lib/libutil/realhostname.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 1999 Brian Somers <brian@Awfulhak.org>
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  */
  28
  29 #include <sys/cdefs.h>
  30 __FBSDID("$FreeBSD$");
  31
  32 #include <sys/param.h>
  33 #include <sys/socket.h>
  34
  35 #include <netdb.h>
  36 #include <netinet/in.h>
  37 #include <arpa/inet.h>
  38
  39 #include <stdio.h>
  40 #include <string.h>
  41
  42 #include "libutil.h"
  43
  44 struct sockinet {
  45         u_char  si_len;
  46         u_char  si_family;
  47         u_short si_port;
  48 };
  49
  50 int
  51 realhostname(char *host, size_t hsize, const struct in_addr *ip)
  52 {
  53         char trimmed[MAXHOSTNAMELEN];
  54         int result;
  55         struct hostent *hp;
  56
  57         result = HOSTNAME_INVALIDADDR;
  58         hp = gethostbyaddr((const char *)ip, sizeof(*ip), AF_INET);
  59
  60         if (hp != NULL) {
  61                 strlcpy(trimmed, hp->h_name, sizeof(trimmed));
  62                 trimdomain(trimmed, strlen(trimmed));
  63                 if (strlen(trimmed) <= hsize) {
  64                         char lookup[MAXHOSTNAMELEN];
  65
  66                         strlcpy(lookup, hp->h_name, sizeof(lookup));
  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 /*
  89  * struct sockaddr has very lax alignment requirements, since all its
  90  * members are char or equivalent.  This is a problem when trying to
  91  * dereference a struct sockaddr_in6 * that was passed in as a struct
  92  * sockaddr *.  Although we know (or trust) that the passed-in struct was
  93  * properly aligned, the compiler doesn't, and (rightly) complains.  These
  94  * macros perform the cast in a way that the compiler will accept.
  95  */
  96 #define SOCKADDR_IN6(p) ((struct sockaddr_in6 *)(void *)(p))
  97 #define SOCKADDR_IN(p) ((struct sockaddr_in *)(void *)(p))
  98 #define SOCKINET(p) ((struct sockinet *)(void *)(p))
  99
 100 int
 101 realhostname_sa(char *host, size_t hsize, struct sockaddr *addr, int addrlen)
 102 {
 103         int result, error;
 104         char buf[NI_MAXHOST];
 105 #ifdef INET6
 106         struct sockaddr_in lsin;
 107 #endif
 108
 109         result = HOSTNAME_INVALIDADDR;
 110
 111 #ifdef INET6
 112         /* IPv4 mapped IPv6 addr consideraton, specified in rfc2373. */
 113         if (addr->sa_family == AF_INET6 &&
 114             addrlen == sizeof(struct sockaddr_in6) &&
 115             IN6_IS_ADDR_V4MAPPED(&SOCKADDR_IN6(addr)->sin6_addr)) {
 116                 struct sockaddr_in6 *sin6;
 117
 118                 sin6 = SOCKADDR_IN6(addr);
 119
 120                 memset(&lsin, 0, sizeof(lsin));
 121                 lsin.sin_len = sizeof(struct sockaddr_in);
 122                 lsin.sin_family = AF_INET;
 123                 lsin.sin_port = sin6->sin6_port;
 124                 memcpy(&lsin.sin_addr, &sin6->sin6_addr.s6_addr[12],
 125                        sizeof(struct in_addr));
 126                 addr = (struct sockaddr *)&lsin;
 127                 addrlen = lsin.sin_len;
 128         }
 129 #endif
 130
 131         error = getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 132                             NI_NAMEREQD);
 133         if (error == 0) {
 134                 struct addrinfo hints, *res, *ores;
 135                 struct sockaddr *sa;
 136
 137                 memset(&hints, 0, sizeof(struct addrinfo));
 138                 hints.ai_family = addr->sa_family;
 139                 hints.ai_flags = AI_CANONNAME | AI_PASSIVE;
 140                 hints.ai_socktype = SOCK_STREAM;
 141
 142                 error = getaddrinfo(buf, NULL, &hints, &res);
 143                 if (error) {
 144                         result = HOSTNAME_INVALIDNAME;
 145                         goto numeric;
 146                 }
 147                 for (ores = res; ; res = res->ai_next) {
 148                         if (res == NULL) {
 149                                 freeaddrinfo(ores);
 150                                 result = HOSTNAME_INCORRECTNAME;
 151                                 goto numeric;
 152                         }
 153                         sa = res->ai_addr;
 154                         if (sa == NULL) {
 155                                 freeaddrinfo(ores);
 156                                 result = HOSTNAME_INCORRECTNAME;
 157                                 goto numeric;
 158                         }
 159                         if (sa->sa_len == addrlen &&
 160                             sa->sa_family == addr->sa_family) {
 161                                 SOCKINET(sa)->si_port = SOCKINET(addr)->si_port;
 162 #ifdef INET6
 163                                 /*
 164                                  * XXX: sin6_socpe_id may not been
 165                                  * filled by DNS
 166                                  */
 167                                 if (sa->sa_family == AF_INET6 &&
 168                                     SOCKADDR_IN6(sa)->sin6_scope_id == 0)
 169                                         SOCKADDR_IN6(sa)->sin6_scope_id =
 170                                             SOCKADDR_IN6(addr)->sin6_scope_id;
 171 #endif
 172                                 if (!memcmp(sa, addr, sa->sa_len)) {
 173                                         result = HOSTNAME_FOUND;
 174                                         if (ores->ai_canonname == NULL) {
 175                                                 freeaddrinfo(ores);
 176                                                 goto numeric;
 177                                         }
 178                                         strlcpy(buf, ores->ai_canonname,
 179                                                 sizeof(buf));
 180                                         trimdomain(buf, hsize);
 181                                         if (strlen(buf) > hsize &&
 182                                             addr->sa_family == AF_INET) {
 183                                                 freeaddrinfo(ores);
 184                                                 goto numeric;
 185                                         }
 186                                         strncpy(host, buf, hsize);
 187                                         break;
 188                                 }
 189                         }
 190                 }
 191                 freeaddrinfo(ores);
 192         } else {
 193     numeric:
 194                 if (getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 195                                 NI_NUMERICHOST) == 0)
 196                         strncpy(host, buf, hsize);
 197         }
 198
 199         return result;
 200 }
 201
 202