Coverage Report

Created: 2020-05-23 13:54

/src/botan/build/include/botan/xmss_privatekey.h
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/*
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 * XMSS_PrivateKey.h
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 * (C) 2016,2017,2018 Matthias Gierlings
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 *
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 * Botan is released under the Simplified BSD License (see license.txt)
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 **/
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#ifndef BOTAN_XMSS_PRIVATEKEY_H_
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#define BOTAN_XMSS_PRIVATEKEY_H_
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#include <cstddef>
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#include <iterator>
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#include <memory>
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#include <botan/alg_id.h>
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#include <botan/exceptn.h>
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#include <botan/pk_keys.h>
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#include <botan/types.h>
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#include <botan/xmss_parameters.h>
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#include <botan/xmss_publickey.h>
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#include <botan/atomic.h>
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#include <botan/xmss_wots_privatekey.h>
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#include <botan/xmss_index_registry.h>
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namespace Botan {
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/**
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 * An XMSS: Extended Hash-Based Signature private key.
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 * The XMSS private key does not support the X509 and PKCS7 standard. Instead
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 * the raw format described in [1] is used.
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 *
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 * [1] XMSS: Extended Hash-Based Signatures,
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 *     Request for Comments: 8391
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 *     Release: May 2018.
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 *     https://datatracker.ietf.org/doc/rfc8391/
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 **/
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class BOTAN_PUBLIC_API(2,0) XMSS_PrivateKey final : public virtual XMSS_PublicKey,
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   public virtual Private_Key
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   {
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   public:
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      /**
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      * Creates a new XMSS private key for the chosen XMSS signature method.
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      * New seeds for public/private key and pseudo random function input are
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      * generated using the provided RNG. The appropriate WOTS signature method
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      * will be automatically set based on the chosen XMSS signature method.
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      *
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      * @param xmss_algo_id Identifier for the selected XMSS signature method.
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      * @param rng A random number generator to use for key generation.
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      **/
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      XMSS_PrivateKey(XMSS_Parameters::xmss_algorithm_t xmss_algo_id,
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                      RandomNumberGenerator& rng);
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      /**
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       * Creates an XMSS_PrivateKey from a byte sequence produced by
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       * raw_private_key().
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       *
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       * @param raw_key An XMSS private key serialized using raw_private_key().
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       **/
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      XMSS_PrivateKey(const secure_vector<uint8_t>& raw_key);
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      /**
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       * Creates a new XMSS private key for the chosen XMSS signature method
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       * using precomputed seeds for public/private keys and pseudo random
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       * function input. The appropriate WOTS signature method will be
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       * automatically set, based on the chosen XMSS signature method.
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       *
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       * @param xmss_algo_id Identifier for the selected XMSS signature method.
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       * @param idx_leaf Index of the next unused leaf.
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       * @param wots_priv_seed A seed to generate a Winternitz-One-Time-
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       *                      Signature private key from.
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       * @param prf a secret n-byte key sourced from a secure source
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       *        of uniformly random data.
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       * @param root Root node of the binary hash tree.
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       * @param public_seed The public seed.
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       **/
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      XMSS_PrivateKey(XMSS_Parameters::xmss_algorithm_t xmss_algo_id,
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                      size_t idx_leaf,
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                      const secure_vector<uint8_t>& wots_priv_seed,
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                      const secure_vector<uint8_t>& prf,
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                      const secure_vector<uint8_t>& root,
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                      const secure_vector<uint8_t>& public_seed)
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         : XMSS_PublicKey(xmss_algo_id, root, public_seed),
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           m_wots_priv_key(XMSS_PublicKey::m_xmss_params.ots_oid(),
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                           public_seed,
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                           wots_priv_seed),
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           m_hash(XMSS_PublicKey::m_xmss_params.hash_function_name()),
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           m_prf(prf),
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           m_index_reg(XMSS_Index_Registry::get_instance())
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         {
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         set_unused_leaf_index(idx_leaf);
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         }
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      bool stateful_operation() const override { return true; }
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      /**
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       * Retrieves the last unused leaf index of the private key. Reusing a leaf
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       * by utilizing leaf indices lower than the last unused leaf index will
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       * compromise security.
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       *
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       * @return Index of the last unused leaf.
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       **/
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      size_t unused_leaf_index() const
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         {
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         return *recover_global_leaf_index();
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         }
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      /**
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       * Sets the last unused leaf index of the private key. The leaf index
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       * will be updated automatically during every signing operation, and
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       * should not be set manually.
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       *
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       * @param idx Index of the last unused leaf.
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       **/
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      void set_unused_leaf_index(size_t idx)
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         {
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         if(idx >= (1ull << XMSS_PublicKey::m_xmss_params.tree_height()))
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            {
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            throw Decoding_Error("XMSS private key leaf index out of bounds");
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            }
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         else
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            {
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            std::atomic<size_t>& index =
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               static_cast<std::atomic<size_t>&>(*recover_global_leaf_index());
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            size_t current = 0;
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            do
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               {
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               current = index.load();
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               if(current > idx)
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                  { return; }
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               }
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            while(!index.compare_exchange_strong(current, idx));
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            }
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         }
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      size_t reserve_unused_leaf_index()
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         {
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         size_t idx = (static_cast<std::atomic<size_t>&>(
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                          *recover_global_leaf_index())).fetch_add(1);
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         if(idx >= (1ull << XMSS_PublicKey::m_xmss_params.tree_height()))
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            {
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            throw Decoding_Error("XMSS private key, one time signatures exhaused");
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            }
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         return idx;
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         }
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      /**
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       * Winternitz One Time Signature Scheme key utilized for signing
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       * operations.
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       *
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       * @return WOTS+ private key.
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       **/
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      const XMSS_WOTS_PrivateKey& wots_private_key() const
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         {
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         return m_wots_priv_key;
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         }
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      /**
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       * Winternitz One Time Signature Scheme key utilized for signing
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       * operations.
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       *
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       * @return WOTS+ private key.
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       **/
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      XMSS_WOTS_PrivateKey& wots_private_key()
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         {
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         return m_wots_priv_key;
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         }
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      const secure_vector<uint8_t>& prf() const
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         {
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         return m_prf;
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         }
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      secure_vector<uint8_t>& prf()
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         {
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         return m_prf;
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         }
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      void set_public_seed(
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         const secure_vector<uint8_t>& public_seed) override
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         {
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         m_public_seed = public_seed;
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         m_wots_priv_key.set_public_seed(public_seed);
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         }
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      void set_public_seed(secure_vector<uint8_t>&& public_seed) override
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         {
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         m_public_seed = std::move(public_seed);
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         m_wots_priv_key.set_public_seed(m_public_seed);
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         }
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      const secure_vector<uint8_t>& public_seed() const override
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         {
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         return m_public_seed;
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         }
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      std::unique_ptr<PK_Ops::Signature>
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      create_signature_op(RandomNumberGenerator&,
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                          const std::string&,
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                          const std::string& provider) const override;
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      secure_vector<uint8_t> private_key_bits() const override
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         {
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         return DER_Encoder().encode(raw_private_key(), OCTET_STRING).get_contents();
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         }
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      size_t size() const override
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         {
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         return XMSS_PublicKey::size() +
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                sizeof(uint32_t) +
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                2 * XMSS_PublicKey::m_xmss_params.element_size();
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         }
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      /**
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       * Generates a non standartized byte sequence representing the XMSS
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       * private key.
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       *
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       * @return byte sequence consisting of the following elements in order:
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       *         4-byte OID, n-byte root node, n-byte public seed,
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       *         8-byte unused leaf index, n-byte prf seed, n-byte private seed.
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       **/
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      secure_vector<uint8_t> raw_private_key() const;
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      /**
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       * Algorithm 9: "treeHash"
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       * Computes the internal n-byte nodes of a Merkle tree.
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       *
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       * @param start_idx The start index.
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       * @param target_node_height Height of the target node.
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       * @param adrs Address of the tree containing the target node.
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       *
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       * @return The root node of a tree of height target_node height with the
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       *         leftmost leaf being the hash of the WOTS+ pk with index
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       *         start_idx.
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       **/
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      secure_vector<uint8_t> tree_hash(
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         size_t start_idx,
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         size_t target_node_height,
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         XMSS_Address& adrs);
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   private:
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      /**
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       * Fetches shared unused leaf index from the index registry
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       **/
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      std::shared_ptr<Atomic<size_t>> recover_global_leaf_index() const;
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      inline void tree_hash_subtree(secure_vector<uint8_t>& result,
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                                    size_t start_idx,
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                                    size_t target_node_height,
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                                    XMSS_Address& adrs)
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         {
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         return tree_hash_subtree(result, start_idx, target_node_height, adrs, m_hash);
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         }
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      /**
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       * Helper for multithreaded tree hashing.
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       */
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      void tree_hash_subtree(secure_vector<uint8_t>& result,
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                             size_t start_idx,
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                             size_t target_node_height,
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                             XMSS_Address& adrs,
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                             XMSS_Hash& hash);
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      XMSS_WOTS_PrivateKey m_wots_priv_key;
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      XMSS_Hash m_hash;
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      secure_vector<uint8_t> m_prf;
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      XMSS_Index_Registry& m_index_reg;
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   };
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}
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#endif
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