libcryfs/crypto/symmetric/GCM_Cipher.h

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2015-10-27 23:19:20 +01:00
#pragma once
#ifndef MESSMER_CPPUTILS_CRYPTO_SYMMETRIC_GCMCIPHER_H_
#define MESSMER_CPPUTILS_CRYPTO_SYMMETRIC_GCMCIPHER_H_
#include "../../data/FixedSizeData.h"
#include "../../data/Data.h"
#include "../../random/Random.h"
#include <cryptopp/cryptopp/gcm.h>
#include "Cipher.h"
namespace cpputils {
template<typename BlockCipher, unsigned int KeySize>
class GCM_Cipher {
public:
using EncryptionKey = FixedSizeData<KeySize>;
static EncryptionKey CreateKey(RandomGenerator &randomGenerator) {
return randomGenerator.getFixedSize<EncryptionKey::BINARY_LENGTH>();
}
static constexpr unsigned int ciphertextSize(unsigned int plaintextBlockSize) {
return plaintextBlockSize + IV_SIZE + TAG_SIZE;
}
static constexpr unsigned int plaintextSize(unsigned int ciphertextBlockSize) {
return ciphertextBlockSize - IV_SIZE - TAG_SIZE;
}
static Data encrypt(const byte *plaintext, unsigned int plaintextSize, const EncryptionKey &encKey);
static boost::optional<Data> decrypt(const byte *ciphertext, unsigned int ciphertextSize, const EncryptionKey &encKey);
private:
static constexpr unsigned int IV_SIZE = BlockCipher::BLOCKSIZE;
static constexpr unsigned int TAG_SIZE = 16;
};
template<typename BlockCipher, unsigned int KeySize>
Data GCM_Cipher<BlockCipher, KeySize>::encrypt(const byte *plaintext, unsigned int plaintextSize, const EncryptionKey &encKey) {
FixedSizeData<IV_SIZE> iv = Random::PseudoRandom().getFixedSize<IV_SIZE>();
typename CryptoPP::GCM<BlockCipher, CryptoPP::GCM_64K_Tables>::Encryption encryption;
encryption.SetKeyWithIV(encKey.data(), encKey.BINARY_LENGTH, iv.data(), IV_SIZE);
Data ciphertext(ciphertextSize(plaintextSize));
std::memcpy(ciphertext.data(), iv.data(), IV_SIZE);
CryptoPP::ArraySource(plaintext, plaintextSize, true,
new CryptoPP::AuthenticatedEncryptionFilter(encryption,
new CryptoPP::ArraySink((byte*)ciphertext.data() + IV_SIZE, ciphertext.size() - IV_SIZE),
false, TAG_SIZE
)
);
return ciphertext;
}
template<typename BlockCipher, unsigned int KeySize>
boost::optional<Data> GCM_Cipher<BlockCipher, KeySize>::decrypt(const byte *ciphertext, unsigned int ciphertextSize, const EncryptionKey &encKey) {
if (ciphertextSize < IV_SIZE + TAG_SIZE) {
return boost::none;
}
const byte *ciphertextIV = ciphertext;
const byte *ciphertextData = ciphertext + IV_SIZE;
typename CryptoPP::GCM<BlockCipher, CryptoPP::GCM_64K_Tables>::Decryption decryption;
decryption.SetKeyWithIV((byte*)encKey.data(), encKey.BINARY_LENGTH, ciphertextIV, IV_SIZE);
Data plaintext(plaintextSize(ciphertextSize));
try {
CryptoPP::ArraySource((byte*)ciphertextData, ciphertextSize - IV_SIZE, true,
new CryptoPP::AuthenticatedDecryptionFilter(decryption,
new CryptoPP::ArraySink((byte*)plaintext.data(), plaintext.size()),
CryptoPP::AuthenticatedDecryptionFilter::DEFAULT_FLAGS, TAG_SIZE
)
);
return std::move(plaintext);
} catch (const CryptoPP::HashVerificationFilter::HashVerificationFailed &e) {
return boost::none;
}
}
}
#endif