Add Sapling output decrypting with spending key

Reviewed-on: #54

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [0.5.3.0]
 
+### Added
+
+- Function to decode Sapling outputs with a spending key
+
 ### Fixed
 
 - Parsing of `TxIn` for FFI

librustzcash-wrapper/Cargo.lock

@@ -1284,6 +1284,7 @@ dependencies = [
  "borsh 0.10.3",
  "f4jumble",
  "haskell-ffi",
+ "incrementalmerkletree",
  "nonempty",
  "orchard",
  "proc-macro2",

librustzcash-wrapper/Cargo.toml

@@ -18,6 +18,7 @@ zcash_client_backend = "0.10.0"
 zip32 = "0.1.0"
 proc-macro2 = "1.0.66"
 nonempty = "0.7.0"
+incrementalmerkletree = "0.5.0"
 
 
 [features]

librustzcash-wrapper/src/lib.rs

@@ -23,6 +23,8 @@ use haskell_ffi::{
     FromHaskell, HaskellSize, ToHaskell
 };
 
+use incrementalmerkletree::frontier::CommitmentTree;
+
 use zip32;
 
 use zcash_primitives::{
@@ -51,6 +53,9 @@ use zcash_primitives::{
         }
     },
     sapling::{
+        Node,
+        MerklePath,
+        NOTE_COMMITMENT_TREE_DEPTH as SAPLING_DEPTH,
         PaymentAddress,
         keys::{
             PreparedIncomingViewingKey as SaplingPreparedIncomingViewingKey,
@@ -63,6 +68,7 @@ use zcash_primitives::{
     consensus::{
         BranchId::Nu5,
         MainNetwork,
+        TestNetwork,
         BlockHeight
     }
 };
@@ -602,7 +608,7 @@ pub extern "C" fn rust_wrapper_svk_decode(
     let input: Vec<u8> = marshall_from_haskell_var(input, input_len, RW);
     let svk = ExtendedFullViewingKey::read(&*input);
     match svk {
-        Ok(k) => {
+        Ok(_k) => {
             true
         }
         Err(e) => {
@@ -698,6 +704,64 @@ pub extern "C" fn rust_wrapper_ufvk_decode(
     }
 }
 
+#[no_mangle]
+pub extern "C" fn rust_wrapper_sapling_esk_decrypt(
+    key: *const u8,
+    key_len: usize,
+    note: *const u8,
+    note_len: usize,
+    external: bool,
+    net: bool,
+    out: *mut u8,
+    out_len: &mut usize
+ ){
+    let sk: Vec<u8> = marshall_from_haskell_var(key, key_len, RW);
+    let note_input: Vec<u8> = marshall_from_haskell_var(note,note_len,RW);
+    let mut note_reader = Cursor::new(note_input);
+    let esk = ExtendedSpendingKey::from_bytes(&sk);
+    let main_domain = SaplingDomain::for_height(MainNetwork, BlockHeight::from_u32(419200));
+    let test_domain = SaplingDomain::for_height(TestNetwork, BlockHeight::from_u32(419200));
+    let scope = if external {
+        SaplingScope::External
+    } else {
+        SaplingScope::Internal
+    };
+    match esk {
+        Ok(k) => {
+            let action = OutputDescription::read(&mut note_reader);
+            match action {
+                Ok(action2) => {
+                    let dfvk = k.to_diversifiable_full_viewing_key();
+                    let ivk = dfvk.to_ivk(scope);
+                    let nk = dfvk.to_nk(scope);
+                    let pivk = SaplingPreparedIncomingViewingKey::new(&ivk);
+                    let result = if net { zcash_note_encryption::try_note_decryption(&main_domain, &pivk, &action2)}
+                    else {zcash_note_encryption::try_note_decryption(&test_domain, &pivk, &action2)};
+                    match result {
+                        Some((n, r, m)) => {
+                            //let nullifier = n.nf(&nk, MerklePath<Node::from_cmu(&n.cmu()), SAPLING_DEPTH>.position());
+                            let hn = Hnote {note: n.value().inner(), recipient: r.to_bytes().to_vec(), memo: m.as_slice().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);
+                        }
+                    }
+                },
+                Err(_e1) => {
+                    let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0] };
+                    marshall_to_haskell_var(&hn0, out, out_len, RW);
+                }
+            }
+        },
+        Err(_e) => {
+            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_sapling_note_decrypt_v2(
     key: *const u8,
@@ -722,11 +786,11 @@ pub extern "C" fn rust_wrapper_sapling_note_decrypt_v2(
                     let result = zcash_note_encryption::try_note_decryption(&domain, &pivk, &action3);
                     match result {
                         Some((n, r, m)) => {
-                            let hn = Hnote {note: n.value().inner(), recipient: r.to_bytes().to_vec(), memo: m.as_slice().to_vec() };
+                            let hn = Hnote {note: n.value().inner(), recipient: r.to_bytes().to_vec(), memo: m.as_slice().to_vec()};
                             marshall_to_haskell_var(&hn, out, out_len, RW);
                         }
                         None => {
-                            let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0] };
+                            let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0]};
                             marshall_to_haskell_var(&hn0, out, out_len, RW);
                         }
                     }
@@ -738,7 +802,7 @@ pub extern "C" fn rust_wrapper_sapling_note_decrypt_v2(
             }
         }
         Err(_e) => {
-            let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0] };
+            let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0]};
             marshall_to_haskell_var(&hn0, out, out_len, RW);
         }
     }
@@ -772,17 +836,17 @@ pub extern "C" fn rust_wrapper_orchard_note_decrypt(
             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() };
+                    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] };
+                    let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0]};
                     marshall_to_haskell_var(&hn0, out, out_len, RW);
                 }
             }
         },
         None => {
-            let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0] };
+            let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0]};
             marshall_to_haskell_var(&hn0, out, out_len, RW);
         }
     }

src/C/Zcash.chs

@@ -101,6 +101,16 @@ import ZcashHaskell.Types
   -> `()'
 #}
 
+{# fun unsafe rust_wrapper_sapling_esk_decrypt as rustWrapperSaplingDecodeEsk
+    { toBorshVar* `BS.ByteString'&
+    , toBorshVar* `BS.ByteString'&
+    , `Bool'
+    , `Bool'
+    , getVarBuffer `Buffer DecodedNote'&
+    }
+ -> `()'
+#}
+
 {# fun unsafe rust_wrapper_ufvk_decode as rustWrapperUfvkDecode
      { toBorshVar* `BS.ByteString'&
      , getVarBuffer `Buffer UnifiedFullViewingKey'&

src/ZcashHaskell/Sapling.hs

@@ -21,6 +21,7 @@ import C.Zcash
   ( rustWrapperIsShielded
   , rustWrapperSaplingCheck
   , rustWrapperSaplingChgPaymentAddress
+  , rustWrapperSaplingDecodeEsk
   , rustWrapperSaplingNoteDecode
   , rustWrapperSaplingPaymentAddress
   , rustWrapperSaplingSpendingkey
@@ -29,7 +30,7 @@ import C.Zcash
   )
 import Data.Aeson
 import qualified Data.ByteString as BS
-import Data.HexString (HexString(..), toBytes)
+import Data.HexString (HexString(..), fromText, toBytes, toText)
 import Data.Word
 import Foreign.Rust.Marshall.Variable
   ( withPureBorshVarBuffer
@@ -43,9 +44,11 @@ import ZcashHaskell.Types
   , RawTxResponse(..)
   , SaplingReceiver(..)
   , SaplingSpendingKey(..)
+  , Scope(..)
   , Seed(..)
   , ShieldedOutput(..)
   , ToBytes(..)
+  , ZcashNet(..)
   , decodeHexText
   , getValue
   )
@@ -58,6 +61,15 @@ isValidShieldedAddress = rustWrapperIsShielded
 getShieldedOutputs :: HexString -> [BS.ByteString]
 getShieldedOutputs t = withPureBorshVarBuffer $ rustWrapperTxParse $ toBytes t
 
+serializeShieldedOutput :: ShieldedOutput -> BS.ByteString
+serializeShieldedOutput so =
+  hexBytes . fromText $
+  toText (s_cv so) <>
+  toText (s_cmu so) <>
+  toText (s_ephKey so) <>
+  toText (s_encCipherText so) <>
+  toText (s_outCipherText so) <> toText (s_proof so)
+
 -- | Check if given bytestring is a valid Sapling viewing key
 isValidSaplingViewingKey :: BS.ByteString -> Bool
 isValidSaplingViewingKey k =
@@ -98,6 +110,26 @@ instance FromJSON RawTxResponse where
           a <- o' .: "actions"
           pure $ RawTxResponse i h sSpend (getShieldedOutputs h) a ht c b
 
+-- | Attempt to decode the given raw tx with the given Sapling spending key
+decodeSaplingOutputEsk ::
+     SaplingSpendingKey
+  -> ShieldedOutput
+  -> ZcashNet
+  -> Scope
+  -> Maybe DecodedNote
+decodeSaplingOutputEsk key out znet scope =
+  case a_value decodedAction of
+    0 -> Nothing
+    _ -> Just decodedAction
+  where
+    decodedAction =
+      withPureBorshVarBuffer $
+      rustWrapperSaplingDecodeEsk
+        (getBytes key)
+        (serializeShieldedOutput out)
+        (znet == MainNet)
+        (scope == External)
+
 -- | Attempts to obtain a sapling SpendingKey using a HDSeed
 genSaplingSpendingKey :: Seed -> CoinType -> Int -> Maybe SaplingSpendingKey
 genSaplingSpendingKey seed c i = do