realhostname.c

   1 /*-
   2  * Copyright (c) 1999 Brian Somers <brian@Awfulhak.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  */
  26
  27 #include <sys/cdefs.h>
  28
  29 #include <sys/param.h>
  30 #include <sys/socket.h>
  31
  32 #include <netdb.h>
  33 #include <netinet/in.h>
  34 #include <arpa/inet.h>
  35
  36 #include <stdio.h>
  37 #include <string.h>
  38
  39 #include "libutil.h"
  40
  41 struct sockinet {
  42         u_char  si_len;
  43         u_char  si_family;
  44         u_short si_port;
  45 };
  46
  47 void trimdomain(char *_fullhost, size_t _hostsize);
  48
  49 int
  50 realhostname(char *host, size_t hsize, const struct in_addr *ip)
  51 {
  52         char trimmed[MAXHOSTNAMELEN];
  53         int result;
  54         struct hostent *hp;
  55
  56         result = HOSTNAME_INVALIDADDR;
  57         hp = gethostbyaddr((const char *)ip, sizeof(*ip), AF_INET);
  58
  59         if (hp != NULL) {
  60                 strlcpy(trimmed, hp->h_name, sizeof(trimmed));
  61                 trimdomain(trimmed, strlen(trimmed));
  62                 if (strlen(trimmed) <= hsize) {
  63                         char lookup[MAXHOSTNAMELEN];
  64
  65                         strncpy(lookup, hp->h_name, sizeof(lookup) - 1);
  66                         lookup[sizeof(lookup) - 1] = '\0';
  67                         hp = gethostbyname(lookup);
  68                         if (hp == NULL)
  69                                 result = HOSTNAME_INVALIDNAME;
  70                         else for (; ; hp->h_addr_list++) {
  71                                 if (*hp->h_addr_list == NULL) {
  72                                         result = HOSTNAME_INCORRECTNAME;
  73                                         break;
  74                                 }
  75                                 if (!memcmp(*hp->h_addr_list, ip, sizeof(*ip))) {
  76                                         strncpy(host, trimmed, hsize);
  77                                         return HOSTNAME_FOUND;
  78                                 }
  79                         }
  80                 }
  81         }
  82
  83         strncpy(host, inet_ntoa(*ip), hsize);
  84
  85         return result;
  86 }
  87
  88 int
  89 realhostname_sa(char *host, size_t hsize, struct sockaddr *addr, int addrlen)
  90 {
  91         int result, error;
  92         char buf[NI_MAXHOST];
  93
  94         result = HOSTNAME_INVALIDADDR;
  95
  96 #ifdef INET6
  97         /* IPv4 mapped IPv6 addr consideraton, specified in rfc2373. */
  98         if (addr->sa_family == AF_INET6 &&
  99             addrlen == sizeof(struct sockaddr_in6) &&
 100             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)addr)->sin6_addr)) {
 101                 struct sockaddr_in6 *sin6;
 102
 103                 sin6 = (struct sockaddr_in6 *)addr;
 104
 105                 memset(&lsin, 0, sizeof(lsin));
 106                 lsin.sin_len = sizeof(struct sockaddr_in);
 107                 lsin.sin_family = AF_INET;
 108                 lsin.sin_port = sin6->sin6_port;
 109                 memcpy(&lsin.sin_addr, &sin6->sin6_addr.s6_addr[12],
 110                        sizeof(struct in_addr));
 111                 addr = (struct sockaddr *)&lsin;
 112                 addrlen = lsin.sin_len;
 113         }
 114 #endif
 115
 116         error = getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 117                             NI_NAMEREQD);
 118         if (error == 0) {
 119                 struct addrinfo hints, *res, *ores;
 120                 struct sockaddr *sa;
 121
 122                 memset(&hints, 0, sizeof(struct addrinfo));
 123                 hints.ai_family = addr->sa_family;
 124                 hints.ai_flags = AI_CANONNAME | AI_PASSIVE;
 125                 hints.ai_socktype = SOCK_STREAM;
 126
 127                 error = getaddrinfo(buf, NULL, &hints, &res);
 128                 if (error) {
 129                         result = HOSTNAME_INVALIDNAME;
 130                         goto numeric;
 131                 }
 132                 for (ores = res; ; res = res->ai_next) {
 133                         if (res == NULL) {
 134                                 freeaddrinfo(ores);
 135                                 result = HOSTNAME_INCORRECTNAME;
 136                                 goto numeric;
 137                         }
 138                         sa = res->ai_addr;
 139                         if (sa == NULL) {
 140                                 freeaddrinfo(ores);
 141                                 result = HOSTNAME_INCORRECTNAME;
 142                                 goto numeric;
 143                         }
 144                         if (sa->sa_len == addrlen &&
 145                             sa->sa_family == addr->sa_family) {
 146                                 ((struct sockinet *)sa)->si_port = ((struct sockinet *)addr)->si_port;
 147 #ifdef INET6
 148                                 /*
 149                                  * XXX: sin6_socpe_id may not been
 150                                  * filled by DNS
 151                                  */
 152                                 if (sa->sa_family == AF_INET6 &&
 153                                     ((struct sockaddr_in6 *)sa)->sin6_scope_id == 0)
 154                                         ((struct sockaddr_in6 *)sa)->sin6_scope_id = ((struct sockaddr_in6 *)addr)->sin6_scope_id;
 155 #endif
 156                                 if (!memcmp(sa, addr, sa->sa_len)) {
 157                                         result = HOSTNAME_FOUND;
 158                                         if (ores->ai_canonname == NULL) {
 159                                                 freeaddrinfo(ores);
 160                                                 goto numeric;
 161                                         }
 162                                         strlcpy(buf, ores->ai_canonname,
 163                                                 sizeof(buf));
 164                                         trimdomain(buf, hsize);
 165                                         if (strlen(buf) > hsize &&
 166                                             addr->sa_family == AF_INET) {
 167                                                 freeaddrinfo(ores);
 168                                                 goto numeric;
 169                                         }
 170                                         strncpy(host, buf, hsize);
 171                                         break;
 172                                 }
 173                         }
 174                 }
 175                 freeaddrinfo(ores);
 176         } else {
 177     numeric:
 178                 if (getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 179                                 NI_NUMERICHOST) == 0)
 180                         strncpy(host, buf, hsize);
 181         }
 182
 183         return result;
 184 }
 185
 186