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/*
* Copyright (C) 2024 Igalia S.L. All rights reserved.
* Copyright (C) 2024 Metrological Group B.V.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include "RTCRtpSFrameTransformer.h"
#if USE(GSTREAMER_WEBRTC)
#include "CryptoAlgorithmAESCTR.h"
#include "OpenSSLCryptoUniquePtr.h"
#include "SFrameUtils.h"
#include <openssl/aes.h>
#include <openssl/core_names.h>
#include <openssl/evp.h>
#include <openssl/kdf.h>
namespace WebCore {
static ExceptionOr<Vector<uint8_t>> deriveHKDFBits(const Vector<uint8_t>& key, const Vector<uint8_t>& salt, const Vector<uint8_t>& info, size_t lengthInBytes)
{
auto paramsBuilder = OsslParamBldPtr(OSSL_PARAM_BLD_new());
if (!paramsBuilder)
return Exception { ExceptionCode::OperationError };
EVPKDFPtr kdf(EVP_KDF_fetch(nullptr, "HKDF", nullptr));
EVPKDFCtxPtr kdfCtx(EVP_KDF_CTX_new(kdf.get()));
if (!OSSL_PARAM_BLD_push_utf8_string(paramsBuilder.get(), OSSL_KDF_PARAM_DIGEST, SN_sha256, strlen(SN_sha256)))
return Exception { ExceptionCode::OperationError };
if (!OSSL_PARAM_BLD_push_octet_string(paramsBuilder.get(), OSSL_KDF_PARAM_KEY, key.data(), key.size()))
return Exception { ExceptionCode::OperationError };
if (!OSSL_PARAM_BLD_push_octet_string(paramsBuilder.get(), OSSL_KDF_PARAM_INFO, info.data(), info.size()))
return Exception { ExceptionCode::OperationError };
if (!OSSL_PARAM_BLD_push_octet_string(paramsBuilder.get(), OSSL_KDF_PARAM_SALT, salt.data(), salt.size()))
return Exception { ExceptionCode::OperationError };
auto params = OsslParamPtr(OSSL_PARAM_BLD_to_param(paramsBuilder.get()));
if (!params)
return Exception { ExceptionCode::OperationError };
Vector<uint8_t> output(lengthInBytes / 8);
if (!EVP_KDF_derive(kdfCtx.get(), output.data(), output.sizeInBytes(), params.get()))
return Exception { ExceptionCode::OperationError };
return output;
}
ExceptionOr<Vector<uint8_t>> RTCRtpSFrameTransformer::computeSaltKey(const Vector<uint8_t>& rawKey)
{
return deriveHKDFBits(rawKey, "SFrame10"_span, "salt"_span, 96);
}
static ExceptionOr<Vector<uint8_t>> createBaseSFrameKey(const Vector<uint8_t>& rawKey)
{
return deriveHKDFBits(rawKey, "SFrame10"_span, "key"_span, 128);
}
ExceptionOr<Vector<uint8_t>> RTCRtpSFrameTransformer::computeAuthenticationKey(const Vector<uint8_t>& rawKey)
{
auto key = createBaseSFrameKey(rawKey);
if (key.hasException())
return key;
return deriveHKDFBits(key.returnValue().subspan(0, 16), "SFrame10 AES CM AEAD"_span, "auth"_span, 256);
}
ExceptionOr<Vector<uint8_t>> RTCRtpSFrameTransformer::computeEncryptionKey(const Vector<uint8_t>& rawKey)
{
auto key = createBaseSFrameKey(rawKey);
if (key.hasException())
return key;
return deriveHKDFBits(key.returnValue().subspan(0, 16), "SFrame10 AES CM AEAD"_span, "enc"_span, 128);
}
// FIXME: This is copied from CryptoAlgorithmAESCTROpenSSL. Remove when the GTK/WPE ports include
// OpenSSL.cmake in their build.
static std::optional<Vector<uint8_t>> crypt(int operation, const Vector<uint8_t>& key, const Vector<uint8_t>& counter, size_t counterLength, std::span<const uint8_t> inputText)
{
constexpr size_t blockSize = 16;
const EVP_CIPHER* algorithm = EVP_aes_128_ctr();
if (!algorithm)
return std::nullopt;
EvpCipherCtxPtr ctx;
int len;
// Create and initialize the context
if (!(ctx = EvpCipherCtxPtr(EVP_CIPHER_CTX_new())))
return std::nullopt;
const size_t blocks = roundUpToMultipleOf(blockSize, inputText.size()) / blockSize;
// Detect loop
if (counterLength < sizeof(size_t) * 8 && blocks > ((size_t)1 << counterLength))
return std::nullopt;
// Calculate capacity before overflow
CryptoAlgorithmAESCTR::CounterBlockHelper counterBlockHelper(counter, counterLength);
size_t capacity = counterBlockHelper.countToOverflowSaturating();
// Divide data into two parts if necessary
size_t headSize = inputText.size();
if (capacity < blocks)
headSize = capacity * blockSize;
Vector<uint8_t> outputText(inputText.size());
// First part
{
// Initialize the encryption(decryption) operation
if (1 != EVP_CipherInit_ex(ctx.get(), algorithm, nullptr, key.data(), counter.data(), operation))
return std::nullopt;
// Disable padding
if (1 != EVP_CIPHER_CTX_set_padding(ctx.get(), 0))
return std::nullopt;
// Provide the message to be encrypted(decrypted), and obtain the encrypted(decrypted) output
if (1 != EVP_CipherUpdate(ctx.get(), outputText.data(), &len, inputText.data(), headSize))
return std::nullopt;
// Finalize the encryption(decryption)
if (1 != EVP_CipherFinal_ex(ctx.get(), outputText.subvector(len).mutableSpan().data() , &len))
return std::nullopt;
}
// Second part
if (capacity < blocks) {
size_t tailSize = inputText.size() - headSize;
Vector<uint8_t> remainingCounter = counterBlockHelper.counterVectorAfterOverflow();
// Initialize the encryption(decryption) operation
if (1 != EVP_CipherInit_ex(ctx.get(), algorithm, nullptr, key.data(), remainingCounter.data(), operation))
return std::nullopt;
// Disable padding
if (1 != EVP_CIPHER_CTX_set_padding(ctx.get(), 0))
return std::nullopt;
// Provide the message to be encrypted(decrypted), and obtain the encrypted(decrypted) output
if (1 != EVP_CipherUpdate(ctx.get(), outputText.subvector(headSize).mutableSpan().data(), &len, inputText.subspan(headSize).data(), tailSize))
return std::nullopt;
// Finalize the encryption(decryption)
if (1 != EVP_CipherFinal_ex(ctx.get(), outputText.subvector(headSize + len).mutableSpan().data(), &len))
return std::nullopt;
}
return outputText;
}
ExceptionOr<Vector<uint8_t>> RTCRtpSFrameTransformer::decryptData(std::span<const uint8_t> data, const Vector<uint8_t>& iv, const Vector<uint8_t>& key)
{
auto output = crypt(0, key, iv, iv.sizeInBytes(), data);
if (!output)
return Exception { ExceptionCode::OperationError };
return WTFMove(*output);
}
ExceptionOr<Vector<uint8_t>> RTCRtpSFrameTransformer::encryptData(std::span<const uint8_t> data, const Vector<uint8_t>& iv, const Vector<uint8_t>& key)
{
auto output = crypt(1, key, iv, iv.sizeInBytes(), data);
if (!output)
return Exception { ExceptionCode::OperationError };
return WTFMove(*output);
}
Vector<uint8_t> RTCRtpSFrameTransformer::computeEncryptedDataSignature(const Vector<uint8_t>& nonce, std::span<const uint8_t> header, std::span<const uint8_t> data, const Vector<uint8_t>& key)
{
Vector<uint8_t> signature(32);
Vector<uint8_t> payload;
payload.appendVector(encodeBigEndian(header.size()));
payload.appendVector(encodeBigEndian(data.size()));
auto iv = nonce.span();
payload.append(iv.subspan(0, 12));
payload.append(header);
payload.append(data);
HMAC(EVP_sha256(), key.data(), key.size(), payload.data(), payload.size(), signature.data(), nullptr);
return signature;
}
void RTCRtpSFrameTransformer::updateAuthenticationSize()
{
size_t digestLength = 32;
if (m_authenticationSize > digestLength)
m_authenticationSize = digestLength;
}
} // namespace WebCore
#endif // USE(GSTREAMER_WEBRTC)
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