fix(dbc_owner): verify input owner proofs

src/error.rs

@@ -28,6 +28,8 @@ pub enum Error {
     UnrecognisedAuthority,
     #[error("At least one transaction input is missing a signature.")]
     MissingSignatureForInput,
+    #[error("At least one input is missing an ownership proof")]
+    MissingInputOwnerProof,
     #[error("Mint request doesn't balance out sum(input) == sum(output)")]
     DbcMintRequestDoesNotBalance { input: u64, output: u64 },
     #[error("Outputs must be numbered 0..N where N = # of outputs")]

src/mint.rs

@@ -164,8 +164,16 @@ impl Mint {
         mint_request: MintRequest,
     ) -> Result<(DbcTransaction, InputSignatures)> {
         mint_request.transaction.validate(self.key_cache())?;
-
         let transaction = mint_request.transaction.blinded();
+        let transaction_hash = transaction.hash();
+        for input_dbc in mint_request.transaction.inputs.iter() {
+            let owner_key = input_dbc.content.owner.public_key();
+            match mint_request.input_ownership_proofs.get(&input_dbc.name()) {
+                Some(sig) if owner_key.verify(&sig, &transaction_hash) => (),
+                Some(_) => return Err(Error::FailedSignature),
+                None => return Err(Error::MissingInputOwnerProof),
+            }
+        }
 
         // Validate that each input has not yet been spent.
         for input in transaction.inputs.iter() {