descriptor.h
1 // Copyright (c) 2018-present 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 /** Whether the given provider has all private keys required by this descriptor. 115 * @return `false` if the descriptor doesn't have any keys or subdescriptors, 116 * or if the provider does not have all private keys required by 117 * the descriptor. 118 */ 119 virtual bool HavePrivateKeys(const SigningProvider& provider) const = 0; 120 121 /** Convert the descriptor to a private string. This uses public keys if the relevant private keys are not in the SigningProvider. 122 * If none of the relevant private keys are available, the output string in the "out" parameter will not contain any private key information, 123 * and this function will return "false". 124 * @param[in] provider The SigningProvider to query for private keys. 125 * @param[out] out The resulting descriptor string, containing private keys if available. 126 * @returns true if at least one private key available. 127 */ 128 virtual bool ToPrivateString(const SigningProvider& provider, std::string& out) const = 0; 129 130 /** 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. */ 131 virtual bool ToNormalizedString(const SigningProvider& provider, std::string& out, const DescriptorCache* cache = nullptr) const = 0; 132 133 /** Expand a descriptor at a specified position. 134 * 135 * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored. 136 * @param[in] provider The provider to query for private keys in case of hardened derivation. 137 * @param[out] output_scripts The expanded scriptPubKeys. 138 * @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`). 139 * @param[out] write_cache Cache data necessary to evaluate the descriptor at this point without access to private keys. 140 */ 141 virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache = nullptr) const = 0; 142 143 /** Expand a descriptor at a specified position using cached expansion data. 144 * 145 * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored. 146 * @param[in] read_cache Cached expansion data. 147 * @param[out] output_scripts The expanded scriptPubKeys. 148 * @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`). 149 */ 150 virtual bool ExpandFromCache(int pos, const DescriptorCache& read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const = 0; 151 152 /** Expand the private key for a descriptor at a specified position, if possible. 153 * 154 * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored. 155 * @param[in] provider The provider to query for the private keys. 156 * @param[out] out Any private keys available for the specified `pos`. 157 */ 158 virtual void ExpandPrivate(int pos, const SigningProvider& provider, FlatSigningProvider& out) const = 0; 159 160 /** @return The OutputType of the scriptPubKey(s) produced by this descriptor. Or nullopt if indeterminate (multiple or none) */ 161 virtual std::optional<OutputType> GetOutputType() const = 0; 162 163 /** Get the size of the scriptPubKey for this descriptor. */ 164 virtual std::optional<int64_t> ScriptSize() const = 0; 165 166 /** Get the maximum size of a satisfaction for this descriptor, in weight units. 167 * 168 * @param use_max_sig Whether to assume ECDSA signatures will have a high-r. 169 */ 170 virtual std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const = 0; 171 172 /** Get the maximum size number of stack elements for satisfying this descriptor. */ 173 virtual std::optional<int64_t> MaxSatisfactionElems() const = 0; 174 175 /** Return all (extended) public keys for this descriptor, including any from subdescriptors. 176 * 177 * @param[out] pubkeys Any public keys 178 * @param[out] ext_pubs Any extended public keys 179 */ 180 virtual void GetPubKeys(std::set<CPubKey>& pubkeys, std::set<CExtPubKey>& ext_pubs) const = 0; 181 182 /** Semantic/safety warnings (includes subdescriptors). */ 183 virtual std::vector<std::string> Warnings() const = 0; 184 185 /** Get the maximum key expression index. Used only for tests */ 186 virtual uint32_t GetMaxKeyExpr() const = 0; 187 188 /** Get the number of key expressions in this descriptor. Used only for tests */ 189 virtual size_t GetKeyCount() const = 0; 190 }; 191 192 /** Parse a `descriptor` string. Included private keys are put in `out`. 193 * 194 * If the descriptor has a checksum, it must be valid. If `require_checksum` 195 * is set, the checksum is mandatory - otherwise it is optional. 196 * 197 * If a parse error occurs, or the checksum is missing/invalid, or anything 198 * else is wrong, an empty vector is returned. 199 */ 200 std::vector<std::unique_ptr<Descriptor>> Parse(std::string_view descriptor, FlatSigningProvider& out, std::string& error, bool require_checksum = false); 201 202 /** Get the checksum for a `descriptor`. 203 * 204 * - If it already has one, and it is correct, return the checksum in the input. 205 * - If it already has one that is wrong, return "". 206 * - If it does not already have one, return the checksum that would need to be added. 207 */ 208 std::string GetDescriptorChecksum(const std::string& descriptor); 209 210 /** Find a descriptor for the specified `script`, using information from `provider` where possible. 211 * 212 * A non-ranged descriptor which only generates the specified script will be returned in all 213 * circumstances. 214 * 215 * For public keys with key origin information, this information will be preserved in the returned 216 * descriptor. 217 * 218 * - If all information for solving `script` is present in `provider`, a descriptor will be returned 219 * which is IsSolvable() and encapsulates said information. 220 * - Failing that, if `script` corresponds to a known address type, an "addr()" descriptor will be 221 * returned (which is not IsSolvable()). 222 * - Failing that, a "raw()" descriptor is returned. 223 */ 224 std::unique_ptr<Descriptor> InferDescriptor(const CScript& script, const SigningProvider& provider); 225 226 /** Unique identifier that may not change over time, unless explicitly marked as not backwards compatible. 227 * This is not part of BIP 380, not guaranteed to be interoperable and should not be exposed to the user. 228 */ 229 uint256 DescriptorID(const Descriptor& desc); 230 231 #endif // BITCOIN_SCRIPT_DESCRIPTOR_H