client);
           if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK,
                        (struct sockaddr *) & client, &len) < 0) {
               tcpd_warn("can't get client address: %m");
               return;                         /* give up */
           }
#ifdef really_paranoid
           memset(buf, 0, sizeof(buf));
#endif
       }
       request->client->sin = (struct sockaddr *)&client;
   }

   /*
    * Determine the server binding. This is used for client username
    * lookups, and for access control rules that trigger on the server
    * address or name.
    */

   if (request->server->sin == NULL) {
       len = sizeof(server);
       if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) {
           tcpd_warn("getsockname: %m");
           return;
       }
       request->server->sin = (struct sockaddr *)&server;
   }
}

/* sock_hostaddr - map endpoint address to printable form */

void
sock_hostaddr(struct host_info *host)
{
   struct sockaddr *sa = host->sin;

   if (!sa)
       return;
   host->addr[0] = '\0';
   getnameinfo(sa, sa->sa_len, host->addr, sizeof(host->addr),
       NULL, 0, NI_NUMERICHOST);
}

/* sock_hostname - map endpoint address to host name */

void
sock_hostname(struct host_info *host)
{
   struct sockaddr *sa = host->sin;
   char h1[NI_MAXHOST], h2[NI_MAXHOST];
   struct addrinfo hints, *res, *res0;
#ifdef INET6
   struct sockaddr_in tmp;
#endif

   if (!sa)
       return;
#ifdef INET6
   /* special case on reverse lookup: mapped addr.  I hate it */
   if (sa->sa_family == AF_INET6 &&
       IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)sa)->sin6_addr)) {
       memset(&tmp, 0, sizeof(tmp));
       tmp.sin_family = AF_INET;
       tmp.sin_len = sizeof(struct sockaddr_in);
       memcpy(&tmp.sin_addr,
           &((struct sockaddr_in6 *)sa)->sin6_addr.s6_addr[12], 4);
       sa = (struct sockaddr *)&tmp;
   }
#endif
   if (getnameinfo(sa, sa->sa_len, h1, sizeof(h1), NULL, 0,
       NI_NUMERICHOST) != 0) {
       return;
   }
   if (getnameinfo(sa, sa->sa_len, host->name, sizeof(host->name), NULL, 0,
       NI_NAMEREQD) == 0) {
       /*
        * if reverse lookup result looks like a numeric hostname,
        * someone is trying to trick us by PTR record like following:
        *      1.1.1.10.in-addr.arpa.  IN PTR  2.3.4.5
        */
       memset(&hints, 0, sizeof(hints));
       hints.ai_socktype = SOCK_DGRAM; /*dummy*/
       hints.ai_flags = AI_NUMERICHOST;
#ifdef APPEND_DOT
       if (getaddrinfo(append_dot(host->name), "0", &hints, &res0) == 0)
#else
       if (getaddrinfo(host->name, "0", &hints, &res0) == 0)
#endif
       {
           tcpd_warn("Nasty PTR record is configured");
           freeaddrinfo(res0);
           /* name is bad, clobber it */
           (void)strlcpy(host->name, paranoid, sizeof(host->name));
           return;
       }

       /*
        * Verify that the address is a member of the address list returned
        * by getaddrinfo(hostname).
        *
        * Verify also that getnameinfo() and getaddrinfo() return the same
        * hostname, or rshd and rlogind may still end up being spoofed.
        *
        * On some sites, getaddrinfo("localhost") returns "localhost.domain".
        * This is a DNS artefact. We treat it as a special case. When we
        * can't believe the address list from getaddrinfo("localhost")
        * we're in big trouble anyway.
        */
       memset(&hints, 0, sizeof(hints));
       hints.ai_family = sa->sa_family;
       hints.ai_socktype = SOCK_DGRAM; /*dummy*/
       hints.ai_flags = AI_CANONNAME;
#ifdef APPEND_DOT
       if (getaddrinfo(append_dot(host->name), "0", &hints, &res0) != 0)
#else
       if (getaddrinfo(host->name, "0", &hints, &res0) != 0)
#endif
       {
           /*
            * Unable to verify that the host name matches the address. This
            * may be a transient problem or a botched name server setup.
            */

           tcpd_warn("can't verify hostname: getaddrinfo(%s, %d) failed",
               host->name, hints.ai_family);
       } else if (res0->ai_canonname &&
           STR_NE(host->name, res0->ai_canonname) &&
           STR_NE(host->name, "localhost")) {
           /*
            * The getnameinfo() and getaddrinfo() calls did not return
            * the same hostname. This could be a nameserver configuration
            * problem. It could also be that someone is trying to spoof us.
            */

           tcpd_warn("host name/name mismatch: %s != %s",
               host->name, res0->ai_canonname);
           freeaddrinfo(res0);
       } else {
           /*
            * The address should be a member of the address list returned by
            * getaddrinfo().
            */

           for (res = res0; res; res = res->ai_next) {
               if (getnameinfo(res->ai_addr, res->ai_addrlen, h2, sizeof(h2),
                   NULL, 0, NI_NUMERICHOST) != 0) {
                   continue;
               }
               if (STR_EQ(h1, h2)) {
                   freeaddrinfo(res0);
                   return;
               }
           }

           /*
            * The host name does not map to the initial address. Perhaps
            * someone has messed up. Perhaps someone compromised a name
            * server.
            */

           tcpd_warn("host name/address mismatch: %s != %s", h1,
               res0->ai_canonname ? res0->ai_canonname : "?");

           freeaddrinfo(res0);
       }
       /* name is bad, clobber it */
       (void)strlcpy(host->name, paranoid, sizeof(host->name));
   }
}

/* sock_sink - absorb unreceived IP datagram */

static void
sock_sink(int fd)
{
   char    buf[BUFSIZ];
   struct sockaddr_storage ss;
   socklen_t size = sizeof(ss);

   /*
    * Eat up the not-yet received datagram. Some systems insist on a
    * non-zero source address argument in the recvfrom() call below.
    */

   (void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & ss, &size);
}

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