Add function to decode Orchard action with spending key

librustzcash-wrapper/src/lib.rs

@@ -852,6 +852,47 @@ pub extern "C" fn rust_wrapper_orchard_note_decrypt(
     }
 }
 
+#[no_mangle]
+pub extern "C" fn rust_wrapper_orchard_note_decrypt_sk(
+    key: *const u8,
+    key_len: usize,
+    note: *const u8,
+    note_len: usize,
+    external: bool,
+    out: *mut u8,
+    out_len: &mut usize
+    ){
+    let sk_input: Vec<u8> = marshall_from_haskell_var(key, key_len, RW);
+    let note_input: Haction = marshall_from_haskell_var(note, note_len, RW);
+    let action: Action<Signature<SpendAuth>> = Action::from_parts(
+        Nullifier::from_bytes(&to_array(note_input.nf.bytes)).unwrap(), 
+        VerificationKey::try_from(to_array(note_input.rk.bytes)).unwrap(), 
+        ExtractedNoteCommitment::from_bytes(&to_array(note_input.cmx.bytes)).unwrap(), 
+        TransmittedNoteCiphertext {epk_bytes: to_array(note_input.eph_key.bytes), enc_ciphertext: to_array(note_input.enc_txt.bytes), out_ciphertext: to_array(note_input.out_txt.bytes)}, 
+        ValueCommitment::from_bytes(&to_array(note_input.cv.bytes)).unwrap(), 
+        Signature::from(to_array(note_input.auth.bytes)));
+    let sk_array = to_array(sk_input);
+    let domain = OrchardDomain::for_nullifier(*action.nullifier());
+    let dec_sk = SpendingKey::from_bytes(sk_array).unwrap();
+    let fvk = FullViewingKey::from(&dec_sk);
+    let ivk = if external {
+        fvk.to_ivk(Scope::External)
+    } else {
+        fvk.to_ivk(Scope::Internal)
+    };
+    let pivk = PreparedIncomingViewingKey::new(&ivk);
+    let result = zcash_note_encryption::try_note_decryption(&domain, &pivk, &action);
+    match result {
+        Some((n, r, m)) => {
+            let hn = Hnote {note: n.value().inner(), recipient: r.to_raw_address_bytes().to_vec(), memo: m.to_vec()};
+            marshall_to_haskell_var(&hn, out, out_len, RW);
+        }
+        None => {
+            let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0]};
+            marshall_to_haskell_var(&hn0, out, out_len, RW);
+        }
+    }
+}
 
 #[no_mangle]
 pub extern "C" fn rust_wrapper_tx_read(

src/C/Zcash.chs

@@ -126,6 +126,14 @@ import ZcashHaskell.Types
   -> `()'
 #}
 
+{# fun unsafe rust_wrapper_orchard_note_decrypt_sk as rustWrapperOrchardNoteDecodeSK
+     { toBorshVar* `BS.ByteString'&
+     , toBorshVar* `OrchardAction'&
+     , `Bool'
+     , getVarBuffer `Buffer DecodedNote'&
+     }
+  -> `()'
+#}
 {# fun unsafe rust_wrapper_tx_parse as rustWrapperTxParse
      { toBorshVar* `BS.ByteString'&
      , getVarBuffer `Buffer [BS.ByteString]'&

src/ZcashHaskell/Orchard.hs

@@ -22,6 +22,7 @@ import C.Zcash
   , rustWrapperGenOrchardSpendKey
   , rustWrapperOrchardCheck
   , rustWrapperOrchardNoteDecode
+  , rustWrapperOrchardNoteDecodeSK
   , rustWrapperUADecode
   , rustWrapperUfvkDecode
   )
@@ -153,3 +154,15 @@ decryptOrchardAction key encAction =
     decodedAction =
       withPureBorshVarBuffer $
       rustWrapperOrchardNoteDecode (o_key key) encAction
+
+-- | Attemtps to decode the given @OrchardAction@ using the given @OrchardSpendingKey@
+decryptOrchardActionSK ::
+     OrchardSpendingKey -> Scope -> OrchardAction -> Maybe DecodedNote
+decryptOrchardActionSK sk scope oa =
+  case a_value decodedAction of
+    0 -> Nothing
+    _ -> Just decodedAction
+  where
+    decodedAction =
+      withPureBorshVarBuffer $
+      rustWrapperOrchardNoteDecodeSK (getBytes sk) oa (scope == External)