// Extension ::= SEQUENCE {
// extnID OBJECT IDENTIFIER,
// critical BOOLEAN DEFAULT FALSE,
// extnValue OCTET STRING
// }
static der::Result
CheckExtensionForCriticality(der::Input& input)
{
uint16_t toSkip;
if (ExpectTagAndGetLength(input, der::OIDTag, toSkip) != der::Success) {
return der::Failure;
}
// TODO: maybe we should check the syntax of the OID value
if (input.Skip(toSkip) != der::Success) {
return der::Failure;
}
// The only valid explicit encoding of the value is TRUE, so don't even
// bother parsing it, since we're going to fail either way.
if (input.Peek(der::BOOLEAN)) {
return der::Fail(SEC_ERROR_UNKNOWN_CRITICAL_EXTENSION);
}
if (ExpectTagAndGetLength(input, der::OCTET_STRING, toSkip)
!= der::Success) {
return der::Failure;
}
return input.Skip(toSkip);
}
// ResponseData ::= SEQUENCE {
// version [0] EXPLICIT Version DEFAULT v1,
// responderID ResponderID,
// producedAt GeneralizedTime,
// responses SEQUENCE OF SingleResponse,
// responseExtensions [1] EXPLICIT Extensions OPTIONAL }
static inline der::Result
ResponseData(der::Input& input, Context& context,
const CERTSignedData& signedResponseData,
/*const*/ SECItem* certs, size_t numCerts)
{
uint8_t version;
if (der::OptionalVersion(input, version) != der::Success) {
return der::Failure;
}
if (version != der::v1) {
// TODO: more specific error code for bad version?
return der::Fail(SEC_ERROR_BAD_DER);
}
// ResponderID ::= CHOICE {
// byName [1] Name,
// byKey [2] KeyHash }
SECItem responderID;
uint16_t responderIDLength;
ResponderIDType responderIDType
= input.Peek(static_cast<uint8_t>(ResponderIDType::byName))
? ResponderIDType::byName
: ResponderIDType::byKey;
if (ExpectTagAndGetLength(input, static_cast<uint8_t>(responderIDType),
responderIDLength) != der::Success) {
return der::Failure;
}
// TODO: responderID probably needs to have another level of ASN1 tag/length
// checked and stripped.
if (input.Skip(responderIDLength, responderID) != der::Success) {
return der::Failure;
}
// 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.
if (VerifySignature(context, responderIDType, responderID, certs, numCerts,
signedResponseData) != SECSuccess) {
return der::Failure;
}
// TODO: Do we even need to parse this? Should we just skip it?
PRTime producedAt;
if (der::GeneralizedTime(input, producedAt) != der::Success) {
return der::Failure;
}
// 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.
if (der::NestedOf(input, der::SEQUENCE, der::SEQUENCE,
der::MustNotBeEmpty,
bind(SingleResponse, _1, ref(context))) != der::Success) {
return der::Failure;
}
if (!input.AtEnd()) {
if (CheckExtensionsForCriticality(input) != der::Success) {
return der::Failure;
}
}
return der::Success;
}
// BasicOCSPResponse ::= SEQUENCE {
// tbsResponseData ResponseData,
// signatureAlgorithm AlgorithmIdentifier,
// signature BIT STRING,
// certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
der::Result
BasicResponse(der::Input& input, Context& context)
{
der::Input::Mark mark(input.GetMark());
uint16_t length;
if (der::ExpectTagAndGetLength(input, der::SEQUENCE, length)
!= der::Success) {
return der::Failure;
}
// The signature covers the entire DER encoding of tbsResponseData, including
// the beginning tag and length. However, when we're parsing tbsResponseData,
// we want to strip off the tag and length because we don't need it after
// we've confirmed it's there and figured out what length it is.
der::Input tbsResponseData;
if (input.Skip(length, tbsResponseData) != der::Success) {
return der::Failure;
}
CERTSignedData signedData;
input.GetSECItem(siBuffer, mark, signedData.data);
if (der::Nested(input, der::SEQUENCE,
bind(der::AlgorithmIdentifier, _1,
ref(signedData.signatureAlgorithm))) != der::Success) {
return der::Failure;
}
if (der::Skip(input, der::BIT_STRING, signedData.signature) != der::Success) {
return der::Failure;
}
if (signedData.signature.len == 0) {
return der::Fail(SEC_ERROR_OCSP_BAD_SIGNATURE);
}
unsigned int unusedBitsAtEnd = signedData.signature.data[0];
// XXX: Really the constraint should be that unusedBitsAtEnd must be less
// than 7. But, we suspect there are no valid OCSP response signatures with
// non-zero unused bits. It seems like NSS assumes this in various places, so
// we enforce it. If we find compatibility issues, we'll know we're wrong.
if (unusedBitsAtEnd != 0) {
return der::Fail(SEC_ERROR_OCSP_BAD_SIGNATURE);
}
++signedData.signature.data;
--signedData.signature.len;
signedData.signature.len = (signedData.signature.len << 3); // Bytes to bits
// Parse certificates, if any
SECItem certs[8];
size_t numCerts = 0;
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
if (der::ExpectTagAndIgnoreLength(
input, der::CONSTRUCTED | der::CONTEXT_SPECIFIC | 0)
!= der::Success) {
return der::Failure;
}
// SEQUENCE wrapper
if (der::ExpectTagAndIgnoreLength(input, der::SEQUENCE) != der::Success) {
return der::Failure;
}
// sequence of certificates
while (!input.AtEnd()) {
if (numCerts == PR_ARRAY_SIZE(certs)) {
return der::Fail(SEC_ERROR_BAD_DER);
}
// Unwrap the SEQUENCE that contains the certificate, which is itself a
// SEQUENCE.
der::Input::Mark mark(input.GetMark());
if (der::Skip(input, der::SEQUENCE) != der::Success) {
return der::Failure;
}
input.GetSECItem(siBuffer, mark, certs[numCerts]);
++numCerts;
}
}
return ResponseData(tbsResponseData, context, signedData, certs, numCerts);
}