/* -*- Mode: C; tab-width: 4 -*-
*
* Copyright (c) 2011-2013 Apple Inc. All rights reserved.
*
* 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
*
* 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.
*/
// ***************************************************************************
// nsec.c: This file contains support functions to validate NSEC records for
// NODATA and NXDOMAIN error.
// ***************************************************************************
#include "mDNSEmbeddedAPI.h"
#include "DNSCommon.h"
#include "nsec.h"
#include "nsec3.h"
// Define DNSSEC_DISABLED to remove all the DNSSEC functionality
// and use the stub functions implemented later in this file.
#ifndef DNSSEC_DISABLED
// Implementation Notes
//
// NSEC records in DNSSEC are used for authenticated denial of existence i.e., if the response to a query
// results in NXDOMAIN or NODATA error, the response also contains NSEC records in the additional section
// to prove the non-existence of the original name. In most of the cases, NSEC records don't have any
// relationship to the original name queried i.e, if they are cached based on the name like other records,
// it can't be located to prove the non-existence of the original name. Hence, we create a negative cache
// record like we do for the NXDOMAIN/NODATA error and then cache the NSEC records as part of that. Sometimes,
// NSEC records are also used for wildcard expanded answer in which case they are cached with the cache record
// that is created for the original name. NSEC records are freed when the parent cache (the record that they
// are attached to is expired).
//
// NSEC records also can be queried like any other record and hence can exist independent of the negative
// cache record. It exists as part of negative cache record only when we get a NXDOMAIN/NODATA error with
// NSEC records. When a query results in NXDOMAIN/NODATA error and needs to be validated, the NSEC
// records (and its RRSIGS) are cached as part of the negative cache record. The NSEC records that
// exist separately from the negative cache record should not be used to answer ValidationRequired/
// ValidatingResponse questions as it may not be sufficient to prove the non-existence of the name.
// The exception is when the NSEC record is looked up explicitly. See DNSSECRecordAnswersQuestion
// for more details.
//
mDNSlocal CacheRecord *NSECParentForQuestion(mDNS *const m, DNSQuestion *q)
{
CacheGroup *cg;
CacheRecord *cr;
mDNSu32 namehash;
namehash = DomainNameHashValue(&q->qname);
cg = CacheGroupForName(m, namehash, &q->qname);
if (!cg)
{
LogDNSSEC("NSECParentForQuestion: Cannot find cg for %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
return mDNSNULL;
}
for (cr = cg->members; cr; cr = cr->next)
if (SameNameRecordAnswersQuestion(&cr->resrec, q))
return cr;
return mDNSNULL;
}
mDNSlocal void UpdateParent(DNSSECVerifier *dv)
{
AuthChainLink(dv->parent, dv->ac);
ResetAuthChain(dv);
dv->parent->NumPackets += dv->NumPackets;
}
// Note: This should just call the parent callback which will free the DNSSECVerifier.
mDNSlocal void VerifyNSECCallback(mDNS *const m, DNSSECVerifier *dv, DNSSECStatus status)
{
if (!dv->parent)
{
LogMsg("VerifyNSECCCallback: ERROR!! no parent DV\n");
FreeDNSSECVerifier(m, dv);
return;
}
if (dv->ac)
{
// Before we free the "dv", we need to update the
// parent with our AuthChain information
UpdateParent(dv);
}
// "status" indicates whether we are able to successfully verify
// the NSEC/NSEC3 signatures. For NSEC3, the OptOut flag may be set
// for which we need to deliver insecure result.
if ((dv->parent->flags & NSEC3_OPT_OUT) && (status == DNSSEC_Secure))
{
dv->parent->DVCallback(m, dv->parent, DNSSEC_Insecure);
}
else
{
dv->parent->DVCallback(m, dv->parent, status);
}
// The callback we called in the previous line should recursively
// free all the DNSSECVerifiers starting from dv->parent and above.
// So, set that to NULL and free the "dv" itself here.
dv->parent = mDNSNULL;
FreeDNSSECVerifier(m, dv);
}
// If the caller provides a callback, it takes the responsibility of calling the original callback
// in "pdv" when it is done.
//
// INPUT:
//
// rr: The NSEC record that should be verified
// rv: The NSEC record can also be provided like this
// pdv: Parent DNSSECVerifier which will be called when the verification is done.
// callback: As part of the proof, we need multiple NSEC verifications before we call the "pdv" callback in
// which case a intermediate "callback" is provided which can be used to do multiple verifications.
// ncr: The cache record where the RRSIGS are cached
//
// NSEC records and signatures are cached along with the cache record so that we can expire them all together. We can't cache
// them based on the name hash like other records as in most cases the returned NSECs has a different name than we asked for
// (except for NODATA error where the name exists but type does not exist).
//
mDNSexport void VerifyNSEC(mDNS *const m, ResourceRecord *rr, RRVerifier *rv, DNSSECVerifier *pdv, CacheRecord *ncr, DNSSECVerifierCallback callback)
{
DNSSECVerifier *dv = mDNSNULL;
CacheRecord **rp;
const domainname *name;
mDNSu16 rrtype;
if (!rv && !rr)
{
LogDNSSEC("VerifyNSEC: Both rr and rv are NULL");
goto error;
}
if (!pdv)
{
LogDNSSEC("VerifyNSEC: ERROR!! pdv is NULL");
return;
}
// Remember the name and type for which we are verifying, so that when we are done processing all
// the verifications, we can trace it back.
//
// Note: Currently it is not used because when the verification completes as we just
// call the "pdv" callback which has its origName and origType.
if (rr)
{
name = rr->name;
rrtype = rr->rrtype;
}
else
{
name = &rv->name;
rrtype = rv->rrtype;
}
dv = AllocateDNSSECVerifier(m, name, rrtype, pdv->q.InterfaceID, DNSSEC_VALIDATION_SECURE,
(callback ? callback : VerifyNSECCallback), mDNSNULL);
if (!dv)
{
LogMsg("VerifyNSEC: mDNSPlatformMemAlloc failed");
return;
}
dv->parent = pdv;
if (AddRRSetToVerifier(dv, rr, rv, RRVS_rr) != mStatus_NoError)
{
LogMsg("VerifyNSEC: ERROR!! AddRRSetToVerifier failed to add NSEC");
goto error;
}
// Add the signatures after validating them
rp = &(ncr->nsec);
while (*rp)
{
if ((*rp)->resrec.rrtype == kDNSType_RRSIG)
{
ValidateRRSIG(dv, RRVS_rrsig, &(*rp)->resrec);
}
rp=&(*rp)->next;
}
if (!dv->rrset)
{
LogMsg("VerifyNSEC: ERROR!! AddRRSetToVerifier missing rrset");
goto error;
}
// Expired signatures.
if (!dv->rrsig)
goto error;
// Next step is to fetch the keys
dv->next = RRVS_key;
StartDNSSECVerification(m, dv);
return;
error:
pdv->DVCallback(m, pdv, DNSSEC_Bogus);
if (dv)
{
dv->parent = mDNSNULL;
FreeDNSSECVerifier(m, dv);
}
return;
}
mDNSlocal void DeleteCachedNSECS(mDNS *const m, CacheRecord *cr)
{
CacheRecord *rp, *next;
if (cr->nsec) LogDNSSEC("DeleteCachedNSECS: Deleting NSEC Records\n");
for (rp = cr->nsec; rp; rp = next)
{
next = rp->next;
ReleaseCacheRecord(m, rp);
}
cr->nsec = mDNSNULL;
}
// Returns success if it adds the nsecs and the rrsigs to the cache record. Otherwise, it returns
// failure (mDNSfalse)
mDNSexport mDNSBool AddNSECSForCacheRecord(mDNS *const m, CacheRecord *crlist, CacheRecord *negcr, mDNSu8 rcode)
{
CacheRecord *cr;
mDNSBool nsecs_seen = mDNSfalse;
mDNSBool nsec3s_seen = mDNSfalse;
if (rcode != kDNSFlag1_RC_NoErr && rcode != kDNSFlag1_RC_NXDomain)
{
LogMsg("AddNSECSForCacheRecord: Addings nsecs for rcode %d", rcode);
return mDNSfalse;
}
// Sanity check the list to see if we have anything else other than
// NSECs and its RRSIGs
for (cr = crlist; cr; cr = cr->next)
{
if (cr->resrec.rrtype != kDNSType_NSEC && cr->resrec.rrtype != kDNSType_NSEC3 &&
cr->resrec.rrtype != kDNSType_SOA && cr->resrec.rrtype != kDNSType_RRSIG)
{
LogMsg("AddNSECSForCacheRecord: ERROR!! Adding Wrong record %s", CRDisplayString(m, cr));
return mDNSfalse;
}
if (cr->resrec.rrtype == kDNSType_RRSIG)
{
RDataBody2 *const rdb = (RDataBody2 *)cr->smallrdatastorage.data;
rdataRRSig *rrsig = &rdb->rrsig;
mDNSu16 tc = swap16(rrsig->typeCovered);
if (tc != kDNSType_NSEC && tc != kDNSType_NSEC3 && tc != kDNSType_SOA)
{
LogMsg("AddNSECSForCacheRecord:ERROR!! Adding RRSIG with Wrong type %s", CRDisplayString(m, cr));
return mDNSfalse;
}
}
else if (cr->resrec.rrtype == kDNSType_NSEC)
{
nsecs_seen = mDNStrue;
}
else if (cr->resrec.rrtype == kDNSType_NSEC3)
{
nsec3s_seen = mDNStrue;
}
LogDNSSEC("AddNSECSForCacheRecord: Found a valid record %s", CRDisplayString(m, cr));
}
if ((nsecs_seen && nsec3s_seen) || (!nsecs_seen && !nsec3s_seen))
{
LogDNSSEC("AddNSECSForCacheRecord:ERROR nsecs_seen %d, nsec3s_seen %d", nsecs_seen, nsec3s_seen);
return mDNSfalse;
}
DeleteCachedNSECS(m, negcr);
LogDNSSEC("AddNSECSForCacheRecord: Adding NSEC Records for %s", CRDisplayString(m, negcr));
negcr->nsec = crlist;
return mDNStrue;
}
// Return the number of labels that matches starting from the right (excluding the
// root label)
mDNSexport int CountLabelsMatch(const domainname *const d1, const domainname *const d2)
{
int count, c1, c2;
int match, i, skip1, skip2;
c1 = CountLabels(d1);
skip1 = c1 - 1;
c2 = CountLabels(d2);
skip2 = c2 - 1;
// Root label always matches. And we don't include it here to
// match CountLabels
match = 0;
// Compare as many labels as possible starting from the rightmost
count = c1 < c2 ? c1 : c2;
for (i = count; i > 0; i--)
{
const domainname *da, *db;
da = SkipLeadingLabels(d1, skip1);
db = SkipLeadingLabels(d2, skip2);
if (!SameDomainName(da, db)) return match;
skip1--;
skip2--;
match++;
}
return match;
}
// Empty Non-Terminal (ENT): if the qname is bigger than nsec owner's name and a
// subdomain of the nsec's nxt field, then the qname is a empty non-terminal. For
// example, if you are looking for (in RFC 4035 example zone) "y.w.example A"
// record, if it is a ENT, then it would return
//
// x.w.example. 3600 NSEC x.y.w.example. MX RRSIG NSEC
//
// This function is normally called before checking for wildcard matches. If you
// find this NSEC, there is no need to look for a wildcard record
// that could possibly answer the question.
mDNSlocal mDNSBool NSECAnswersENT(const ResourceRecord *const rr, domainname *qname)
{
const domainname *oname = rr->name;
const RDataBody2 *const rdb = (RDataBody2 *)rr->rdata->u.data;
const domainname *nxt = (const domainname *)&rdb->data;
int ret;
int subdomain;
// Is the owner name smaller than qname?
ret = DNSSECCanonicalOrder(oname, qname, mDNSNULL);
if (ret < 0)
{
// Is the next domain field a subdomain of qname ?
ret = DNSSECCanonicalOrder(nxt, qname, &subdomain);
if (subdomain)
{
if (ret <= 0)
{
LogMsg("NSECAnswersENT: ERROR!! DNSSECCanonicalOrder subdomain set "
" qname %##s, NSEC %##s", qname->c, rr->name->c);
}
return mDNStrue;
}
}
return mDNSfalse;
}
mDNSlocal const domainname *NSECClosestEncloser(ResourceRecord *rr, domainname *qname)
{
const domainname *oname = rr->name;
const RDataBody2 *const rdb = (RDataBody2 *)rr->rdata->u.data;
const domainname *nxt = (const domainname *)&rdb->data;
int match1, match2;
match1 = CountLabelsMatch(oname, qname);
match2 = CountLabelsMatch(nxt, qname);
// Return the closest i.e the one that matches more labels
if (match1 > match2)
return SkipLeadingLabels(oname, CountLabels(oname) - match1);
else
return SkipLeadingLabels(nxt, CountLabels(nxt) - match2);
}
// Assumption: NSEC has been validated outside of this function
//
// Does the name exist given the name and NSEC rr ?
//
// Returns -1 if it is an inappropriate nsec
// Returns 1 if the name exists
// Returns 0 if the name does not exist
//
mDNSlocal int NSECNameExists(mDNS *const m, ResourceRecord *rr, domainname *name, mDNSu16 qtype)
{
const RDataBody2 *const rdb = (RDataBody2 *)rr->rdata->u.data;
const domainname *nxt = (const domainname *)&rdb->data;
const domainname *oname = rr->name; // owner name
int ret1, subdomain1;
int ret2, subdomain2;
int ret3, subdomain3;
ret1 = DNSSECCanonicalOrder(oname, name, &subdomain1);
if (ret1 > 0)
{
LogDNSSEC("NSECNameExists: owner name %##s is bigger than name %##s", oname->c, name->c);
return -1;
}
// Section 4.1 of draft-ietf-dnsext-dnssec-bis-updates-14:
//
// Ancestor delegation NSEC or NSEC3 RRs MUST NOT be used to assume non-
// existence of any RRs below that zone cut, which include all RRs at
// that (original) owner name other than DS RRs, and all RRs below that
// owner name regardless of type.
//
// This also implies that we can't use the child side NSEC for DS question.
if (!ret1)
{
mDNSBool soa = RRAssertsExistence(rr, kDNSType_SOA);
mDNSBool ns = RRAssertsExistence(rr, kDNSType_NS);
// We are here because the owner name is the same as "name". Make sure the
// NSEC has the right NS and SOA bits set.
if (qtype != kDNSType_DS && ns && !soa)
{
LogDNSSEC("NSECNameExists: Parent side NSEC %s can't be used for question %##s (%s)",
RRDisplayString(m, rr), name->c, DNSTypeName(qtype));
return -1;
}
else if (qtype == kDNSType_DS && soa)
{
LogDNSSEC("NSECNameExists: Child side NSEC %s can't be used for question %##s (%s)",
RRDisplayString(m, rr), name->c, DNSTypeName(qtype));
return -1;
}
LogDNSSEC("NSECNameExists: owner name %##s is same as name %##s", oname->c, name->c);
return 1;
}
// If the name is a.b.com and NSEC's owner name is b.com i.e., a subdomain
// and nsec comes from the parent (NS is set and SOA is not set), then this
// NSEC can't be used for names below the owner name.
//
// Similarly if DNAME is set, we can't use it here. See RFC2672-bis-dname
// appendix.
if (subdomain1 && (RRAssertsExistence(rr, kDNSType_DNAME) ||
(RRAssertsNonexistence(rr, kDNSType_SOA) && RRAssertsExistence(rr, kDNSType_NS))))
{
LogDNSSEC("NSECNameExists: NSEC %s comes from the parent, can't use it here",
RRDisplayString(m, rr));
return -1;
}
// At this stage, we know that name is greater than the owner name and
// the nsec is not from the parent side.
//
// Compare with the next field in the nsec.
//
ret2 = DNSSECCanonicalOrder(name, nxt, &subdomain2);
// Exact match with the nsec next name
if (!ret2)
{
LogDNSSEC("NSECNameExists: name %##s is same as nxt name %##s", name->c, nxt->c);
return 1;
}
ret3 = DNSSECCanonicalOrder(oname, nxt, &subdomain3);
if (!ret3)
{
// Pathological case of a single name in the domain. This means only the
// apex of the zone itself exists. Nothing below it. "subdomain2" indicates
// that name is a subdmain of "next" and hence below the zone.
if (subdomain2)
{
LogDNSSEC("NSECNameExists: owner name %##s subdomain of nxt name %##s", oname->c, nxt->c);
return 0;
}
else
{
LogDNSSEC("NSECNameExists: Single name in zone, owner name %##s is same as nxt name %##s", oname->c, nxt->c);
return -1;
}
}
if (ret3 < 0)
{
// Regular NSEC in the zone. Make sure that the "name" lies within
// oname and next. oname < name and name < next
if (ret1 < 0 && ret2 < 0)
{
LogDNSSEC("NSECNameExists: Normal NSEC name %##s lies within owner %##s and nxt name %##s",
name->c, oname->c, nxt->c);
return 0;
}
else
{
LogDNSSEC("NSECNameExists: Normal NSEC name %##s does not lie within owner %##s and nxt name %##s",
name->c, oname->c, nxt->c);
return -1;
}
}
else
{
// Last NSEC in the zone. The "next" is pointing to the apex. All names
// should be a subdomain of that and the name should be bigger than
// oname
if (ret1 < 0 && subdomain2)
{
LogDNSSEC("NSECNameExists: Last NSEC name %##s lies within owner %##s and nxt name %##s",
name->c, oname->c, nxt->c);
return 0;
}
else
{
LogDNSSEC("NSECNameExists: Last NSEC name %##s does not lie within owner %##s and nxt name %##s",
name->c, oname->c, nxt->c);
return -1;
}
}
LogDNSSEC("NSECNameExists: NSEC %s did not match any case", RRDisplayString(m, rr));
return -1;
}
// If the answer was result of a wildcard match, then this function proves
// that a proper wildcard was used to answer the question and that the
// original name does not exist
mDNSexport void WildcardAnswerProof(mDNS *const m, DNSSECVerifier *dv)
{
CacheRecord *ncr;
CacheRecord **rp;
const domainname *ce;
DNSQuestion q;
CacheRecord **nsec3 = mDNSNULL;
LogDNSSEC("WildcardAnswerProof: Question %##s (%s)", dv->origName.c, DNSTypeName(dv->origType));
//
// RFC 4035: Section 3.1.3.3
//
// 1) We used a wildcard because the qname does not exist, so verify
// that the qname does not exist
//
// 2) Is the wildcard the right one ?
//
// Unfortunately, this is not well explained in that section. Refer to
// RFC 5155 section 7.2.6.
// Walk the list of nsecs we received and see if they prove that
// the name does not exist
mDNSPlatformMemZero(&q, sizeof(DNSQuestion));
q.ThisQInterval = -1;
InitializeQuestion(m, &q, dv->InterfaceID, &dv->origName, dv->origType, mDNSNULL, mDNSNULL);
ncr = NSECParentForQuestion(m, &q);
if (!ncr)
{
LogMsg("WildcardAnswerProof: Can't find NSEC Parent for %##s (%s)", q.qname.c, DNSTypeName(q.qtype));
goto error;
}
else
{
LogDNSSEC("WildcardAnswerProof: found %s", CRDisplayString(m, ncr));
}
rp = &(ncr->nsec);
while (*rp)
{
if ((*rp)->resrec.rrtype == kDNSType_NSEC)
{
CacheRecord *cr = *rp;
if (!NSECNameExists(m, &cr->resrec, &dv->origName, dv->origType))
break;
}
else if ((*rp)->resrec.rrtype == kDNSType_NSEC3)
{
nsec3 = rp;
}
rp=&(*rp)->next;
}
if (!(*rp))
{
mDNSBool ret = mDNSfalse;
if (nsec3)
{
ret = NSEC3WildcardAnswerProof(m, ncr, dv);
}
if (!ret)
{
LogDNSSEC("WildcardAnswerProof: NSEC3 wildcard proof failed for %##s (%s)", q.qname.c, DNSTypeName(q.qtype));
goto error;
}
rp = nsec3;
}
else
{
ce = NSECClosestEncloser(&((*rp)->resrec), &dv->origName);
if (!ce)
{
LogMsg("WildcardAnswerProof: ERROR!! Closest Encloser NULL for %##s (%s)", q.qname.c, DNSTypeName(q.qtype));
goto error;
}
if (!SameDomainName(ce, dv->wildcardName))
{
LogMsg("WildcardAnswerProof: ERROR!! Closest Encloser %##s does not match wildcard name %##s", q.qname.c, dv->wildcardName->c);
goto error;
}
}
VerifyNSEC(m, &((*rp)->resrec), mDNSNULL, dv, ncr, mDNSNULL);
return;
error:
dv->DVCallback(m, dv, DNSSEC_Bogus);
}
// We have a NSEC. Need to see if it proves that NODATA exists for the given name. Note that this
// function does not prove anything as proof may require more than one NSEC and this function
// processes only one NSEC at a time.
//
// Returns mDNSfalse if the NSEC does not prove the NODATA error
// Returns mDNStrue if the NSEC proves the NODATA error
//
mDNSlocal mDNSBool NSECNoDataError(mDNS *const m, ResourceRecord *rr, domainname *name, mDNSu16 qtype, domainname **wildcard)
{
const domainname *oname = rr->name; // owner name
*wildcard = mDNSNULL;
// RFC 4035
//
// section 3.1.3.1 : Name matches. Prove that the type does not exist and also CNAME is
// not set as in that case CNAME should have been returned ( CNAME part is mentioned in
// section 4.3 of dnssec-bis-updates.) Without the CNAME check, a positive response can
// be converted to a NODATA/NOERROR response.
//
// section 3.1.3.4 : No exact match for the name but there is a wildcard that could match
// the name but not the type. There are two NSECs in this case. One of them is a wildcard
// NSEC and another NSEC proving that the qname does not exist. We are called with one
// NSEC at a time. We return what we matched and the caller should decide whether all
// conditions are met for the proof.
if (SameDomainName(oname, name))
{
mDNSBool soa = RRAssertsExistence(rr, kDNSType_SOA);
mDNSBool ns = RRAssertsExistence(rr, kDNSType_NS);
if (qtype != kDNSType_DS)
{
// For non-DS type questions, we don't want to use the parent side records to
// answer it
if (ns && !soa)
{
LogDNSSEC("NSECNoDataError: Parent side NSEC %s, can't use for child qname %##s (%s)",
RRDisplayString(m, rr), name->c, DNSTypeName(qtype));
return mDNSfalse;
}
}
else
{
if (soa)
{
LogDNSSEC("NSECNoDataError: Child side NSEC %s, can't use for parent qname %##s (%s)",
RRDisplayString(m, rr), name->c, DNSTypeName(qtype));
return mDNSfalse;
}
}
if (RRAssertsExistence(rr, qtype) || RRAssertsExistence(rr, kDNSType_CNAME))
{
LogMsg("NSECNoDataError: ERROR!! qtype %s exists in %s", DNSTypeName(qtype), RRDisplayString(m, rr));
return mDNSfalse;
}
LogDNSSEC("NSECNoDataError: qype %s does not exist in %s", DNSTypeName(qtype), RRDisplayString(m, rr));
return mDNStrue;
}
else
{
// Name does not exist. Before we check for a wildcard match, make sure that
// this is not an ENT.
if (NSECAnswersENT(rr, name))
{
LogDNSSEC("NSECNoDataError: name %##s exists %s", name->c, RRDisplayString(m, rr));
return mDNSfalse;
}
// Wildcard check. If this is a wildcard NSEC, then check to see if we could
// have answered the question using this wildcard and it should not have the
// "qtype" passed in with its bitmap.
//
// See RFC 4592, on how wildcards are used to synthesize answers. Find the
// closest encloser and the qname should be a subdomain i.e if the wildcard
// is *.x.example, x.example is the closest encloser and the qname should be
// a subdomain e.g., y.x.example or z.y.x.example and so on.
if (oname->c[0] == 1 && oname->c[1] == '*')
{
int s;
const domainname *ce = SkipLeadingLabels(oname, 1);
DNSSECCanonicalOrder(name, ce, &s);
if (s)
{
if (RRAssertsExistence(rr, qtype) || RRAssertsExistence(rr, kDNSType_CNAME))
{
LogMsg("NSECNoDataError: ERROR!! qtype %s exists in wildcard %s", DNSTypeName(qtype), RRDisplayString(m, rr));
return mDNSfalse;
}
if (qtype == kDNSType_DS && RRAssertsExistence(rr, kDNSType_SOA))
{
LogDNSSEC("NSECNoDataError: Child side wildcard NSEC %s, can't use for parent qname %##s (%s)",
RRDisplayString(m, rr), name->c, DNSTypeName(qtype));
return mDNSfalse;
}
else if (qtype != kDNSType_DS && RRAssertsNonexistence(rr, kDNSType_SOA) &&
RRAssertsExistence(rr, kDNSType_NS))
{
// Don't use the parent side record for this
LogDNSSEC("NSECNoDataError: Parent side wildcard NSEC %s, can't use for child qname %##s (%s)",
RRDisplayString(m, rr), name->c, DNSTypeName(qtype));
return mDNSfalse;
}
*wildcard = (domainname *)ce;
LogDNSSEC("NSECNoDataError: qtype %s does not exist in wildcard %s", DNSTypeName(qtype), RRDisplayString(m, rr));
return mDNStrue;
}
}
return mDNSfalse;
}
}
mDNSexport void NoDataNSECCallback(mDNS *const m, DNSSECVerifier *dv, DNSSECStatus status)
{
RRVerifier *rv;
DNSSECVerifier *pdv;
CacheRecord *ncr;
LogDNSSEC("NoDataNSECCallback: called");
if (!dv->parent)
{
LogMsg("NoDataNSECCCallback: no parent DV");
FreeDNSSECVerifier(m, dv);
return;
}
if (dv->ac)
{
// Before we free the "dv", we need to update the
// parent with our AuthChain information
UpdateParent(dv);
}
pdv = dv->parent;
// We don't care about the "dv" that was allocated in VerifyNSEC
// as it just verifies one of the nsecs. Get the original verifier and
// verify the other NSEC like we did the first time.
dv->parent = mDNSNULL;
FreeDNSSECVerifier(m, dv);
if (status != DNSSEC_Secure)
{
goto error;
}
ncr = NSECParentForQuestion(m, &pdv->q);
if (!ncr)
{
LogMsg("NoDataNSECCallback: Can't find NSEC Parent for %##s (%s)", pdv->q.qname.c, DNSTypeName(pdv->q.qtype));
goto error;
}
rv = pdv->pendingNSEC;
pdv->pendingNSEC = rv->next;
// We might have more than one pendingNSEC in the case of NSEC3. If this is the last one,
// we don't need to come back here; let the regular NSECCallback call the original callback.
rv->next = mDNSNULL;
LogDNSSEC("NoDataNSECCallback: Verifying %##s (%s)", rv->name.c, DNSTypeName(rv->rrtype));
if (!pdv->pendingNSEC)
VerifyNSEC(m, mDNSNULL, rv, pdv, ncr, mDNSNULL);
else
VerifyNSEC(m, mDNSNULL, rv, pdv, ncr, NoDataNSECCallback);
return;
error:
pdv->DVCallback(m, pdv, status);
}
mDNSexport void NameErrorNSECCallback(mDNS *const m, DNSSECVerifier *dv, DNSSECStatus status)
{
RRVerifier *rv;
DNSSECVerifier *pdv;
CacheRecord *ncr;
LogDNSSEC("NameErrorNSECCallback: called");
if (!dv->parent)
{
LogMsg("NameErrorNSECCCallback: no parent DV");
FreeDNSSECVerifier(m, dv);
return;
}
if (dv->ac)
{
// Before we free the "dv", we need to update the
// parent with our AuthChain information
UpdateParent(dv);
}
pdv = dv->parent;
// We don't care about the "dv" that was allocated in VerifyNSEC
// as it just verifies one of the nsecs. Get the original verifier and
// verify the other NSEC like we did the first time.
dv->parent = mDNSNULL;
FreeDNSSECVerifier(m, dv);
if (status != DNSSEC_Secure)
{
goto error;
}
ncr = NSECParentForQuestion(m, &pdv->q);
if (!ncr)
{
LogMsg("NameErrorNSECCallback: Can't find NSEC Parent for %##s (%s)", pdv->q.qname.c, DNSTypeName(pdv->q.qtype));
goto error;
}
rv = pdv->pendingNSEC;
pdv->pendingNSEC = rv->next;
// We might have more than one pendingNSEC in the case of NSEC3. If this is the last one,
// we don't need to come back here; let the regular NSECCallback call the original callback.
rv->next = mDNSNULL;
LogDNSSEC("NameErrorNSECCallback: Verifying %##s (%s)", rv->name.c, DNSTypeName(rv->rrtype));
if (!pdv->pendingNSEC)
VerifyNSEC(m, mDNSNULL, rv, pdv, ncr, mDNSNULL);
else
VerifyNSEC(m, mDNSNULL, rv, pdv, ncr, NameErrorNSECCallback);
return;
error:
pdv->DVCallback(m, pdv, status);
}
// We get a NODATA error with no records in answer section. This proves
// that qname does not exist.
mDNSlocal void NoDataProof(mDNS *const m, DNSSECVerifier *dv, CacheRecord *ncr)
{
CacheRecord **rp;
domainname *wildcard = mDNSNULL;
const domainname *ce = mDNSNULL;
ResourceRecord *nsec_wild = mDNSNULL;
ResourceRecord *nsec_noname = mDNSNULL;
// NODATA Error could mean two things. The name exists with no type or there is a
// wildcard that matches the name but no type. This is done by NSECNoDataError.
//
// If it is the case of wildcard, there are two NSECs. One is the wildcard NSEC and
// the other NSEC to prove that there is no other closer match.
wildcard = mDNSNULL;
rp = &(ncr->nsec);
while (*rp)
{
if ((*rp)->resrec.rrtype == kDNSType_NSEC)
{
CacheRecord *cr = *rp;
if (NSECNoDataError(m, &cr->resrec, &dv->q.qname, dv->q.qtype, &wildcard))
{
if (wildcard)
{
dv->flags |= WILDCARD_PROVES_NONAME_EXISTS;
LogDNSSEC("NoDataProof: NSEC %s proves NODATA error for %##s (%s)",
RRDisplayString(m, &(*rp)->resrec), dv->q.qname.c, DNSTypeName(dv->q.qtype));
}
else
{
dv->flags |= NSEC_PROVES_NOTYPE_EXISTS;
LogDNSSEC("NoDataProof: NSEC %s proves NOTYPE error for %##s (%s)",
RRDisplayString(m, &(*rp)->resrec), dv->q.qname.c, DNSTypeName(dv->q.qtype));
}
nsec_wild = &cr->resrec;
}
if (!NSECNameExists(m, &cr->resrec, &dv->q.qname, dv->q.qtype))
{
LogDNSSEC("NoDataProof: NSEC %s proves that name %##s (%s) does not exist",
RRDisplayString(m, &(*rp)->resrec), dv->q.qname.c, DNSTypeName(dv->q.qtype));
// If we have a wildcard, then we should check to see if the closest
// encloser is the same as the wildcard.
ce = NSECClosestEncloser(&cr->resrec, &dv->q.qname);
dv->flags |= NSEC_PROVES_NONAME_EXISTS;
nsec_noname = &cr->resrec;
}
}
rp=&(*rp)->next;
}
if (!nsec_noname && !nsec_wild)
{
LogDNSSEC("NoDataProof: No valid NSECs for %##s (%s)", dv->q.qname.c, DNSTypeName(dv->q.qtype));
goto error;
}
// If the type exists, then we have to verify just that NSEC
if (!(dv->flags & NSEC_PROVES_NOTYPE_EXISTS))
{
// If we have a wildcard, then we should have a "ce" which matches the wildcard
// If we don't have a wildcard, then we should have proven that the name does not
// exist which means we would have set the "ce".
if (wildcard && !ce)
{
LogMsg("NoDataProof: Cannot prove that the name %##s (%s) does not exist", dv->q.qname.c, DNSTypeName(dv->q.qtype));
goto error;
}
if (wildcard && !SameDomainName(wildcard, ce))
{
LogMsg("NoDataProof: wildcard %##s does not match closest encloser %##s", wildcard->c, ce->c);
goto error;
}
// If a single NSEC can prove both, then we just have validate that one NSEC.
if (nsec_wild == nsec_noname)
{
nsec_noname = mDNSNULL;
dv->flags &= ~NSEC_PROVES_NONAME_EXISTS;
}
}
if ((dv->flags & (WILDCARD_PROVES_NONAME_EXISTS|NSEC_PROVES_NONAME_EXISTS)) ==
(WILDCARD_PROVES_NONAME_EXISTS|NSEC_PROVES_NONAME_EXISTS))
{
mStatus status;
RRVerifier *r = AllocateRRVerifier(nsec_noname, &status);
if (!r) goto error;
// First verify wildcard NSEC and then when we are done, we
// will verify the noname nsec
dv->pendingNSEC = r;
LogDNSSEC("NoDataProof: Verifying wild and noname %s", nsec_wild ? RRDisplayString(m, nsec_wild) : "NULL");
VerifyNSEC(m, nsec_wild, mDNSNULL, dv, ncr, NoDataNSECCallback);
}
else if ((dv->flags & WILDCARD_PROVES_NONAME_EXISTS) ||
(dv->flags & NSEC_PROVES_NOTYPE_EXISTS))
{
LogDNSSEC("NoDataProof: Verifying wild %s", nsec_wild ? RRDisplayString(m, nsec_wild) : "NULL");
VerifyNSEC(m, nsec_wild, mDNSNULL, dv, ncr, mDNSNULL);
}
else if (dv->flags & NSEC_PROVES_NONAME_EXISTS)
{
LogDNSSEC("NoDataProof: Verifying noname %s", nsec_noname ? RRDisplayString(m, nsec_noname) : "NULL");
VerifyNSEC(m, nsec_noname, mDNSNULL, dv, ncr, mDNSNULL);
}
return;
error:
LogDNSSEC("NoDataProof: Error return");
dv->DVCallback(m, dv, DNSSEC_Bogus);
}
mDNSlocal mDNSBool NSECNoWildcard(mDNS *const m, ResourceRecord *rr, domainname *qname, mDNSu16 qtype)
{
const domainname *ce;
domainname wild;
// If the query name is c.x.w.example and if the name does not exist, we should get
// get a nsec back that looks something like this:
//
// w.example NSEC a.w.example
//
// First, we need to get the closest encloser which in this case is w.example. Wild
// card synthesis works by finding the closest encloser first and then look for
// a "*" label (assuming * label does not appear in the question). If it does not
// exists, it would return the NSEC at that name. And the wildcard name at the
// closest encloser "*.w.example" would be covered by such an NSEC. (Appending "*"
// makes it bigger than w.example and "* is smaller than "a" for the above NSEC)
//
ce = NSECClosestEncloser(rr, qname);
if (!ce) { LogMsg("NSECNoWildcard: No closest encloser for rr %s, qname %##s (%s)", qname->c, DNSTypeName(qtype)); return mDNSfalse; }
wild.c[0] = 1;
wild.c[1] = '*';
wild.c[2] = 0;
if (!AppendDomainName(&wild, ce))
{
LogMsg("NSECNoWildcard: ERROR!! Can't append domainname closest encloser name %##s, qname %##s (%s)", ce->c, qname->c, DNSTypeName(qtype));
return mDNSfalse;
}
if (NSECNameExists(m, rr, &wild, qtype) != 0)
{
LogDNSSEC("NSECNoWildcard: Wildcard name %##s exists or not valid qname %##s (%s)", wild.c, qname->c, DNSTypeName(qtype));
return mDNSfalse;
}
LogDNSSEC("NSECNoWildcard: Wildcard name %##s does not exist for record %s, qname %##s (%s)", wild.c,
RRDisplayString(m, rr), qname->c, DNSTypeName(qtype));
return mDNStrue;
}
// We get a NXDOMAIN error with no records in answer section. This proves
// that qname does not exist.
mDNSlocal void NameErrorProof(mDNS *const m, DNSSECVerifier *dv, CacheRecord *ncr)
{
CacheRecord **rp;
ResourceRecord *nsec_wild = mDNSNULL;
ResourceRecord *nsec_noname = mDNSNULL;
mStatus status;
// NXDOMAIN Error. We need to prove that the qname does not exist and there
// is no wildcard that can be used to answer the question.
rp = &(ncr->nsec);
while (*rp)
{
if ((*rp)->resrec.rrtype == kDNSType_NSEC)
{
CacheRecord *cr = *rp;
if (!NSECNameExists(m, &cr->resrec, &dv->q.qname, dv->q.qtype))
{
LogDNSSEC("NameErrorProof: NSEC %s proves name does not exist for %##s (%s)",
RRDisplayString(m, &(*rp)->resrec), dv->q.qname.c, DNSTypeName(dv->q.qtype));
// If we have a wildcard, then we should check to see if the closest
// encloser is the same as the wildcard.
dv->flags |= NSEC_PROVES_NONAME_EXISTS;
nsec_noname = &cr->resrec;
}
if (NSECNoWildcard(m, &cr->resrec, &dv->q.qname, dv->q.qtype))
{
dv->flags |= WILDCARD_PROVES_NONAME_EXISTS;
nsec_wild = &cr->resrec;
LogDNSSEC("NameErrorProof: NSEC %s proves wildcard cannot answer question for %##s (%s)",
RRDisplayString(m, &(*rp)->resrec), dv->q.qname.c, DNSTypeName(dv->q.qtype));
}
}
rp=&(*rp)->next;
}
if (!nsec_noname || !nsec_wild)
{
LogMsg("NameErrorProof: Proof failed for %##s (%s) noname %p, wild %p", dv->q.qname.c, DNSTypeName(dv->q.qtype), nsec_noname, nsec_wild);
goto error;
}
// First verify wildcard NSEC and then when we are done, we will verify the noname nsec.
// Sometimes a single NSEC can prove both that the "qname" does not exist and a wildcard
// could not have produced qname. These are a few examples where this can happen.
//
// 1. If the zone is example.com and you look up *.example.com and if there are no wildcards,
// you will get a NSEC back "example.com NSEC a.example.com". This proves that both the
// name does not exist and *.example.com also does not exist
//
// 2. If the zone is example.com and it has a record like this:
//
// example.com NSEC d.example.com
//
// any name you lookup in between like a.example.com,b.example.com etc. you will get a single
// NSEC back. In that case we just have to verify only once.
//
if (nsec_wild != nsec_noname)
{
RRVerifier *r = AllocateRRVerifier(nsec_noname, &status);
if (!r) goto error;
dv->pendingNSEC = r;
LogDNSSEC("NoDataProof: Verifying wild %s", RRDisplayString(m, nsec_wild));
VerifyNSEC(m, nsec_wild, mDNSNULL, dv, ncr, NameErrorNSECCallback);
}
else
{
LogDNSSEC("NoDataProof: Verifying only one %s", RRDisplayString(m, nsec_wild));
VerifyNSEC(m, nsec_wild, mDNSNULL, dv, ncr, mDNSNULL);
}
return;
error:
dv->DVCallback(m, dv, DNSSEC_Bogus);
}
mDNSexport CacheRecord *NSECRecordIsDelegation(mDNS *const m, domainname *name, mDNSu16 qtype)
{
CacheGroup *cg;
CacheRecord *cr;
mDNSu32 namehash;
namehash = DomainNameHashValue(name);
cg = CacheGroupForName(m, namehash, name);
if (!cg)
{
LogDNSSEC("NSECRecordForName: cg NULL for %##s", name);
return mDNSNULL;
}
for (cr = cg->members; cr; cr = cr->next)
{
if (cr->resrec.RecordType == kDNSRecordTypePacketNegative && cr->resrec.rrtype == qtype)
{
CacheRecord *ncr;
for (ncr = cr->nsec; ncr; ncr = ncr->next)
{
if (ncr->resrec.rrtype == kDNSType_NSEC &&
SameDomainName(ncr->resrec.name, name))
{
// See the Insecure Delegation Proof section in dnssec-bis: DS bit and SOA bit
// should be absent
if (RRAssertsExistence(&ncr->resrec, kDNSType_SOA) ||
RRAssertsExistence(&ncr->resrec, kDNSType_DS))
{
LogDNSSEC("NSECRecordForName: found record %s for %##s (%s), but DS or SOA bit set", CRDisplayString(m, ncr), name,
DNSTypeName(qtype));
return mDNSNULL;
}
// Section 2.3 of RFC 4035 states that:
//
// Each owner name in the zone that has authoritative data or a delegation point NS RRset MUST
// have an NSEC resource record.
//
// So, if we have an NSEC record matching the question name with the NS bit set,
// then this is a delegation.
//
if (RRAssertsExistence(&ncr->resrec, kDNSType_NS))
{
LogDNSSEC("NSECRecordForName: found record %s for %##s (%s)", CRDisplayString(m, ncr), name, DNSTypeName(qtype));
return ncr;
}
else
{
LogDNSSEC("NSECRecordForName: found record %s for %##s (%s), but NS bit is not set", CRDisplayString(m, ncr), name,
DNSTypeName(qtype));
return mDNSNULL;
}
}
}
}
}
return mDNSNULL;
}
mDNSlocal void StartInsecureProof(mDNS * const m, DNSSECVerifier *dv)
{
domainname trigger;
DNSSECVerifier *prevdv = mDNSNULL;
// Remember the name that triggered the insecure proof
AssignDomainName(&trigger, &dv->q.qname);
while (dv->parent)
{
prevdv = dv;
dv = dv->parent;
}
if (prevdv)
{
prevdv->parent = mDNSNULL;
FreeDNSSECVerifier(m, prevdv);
}
// For Optional DNSSEC, we are opportunistically verifying dnssec. We don't care
// if something results in bogus as we still want to deliver results to the
// application e.g., CNAME processing results in bogus because the path is broken,
// but we still want to follow CNAMEs so that we can deliver the final results to
// the application.
if (dv->ValidationRequired == DNSSEC_VALIDATION_SECURE_OPTIONAL)
{
LogDNSSEC("StartInsecureProof: Aborting insecure proof for %##s (%s)", dv->q.qname.c, DNSTypeName(dv->q.qtype));
dv->DVCallback(m, dv, DNSSEC_Bogus);
return;
}
LogDNSSEC("StartInsecureProof for %##s (%s)", dv->q.qname.c, DNSTypeName(dv->q.qtype));
// Don't start the insecure proof again after we finish the one that we start here by
// setting InsecureProofDone.
dv->InsecureProofDone = 1;
ProveInsecure(m, dv, mDNSNULL, &trigger);
return;
}
mDNSexport void ValidateWithNSECS(mDNS *const m, DNSSECVerifier *dv, CacheRecord *cr)
{
LogDNSSEC("ValidateWithNSECS: called for %s", CRDisplayString(m, cr));
// If we are encountering a break in the chain of trust i.e., NSEC/NSEC3s for
// DS query, then do the insecure proof. This is important because if we
// validate these NSECs normally and prove that they are "secure", we will
// end up delivering the secure result to the original question where as
// these NSEC/NSEC3s actually prove that DS does not exist and hence insecure.
//
// This break in the chain can happen after we have partially validated the
// path (dv->ac is non-NULL) or the first time (dv->ac is NULL) after we
// fetched the DNSKEY (dv->key is non-NULL). We don't want to do this
// if we have just started the non-existence proof (dv->key is NULL) as
// it does not indicate a break in the chain of trust.
//
// If we are already doing a insecurity proof, don't start another one. In
// the case of NSECs, it is possible that insecurity proof starts and it
// gets NSECs and as part of validating that we receive more NSECS in which
// case we don't want to start another insecurity proof.
if (dv->ValidationRequired != DNSSEC_VALIDATION_INSECURE &&
(!dv->parent || dv->parent->ValidationRequired != DNSSEC_VALIDATION_INSECURE))
{
if ((dv->ac && dv->q.qtype == kDNSType_DS) ||
(!dv->ac && dv->key && dv->q.qtype == kDNSType_DS))
{
LogDNSSEC("ValidateWithNSECS: Starting insecure proof: name %##s ac %p, key %p, parent %p", dv->q.qname.c,
dv->ac, dv->key, dv->parent);
StartInsecureProof(m, dv);
return;
}
}
// "parent" is set when we are validating a NSEC and we should not be here in
// the normal case when parent is set. For example, we are looking up the A
// record for www.example.com and following can happen.
//
// a) Record does not exist and we get a NSEC
// b) While validating (a), we get an NSEC for the first DS record that we look up
// c) Record exists but we get NSECs for the first DS record
// d) We are able to partially validate (a) or (b), but we get NSECs somewhere in
// the chain
//
// For (a), parent is not set as we are not validating the NSEC yet. Hence we would
// start the validation now.
//
// For (b), the parent is set, but should be caught by the above "if" block because we
// should have gotten the DNSKEY at least. In the case of nested insecurity proof,
// we would end up here and fail with bogus.
//
// For (c), the parent is not set and should be caught by the above "if" block because we
// should have gotten the DNSKEY at least.
//
// For (d), the above "if" block would catch it as "dv->ac" is non-NULL.
//
// Hence, we should not come here in the normal case. Possible pathological cases are:
// Insecure proof getting NSECs while validating NSECs, getting NSECs for DNSKEY for (c)
// above etc.
if (dv->parent)
{
LogDNSSEC("ValidateWithNSECS: dv parent set for %##s (%s)", dv->q.qname.c, DNSTypeName(dv->q.qtype));
dv->DVCallback(m, dv, DNSSEC_Bogus);
return;
}
if (cr->resrec.RecordType == kDNSRecordTypePacketNegative)
{
mDNSu8 rcode;
CacheRecord *neg = cr->nsec;
mDNSBool nsecs_seen = mDNSfalse;
while (neg)
{
// The list can only have NSEC or NSEC3s. This was checked when we added the
// NSECs to the cache record.
if (neg->resrec.rrtype == kDNSType_NSEC)
nsecs_seen = mDNStrue;
LogDNSSEC("ValidateWithNSECS: NSECCached Record %s", CRDisplayString(m, neg));
neg = neg->next;
}
rcode = (mDNSu8)(cr->responseFlags.b[1] & kDNSFlag1_RC_Mask);
if (rcode == kDNSFlag1_RC_NoErr)
{
if (nsecs_seen)
NoDataProof(m, dv, cr);
else
NSEC3NoDataProof(m, dv, cr);
}
else if (rcode == kDNSFlag1_RC_NXDomain)
{
if (nsecs_seen)
NameErrorProof(m, dv, cr);
else
NSEC3NameErrorProof(m, dv, cr);
}
else
{
LogDNSSEC("ValidateWithNSECS: Rcode %d invalid", rcode);
dv->DVCallback(m, dv, DNSSEC_Bogus);
}
}
else
{
LogMsg("ValidateWithNSECS: Not a valid cache record %s for NSEC proofs", CRDisplayString(m, cr));
dv->DVCallback(m, dv, DNSSEC_Bogus);
return;
}
}
#else // !DNSSEC_DISABLED
mDNSexport mDNSBool AddNSECSForCacheRecord(mDNS *const m, CacheRecord *crlist, CacheRecord *negcr, mDNSu8 rcode)
{
(void)m;
(void)crlist;
(void)negcr;
(void)rcode;
return mDNSfalse;
}
#endif // !DNSSEC_DISABLED
