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 int
  48 realhostname(char *host, size_t hsize, const struct in_addr *ip)
  49 {
  50         char trimmed[MAXHOSTNAMELEN];
  51         int result;
  52         struct hostent *hp;
  53
  54         result = HOSTNAME_INVALIDADDR;
  55         hp = gethostbyaddr((const char *)ip, sizeof(*ip), AF_INET);
  56
  57         if (hp != NULL) {
  58                 strlcpy(trimmed, hp->h_name, sizeof(trimmed));
  59                 trimdomain(trimmed, strlen(trimmed));
  60                 if (strlen(trimmed) <= hsize) {
  61                         char lookup[MAXHOSTNAMELEN];
  62
  63                         strncpy(lookup, hp->h_name, sizeof(lookup) - 1);
  64                         lookup[sizeof(lookup) - 1] = '\0';
  65                         hp = gethostbyname(lookup);
  66                         if (hp == NULL)
  67                                 result = HOSTNAME_INVALIDNAME;
  68                         else for (; ; hp->h_addr_list++) {
  69                                 if (*hp->h_addr_list == NULL) {
  70                                         result = HOSTNAME_INCORRECTNAME;
  71                                         break;
  72                                 }
  73                                 if (!memcmp(*hp->h_addr_list, ip, sizeof(*ip))) {
  74                                         strncpy(host, trimmed, hsize);
  75                                         return HOSTNAME_FOUND;
  76                                 }
  77                         }
  78                 }
  79         }
  80
  81         strncpy(host, inet_ntoa(*ip), hsize);
  82
  83         return result;
  84 }
  85
  86 int
  87 realhostname_sa(char *host, size_t hsize, struct sockaddr *addr, int addrlen)
  88 {
  89         int result, error;
  90         char buf[NI_MAXHOST];
  91
  92         result = HOSTNAME_INVALIDADDR;
  93
  94 #ifdef INET6
  95         /* IPv4 mapped IPv6 addr consideraton, specified in rfc2373. */
  96         if (addr->sa_family == AF_INET6 &&
  97             addrlen == sizeof(struct sockaddr_in6) &&
  98             IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)addr)->sin6_addr)) {
  99                 struct sockaddr_in6 *sin6;
 100
 101                 sin6 = (struct sockaddr_in6 *)addr;
 102
 103                 memset(&lsin, 0, sizeof(lsin));
 104                 lsin.sin_len = sizeof(struct sockaddr_in);
 105                 lsin.sin_family = AF_INET;
 106                 lsin.sin_port = sin6->sin6_port;
 107                 memcpy(&lsin.sin_addr, &sin6->sin6_addr.s6_addr[12],
 108                        sizeof(struct in_addr));
 109                 addr = (struct sockaddr *)&lsin;
 110                 addrlen = lsin.sin_len;
 111         }
 112 #endif
 113
 114         error = getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 115                             NI_NAMEREQD);
 116         if (error == 0) {
 117                 struct addrinfo hints, *res, *ores;
 118                 struct sockaddr *sa;
 119
 120                 memset(&hints, 0, sizeof(struct addrinfo));
 121                 hints.ai_family = addr->sa_family;
 122                 hints.ai_flags = AI_CANONNAME | AI_PASSIVE;
 123                 hints.ai_socktype = SOCK_STREAM;
 124
 125                 error = getaddrinfo(buf, NULL, &hints, &res);
 126                 if (error) {
 127                         result = HOSTNAME_INVALIDNAME;
 128                         goto numeric;
 129                 }
 130                 for (ores = res; ; res = res->ai_next) {
 131                         if (res == NULL) {
 132                                 freeaddrinfo(ores);
 133                                 result = HOSTNAME_INCORRECTNAME;
 134                                 goto numeric;
 135                         }
 136                         sa = res->ai_addr;
 137                         if (sa == NULL) {
 138                                 freeaddrinfo(ores);
 139                                 result = HOSTNAME_INCORRECTNAME;
 140                                 goto numeric;
 141                         }
 142                         if (sa->sa_len == addrlen &&
 143                             sa->sa_family == addr->sa_family) {
 144                                 ((struct sockinet *)sa)->si_port = ((struct sockinet *)addr)->si_port;
 145 #ifdef INET6
 146                                 /*
 147                                  * XXX: sin6_socpe_id may not been
 148                                  * filled by DNS
 149                                  */
 150                                 if (sa->sa_family == AF_INET6 &&
 151                                     ((struct sockaddr_in6 *)sa)->sin6_scope_id == 0)
 152                                         ((struct sockaddr_in6 *)sa)->sin6_scope_id = ((struct sockaddr_in6 *)addr)->sin6_scope_id;
 153 #endif
 154                                 if (!memcmp(sa, addr, sa->sa_len)) {
 155                                         result = HOSTNAME_FOUND;
 156                                         if (ores->ai_canonname == NULL) {
 157                                                 freeaddrinfo(ores);
 158                                                 goto numeric;
 159                                         }
 160                                         strlcpy(buf, ores->ai_canonname,
 161                                                 sizeof(buf));
 162                                         trimdomain(buf, hsize);
 163                                         if (strlen(buf) > hsize &&
 164                                             addr->sa_family == AF_INET) {
 165                                                 freeaddrinfo(ores);
 166                                                 goto numeric;
 167                                         }
 168                                         strncpy(host, buf, hsize);
 169                                         break;
 170                                 }
 171                         }
 172                 }
 173                 freeaddrinfo(ores);
 174         } else {
 175     numeric:
 176                 if (getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 177                                 NI_NUMERICHOST) == 0)
 178                         strncpy(host, buf, hsize);
 179         }
 180
 181         return result;
 182 }
 183
 184