/*

* OpenPGP PBKDF

* (C) 1999-2007,2017 Jack Lloyd

* (C) 2018 Ribose Inc

*

* Distributed under the terms of the Botan license

*/

#ifndef BOTAN_OPENPGP_S2K_H_

#define BOTAN_OPENPGP_S2K_H_

#include <botan/pbkdf.h>

#include <botan/pwdhash.h>

#include <botan/hash.h>

/*

This header will not be fully internal - the RFC4880 count

encoding functions will remain here. But the definition of

OpenPGP_S2K will be made internal

*/

//BOTAN_FUTURE_INTERNAL_HEADER(pgp_s2k.h)

namespace Botan {

/**

* RFC 4880 encodes the iteration count to a single-byte value

*/

uint8_t BOTAN_PUBLIC_API(2,8) RFC4880_encode_count(size_t iterations);

/**

* Decode the iteration count from RFC 4880 encoding

*/

size_t BOTAN_PUBLIC_API(2,8) RFC4880_decode_count(uint8_t encoded_iter);

/**

* Round an arbitrary iteration count to next largest iteration count

* supported by RFC4880 encoding.

*/

inline size_t RFC4880_round_iterations(size_t iterations)

   {

   return RFC4880_decode_count(RFC4880_encode_count(iterations));

   }

/**

* OpenPGP's S2K

*

* See RFC 4880 sections 3.7.1.1, 3.7.1.2, and 3.7.1.3

* If the salt is empty and iterations == 1, "simple" S2K is used

* If the salt is non-empty and iterations == 1, "salted" S2K is used

* If the salt is non-empty and iterations > 1, "iterated" S2K is used

*

* Due to complexities of the PGP S2K algorithm, time-based derivation

* is not supported. So if iterations == 0 and msec.count() > 0, an

* exception is thrown. In the future this may be supported, in which

* case "iterated" S2K will be used and the number of iterations

* performed is returned.

*

* Note that unlike PBKDF2, OpenPGP S2K's "iterations" are defined as

* the number of bytes hashed.

*/

class BOTAN_PUBLIC_API(2,2) OpenPGP_S2K final : public PBKDF

   {

   public:

      /**

      * @param hash the hash function to use

      */

      explicit OpenPGP_S2K(HashFunction* hash) : m_hash(hash) {}

      std::string name() const override

         {

         return "OpenPGP-S2K(" + m_hash->name() + ")";

         }

      PBKDF* clone() const override

         {

         return new OpenPGP_S2K(m_hash->clone());

         }

      size_t pbkdf(uint8_t output_buf[], size_t output_len,

                   const std::string& passphrase,

                   const uint8_t salt[], size_t salt_len,

                   size_t iterations,

                   std::chrono::milliseconds msec) const override;

      /**

      * RFC 4880 encodes the iteration count to a single-byte value

      */

      static uint8_t encode_count(size_t iterations)

         {

         return RFC4880_encode_count(iterations);

         }

      static size_t decode_count(uint8_t encoded_iter)

         {

         return RFC4880_decode_count(encoded_iter);

         }

   private:

      std::unique_ptr<HashFunction> m_hash;

   };

/**

* OpenPGP's S2K

*

* See RFC 4880 sections 3.7.1.1, 3.7.1.2, and 3.7.1.3

* If the salt is empty and iterations == 1, "simple" S2K is used

* If the salt is non-empty and iterations == 1, "salted" S2K is used

* If the salt is non-empty and iterations > 1, "iterated" S2K is used

*

* Note that unlike PBKDF2, OpenPGP S2K's "iterations" are defined as

* the number of bytes hashed.

*/

class BOTAN_PUBLIC_API(2,8) RFC4880_S2K final : public PasswordHash

   {

   public:

      /**

      * @param hash the hash function to use

      * @param iterations is rounded due to PGP formatting

      */

      RFC4880_S2K(HashFunction* hash, size_t iterations);

      std::string to_string() const override;

      size_t iterations() const override { return m_iterations; }

      void derive_key(uint8_t out[], size_t out_len,

                      const char* password, size_t password_len,

                      const uint8_t salt[], size_t salt_len) const override;

   private:

      std::unique_ptr<HashFunction> m_hash;

      size_t m_iterations;

   };

class BOTAN_PUBLIC_API(2,8) RFC4880_S2K_Family final : public PasswordHashFamily

   {

   public:

      RFC4880_S2K_Family(HashFunction* hash) : m_hash(hash) {}

      std::string name() const override;

      std::unique_ptr<PasswordHash> tune(size_t output_len,

                                         std::chrono::milliseconds msec,

                                         size_t max_mem) const override;

      /**

      * Return some default parameter set for this PBKDF that should be good

      * enough for most users. The value returned may change over time as

      * processing power and attacks improve.

      */

      std::unique_ptr<PasswordHash> default_params() const override;

      std::unique_ptr<PasswordHash> from_iterations(size_t iter) const override;

      std::unique_ptr<PasswordHash> from_params(

         size_t iter, size_t, size_t) const override;

   private:

      std::unique_ptr<HashFunction> m_hash;

   };

}

#endif