// BasicOCSPResponse ::= SEQUENCE {
// tbsResponseData ResponseData,
// signatureAlgorithm AlgorithmIdentifier,
// signature BIT STRING,
// certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
Result
BasicResponse(Reader& input, Context& context)
{
Reader tbsResponseData;
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()) {
// We ignore the lengths of the wrappers because we'll detect bad lengths
// during parsing--too short and we'll run out of input for parsing a cert,
// and too long and we'll have leftover data that won't parse as a cert.
// [0] wrapper
Reader wrapped;
rv = der::ExpectTagAndGetValue(
input, der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 0, wrapped);
if (rv != Success) {
return rv;
}
rv = der::End(input);
if (rv != Success) {
return rv;
}
// SEQUENCE wrapper
Reader certsSequence;
rv = der::ExpectTagAndGetValue(wrapped, der::SEQUENCE, certsSequence);
if (rv != Success) {
return rv;
}
rv = der::End(wrapped);
if (rv != Success) {
return rv;
}
// sequence of certificates
while (!certsSequence.AtEnd()) {
Input cert;
rv = der::ExpectTagAndGetTLV(certsSequence, der::SEQUENCE, cert);
if (rv != Success) {
return rv;
}
rv = certs.Append(cert);
if (rv != Success) {
return rv;
}
}
}
return ResponseData(tbsResponseData, context, signedData, certs);
}
// Recursively build the path from the given subject certificate to the root.
//
// Be very careful about changing the order of checks. The order is significant
// because it affects which error we return when a certificate or certificate
// chain has multiple problems. See the error ranking documentation in
// pkix/pkix.h.
static Result
BuildForward(TrustDomain& trustDomain,
const BackCert& subject,
Time time,
KeyUsage requiredKeyUsageIfPresent,
KeyPurposeId requiredEKUIfPresent,
const CertPolicyId& requiredPolicy,
/*optional*/ const Input* stapledOCSPResponse,
unsigned int subCACount)
{
Result rv;
TrustLevel trustLevel;
// If this is an end-entity and not a trust anchor, we defer reporting
// any error found here until after attempting to find a valid chain.
// See the explanation of error prioritization in pkix.h.
rv = CheckIssuerIndependentProperties(trustDomain, subject, time,
requiredKeyUsageIfPresent,
requiredEKUIfPresent, requiredPolicy,
subCACount, trustLevel);
Result deferredEndEntityError = Success;
if (rv != Success) {
if (subject.endEntityOrCA == EndEntityOrCA::MustBeEndEntity &&
trustLevel != TrustLevel::TrustAnchor) {
deferredEndEntityError = rv;
} else {
return rv;
}
}
if (trustLevel == TrustLevel::TrustAnchor) {
// End of the recursion.
NonOwningDERArray chain;
for (const BackCert* cert = &subject; cert; cert = cert->childCert) {
rv = chain.Append(cert->GetDER());
if (rv != Success) {
return NotReached("NonOwningDERArray::SetItem failed.", rv);
}
}
// This must be done here, after the chain is built but before any
// revocation checks have been done.
return trustDomain.IsChainValid(chain, time);
}
if (subject.endEntityOrCA == EndEntityOrCA::MustBeCA) {
// Avoid stack overflows and poor performance by limiting cert chain
// length.
static const unsigned int MAX_SUBCA_COUNT = 6;
static_assert(1/*end-entity*/ + MAX_SUBCA_COUNT + 1/*root*/ ==
NonOwningDERArray::MAX_LENGTH,
"MAX_SUBCA_COUNT and NonOwningDERArray::MAX_LENGTH mismatch.");
if (subCACount >= MAX_SUBCA_COUNT) {
return Result::ERROR_UNKNOWN_ISSUER;
}
++subCACount;
} else {
assert(subCACount == 0);
}
// Find a trusted issuer.
PathBuildingStep pathBuilder(trustDomain, subject, time,
requiredEKUIfPresent, requiredPolicy,
stapledOCSPResponse, subCACount);
// TODO(bug 965136): Add SKI/AKI matching optimizations
rv = trustDomain.FindIssuer(subject.GetIssuer(), pathBuilder, time);
if (rv != Success) {
return rv;
}
rv = pathBuilder.CheckResult();
if (rv != Success) {
return rv;
}
// If we found a valid chain but deferred reporting an error with the
// end-entity certificate, report it now.
if (deferredEndEntityError != Success) {
return deferredEndEntityError;
}
// We've built a valid chain from the subject cert up to a trusted root.
return Success;
}