/*
* iterator/iter_scrub.c - scrubbing, normalization, sanitization of DNS msgs.
*
* Copyright (c) 2007, NLnet Labs. All rights reserved.
*
* This software is open source.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 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.
*
* Neither the name of the NLNET LABS 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 COPYRIGHT HOLDERS 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 COPYRIGHT
* HOLDER 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.
*/
/**
* \file
*
* This file has routine(s) for cleaning up incoming DNS messages from
* possible useless or malicious junk in it.
*/
#include "config.h"
#include "iterator/iter_scrub.h"
#include "iterator/iterator.h"
#include "iterator/iter_priv.h"
#include "services/cache/rrset.h"
#include "util/log.h"
#include "util/net_help.h"
#include "util/regional.h"
#include "util/config_file.h"
#include "util/module.h"
#include "util/data/msgparse.h"
#include "util/data/dname.h"
#include "util/data/msgreply.h"
#include "util/alloc.h"
#include "sldns/sbuffer.h"
/** RRset flag used during scrubbing. The RRset is OK. */
#define RRSET_SCRUB_OK 0x80
/** remove rrset, update loop variables */
static void
remove_rrset(const char* str, sldns_buffer* pkt, struct msg_parse* msg,
struct rrset_parse* prev, struct rrset_parse** rrset)
{
if(verbosity >= VERB_QUERY && str
&& (*rrset)->dname_len <= LDNS_MAX_DOMAINLEN) {
uint8_t buf[LDNS_MAX_DOMAINLEN+1];
dname_pkt_copy(pkt, buf, (*rrset)->dname);
log_nametypeclass(VERB_QUERY, str, buf,
(*rrset)->type, ntohs((*rrset)->rrset_class));
}
if(prev)
prev->rrset_all_next = (*rrset)->rrset_all_next;
else msg->rrset_first = (*rrset)->rrset_all_next;
if(msg->rrset_last == *rrset)
msg->rrset_last = prev;
msg->rrset_count --;
switch((*rrset)->section) {
case LDNS_SECTION_ANSWER: msg->an_rrsets--; break;
case LDNS_SECTION_AUTHORITY: msg->ns_rrsets--; break;
case LDNS_SECTION_ADDITIONAL: msg->ar_rrsets--; break;
default: log_assert(0);
}
msgparse_bucket_remove(msg, *rrset);
*rrset = (*rrset)->rrset_all_next;
}
/** return true if rr type has additional names in it */
static int
has_additional(uint16_t t)
{
switch(t) {
case LDNS_RR_TYPE_MB:
case LDNS_RR_TYPE_MD:
case LDNS_RR_TYPE_MF:
case LDNS_RR_TYPE_NS:
case LDNS_RR_TYPE_MX:
case LDNS_RR_TYPE_KX:
case LDNS_RR_TYPE_SRV:
return 1;
case LDNS_RR_TYPE_NAPTR:
/* TODO: NAPTR not supported, glue stripped off */
return 0;
}
return 0;
}
/** get additional name from rrset RR, return false if no name present */
static int
get_additional_name(struct rrset_parse* rrset, struct rr_parse* rr,
uint8_t** nm, size_t* nmlen, sldns_buffer* pkt)
{
size_t offset = 0;
size_t len, oldpos;
switch(rrset->type) {
case LDNS_RR_TYPE_MB:
case LDNS_RR_TYPE_MD:
case LDNS_RR_TYPE_MF:
case LDNS_RR_TYPE_NS:
offset = 0;
break;
case LDNS_RR_TYPE_MX:
case LDNS_RR_TYPE_KX:
offset = 2;
break;
case LDNS_RR_TYPE_SRV:
offset = 6;
break;
case LDNS_RR_TYPE_NAPTR:
/* TODO: NAPTR not supported, glue stripped off */
return 0;
default:
return 0;
}
len = sldns_read_uint16(rr->ttl_data+sizeof(uint32_t));
if(len < offset+1)
return 0; /* rdata field too small */
*nm = rr->ttl_data+sizeof(uint32_t)+sizeof(uint16_t)+offset;
oldpos = sldns_buffer_position(pkt);
sldns_buffer_set_position(pkt, (size_t)(*nm - sldns_buffer_begin(pkt)));
*nmlen = pkt_dname_len(pkt);
sldns_buffer_set_position(pkt, oldpos);
if(*nmlen == 0)
return 0;
return 1;
}
/** Place mark on rrsets in additional section they are OK */
static void
mark_additional_rrset(sldns_buffer* pkt, struct msg_parse* msg,
struct rrset_parse* rrset)
{
/* Mark A and AAAA for NS as appropriate additional section info. */
uint8_t* nm = NULL;
size_t nmlen = 0;
struct rr_parse* rr;
if(!has_additional(rrset->type))
return;
for(rr = rrset->rr_first; rr; rr = rr->next) {
if(get_additional_name(rrset, rr, &nm, &nmlen, pkt)) {
/* mark A */
hashvalue_t h = pkt_hash_rrset(pkt, nm, LDNS_RR_TYPE_A,
rrset->rrset_class, 0);
struct rrset_parse* r = msgparse_hashtable_lookup(
msg, pkt, h, 0, nm, nmlen,
LDNS_RR_TYPE_A, rrset->rrset_class);
if(r && r->section == LDNS_SECTION_ADDITIONAL) {
r->flags |= RRSET_SCRUB_OK;
}
/* mark AAAA */
h = pkt_hash_rrset(pkt, nm, LDNS_RR_TYPE_AAAA,
rrset->rrset_class, 0);
r = msgparse_hashtable_lookup(msg, pkt, h, 0, nm,
nmlen, LDNS_RR_TYPE_AAAA, rrset->rrset_class);
if(r && r->section == LDNS_SECTION_ADDITIONAL) {
r->flags |= RRSET_SCRUB_OK;
}
}
}
}
/** Get target name of a CNAME */
static int
parse_get_cname_target(struct rrset_parse* rrset, uint8_t** sname,
size_t* snamelen)
{
if(rrset->rr_count != 1) {
struct rr_parse* sig;
verbose(VERB_ALGO, "Found CNAME rrset with "
"size > 1: %u", (unsigned)rrset->rr_count);
/* use the first CNAME! */
rrset->rr_count = 1;
rrset->size = rrset->rr_first->size;
for(sig=rrset->rrsig_first; sig; sig=sig->next)
rrset->size += sig->size;
rrset->rr_last = rrset->rr_first;
rrset->rr_first->next = NULL;
}
if(rrset->rr_first->size < sizeof(uint16_t)+1)
return 0; /* CNAME rdata too small */
*sname = rrset->rr_first->ttl_data + sizeof(uint32_t)
+ sizeof(uint16_t); /* skip ttl, rdatalen */
*snamelen = rrset->rr_first->size - sizeof(uint16_t);
return 1;
}
/** Synthesize CNAME from DNAME, false if too long */
static int
synth_cname(uint8_t* qname, size_t qnamelen, struct rrset_parse* dname_rrset,
uint8_t* alias, size_t* aliaslen, sldns_buffer* pkt)
{
/* we already know that sname is a strict subdomain of DNAME owner */
uint8_t* dtarg = NULL;
size_t dtarglen;
if(!parse_get_cname_target(dname_rrset, &dtarg, &dtarglen))
return 0;
log_assert(qnamelen > dname_rrset->dname_len);
/* DNAME from com. to net. with qname example.com. -> example.net. */
/* so: \3com\0 to \3net\0 and qname \7example\3com\0 */
*aliaslen = qnamelen + dtarglen - dname_rrset->dname_len;
if(*aliaslen > LDNS_MAX_DOMAINLEN)
return 0; /* should have been RCODE YXDOMAIN */
/* decompress dnames into buffer, we know it fits */
dname_pkt_copy(pkt, alias, qname);
dname_pkt_copy(pkt, alias+(qnamelen-dname_rrset->dname_len), dtarg);
return 1;
}
/** synthesize a CNAME rrset */
static struct rrset_parse*
synth_cname_rrset(uint8_t** sname, size_t* snamelen, uint8_t* alias,
size_t aliaslen, struct regional* region, struct msg_parse* msg,
struct rrset_parse* rrset, struct rrset_parse* prev,
struct rrset_parse* nx, sldns_buffer* pkt)
{
struct rrset_parse* cn = (struct rrset_parse*)regional_alloc(region,
sizeof(struct rrset_parse));
if(!cn)
return NULL;
memset(cn, 0, sizeof(*cn));
cn->rr_first = (struct rr_parse*)regional_alloc(region,
sizeof(struct rr_parse));
if(!cn->rr_first)
return NULL;
cn->rr_last = cn->rr_first;
/* CNAME from sname to alias */
cn->dname = (uint8_t*)regional_alloc(region, *snamelen);
if(!cn->dname)
return NULL;
dname_pkt_copy(pkt, cn->dname, *sname);
cn->dname_len = *snamelen;
cn->type = LDNS_RR_TYPE_CNAME;
cn->section = rrset->section;
cn->rrset_class = rrset->rrset_class;
cn->rr_count = 1;
cn->size = sizeof(uint16_t) + aliaslen;
cn->hash=pkt_hash_rrset(pkt, cn->dname, cn->type, cn->rrset_class, 0);
/* allocate TTL + rdatalen + uncompressed dname */
memset(cn->rr_first, 0, sizeof(struct rr_parse));
cn->rr_first->outside_packet = 1;
cn->rr_first->ttl_data = (uint8_t*)regional_alloc(region,
sizeof(uint32_t)+sizeof(uint16_t)+aliaslen);
if(!cn->rr_first->ttl_data)
return NULL;
sldns_write_uint32(cn->rr_first->ttl_data, 0); /* TTL = 0 */
sldns_write_uint16(cn->rr_first->ttl_data+4, aliaslen);
memmove(cn->rr_first->ttl_data+6, alias, aliaslen);
cn->rr_first->size = sizeof(uint16_t)+aliaslen;
/* link it in */
cn->rrset_all_next = nx;
if(prev)
prev->rrset_all_next = cn;
else msg->rrset_first = cn;
if(nx == NULL)
msg->rrset_last = cn;
msg->rrset_count ++;
msg->an_rrsets++;
/* it is not inserted in the msg hashtable. */
*sname = cn->rr_first->ttl_data + sizeof(uint32_t)+sizeof(uint16_t);
*snamelen = aliaslen;
return cn;
}
/** check if DNAME applies to a name */
static int
pkt_strict_sub(sldns_buffer* pkt, uint8_t* sname, uint8_t* dr)
{
uint8_t buf1[LDNS_MAX_DOMAINLEN+1];
uint8_t buf2[LDNS_MAX_DOMAINLEN+1];
/* decompress names */
dname_pkt_copy(pkt, buf1, sname);
dname_pkt_copy(pkt, buf2, dr);
return dname_strict_subdomain_c(buf1, buf2);
}
/** check subdomain with decompression */
static int
pkt_sub(sldns_buffer* pkt, uint8_t* comprname, uint8_t* zone)
{
uint8_t buf[LDNS_MAX_DOMAINLEN+1];
dname_pkt_copy(pkt, buf, comprname);
return dname_subdomain_c(buf, zone);
}
/** check subdomain with decompression, compressed is parent */
static int
sub_of_pkt(sldns_buffer* pkt, uint8_t* zone, uint8_t* comprname)
{
uint8_t buf[LDNS_MAX_DOMAINLEN+1];
dname_pkt_copy(pkt, buf, comprname);
return dname_subdomain_c(zone, buf);
}
/**
* This routine normalizes a response. This includes removing "irrelevant"
* records from the answer and additional sections and (re)synthesizing
* CNAMEs from DNAMEs, if present.
*
* @param pkt: packet.
* @param msg: msg to normalize.
* @param qinfo: original query.
* @param region: where to allocate synthesized CNAMEs.
* @return 0 on error.
*/
static int
scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg,
struct query_info* qinfo, struct regional* region)
{
uint8_t* sname = qinfo->qname;
size_t snamelen = qinfo->qname_len;
struct rrset_parse* rrset, *prev, *nsset=NULL;
if(FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NOERROR &&
FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NXDOMAIN)
return 1;
/* For the ANSWER section, remove all "irrelevant" records and add
* synthesized CNAMEs from DNAMEs
* This will strip out-of-order CNAMEs as well. */
/* walk through the parse packet rrset list, keep track of previous
* for insert and delete ease, and examine every RRset */
prev = NULL;
rrset = msg->rrset_first;
while(rrset && rrset->section == LDNS_SECTION_ANSWER) {
if(rrset->type == LDNS_RR_TYPE_DNAME &&
pkt_strict_sub(pkt, sname, rrset->dname)) {
/* check if next rrset is correct CNAME. else,
* synthesize a CNAME */
struct rrset_parse* nx = rrset->rrset_all_next;
uint8_t alias[LDNS_MAX_DOMAINLEN+1];
size_t aliaslen = 0;
if(rrset->rr_count != 1) {
verbose(VERB_ALGO, "Found DNAME rrset with "
"size > 1: %u",
(unsigned)rrset->rr_count);
return 0;
}
if(!synth_cname(sname, snamelen, rrset, alias,
&aliaslen, pkt)) {
verbose(VERB_ALGO, "synthesized CNAME "
"too long");
return 0;
}
if(nx && nx->type == LDNS_RR_TYPE_CNAME &&
dname_pkt_compare(pkt, sname, nx->dname) == 0) {
/* check next cname */
uint8_t* t = NULL;
size_t tlen = 0;
if(!parse_get_cname_target(nx, &t, &tlen))
return 0;
if(dname_pkt_compare(pkt, alias, t) == 0) {
/* it's OK and better capitalized */
prev = rrset;
rrset = nx;
continue;
}
/* synth ourselves */
}
/* synth a CNAME rrset */
prev = synth_cname_rrset(&sname, &snamelen, alias,
aliaslen, region, msg, rrset, rrset, nx, pkt);
if(!prev) {
log_err("out of memory synthesizing CNAME");
return 0;
}
/* FIXME: resolve the conflict between synthesized
* CNAME ttls and the cache. */
rrset = nx;
continue;
}
/* The only records in the ANSWER section not allowed to */
if(dname_pkt_compare(pkt, sname, rrset->dname) != 0) {
remove_rrset("normalize: removing irrelevant RRset:",
pkt, msg, prev, &rrset);
continue;
}
/* Follow the CNAME chain. */
if(rrset->type == LDNS_RR_TYPE_CNAME) {
struct rrset_parse* nx = rrset->rrset_all_next;
uint8_t* oldsname = sname;
/* see if the next one is a DNAME, if so, swap them */
if(nx && nx->section == LDNS_SECTION_ANSWER &&
nx->type == LDNS_RR_TYPE_DNAME &&
nx->rr_count == 1 &&
pkt_strict_sub(pkt, sname, nx->dname)) {
/* there is a DNAME after this CNAME, it
* is in the ANSWER section, and the DNAME
* applies to the name we cover */
/* check if the alias of the DNAME equals
* this CNAME */
uint8_t alias[LDNS_MAX_DOMAINLEN+1];
size_t aliaslen = 0;
uint8_t* t = NULL;
size_t tlen = 0;
if(synth_cname(sname, snamelen, nx, alias,
&aliaslen, pkt) &&
parse_get_cname_target(rrset, &t, &tlen) &&
dname_pkt_compare(pkt, alias, t) == 0) {
/* the synthesized CNAME equals the
* current CNAME. This CNAME is the
* one that the DNAME creates, and this
* CNAME is better capitalised */
verbose(VERB_ALGO, "normalize: re-order of DNAME and its CNAME");
if(prev) prev->rrset_all_next = nx;
else msg->rrset_first = nx;
if(nx->rrset_all_next == NULL)
msg->rrset_last = rrset;
rrset->rrset_all_next =
nx->rrset_all_next;
nx->rrset_all_next = rrset;
prev = nx;
}
}
/* move to next name in CNAME chain */
if(!parse_get_cname_target(rrset, &sname, &snamelen))
return 0;
prev = rrset;
rrset = rrset->rrset_all_next;
/* in CNAME ANY response, can have data after CNAME */
if(qinfo->qtype == LDNS_RR_TYPE_ANY) {
while(rrset && rrset->section ==
LDNS_SECTION_ANSWER &&
dname_pkt_compare(pkt, oldsname,
rrset->dname) == 0) {
prev = rrset;
rrset = rrset->rrset_all_next;
}
}
continue;
}
/* Otherwise, make sure that the RRset matches the qtype. */
if(qinfo->qtype != LDNS_RR_TYPE_ANY &&
qinfo->qtype != rrset->type) {
remove_rrset("normalize: removing irrelevant RRset:",
pkt, msg, prev, &rrset);
continue;
}
/* Mark the additional names from relevant rrset as OK. */
/* only for RRsets that match the query name, other ones
* will be removed by sanitize, so no additional for them */
if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) == 0)
mark_additional_rrset(pkt, msg, rrset);
prev = rrset;
rrset = rrset->rrset_all_next;
}
/* Mark additional names from AUTHORITY */
while(rrset && rrset->section == LDNS_SECTION_AUTHORITY) {
if(rrset->type==LDNS_RR_TYPE_DNAME ||
rrset->type==LDNS_RR_TYPE_CNAME ||
rrset->type==LDNS_RR_TYPE_A ||
rrset->type==LDNS_RR_TYPE_AAAA) {
remove_rrset("normalize: removing irrelevant "
"RRset:", pkt, msg, prev, &rrset);
continue;
}
/* only one NS set allowed in authority section */
if(rrset->type==LDNS_RR_TYPE_NS) {
/* NS set must be pertinent to the query */
if(!sub_of_pkt(pkt, qinfo->qname, rrset->dname)) {
remove_rrset("normalize: removing irrelevant "
"RRset:", pkt, msg, prev, &rrset);
continue;
}
if(nsset == NULL) {
nsset = rrset;
} else {
remove_rrset("normalize: removing irrelevant "
"RRset:", pkt, msg, prev, &rrset);
continue;
}
}
mark_additional_rrset(pkt, msg, rrset);
prev = rrset;
rrset = rrset->rrset_all_next;
}
/* For each record in the additional section, remove it if it is an
* address record and not in the collection of additional names
* found in ANSWER and AUTHORITY. */
/* These records have not been marked OK previously */
while(rrset && rrset->section == LDNS_SECTION_ADDITIONAL) {
/* FIXME: what about other types? */
if(rrset->type==LDNS_RR_TYPE_A ||
rrset->type==LDNS_RR_TYPE_AAAA)
{
if((rrset->flags & RRSET_SCRUB_OK)) {
/* remove flag to clean up flags variable */
rrset->flags &= ~RRSET_SCRUB_OK;
} else {
remove_rrset("normalize: removing irrelevant "
"RRset:", pkt, msg, prev, &rrset);
continue;
}
}
if(rrset->type==LDNS_RR_TYPE_DNAME ||
rrset->type==LDNS_RR_TYPE_CNAME ||
rrset->type==LDNS_RR_TYPE_NS) {
remove_rrset("normalize: removing irrelevant "
"RRset:", pkt, msg, prev, &rrset);
continue;
}
prev = rrset;
rrset = rrset->rrset_all_next;
}
return 1;
}
/**
* Store potential poison in the cache (only if hardening disabled).
* The rrset is stored in the cache but removed from the message.
* So that it will be used for infrastructure purposes, but not be
* returned to the client.
* @param pkt: packet
* @param msg: message parsed
* @param env: environment with cache
* @param rrset: to store.
*/
static void
store_rrset(sldns_buffer* pkt, struct msg_parse* msg, struct module_env* env,
struct rrset_parse* rrset)
{
struct ub_packed_rrset_key* k;
struct packed_rrset_data* d;
struct rrset_ref ref;
time_t now = *env->now;
k = alloc_special_obtain(env->alloc);
if(!k)
return;
k->entry.data = NULL;
if(!parse_copy_decompress_rrset(pkt, msg, rrset, NULL, k)) {
alloc_special_release(env->alloc, k);
return;
}
d = (struct packed_rrset_data*)k->entry.data;
packed_rrset_ttl_add(d, now);
ref.key = k;
ref.id = k->id;
/*ignore ret: it was in the cache, ref updated */
(void)rrset_cache_update(env->rrset_cache, &ref, env->alloc, now);
}
/** Check if there are SOA records in the authority section (negative) */
static int
soa_in_auth(struct msg_parse* msg)
{
struct rrset_parse* rrset;
for(rrset = msg->rrset_first; rrset; rrset = rrset->rrset_all_next)
if(rrset->type == LDNS_RR_TYPE_SOA &&
rrset->section == LDNS_SECTION_AUTHORITY)
return 1;
return 0;
}
/**
* Check if right hand name in NSEC is within zone
* @param rrset: the NSEC rrset
* @param zonename: the zone name.
* @return true if BAD.
*/
static int sanitize_nsec_is_overreach(struct rrset_parse* rrset,
uint8_t* zonename)
{
struct rr_parse* rr;
uint8_t* rhs;
size_t len;
log_assert(rrset->type == LDNS_RR_TYPE_NSEC);
for(rr = rrset->rr_first; rr; rr = rr->next) {
rhs = rr->ttl_data+4+2;
len = sldns_read_uint16(rr->ttl_data+4);
if(!dname_valid(rhs, len)) {
/* malformed domain name in rdata */
return 1;
}
if(!dname_subdomain_c(rhs, zonename)) {
/* overreaching */
return 1;
}
}
/* all NSEC RRs OK */
return 0;
}
/**
* Given a response event, remove suspect RRsets from the response.
* "Suspect" rrsets are potentially poison. Note that this routine expects
* the response to be in a "normalized" state -- that is, all "irrelevant"
* RRsets have already been removed, CNAMEs are in order, etc.
*
* @param pkt: packet.
* @param msg: msg to normalize.
* @param qinfo: the question originally asked.
* @param zonename: name of server zone.
* @param env: module environment with config and cache.
* @param ie: iterator environment with private address data.
* @return 0 on error.
*/
static int
scrub_sanitize(sldns_buffer* pkt, struct msg_parse* msg,
struct query_info* qinfo, uint8_t* zonename, struct module_env* env,
struct iter_env* ie)
{
int del_addi = 0; /* if additional-holding rrsets are deleted, we
do not trust the normalized additional-A-AAAA any more */
struct rrset_parse* rrset, *prev;
prev = NULL;
rrset = msg->rrset_first;
/* the first DNAME is allowed to stay. It needs checking before
* it can be used from the cache. After normalization, an initial
* DNAME will have a correctly synthesized CNAME after it. */
if(rrset && rrset->type == LDNS_RR_TYPE_DNAME &&
rrset->section == LDNS_SECTION_ANSWER &&
pkt_strict_sub(pkt, qinfo->qname, rrset->dname) &&
pkt_sub(pkt, rrset->dname, zonename)) {
prev = rrset; /* DNAME allowed to stay in answer section */
rrset = rrset->rrset_all_next;
}
/* remove all records from the answer section that are
* not the same domain name as the query domain name.
* The answer section should contain rrsets with the same name
* as the question. For DNAMEs a CNAME has been synthesized.
* Wildcards have the query name in answer section.
* ANY queries get query name in answer section.
* Remainders of CNAME chains are cut off and resolved by iterator. */
while(rrset && rrset->section == LDNS_SECTION_ANSWER) {
if(dname_pkt_compare(pkt, qinfo->qname, rrset->dname) != 0) {
if(has_additional(rrset->type)) del_addi = 1;
remove_rrset("sanitize: removing extraneous answer "
"RRset:", pkt, msg, prev, &rrset);
continue;
}
prev = rrset;
rrset = rrset->rrset_all_next;
}
/* At this point, we brutally remove ALL rrsets that aren't
* children of the originating zone. The idea here is that,
* as far as we know, the server that we contacted is ONLY
* authoritative for the originating zone. It, of course, MAY
* be authoritative for any other zones, and of course, MAY
* NOT be authoritative for some subdomains of the originating
* zone. */
prev = NULL;
rrset = msg->rrset_first;
while(rrset) {
/* remove private addresses */
if( (rrset->type == LDNS_RR_TYPE_A ||
rrset->type == LDNS_RR_TYPE_AAAA)) {
/* do not set servfail since this leads to too
* many drops of other people using rfc1918 space */
/* also do not remove entire rrset, unless all records
* in it are bad */
if(priv_rrset_bad(ie->priv, pkt, rrset)) {
remove_rrset(NULL, pkt, msg, prev, &rrset);
continue;
}
}
/* skip DNAME records -- they will always be followed by a
* synthesized CNAME, which will be relevant.
* FIXME: should this do something differently with DNAME
* rrsets NOT in Section.ANSWER? */
/* But since DNAME records are also subdomains of the zone,
* same check can be used */
if(!pkt_sub(pkt, rrset->dname, zonename)) {
if(msg->an_rrsets == 0 &&
rrset->type == LDNS_RR_TYPE_NS &&
rrset->section == LDNS_SECTION_AUTHORITY &&
FLAGS_GET_RCODE(msg->flags) ==
LDNS_RCODE_NOERROR && !soa_in_auth(msg) &&
sub_of_pkt(pkt, zonename, rrset->dname)) {
/* noerror, nodata and this NS rrset is above
* the zone. This is LAME!
* Leave in the NS for lame classification. */
/* remove everything from the additional
* (we dont want its glue that was approved
* during the normalize action) */
del_addi = 1;
} else if(!env->cfg->harden_glue && (
rrset->type == LDNS_RR_TYPE_A ||
rrset->type == LDNS_RR_TYPE_AAAA)) {
/* store in cache! Since it is relevant
* (from normalize) it will be picked up
* from the cache to be used later */
store_rrset(pkt, msg, env, rrset);
remove_rrset("sanitize: storing potential "
"poison RRset:", pkt, msg, prev, &rrset);
continue;
} else {
if(has_additional(rrset->type)) del_addi = 1;
remove_rrset("sanitize: removing potential "
"poison RRset:", pkt, msg, prev, &rrset);
continue;
}
}
if(del_addi && rrset->section == LDNS_SECTION_ADDITIONAL) {
remove_rrset("sanitize: removing potential "
"poison reference RRset:", pkt, msg, prev, &rrset);
continue;
}
/* check if right hand side of NSEC is within zone */
if(rrset->type == LDNS_RR_TYPE_NSEC &&
sanitize_nsec_is_overreach(rrset, zonename)) {
remove_rrset("sanitize: removing overreaching NSEC "
"RRset:", pkt, msg, prev, &rrset);
continue;
}
prev = rrset;
rrset = rrset->rrset_all_next;
}
return 1;
}
int
scrub_message(sldns_buffer* pkt, struct msg_parse* msg,
struct query_info* qinfo, uint8_t* zonename, struct regional* region,
struct module_env* env, struct iter_env* ie)
{
/* basic sanity checks */
log_nametypeclass(VERB_ALGO, "scrub for", zonename, LDNS_RR_TYPE_NS,
qinfo->qclass);
if(msg->qdcount > 1)
return 0;
if( !(msg->flags&BIT_QR) )
return 0;
msg->flags &= ~(BIT_AD|BIT_Z); /* force off bit AD and Z */
/* make sure that a query is echoed back when NOERROR or NXDOMAIN */
/* this is not required for basic operation but is a forgery
* resistance (security) feature */
if((FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR ||
FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN) &&
msg->qdcount == 0)
return 0;
/* if a query is echoed back, make sure it is correct. Otherwise,
* this may be not a reply to our query. */
if(msg->qdcount == 1) {
if(dname_pkt_compare(pkt, msg->qname, qinfo->qname) != 0)
return 0;
if(msg->qtype != qinfo->qtype || msg->qclass != qinfo->qclass)
return 0;
}
/* normalize the response, this cleans up the additional. */
if(!scrub_normalize(pkt, msg, qinfo, region))
return 0;
/* delete all out-of-zone information */
if(!scrub_sanitize(pkt, msg, qinfo, zonename, env, ie))
return 0;
return 1;
}
