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 <pubkey.h>
10 #include <uint256.h>
11 12 #include <cstddef>
13 #include <cstdint>
14 #include <memory>
15 #include <optional>
16 #include <set>
17 #include <string>
18 #include <string_view>
19 #include <unordered_map>
20 #include <vector>
21 22 class CScript;
23 class SigningProvider;
24 struct FlatSigningProvider;
25 26 using ExtPubKeyMap = std::unordered_map<uint32_t, CExtPubKey>;
27 28 /** Cache for single descriptor's derived extended pubkeys */
29 class DescriptorCache {
30 private:
31 /** Map key expression index -> map of (key derivation index -> xpub) */
32 std::unordered_map<uint32_t, ExtPubKeyMap> m_derived_xpubs;
33 /** Map key expression index -> parent xpub */
34 ExtPubKeyMap m_parent_xpubs;
35 /** Map key expression index -> last hardened xpub */
36 ExtPubKeyMap m_last_hardened_xpubs;
37 38 public:
39 /** Cache a parent xpub
40 *
41 * @param[in] key_exp_pos Position of the key expression within the descriptor
42 * @param[in] xpub The CExtPubKey to cache
43 */
44 void CacheParentExtPubKey(uint32_t key_exp_pos, const CExtPubKey& xpub);
45 /** Retrieve a cached parent xpub
46 *
47 * @param[in] key_exp_pos Position of the key expression within the descriptor
48 * @param[out] xpub The CExtPubKey to get from cache
49 */
50 bool GetCachedParentExtPubKey(uint32_t key_exp_pos, CExtPubKey& xpub) const;
51 /** Cache an xpub derived at an index
52 *
53 * @param[in] key_exp_pos Position of the key expression within the descriptor
54 * @param[in] der_index Derivation index of the xpub
55 * @param[in] xpub The CExtPubKey to cache
56 */
57 void CacheDerivedExtPubKey(uint32_t key_exp_pos, uint32_t der_index, const CExtPubKey& xpub);
58 /** Retrieve a cached xpub derived at an index
59 *
60 * @param[in] key_exp_pos Position of the key expression within the descriptor
61 * @param[in] der_index Derivation index of the xpub
62 * @param[out] xpub The CExtPubKey to get from cache
63 */
64 bool GetCachedDerivedExtPubKey(uint32_t key_exp_pos, uint32_t der_index, CExtPubKey& xpub) const;
65 /** Cache a last hardened xpub
66 *
67 * @param[in] key_exp_pos Position of the key expression within the descriptor
68 * @param[in] xpub The CExtPubKey to cache
69 */
70 void CacheLastHardenedExtPubKey(uint32_t key_exp_pos, const CExtPubKey& xpub);
71 /** Retrieve a cached last hardened xpub
72 *
73 * @param[in] key_exp_pos Position of the key expression within the descriptor
74 * @param[out] xpub The CExtPubKey to get from cache
75 */
76 bool GetCachedLastHardenedExtPubKey(uint32_t key_exp_pos, CExtPubKey& xpub) const;
77 78 /** Retrieve all cached parent xpubs */
79 ExtPubKeyMap GetCachedParentExtPubKeys() const;
80 /** Retrieve all cached derived xpubs */
81 std::unordered_map<uint32_t, ExtPubKeyMap> GetCachedDerivedExtPubKeys() const;
82 /** Retrieve all cached last hardened xpubs */
83 ExtPubKeyMap GetCachedLastHardenedExtPubKeys() const;
84 85 /** Combine another DescriptorCache into this one.
86 * Returns a cache containing the items from the other cache unknown to current cache
87 */
88 DescriptorCache MergeAndDiff(const DescriptorCache& other);
89 };
90 91 /** \brief Interface for parsed descriptor objects.
92 *
93 * Descriptors are strings that describe a set of scriptPubKeys, together with
94 * all information necessary to solve them. By combining all information into
95 * one, they avoid the need to separately import keys and scripts.
96 *
97 * Descriptors may be ranged, which occurs when the public keys inside are
98 * specified in the form of HD chains (xpubs).
99 *
100 * Descriptors always represent public information - public keys and scripts -
101 * but in cases where private keys need to be conveyed along with a descriptor,
102 * they can be included inside by changing public keys to private keys (WIF
103 * format), and changing xpubs by xprvs.
104 *
105 * Reference documentation about the descriptor language can be found in
106 * doc/descriptors.md.
107 */
108 struct Descriptor {
109 virtual ~Descriptor() = default;
110 111 /** Whether the expansion of this descriptor depends on the position. */
112 virtual bool IsRange() const = 0;
113 114 /** Whether this descriptor has all information about signing ignoring lack of private keys.
115 * This is true for all descriptors except ones that use `raw` or `addr` constructions. */
116 virtual bool IsSolvable() const = 0;
117 118 /** Convert the descriptor back to a string, undoing parsing. */
119 virtual std::string ToString(bool compat_format=false) const = 0;
120 121 /** Whether this descriptor will return at most one scriptPubKey or multiple (aka is or is not combo) */
122 virtual bool IsSingleType() const = 0;
123 124 /** Whether the given provider has all private keys required by this descriptor.
125 * @return `false` if the descriptor doesn't have any keys or subdescriptors,
126 * or if the provider does not have all private keys required by
127 * the descriptor.
128 */
129 virtual bool HavePrivateKeys(const SigningProvider& provider) const = 0;
130 131 /** Convert the descriptor to a private string. This uses public keys if the relevant private keys are not in the SigningProvider.
132 * If none of the relevant private keys are available, the output string in the "out" parameter will not contain any private key information,
133 * and this function will return "false".
134 * @param[in] provider The SigningProvider to query for private keys.
135 * @param[out] out The resulting descriptor string, containing private keys if available.
136 * @returns true if at least one private key available.
137 */
138 virtual bool ToPrivateString(const SigningProvider& provider, std::string& out) const = 0;
139 140 /** 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. */
141 virtual bool ToNormalizedString(const SigningProvider& provider, std::string& out, const DescriptorCache* cache = nullptr) const = 0;
142 143 /** Whether the descriptor can be used to produce its address(es) without needing a cache or private keys. */
144 virtual bool CanSelfExpand() const = 0;
145 146 /** Expand a descriptor at a specified position.
147 *
148 * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
149 * @param[in] provider The provider to query for private keys in case of hardened derivation.
150 * @param[out] output_scripts The expanded scriptPubKeys.
151 * @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`).
152 * @param[out] write_cache Cache data necessary to evaluate the descriptor at this point without access to private keys.
153 */
154 virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache = nullptr) const = 0;
155 156 /** Expand a descriptor at a specified position using cached expansion data.
157 *
158 * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
159 * @param[in] read_cache Cached expansion data.
160 * @param[out] output_scripts The expanded scriptPubKeys.
161 * @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`).
162 */
163 virtual bool ExpandFromCache(int pos, const DescriptorCache& read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const = 0;
164 165 /** Expand the private key for a descriptor at a specified position, if possible.
166 *
167 * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
168 * @param[in] provider The provider to query for the private keys.
169 * @param[out] out Any private keys available for the specified `pos`.
170 */
171 virtual void ExpandPrivate(int pos, const SigningProvider& provider, FlatSigningProvider& out) const = 0;
172 173 /** @return The OutputType of the scriptPubKey(s) produced by this descriptor. Or nullopt if indeterminate (multiple or none) */
174 virtual std::optional<OutputType> GetOutputType() const = 0;
175 176 /** Get the size of the scriptPubKey for this descriptor. */
177 virtual std::optional<int64_t> ScriptSize() const = 0;
178 179 /** Get the maximum size of a satisfaction for this descriptor, in weight units.
180 *
181 * @param use_max_sig Whether to assume ECDSA signatures will have a high-r.
182 */
183 virtual std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const = 0;
184 185 /** Get the maximum size number of stack elements for satisfying this descriptor. */
186 virtual std::optional<int64_t> MaxSatisfactionElems() const = 0;
187 188 /** Return all (extended) public keys for this descriptor, including any from subdescriptors.
189 *
190 * @param[out] pubkeys Any public keys
191 * @param[out] ext_pubs Any extended public keys
192 */
193 virtual void GetPubKeys(std::set<CPubKey>& pubkeys, std::set<CExtPubKey>& ext_pubs) const = 0;
194 195 /** Whether this descriptor produces any scripts with the Expand functions */
196 virtual bool HasScripts() const = 0;
197 198 /** Semantic/safety warnings (includes subdescriptors). */
199 virtual std::vector<std::string> Warnings() const = 0;
200 201 /** Get the maximum key expression index. Used only for tests */
202 virtual uint32_t GetMaxKeyExpr() const = 0;
203 204 /** Get the number of key expressions in this descriptor. Used only for tests */
205 virtual size_t GetKeyCount() const = 0;
206 };
207 208 /** Parse a `descriptor` string. Included private keys are put in `out`.
209 *
210 * If the descriptor has a checksum, it must be valid. If `require_checksum`
211 * is set, the checksum is mandatory - otherwise it is optional.
212 *
213 * If a parse error occurs, or the checksum is missing/invalid, or anything
214 * else is wrong, an empty vector is returned.
215 */
216 std::vector<std::unique_ptr<Descriptor>> Parse(std::string_view descriptor, FlatSigningProvider& out, std::string& error, bool require_checksum = false);
217 218 /** Get the checksum for a `descriptor`.
219 *
220 * - If it already has one, and it is correct, return the checksum in the input.
221 * - If it already has one that is wrong, return "".
222 * - If it does not already have one, return the checksum that would need to be added.
223 */
224 std::string GetDescriptorChecksum(const std::string& descriptor);
225 226 /** Find a descriptor for the specified `script`, using information from `provider` where possible.
227 *
228 * A non-ranged descriptor which only generates the specified script will be returned in all
229 * circumstances.
230 *
231 * For public keys with key origin information, this information will be preserved in the returned
232 * descriptor.
233 *
234 * - If all information for solving `script` is present in `provider`, a descriptor will be returned
235 * which is IsSolvable() and encapsulates said information.
236 * - Failing that, if `script` corresponds to a known address type, an "addr()" descriptor will be
237 * returned (which is not IsSolvable()).
238 * - Failing that, a "raw()" descriptor is returned.
239 */
240 std::unique_ptr<Descriptor> InferDescriptor(const CScript& script, const SigningProvider& provider);
241 242 /** Unique identifier that may not change over time, unless explicitly marked as not backwards compatible.
243 * This is not part of BIP 380, not guaranteed to be interoperable and should not be exposed to the user.
244 */
245 uint256 DescriptorID(const Descriptor& desc);
246 247 #endif // BITCOIN_SCRIPT_DESCRIPTOR_H
248