/* $NetBSD: res_query.c,v 1.37 2003/08/07 16:43:14 agc Exp $ */ /*- * Copyright (c) 1988, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * - * Portions Copyright (c) 1993 by Digital Equipment Corporation. * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies, and that * the name of Digital Equipment Corporation not be used in advertising or * publicity pertaining to distribution of the document or software without * specific, written prior permission. * * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS * SOFTWARE. * - * --Copyright-- */ #include #if defined(LIBC_SCCS) && !defined(lint) #if 0 static char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93"; static char rcsid[] = "Id: res_query.c,v 8.10 1997/06/01 20:34:37 vixie Exp "; #else __RCSID("$NetBSD: res_query.c,v 1.37 2003/08/07 16:43:14 agc Exp $"); #endif #endif /* LIBC_SCCS and not lint */ #if defined(_LIBC) #include "namespace.h" #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #if defined(_LIBC) && defined(__weak_alias) __weak_alias(res_query,_res_query) __weak_alias(res_search,_res_search) #endif #if PACKETSZ > 1024 #define MAXPACKET PACKETSZ #else #define MAXPACKET 1024 #endif int h_errno; /* * Formulate a normal query, send, and await answer. * Returned answer is placed in supplied buffer "answer". * Perform preliminary check of answer, returning success only * if no error is indicated and the answer count is nonzero. * Return the size of the response on success, -1 on error. * Error number is left in h_errno. * * Caller must parse answer and determine whether it answers the question. */ int res_query(name, class, type, answer, anslen) const char *name; /* domain name */ int class, type; /* class and type of query */ u_char *answer; /* buffer to put answer */ int anslen; /* size of answer buffer */ { u_char buf[MAXPACKET]; HEADER *hp = (HEADER *)(void *)answer; int n; hp->rcode = NOERROR; /* default */ _DIAGASSERT(name != NULL); _DIAGASSERT(answer != NULL); if ((_res.options & RES_INIT) == 0 && res_init() == -1) { h_errno = NETDB_INTERNAL; return (-1); } #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; res_query(%s, %d, %d)\n", name, class, type); #endif n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL, buf, sizeof(buf)); #ifdef RES_USE_EDNS0 if (n > 0 && (_res.options & RES_USE_EDNS0) != 0) n = res_opt(n, buf, sizeof(buf), anslen); #endif if (n <= 0) { #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; res_query: mkquery failed\n"); #endif h_errno = NO_RECOVERY; return (n); } n = res_send(buf, n, answer, anslen); if (n < 0) { #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; res_query: send error\n"); #endif h_errno = TRY_AGAIN; return (n); } if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; rcode = %u, ancount=%u\n", hp->rcode, ntohs(hp->ancount)); #endif switch (hp->rcode) { case NXDOMAIN: h_errno = HOST_NOT_FOUND; break; case SERVFAIL: h_errno = TRY_AGAIN; break; case NOERROR: h_errno = NO_DATA; break; case FORMERR: case NOTIMP: case REFUSED: default: h_errno = NO_RECOVERY; break; } return (-1); } return (n); } /* * Formulate a normal query, send, and retrieve answer in supplied buffer. * Return the size of the response on success, -1 on error. * If enabled, implement search rules until answer or unrecoverable failure * is detected. Error code, if any, is left in h_errno. */ int res_search(name, class, type, answer, anslen) const char *name; /* domain name */ int class, type; /* class and type of query */ u_char *answer; /* buffer to put answer */ int anslen; /* size of answer */ { const char *cp, * const *domain; HEADER *hp = (HEADER *)(void *)answer; u_int dots; int trailing_dot, ret, saved_herrno; int got_nodata = 0, got_servfail = 0, tried_as_is = 0; _DIAGASSERT(name != NULL); _DIAGASSERT(answer != NULL); if ((_res.options & RES_INIT) == 0 && res_init() == -1) { h_errno = NETDB_INTERNAL; return (-1); } errno = 0; h_errno = HOST_NOT_FOUND; /* default, if we never query */ dots = 0; for (cp = name; *cp; cp++) dots += (*cp == '.'); trailing_dot = 0; if (cp > name && *--cp == '.') trailing_dot++; /* * if there aren't any dots, it could be a user-level alias */ if (!dots && (cp = __hostalias(name)) != NULL) return (res_query(cp, class, type, answer, anslen)); /* * If there are dots in the name already, let's just give it a try * 'as is'. The threshold can be set with the "ndots" option. */ saved_herrno = -1; if (dots >= _res.ndots) { ret = res_querydomain(name, NULL, class, type, answer, anslen); if (ret > 0) return (ret); saved_herrno = h_errno; tried_as_is++; } /* * We do at least one level of search if * - there is no dot and RES_DEFNAME is set, or * - there is at least one dot, there is no trailing dot, * and RES_DNSRCH is set. */ if ((!dots && (_res.options & RES_DEFNAMES)) || (dots && !trailing_dot && (_res.options & RES_DNSRCH))) { int done = 0; for (domain = (const char * const *)_res.dnsrch; *domain && !done; domain++) { ret = res_querydomain(name, *domain, class, type, answer, anslen); if (ret > 0) return (ret); /* * If no server present, give up. * If name isn't found in this domain, * keep trying higher domains in the search list * (if that's enabled). * On a NO_DATA error, keep trying, otherwise * a wildcard entry of another type could keep us * from finding this entry higher in the domain. * If we get some other error (negative answer or * server failure), then stop searching up, * but try the input name below in case it's * fully-qualified. */ if (errno == ECONNREFUSED) { h_errno = TRY_AGAIN; return (-1); } switch (h_errno) { case NO_DATA: got_nodata++; /* FALLTHROUGH */ case HOST_NOT_FOUND: /* keep trying */ break; case TRY_AGAIN: if (hp->rcode == SERVFAIL) { /* try next search element, if any */ got_servfail++; break; } /* FALLTHROUGH */ default: /* anything else implies that we're done */ done++; } /* * if we got here for some reason other than DNSRCH, * we only wanted one iteration of the loop, so stop. */ if (!(_res.options & RES_DNSRCH)) done++; } } /* * if we have not already tried the name "as is", do that now. * note that we do this regardless of how many dots were in the * name or whether it ends with a dot. */ if (!tried_as_is) { ret = res_querydomain(name, NULL, class, type, answer, anslen); if (ret > 0) return (ret); } /* * if we got here, we didn't satisfy the search. * if we did an initial full query, return that query's h_errno * (note that we wouldn't be here if that query had succeeded). * else if we ever got a nodata, send that back as the reason. * else send back meaningless h_errno, that being the one from * the last DNSRCH we did. */ if (saved_herrno != -1) h_errno = saved_herrno; else if (got_nodata) h_errno = NO_DATA; else if (got_servfail) h_errno = TRY_AGAIN; return (-1); } /* * Perform a call on res_query on the concatenation of name and domain, * removing a trailing dot from name if domain is NULL. */ int res_querydomain(name, domain, class, type, answer, anslen) const char *name, *domain; int class, type; /* class and type of query */ u_char *answer; /* buffer to put answer */ int anslen; /* size of answer */ { char nbuf[MAXDNAME]; const char *longname = nbuf; size_t n, d; _DIAGASSERT(name != NULL); /* domain may be NULL */ _DIAGASSERT(answer != NULL); if ((_res.options & RES_INIT) == 0 && res_init() == -1) { h_errno = NETDB_INTERNAL; return (-1); } #ifdef DEBUG if (_res.options & RES_DEBUG) printf(";; res_querydomain(%s, %s, %d, %d)\n", name, domain?domain:"", class, type); #endif if (domain == NULL) { /* * Check for trailing '.'; * copy without '.' if present. */ n = strlen(name); if (n + 1 > sizeof(nbuf)) { h_errno = NO_RECOVERY; return (-1); } if (n > 0 && name[--n] == '.') { strncpy(nbuf, name, n); nbuf[n] = '\0'; } else longname = name; } else { n = strlen(name); d = strlen(domain); if (n + 1 + d + 1 > sizeof(nbuf)) { h_errno = NO_RECOVERY; return (-1); } snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain); } return (res_query(longname, class, type, answer, anslen)); } const char * __hostalias(name) const char *name; { char *cp1, *cp2; FILE *fp; char *file; char buf[BUFSIZ]; static char abuf[MAXDNAME]; _DIAGASSERT(name != NULL); if (_res.options & RES_NOALIASES) return (NULL); /* * forbid hostaliases for setuid binary, due to possible security * breach. */ if (issetugid()) return (NULL); file = getenv("HOSTALIASES"); if (file == NULL || (fp = fopen(file, "r")) == NULL) return (NULL); #if 0 /* * if a setuid binary dumps core into a weak-privileged file, malicious * user may try to use $HOSTALIASES to peep content of protected files * kept in *fp. * NetBSD does not dump core for setuid binary, so it is safe to * comment the line out. see sys/kern/kern_sig.c:coredump(). */ setbuf(fp, NULL); #endif buf[sizeof(buf) - 1] = '\0'; while (fgets(buf, sizeof(buf) - 1, fp)) { for (cp1 = buf; *cp1 && !isspace((u_char) *cp1); ++cp1) ; if (!*cp1) break; *cp1 = '\0'; if (!strcasecmp(buf, name)) { while (isspace((u_char) *++cp1)) ; if (!*cp1) break; for (cp2 = cp1 + 1; *cp2 && !isspace((u_char) *cp2); ++cp2) ; *cp2 = '\0'; (void)strlcpy(abuf, cp1, sizeof(abuf)); (void)fclose(fp); return (abuf); } } (void)fclose(fp); return (NULL); }