Source/WebCore/crypto/gcrypt/CryptoAlgorithmRSA_PSSGCrypt.cpp

/*
 * Copyright (C) 2017 Apple Inc. All rights reserved.
 * Copyright (C) 2017 Metrological Group B.V.
 * Copyright (C) 2017 Igalia S.L.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
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 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * 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 "CryptoAlgorithmRSA_PSS.h"

#if ENABLE(WEB_CRYPTO)

#include "CryptoAlgorithmRsaPssParams.h"
#include "CryptoKeyRSA.h"
#include "GCryptUtilities.h"

namespace WebCore {

static Optional<Vector<uint8_t>> gcryptSign(gcry_sexp_t keySexp, const Vector<uint8_t>& data, CryptoAlgorithmIdentifier hashAlgorithmIdentifier, size_t saltLength, size_t keySizeInBytes)
{
    // Perform digest operation with the specified algorithm on the given data.
    Vector<uint8_t> dataHash;
    {
        auto digestAlgorithm = hashCryptoDigestAlgorithm(hashAlgorithmIdentifier);
        if (!digestAlgorithm)
            return WTF::nullopt;

        auto digest = PAL::CryptoDigest::create(*digestAlgorithm);
        if (!digest)
            return WTF::nullopt;

        digest->addBytes(data.data(), data.size());
        dataHash = digest->computeHash();
    }

    // Construct the `data` s-expression that contains PSS-padded hashed data.
    PAL::GCrypt::Handle<gcry_sexp_t> dataSexp;
    {
        auto shaAlgorithm = hashAlgorithmName(hashAlgorithmIdentifier);
        if (!shaAlgorithm)
            return WTF::nullopt;

        gcry_error_t error = gcry_sexp_build(&dataSexp, nullptr, "(data(flags pss)(salt-length %u)(hash %s %b))",
            saltLength, *shaAlgorithm, dataHash.size(), dataHash.data());
        if (error != GPG_ERR_NO_ERROR) {
            PAL::GCrypt::logError(error);
            return WTF::nullopt;
        }
    }

    // Perform the PK signing, retrieving a `sig-val` s-expression of the following form:
    // (sig-val
    //   (rsa
    //     (s s-mpi)))
    PAL::GCrypt::Handle<gcry_sexp_t> signatureSexp;
    gcry_error_t error = gcry_pk_sign(&signatureSexp, dataSexp, keySexp);
    if (error != GPG_ERR_NO_ERROR) {
        PAL::GCrypt::logError(error);
        return WTF::nullopt;
    }

    // Retrieve MPI data of the embedded `s` integer.
    PAL::GCrypt::Handle<gcry_sexp_t> sSexp(gcry_sexp_find_token(signatureSexp, "s", 0));
    if (!sSexp)
        return WTF::nullopt;

    return mpiZeroPrefixedData(sSexp, keySizeInBytes);
}

static Optional<bool> gcryptVerify(gcry_sexp_t keySexp, const Vector<uint8_t>& signature, const Vector<uint8_t>& data, CryptoAlgorithmIdentifier hashAlgorithmIdentifier, size_t saltLength)
{
    // Perform digest operation with the specified algorithm on the given data.
    Vector<uint8_t> dataHash;
    {
        auto digestAlgorithm = hashCryptoDigestAlgorithm(hashAlgorithmIdentifier);
        if (!digestAlgorithm)
            return WTF::nullopt;

        auto digest = PAL::CryptoDigest::create(*digestAlgorithm);
        if (!digest)
            return WTF::nullopt;

        digest->addBytes(data.data(), data.size());
        dataHash = digest->computeHash();
    }

    // Construct the `sig-val` s-expression that contains the signature data.
    PAL::GCrypt::Handle<gcry_sexp_t> signatureSexp;
    gcry_error_t error = gcry_sexp_build(&signatureSexp, nullptr, "(sig-val(rsa(s %b)))",
        signature.size(), signature.data());
    if (error != GPG_ERR_NO_ERROR) {
        PAL::GCrypt::logError(error);
        return WTF::nullopt;
    }

    // Construct the `data` s-expression that contains PSS-padded hashed data.
    PAL::GCrypt::Handle<gcry_sexp_t> dataSexp;
    {
        auto shaAlgorithm = hashAlgorithmName(hashAlgorithmIdentifier);
        if (!shaAlgorithm)
            return WTF::nullopt;

        error = gcry_sexp_build(&dataSexp, nullptr, "(data(flags pss)(salt-length %u)(hash %s %b))",
            saltLength, *shaAlgorithm, dataHash.size(), dataHash.data());
        if (error != GPG_ERR_NO_ERROR) {
            PAL::GCrypt::logError(error);
            return WTF::nullopt;
        }
    }

    // Perform the PK verification. We report success if there's no error returned, or
    // a failure in any other case. OperationError should not be returned at this point,
    // avoiding spilling information about the exact cause of verification failure.
    error = gcry_pk_verify(signatureSexp, dataSexp, keySexp);
    return { error == GPG_ERR_NO_ERROR };
}

ExceptionOr<Vector<uint8_t>> CryptoAlgorithmRSA_PSS::platformSign(const CryptoAlgorithmRsaPssParams& parameters, const CryptoKeyRSA& key, const Vector<uint8_t>& data)
{
    RELEASE_ASSERT_WITH_SECURITY_IMPLICATION(!(key.keySizeInBits() % 8));
    auto output = gcryptSign(key.platformKey(), data, key.hashAlgorithmIdentifier(), parameters.saltLength, key.keySizeInBits() / 8);
    if (!output)
        return Exception { OperationError };
    return WTFMove(*output);
}

ExceptionOr<bool> CryptoAlgorithmRSA_PSS::platformVerify(const CryptoAlgorithmRsaPssParams& parameters, const CryptoKeyRSA& key, const Vector<uint8_t>& signature, const Vector<uint8_t>& data)
{
    auto output = gcryptVerify(key.platformKey(), signature, data, key.hashAlgorithmIdentifier(), parameters.saltLength);
    if (!output)
        return Exception { OperationError };
    return WTFMove(*output);
}


} // namespace WebCore

#endif // ENABLE(WEB_CRYPTO)