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// Copyright 2018 The Chromium Authors. All rights reserved.
// Copyright (C) 2019-2021 Apple Inc. All rights reserved.
//
// 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 Google Inc. 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
// OWNER 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.
#include "config.h"
#include "U2fResponseConverter.h"
#if ENABLE(WEB_AUTHN)
#include "CommonCryptoDERUtilities.h"
#include "FidoConstants.h"
#include "WebAuthenticationConstants.h"
#include "WebAuthenticationUtils.h"
namespace fido {
using namespace WebCore;
namespace {
// In a U2F registration response, the key is in X9.62 format:
// - a constant 0x04 prefix to indicate an uncompressed key
// - the 32-byte x coordinate
// - the 32-byte y coordinate.
const uint8_t uncompressedKey = 0x04;
// https://www.w3.org/TR/webauthn/#flags
const uint8_t makeCredentialFlags = 0b01000001; // UP and AT are set.
// https://fidoalliance.org/specs/fido-u2f-v1.2-ps-20170411/fido-u2f-raw-message-formats-v1.2-ps-20170411.html#authentication-response-message-success
const size_t flagIndex = 0;
const size_t counterIndex = 1;
const size_t signatureIndex = 5;
static Vector<uint8_t> extractECPublicKeyFromU2fRegistrationResponse(const Vector<uint8_t>& u2fData)
{
size_t pos = kReservedLength;
if (u2fData.size() <= pos || u2fData[pos] != uncompressedKey)
return { };
pos++;
if (u2fData.size() < pos + 2 * ES256FieldElementLength)
return { };
Vector<uint8_t> x { u2fData.data() + pos, ES256FieldElementLength };
pos += ES256FieldElementLength;
Vector<uint8_t> y { u2fData.data() + pos, ES256FieldElementLength };
return encodeES256PublicKeyAsCBOR(WTFMove(x), WTFMove(y));
}
static Vector<uint8_t> extractCredentialIdFromU2fRegistrationResponse(const Vector<uint8_t>& u2fData)
{
size_t pos = kU2fKeyHandleLengthOffset;
if (u2fData.size() <= pos)
return { };
size_t credentialIdLength = u2fData[pos];
pos++;
if (u2fData.size() < pos + credentialIdLength)
return { };
return { u2fData.data() + pos, credentialIdLength };
}
static Vector<uint8_t> createAttestedCredentialDataFromU2fRegisterResponse(const Vector<uint8_t>& u2fData, const Vector<uint8_t>& publicKey)
{
auto credentialId = extractCredentialIdFromU2fRegistrationResponse(u2fData);
if (credentialId.isEmpty())
return { };
return buildAttestedCredentialData(Vector<uint8_t>(aaguidLength, 0), credentialId, publicKey);
}
static size_t parseX509Length(const Vector<uint8_t>& u2fData, size_t offset)
{
if (u2fData.size() <= offset || u2fData[offset] != SequenceMark)
return 0;
offset++;
if (u2fData.size() <= offset)
return 0;
const auto sequenceLengthLength = bytesUsedToEncodedLength(u2fData[offset]);
if (sequenceLengthLength > sizeof(size_t) || (u2fData.size() < offset + sequenceLengthLength))
return 0;
size_t sequenceLength = sequenceLengthLength == 1 ? u2fData[offset] : 0;
offset++;
for (auto i = sequenceLengthLength - 1; i; i--, offset++)
sequenceLength += u2fData[offset] << (i - 1) * 8;
return sequenceLength + sequenceLengthLength + sizeof(SequenceMark);
}
static cbor::CBORValue::MapValue createFidoAttestationStatementFromU2fRegisterResponse(const Vector<uint8_t>& u2fData, size_t offset)
{
auto x509Length = parseX509Length(u2fData, offset);
if (!x509Length || u2fData.size() < offset + x509Length)
return { };
Vector<uint8_t> x509 { u2fData.data() + offset, x509Length };
offset += x509Length;
Vector<uint8_t> signature { u2fData.data() + offset, u2fData.size() - offset };
if (signature.isEmpty())
return { };
cbor::CBORValue::MapValue attestationStatementMap;
attestationStatementMap[cbor::CBORValue("sig")] = cbor::CBORValue(WTFMove(signature));
Vector<cbor::CBORValue> cborArray;
cborArray.append(cbor::CBORValue(WTFMove(x509)));
attestationStatementMap[cbor::CBORValue("x5c")] = cbor::CBORValue(WTFMove(cborArray));
return attestationStatementMap;
}
} // namespace
RefPtr<AuthenticatorAttestationResponse> readU2fRegisterResponse(const String& rpId, const Vector<uint8_t>& u2fData, AuthenticatorAttachment attachment, Vector<AuthenticatorTransport>&& transports, const AttestationConveyancePreference& attestation)
{
auto publicKey = extractECPublicKeyFromU2fRegistrationResponse(u2fData);
if (publicKey.isEmpty())
return nullptr;
auto attestedCredentialData = createAttestedCredentialDataFromU2fRegisterResponse(u2fData, publicKey);
if (attestedCredentialData.isEmpty())
return nullptr;
// Extract the credentialId for packing into the response data.
auto credentialId = extractCredentialIdFromU2fRegistrationResponse(u2fData);
ASSERT(!credentialId.isEmpty());
// The counter is zeroed out for Register requests.
auto authData = buildAuthData(rpId, makeCredentialFlags, 0, attestedCredentialData);
auto fidoAttestationStatement = createFidoAttestationStatementFromU2fRegisterResponse(u2fData, kU2fKeyHandleOffset + credentialId.size());
if (fidoAttestationStatement.empty())
return nullptr;
auto attestationObject = buildAttestationObject(WTFMove(authData), "fido-u2f"_s, WTFMove(fidoAttestationStatement), attestation);
return AuthenticatorAttestationResponse::create(credentialId, attestationObject, attachment, WTFMove(transports));
}
RefPtr<AuthenticatorAssertionResponse> readU2fSignResponse(const String& rpId, const WebCore::BufferSource& keyHandle, const Vector<uint8_t>& u2fData, AuthenticatorAttachment attachment)
{
if (!keyHandle.length() || u2fData.size() <= signatureIndex)
return nullptr;
// 1 byte flags, 4 bytes counter
auto flags = u2fData[flagIndex];
uint32_t counter = u2fData[counterIndex] << 24;
counter += u2fData[counterIndex + 1] << 16;
counter += u2fData[counterIndex + 2] << 8;
counter += u2fData[counterIndex + 3];
auto authData = buildAuthData(rpId, flags, counter, { });
// FIXME: Find a way to remove the need of constructing a vector here.
Vector<uint8_t> signature { u2fData.data() + signatureIndex, u2fData.size() - signatureIndex };
Vector<uint8_t> keyHandleVector { keyHandle.data(), keyHandle.length() };
return AuthenticatorAssertionResponse::create(keyHandleVector, authData, signature, { }, attachment);
}
} // namespace fido
#endif // ENABLE(WEB_AUTHN)
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