/*

* ChaCha20Poly1305 AEAD

* (C) 2014 Jack Lloyd

* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#ifndef BOTAN_AEAD_CHACHA20_POLY1305_H_

#define BOTAN_AEAD_CHACHA20_POLY1305_H_

#include <botan/aead.h>

#include <botan/assert.h>

#include <botan/mac.h>

#include <botan/stream_cipher.h>

namespace Botan {

/**

* Base class

* See draft-irtf-cfrg-chacha20-poly1305-03 for specification

* If a nonce of 64 bits is used the older version described in

* draft-agl-tls-chacha20poly1305-04 is used instead.

* If a nonce of 192 bits is used, XChaCha20Poly1305 is selected.

*/

class ChaCha20Poly1305_Mode : public AEAD_Mode {

   public:

      void set_associated_data_n(size_t idx, std::span<const uint8_t> ad) final;

      bool associated_data_requires_key() const override { return false; }

      std::string name() const override { return "ChaCha20Poly1305"; }

      size_t update_granularity() const override;

      size_t ideal_granularity() const override;

      Key_Length_Specification key_spec() const override { return Key_Length_Specification(32); }

      bool valid_nonce_length(size_t n) const override;

      size_t tag_size() const override { return 16; }

      void clear() override;

      void reset() override;

      bool has_keying_material() const final;

   protected:

      std::unique_ptr<StreamCipher> m_chacha;

      std::unique_ptr<MessageAuthenticationCode> m_poly1305;

      ChaCha20Poly1305_Mode();

      secure_vector<uint8_t> m_ad;

      size_t m_nonce_len = 0;

      size_t m_ctext_len = 0;

      bool cfrg_version() const { return m_nonce_len == 12 || m_nonce_len == 24; }

      void update_len(size_t len);

   private:

      void start_msg(const uint8_t nonce[], size_t nonce_len) override;

      void key_schedule(std::span<const uint8_t> key) override;

};

/**

* ChaCha20Poly1305 Encryption

*/

class ChaCha20Poly1305_Encryption final : public ChaCha20Poly1305_Mode {

   public:

      size_t output_length(size_t input_length) const override { return input_length + tag_size(); }

      size_t minimum_final_size() const override { return 0; }

   private:

      size_t process_msg(uint8_t buf[], size_t size) override;

      void finish_msg(secure_vector<uint8_t>& final_block, size_t offset = 0) override;

};

/**

* ChaCha20Poly1305 Decryption

*/

class ChaCha20Poly1305_Decryption final : public ChaCha20Poly1305_Mode {

   public:

      size_t output_length(size_t input_length) const override {

         BOTAN_ARG_CHECK(input_length >= tag_size(), "Sufficient input");

         return input_length - tag_size();

      }

      size_t minimum_final_size() const override { return tag_size(); }

   private:

      size_t process_msg(uint8_t buf[], size_t size) override;

      void finish_msg(secure_vector<uint8_t>& final_block, size_t offset = 0) override;

};

}  // namespace Botan

#endif