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| 1 | +//! This module allows DIDs to publically attests to arbirary (and arbitrarily large) RDF |
| 2 | +//! claimgraphs. These attestations are not stored on-chain; rather, the attester chooses a storage |
| 3 | +//! method by specifying an Iri. |
| 4 | +
|
| 5 | +use crate::did::{self, Did, DidSignature}; |
| 6 | +use crate::StateChange; |
| 7 | +use alloc::vec::Vec; |
| 8 | +use codec::{Decode, Encode}; |
| 9 | +use frame_support::{ |
| 10 | + decl_error, decl_module, decl_storage, dispatch::DispatchResult, ensure, traits::Get, |
| 11 | + weights::Weight, |
| 12 | +}; |
| 13 | +use frame_system::{self as system, ensure_signed}; |
| 14 | + |
| 15 | +pub type Iri = Vec<u8>; |
| 16 | + |
| 17 | +pub trait Trait: system::Trait + did::Trait { |
| 18 | + /// The cost charged by the network to store a single byte in chain-state for the life of the |
| 19 | + /// chain. |
| 20 | + type StorageWeight: Get<Weight>; |
| 21 | +} |
| 22 | + |
| 23 | +#[derive(Encode, Decode, Clone, PartialEq, Debug, Default)] |
| 24 | +#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))] |
| 25 | +pub struct Attestation { |
| 26 | + #[codec(compact)] |
| 27 | + priority: u64, |
| 28 | + iri: Option<Iri>, |
| 29 | +} |
| 30 | + |
| 31 | +decl_error! { |
| 32 | + /// Error for the attest module. |
| 33 | + pub enum Error for Module<T: Trait> { |
| 34 | + /// The Attestation was not posted because its priority was less than or equal to that of |
| 35 | + /// an attestation previously posted by the same entity. |
| 36 | + /// |
| 37 | + /// Note, the default value for an attestation is the null claim (claiming nothing), with |
| 38 | + /// a priority of 0. To override this initial value, a priority of 1 or greater is required. |
| 39 | + /// Check to see that the provided priority is not zero as that could be the cause of this |
| 40 | + /// error. |
| 41 | + PriorityTooLow, |
| 42 | + /// Signature verification failed while adding blob |
| 43 | + InvalidSig |
| 44 | + } |
| 45 | +} |
| 46 | + |
| 47 | +decl_storage! { |
| 48 | + trait Store for Module<T: Trait> as Blob { |
| 49 | + // The priority value provides replay protection and also gives attestations a paritial |
| 50 | + // ordering. Signatures with lesser or equal priority to those previously posted by the same |
| 51 | + // entity are not accepted by the chain. |
| 52 | + // |
| 53 | + // Notice that priority is not a block-number. This is intentional as it yields some desired |
| 54 | + // properties and allows some potential use-cases: |
| 55 | + // - When publishing consecutive attestations, the attester need not care at which block a |
| 56 | + // a previous attestation was included. This means attestations can be made over a |
| 57 | + // mono-directional channel. |
| 58 | + // - Timestamps may be used as priority when available. |
| 59 | + // - A timeline of future attestations may be constructed by encrypting multiple |
| 60 | + // signatures, each with the output of a verifiable delay function. A "final" |
| 61 | + // attestation may be selected by assigning it the higest prority in the batch. |
| 62 | + // The "final" attestation will be acceptable by the runtime regardless of whether its |
| 63 | + // predecessors were submitted. |
| 64 | + // |
| 65 | + // An attestation on chain with iri set to None is sematically meaningless. Setting the |
| 66 | + // iri to None is equivalent to attesting to the empty claimgraph. |
| 67 | + // |
| 68 | + // When Attestations::get(did).iri == Some(dat) and dat is a valid utf-8 Iri: |
| 69 | + // `[did dock:attestsDocumentContents dat]`. |
| 70 | + Attestations: map hasher(blake2_128_concat) Did => Attestation; |
| 71 | + } |
| 72 | +} |
| 73 | + |
| 74 | +decl_module! { |
| 75 | + pub struct Module<T: Trait> for enum Call where origin: T::Origin { |
| 76 | + #[weight = { |
| 77 | + T::DbWeight::get().reads_writes(2, 1) |
| 78 | + + signature.weight() |
| 79 | + + attests |
| 80 | + .iri |
| 81 | + .as_ref() |
| 82 | + .map(|iri| iri.len()) |
| 83 | + .unwrap_or_default() as Weight |
| 84 | + * T::StorageWeight::get() |
| 85 | + }] |
| 86 | + fn set_claim( |
| 87 | + origin, |
| 88 | + attester: Did, |
| 89 | + attests: Attestation, |
| 90 | + signature: DidSignature, |
| 91 | + ) -> DispatchResult { |
| 92 | + Module::<T>::set_claim_(origin, attester, attests, signature) |
| 93 | + } |
| 94 | + } |
| 95 | +} |
| 96 | + |
| 97 | +impl<T: Trait> Module<T> { |
| 98 | + fn set_claim_( |
| 99 | + origin: <T as system::Trait>::Origin, |
| 100 | + attester: Did, |
| 101 | + attests: Attestation, |
| 102 | + signature: DidSignature, |
| 103 | + ) -> DispatchResult { |
| 104 | + ensure_signed(origin)?; |
| 105 | + |
| 106 | + // check |
| 107 | + let payload = StateChange::Attestation((attester, attests.clone())).encode(); |
| 108 | + let valid = did::Module::<T>::verify_sig_from_did(&signature, &payload, &attester)?; |
| 109 | + ensure!(valid, Error::<T>::InvalidSig); |
| 110 | + let prev = Attestations::get(&attester); |
| 111 | + ensure!(prev.priority < attests.priority, Error::<T>::PriorityTooLow); |
| 112 | + |
| 113 | + // execute |
| 114 | + Attestations::insert(&attester, &attests); |
| 115 | + |
| 116 | + Ok(()) |
| 117 | + } |
| 118 | +} |
| 119 | + |
| 120 | +#[cfg(test)] |
| 121 | +mod test { |
| 122 | + use super::*; |
| 123 | + use crate::test_common::*; |
| 124 | + use sp_core::sr25519; |
| 125 | + |
| 126 | + type Mod = crate::attest::Module<Test>; |
| 127 | + type Er = crate::attest::Error<Test>; |
| 128 | + |
| 129 | + /// Trigger the PriorityTooLow error by submitting a priority 0 attestation. |
| 130 | + #[test] |
| 131 | + fn priority_too_low() { |
| 132 | + ext().execute_with(|| { |
| 133 | + let (did, kp) = newdid(); |
| 134 | + let att = Attestation { |
| 135 | + priority: 0, |
| 136 | + iri: None, |
| 137 | + }; |
| 138 | + let err = Mod::set_claim( |
| 139 | + Origin::signed(0), |
| 140 | + did, |
| 141 | + att.clone(), |
| 142 | + sign(&StateChange::Attestation((did, att)), &kp), |
| 143 | + ) |
| 144 | + .unwrap_err(); |
| 145 | + assert_eq!(err, Er::PriorityTooLow.into()); |
| 146 | + }); |
| 147 | + } |
| 148 | + |
| 149 | + /// assert sizes of encoded Attestation |
| 150 | + #[test] |
| 151 | + fn encoded_attestation_size() { |
| 152 | + ext().execute_with(|| { |
| 153 | + for (priority, iri, expected_size) in [ |
| 154 | + (0, None, 1 + 1), |
| 155 | + (63, None, 1 + 1), |
| 156 | + (64, None, 2 + 1), |
| 157 | + (256, None, 2 + 1), |
| 158 | + (0, Some(vec![]), 1 + 2), |
| 159 | + (0, Some(vec![0]), 1 + 3), |
| 160 | + (0, Some(vec![0; 63]), 1 + 63 + 2), |
| 161 | + (0, Some(vec![0; 64]), 1 + 64 + 3), |
| 162 | + (0, Some(vec![0; 256]), 1 + 256 + 3), |
| 163 | + (63, Some(vec![0; 256]), 1 + 256 + 3), |
| 164 | + (64, Some(vec![0; 256]), 2 + 256 + 3), |
| 165 | + ] |
| 166 | + .iter() |
| 167 | + .cloned() |
| 168 | + { |
| 169 | + assert_eq!(Attestation { priority, iri }.encode().len(), expected_size); |
| 170 | + } |
| 171 | + }); |
| 172 | + } |
| 173 | + |
| 174 | + /// Trigger the InvalidSig error by tweaking a value in the plaintext after signing |
| 175 | + #[test] |
| 176 | + fn invalid_sig_a() { |
| 177 | + ext().execute_with(|| { |
| 178 | + let (dida, kpa) = newdid(); |
| 179 | + let mut att = Attestation { |
| 180 | + priority: 1, |
| 181 | + iri: None, |
| 182 | + }; |
| 183 | + let sig = sign(&StateChange::Attestation((dida, att.clone())), &kpa); |
| 184 | + att.priority += 1; |
| 185 | + let err = Mod::set_claim(Origin::signed(0), dida, att, sig).unwrap_err(); |
| 186 | + assert_eq!(err, Er::InvalidSig.into()); |
| 187 | + }); |
| 188 | + } |
| 189 | + |
| 190 | + /// Trigger the InvalidSig error using a different did for signing |
| 191 | + #[test] |
| 192 | + fn invalid_sig_b() { |
| 193 | + ext().execute_with(|| { |
| 194 | + let (dida, _kpa) = newdid(); |
| 195 | + let (_didb, kpb) = newdid(); |
| 196 | + let att = Attestation { |
| 197 | + priority: 1, |
| 198 | + iri: None, |
| 199 | + }; |
| 200 | + let err = Mod::set_claim( |
| 201 | + Origin::signed(0), |
| 202 | + dida, |
| 203 | + att.clone(), |
| 204 | + sign(&StateChange::Attestation((dida, att)), &kpb), |
| 205 | + ) |
| 206 | + .unwrap_err(); |
| 207 | + assert_eq!(err, Er::InvalidSig.into()); |
| 208 | + }); |
| 209 | + } |
| 210 | + |
| 211 | + /// Attestations with equal priority are mutually exlusive |
| 212 | + #[test] |
| 213 | + fn priority_face_off() { |
| 214 | + ext().execute_with(|| { |
| 215 | + let (did, kp) = newdid(); |
| 216 | + |
| 217 | + // same iri |
| 218 | + set_claim( |
| 219 | + &did, |
| 220 | + &Attestation { |
| 221 | + priority: 1, |
| 222 | + iri: None, |
| 223 | + }, |
| 224 | + &kp, |
| 225 | + ) |
| 226 | + .unwrap(); |
| 227 | + assert_eq!( |
| 228 | + set_claim( |
| 229 | + &did, |
| 230 | + &Attestation { |
| 231 | + priority: 1, |
| 232 | + iri: None, |
| 233 | + }, |
| 234 | + &kp, |
| 235 | + ) |
| 236 | + .unwrap_err(), |
| 237 | + Er::PriorityTooLow.into() |
| 238 | + ); |
| 239 | + |
| 240 | + // different iris |
| 241 | + set_claim( |
| 242 | + &did, |
| 243 | + &Attestation { |
| 244 | + priority: 2, |
| 245 | + iri: Some(vec![0]), |
| 246 | + }, |
| 247 | + &kp, |
| 248 | + ) |
| 249 | + .unwrap(); |
| 250 | + assert_eq!( |
| 251 | + set_claim( |
| 252 | + &did, |
| 253 | + &Attestation { |
| 254 | + priority: 2, |
| 255 | + iri: Some(vec![0, 2, 3]), |
| 256 | + }, |
| 257 | + &kp, |
| 258 | + ) |
| 259 | + .unwrap_err(), |
| 260 | + Er::PriorityTooLow.into() |
| 261 | + ); |
| 262 | + }); |
| 263 | + } |
| 264 | + |
| 265 | + /// After attempting a set of attestations the one with highest priority is the one that ends up |
| 266 | + /// in chain state. |
| 267 | + #[test] |
| 268 | + fn priority_battle_royale() { |
| 269 | + ext().execute_with(|| { |
| 270 | + let (did, kp) = newdid(); |
| 271 | + let prios: Vec<u64> = (0..200).map(|_| rand::random::<u64>()).collect(); |
| 272 | + for priority in &prios { |
| 273 | + let _ = set_claim( |
| 274 | + &did, |
| 275 | + &Attestation { |
| 276 | + priority: *priority, |
| 277 | + iri: None, |
| 278 | + }, |
| 279 | + &kp, |
| 280 | + ); |
| 281 | + } |
| 282 | + assert_eq!( |
| 283 | + Attestations::get(did).priority, |
| 284 | + prios.iter().max().unwrap().clone() |
| 285 | + ); |
| 286 | + }); |
| 287 | + } |
| 288 | + |
| 289 | + /// An attestation with priority set to the highest value is final. |
| 290 | + /// It does not trigger a panic by integer overflow. |
| 291 | + #[test] |
| 292 | + fn max_priority_is_final() { |
| 293 | + ext().execute_with(|| { |
| 294 | + let (did, kp) = newdid(); |
| 295 | + set_claim( |
| 296 | + &did, |
| 297 | + &Attestation { |
| 298 | + priority: u64::max_value(), |
| 299 | + iri: None, |
| 300 | + }, |
| 301 | + &kp, |
| 302 | + ) |
| 303 | + .unwrap(); |
| 304 | + let err = set_claim( |
| 305 | + &did, |
| 306 | + &Attestation { |
| 307 | + priority: u64::max_value(), |
| 308 | + iri: None, |
| 309 | + }, |
| 310 | + &kp, |
| 311 | + ) |
| 312 | + .unwrap_err(); |
| 313 | + assert_eq!(err, Er::PriorityTooLow.into()); |
| 314 | + }); |
| 315 | + } |
| 316 | + |
| 317 | + /// Set an attestation that is not None |
| 318 | + #[test] |
| 319 | + fn set_some_attestation() { |
| 320 | + ext().execute_with(|| { |
| 321 | + let (did, kp) = newdid(); |
| 322 | + assert_eq!( |
| 323 | + Attestations::get(did), |
| 324 | + Attestation { |
| 325 | + priority: 0, |
| 326 | + iri: None, |
| 327 | + } |
| 328 | + ); |
| 329 | + set_claim( |
| 330 | + &did, |
| 331 | + &Attestation { |
| 332 | + priority: 1, |
| 333 | + iri: Some(vec![0, 1, 2]), |
| 334 | + }, |
| 335 | + &kp, |
| 336 | + ) |
| 337 | + .unwrap(); |
| 338 | + assert_eq!( |
| 339 | + Attestations::get(did), |
| 340 | + Attestation { |
| 341 | + priority: 1, |
| 342 | + iri: Some(vec![0, 1, 2]), |
| 343 | + } |
| 344 | + ); |
| 345 | + }); |
| 346 | + } |
| 347 | + |
| 348 | + /// Skip a priority value. |
| 349 | + #[test] |
| 350 | + fn skip_prio() { |
| 351 | + ext().execute_with(|| { |
| 352 | + let (did, kp) = newdid(); |
| 353 | + for priority in &[1, 2, 4] { |
| 354 | + set_claim( |
| 355 | + &did, |
| 356 | + &Attestation { |
| 357 | + priority: *priority, |
| 358 | + iri: None, |
| 359 | + }, |
| 360 | + &kp, |
| 361 | + ) |
| 362 | + .unwrap(); |
| 363 | + } |
| 364 | + }); |
| 365 | + } |
| 366 | + |
| 367 | + /// helper |
| 368 | + fn set_claim(claimer: &did::Did, att: &Attestation, kp: &sr25519::Pair) -> DispatchResult { |
| 369 | + Mod::set_claim( |
| 370 | + Origin::signed(0), |
| 371 | + claimer.clone(), |
| 372 | + att.clone(), |
| 373 | + sign( |
| 374 | + &StateChange::Attestation((claimer.clone(), att.clone())), |
| 375 | + kp, |
| 376 | + ), |
| 377 | + ) |
| 378 | + } |
| 379 | +} |
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