/*
* Key Derivation Function interfaces
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_KDF_BASE_H_
#define BOTAN_KDF_BASE_H_

#include <botan/secmem.h>
#include <botan/exceptn.h>
#include <string>

namespace Botan {

/**
* Key Derivation Function
*/
class BOTAN_PUBLIC_API(2,0) KDF
   {
   public:
      virtual ~KDF() = default;

      /**
      * Create an instance based on a name
      * If provider is empty then best available is chosen.
      * @param algo_spec algorithm name
      * @param provider provider implementation to choose
      * @return a null pointer if the algo/provider combination cannot be found
      */
      static std::unique_ptr<KDF>
         create(const std::string& algo_spec,
                const std::string& provider = "");

      /**
      * Create an instance based on a name, or throw if the
      * algo/provider combination cannot be found. If provider is
      * empty then best available is chosen.
      */
      static std::unique_ptr<KDF>
         create_or_throw(const std::string& algo_spec,
                         const std::string& provider = "");

      /**
      * @return list of available providers for this algorithm, empty if not available
      */
      static std::vector<std::string> providers(const std::string& algo_spec);

      /**
      * @return KDF name
      */
      virtual std::string name() const = 0;

      /**
      * Derive a key
      * @param key buffer holding the derived key, must be of length key_len
      * @param key_len the desired output length in bytes
      * @param secret the secret input
      * @param secret_len size of secret in bytes
      * @param salt a diversifier
      * @param salt_len size of salt in bytes
      * @param label purpose for the derived keying material
      * @param label_len size of label in bytes
      */
      virtual void kdf(uint8_t key[], size_t key_len,
                       const uint8_t secret[], size_t secret_len,
                       const uint8_t salt[], size_t salt_len,
                       const uint8_t label[], size_t label_len) const = 0;

      /**
      * Derive a key
      * @param key_len the desired output length in bytes
      * @param secret the secret input
      * @param secret_len size of secret in bytes
      * @param salt a diversifier
      * @param salt_len size of salt in bytes
      * @param label purpose for the derived keying material
      * @param label_len size of label in bytes
      * @return the derived key
      */
      secure_vector<uint8_t> derive_key(size_t key_len,
                                    const uint8_t secret[],
                                    size_t secret_len,
                                    const uint8_t salt[],
                                    size_t salt_len,
                                    const uint8_t label[] = nullptr,
                                    size_t label_len = 0) const
         {
         secure_vector<uint8_t> key(key_len);
         kdf(key.data(), key.size(), secret, secret_len, salt, salt_len, label, label_len);
         return key;
         }

      /**
      * Derive a key
      * @param key_len the desired output length in bytes
      * @param secret the secret input
      * @param salt a diversifier
      * @param label purpose for the derived keying material
      * @return the derived key
      */
      secure_vector<uint8_t> derive_key(size_t key_len,
                                    const secure_vector<uint8_t>& secret,
                                    const std::string& salt = "",
                                    const std::string& label = "") const
         {
         return derive_key(key_len, secret.data(), secret.size(),
                           cast_char_ptr_to_uint8(salt.data()),
                           salt.length(),
                           cast_char_ptr_to_uint8(label.data()),
                           label.length());

         }

      /**
      * Derive a key
      * @param key_len the desired output length in bytes
      * @param secret the secret input
      * @param salt a diversifier
      * @param label purpose for the derived keying material
      * @return the derived key
      */
      template<typename Alloc, typename Alloc2, typename Alloc3>
      secure_vector<uint8_t> derive_key(size_t key_len,
                                     const std::vector<uint8_t, Alloc>& secret,
                                     const std::vector<uint8_t, Alloc2>& salt,
                                     const std::vector<uint8_t, Alloc3>& label) const
         {
         return derive_key(key_len,
                           secret.data(), secret.size(),
                           salt.data(), salt.size(),
                           label.data(), label.size());
         }

      /**
      * Derive a key
      * @param key_len the desired output length in bytes
      * @param secret the secret input
      * @param salt a diversifier
      * @param salt_len size of salt in bytes
      * @param label purpose for the derived keying material
      * @return the derived key
      */
      secure_vector<uint8_t> derive_key(size_t key_len,
                                    const secure_vector<uint8_t>& secret,
                                    const uint8_t salt[],
                                    size_t salt_len,
                                    const std::string& label = "") const
         {
         return derive_key(key_len,
                           secret.data(), secret.size(),
                           salt, salt_len,
                           cast_char_ptr_to_uint8(label.data()),
                           label.size());
         }

      /**
      * Derive a key
      * @param key_len the desired output length in bytes
      * @param secret the secret input
      * @param secret_len size of secret in bytes
      * @param salt a diversifier
      * @param label purpose for the derived keying material
      * @return the derived key
      */
      secure_vector<uint8_t> derive_key(size_t key_len,
                                    const uint8_t secret[],
                                    size_t secret_len,
                                    const std::string& salt = "",
                                    const std::string& label = "") const
         {
         return derive_key(key_len, secret, secret_len,
                           cast_char_ptr_to_uint8(salt.data()),
                           salt.length(),
                           cast_char_ptr_to_uint8(label.data()),
                           label.length());
         }

      /**
      * @return new object representing the same algorithm as *this
      */
      virtual std::unique_ptr<KDF> new_object() const = 0;

      /**
      * @return new object representing the same algorithm as *this
      */
      KDF* clone() const
         {
         return this->new_object().release();
         }
   };

/**
* Factory method for KDF (key derivation function)
* @param algo_spec the name of the KDF to create
* @return pointer to newly allocated object of that type
*
* Prefer KDF::create
*/
inline KDF* get_kdf(const std::string& algo_spec)
   {
   auto kdf = KDF::create(algo_spec);
   if(kdf)
      return kdf.release();

   if(algo_spec == "Raw")
      return nullptr;

   throw Algorithm_Not_Found(algo_spec);
   }

}

#endif