1  // Copyright (c) 2018-2021 The Bitcoin Core developers
  2  // Distributed under the MIT software license, see the accompanying
  3  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  4  
  5  #ifndef BITCOIN_SCRIPT_DESCRIPTOR_H
  6  #define BITCOIN_SCRIPT_DESCRIPTOR_H
  7  
  8  #include <outputtype.h>
  9  #include <script/script.h>
 10  #include <script/sign.h>
 11  #include <script/signingprovider.h>
 12  
 13  #include <optional>
 14  #include <vector>
 15  
 16  using ExtPubKeyMap = std::unordered_map<uint32_t, CExtPubKey>;
 17  
 18  /** Cache for single descriptor's derived extended pubkeys */
 19  class DescriptorCache {
 20  private:
 21      /** Map key expression index -> map of (key derivation index -> xpub) */
 22      std::unordered_map<uint32_t, ExtPubKeyMap> m_derived_xpubs;
 23      /** Map key expression index -> parent xpub */
 24      ExtPubKeyMap m_parent_xpubs;
 25      /** Map key expression index -> last hardened xpub */
 26      ExtPubKeyMap m_last_hardened_xpubs;
 27  
 28  public:
 29      /** Cache a parent xpub
 30       *
 31       * @param[in] key_exp_pos Position of the key expression within the descriptor
 32       * @param[in] xpub The CExtPubKey to cache
 33       */
 34      void CacheParentExtPubKey(uint32_t key_exp_pos, const CExtPubKey& xpub);
 35      /** Retrieve a cached parent xpub
 36       *
 37       * @param[in] key_exp_pos Position of the key expression within the descriptor
 38       * @param[out] xpub The CExtPubKey to get from cache
 39       */
 40      bool GetCachedParentExtPubKey(uint32_t key_exp_pos, CExtPubKey& xpub) const;
 41      /** Cache an xpub derived at an index
 42       *
 43       * @param[in] key_exp_pos Position of the key expression within the descriptor
 44       * @param[in] der_index Derivation index of the xpub
 45       * @param[in] xpub The CExtPubKey to cache
 46       */
 47      void CacheDerivedExtPubKey(uint32_t key_exp_pos, uint32_t der_index, const CExtPubKey& xpub);
 48      /** Retrieve a cached xpub derived at an index
 49       *
 50       * @param[in] key_exp_pos Position of the key expression within the descriptor
 51       * @param[in] der_index Derivation index of the xpub
 52       * @param[out] xpub The CExtPubKey to get from cache
 53       */
 54      bool GetCachedDerivedExtPubKey(uint32_t key_exp_pos, uint32_t der_index, CExtPubKey& xpub) const;
 55      /** Cache a last hardened xpub
 56       *
 57       * @param[in] key_exp_pos Position of the key expression within the descriptor
 58       * @param[in] xpub The CExtPubKey to cache
 59       */
 60      void CacheLastHardenedExtPubKey(uint32_t key_exp_pos, const CExtPubKey& xpub);
 61      /** Retrieve a cached last hardened xpub
 62       *
 63       * @param[in] key_exp_pos Position of the key expression within the descriptor
 64       * @param[out] xpub The CExtPubKey to get from cache
 65       */
 66      bool GetCachedLastHardenedExtPubKey(uint32_t key_exp_pos, CExtPubKey& xpub) const;
 67  
 68      /** Retrieve all cached parent xpubs */
 69      ExtPubKeyMap GetCachedParentExtPubKeys() const;
 70      /** Retrieve all cached derived xpubs */
 71      std::unordered_map<uint32_t, ExtPubKeyMap> GetCachedDerivedExtPubKeys() const;
 72      /** Retrieve all cached last hardened xpubs */
 73      ExtPubKeyMap GetCachedLastHardenedExtPubKeys() const;
 74  
 75      /** Combine another DescriptorCache into this one.
 76       * Returns a cache containing the items from the other cache unknown to current cache
 77       */
 78      DescriptorCache MergeAndDiff(const DescriptorCache& other);
 79  };
 80  
 81  /** \brief Interface for parsed descriptor objects.
 82   *
 83   * Descriptors are strings that describe a set of scriptPubKeys, together with
 84   * all information necessary to solve them. By combining all information into
 85   * one, they avoid the need to separately import keys and scripts.
 86   *
 87   * Descriptors may be ranged, which occurs when the public keys inside are
 88   * specified in the form of HD chains (xpubs).
 89   *
 90   * Descriptors always represent public information - public keys and scripts -
 91   * but in cases where private keys need to be conveyed along with a descriptor,
 92   * they can be included inside by changing public keys to private keys (WIF
 93   * format), and changing xpubs by xprvs.
 94   *
 95   * Reference documentation about the descriptor language can be found in
 96   * doc/descriptors.md.
 97   */
 98  struct Descriptor {
 99      virtual ~Descriptor() = default;
100  
101      /** Whether the expansion of this descriptor depends on the position. */
102      virtual bool IsRange() const = 0;
103  
104      /** Whether this descriptor has all information about signing ignoring lack of private keys.
105       *  This is true for all descriptors except ones that use `raw` or `addr` constructions. */
106      virtual bool IsSolvable() const = 0;
107  
108      /** Convert the descriptor back to a string, undoing parsing. */
109      virtual std::string ToString(bool compat_format=false) const = 0;
110  
111      /** Whether this descriptor will return one scriptPubKey or multiple (aka is or is not combo) */
112      virtual bool IsSingleType() const = 0;
113  
114      /** Convert the descriptor to a private string. This fails if the provided provider does not have the relevant private keys. */
115      virtual bool ToPrivateString(const SigningProvider& provider, std::string& out) const = 0;
116  
117      /** Convert the descriptor to a normalized string. Normalized descriptors have the xpub at the last hardened step. This fails if the provided provider does not have the private keys to derive that xpub. */
118      virtual bool ToNormalizedString(const SigningProvider& provider, std::string& out, const DescriptorCache* cache = nullptr) const = 0;
119  
120      /** Expand a descriptor at a specified position.
121       *
122       * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
123       * @param[in] provider The provider to query for private keys in case of hardened derivation.
124       * @param[out] output_scripts The expanded scriptPubKeys.
125       * @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`).
126       * @param[out] write_cache Cache data necessary to evaluate the descriptor at this point without access to private keys.
127       */
128      virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache = nullptr) const = 0;
129  
130      /** Expand a descriptor at a specified position using cached expansion data.
131       *
132       * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
133       * @param[in] read_cache Cached expansion data.
134       * @param[out] output_scripts The expanded scriptPubKeys.
135       * @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`).
136       */
137      virtual bool ExpandFromCache(int pos, const DescriptorCache& read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const = 0;
138  
139      /** Expand the private key for a descriptor at a specified position, if possible.
140       *
141       * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
142       * @param[in] provider The provider to query for the private keys.
143       * @param[out] out Any private keys available for the specified `pos`.
144       */
145      virtual void ExpandPrivate(int pos, const SigningProvider& provider, FlatSigningProvider& out) const = 0;
146  
147      /** @return The OutputType of the scriptPubKey(s) produced by this descriptor. Or nullopt if indeterminate (multiple or none) */
148      virtual std::optional<OutputType> GetOutputType() const = 0;
149  
150      /** Get the size of the scriptPubKey for this descriptor. */
151      virtual std::optional<int64_t> ScriptSize() const = 0;
152  
153      /** Get the maximum size of a satisfaction for this descriptor, in weight units.
154       *
155       * @param use_max_sig Whether to assume ECDSA signatures will have a high-r.
156       */
157      virtual std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const = 0;
158  
159      /** Get the maximum size number of stack elements for satisfying this descriptor. */
160      virtual std::optional<int64_t> MaxSatisfactionElems() const = 0;
161  };
162  
163  /** Parse a `descriptor` string. Included private keys are put in `out`.
164   *
165   * If the descriptor has a checksum, it must be valid. If `require_checksum`
166   * is set, the checksum is mandatory - otherwise it is optional.
167   *
168   * If a parse error occurs, or the checksum is missing/invalid, or anything
169   * else is wrong, `nullptr` is returned.
170   */
171  std::unique_ptr<Descriptor> Parse(const std::string& descriptor, FlatSigningProvider& out, std::string& error, bool require_checksum = false);
172  
173  /** Get the checksum for a `descriptor`.
174   *
175   * - If it already has one, and it is correct, return the checksum in the input.
176   * - If it already has one that is wrong, return "".
177   * - If it does not already have one, return the checksum that would need to be added.
178   */
179  std::string GetDescriptorChecksum(const std::string& descriptor);
180  
181  /** Find a descriptor for the specified `script`, using information from `provider` where possible.
182   *
183   * A non-ranged descriptor which only generates the specified script will be returned in all
184   * circumstances.
185   *
186   * For public keys with key origin information, this information will be preserved in the returned
187   * descriptor.
188   *
189   * - If all information for solving `script` is present in `provider`, a descriptor will be returned
190   *   which is IsSolvable() and encapsulates said information.
191   * - Failing that, if `script` corresponds to a known address type, an "addr()" descriptor will be
192   *   returned (which is not IsSolvable()).
193   * - Failing that, a "raw()" descriptor is returned.
194   */
195  std::unique_ptr<Descriptor> InferDescriptor(const CScript& script, const SigningProvider& provider);
196  
197  /** Unique identifier that may not change over time, unless explicitly marked as not backwards compatible.
198  *   This is not part of BIP 380, not guaranteed to be interoperable and should not be exposed to the user.
199  */
200  uint256 DescriptorID(const Descriptor& desc);
201  
202  #endif // BITCOIN_SCRIPT_DESCRIPTOR_H