lib/libutil/realhostname.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause
   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/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                         strlcpy(lookup, hp->h_name, sizeof(lookup));
  64                         hp = gethostbyname(lookup);
  65                         if (hp == NULL)
  66                                 result = HOSTNAME_INVALIDNAME;
  67                         else for (; ; hp->h_addr_list++) {
  68                                 if (*hp->h_addr_list == NULL) {
  69                                         result = HOSTNAME_INCORRECTNAME;
  70                                         break;
  71                                 }
  72                                 if (!memcmp(*hp->h_addr_list, ip, sizeof(*ip))) {
  73                                         strncpy(host, trimmed, hsize);
  74                                         return HOSTNAME_FOUND;
  75                                 }
  76                         }
  77                 }
  78         }
  79
  80         strncpy(host, inet_ntoa(*ip), hsize);
  81
  82         return result;
  83 }
  84
  85 /*
  86  * struct sockaddr has very lax alignment requirements, since all its
  87  * members are char or equivalent.  This is a problem when trying to
  88  * dereference a struct sockaddr_in6 * that was passed in as a struct
  89  * sockaddr *.  Although we know (or trust) that the passed-in struct was
  90  * properly aligned, the compiler doesn't, and (rightly) complains.  These
  91  * macros perform the cast in a way that the compiler will accept.
  92  */
  93 #define SOCKADDR_IN6(p) ((struct sockaddr_in6 *)(void *)(p))
  94 #define SOCKADDR_IN(p) ((struct sockaddr_in *)(void *)(p))
  95 #define SOCKINET(p) ((struct sockinet *)(void *)(p))
  96
  97 int
  98 realhostname_sa(char *host, size_t hsize, struct sockaddr *addr, int addrlen)
  99 {
 100         int result, error;
 101         char buf[NI_MAXHOST];
 102 #ifdef INET6
 103         struct sockaddr_in lsin;
 104 #endif
 105
 106         result = HOSTNAME_INVALIDADDR;
 107
 108 #ifdef INET6
 109         /* IPv4 mapped IPv6 addr consideraton, specified in rfc2373. */
 110         if (addr->sa_family == AF_INET6 &&
 111             addrlen == sizeof(struct sockaddr_in6) &&
 112             IN6_IS_ADDR_V4MAPPED(&SOCKADDR_IN6(addr)->sin6_addr)) {
 113                 struct sockaddr_in6 *sin6;
 114
 115                 sin6 = SOCKADDR_IN6(addr);
 116
 117                 memset(&lsin, 0, sizeof(lsin));
 118                 lsin.sin_len = sizeof(struct sockaddr_in);
 119                 lsin.sin_family = AF_INET;
 120                 lsin.sin_port = sin6->sin6_port;
 121                 memcpy(&lsin.sin_addr, &sin6->sin6_addr.s6_addr[12],
 122                        sizeof(struct in_addr));
 123                 addr = (struct sockaddr *)&lsin;
 124                 addrlen = lsin.sin_len;
 125         }
 126 #endif
 127
 128         error = getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 129                             NI_NAMEREQD);
 130         if (error == 0) {
 131                 struct addrinfo hints, *res, *ores;
 132                 struct sockaddr *sa;
 133
 134                 memset(&hints, 0, sizeof(struct addrinfo));
 135                 hints.ai_family = addr->sa_family;
 136                 hints.ai_flags = AI_CANONNAME | AI_PASSIVE;
 137                 hints.ai_socktype = SOCK_STREAM;
 138
 139                 error = getaddrinfo(buf, NULL, &hints, &res);
 140                 if (error) {
 141                         result = HOSTNAME_INVALIDNAME;
 142                         goto numeric;
 143                 }
 144                 for (ores = res; ; res = res->ai_next) {
 145                         if (res == NULL) {
 146                                 freeaddrinfo(ores);
 147                                 result = HOSTNAME_INCORRECTNAME;
 148                                 goto numeric;
 149                         }
 150                         sa = res->ai_addr;
 151                         if (sa == NULL) {
 152                                 freeaddrinfo(ores);
 153                                 result = HOSTNAME_INCORRECTNAME;
 154                                 goto numeric;
 155                         }
 156                         if (sa->sa_len == addrlen &&
 157                             sa->sa_family == addr->sa_family) {
 158                                 SOCKINET(sa)->si_port = SOCKINET(addr)->si_port;
 159 #ifdef INET6
 160                                 /*
 161                                  * XXX: sin6_socpe_id may not been
 162                                  * filled by DNS
 163                                  */
 164                                 if (sa->sa_family == AF_INET6 &&
 165                                     SOCKADDR_IN6(sa)->sin6_scope_id == 0)
 166                                         SOCKADDR_IN6(sa)->sin6_scope_id =
 167                                             SOCKADDR_IN6(addr)->sin6_scope_id;
 168 #endif
 169                                 if (!memcmp(sa, addr, sa->sa_len)) {
 170                                         result = HOSTNAME_FOUND;
 171                                         if (ores->ai_canonname == NULL) {
 172                                                 freeaddrinfo(ores);
 173                                                 goto numeric;
 174                                         }
 175                                         strlcpy(buf, ores->ai_canonname,
 176                                                 sizeof(buf));
 177                                         trimdomain(buf, hsize);
 178                                         if (strlen(buf) > hsize &&
 179                                             addr->sa_family == AF_INET) {
 180                                                 freeaddrinfo(ores);
 181                                                 goto numeric;
 182                                         }
 183                                         strncpy(host, buf, hsize);
 184                                         break;
 185                                 }
 186                         }
 187                 }
 188                 freeaddrinfo(ores);
 189         } else {
 190     numeric:
 191                 if (getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
 192                                 NI_NUMERICHOST) == 0)
 193                         strncpy(host, buf, hsize);
 194         }
 195
 196         return result;
 197 }
 198
 199