Removed the DNS caching system because tinyproxy did not determine the TTL
of the host names being resolved, which is not recommended by RFC2616. Basically, if a HTTP client doesn't respect the TTL is should not be caching the address since it leaves itself open to DNS spoofing attacks. Also, having a DNS caching system is an administater decision, and so should not be included in the tinyproxy source.
This commit is contained in:
Robert James Kaes
parent
e0694a8f6e
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bf18ec5adc
147
src/dnscache.c
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src/dnscache.c
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/* $Id: dnscache.c,v 1.18 2001-11-22 00:31:10 rjkaes Exp $
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*
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* This is a caching DNS system. When a host name is needed we look it up here
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* and see if there is already an answer for it. The domains are placed in a
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* hashed linked list. If the name is not here, then we need to look it up and
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* add it to the system. This really speeds up the connection to servers since
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* the DNS name does not need to be looked up each time. It's kind of cool. :)
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*
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* Copyright (C) 1999 Robert James Kaes (rjkaes@flarenet.com)
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* Copyright (C) 2000 Chris Lightfoot (chris@ex-parrot.com)
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2, or (at your option) any
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* later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include "tinyproxy.h"
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#include "dnscache.h"
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#include "log.h"
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#include "ternary.h"
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#include "utils.h"
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/*
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* The mutex is used for locking around accesses to the ternary tree.
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*/
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static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
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#define LOCK() pthread_mutex_lock(&mutex);
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#define UNLOCK() pthread_mutex_unlock(&mutex);
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#define DNSEXPIRE (5 * 60)
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#define DNS_INSERT_LIMIT 10000 /* free the memory after inserts */
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struct dnscache_s {
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struct in_addr ipaddr;
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time_t expire;
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};
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static TERNARY dns_tree = -1;
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static unsigned int dns_insertions;
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static int
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dns_lookup(struct in_addr *addr, char *domain)
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{
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int ret;
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struct dnscache_s *ptr;
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assert(addr != NULL);
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assert(domain != NULL);
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ret = ternary_search(dns_tree, domain, (void *) &ptr);
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if (TE_ISERROR(ret)
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|| difftime(time(NULL), ptr->expire) > DNSEXPIRE) {
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return -1;
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}
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memcpy(addr, &ptr->ipaddr, sizeof(struct in_addr));
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return 0;
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}
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static int
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dns_insert(struct in_addr *addr, char *domain)
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{
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struct dnscache_s *newptr;
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assert(addr != NULL);
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assert(domain != NULL);
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if (!(newptr = safemalloc(sizeof(struct dnscache_s)))) {
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return -1;
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}
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memcpy(&newptr->ipaddr, addr, sizeof(struct in_addr));
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newptr->expire = time(NULL);
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DEBUG2("Inserting [%s] into DNS cache", domain);
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if (TE_ISERROR(ternary_replace(dns_tree, domain, newptr))) {
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safefree(newptr);
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return -1;
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}
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DEBUG2("Finished inserting [%s] into DNS cache", domain);
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return 0;
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}
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int
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dnscache(struct in_addr *addr, char *domain)
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{
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struct hostent *resolv;
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assert(addr != NULL);
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assert(domain != NULL);
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LOCK();
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/* If the DNS tree doesn't exist, build a new one */
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if (dns_tree < 0) {
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dns_tree = ternary_new();
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dns_insertions = 0;
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}
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if (inet_aton(domain, (struct in_addr *) addr) != 0) {
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UNLOCK();
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return 0;
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}
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/* Well, we're not dotted-decimal so we need to look it up */
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if (dns_lookup(addr, domain) == 0) {
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UNLOCK();
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return 0;
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}
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/* Okay, so not in the list... need to actually look it up. */
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if (!(resolv = gethostbyname(domain))) {
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UNLOCK();
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return -1;
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}
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memcpy(addr, resolv->h_addr_list[0], resolv->h_length);
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dns_insert(addr, domain);
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dns_insertions++;
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if (dns_insertions > DNS_INSERT_LIMIT) {
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log_message(LOG_INFO,
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"DNS Insertion limit reached (%u). Rebuilding cache.",
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dns_insertions);
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ternary_destroy(dns_tree, free);
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dns_tree = ternary_new();
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dns_insertions = 0;
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}
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UNLOCK();
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return 0;
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}
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@ -1,25 +0,0 @@
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/* $Id: dnscache.h,v 1.7 2001-10-25 17:02:50 rjkaes Exp $
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*
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* See 'dnscache.c' for a detailed description.
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*
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* Copyright (C) 1999 Robert James Kaes (rjkaes@flarenet.com)
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2, or (at your option) any
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* later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#ifndef _TINYPROXY_DNSCACHE_H_
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#define _TINYPROXY_DNSCACHE_H_
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#include "tinyproxy.h"
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extern int dnscache(struct in_addr *addr, char *domain);
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#endif
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