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/*
* 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
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS 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 APPLE INC. OR ITS 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 "CryptoAlgorithmHKDF.h"
#if ENABLE(WEB_CRYPTO)
#include "CryptoAlgorithmHkdfParams.h"
#include "CryptoKeyRaw.h"
#include "GCryptUtilities.h"
namespace WebCore {
// libgcrypt doesn't provide HKDF functionality, so we have to implement it manually.
// We should switch to the libgcrypt-provided implementation once it's available.
// https://bugs.webkit.org/show_bug.cgi?id=171536
static std::optional<Vector<uint8_t>> gcryptDeriveBits(const Vector<uint8_t>& key, const Vector<uint8_t>& salt, const Vector<uint8_t>& info, size_t lengthInBytes, CryptoAlgorithmIdentifier identifier)
{
// libgcrypt doesn't provide HKDF support, so we have to implement
// the functionality ourselves as specified in RFC5869.
// https://www.ietf.org/rfc/rfc5869.txt
auto macAlgorithm = hmacAlgorithm(identifier);
if (!macAlgorithm)
return std::nullopt;
// We can immediately discard invalid output lengths, otherwise needed for the expand step.
size_t macLength = gcry_mac_get_algo_maclen(*macAlgorithm);
if (lengthInBytes > macLength * 255)
return std::nullopt;
PAL::GCrypt::Handle<gcry_mac_hd_t> handle;
gcry_error_t error = gcry_mac_open(&handle, *macAlgorithm, 0, nullptr);
if (error != GPG_ERR_NO_ERROR) {
PAL::GCrypt::logError(error);
return std::nullopt;
}
// Step 1 -- Extract. A pseudo-random key is generated with the specified algorithm
// for the given salt value (used as a key) and the 'input keying material'.
Vector<uint8_t> pseudoRandomKey(macLength);
{
// If the salt vector is empty, a zeroed-out key of macLength size should be used.
if (salt.isEmpty()) {
Vector<uint8_t> zeroedKey(macLength, 0);
error = gcry_mac_setkey(handle, zeroedKey.data(), zeroedKey.size());
} else
error = gcry_mac_setkey(handle, salt.data(), salt.size());
if (error != GPG_ERR_NO_ERROR) {
PAL::GCrypt::logError(error);
return std::nullopt;
}
error = gcry_mac_write(handle, key.data(), key.size());
if (error != GPG_ERR_NO_ERROR) {
PAL::GCrypt::logError(error);
return std::nullopt;
}
size_t pseudoRandomKeySize = pseudoRandomKey.size();
error = gcry_mac_read(handle, pseudoRandomKey.data(), &pseudoRandomKeySize);
if (error != GPG_ERR_NO_ERROR) {
PAL::GCrypt::logError(error);
return std::nullopt;
}
// Something went wrong if libgcrypt didn't write out the proper amount of data.
if (pseudoRandomKeySize != macLength)
return std::nullopt;
}
// Step #2 -- Expand.
Vector<uint8_t> output;
{
// Deduce the number of needed iterations to retrieve the necessary amount of data.
size_t numIterations = (lengthInBytes + macLength) / macLength;
// Block from the previous iteration is used in the current one, except
// in the first iteration when it's empty.
Vector<uint8_t> lastBlock(macLength);
for (size_t i = 0; i < numIterations; ++i) {
error = gcry_mac_reset(handle);
if (error != GPG_ERR_NO_ERROR) {
PAL::GCrypt::logError(error);
return std::nullopt;
}
error = gcry_mac_setkey(handle, pseudoRandomKey.data(), pseudoRandomKey.size());
if (error != GPG_ERR_NO_ERROR) {
PAL::GCrypt::logError(error);
return std::nullopt;
}
// T(0) = empty string (zero length) -- i.e. empty lastBlock
// T(i) = HMAC-Hash(PRK, T(i-1) | info | hex(i)) -- | represents concatenation
Vector<uint8_t> blockData;
if (i)
blockData.appendVector(lastBlock);
blockData.appendVector(info);
blockData.append(i + 1);
error = gcry_mac_write(handle, blockData.data(), blockData.size());
if (error != GPG_ERR_NO_ERROR) {
PAL::GCrypt::logError(error);
return std::nullopt;
}
size_t blockSize = lastBlock.size();
error = gcry_mac_read(handle, lastBlock.data(), &blockSize);
if (error != GPG_ERR_NO_ERROR) {
PAL::GCrypt::logError(error);
return std::nullopt;
}
// Something went wrong if libgcrypt didn't write out the proper amount of data.
if (blockSize != lastBlock.size())
return std::nullopt;
// Append the current block data to the output vector.
output.appendVector(lastBlock);
}
}
// Clip output vector to the requested size.
output.resize(lengthInBytes);
return output;
}
ExceptionOr<Vector<uint8_t>> CryptoAlgorithmHKDF::platformDeriveBits(const CryptoAlgorithmHkdfParams& parameters, const CryptoKeyRaw& key, size_t length)
{
auto output = gcryptDeriveBits(key.key(), parameters.saltVector(), parameters.infoVector(), length / 8, parameters.hashIdentifier);
if (!output)
return Exception { OperationError };
return WTFMove(*output);
}
} // namespace WebCore
#endif // ENABLE(WEB_CRYPTO)
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