/* * GCM Mode * (C) 2013 Jack Lloyd * * Botan is released under the Simplified BSD License (see license.txt) */ #ifndef BOTAN_AEAD_GCM_H__ #define BOTAN_AEAD_GCM_H__ #include #include #include namespace Botan { class GHASH; /** * GCM Mode */ class BOTAN_DLL GCM_Mode : public AEAD_Mode { public: void set_associated_data(const byte ad[], size_t ad_len) override; std::string name() const override; size_t update_granularity() const override; Key_Length_Specification key_spec() const override; // GCM supports arbitrary nonce lengths bool valid_nonce_length(size_t) const override { return true; } size_t tag_size() const override { return m_tag_size; } void clear() override; protected: GCM_Mode(BlockCipher* cipher, size_t tag_size); const size_t m_BS = 16; const size_t m_tag_size; const std::string m_cipher_name; std::unique_ptr m_ctr; std::unique_ptr m_ghash; private: secure_vector start_raw(const byte nonce[], size_t nonce_len) override; void key_schedule(const byte key[], size_t length) override; }; /** * GCM Encryption */ class BOTAN_DLL GCM_Encryption final : public GCM_Mode { public: /** * @param cipher the 128 bit block cipher to use * @param tag_size is how big the auth tag will be */ GCM_Encryption(BlockCipher* cipher, size_t tag_size = 16) : GCM_Mode(cipher, tag_size) {} size_t output_length(size_t input_length) const override { return input_length + tag_size(); } size_t minimum_final_size() const override { return 0; } void update(secure_vector& blocks, size_t offset = 0) override; void finish(secure_vector& final_block, size_t offset = 0) override; }; /** * GCM Decryption */ class BOTAN_DLL GCM_Decryption final : public GCM_Mode { public: /** * @param cipher the 128 bit block cipher to use * @param tag_size is how big the auth tag will be */ GCM_Decryption(BlockCipher* cipher, size_t tag_size = 16) : GCM_Mode(cipher, tag_size) {} size_t output_length(size_t input_length) const override { BOTAN_ASSERT(input_length > tag_size(), "Sufficient input"); return input_length - tag_size(); } size_t minimum_final_size() const override { return tag_size(); } void update(secure_vector& blocks, size_t offset = 0) override; void finish(secure_vector& final_block, size_t offset = 0) override; }; /** * GCM's GHASH * Maybe a Transform? */ class BOTAN_DLL GHASH : public SymmetricAlgorithm { public: void set_associated_data(const byte ad[], size_t ad_len); secure_vector nonce_hash(const byte nonce[], size_t len); void start(const byte nonce[], size_t len); /* * Assumes input len is multiple of 16 */ void update(const byte in[], size_t len); secure_vector final(); Key_Length_Specification key_spec() const override { return Key_Length_Specification(16); } void clear() override; std::string name() const override { return "GHASH"; } private: void key_schedule(const byte key[], size_t key_len) override; void gcm_multiply(secure_vector& x) const; void ghash_update(secure_vector& x, const byte input[], size_t input_len); void add_final_block(secure_vector& x, size_t ad_len, size_t pt_len); secure_vector m_H; secure_vector m_H_ad; secure_vector m_nonce; secure_vector m_ghash; size_t m_ad_len = 0, m_text_len = 0; }; } #endif