Add function to append nodes to commitment tree

librustzcash-wrapper/src/lib.rs

@@ -6,7 +6,8 @@ use std::{
     marker::PhantomData,
     io::{
         Write,
-        Cursor
+        Cursor,
+        Error
     },
 };
 
@@ -28,6 +29,10 @@ use incrementalmerkletree::frontier::CommitmentTree;
 use zip32;
 
 use zcash_primitives::{
+    merkle_tree::{
+        read_commitment_tree,
+        write_commitment_tree
+    },
     zip32::{
         Scope as SaplingScope,
         ChildIndex,
@@ -57,6 +62,7 @@ use zcash_primitives::{
         MerklePath,
         NOTE_COMMITMENT_TREE_DEPTH as SAPLING_DEPTH,
         PaymentAddress,
+        note::ExtractedNoteCommitment as SaplingNoteCommitment,
         keys::{
             PreparedIncomingViewingKey as SaplingPreparedIncomingViewingKey,
             ExpandedSpendingKey,
@@ -187,6 +193,14 @@ pub struct Hhex {
     bytes: Vec<u8>
 }
 
+impl<RW> ToHaskell<RW> for Hhex {
+    fn to_haskell<W: Write>(&self, writer: &mut W, _tag: PhantomData<RW>) -> Result<()> {
+        self.serialize(writer)?;
+        Ok(())
+    }
+}
+
+
 #[derive(BorshSerialize, BorshDeserialize)]
 pub struct Haction {
     nf: Hhex,
@@ -1129,3 +1143,33 @@ pub extern "C" fn rust_wrapper_derive_orchard_receiver(
     marshall_to_haskell_var(&o_rec.to_raw_address_bytes().to_vec(), out, out_len, RW);
 
 }
+
+#[no_mangle]
+pub extern "C" fn rust_wrapper_read_commitment_tree(
+    tree: *const u8,
+    tree_len: usize,
+    node: *const u8,
+    node_len: usize,
+    out: *mut u8,
+    out_len: &mut usize
+    ){
+    let tree_in: Vec<u8> = marshall_from_haskell_var(tree, tree_len, RW);
+    let tree_reader = Cursor::new(tree_in);
+    let mut ct: CommitmentTree<Node, SAPLING_DEPTH> = read_commitment_tree(tree_reader).unwrap();
+
+    let node_in: Vec<u8> = marshall_from_haskell_var(node, node_len, RW);
+    let n = Node::from_cmu(&SaplingNoteCommitment::from_bytes(&to_array(node_in)).unwrap());
+    ct.append(n);
+    let mut out_bytes: Vec<u8> = Vec::new();
+    let result = write_commitment_tree(&ct, &mut out_bytes );
+    match result {
+        Ok(()) => {
+            let h = Hhex { bytes: out_bytes};
+            marshall_to_haskell_var(&h, out, out_len, RW);
+        },
+        Err(_e) => {
+            let h0 = Hhex { bytes: vec![0]};
+            marshall_to_haskell_var(&h0, out, out_len, RW);
+        }
+    }
+}

src/C/Zcash.chs

@@ -200,3 +200,11 @@ import ZcashHaskell.Types
      }
   -> `()'
 #}
+
+{# fun unsafe rust_wrapper_read_commitment_tree as rustWrapperReadSaplingCommitmentTree
+     { toBorshVar* `BS.ByteString'&
+     , toBorshVar* `BS.ByteString'&
+     , getVarBuffer `Buffer (BS.ByteString)'&
+     }
+  -> `()'
+#}

src/ZcashHaskell/Sapling.hs

@@ -19,6 +19,7 @@ module ZcashHaskell.Sapling where
 
 import C.Zcash
   ( rustWrapperIsShielded
+  , rustWrapperReadSaplingCommitmentTree
   , rustWrapperSaplingCheck
   , rustWrapperSaplingChgPaymentAddress
   , rustWrapperSaplingDecodeEsk
@@ -30,7 +31,7 @@ import C.Zcash
   )
 import Data.Aeson
 import qualified Data.ByteString as BS
-import Data.HexString (HexString(..), fromText, toBytes, toText)
+import Data.HexString (HexString(..), fromText, hexString, toBytes, toText)
 import Data.Word
 import Foreign.Rust.Marshall.Variable
   ( withPureBorshVarBuffer
@@ -166,3 +167,17 @@ genSaplingInternalAddress sk =
   where
     res =
       withPureBorshVarBuffer (rustWrapperSaplingChgPaymentAddress $ getBytes sk)
+
+-- | Update a Sapling commitment tree
+updateSaplingCommitmentTree ::
+     HexString -- ^ the base tree
+  -> HexString -- ^ the new note commitment
+  -> Maybe HexString
+updateSaplingCommitmentTree tree cmu =
+  if BS.length updatedTree > 1
+    then Just $ HexString updatedTree
+    else Nothing
+  where
+    updatedTree =
+      withPureBorshVarBuffer $
+      rustWrapperReadSaplingCommitmentTree (hexBytes tree) (hexBytes cmu)

test/Spec.hs

@@ -54,6 +54,7 @@ import ZcashHaskell.Sapling
   , isValidSaplingViewingKey
   , isValidShieldedAddress
   , matchSaplingAddress
+  , updateSaplingCommitmentTree
   )
 import ZcashHaskell.Transparent
 import ZcashHaskell.Types
@@ -844,6 +845,24 @@ main = do
               let tb = zt_tBundle t'
               print tb
               show tb `shouldNotBe` ""
+      describe "Sapling commitment trees" $ do
+        let tree =
+              hexString
+                "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"
+        let cmu1 =
+              hexString
+                "45e47c5df6f5c5e48aa3526e977b2d1b57eda57214e36f06128008cb17b0125f"
+        let cmu2 =
+              hexString
+                "426ef44b3b22e0eeda7e4d2b62bac63966572b224e50f97ee56c9490cde4910d"
+        let tree2 =
+              hexString
+                "01a47029e9b43722c57143a5d07681bff3e2315c9a28ad49d69e7c1f2f6e81ac160010000000000000012f4f72c03f8c937a94919a01a07f21165cc8394295291cb888ca91ed003810390107114fe4bb4cd08b47f6ae47477c182d5da9fe5c189061808c1091e9bf3b4524000001447d6b9100cddd5f80c8cf4ddee2b87eba053bd987465aec2293bd0514e68b0d015f6c95e75f4601a0a31670a7deb970fc8988c611685161d2e1629d0a1a0ebd07015f8b9205e0514fa235d75c150b87e23866b882b39786852d1ab42aab11d31a4a0117ddeb3a5f8d2f6b2d0a07f28f01ab25e03a05a9319275bb86d72fcaef6fc01501f08f39275112dd8905b854170b7f247cf2df18454d4fa94e6e4f9320cca05f24011f8322ef806eb2430dc4a7a41c1b344bea5be946efc7b4349c1c9edb14ff9d39"
+        it "Commitment tree is updated correctly" $ do
+          let t1 = updateSaplingCommitmentTree tree cmu1
+          case t1 of
+            Nothing -> assertFailure "Tree 1 failed"
+            Just t2 -> updateSaplingCommitmentTree t2 cmu2 `shouldBe` Just tree2
 
 -- | Properties
 prop_PhraseLength :: Property