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Diffstat (limited to 'runtime/dnscache.c')
| -rw-r--r-- | runtime/dnscache.c | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/runtime/dnscache.c b/runtime/dnscache.c new file mode 100644 index 00000000..32d6e425 --- /dev/null +++ b/runtime/dnscache.c @@ -0,0 +1,355 @@ +/* dnscache.c + * Implementation of a real DNS cache + * + * File begun on 2011-06-06 by RGerhards + * The initial implementation is far from being optimal. The idea is to + * first get somethting that'S functionally OK, and then evolve the algorithm. + * In any case, even the initial implementaton is far faster than what we had + * before. -- rgerhards, 2011-06-06 + * + * Copyright 2011 by Rainer Gerhards and Adiscon GmbH. + * + * This file is part of the rsyslog runtime library. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * -or- + * see COPYING.ASL20 in the source distribution + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +#include "config.h" + +#include "rsyslog.h" +#include <stdio.h> +#include <stdlib.h> +#include <signal.h> +#include <netdb.h> +#include <unistd.h> + +#include "syslogd-types.h" +#include "glbl.h" +#include "errmsg.h" +#include "obj.h" +#include "unicode-helper.h" +#include "net.h" + +/* in this initial implementation, we use a simple, non-optimized at all + * linear list. + */ +/* module data structures */ +struct dnscache_entry_s { + struct sockaddr_storage addr; + uchar *pszHostFQDN; + uchar *ip; + struct dnscache_entry_s *next; + unsigned nUsed; +}; +typedef struct dnscache_entry_s dnscache_entry_t; +struct dnscache_s { + pthread_rwlock_t rwlock; + dnscache_entry_t *root; + unsigned nEntries; +}; +typedef struct dnscache_s dnscache_t; +#define MAX_CACHE_ENTRIES 1000 + + +/* static data */ +DEFobjStaticHelpers +DEFobjCurrIf(glbl) +DEFobjCurrIf(errmsg) +static dnscache_t dnsCache; + + +/* init function (must be called once) */ +rsRetVal +dnscacheInit(void) +{ + DEFiRet; + dnsCache.root = NULL; + dnsCache.nEntries = 0; + pthread_rwlock_init(&dnsCache.rwlock, NULL); + CHKiRet(objGetObjInterface(&obj)); /* this provides the root pointer for all other queries */ + CHKiRet(objUse(glbl, CORE_COMPONENT)); + CHKiRet(objUse(errmsg, CORE_COMPONENT)); +finalize_it: + RETiRet; +} + +/* deinit function (must be called once) */ +rsRetVal +dnscacheDeinit(void) +{ + DEFiRet; + //TODO: free cache elements dnsCache.root = NULL; + pthread_rwlock_destroy(&dnsCache.rwlock); + objRelease(glbl, CORE_COMPONENT); + objRelease(errmsg, CORE_COMPONENT); + RETiRet; +} + + +/* destruct a cache entry. + * Precondition: entry must already be unlinked from list + */ +static inline void +entryDestruct(dnscache_entry_t *etry) +{ + free(etry->pszHostFQDN); + free(etry->ip); + free(etry); +} + + +static inline dnscache_entry_t* +findEntry(struct sockaddr_storage *addr) +{ + dnscache_entry_t *etry; + for(etry = dnsCache.root ; etry != NULL ; etry = etry->next) { + if(SALEN((struct sockaddr*)addr) == SALEN((struct sockaddr*) &etry->addr) + && !memcmp(addr, &etry->addr, SALEN((struct sockaddr*) addr))) + break; /* in this case, we found our entry */ + } + if(etry != NULL) + ++etry->nUsed; /* this is *not* atomic, but we can live with an occasional loss! */ + return etry; +} + + +/* This is a cancel-safe getnameinfo() version, because we learned + * (via drd/valgrind) that getnameinfo() seems to have some issues + * when being cancelled, at least if the module was dlloaded. + * rgerhards, 2008-09-30 + */ +static inline int +mygetnameinfo(const struct sockaddr *sa, socklen_t salen, + char *host, size_t hostlen, + char *serv, size_t servlen, int flags) +{ + int iCancelStateSave; + int i; + + pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &iCancelStateSave); + i = getnameinfo(sa, salen, host, hostlen, serv, servlen, flags); + pthread_setcancelstate(iCancelStateSave, NULL); + return i; +} + + +/* resolve an address. + * + * Please see http://www.hmug.org/man/3/getnameinfo.php (under Caveats) + * for some explanation of the code found below. We do by default not + * discard message where we detected malicouos DNS PTR records. However, + * there is a user-configurabel option that will tell us if + * we should abort. For this, the return value tells the caller if the + * message should be processed (1) or discarded (0). + */ +static rsRetVal +resolveAddr(struct sockaddr_storage *addr, uchar *pszHostFQDN, uchar *ip) +{ + DEFiRet; + int error; + sigset_t omask, nmask; + struct addrinfo hints, *res; + + assert(addr != NULL); + assert(pszHostFQDN != NULL); + + error = mygetnameinfo((struct sockaddr *)addr, SALEN((struct sockaddr *)addr), + (char*) ip, NI_MAXHOST, NULL, 0, NI_NUMERICHOST); + if(error) { + dbgprintf("Malformed from address %s\n", gai_strerror(error)); + ABORT_FINALIZE(RS_RET_INVALID_SOURCE); + } + + if(!glbl.GetDisableDNS()) { + sigemptyset(&nmask); + sigaddset(&nmask, SIGHUP); + pthread_sigmask(SIG_BLOCK, &nmask, &omask); + + error = mygetnameinfo((struct sockaddr *)addr, SALEN((struct sockaddr *) addr), + (char*)pszHostFQDN, NI_MAXHOST, NULL, 0, NI_NAMEREQD); + +dbgprintf("dnscache: error %d after 2nd mygetnameinfo\n", error); + if(error == 0) { + memset (&hints, 0, sizeof (struct addrinfo)); + hints.ai_flags = AI_NUMERICHOST; + + /* we now do a lookup once again. This one should fail, + * because we should not have obtained a non-numeric address. If + * we got a numeric one, someone messed with DNS! + */ + if(getaddrinfo ((char*)pszHostFQDN, NULL, &hints, &res) == 0) { + uchar szErrMsg[1024]; + freeaddrinfo (res); + /* OK, we know we have evil. The question now is what to do about + * it. One the one hand, the message might probably be intended + * to harm us. On the other hand, losing the message may also harm us. + * Thus, the behaviour is controlled by the $DropMsgsWithMaliciousDnsPTRRecords + * option. If it tells us we should discard, we do so, else we proceed, + * but log an error message together with it. + * time being, we simply drop the name we obtained and use the IP - that one + * is OK in any way. We do also log the error message. rgerhards, 2007-07-16 + */ + if(glbl.GetDropMalPTRMsgs() == 1) { + snprintf((char*)szErrMsg, sizeof(szErrMsg) / sizeof(uchar), + "Malicious PTR record, message dropped " + "IP = \"%s\" HOST = \"%s\"", + ip, pszHostFQDN); + errmsg.LogError(0, RS_RET_MALICIOUS_ENTITY, "%s", szErrMsg); + pthread_sigmask(SIG_SETMASK, &omask, NULL); + ABORT_FINALIZE(RS_RET_MALICIOUS_ENTITY); + } + + /* Please note: we deal with a malicous entry. Thus, we have crafted + * the snprintf() below so that all text is in front of the entry - maybe + * it contains characters that make the message unreadable + * (OK, I admit this is more or less impossible, but I am paranoid...) + * rgerhards, 2007-07-16 + */ + snprintf((char*)szErrMsg, sizeof(szErrMsg) / sizeof(uchar), + "Malicious PTR record (message accepted, but used IP " + "instead of PTR name: IP = \"%s\" HOST = \"%s\"", + ip, pszHostFQDN); + errmsg.LogError(0, NO_ERRCODE, "%s", szErrMsg); + + error = 1; /* that will trigger using IP address below. */ + } + } + pthread_sigmask(SIG_SETMASK, &omask, NULL); + } + +dbgprintf("dnscache: error %d, DisableDNS %d\n", error, glbl.GetDisableDNS()); + if(error || glbl.GetDisableDNS()) { + dbgprintf("Host name for your address (%s) unknown\n", ip); + strcpy((char*) pszHostFQDN, (char*)ip); + } + +finalize_it: + RETiRet; +} + + +/* evict an entry from the cache. We should try to evict one that does + * not decrease the hit rate that much, but we do not try to hard currently + * (as the base cache data structure may change). + * This MUST NOT be called when the cache is empty! + * rgerhards, 2011-06-06 + */ +static inline void +evictEntry(void) +{ + dnscache_entry_t *prev, *evict, *prevEvict, *etry; + unsigned lowest; + + prev = prevEvict = NULL; + evict = dnsCache.root; + lowest = evict->nUsed; + for(etry = dnsCache.root->next ; etry != NULL ; etry = etry->next) { + if(etry->nUsed < lowest) { + evict = etry; + lowest = etry->nUsed; + prevEvict = prev; + } + prev = etry; + } + + /* found lowest, unlink */ + if(prevEvict == NULL) { /* remove root? */ + dnsCache.root = evict->next; + } else { + prevEvict = evict->next; + } + entryDestruct(evict); +} + + +/* add a new entry to the cache. This means the address is resolved and + * then added to the cache. + */ +static inline rsRetVal +addEntry(struct sockaddr_storage *addr, dnscache_entry_t **pEtry) +{ + uchar pszHostFQDN[NI_MAXHOST]; + uchar ip[80]; /* 80 is safe for larges IPv6 addr */ + dnscache_entry_t *etry; + DEFiRet; + CHKiRet(resolveAddr(addr, pszHostFQDN, ip)); + CHKmalloc(etry = MALLOC(sizeof(dnscache_entry_t))); + CHKmalloc(etry->pszHostFQDN = ustrdup(pszHostFQDN)); + CHKmalloc(etry->ip = ustrdup(ip)); + memcpy(&etry->addr, addr, SALEN((struct sockaddr*) addr)); + etry->nUsed = 0; + *pEtry = etry; + + /* add to list. Currently, we place the new element always at + * the root node. This needs to be optimized later. 2011-06-06 + */ + pthread_rwlock_unlock(&dnsCache.rwlock); /* release read lock */ + pthread_rwlock_wrlock(&dnsCache.rwlock); /* and re-aquire for writing */ + if(dnsCache.nEntries >= MAX_CACHE_ENTRIES) { + evictEntry(); + } + etry->next = dnsCache.root; + dnsCache.root = etry; + pthread_rwlock_unlock(&dnsCache.rwlock); + pthread_rwlock_rdlock(&dnsCache.rwlock); /* TODO: optimize this! */ + +finalize_it: + RETiRet; +} + + +/* validate if an entry is still valid and, if not, re-query it. + * In the initial implementation, this is a dummy! + * TODO: implement! + */ +static inline rsRetVal +validateEntry(dnscache_entry_t *etry, struct sockaddr_storage *addr) +{ + return RS_RET_OK; +} + + +/* This is the main function: it looks up an entry and returns it's name + * and IP address. If the entry is not yet inside the cache, it is added. + * If the entry can not be resolved, an error is reported back. + */ +rsRetVal +dnscacheLookup(struct sockaddr_storage *addr, uchar *pszHostFQDN, uchar *ip) +{ + dnscache_entry_t *etry; + DEFiRet; + + pthread_rwlock_rdlock(&dnsCache.rwlock); /* TODO: optimize this! */ + etry = findEntry(addr); + dbgprintf("dnscache: entry %p found\n", etry); + if(etry == NULL) { + CHKiRet(addEntry(addr, &etry)); + } else { + CHKiRet(validateEntry(etry, addr)); + } + // TODO/QUESTION: can we get rid of the strcpy? +dbgprintf("XXXX: hostn '%s', ip '%s'\n", etry->pszHostFQDN, etry->ip); + strcpy((char*)pszHostFQDN, (char*)etry->pszHostFQDN); + strcpy((char*)ip, (char*)etry->ip); + +finalize_it: + pthread_rwlock_unlock(&dnsCache.rwlock); +dbgprintf("XXXX: dnscacheLookup finished, iRet=%d\n", iRet); + if(iRet != RS_RET_OK && iRet != RS_RET_ADDRESS_UNKNOWN) { + DBGPRINTF("dnscacheLookup failed with iRet %d\n", iRet); + strcpy((char*) pszHostFQDN, "???"); + strcpy((char*) ip, "???"); + } + RETiRet; +} |