/*
* Hooks for application level policies on TLS connections
* (C) 2004-2006,2013 Jack Lloyd
*
* Released under the terms of the Botan license
*/

#ifndef BOTAN_TLS_POLICY_H__
#define BOTAN_TLS_POLICY_H__

#include <botan/tls_version.h>
#include <botan/tls_ciphersuite.h>
#include <botan/x509cert.h>
#include <botan/dl_group.h>
#include <vector>

namespace Botan {

namespace TLS {

/**
* TLS Policy Base Class
* Inherit and overload as desired to suit local policy concerns
*/
class BOTAN_DLL Policy
   {
   public:

      /**
      * Returns a list of ciphers we are willing to negotiate, in
      * order of preference.
      */
      virtual std::vector<std::string> allowed_ciphers() const;

      /**
      * Returns a list of hash algorithms we are willing to use for
      * signatures, in order of preference.
      */
      virtual std::vector<std::string> allowed_signature_hashes() const;

      /**
      * Returns a list of MAC algorithms we are willing to use.
      */
      virtual std::vector<std::string> allowed_macs() const;

      /**
      * Returns a list of key exchange algorithms we are willing to
      * use, in order of preference. Allowed values: DH, empty string
      * (representing RSA using server certificate key)
      */
      virtual std::vector<std::string> allowed_key_exchange_methods() const;

      /**
      * Returns a list of signature algorithms we are willing to
      * use, in order of preference. Allowed values RSA and DSA.
      */
      virtual std::vector<std::string> allowed_signature_methods() const;

      /**
      * Return list of ECC curves we are willing to use in order of preference
      */
      virtual std::vector<std::string> allowed_ecc_curves() const;

      /**
      * Returns a list of compression algorithms we are willing to use,
      * in order of preference. Allowed values any value of
      * Compression_Method.
      *
      * @note Compression is not currently supported
      */
      virtual std::vector<byte> compression() const;

      /**
      * Choose an elliptic curve to use
      */
      virtual std::string choose_curve(const std::vector<std::string>& curve_names) const;

      /**
      * Attempt to negotiate the use of the heartbeat extension
      */
      virtual bool negotiate_heartbeat_support() const;

      /**
      * Allow renegotiation even if the counterparty doesn't
      * support the secure renegotiation extension.
      *
      * @warning Changing this to true exposes you to injected
      * plaintext attacks. Read RFC 5746 for background.
      */
      virtual bool allow_insecure_renegotiation() const { return false; }

      /**
      * The protocol dictates that the first 32 bits of the random
      * field are the current time in seconds. However this allows
      * client fingerprinting attacks. Set to false to disable, in
      * which case random bytes will be used instead.
      */
      virtual bool include_time_in_hello_random() const { return true; }

      /**
      * Allow servers to initiate a new handshake
      */
      virtual bool allow_server_initiated_renegotiation() const;

      /**
      * Return the group to use for ephemeral Diffie-Hellman key agreement
      */
      virtual DL_Group dh_group() const;

      /**
      * Return the minimum DH group size we're willing to use
      */
      virtual size_t minimum_dh_group_size() const;

      /**
      * If this function returns false, unknown SRP/PSK identifiers
      * will be rejected with an unknown_psk_identifier alert as soon
      * as the non-existence is identified. Otherwise, a false
      * identifier value will be used and the protocol allowed to
      * proceed, causing the handshake to eventually fail without
      * revealing that the username does not exist on this system.
      */
      virtual bool hide_unknown_users() const { return false; }

      /**
      * Return the allowed lifetime of a session ticket. If 0, session
      * tickets do not expire until the session ticket key rolls over.
      * Expired session tickets cannot be used to resume a session.
      */
      virtual u32bit session_ticket_lifetime() const;

      /**
      * @return true if and only if we are willing to accept this version
      * Default accepts TLS v1.0 and later.

      * Override if you want to allow negotiating SSLv3 (*not recommended*)
      * Override if you want to enable DTLS in your application.
      */
      virtual bool acceptable_protocol_version(Protocol_Version version) const;

      /**
      * Returns the more recent protocol version we are willing to
      * use, for either TLS or DTLS depending on datagram param.
      * Shouldn't ever need to override this unless you want to allow
      * a user to disable use of TLS v1.2 (which is *not recommended*)
      */
      virtual Protocol_Version latest_supported_version(bool datagram) const;

      /**
      * When offering this version, should we send a fallback SCSV?
      * Default returns true iff version is not the latest version the
      * policy allows, exists to allow override in case of interop problems.
      */
      virtual bool send_fallback_scsv(Protocol_Version version) const;

      /**
      * Allows policy to reject any ciphersuites which are undesirable
      * for whatever reason without having to reimplement ciphersuite_list
      */
      virtual bool acceptable_ciphersuite(const Ciphersuite& suite) const;

      /**
      * @return true if servers should choose the ciphersuite matching
      *         their highest preference, rather than the clients.
      *         Has no effect on client side.
      */
      virtual bool server_uses_own_ciphersuite_preferences() const { return true; }

      /**
      * Return allowed ciphersuites, in order of preference
      */
      virtual std::vector<u16bit> ciphersuite_list(Protocol_Version version,
                                                   bool have_srp) const;

      virtual ~Policy() {}
   };

/**
* NSA Suite B 128-bit security level (see @rfc 6460)
*/
class BOTAN_DLL NSA_Suite_B_128 : public Policy
   {
   public:
      std::vector<std::string> allowed_ciphers() const override
         { return std::vector<std::string>({"AES-128/GCM"}); }

      std::vector<std::string> allowed_signature_hashes() const override
         { return std::vector<std::string>({"SHA-256"}); }

      std::vector<std::string> allowed_macs() const override
         { return std::vector<std::string>({"AEAD"}); }

      std::vector<std::string> allowed_key_exchange_methods() const override
         { return std::vector<std::string>({"ECDH"}); }

      std::vector<std::string> allowed_signature_methods() const override
         { return std::vector<std::string>({"ECDSA"}); }

      std::vector<std::string> allowed_ecc_curves() const override
         { return std::vector<std::string>({"secp256r1"}); }

      bool acceptable_protocol_version(Protocol_Version version) const override
         { return version == Protocol_Version::TLS_V12; }
   };

/**
* Policy for DTLS. We require DTLS v1.2 and an AEAD mode
*/
class BOTAN_DLL Datagram_Policy : public Policy
   {
   public:
      std::vector<std::string> allowed_macs() const override
         { return std::vector<std::string>({"AEAD"}); }

      bool acceptable_protocol_version(Protocol_Version version) const override
         { return version == Protocol_Version::DTLS_V12; }
   };

}

}

#endif
