Line data    Source code

       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           0 : 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           0 :     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