gcm.h

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// gcm.h - originally written and placed in the public domain by Wei Dai

/// \file gcm.h
/// \brief GCM block cipher mode of operation
/// \since Crypto++ 5.6.0

#ifndef CRYPTOPP_GCM_H
#define CRYPTOPP_GCM_H

#include "authenc.h"
#include "modes.h"

// Clang 3.3 integrated assembler crash on Linux. Clang 3.4 due to compiler
// error with .intel_syntax, http://llvm.org/bugs/show_bug.cgi?id=24232
#if CRYPTOPP_BOOL_X32 || defined(CRYPTOPP_DISABLE_MIXED_ASM)
# define CRYPTOPP_DISABLE_GCM_ASM 1
#endif

NAMESPACE_BEGIN(CryptoPP)

/// \enum GCM_TablesOption
/// \brief GCM table size options
enum GCM_TablesOption {
    /// \brief Use a table with 2K entries
    GCM_2K_Tables,
    /// \brief Use a table with 64K entries
    GCM_64K_Tables};

/// \brief GCM block cipher base implementation
/// \details Base implementation of the AuthenticatedSymmetricCipher interface
/// \since Crypto++ 5.6.0
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE GCM_Base : public AuthenticatedSymmetricCipherBase
{
public:
    // AuthenticatedSymmetricCipher
    std::string AlgorithmName() const
        {return GetBlockCipher().AlgorithmName() + std::string("/GCM");}
    std::string AlgorithmProvider() const
        {return GetBlockCipher().AlgorithmProvider();}
    size_t MinKeyLength() const
        {return GetBlockCipher().MinKeyLength();}
    size_t MaxKeyLength() const
        {return GetBlockCipher().MaxKeyLength();}
    size_t DefaultKeyLength() const
        {return GetBlockCipher().DefaultKeyLength();}
    size_t GetValidKeyLength(size_t n) const
        {return GetBlockCipher().GetValidKeyLength(n);}
    bool IsValidKeyLength(size_t n) const
        {return GetBlockCipher().IsValidKeyLength(n);}
    unsigned int OptimalDataAlignment() const;
    IV_Requirement IVRequirement() const
        {return UNIQUE_IV;}
    unsigned int IVSize() const
        {return 12;}
    unsigned int MinIVLength() const
        {return 1;}
    unsigned int MaxIVLength() const
        {return UINT_MAX;}      // (W64LIT(1)<<61)-1 in the standard
    unsigned int DigestSize() const
        {return 16;}
    lword MaxHeaderLength() const
        {return (W64LIT(1)<<61)-1;}
    lword MaxMessageLength() const
        {return ((W64LIT(1)<<39)-256)/8;}

protected:
    // AuthenticatedSymmetricCipherBase
    bool AuthenticationIsOnPlaintext() const
        {return false;}
    unsigned int AuthenticationBlockSize() const
        {return HASH_BLOCKSIZE;}
    void SetKeyWithoutResync(const byte *userKey, size_t keylength, const NameValuePairs &params);
    void Resync(const byte *iv, size_t len);
    size_t AuthenticateBlocks(const byte *data, size_t len);
    void AuthenticateLastHeaderBlock();
    void AuthenticateLastConfidentialBlock();
    void AuthenticateLastFooterBlock(byte *mac, size_t macSize);
    SymmetricCipher & AccessSymmetricCipher() {return m_ctr;}

    virtual BlockCipher & AccessBlockCipher() =0;
    virtual GCM_TablesOption GetTablesOption() const =0;

    const BlockCipher & GetBlockCipher() const {return const_cast<GCM_Base *>(this)->AccessBlockCipher();}
    byte *HashBuffer() {return m_buffer+REQUIRED_BLOCKSIZE;}
    byte *HashKey() {return m_buffer+2*REQUIRED_BLOCKSIZE;}
    byte *MulTable() {return m_buffer+3*REQUIRED_BLOCKSIZE;}
    inline void ReverseHashBufferIfNeeded();

    class CRYPTOPP_DLL GCTR : public CTR_Mode_ExternalCipher::Encryption
    {
    protected:
        void IncrementCounterBy256();
    };

    GCTR m_ctr;
    static word16 s_reductionTable[256];
    static volatile bool s_reductionTableInitialized;
    enum {REQUIRED_BLOCKSIZE = 16, HASH_BLOCKSIZE = 16};
};

/// \brief GCM block cipher final implementation
/// \tparam T_BlockCipher block cipher
/// \tparam T_TablesOption table size, either \p GCM_2K_Tables or \p GCM_64K_Tables
/// \tparam T_IsEncryption direction in which to operate the cipher
/// \since Crypto++ 5.6.0
template <class T_BlockCipher, GCM_TablesOption T_TablesOption, bool T_IsEncryption>
class GCM_Final : public GCM_Base
{
public:
    static std::string StaticAlgorithmName()
        {return T_BlockCipher::StaticAlgorithmName() + std::string("/GCM");}
    bool IsForwardTransformation() const
        {return T_IsEncryption;}

private:
    GCM_TablesOption GetTablesOption() const {return T_TablesOption;}
    BlockCipher & AccessBlockCipher() {return m_cipher;}
    typename T_BlockCipher::Encryption m_cipher;
};

/// \brief GCM block cipher mode of operation
/// \tparam T_BlockCipher block cipher
/// \tparam T_TablesOption table size, either \p GCM_2K_Tables or \p GCM_64K_Tables
/// \details \p GCM provides the \p Encryption and \p Decryption typedef. See GCM_Base
///   and GCM_Final for the AuthenticatedSymmetricCipher implementation.
/// \sa <a href="http://www.cryptopp.com/wiki/GCM_Mode">GCM Mode</a> and
///   <A HREF="http://www.cryptopp.com/wiki/Modes_of_Operation">Modes of Operation</A>
///   on the Crypto++ wiki.
/// \since Crypto++ 5.6.0
template <class T_BlockCipher, GCM_TablesOption T_TablesOption=GCM_2K_Tables>
struct GCM : public AuthenticatedSymmetricCipherDocumentation
{
    typedef GCM_Final<T_BlockCipher, T_TablesOption, true> Encryption;
    typedef GCM_Final<T_BlockCipher, T_TablesOption, false> Decryption;
};

NAMESPACE_END

#endif