Remove `MemoBytes` usage from `zcash_primitives::sapling`

zcash_client_backend/src/decrypt.rs

@@ -96,7 +96,7 @@ pub fn decrypt_transaction<P: consensus::Parameters>(
                                     index,
                                     note,
                                     account,
-                                    memo,
+                                    memo: MemoBytes::from_bytes(&memo).expect("correct length"),
                                     transfer_type,
                                 })
                         })

zcash_client_backend/src/scanning.rs

@@ -739,7 +739,7 @@ mod tests {
         let encryptor = sapling_note_encryption(
             Some(dfvk.fvk().ovk),
             note.clone(),
-            MemoBytes::empty(),
+            *MemoBytes::empty().as_array(),
             &mut rng,
         );
         let cmu = note.cmu().to_bytes().to_vec();

zcash_client_sqlite/src/testing.rs

@@ -779,7 +779,7 @@ pub(crate) fn fake_compact_block<P: consensus::Parameters>(
     let encryptor = sapling_note_encryption(
         Some(dfvk.fvk().ovk),
         note.clone(),
-        MemoBytes::empty(),
+        *MemoBytes::empty().as_array(),
         &mut rng,
     );
     let cmu = note.cmu().to_bytes().to_vec();
@@ -886,7 +886,7 @@ pub(crate) fn fake_compact_block_spending<P: consensus::Parameters>(
         let encryptor = sapling_note_encryption(
             Some(dfvk.fvk().ovk),
             note.clone(),
-            MemoBytes::empty(),
+            *MemoBytes::empty().as_array(),
             &mut rng,
         );
         let cmu = note.cmu().to_bytes().to_vec();
@@ -912,7 +912,7 @@ pub(crate) fn fake_compact_block_spending<P: consensus::Parameters>(
         let encryptor = sapling_note_encryption(
             Some(dfvk.fvk().ovk),
             note.clone(),
-            MemoBytes::empty(),
+            *MemoBytes::empty().as_array(),
             &mut rng,
         );
         let cmu = note.cmu().to_bytes().to_vec();

zcash_client_sqlite/src/wallet/sapling.rs

@@ -1040,7 +1040,13 @@ pub(crate) mod tests {
                 );
 
                 if result.is_some() {
-                    return Ok(result);
+                    return Ok(result.map(|(note, addr, memo)| {
+                        (
+                            note,
+                            addr,
+                            MemoBytes::from_bytes(&memo).expect("correct length"),
+                        )
+                    }));
                 }
             }
 

zcash_primitives/CHANGELOG.md

@@ -112,6 +112,8 @@ and this library adheres to Rust's notion of
   - `builder::SaplingBuilder::new` now takes a `Zip212Enforcement` argument
     instead of a `P: consensus::Parameters` argument and a target height.
   - `builder::SaplingBuilder::add_spend` now takes `extsk` by reference.
+  - `builder::SaplingBuilder::add_output` now takes an `Option<[u8; 512]>` memo
+    instead of a `MemoBytes`.
   - `builder::SaplingBuilder::build` no longer takes a prover, proving context,
     progress notifier, or target height. Instead, it has `SpendProver, OutputProver`
     generic parameters and returns `(UnauthorizedBundle, SaplingMetadata)`. The
@@ -137,6 +139,13 @@ and this library adheres to Rust's notion of
       - `try_sapling_compact_note_decryption`
       - `try_sapling_output_recovery_with_ock`
       - `try_sapling_output_recovery`
+    - `SaplingDomain::Memo` now has type `[u8; 512]` instead of `MemoBytes`.
+    - `sapling_note_encryption` now takes `memo` as a `[u8; 512]` instead of
+      `MemoBytes`.
+    - The following methods now return `[u8; 512]` instead of `MemoBytes`:
+      - `try_sapling_note_decryption`
+      - `try_sapling_output_recovery_with_ock`
+      - `try_sapling_output_recovery`
   - `util::generate_random_rseed` now takes a `Zip212Enforcement` argument
     instead of a `P: consensus::Parameters` argument and a height.
 - `zcash_primitives::transaction`:

zcash_primitives/benches/note_decryption.rs

@@ -6,7 +6,6 @@ use rand_core::OsRng;
 use zcash_note_encryption::batch;
 use zcash_primitives::{
     consensus::{sapling_zip212_enforcement, NetworkUpgrade::Canopy, Parameters, TEST_NETWORK},
-    memo::MemoBytes,
     sapling::{
         builder::SaplingBuilder,
         note_encryption::{
@@ -38,13 +37,7 @@ fn bench_note_decryption(c: &mut Criterion) {
 
         let mut builder = SaplingBuilder::new(zip212_enforcement);
         builder
-            .add_output(
+            .add_output(&mut rng, None, pa, NoteValue::from_raw(100), None)
-                &mut rng,
-                None,
-                pa,
-                NoteValue::from_raw(100),
-                MemoBytes::empty(),
-            )
             .unwrap();
         let (bundle, _) = builder
             .build::<MockSpendProver, MockOutputProver, _, Amount>(&mut rng)

zcash_primitives/src/sapling/builder.rs

@@ -9,7 +9,6 @@ use rand_core::CryptoRng;
 
 use crate::{
     keys::OutgoingViewingKey,
-    memo::MemoBytes,
     sapling::{
         self,
         bundle::{
@@ -165,7 +164,7 @@ struct SaplingOutputInfo {
     /// `None` represents the `ovk = ⊥` case.
     ovk: Option<OutgoingViewingKey>,
     note: Note,
-    memo: MemoBytes,
+    memo: Option<[u8; 512]>,
     rcv: ValueCommitTrapdoor,
 }
 
@@ -188,7 +187,7 @@ impl SaplingOutputInfo {
             None,
             dummy_to,
             NoteValue::from_raw(0),
-            MemoBytes::empty(),
+            None,
             zip212_enforcement,
         )
     }
@@ -198,7 +197,7 @@ impl SaplingOutputInfo {
         ovk: Option<OutgoingViewingKey>,
         to: PaymentAddress,
         value: NoteValue,
-        memo: MemoBytes,
+        memo: Option<[u8; 512]>,
         zip212_enforcement: Zip212Enforcement,
     ) -> Self {
         let rseed = generate_random_rseed_internal(zip212_enforcement, rng);
@@ -217,7 +216,16 @@ impl SaplingOutputInfo {
         self,
         rng: &mut R,
     ) -> OutputDescription<sapling::circuit::Output> {
-        let encryptor = sapling_note_encryption::<R>(self.ovk, self.note.clone(), self.memo, rng);
+        let encryptor = sapling_note_encryption::<R>(
+            self.ovk,
+            self.note.clone(),
+            self.memo.unwrap_or_else(|| {
+                let mut memo = [0; 512];
+                memo[0] = 0xf6;
+                memo
+            }),
+            rng,
+        );
 
         // Construct the value commitment.
         let cv = ValueCommitment::derive(self.note.value(), self.rcv.clone());
@@ -396,7 +404,7 @@ impl SaplingBuilder {
         ovk: Option<OutgoingViewingKey>,
         to: PaymentAddress,
         value: NoteValue,
-        memo: MemoBytes,
+        memo: Option<[u8; 512]>,
     ) -> Result<(), Error> {
         let output = SaplingOutputInfo::new_internal(
             &mut rng,

zcash_primitives/src/sapling/note_encryption.rs

@@ -15,9 +15,7 @@ use zcash_note_encryption::{
     ENC_CIPHERTEXT_SIZE, NOTE_PLAINTEXT_SIZE, OUT_PLAINTEXT_SIZE,
 };
 
-use crate::{
+use crate::sapling::{
-    memo::MemoBytes,
-    sapling::{
     bundle::{GrothProofBytes, OutputDescription},
     keys::{
         DiversifiedTransmissionKey, EphemeralPublicKey, EphemeralSecretKey, OutgoingViewingKey,
@@ -25,7 +23,6 @@ use crate::{
     },
     value::{NoteValue, ValueCommitment},
     Diversifier, Note, PaymentAddress, Rseed,
-    },
 };
 
 use super::note::ExtractedNoteCommitment;
@@ -145,7 +142,7 @@ impl Domain for SaplingDomain {
     type ValueCommitment = ValueCommitment;
     type ExtractedCommitment = ExtractedNoteCommitment;
     type ExtractedCommitmentBytes = [u8; 32];
-    type Memo = MemoBytes;
+    type Memo = [u8; 512];
 
     fn derive_esk(note: &Self::Note) -> Option<Self::EphemeralSecretKey> {
         note.derive_esk()
@@ -209,7 +206,7 @@ impl Domain for SaplingDomain {
             }
         }
 
-        input[COMPACT_NOTE_SIZE..NOTE_PLAINTEXT_SIZE].copy_from_slice(&memo.as_array()[..]);
+        input[COMPACT_NOTE_SIZE..NOTE_PLAINTEXT_SIZE].copy_from_slice(&memo[..]);
 
         NotePlaintextBytes(input)
     }
@@ -286,7 +283,9 @@ impl Domain for SaplingDomain {
     }
 
     fn extract_memo(&self, plaintext: &NotePlaintextBytes) -> Self::Memo {
-        MemoBytes::from_bytes(&plaintext.0[COMPACT_NOTE_SIZE..NOTE_PLAINTEXT_SIZE]).unwrap()
+        plaintext.0[COMPACT_NOTE_SIZE..NOTE_PLAINTEXT_SIZE]
+            .try_into()
+            .expect("correct length")
     }
 }
 
@@ -361,7 +360,6 @@ impl ShieldedOutput<SaplingDomain, COMPACT_NOTE_SIZE> for CompactOutputDescripti
 /// use zcash_primitives::{
 ///     keys::{OutgoingViewingKey, prf_expand},
 ///     consensus::{TEST_NETWORK, NetworkUpgrade, Parameters},
-///     memo::MemoBytes,
 ///     sapling::{
 ///         note_encryption::{sapling_note_encryption, Zip212Enforcement},
 ///         util::generate_random_rseed,
@@ -388,14 +386,14 @@ impl ShieldedOutput<SaplingDomain, COMPACT_NOTE_SIZE> for CompactOutputDescripti
 /// let note = to.create_note(value, rseed);
 /// let cmu = note.cmu();
 ///
-/// let mut enc = sapling_note_encryption(ovk, note, MemoBytes::empty(), &mut rng);
+/// let mut enc = sapling_note_encryption(ovk, note, [0x37; 512], &mut rng);
 /// let encCiphertext = enc.encrypt_note_plaintext();
 /// let outCiphertext = enc.encrypt_outgoing_plaintext(&cv, &cmu, &mut rng);
 /// ```
 pub fn sapling_note_encryption<R: RngCore>(
     ovk: Option<OutgoingViewingKey>,
     note: Note,
-    memo: MemoBytes,
+    memo: [u8; 512],
     rng: &mut R,
 ) -> NoteEncryption<SaplingDomain> {
     let esk = note.generate_or_derive_esk_internal(rng);
@@ -416,7 +414,7 @@ pub fn try_sapling_note_decryption<Output: ShieldedOutput<SaplingDomain, ENC_CIP
     ivk: &PreparedIncomingViewingKey,
     output: &Output,
     zip212_enforcement: Zip212Enforcement,
-) -> Option<(Note, PaymentAddress, MemoBytes)> {
+) -> Option<(Note, PaymentAddress, [u8; 512])> {
     let domain = SaplingDomain::new(zip212_enforcement);
     try_note_decryption(&domain, ivk, output)
 }
@@ -444,7 +442,7 @@ pub fn try_sapling_output_recovery_with_ock(
     ock: &OutgoingCipherKey,
     output: &OutputDescription<GrothProofBytes>,
     zip212_enforcement: Zip212Enforcement,
-) -> Option<(Note, PaymentAddress, MemoBytes)> {
+) -> Option<(Note, PaymentAddress, [u8; 512])> {
     let domain = SaplingDomain::new(zip212_enforcement);
     try_output_recovery_with_ock(&domain, ock, output, output.out_ciphertext())
 }
@@ -461,7 +459,7 @@ pub fn try_sapling_output_recovery(
     ovk: &OutgoingViewingKey,
     output: &OutputDescription<GrothProofBytes>,
     zip212_enforcement: Zip212Enforcement,
-) -> Option<(Note, PaymentAddress, MemoBytes)> {
+) -> Option<(Note, PaymentAddress, [u8; 512])> {
     let domain = SaplingDomain::new(zip212_enforcement);
     try_output_recovery_with_ovk(&domain, ovk, output, output.cv(), output.out_ciphertext())
 }
@@ -492,7 +490,6 @@ mod tests {
 
     use crate::{
         keys::OutgoingViewingKey,
-        memo::MemoBytes,
         sapling::{
             bundle::{GrothProofBytes, OutputDescription},
             keys::{DiversifiedTransmissionKey, EphemeralSecretKey},
@@ -561,7 +558,7 @@ mod tests {
         let cmu = note.cmu();
 
         let ovk = OutgoingViewingKey([0; 32]);
-        let ne = sapling_note_encryption(Some(ovk), note, MemoBytes::empty(), &mut rng);
+        let ne = sapling_note_encryption(Some(ovk), note, [0x37; 512], &mut rng);
         let epk = ne.epk();
         let ock = prf_ock(&ovk, &cv, &cmu.to_bytes(), &epk.to_bytes());
 
@@ -1415,7 +1412,7 @@ mod tests {
                 Some((decrypted_note, decrypted_to, decrypted_memo)) => {
                     assert_eq!(decrypted_note, note);
                     assert_eq!(decrypted_to, to);
-                    assert_eq!(&decrypted_memo.as_array()[..], &tv.memo[..]);
+                    assert_eq!(&decrypted_memo[..], &tv.memo[..]);
                 }
                 None => panic!("Note decryption failed"),
             }
@@ -1436,7 +1433,7 @@ mod tests {
                 Some((decrypted_note, decrypted_to, decrypted_memo)) => {
                     assert_eq!(decrypted_note, note);
                     assert_eq!(decrypted_to, to);
-                    assert_eq!(&decrypted_memo.as_array()[..], &tv.memo[..]);
+                    assert_eq!(&decrypted_memo[..], &tv.memo[..]);
                 }
                 None => panic!("Output recovery failed"),
             }
@@ -1449,7 +1446,7 @@ mod tests {
                 [Some(((decrypted_note, decrypted_to, decrypted_memo), i))] => {
                     assert_eq!(decrypted_note, &note);
                     assert_eq!(decrypted_to, &to);
-                    assert_eq!(&decrypted_memo.as_array()[..], &tv.memo[..]);
+                    assert_eq!(&decrypted_memo[..], &tv.memo[..]);
                     assert_eq!(*i, 0);
                 }
                 _ => panic!("Note decryption failed"),
@@ -1475,12 +1472,7 @@ mod tests {
             // Test encryption
             //
 
-            let ne = NoteEncryption::<SaplingDomain>::new_with_esk(
+            let ne = NoteEncryption::<SaplingDomain>::new_with_esk(esk, Some(ovk), note, tv.memo);
-                esk,
-                Some(ovk),
-                note,
-                MemoBytes::from_bytes(&tv.memo).unwrap(),
-            );
 
             assert_eq!(ne.encrypt_note_plaintext().as_ref(), &tv.c_enc[..]);
             assert_eq!(

zcash_primitives/src/transaction/builder.rs

@@ -356,7 +356,7 @@ impl<'a, P: consensus::Parameters, R: RngCore + CryptoRng> Builder<'a, P, R> {
             ovk,
             to,
             sapling::value::NoteValue::from_raw(value.into()),
-            memo,
+            Some(*memo.as_array()),
         )
     }