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       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