lib/libutil/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  * $FreeBSD: head/lib/libutil/realhostname.c 185277 2008-11-25 02:15:09Z avatar $
  27  */
  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 #include <libutil.h>
  39
  40 struct sockinet {
  41         u_char  si_len;
  42         u_char  si_family;
  43         u_short si_port;
  44 };
  45
  46 int
  47 realhostname(char *host, size_t hsize, const struct in_addr *ip)
  48 {
  49         char trimmed[MAXHOSTNAMELEN];
  50         int result;
  51         struct hostent *hp;
  52
  53         result = HOSTNAME_INVALIDADDR;
  54         hp = gethostbyaddr((const char *)ip, sizeof(*ip), AF_INET);
  55
  56         if (hp != NULL) {
  57                 strlcpy(trimmed, hp->h_name, sizeof(trimmed));
  58                 trimdomain(trimmed, strlen(trimmed));
  59                 if (strlen(trimmed) <= hsize) {
  60                         char lookup[MAXHOSTNAMELEN];
  61
  62                         strlcpy(lookup, hp->h_name, sizeof(lookup));
  63                         hp = gethostbyname(lookup);
  64                         if (hp == NULL)
  65                                 result = HOSTNAME_INVALIDNAME;
  66                         else for (; ; hp->h_addr_list++) {
  67                                 if (*hp->h_addr_list == NULL) {
  68                                         result = HOSTNAME_INCORRECTNAME;
  69                                         break;
  70                                 }
  71                                 if (!memcmp(*hp->h_addr_list, ip, sizeof(*ip))) {
  72                                         strncpy(host, trimmed, hsize);
  73                                         return HOSTNAME_FOUND;
  74                                 }
  75                         }
  76                 }
  77         }
  78
  79         strncpy(host, inet_ntoa(*ip), hsize);
  80
  81         return result;
  82 }
  83
  84 /*
  85  * struct sockaddr has very lax alignment requirements, since all its
  86  * members are char or equivalent.  This is a problem when trying to
  87  * dereference a struct sockaddr_in6 * that was passed in as a struct
  88  * sockaddr *.  Although we know (or trust) that the passed-in struct was
  89  * properly aligned, the compiler doesn't, and (rightly) complains.  These
  90  * macros perform the cast in a way that the compiler will accept.
  91  */
  92 #define SOCKADDR_IN6(p) ((struct sockaddr_in6 *)(void *)(p))
  93 #define SOCKADDR_IN(p) ((struct sockaddr_in *)(void *)(p))
  94 #define SOCKINET(p) ((struct sockinet *)(void *)(p))
  95
  96 int
  97 realhostname_sa(char *host, size_t hsize, struct sockaddr *addr, int addrlen)
  98 {
  99         int result, error;
 100         char buf[NI_MAXHOST];
 101 #ifdef INET6
 102         struct sockaddr_in lsin;
 103 #endif
 104
 105         result = HOSTNAME_INVALIDADDR;
 106
 107 #ifdef INET6
 108         /* IPv4 mapped IPv6 addr consideraton, specified in rfc2373. */
 109         if (addr->sa_family == AF_INET6 &&
 110             addrlen == sizeof(struct sockaddr_in6) &&
 111             IN6_IS_ADDR_V4MAPPED(&SOCKADDR_IN6(addr)->sin6_addr)) {
 112                 struct sockaddr_in6 *sin6;
 113
 114                 sin6 = SOCKADDR_IN6(addr);
 115
 116                 memset(&lsin, 0, sizeof(lsin));
 117                 lsin.sin_len = sizeof(struct sockaddr_in);
 118                 lsin.sin_family = AF_INET;
 119                 lsin.sin_port = sin6->sin6_port;
 120                 memcpy(&lsin.sin_addr, &sin6->sin6_addr.s6_addr[12],
 121                        sizeof(struct in_addr));
 122                 addr = (struct sockaddr *)&lsin;
 123                 addrlen = lsin.sin_len;
 124         }
 125 #endif
 126
 127         error = getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 128                             NI_NAMEREQD);
 129         if (error == 0) {
 130                 struct addrinfo hints, *res, *ores;
 131                 struct sockaddr *sa;
 132
 133                 memset(&hints, 0, sizeof(struct addrinfo));
 134                 hints.ai_family = addr->sa_family;
 135                 hints.ai_flags = AI_CANONNAME | AI_PASSIVE;
 136                 hints.ai_socktype = SOCK_STREAM;
 137
 138                 error = getaddrinfo(buf, NULL, &hints, &res);
 139                 if (error) {
 140                         result = HOSTNAME_INVALIDNAME;
 141                         goto numeric;
 142                 }
 143                 for (ores = res; ; res = res->ai_next) {
 144                         if (res == NULL) {
 145                                 freeaddrinfo(ores);
 146                                 result = HOSTNAME_INCORRECTNAME;
 147                                 goto numeric;
 148                         }
 149                         sa = res->ai_addr;
 150                         if (sa == NULL) {
 151                                 freeaddrinfo(ores);
 152                                 result = HOSTNAME_INCORRECTNAME;
 153                                 goto numeric;
 154                         }
 155                         if (sa->sa_len == addrlen &&
 156                             sa->sa_family == addr->sa_family) {
 157                                 SOCKINET(sa)->si_port = SOCKINET(addr)->si_port;
 158 #ifdef INET6
 159                                 /*
 160                                  * XXX: sin6_socpe_id may not been
 161                                  * filled by DNS
 162                                  */
 163                                 if (sa->sa_family == AF_INET6 &&
 164                                     SOCKADDR_IN6(sa)->sin6_scope_id == 0)
 165                                         SOCKADDR_IN6(sa)->sin6_scope_id =
 166                                             SOCKADDR_IN6(addr)->sin6_scope_id;
 167 #endif
 168                                 if (!memcmp(sa, addr, sa->sa_len)) {
 169                                         result = HOSTNAME_FOUND;
 170                                         if (ores->ai_canonname == NULL) {
 171                                                 freeaddrinfo(ores);
 172                                                 goto numeric;
 173                                         }
 174                                         strlcpy(buf, ores->ai_canonname,
 175                                                 sizeof(buf));
 176                                         trimdomain(buf, hsize);
 177                                         if (strlen(buf) > hsize &&
 178                                             addr->sa_family == AF_INET) {
 179                                                 freeaddrinfo(ores);
 180                                                 goto numeric;
 181                                         }
 182                                         strncpy(host, buf, hsize);
 183                                         break;
 184                                 }
 185                         }
 186                 }
 187                 freeaddrinfo(ores);
 188         } else {
 189     numeric:
 190                 if (getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 191                                 NI_NUMERICHOST) == 0)
 192                         strncpy(host, buf, hsize);
 193         }
 194
 195         return result;
 196 }
 197
 198