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/**
* Copyright (C) 2021-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/base/data_range.h"
#include "mongo/base/data_range_cursor.h"
#include "mongo/base/secure_allocator.h"
#include "mongo/base/status.h"
#include "mongo/crypto/symmetric_crypto.h"
namespace mongo {
namespace crypto {
/** Accumulates unaligned input, and presents it in block aligned segments to a caller provided
* callback.
*/
class BlockPacker {
public:
BlockPacker()
: _blockData(_blockBuffer->data(), _blockBuffer->size()), _blockCursor(_blockData) {}
template <typename OperationFn>
StatusWith<size_t> pack(ConstDataRange inData, OperationFn&& op) {
ConstDataRangeCursor inCursor(inData);
// We must always attempt to accumulate a block. We must only perform the operation when we
// would overflow a block. The finalization operation must have the last block of data
// available.
size_t bytesWritten = 0;
// Pad block. This needs to happen if the block is partially full from a previous iteration.
// Otherwise, we don't need to align with earlier input, and can consume the data straight
// out of the input.
if (_blockCursor.length() < aesBlockSize) {
size_t bytesToFill = std::min(inCursor.length(), _blockCursor.length());
ConstDataRange bytesToFillRange(inCursor.data(), bytesToFill);
inCursor.advance(bytesToFill);
_blockCursor.writeAndAdvance(bytesToFillRange);
}
// If we've consumed all the input, we're done. Processing will happen in later method
// calls.
if (inCursor.length() == 0) {
return 0;
}
// We have more input to consume. If we already have a block, flush it.
if (_blockCursor.length() == 0) {
StatusWith<size_t> swBlockBytesWritten = op(ConstDataRange(*_blockBuffer));
if (!swBlockBytesWritten.isOK()) {
return swBlockBytesWritten.getStatus();
}
bytesWritten += swBlockBytesWritten.getValue();
_blockCursor = DataRangeCursor(_blockData);
}
// We can now process a whole number of blocks. However, we must not process the last block,
// which is defered until later calls.
std::lldiv_t results = std::div(static_cast<const long long>(inCursor.length()),
static_cast<const long long>(aesBlockSize));
size_t blocksToProcess = results.quot;
size_t bytesRemaining = results.rem;
if (blocksToProcess > 0 && bytesRemaining == 0) {
blocksToProcess -= 1;
}
size_t bytesToProcess = blocksToProcess * aesBlockSize;
if (bytesToProcess) {
ConstDataRange invocationInput(inCursor.data(), inCursor.data() + bytesToProcess);
inCursor.advance(bytesToProcess);
StatusWith<size_t> swBytesDecrypted = op(invocationInput);
if (!swBytesDecrypted.isOK()) {
return swBytesDecrypted.getStatus();
}
bytesWritten += swBytesDecrypted.getValue();
}
// We must now pack the remaining data into the block
invariant(_blockCursor.length() >= inCursor.length());
_blockCursor.writeAndAdvance(inCursor);
return static_cast<size_t>(bytesWritten);
}
ConstDataRange getBlock() const {
return ConstDataRange(_blockData.data(), _blockData.length() - _blockCursor.length());
}
private:
// buffer to store a single block of data, to be encrypted by update when filled, or by finalize
// with padding. 16 is the block length for AES.
SecureArray<uint8_t, aesBlockSize> _blockBuffer;
DataRange _blockData;
DataRangeCursor _blockCursor;
};
} // namespace crypto
} // namespace mongo
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