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gecko-dev/security/pkix/lib/pkixocsp.cpp

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This code is made available to you under your choice of the following sets
* of licensing terms:
*/
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
/* Copyright 2013 Mozilla Contributors
*
* 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.
*/
#include <limits>
#include "pkix/pkix.h"
#include "pkixcheck.h"
#include "pkixutil.h"
namespace {
const size_t SHA1_DIGEST_LENGTH = 160 / 8;
} // unnamed namespace
namespace mozilla { namespace pkix {
// These values correspond to the tag values in the ASN.1 CertStatus
enum class CertStatus : uint8_t {
Good = der::CONTEXT_SPECIFIC | 0,
Revoked = der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 1,
Unknown = der::CONTEXT_SPECIFIC | 2
};
class Context final
{
public:
Context(TrustDomain& trustDomain, const CertID& certID, Time time,
uint16_t maxLifetimeInDays, /*optional out*/ Time* thisUpdate,
/*optional out*/ Time* validThrough)
: trustDomain(trustDomain)
, certID(certID)
, time(time)
, maxLifetimeInDays(maxLifetimeInDays)
, certStatus(CertStatus::Unknown)
, thisUpdate(thisUpdate)
, validThrough(validThrough)
, expired(false)
, matchFound(false)
{
if (thisUpdate) {
*thisUpdate = TimeFromElapsedSecondsAD(0);
}
if (validThrough) {
*validThrough = TimeFromElapsedSecondsAD(0);
}
}
TrustDomain& trustDomain;
const CertID& certID;
const Time time;
const uint16_t maxLifetimeInDays;
CertStatus certStatus;
Time* thisUpdate;
Time* validThrough;
bool expired;
// Keep track of whether the OCSP response contains the status of the
// certificate we're interested in. Responders might reply without
// including the status of any of the requested certs, we should
// indicate a server failure in those cases.
bool matchFound;
Context(const Context&) = delete;
void operator=(const Context&) = delete;
};
// Verify that potentialSigner is a valid delegated OCSP response signing cert
// according to RFC 6960 section 4.2.2.2.
static Result
CheckOCSPResponseSignerCert(TrustDomain& trustDomain,
BackCert& potentialSigner,
Input issuerSubject,
Input issuerSubjectPublicKeyInfo,
Time time)
{
Result rv;
// We don't need to do a complete verification of the signer (i.e. we don't
// have to call BuildCertChain to verify the entire chain) because we
// already know that the issuer is valid, since revocation checking is done
// from the root to the parent after we've built a complete chain that we
// know is otherwise valid. Rather, we just need to do a one-step validation
// from potentialSigner to the issuer.
//
// It seems reasonable to require the KU_DIGITAL_SIGNATURE key usage on the
// OCSP responder certificate if the OCSP responder certificate has a
// key usage extension. However, according to bug 240456, some OCSP responder
// certificates may have only the nonRepudiation bit set. Also, the OCSP
// specification (RFC 6960) does not mandate any particular key usage to be
// asserted for OCSP responde signers. Oddly, the CABForum Baseline
// Requirements v.1.1.5 do say "If the Root CA Private Key is used for
// signing OCSP responses, then the digitalSignature bit MUST be set."
//
// Note that CheckIssuerIndependentProperties processes
// SEC_OID_OCSP_RESPONDER in the way that the OCSP specification requires us
// to--in particular, it doesn't allow SEC_OID_OCSP_RESPONDER to be implied
// by a missing EKU extension, unlike other EKUs.
//
// TODO(bug 926261): If we're validating for a policy then the policy OID we
// are validating for should be passed to CheckIssuerIndependentProperties.
TrustLevel unusedTrustLevel;
rv = CheckIssuerIndependentProperties(trustDomain, potentialSigner, time,
KeyUsage::noParticularKeyUsageRequired,
KeyPurposeId::id_kp_OCSPSigning,
CertPolicyId::anyPolicy, 0,
unusedTrustLevel);
if (rv != Success) {
return rv;
}
// It is possible that there exists a certificate with the same key as the
// issuer but with a different name, so we need to compare names
// XXX(bug 926270) XXX(bug 1008133) XXX(bug 980163): Improve name
// comparison.
// TODO: needs test
if (!InputsAreEqual(potentialSigner.GetIssuer(), issuerSubject)) {
return Result::ERROR_OCSP_RESPONDER_CERT_INVALID;
}
// TODO(bug 926260): check name constraints
rv = VerifySignedData(trustDomain, potentialSigner.GetSignedData(),
issuerSubjectPublicKeyInfo);
// TODO: check for revocation of the OCSP responder certificate unless no-check
// or the caller forcing no-check. To properly support the no-check policy, we'd
// need to enforce policy constraints from the issuerChain.
return rv;
}
enum class ResponderIDType : uint8_t
{
byName = der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 1,
byKey = der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 2
};
static inline Result OCSPResponse(Reader&, Context&);
static inline Result ResponseBytes(Reader&, Context&);
static inline Result BasicResponse(Reader&, Context&);
static inline Result ResponseData(
Reader& tbsResponseData,
Context& context,
const der::SignedDataWithSignature& signedResponseData,
const DERArray& certs);
static inline Result SingleResponse(Reader& input, Context& context);
static Result ExtensionNotUnderstood(Reader& extnID, Input extnValue,
bool critical, /*out*/ bool& understood);
static inline Result CertID(Reader& input,
const Context& context,
/*out*/ bool& match);
static Result MatchKeyHash(TrustDomain& trustDomain,
Input issuerKeyHash,
Input issuerSubjectPublicKeyInfo,
/*out*/ bool& match);
static Result KeyHash(TrustDomain& trustDomain,
Input subjectPublicKeyInfo,
/*out*/ uint8_t* hashBuf, size_t hashBufSize);
static Result
MatchResponderID(TrustDomain& trustDomain,
ResponderIDType responderIDType,
Input responderID,
Input potentialSignerSubject,
Input potentialSignerSubjectPublicKeyInfo,
/*out*/ bool& match)
{
match = false;
switch (responderIDType) {
case ResponderIDType::byName:
// XXX(bug 926270) XXX(bug 1008133) XXX(bug 980163): Improve name
// comparison.
match = InputsAreEqual(responderID, potentialSignerSubject);
return Success;
case ResponderIDType::byKey:
{
Reader input(responderID);
Input keyHash;
Result rv = der::ExpectTagAndGetValue(input, der::OCTET_STRING, keyHash);
if (rv != Success) {
return rv;
}
return MatchKeyHash(trustDomain, keyHash,
potentialSignerSubjectPublicKeyInfo, match);
}
MOZILLA_PKIX_UNREACHABLE_DEFAULT_ENUM
}
}
static Result
VerifyOCSPSignedData(TrustDomain& trustDomain,
const der::SignedDataWithSignature& signedResponseData,
Input spki)
{
Result rv = VerifySignedData(trustDomain, signedResponseData, spki);
if (rv == Result::ERROR_BAD_SIGNATURE) {
rv = Result::ERROR_OCSP_BAD_SIGNATURE;
}
return rv;
}
// RFC 6960 section 4.2.2.2: The OCSP responder must either be the issuer of
// the cert or it must be a delegated OCSP response signing cert directly
// issued by the issuer. If the OCSP responder is a delegated OCSP response
// signer, then its certificate is (probably) embedded within the OCSP
// response and we'll need to verify that it is a valid certificate that chains
// *directly* to issuerCert.
static Result
VerifySignature(Context& context, ResponderIDType responderIDType,
Input responderID, const DERArray& certs,
const der::SignedDataWithSignature& signedResponseData)
{
bool match;
Result rv = MatchResponderID(context.trustDomain, responderIDType,
responderID, context.certID.issuer,
context.certID.issuerSubjectPublicKeyInfo,
match);
if (rv != Success) {
return rv;
}
if (match) {
return VerifyOCSPSignedData(context.trustDomain, signedResponseData,
context.certID.issuerSubjectPublicKeyInfo);
}
size_t numCerts = certs.GetLength();
for (size_t i = 0; i < numCerts; ++i) {
BackCert cert(*certs.GetDER(i), EndEntityOrCA::MustBeEndEntity, nullptr);
rv = cert.Init();
if (rv != Success) {
return rv;
}
rv = MatchResponderID(context.trustDomain, responderIDType, responderID,
cert.GetSubject(), cert.GetSubjectPublicKeyInfo(),
match);
if (rv != Success) {
if (IsFatalError(rv)) {
return rv;
}
continue;
}
if (match) {
rv = CheckOCSPResponseSignerCert(context.trustDomain, cert,
context.certID.issuer,
context.certID.issuerSubjectPublicKeyInfo,
context.time);
if (rv != Success) {
if (IsFatalError(rv)) {
return rv;
}
continue;
}
return VerifyOCSPSignedData(context.trustDomain, signedResponseData,
cert.GetSubjectPublicKeyInfo());
}
}
return Result::ERROR_OCSP_INVALID_SIGNING_CERT;
}
static inline Result
MapBadDERToMalformedOCSPResponse(Result rv)
{
if (rv == Result::ERROR_BAD_DER) {
return Result::ERROR_OCSP_MALFORMED_RESPONSE;
}
return rv;
}
Result
VerifyEncodedOCSPResponse(TrustDomain& trustDomain, const struct CertID& certID,
Time time, uint16_t maxOCSPLifetimeInDays,
Input encodedResponse,
/*out*/ bool& expired,
/*optional out*/ Time* thisUpdate,
/*optional out*/ Time* validThrough)
{
// Always initialize this to something reasonable.
expired = false;
Context context(trustDomain, certID, time, maxOCSPLifetimeInDays,
thisUpdate, validThrough);
Reader input(encodedResponse);
Result rv = der::Nested(input, der::SEQUENCE, [&context](Reader& r) {
return OCSPResponse(r, context);
});
if (rv != Success) {
return MapBadDERToMalformedOCSPResponse(rv);
}
rv = der::End(input);
if (rv != Success) {
return MapBadDERToMalformedOCSPResponse(rv);
}
if (!context.matchFound) {
return Result::ERROR_OCSP_RESPONSE_FOR_CERT_MISSING;
}
expired = context.expired;
switch (context.certStatus) {
case CertStatus::Good:
if (expired) {
return Result::ERROR_OCSP_OLD_RESPONSE;
}
return Success;
case CertStatus::Revoked:
return Result::ERROR_REVOKED_CERTIFICATE;
case CertStatus::Unknown:
return Result::ERROR_OCSP_UNKNOWN_CERT;
MOZILLA_PKIX_UNREACHABLE_DEFAULT_ENUM
}
}
// OCSPResponse ::= SEQUENCE {
// responseStatus OCSPResponseStatus,
// responseBytes [0] EXPLICIT ResponseBytes OPTIONAL }
//
static inline Result
OCSPResponse(Reader& input, Context& context)
{
// OCSPResponseStatus ::= ENUMERATED {
// successful (0), -- Response has valid confirmations
// malformedRequest (1), -- Illegal confirmation request
// internalError (2), -- Internal error in issuer
// tryLater (3), -- Try again later
// -- (4) is not used
// sigRequired (5), -- Must sign the request
// unauthorized (6) -- Request unauthorized
// }
uint8_t responseStatus;
Result rv = der::Enumerated(input, responseStatus);
if (rv != Success) {
return rv;
}
switch (responseStatus) {
case 0: break; // successful
case 1: return Result::ERROR_OCSP_MALFORMED_REQUEST;
case 2: return Result::ERROR_OCSP_SERVER_ERROR;
case 3: return Result::ERROR_OCSP_TRY_SERVER_LATER;
case 5: return Result::ERROR_OCSP_REQUEST_NEEDS_SIG;
case 6: return Result::ERROR_OCSP_UNAUTHORIZED_REQUEST;
default: return Result::ERROR_OCSP_UNKNOWN_RESPONSE_STATUS;
}
return der::Nested(input, der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 0,
der::SEQUENCE, [&context](Reader& r) {
return ResponseBytes(r, context);
});
}
// ResponseBytes ::= SEQUENCE {
// responseType OBJECT IDENTIFIER,
// response OCTET STRING }
static inline Result
ResponseBytes(Reader& input, Context& context)
{
static const uint8_t id_pkix_ocsp_basic[] = {
0x2B, 0x06, 0x01, 0x05, 0x05, 0x07, 0x30, 0x01, 0x01
};
Result rv = der::OID(input, id_pkix_ocsp_basic);
if (rv != Success) {
return rv;
}
return der::Nested(input, der::OCTET_STRING, der::SEQUENCE,
[&context](Reader& r) {
return BasicResponse(r, context);
});
}
// BasicOCSPResponse ::= SEQUENCE {
// tbsResponseData ResponseData,
// signatureAlgorithm AlgorithmIdentifier,
// signature BIT STRING,
// certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
Result
BasicResponse(Reader& input, Context& context)
{
Reader tbsResponseData;
der::SignedDataWithSignature signedData;
Result rv = der::SignedData(input, tbsResponseData, signedData);
if (rv != Success) {
if (rv == Result::ERROR_BAD_SIGNATURE) {
return Result::ERROR_OCSP_BAD_SIGNATURE;
}
return rv;
}
// Parse certificates, if any
NonOwningDERArray certs;
if (!input.AtEnd()) {
rv = der::Nested(input, der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 0,
der::SEQUENCE, [&certs](Reader& certsDER) -> Result {
while (!certsDER.AtEnd()) {
Input cert;
Result rv = der::ExpectTagAndGetTLV(certsDER, der::SEQUENCE, cert);
if (rv != Success) {
return rv;
}
rv = certs.Append(cert);
if (rv != Success) {
return Result::ERROR_BAD_DER; // Too many certs
}
}
return Success;
});
if (rv != Success) {
return rv;
}
}
return ResponseData(tbsResponseData, context, signedData, certs);
}
// ResponseData ::= SEQUENCE {
// version [0] EXPLICIT Version DEFAULT v1,
// responderID ResponderID,
// producedAt GeneralizedTime,
// responses SEQUENCE OF SingleResponse,
// responseExtensions [1] EXPLICIT Extensions OPTIONAL }
static inline Result
ResponseData(Reader& input, Context& context,
const der::SignedDataWithSignature& signedResponseData,
const DERArray& certs)
{
der::Version version;
Result rv = der::OptionalVersion(input, version);
if (rv != Success) {
return rv;
}
if (version != der::Version::v1) {
// TODO: more specific error code for bad version?
return Result::ERROR_BAD_DER;
}
// ResponderID ::= CHOICE {
// byName [1] Name,
// byKey [2] KeyHash }
Input responderID;
ResponderIDType responderIDType
= input.Peek(static_cast<uint8_t>(ResponderIDType::byName))
? ResponderIDType::byName
: ResponderIDType::byKey;
rv = der::ExpectTagAndGetValue(input, static_cast<uint8_t>(responderIDType),
responderID);
if (rv != Success) {
return rv;
}
// This is the soonest we can verify the signature. We verify the signature
// right away to follow the principal of minimizing the processing of data
// before verifying its signature.
rv = VerifySignature(context, responderIDType, responderID, certs,
signedResponseData);
if (rv != Success) {
return rv;
}
// TODO: Do we even need to parse this? Should we just skip it?
Time producedAt(Time::uninitialized);
rv = der::GeneralizedTime(input, producedAt);
if (rv != Success) {
return rv;
}
// We don't accept an empty sequence of responses. In practice, a legit OCSP
// responder will never return an empty response, and handling the case of an
// empty response makes things unnecessarily complicated.
rv = der::NestedOf(input, der::SEQUENCE, der::SEQUENCE,
der::EmptyAllowed::No, [&context](Reader& r) {
return SingleResponse(r, context);
});
if (rv != Success) {
return rv;
}
return der::OptionalExtensions(input,
der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 1,
ExtensionNotUnderstood);
}
// SingleResponse ::= SEQUENCE {
// certID CertID,
// certStatus CertStatus,
// thisUpdate GeneralizedTime,
// nextUpdate [0] EXPLICIT GeneralizedTime OPTIONAL,
// singleExtensions [1] EXPLICIT Extensions{{re-ocsp-crl |
// re-ocsp-archive-cutoff |
// CrlEntryExtensions, ...}
// } OPTIONAL }
static inline Result
SingleResponse(Reader& input, Context& context)
{
bool match = false;
Result rv = der::Nested(input, der::SEQUENCE, [&context, &match](Reader& r) {
return CertID(r, context, match);
});
if (rv != Success) {
return rv;
}
if (!match) {
// This response does not reference the certificate we're interested in.
// By consuming the rest of our input and returning successfully, we can
// continue processing and examine another response that might have what
// we want.
input.SkipToEnd();
return Success;
}
// We found a response for the cert we're interested in.
context.matchFound = true;
// CertStatus ::= CHOICE {
// good [0] IMPLICIT NULL,
// revoked [1] IMPLICIT RevokedInfo,
// unknown [2] IMPLICIT UnknownInfo }
//
// In the event of multiple SingleResponses for a cert that have conflicting
// statuses, we use the following precedence rules:
//
// * revoked overrides good and unknown
// * good overrides unknown
if (input.Peek(static_cast<uint8_t>(CertStatus::Good))) {
rv = der::ExpectTagAndEmptyValue(input,
static_cast<uint8_t>(CertStatus::Good));
if (rv != Success) {
return rv;
}
if (context.certStatus != CertStatus::Revoked) {
context.certStatus = CertStatus::Good;
}
} else if (input.Peek(static_cast<uint8_t>(CertStatus::Revoked))) {
// We don't need any info from the RevokedInfo structure, so we don't even
// parse it. TODO: We should mention issues like this in the explanation of
// why we treat invalid OCSP responses equivalently to revoked for OCSP
// stapling.
rv = der::ExpectTagAndSkipValue(input,
static_cast<uint8_t>(CertStatus::Revoked));
if (rv != Success) {
return rv;
}
context.certStatus = CertStatus::Revoked;
} else {
rv = der::ExpectTagAndEmptyValue(input,
static_cast<uint8_t>(CertStatus::Unknown));
if (rv != Success) {
return rv;
}
}
// http://tools.ietf.org/html/rfc6960#section-3.2
// 5. The time at which the status being indicated is known to be
// correct (thisUpdate) is sufficiently recent;
// 6. When available, the time at or before which newer information will
// be available about the status of the certificate (nextUpdate) is
// greater than the current time.
Time thisUpdate(Time::uninitialized);
rv = der::GeneralizedTime(input, thisUpdate);
if (rv != Success) {
return rv;
}
static const uint64_t SLOP_SECONDS = Time::ONE_DAY_IN_SECONDS;
Time timePlusSlop(context.time);
rv = timePlusSlop.AddSeconds(SLOP_SECONDS);
if (rv != Success) {
return rv;
}
if (thisUpdate > timePlusSlop) {
return Result::ERROR_OCSP_FUTURE_RESPONSE;
}
Time notAfter(Time::uninitialized);
static const uint8_t NEXT_UPDATE_TAG =
der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 0;
if (input.Peek(NEXT_UPDATE_TAG)) {
Time nextUpdate(Time::uninitialized);
rv = der::Nested(input, NEXT_UPDATE_TAG, [&nextUpdate](Reader& r) {
return der::GeneralizedTime(r, nextUpdate);
});
if (rv != Success) {
return rv;
}
if (nextUpdate < thisUpdate) {
return Result::ERROR_OCSP_MALFORMED_RESPONSE;
}
notAfter = thisUpdate;
if (notAfter.AddSeconds(context.maxLifetimeInDays *
Time::ONE_DAY_IN_SECONDS) != Success) {
// This could only happen if we're dealing with times beyond the year
// 10,000AD.
return Result::ERROR_OCSP_FUTURE_RESPONSE;
}
if (nextUpdate <= notAfter) {
notAfter = nextUpdate;
}
} else {
// NSS requires all OCSP responses without a nextUpdate to be recent.
// Match that stricter behavior.
notAfter = thisUpdate;
if (notAfter.AddSeconds(Time::ONE_DAY_IN_SECONDS) != Success) {
// This could only happen if we're dealing with times beyond the year
// 10,000AD.
return Result::ERROR_OCSP_FUTURE_RESPONSE;
}
}
// Add some slop to hopefully handle clock-skew.
Time notAfterPlusSlop(notAfter);
rv = notAfterPlusSlop.AddSeconds(SLOP_SECONDS);
if (rv != Success) {
// This could only happen if we're dealing with times beyond the year
// 10,000AD.
return Result::ERROR_OCSP_FUTURE_RESPONSE;
}
if (context.time > notAfterPlusSlop) {
context.expired = true;
}
rv = der::OptionalExtensions(input,
der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 1,
ExtensionNotUnderstood);
if (rv != Success) {
return rv;
}
if (context.thisUpdate) {
*context.thisUpdate = thisUpdate;
}
if (context.validThrough) {
*context.validThrough = notAfterPlusSlop;
}
return Success;
}
// CertID ::= SEQUENCE {
// hashAlgorithm AlgorithmIdentifier,
// issuerNameHash OCTET STRING, -- Hash of issuer's DN
// issuerKeyHash OCTET STRING, -- Hash of issuer's public key
// serialNumber CertificateSerialNumber }
static inline Result
CertID(Reader& input, const Context& context, /*out*/ bool& match)
{
match = false;
DigestAlgorithm hashAlgorithm;
Result rv = der::DigestAlgorithmIdentifier(input, hashAlgorithm);
if (rv != Success) {
if (rv == Result::ERROR_INVALID_ALGORITHM) {
// Skip entries that are hashed with algorithms we don't support.
input.SkipToEnd();
return Success;
}
return rv;
}
Input issuerNameHash;
rv = der::ExpectTagAndGetValue(input, der::OCTET_STRING, issuerNameHash);
if (rv != Success) {
return rv;
}
Input issuerKeyHash;
rv = der::ExpectTagAndGetValue(input, der::OCTET_STRING, issuerKeyHash);
if (rv != Success) {
return rv;
}
Input serialNumber;
rv = der::CertificateSerialNumber(input, serialNumber);
if (rv != Success) {
return rv;
}
if (!InputsAreEqual(serialNumber, context.certID.serialNumber)) {
// This does not reference the certificate we're interested in.
// Consume the rest of the input and return successfully to
// potentially continue processing other responses.
input.SkipToEnd();
return Success;
}
// TODO: support SHA-2 hashes.
if (hashAlgorithm != DigestAlgorithm::sha1) {
// Again, not interested in this response. Consume input, return success.
input.SkipToEnd();
return Success;
}
if (issuerNameHash.GetLength() != SHA1_DIGEST_LENGTH) {
return Result::ERROR_OCSP_MALFORMED_RESPONSE;
}
// From http://tools.ietf.org/html/rfc6960#section-4.1.1:
// "The hash shall be calculated over the DER encoding of the
// issuer's name field in the certificate being checked."
uint8_t hashBuf[SHA1_DIGEST_LENGTH];
rv = context.trustDomain.DigestBuf(context.certID.issuer,
DigestAlgorithm::sha1, hashBuf,
sizeof(hashBuf));
if (rv != Success) {
return rv;
}
Input computed(hashBuf);
if (!InputsAreEqual(computed, issuerNameHash)) {
// Again, not interested in this response. Consume input, return success.
input.SkipToEnd();
return Success;
}
return MatchKeyHash(context.trustDomain, issuerKeyHash,
context.certID.issuerSubjectPublicKeyInfo, match);
}
// From http://tools.ietf.org/html/rfc6960#section-4.1.1:
// "The hash shall be calculated over the value (excluding tag and length) of
// the subject public key field in the issuer's certificate."
//
// From http://tools.ietf.org/html/rfc6960#appendix-B.1:
// KeyHash ::= OCTET STRING -- SHA-1 hash of responder's public key
// -- (i.e., the SHA-1 hash of the value of the
// -- BIT STRING subjectPublicKey [excluding
// -- the tag, length, and number of unused
// -- bits] in the responder's certificate)
static Result
MatchKeyHash(TrustDomain& trustDomain, Input keyHash,
const Input subjectPublicKeyInfo, /*out*/ bool& match)
{
if (keyHash.GetLength() != SHA1_DIGEST_LENGTH) {
return Result::ERROR_OCSP_MALFORMED_RESPONSE;
}
static uint8_t hashBuf[SHA1_DIGEST_LENGTH];
Result rv = KeyHash(trustDomain, subjectPublicKeyInfo, hashBuf,
sizeof hashBuf);
if (rv != Success) {
return rv;
}
Input computed(hashBuf);
match = InputsAreEqual(computed, keyHash);
return Success;
}
// TODO(bug 966856): support SHA-2 hashes
Result
KeyHash(TrustDomain& trustDomain, const Input subjectPublicKeyInfo,
/*out*/ uint8_t* hashBuf, size_t hashBufSize)
{
if (!hashBuf || hashBufSize != SHA1_DIGEST_LENGTH) {
return Result::FATAL_ERROR_LIBRARY_FAILURE;
}
// RFC 5280 Section 4.1
//
// SubjectPublicKeyInfo ::= SEQUENCE {
// algorithm AlgorithmIdentifier,
// subjectPublicKey BIT STRING }
Reader spki;
Result rv = der::ExpectTagAndGetValueAtEnd(subjectPublicKeyInfo,
der::SEQUENCE, spki);
if (rv != Success) {
return rv;
}
// Skip AlgorithmIdentifier
rv = der::ExpectTagAndSkipValue(spki, der::SEQUENCE);
if (rv != Success) {
return rv;
}
Input subjectPublicKey;
rv = der::BitStringWithNoUnusedBits(spki, subjectPublicKey);
if (rv != Success) {
return rv;
}
rv = der::End(spki);
if (rv != Success) {
return rv;
}
return trustDomain.DigestBuf(subjectPublicKey, DigestAlgorithm::sha1,
hashBuf, hashBufSize);
}
Result
ExtensionNotUnderstood(Reader& /*extnID*/, Input /*extnValue*/,
bool /*critical*/, /*out*/ bool& understood)
{
understood = false;
return Success;
}
// 1. The certificate identified in a received response corresponds to
// the certificate that was identified in the corresponding request;
// 2. The signature on the response is valid;
// 3. The identity of the signer matches the intended recipient of the
// request;
// 4. The signer is currently authorized to provide a response for the
// certificate in question;
// 5. The time at which the status being indicated is known to be
// correct (thisUpdate) is sufficiently recent;
// 6. When available, the time at or before which newer information will
// be available about the status of the certificate (nextUpdate) is
// greater than the current time.
//
// Responses whose nextUpdate value is earlier than
// the local system time value SHOULD be considered unreliable.
// Responses whose thisUpdate time is later than the local system time
// SHOULD be considered unreliable.
//
// If nextUpdate is not set, the responder is indicating that newer
// revocation information is available all the time.
//
// http://tools.ietf.org/html/rfc5019#section-4
Result
CreateEncodedOCSPRequest(TrustDomain& trustDomain, const struct CertID& certID,
/*out*/ uint8_t (&out)[OCSP_REQUEST_MAX_LENGTH],
/*out*/ size_t& outLen)
{
// We do not add any extensions to the request.
// RFC 6960 says "An OCSP client MAY wish to specify the kinds of response
// types it understands. To do so, it SHOULD use an extension with the OID
// id-pkix-ocsp-response." This use of MAY and SHOULD is unclear. MSIE11
// on Windows 8.1 does not include any extensions, whereas NSS has always
// included the id-pkix-ocsp-response extension. Avoiding the sending the
// extension is better for OCSP GET because it makes the request smaller,
// and thus more likely to fit within the 255 byte limit for OCSP GET that
// is specified in RFC 5019 Section 5.
// Bug 966856: Add the id-pkix-ocsp-pref-sig-algs extension.
// Since we don't know whether the OCSP responder supports anything other
// than SHA-1, we have no choice but to use SHA-1 for issuerNameHash and
// issuerKeyHash.
static const uint8_t hashAlgorithm[11] = {
0x30, 0x09, // SEQUENCE
0x06, 0x05, 0x2B, 0x0E, 0x03, 0x02, 0x1A, // OBJECT IDENTIFIER id-sha1
0x05, 0x00, // NULL
};
static const uint8_t hashLen = 160 / 8;
static const unsigned int totalLenWithoutSerialNumberData
= 2 // OCSPRequest
+ 2 // tbsRequest
+ 2 // requestList
+ 2 // Request
+ 2 // reqCert (CertID)
+ sizeof(hashAlgorithm) // hashAlgorithm
+ 2 + hashLen // issuerNameHash
+ 2 + hashLen // issuerKeyHash
+ 2; // serialNumber (header)
// The only way we could have a request this large is if the serialNumber was
// ridiculously and unreasonably large. RFC 5280 says "Conforming CAs MUST
// NOT use serialNumber values longer than 20 octets." With this restriction,
// we allow for some amount of non-conformance with that requirement while
// still ensuring we can encode the length values in the ASN.1 TLV structures
// in a single byte.
static_assert(totalLenWithoutSerialNumberData < OCSP_REQUEST_MAX_LENGTH,
"totalLenWithoutSerialNumberData too big");
if (certID.serialNumber.GetLength() >
OCSP_REQUEST_MAX_LENGTH - totalLenWithoutSerialNumberData) {
return Result::ERROR_BAD_DER;
}
outLen = totalLenWithoutSerialNumberData + certID.serialNumber.GetLength();
uint8_t totalLen = static_cast<uint8_t>(outLen);
uint8_t* d = out;
*d++ = 0x30; *d++ = totalLen - 2u; // OCSPRequest (SEQUENCE)
*d++ = 0x30; *d++ = totalLen - 4u; // tbsRequest (SEQUENCE)
*d++ = 0x30; *d++ = totalLen - 6u; // requestList (SEQUENCE OF)
*d++ = 0x30; *d++ = totalLen - 8u; // Request (SEQUENCE)
*d++ = 0x30; *d++ = totalLen - 10u; // reqCert (CertID SEQUENCE)
// reqCert.hashAlgorithm
for (size_t i = 0; i < sizeof(hashAlgorithm); ++i) {
*d++ = hashAlgorithm[i];
}
// reqCert.issuerNameHash (OCTET STRING)
*d++ = 0x04;
*d++ = hashLen;
Result rv = trustDomain.DigestBuf(certID.issuer, DigestAlgorithm::sha1, d,
hashLen);
if (rv != Success) {
return rv;
}
d += hashLen;
// reqCert.issuerKeyHash (OCTET STRING)
*d++ = 0x04;
*d++ = hashLen;
rv = KeyHash(trustDomain, certID.issuerSubjectPublicKeyInfo, d, hashLen);
if (rv != Success) {
return rv;
}
d += hashLen;
// reqCert.serialNumber (INTEGER)
*d++ = 0x02; // INTEGER
*d++ = static_cast<uint8_t>(certID.serialNumber.GetLength());
Reader serialNumber(certID.serialNumber);
do {
rv = serialNumber.Read(*d);
if (rv != Success) {
return rv;
}
++d;
} while (!serialNumber.AtEnd());
assert(d == out + totalLen);
return Success;
}
} } // namespace mozilla::pkix
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