/*
 * Copyright (C) 2017 Apple Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions
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 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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#include "config.h"
#include "CryptoAlgorithmECDSA.h"

#if ENABLE(SUBTLE_CRYPTO)

#include "CommonCryptoDERUtilities.h"
#include "CommonCryptoUtilities.h"
#include "CryptoAlgorithmEcdsaParams.h"
#include "CryptoDigestAlgorithm.h"
#include "CryptoKeyEC.h"

namespace WebCore {

static ExceptionOr<Vector<uint8_t>> signECDSA(CryptoAlgorithmIdentifier hash, const PlatformECKey key, size_t keyLengthInBytes, const Vector<uint8_t>& data)
{
    CCDigestAlgorithm digestAlgorithm;
    if (!getCommonCryptoDigestAlgorithm(hash, digestAlgorithm))
        return Exception { OperationError };

    auto cryptoDigestAlgorithm = WebCore::cryptoDigestAlgorithm(hash);
    if (!cryptoDigestAlgorithm)
        return Exception { OperationError };
    auto digest = PAL::CryptoDigest::create(*cryptoDigestAlgorithm);
    if (!digest)
        return Exception { OperationError };
    digest->addBytes(data.data(), data.size());
    auto digestData = digest->computeHash();

    // The signature produced by CCECCryptorSignHash is in DER format.
    // tag + length(1) + tag + length(1) + InitialOctet(?) + keyLength in bytes + tag + length(1) + InitialOctet(?) + keyLength in bytes
    Vector<uint8_t> signature(8 + keyLengthInBytes * 2);
    size_t signatureSize = signature.size();

    CCCryptorStatus status = CCECCryptorSignHash(key, digestData.data(), digestData.size(), signature.data(), &signatureSize);
    if (status)
        return Exception { OperationError };

    // FIXME: <rdar://problem/31618371>
    // convert the DER binary into r + s
    Vector<uint8_t> newSignature;
    newSignature.reserveCapacity(keyLengthInBytes * 2);
    size_t offset = 3; // skip tag, length, tag

    // If r < keyLengthInBytes, fill the head of r with 0s.
    size_t bytesToCopy = keyLengthInBytes;
    if (signature[offset] < keyLengthInBytes) {
        newSignature.resize(keyLengthInBytes - signature[offset]);
        memset(newSignature.data(), InitialOctet, keyLengthInBytes - signature[offset]);
        bytesToCopy = signature[offset];
    } else if (signature[offset] > keyLengthInBytes) // Otherwise skip the leading 0s of r.
        offset += signature[offset] - keyLengthInBytes;
    offset++; // skip length
    ASSERT_WITH_SECURITY_IMPLICATION(signature.size() > offset + bytesToCopy);
    newSignature.append(signature.data() + offset, bytesToCopy);
    offset += bytesToCopy + 1; // skip r, tag

    // If s < keyLengthInBytes, fill the head of s with 0s.
    bytesToCopy = keyLengthInBytes;
    if (signature[offset] < keyLengthInBytes) {
        size_t pos = newSignature.size();
        newSignature.resize(pos + keyLengthInBytes - signature[offset]);
        memset(newSignature.data() + pos, InitialOctet, keyLengthInBytes - signature[offset]);
        bytesToCopy = signature[offset];
    } else if (signature[offset] > keyLengthInBytes) // Otherwise skip the leading 0s of s.
        offset += signature[offset] - keyLengthInBytes;
    offset++; // skip length
    ASSERT_WITH_SECURITY_IMPLICATION(signature.size() >= offset + bytesToCopy);
    newSignature.append(signature.data() + offset, bytesToCopy);

    return WTFMove(newSignature);
}

static ExceptionOr<bool> verifyECDSA(CryptoAlgorithmIdentifier hash, const PlatformECKey key, size_t keyLengthInBytes, const Vector<uint8_t>& signature, const Vector<uint8_t> data)
{
    CCDigestAlgorithm digestAlgorithm;
    if (!getCommonCryptoDigestAlgorithm(hash, digestAlgorithm))
        return Exception { OperationError };

    auto cryptoDigestAlgorithm = WebCore::cryptoDigestAlgorithm(hash);
    if (!cryptoDigestAlgorithm)
        return Exception { OperationError };
    auto digest = PAL::CryptoDigest::create(*cryptoDigestAlgorithm);
    if (!digest)
        return Exception { OperationError };
    digest->addBytes(data.data(), data.size());
    auto digestData = digest->computeHash();

    if (signature.size() != keyLengthInBytes * 2)
        return false;

    // FIXME: <rdar://problem/31618371>
    // Convert the signature into DER format.
    // tag + length(1) + tag + length(1) + InitialOctet(?) + r + tag + length(1) + InitialOctet(?) + s
    // Skip any heading 0s of r and s.
    size_t rStart = 0;
    while (rStart < keyLengthInBytes && !signature[rStart])
        rStart++;
    size_t sStart = keyLengthInBytes;
    while (rStart < signature.size() && !signature[sStart])
        sStart++;

    // InitialOctet is needed when the first byte of r/s is larger than or equal to 128.
    bool rNeedsInitialOctet = signature[rStart] >= 128;
    bool sNeedsInitialOctet = signature[sStart] >= 128;

    // Construct the DER signature.
    Vector<uint8_t> newSignature;
    newSignature.reserveCapacity(6 + keyLengthInBytes * 3  + rNeedsInitialOctet + sNeedsInitialOctet - rStart - sStart);
    newSignature.append(SequenceMark);
    addEncodedASN1Length(newSignature, 4 + keyLengthInBytes * 3  + rNeedsInitialOctet + sNeedsInitialOctet - rStart - sStart);
    newSignature.append(IntegerMark);
    addEncodedASN1Length(newSignature, keyLengthInBytes + rNeedsInitialOctet - rStart);
    if (rNeedsInitialOctet)
        newSignature.append(InitialOctet);
    newSignature.append(signature.data() + rStart, keyLengthInBytes - rStart);
    newSignature.append(IntegerMark);
    addEncodedASN1Length(newSignature, keyLengthInBytes * 2 + sNeedsInitialOctet - sStart);
    if (sNeedsInitialOctet)
        newSignature.append(InitialOctet);
    newSignature.append(signature.data() + sStart, keyLengthInBytes * 2 - sStart);

    uint32_t valid;
    CCCryptorStatus status = CCECCryptorVerifyHash(key, digestData.data(), digestData.size(), newSignature.data(), newSignature.size(), &valid);
    if (status)
        return Exception { OperationError };
    return valid;
}

ExceptionOr<Vector<uint8_t>> CryptoAlgorithmECDSA::platformSign(const CryptoAlgorithmEcdsaParams& parameters, const CryptoKeyEC& key, const Vector<uint8_t>& data)
{
    return signECDSA(parameters.hashIdentifier, key.platformKey(), key.keySizeInBits() / 8, data);
}

ExceptionOr<bool> CryptoAlgorithmECDSA::platformVerify(const CryptoAlgorithmEcdsaParams& parameters, const CryptoKeyEC& key, const Vector<uint8_t>& signature, const Vector<uint8_t>& data)
{
    return verifyECDSA(parameters.hashIdentifier, key.platformKey(), key.keySizeInBits() / 8, signature, data);
}

} // namespace WebCore

#endif // ENABLE(SUBTLE_CRYPTO)