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45 lines
1.7 KiB
C++
45 lines
1.7 KiB
C++
#include "XChunkProcessorSalsa20Decryption.h"
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#include <cassert>
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#include "Crypto.h"
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#include "AbstractSalsa20Processor.h"
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XChunkProcessorSalsa20Decryption::XChunkProcessorSalsa20Decryption(const int streamCount, std::string& zoneName, const uint8_t* salsa20Key, const size_t keySize)
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: AbstractSalsa20Processor(streamCount, zoneName, salsa20Key, keySize)
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{
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}
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size_t XChunkProcessorSalsa20Decryption::Process(const int streamNumber, const uint8_t* input, const size_t inputLength, uint8_t* output, const size_t outputBufferSize)
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{
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assert(streamNumber >= 0 && streamNumber < m_stream_count);
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assert(input != nullptr);
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assert(output != nullptr);
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assert(inputLength <= outputBufferSize);
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auto& streamContext = m_stream_contexts[streamNumber];
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// Initialize Salsa20 with an IV of the first 8 bytes of the current hash block
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streamContext.m_salsa20->SetIV(GetHashBlock(streamNumber), SALSA20_IV_SIZE);
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streamContext.m_salsa20->Process(input, output, inputLength);
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// Hash decrypted XChunk
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uint8_t blockSha1Hash[SHA1_HASH_SIZE];
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streamContext.m_sha1->Init();
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streamContext.m_sha1->Process(output, inputLength);
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streamContext.m_sha1->Finish(&blockSha1Hash);
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// Advance index to next hash block
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m_stream_block_indices[streamNumber] = (m_stream_block_indices[streamNumber] + 1) % BLOCK_HASHES_COUNT;
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auto* nextHashBlock = GetHashBlock(streamNumber);
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// XOR the upcoming hash block with the hash of the XChunk utilizing the previous hash block
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for (unsigned int hashOffset = 0; hashOffset < sizeof(blockSha1Hash); hashOffset++)
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{
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nextHashBlock[hashOffset] ^= blockSha1Hash[hashOffset];
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}
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return inputLength;
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}
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