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| 1 | +use bitcoin::psbt::{GetKey, GetKeyError, KeyRequest}; |
| 2 | +use bitcoin::secp256k1::{Secp256k1, Signing}; |
| 3 | +use bitcoin::PrivateKey; |
| 4 | + |
| 5 | +use crate::descriptor::{DescriptorSecretKey, KeyMap}; |
| 6 | +use crate::BTreeMap; |
| 7 | + |
| 8 | +/// A wrapper around KeyMap that implements GetKey for PSBT signing. |
| 9 | +#[derive(Debug, Clone, Eq, PartialEq)] |
| 10 | +pub struct KeyMapWrapper { |
| 11 | + map: KeyMap, |
| 12 | +} |
| 13 | + |
| 14 | +impl From<KeyMap> for KeyMapWrapper { |
| 15 | + fn from(map: KeyMap) -> Self { KeyMapWrapper { map } } |
| 16 | +} |
| 17 | + |
| 18 | +impl GetKey for KeyMapWrapper { |
| 19 | + type Error = GetKeyError; |
| 20 | + |
| 21 | + fn get_key<C: Signing>( |
| 22 | + &self, |
| 23 | + key_request: KeyRequest, |
| 24 | + secp: &Secp256k1<C>, |
| 25 | + ) -> Result<Option<bitcoin::PrivateKey>, Self::Error> { |
| 26 | + Ok(self |
| 27 | + .map |
| 28 | + .iter() |
| 29 | + .find_map(|(_desc_pk, desc_sk)| -> Option<PrivateKey> { |
| 30 | + match desc_sk.get_key(key_request.clone(), secp) { |
| 31 | + Ok(Some(pk)) => Some(pk), |
| 32 | + // When looking up keys in a map, we eat errors on individual keys, on |
| 33 | + // the assumption that some other key in the map might not error. |
| 34 | + Ok(None) | Err(_) => None, |
| 35 | + } |
| 36 | + })) |
| 37 | + } |
| 38 | +} |
| 39 | + |
| 40 | +impl GetKey for DescriptorSecretKey { |
| 41 | + type Error = GetKeyError; |
| 42 | + |
| 43 | + fn get_key<C: Signing>( |
| 44 | + &self, |
| 45 | + key_request: KeyRequest, |
| 46 | + secp: &Secp256k1<C>, |
| 47 | + ) -> Result<Option<PrivateKey>, Self::Error> { |
| 48 | + match (self, key_request) { |
| 49 | + (DescriptorSecretKey::Single(single_priv), key_request) => { |
| 50 | + let sk = single_priv.key; |
| 51 | + let pk = sk.public_key(secp); |
| 52 | + let pubkey_map = BTreeMap::from([(pk, sk)]); |
| 53 | + pubkey_map.get_key(key_request, secp) |
| 54 | + } |
| 55 | + (DescriptorSecretKey::XPrv(descriptor_xkey), KeyRequest::Pubkey(public_key)) => { |
| 56 | + let xpriv = descriptor_xkey |
| 57 | + .xkey |
| 58 | + .derive_priv(secp, &descriptor_xkey.derivation_path) |
| 59 | + .map_err(GetKeyError::Bip32)?; |
| 60 | + let pk = xpriv.private_key.public_key(secp); |
| 61 | + |
| 62 | + if public_key.inner.eq(&pk) { |
| 63 | + Ok(Some(xpriv.to_priv())) |
| 64 | + } else { |
| 65 | + Ok(None) |
| 66 | + } |
| 67 | + } |
| 68 | + ( |
| 69 | + DescriptorSecretKey::XPrv(descriptor_xkey), |
| 70 | + ref key_request @ KeyRequest::Bip32(ref key_source), |
| 71 | + ) => { |
| 72 | + if let Some(key) = descriptor_xkey.xkey.get_key(key_request.clone(), secp)? { |
| 73 | + return Ok(Some(key)); |
| 74 | + } |
| 75 | + |
| 76 | + if descriptor_xkey.matches(key_source, secp).is_some() { |
| 77 | + let (_, derivation_path) = key_source; |
| 78 | + return Ok(Some( |
| 79 | + descriptor_xkey |
| 80 | + .xkey |
| 81 | + .derive_priv(secp, &derivation_path) |
| 82 | + .map_err(GetKeyError::Bip32)? |
| 83 | + .to_priv(), |
| 84 | + )); |
| 85 | + } |
| 86 | + |
| 87 | + Ok(None) |
| 88 | + } |
| 89 | + (DescriptorSecretKey::XPrv(_), KeyRequest::XOnlyPubkey(_)) => { |
| 90 | + Err(GetKeyError::NotSupported) |
| 91 | + } |
| 92 | + ( |
| 93 | + desc_multi_sk @ DescriptorSecretKey::MultiXPrv(_descriptor_multi_xkey), |
| 94 | + key_request, |
| 95 | + ) => { |
| 96 | + for desc_sk in &desc_multi_sk.clone().into_single_keys() { |
| 97 | + // If any key is an error, then all of them will, so here we propagate errors with ?. |
| 98 | + if let Some(pk) = desc_sk.get_key(key_request.clone(), secp)? { |
| 99 | + return Ok(Some(pk)); |
| 100 | + } |
| 101 | + } |
| 102 | + Ok(None) |
| 103 | + } |
| 104 | + _ => Ok(None), |
| 105 | + } |
| 106 | + } |
| 107 | +} |
| 108 | + |
| 109 | +#[cfg(test)] |
| 110 | +mod tests { |
| 111 | + use core::str::FromStr; |
| 112 | + |
| 113 | + use bitcoin::bip32::{ChildNumber, DerivationPath, IntoDerivationPath, Xpriv}; |
| 114 | + |
| 115 | + use super::*; |
| 116 | + use crate::Descriptor; |
| 117 | + |
| 118 | + #[test] |
| 119 | + fn get_key_single_key() { |
| 120 | + let secp = Secp256k1::new(); |
| 121 | + |
| 122 | + let descriptor_sk_s = |
| 123 | + "[90b6a706/44'/0'/0'/0/0]cMk8gWmj1KpjdYnAWwsEDekodMYhbyYBhG8gMtCCxucJ98JzcNij"; |
| 124 | + |
| 125 | + let single = match descriptor_sk_s.parse::<DescriptorSecretKey>().unwrap() { |
| 126 | + DescriptorSecretKey::Single(single) => single, |
| 127 | + _ => panic!("unexpected DescriptorSecretKey variant"), |
| 128 | + }; |
| 129 | + |
| 130 | + let want_sk = single.key; |
| 131 | + let descriptor_s = format!("wpkh({})", descriptor_sk_s); |
| 132 | + let (_, keymap) = Descriptor::parse_descriptor(&secp, &descriptor_s).unwrap(); |
| 133 | + let keymap_wrapper = KeyMapWrapper::from(keymap); |
| 134 | + |
| 135 | + let pk = want_sk.public_key(&secp); |
| 136 | + let request = KeyRequest::Pubkey(pk); |
| 137 | + let got_sk = keymap_wrapper |
| 138 | + .get_key(request, &secp) |
| 139 | + .expect("get_key call errored") |
| 140 | + .expect("failed to find the key"); |
| 141 | + assert_eq!(got_sk, want_sk) |
| 142 | + } |
| 143 | + |
| 144 | + #[test] |
| 145 | + fn get_key_xpriv_single_key_xpriv() { |
| 146 | + let secp = Secp256k1::new(); |
| 147 | + |
| 148 | + let s = "xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi"; |
| 149 | + |
| 150 | + let xpriv = s.parse::<Xpriv>().unwrap(); |
| 151 | + let xpriv_fingerprint = xpriv.fingerprint(&secp); |
| 152 | + |
| 153 | + // Sanity check. |
| 154 | + { |
| 155 | + let descriptor_sk_s = format!("[{}]{}", xpriv_fingerprint, xpriv); |
| 156 | + let descriptor_sk = descriptor_sk_s.parse::<DescriptorSecretKey>().unwrap(); |
| 157 | + let got = match descriptor_sk { |
| 158 | + DescriptorSecretKey::XPrv(x) => x.xkey, |
| 159 | + _ => panic!("unexpected DescriptorSecretKey variant"), |
| 160 | + }; |
| 161 | + assert_eq!(got, xpriv); |
| 162 | + } |
| 163 | + |
| 164 | + let want_sk = xpriv.to_priv(); |
| 165 | + let descriptor_s = format!("wpkh([{}]{})", xpriv_fingerprint, xpriv); |
| 166 | + let (_, keymap) = Descriptor::parse_descriptor(&secp, &descriptor_s).unwrap(); |
| 167 | + let keymap_wrapper = KeyMapWrapper::from(keymap); |
| 168 | + |
| 169 | + let pk = want_sk.public_key(&secp); |
| 170 | + let request = KeyRequest::Pubkey(pk); |
| 171 | + let got_sk = keymap_wrapper |
| 172 | + .get_key(request, &secp) |
| 173 | + .expect("get_key call errored") |
| 174 | + .expect("failed to find the key"); |
| 175 | + assert_eq!(got_sk, want_sk) |
| 176 | + } |
| 177 | + |
| 178 | + #[test] |
| 179 | + fn get_key_xpriv_child_depth_one() { |
| 180 | + let secp = Secp256k1::new(); |
| 181 | + |
| 182 | + let s = "xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi"; |
| 183 | + let master = s.parse::<Xpriv>().unwrap(); |
| 184 | + let master_fingerprint = master.fingerprint(&secp); |
| 185 | + |
| 186 | + let child_number = ChildNumber::from_hardened_idx(44).unwrap(); |
| 187 | + let child = master.derive_priv(&secp, &[child_number]).unwrap(); |
| 188 | + |
| 189 | + // Sanity check. |
| 190 | + { |
| 191 | + let descriptor_sk_s = format!("[{}/44']{}", master_fingerprint, child); |
| 192 | + let descriptor_sk = descriptor_sk_s.parse::<DescriptorSecretKey>().unwrap(); |
| 193 | + let got = match descriptor_sk { |
| 194 | + DescriptorSecretKey::XPrv(ref x) => x.xkey, |
| 195 | + _ => panic!("unexpected DescriptorSecretKey variant"), |
| 196 | + }; |
| 197 | + assert_eq!(got, child); |
| 198 | + } |
| 199 | + |
| 200 | + let want_sk = child.to_priv(); |
| 201 | + let descriptor_s = format!("wpkh({}/44')", s); |
| 202 | + let (_, keymap) = Descriptor::parse_descriptor(&secp, &descriptor_s).unwrap(); |
| 203 | + let keymap_wrapper = KeyMapWrapper::from(keymap); |
| 204 | + |
| 205 | + let pk = want_sk.public_key(&secp); |
| 206 | + let request = KeyRequest::Pubkey(pk); |
| 207 | + let got_sk = keymap_wrapper |
| 208 | + .get_key(request, &secp) |
| 209 | + .expect("get_key call errored") |
| 210 | + .expect("failed to find the key"); |
| 211 | + assert_eq!(got_sk, want_sk) |
| 212 | + } |
| 213 | + |
| 214 | + #[test] |
| 215 | + fn get_key_xpriv_with_path() { |
| 216 | + let secp = Secp256k1::new(); |
| 217 | + |
| 218 | + let s = "xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi"; |
| 219 | + let master = s.parse::<Xpriv>().unwrap(); |
| 220 | + let master_fingerprint = master.fingerprint(&secp); |
| 221 | + |
| 222 | + let first_external_child = "44'/0'/0'/0/0"; |
| 223 | + let derivation_path = first_external_child.into_derivation_path().unwrap(); |
| 224 | + |
| 225 | + let child = master.derive_priv(&secp, &derivation_path).unwrap(); |
| 226 | + |
| 227 | + // Sanity check. |
| 228 | + { |
| 229 | + let descriptor_sk_s = |
| 230 | + format!("[{}/{}]{}", master_fingerprint, first_external_child, child); |
| 231 | + let descriptor_sk = descriptor_sk_s.parse::<DescriptorSecretKey>().unwrap(); |
| 232 | + let got = match descriptor_sk { |
| 233 | + DescriptorSecretKey::XPrv(ref x) => x.xkey, |
| 234 | + _ => panic!("unexpected DescriptorSecretKey variant"), |
| 235 | + }; |
| 236 | + assert_eq!(got, child); |
| 237 | + } |
| 238 | + |
| 239 | + let want_sk = child.to_priv(); |
| 240 | + let descriptor_s = format!("wpkh({}/44'/0'/0'/0/*)", s); |
| 241 | + let (_, keymap) = Descriptor::parse_descriptor(&secp, &descriptor_s).unwrap(); |
| 242 | + let keymap_wrapper = KeyMapWrapper::from(keymap); |
| 243 | + |
| 244 | + let key_source = (master_fingerprint, derivation_path); |
| 245 | + let request = KeyRequest::Bip32(key_source); |
| 246 | + let got_sk = keymap_wrapper |
| 247 | + .get_key(request, &secp) |
| 248 | + .expect("get_key call errored") |
| 249 | + .expect("failed to find the key"); |
| 250 | + |
| 251 | + assert_eq!(got_sk, want_sk) |
| 252 | + } |
| 253 | + |
| 254 | + #[test] |
| 255 | + fn get_key_xpriv_with_key_origin() { |
| 256 | + let secp = Secp256k1::new(); |
| 257 | + |
| 258 | + let descriptor_str = "wpkh([d34db33f/84h/1h/0h]tprv8ZgxMBicQKsPd3EupYiPRhaMooHKUHJxNsTfYuScep13go8QFfHdtkG9nRkFGb7busX4isf6X9dURGCoKgitaApQ6MupRhZMcELAxTBRJgS/*)"; |
| 259 | + let (_descriptor_pk, keymap) = Descriptor::parse_descriptor(&secp, descriptor_str).unwrap(); |
| 260 | + let keymap_wrapper = KeyMapWrapper::from(keymap); |
| 261 | + |
| 262 | + let descriptor_sk = DescriptorSecretKey::from_str("[d34db33f/84h/1h/0h]tprv8ZgxMBicQKsPd3EupYiPRhaMooHKUHJxNsTfYuScep13go8QFfHdtkG9nRkFGb7busX4isf6X9dURGCoKgitaApQ6MupRhZMcELAxTBRJgS/*").unwrap(); |
| 263 | + let xpriv = match descriptor_sk { |
| 264 | + DescriptorSecretKey::XPrv(descriptor_xkey) => descriptor_xkey, |
| 265 | + _ => unreachable!(), |
| 266 | + }; |
| 267 | + |
| 268 | + let path = DerivationPath::from_str("84'/1'/0'/0").unwrap(); |
| 269 | + let expected_pk = xpriv.xkey.derive_priv(&secp, &path).unwrap().to_priv(); |
| 270 | + |
| 271 | + let (fp, _) = xpriv.origin.unwrap(); |
| 272 | + let key_request = KeyRequest::Bip32((fp, path)); |
| 273 | + |
| 274 | + let pk = keymap_wrapper |
| 275 | + .get_key(key_request, &secp) |
| 276 | + .expect("get_key should not fail") |
| 277 | + .expect("get_key should return a `PrivateKey`"); |
| 278 | + |
| 279 | + assert_eq!(pk, expected_pk); |
| 280 | + } |
| 281 | + |
| 282 | + #[test] |
| 283 | + fn get_key_keymap_no_match() { |
| 284 | + let secp = Secp256k1::new(); |
| 285 | + |
| 286 | + // Create a keymap with one key |
| 287 | + let descriptor_s = "wpkh(cMk8gWmj1KpjdYnAWwsEDekodMYhbyYBhG8gMtCCxucJ98JzcNij)"; |
| 288 | + let (_, keymap) = Descriptor::parse_descriptor(&secp, descriptor_s).unwrap(); |
| 289 | + let keymap_wrapper = KeyMapWrapper::from(keymap); |
| 290 | + |
| 291 | + // Request a different public key that doesn't exist in the keymap |
| 292 | + let different_sk = |
| 293 | + PrivateKey::from_str("cNJFgo1driFnPcBdBX8BrJrpxchBWXwXCvNH5SoSkdcF6JXXwHMm").unwrap(); |
| 294 | + let different_pk = different_sk.public_key(&secp); |
| 295 | + let request = KeyRequest::Pubkey(different_pk); |
| 296 | + |
| 297 | + let result = keymap_wrapper.get_key(request, &secp).unwrap(); |
| 298 | + assert!(result.is_none(), "Should return None when no matching key is found"); |
| 299 | + } |
| 300 | + |
| 301 | + #[test] |
| 302 | + fn get_key_descriptor_secret_key_xonly_not_supported() { |
| 303 | + let secp = Secp256k1::new(); |
| 304 | + |
| 305 | + let descriptor_sk = DescriptorSecretKey::from_str("xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi").unwrap(); |
| 306 | + |
| 307 | + // Create an x-only public key request |
| 308 | + let sk = |
| 309 | + PrivateKey::from_str("cMk8gWmj1KpjdYnAWwsEDekodMYhbyYBhG8gMtCCxucJ98JzcNij").unwrap(); |
| 310 | + let xonly_pk = sk.public_key(&secp).inner.x_only_public_key().0; |
| 311 | + let request = KeyRequest::XOnlyPubkey(xonly_pk); |
| 312 | + |
| 313 | + let result = descriptor_sk.get_key(request.clone(), &secp); |
| 314 | + assert!(matches!(result, Err(GetKeyError::NotSupported))); |
| 315 | + |
| 316 | + // Also test with KeyMap |
| 317 | + let descriptor_s = "wpkh(xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi)"; |
| 318 | + let (_, keymap) = Descriptor::parse_descriptor(&secp, descriptor_s).unwrap(); |
| 319 | + let keymap_wrapper = KeyMapWrapper::from(keymap); |
| 320 | + |
| 321 | + // While requesting an x-only key from an individual xpriv, that's an error. |
| 322 | + // But from a keymap, which might have both x-only keys and regular xprivs, |
| 323 | + // we treat errors as "key not found". |
| 324 | + let result = keymap_wrapper.get_key(request, &secp); |
| 325 | + assert!(matches!(result, Ok(None))); |
| 326 | + } |
| 327 | + |
| 328 | + #[test] |
| 329 | + fn get_key_descriptor_secret_key_xonly_multipath() { |
| 330 | + let secp = Secp256k1::new(); |
| 331 | + |
| 332 | + let descriptor_sk = DescriptorSecretKey::from_str("[d34db33f/84h/0h/0h]tprv8ZgxMBicQKsPd3EupYiPRhaMooHKUHJxNsTfYuScep13go8QFfHdtkG9nRkFGb7busX4isf6X9dURGCoKgitaApQ6MupRhZMcELAxTBRJgS/<0;1>").unwrap(); |
| 333 | + |
| 334 | + // Request with a different fingerprint |
| 335 | + let different_fingerprint = bitcoin::bip32::Fingerprint::from([0x12, 0x34, 0x56, 0x78]); |
| 336 | + let path = DerivationPath::from_str("84'/1'/0'/0").unwrap(); |
| 337 | + let request = KeyRequest::Bip32((different_fingerprint, path)); |
| 338 | + |
| 339 | + let result = descriptor_sk.get_key(request.clone(), &secp).unwrap(); |
| 340 | + assert!(result.is_none(), "Should return None when fingerprint doesn't match"); |
| 341 | + |
| 342 | + // Create an x-only public key request -- now we get "not supported". |
| 343 | + let sk = |
| 344 | + PrivateKey::from_str("cMk8gWmj1KpjdYnAWwsEDekodMYhbyYBhG8gMtCCxucJ98JzcNij").unwrap(); |
| 345 | + let xonly_pk = sk.public_key(&secp).inner.x_only_public_key().0; |
| 346 | + let request_x = KeyRequest::XOnlyPubkey(xonly_pk); |
| 347 | + |
| 348 | + let result = descriptor_sk.get_key(request_x.clone(), &secp); |
| 349 | + assert!(matches!(result, Err(GetKeyError::NotSupported))); |
| 350 | + |
| 351 | + // Also test with KeyMap; as in the previous test, the error turns to None. |
| 352 | + let descriptor_s = "wpkh([d34db33f/84h/1h/0h]tprv8ZgxMBicQKsPd3EupYiPRhaMooHKUHJxNsTfYuScep13go8QFfHdtkG9nRkFGb7busX4isf6X9dURGCoKgitaApQ6MupRhZMcELAxTBRJgS/*)"; |
| 353 | + let (_, keymap) = Descriptor::parse_descriptor(&secp, descriptor_s).unwrap(); |
| 354 | + let keymap_wrapper = KeyMapWrapper::from(keymap); |
| 355 | + |
| 356 | + let result = keymap_wrapper.get_key(request, &secp).unwrap(); |
| 357 | + assert!(result.is_none(), "Should return None when fingerprint doesn't match"); |
| 358 | + let result = keymap_wrapper.get_key(request_x, &secp).unwrap(); |
| 359 | + assert!(result.is_none(), "Should return None even on error"); |
| 360 | + } |
| 361 | +} |
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