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
  27 #include <sys/cdefs.h>
  28 __FBSDID("$FreeBSD$");
  29
  30 #include <sys/param.h>
  31 #include <sys/socket.h>
  32
  33 #include <netdb.h>
  34 #include <netinet/in.h>
  35 #include <arpa/inet.h>
  36
  37 #include <stdio.h>
  38 #include <string.h>
  39
  40 #include "libutil.h"
  41
  42 struct sockinet {
  43         u_char  si_len;
  44         u_char  si_family;
  45         u_short si_port;
  46 };
  47
  48 int
  49 realhostname(char *host, size_t hsize, const struct in_addr *ip)
  50 {
  51         char trimmed[MAXHOSTNAMELEN];
  52         int result;
  53         struct hostent *hp;
  54
  55         result = HOSTNAME_INVALIDADDR;
  56         hp = gethostbyaddr((const char *)ip, sizeof(*ip), AF_INET);
  57
  58         if (hp != NULL) {
  59                 strlcpy(trimmed, hp->h_name, sizeof(trimmed));
  60                 trimdomain(trimmed, strlen(trimmed));
  61                 if (strlen(trimmed) <= hsize) {
  62                         char lookup[MAXHOSTNAMELEN];
  63
  64                         strlcpy(lookup, hp->h_name, sizeof(lookup));
  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 /*
  87  * struct sockaddr has very lax alignment requirements, since all its
  88  * members are char or equivalent.  This is a problem when trying to
  89  * dereference a struct sockaddr_in6 * that was passed in as a struct
  90  * sockaddr *.  Although we know (or trust) that the passed-in struct was
  91  * properly aligned, the compiler doesn't, and (rightly) complains.  These
  92  * macros perform the cast in a way that the compiler will accept.
  93  */
  94 #define SOCKADDR_IN6(p) ((struct sockaddr_in6 *)(void *)(p))
  95 #define SOCKADDR_IN(p) ((struct sockaddr_in *)(void *)(p))
  96 #define SOCKINET(p) ((struct sockinet *)(void *)(p))
  97
  98 int
  99 realhostname_sa(char *host, size_t hsize, struct sockaddr *addr, int addrlen)
 100 {
 101         int result, error;
 102         char buf[NI_MAXHOST];
 103 #ifdef INET6
 104         struct sockaddr_in lsin;
 105 #endif
 106
 107         result = HOSTNAME_INVALIDADDR;
 108
 109 #ifdef INET6
 110         /* IPv4 mapped IPv6 addr consideraton, specified in rfc2373. */
 111         if (addr->sa_family == AF_INET6 &&
 112             addrlen == sizeof(struct sockaddr_in6) &&
 113             IN6_IS_ADDR_V4MAPPED(&SOCKADDR_IN6(addr)->sin6_addr)) {
 114                 struct sockaddr_in6 *sin6;
 115
 116                 sin6 = SOCKADDR_IN6(addr);
 117
 118                 memset(&lsin, 0, sizeof(lsin));
 119                 lsin.sin_len = sizeof(struct sockaddr_in);
 120                 lsin.sin_family = AF_INET;
 121                 lsin.sin_port = sin6->sin6_port;
 122                 memcpy(&lsin.sin_addr, &sin6->sin6_addr.s6_addr[12],
 123                        sizeof(struct in_addr));
 124                 addr = (struct sockaddr *)&lsin;
 125                 addrlen = lsin.sin_len;
 126         }
 127 #endif
 128
 129         error = getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 130                             NI_NAMEREQD);
 131         if (error == 0) {
 132                 struct addrinfo hints, *res, *ores;
 133                 struct sockaddr *sa;
 134
 135                 memset(&hints, 0, sizeof(struct addrinfo));
 136                 hints.ai_family = addr->sa_family;
 137                 hints.ai_flags = AI_CANONNAME | AI_PASSIVE;
 138                 hints.ai_socktype = SOCK_STREAM;
 139
 140                 error = getaddrinfo(buf, NULL, &hints, &res);
 141                 if (error) {
 142                         result = HOSTNAME_INVALIDNAME;
 143                         goto numeric;
 144                 }
 145                 for (ores = res; ; res = res->ai_next) {
 146                         if (res == NULL) {
 147                                 freeaddrinfo(ores);
 148                                 result = HOSTNAME_INCORRECTNAME;
 149                                 goto numeric;
 150                         }
 151                         sa = res->ai_addr;
 152                         if (sa == NULL) {
 153                                 freeaddrinfo(ores);
 154                                 result = HOSTNAME_INCORRECTNAME;
 155                                 goto numeric;
 156                         }
 157                         if (sa->sa_len == addrlen &&
 158                             sa->sa_family == addr->sa_family) {
 159                                 SOCKINET(sa)->si_port = SOCKINET(addr)->si_port;
 160 #ifdef INET6
 161                                 /*
 162                                  * XXX: sin6_socpe_id may not been
 163                                  * filled by DNS
 164                                  */
 165                                 if (sa->sa_family == AF_INET6 &&
 166                                     SOCKADDR_IN6(sa)->sin6_scope_id == 0)
 167                                         SOCKADDR_IN6(sa)->sin6_scope_id =
 168                                             SOCKADDR_IN6(addr)->sin6_scope_id;
 169 #endif
 170                                 if (!memcmp(sa, addr, sa->sa_len)) {
 171                                         result = HOSTNAME_FOUND;
 172                                         if (ores->ai_canonname == NULL) {
 173                                                 freeaddrinfo(ores);
 174                                                 goto numeric;
 175                                         }
 176                                         strlcpy(buf, ores->ai_canonname,
 177                                                 sizeof(buf));
 178                                         trimdomain(buf, hsize);
 179                                         if (strlen(buf) > hsize &&
 180                                             addr->sa_family == AF_INET) {
 181                                                 freeaddrinfo(ores);
 182                                                 goto numeric;
 183                                         }
 184                                         strncpy(host, buf, hsize);
 185                                         break;
 186                                 }
 187                         }
 188                 }
 189                 freeaddrinfo(ores);
 190         } else {
 191     numeric:
 192                 if (getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 193                                 NI_NUMERICHOST) == 0)
 194                         strncpy(host, buf, hsize);
 195         }
 196
 197         return result;
 198 }
 199
 200