Instantiate ProofChain from a Cid (#35)

ucan-wg · Oct 24, 2022 · 11d10d6 · 11d10d6
1 parent 163b5dc
commit 11d10d6
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Showing 2 changed files with 58 additions and 2 deletions.
diff --git a/ucan/src/chain.rs b/ucan/src/chain.rs
@@ -46,6 +46,7 @@ pub struct ProofChain {
 }
 
 impl ProofChain {
+    /// Instantiate a [ProofChain] from a [Ucan], given a [UcanJwtStore] and [DidParser]
     #[cfg_attr(target_arch = "wasm32", async_recursion(?Send))]
     #[cfg_attr(not(target_arch = "wasm32"), async_recursion)]
     pub async fn from_ucan<S>(
@@ -102,10 +103,16 @@ impl ProofChain {
         })
     }
 
-    pub async fn from_cid<'a>(_cid: &str, _did_parser: &mut DidParser) -> Result<ProofChain> {
-        todo!("Resolving a proof from a CID not yet implemented")
+    /// Instantiate a [ProofChain] from a [Cid], given a [UcanJwtStore] and [DidParser]
+    /// The [Cid] must resolve to a JWT token string
+    pub async fn from_cid<S>(cid: &Cid, did_parser: &mut DidParser, store: &S) -> Result<ProofChain>
+    where
+        S: UcanJwtStore,
+    {
+        Self::try_from_token_string(&store.require_token(cid).await?, did_parser, store).await
     }
 
+    /// Instantiate a [ProofChain] from a JWT token string, given a [UcanJwtStore] and [DidParser]
     pub async fn try_from_token_string<'a, S>(
         ucan_token_string: &str,
         did_parser: &mut DidParser,

diff --git a/ucan/src/tests/chain.rs b/ucan/src/tests/chain.rs
@@ -100,6 +100,55 @@ pub async fn it_fails_with_incorrect_chaining() {
     assert!(parse_token_result.is_err());
 }
 
+#[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
+#[cfg_attr(not(target_arch = "wasm32"), tokio::test)]
+pub async fn it_can_be_instantiated_by_cid() {
+    let identities = Identities::new().await;
+    let mut did_parser = DidParser::new(SUPPORTED_KEYS);
+
+    let leaf_ucan = UcanBuilder::default()
+        .issued_by(&identities.alice_key)
+        .for_audience(identities.bob_did.as_str())
+        .with_lifetime(60)
+        .build()
+        .unwrap()
+        .sign()
+        .await
+        .unwrap();
+
+    let delegated_token = UcanBuilder::default()
+        .issued_by(&identities.bob_key)
+        .for_audience(identities.mallory_did.as_str())
+        .with_lifetime(50)
+        .witnessed_by(&leaf_ucan)
+        .build()
+        .unwrap()
+        .sign()
+        .await
+        .unwrap()
+        .encode()
+        .unwrap();
+
+    let mut store = MemoryStore::default();
+
+    store
+        .write_token(&leaf_ucan.encode().unwrap())
+        .await
+        .unwrap();
+
+    let cid = store.write_token(&delegated_token).await.unwrap();
+
+    let chain = ProofChain::from_cid(&cid, &mut did_parser, &store)
+        .await
+        .unwrap();
+
+    assert_eq!(chain.ucan().audience(), &identities.mallory_did);
+    assert_eq!(
+        chain.proofs().get(0).unwrap().ucan().issuer(),
+        &identities.alice_did
+    );
+}
+
 #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
 #[cfg_attr(not(target_arch = "wasm32"), tokio::test)]
 pub async fn it_can_handle_multiple_leaves() {