Fix #237

coins/monero/src/wallet/extra.rs

@@ -21,7 +21,7 @@ pub const ARBITRARY_DATA_MARKER: u8 = 127;
 pub const MAX_ARBITRARY_DATA_SIZE: usize = MAX_TX_EXTRA_NONCE_SIZE - 1;
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Zeroize)]
-pub(crate) enum PaymentId {
+pub enum PaymentId {
   Unencrypted([u8; 32]),
   Encrypted([u8; 8]),
 }
@@ -31,6 +31,7 @@ impl BitXor<[u8; 8]> for PaymentId {
 
   fn bitxor(self, bytes: [u8; 8]) -> PaymentId {
     match self {
+      // Don't perform the xor since this isn't intended to be encrypted with xor
       PaymentId::Unencrypted(_) => self,
       PaymentId::Encrypted(id) => {
         PaymentId::Encrypted((u64::from_le_bytes(id) ^ u64::from_le_bytes(bytes)).to_le_bytes())
@@ -40,7 +41,7 @@ impl BitXor<[u8; 8]> for PaymentId {
 }
 
 impl PaymentId {
-  pub(crate) fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
+  pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
     match self {
       PaymentId::Unencrypted(id) => {
         w.write_all(&[PAYMENT_ID_MARKER])?;
@@ -54,7 +55,7 @@ impl PaymentId {
     Ok(())
   }
 
-  fn read<R: Read>(r: &mut R) -> io::Result<PaymentId> {
+  pub fn read<R: Read>(r: &mut R) -> io::Result<PaymentId> {
     Ok(match read_byte(r)? {
       0 => PaymentId::Unencrypted(read_bytes(r)?),
       1 => PaymentId::Encrypted(read_bytes(r)?),
@@ -65,7 +66,7 @@ impl PaymentId {
 
 // Doesn't bother with padding nor MinerGate
 #[derive(Clone, PartialEq, Eq, Debug, Zeroize)]
-pub(crate) enum ExtraField {
+pub enum ExtraField {
   PublicKey(EdwardsPoint),
   Nonce(Vec<u8>),
   MergeMining(usize, [u8; 32]),
@@ -73,7 +74,7 @@ pub(crate) enum ExtraField {
 }
 
 impl ExtraField {
-  fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
+  pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
     match self {
       ExtraField::PublicKey(key) => {
         w.write_all(&[1])?;
@@ -96,7 +97,7 @@ impl ExtraField {
     Ok(())
   }
 
-  fn read<R: Read>(r: &mut R) -> io::Result<ExtraField> {
+  pub fn read<R: Read>(r: &mut R) -> io::Result<ExtraField> {
     Ok(match read_byte(r)? {
       1 => ExtraField::PublicKey(read_point(r)?),
       2 => ExtraField::Nonce({
@@ -118,9 +119,9 @@ impl ExtraField {
 }
 
 #[derive(Clone, PartialEq, Eq, Debug, Zeroize)]
-pub(crate) struct Extra(Vec<ExtraField>);
+pub struct Extra(Vec<ExtraField>);
 impl Extra {
-  pub(crate) fn keys(&self) -> Option<(EdwardsPoint, Option<Vec<EdwardsPoint>>)> {
+  pub fn keys(&self) -> Option<(EdwardsPoint, Option<Vec<EdwardsPoint>>)> {
     let mut key = None;
     let mut additional = None;
     for field in &self.0 {
@@ -136,7 +137,7 @@ impl Extra {
     key.map(|key| (key, additional))
   }
 
-  pub(crate) fn payment_id(&self) -> Option<PaymentId> {
+  pub fn payment_id(&self) -> Option<PaymentId> {
     for field in &self.0 {
       if let ExtraField::Nonce(data) = field {
         return PaymentId::read::<&[u8]>(&mut data.as_ref()).ok();
@@ -145,7 +146,7 @@ impl Extra {
     None
   }
 
-  pub(crate) fn data(&self) -> Vec<Vec<u8>> {
+  pub fn data(&self) -> Vec<Vec<u8>> {
     let mut res = vec![];
     for field in &self.0 {
       if let ExtraField::Nonce(data) = field {
@@ -182,14 +183,20 @@ impl Extra {
     data.iter().map(|v| 1 + varint_len(v.len()) + v.len()).sum::<usize>()
   }
 
-  pub(crate) fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
+  pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
     for field in &self.0 {
       field.write(w)?;
     }
     Ok(())
   }
 
-  pub(crate) fn read<R: Read>(r: &mut R) -> io::Result<Extra> {
+  pub fn serialize(&self) -> Vec<u8> {
+    let mut buf = vec![];
+    self.write(&mut buf).unwrap();
+    buf
+  }
+
+  pub fn read<R: Read>(r: &mut R) -> io::Result<Extra> {
     let mut res = Extra(vec![]);
     let mut field;
     while {

coins/monero/src/wallet/mod.rs

@@ -28,7 +28,9 @@ pub(crate) mod decoys;
 pub(crate) use decoys::Decoys;
 
 mod send;
-pub use send::{Fee, TransactionError, SignableTransaction, SignableTransactionBuilder};
+pub use send::{Fee, TransactionError, Change, SignableTransaction, SignableTransactionBuilder};
+#[cfg(feature = "multisig")]
+pub(crate) use send::InternalPayment;
 #[cfg(feature = "multisig")]
 pub use send::TransactionMachine;
 

coins/monero/src/wallet/send/builder.rs

@@ -5,7 +5,7 @@ use zeroize::{Zeroize, ZeroizeOnDrop};
 use crate::{
   Protocol,
   wallet::{
-    address::MoneroAddress, Fee, SpendableOutput, SignableTransaction, TransactionError,
+    address::MoneroAddress, Fee, SpendableOutput, Change, SignableTransaction, TransactionError,
     extra::MAX_ARBITRARY_DATA_SIZE,
   },
 };
@@ -17,14 +17,14 @@ struct SignableTransactionBuilderInternal {
 
   inputs: Vec<SpendableOutput>,
   payments: Vec<(MoneroAddress, u64)>,
-  change_address: Option<MoneroAddress>,
+  change_address: Option<Change>,
   data: Vec<Vec<u8>>,
 }
 
 impl SignableTransactionBuilderInternal {
   // Takes in the change address so users don't miss that they have to manually set one
   // If they don't, all leftover funds will become part of the fee
-  fn new(protocol: Protocol, fee: Fee, change_address: Option<MoneroAddress>) -> Self {
+  fn new(protocol: Protocol, fee: Fee, change_address: Option<Change>) -> Self {
     Self { protocol, fee, inputs: vec![], payments: vec![], change_address, data: vec![] }
   }
 
@@ -77,7 +77,7 @@ impl SignableTransactionBuilder {
     Self(self.0.clone())
   }
 
-  pub fn new(protocol: Protocol, fee: Fee, change_address: Option<MoneroAddress>) -> Self {
+  pub fn new(protocol: Protocol, fee: Fee, change_address: Option<Change>) -> Self {
     Self(Arc::new(RwLock::new(SignableTransactionBuilderInternal::new(
       protocol,
       fee,
@@ -117,7 +117,7 @@ impl SignableTransactionBuilder {
       read.protocol,
       read.inputs.clone(),
       read.payments.clone(),
-      read.change_address,
+      read.change_address.clone(),
       read.data.clone(),
       read.fee,
     )

coins/monero/src/wallet/send/mod.rs

@@ -1,4 +1,4 @@
-use core::ops::Deref;
+use core::{ops::Deref, fmt};
 
 use thiserror::Error;
 
@@ -8,7 +8,11 @@ use rand::seq::SliceRandom;
 use zeroize::{Zeroize, ZeroizeOnDrop, Zeroizing};
 
 use group::Group;
-use curve25519_dalek::{constants::ED25519_BASEPOINT_TABLE, scalar::Scalar, edwards::EdwardsPoint};
+use curve25519_dalek::{
+  constants::{ED25519_BASEPOINT_POINT, ED25519_BASEPOINT_TABLE},
+  scalar::Scalar,
+  edwards::EdwardsPoint,
+};
 use dalek_ff_group as dfg;
 
 #[cfg(feature = "multisig")]
@@ -25,9 +29,9 @@ use crate::{
   transaction::{Input, Output, Timelock, TransactionPrefix, Transaction},
   rpc::{Rpc, RpcError},
   wallet::{
-    address::MoneroAddress,
-    SpendableOutput, Decoys, PaymentId, ExtraField, Extra, key_image_sort, uniqueness, shared_key,
-    commitment_mask, amount_encryption,
+    address::{Network, AddressSpec, MoneroAddress},
+    ViewPair, SpendableOutput, Decoys, PaymentId, ExtraField, Extra, key_image_sort, uniqueness,
+    shared_key, commitment_mask, amount_encryption,
     extra::{ARBITRARY_DATA_MARKER, MAX_ARBITRARY_DATA_SIZE},
   },
 };
@@ -51,24 +55,23 @@ struct SendOutput {
 }
 
 impl SendOutput {
-  fn new(
-    r: &Zeroizing<Scalar>,
+  #[allow(non_snake_case)]
+  fn internal(
     unique: [u8; 32],
     output: (usize, (MoneroAddress, u64)),
+    ecdh_left: &Zeroizing<Scalar>,
+    ecdh_right: &EdwardsPoint,
+    R: EdwardsPoint,
   ) -> (SendOutput, Option<[u8; 8]>) {
     let o = output.0;
     let output = output.1;
 
     let (view_tag, shared_key, payment_id_xor) =
-      shared_key(Some(unique).filter(|_| output.0.is_guaranteed()), r, &output.0.view, o);
+      shared_key(Some(unique).filter(|_| output.0.is_guaranteed()), ecdh_left, ecdh_right, o);
 
     (
       SendOutput {
-        R: if !output.0.is_subaddress() {
-          r.deref() * &ED25519_BASEPOINT_TABLE
-        } else {
-          r.deref() * output.0.spend
-        },
+        R,
         view_tag,
         dest: ((&shared_key * &ED25519_BASEPOINT_TABLE) + output.0.spend),
         commitment: Commitment::new(commitment_mask(shared_key), output.1),
@@ -80,6 +83,39 @@ impl SendOutput {
         .map(|id| (u64::from_le_bytes(id) ^ u64::from_le_bytes(payment_id_xor)).to_le_bytes()),
     )
   }
+
+  fn new(
+    r: &Zeroizing<Scalar>,
+    unique: [u8; 32],
+    output: (usize, (MoneroAddress, u64)),
+  ) -> (SendOutput, Option<[u8; 8]>) {
+    let address = output.1 .0;
+    SendOutput::internal(
+      unique,
+      output,
+      r,
+      &address.view,
+      if !address.is_subaddress() {
+        r.deref() * &ED25519_BASEPOINT_TABLE
+      } else {
+        r.deref() * address.spend
+      },
+    )
+  }
+
+  fn change(
+    ecdh: &EdwardsPoint,
+    unique: [u8; 32],
+    output: (usize, (MoneroAddress, u64)),
+  ) -> (SendOutput, Option<[u8; 8]>) {
+    SendOutput::internal(
+      unique,
+      output,
+      &Zeroizing::new(Scalar::one()),
+      ecdh,
+      ED25519_BASEPOINT_POINT,
+    )
+  }
 }
 
 #[derive(Clone, PartialEq, Eq, Debug, Error)]
@@ -179,21 +215,66 @@ impl Fee {
 pub struct SignableTransaction {
   protocol: Protocol,
   inputs: Vec<SpendableOutput>,
-  payments: Vec<(MoneroAddress, u64)>,
+  payments: Vec<InternalPayment>,
   data: Vec<Vec<u8>>,
   fee: u64,
 }
 
+/// Specification for a change output.
+#[derive(Clone, PartialEq, Eq, Zeroize)]
+pub struct Change {
+  address: MoneroAddress,
+  view: Option<Zeroizing<Scalar>>,
+}
+
+impl fmt::Debug for Change {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    f.debug_struct("Change").field("address", &self.address).finish_non_exhaustive()
+  }
+}
+
+impl Change {
+  /// Create a change output specification from a ViewPair, as needed to maintain privacy.
+  pub fn new(view: &ViewPair, guaranteed: bool) -> Change {
+    Change {
+      address: view.address(
+        Network::Mainnet,
+        if !guaranteed {
+          AddressSpec::Standard
+        } else {
+          AddressSpec::Featured { subaddress: None, payment_id: None, guaranteed: true }
+        },
+      ),
+      view: Some(view.view.clone()),
+    }
+  }
+
+  /// Create a fingerprintable change output specification which will harm privacy. Only use this
+  /// if you know what you're doing.
+  pub fn fingerprintable(address: MoneroAddress) -> Change {
+    Change { address, view: None }
+  }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Zeroize)]
+pub(crate) enum InternalPayment {
+  Payment((MoneroAddress, u64)),
+  Change(Change, u64),
+}
+
 impl SignableTransaction {
-  /// Create a signable transaction. If the change address is specified, leftover funds will be
-  /// sent to it. If the change address isn't specified, up to 16 outputs may be specified, using
-  /// any leftover funds as a bonus to the fee. The optional data field will be embedded in TX
-  /// extra.
+  /// Create a signable transaction.
+  ///
+  /// Up to 16 outputs may be present, including the change output.
+  ///
+  /// If the change address is specified, leftover funds will be sent to it.
+  ///
+  /// Each chunk of data must not exceed MAX_ARBITRARY_DATA_SIZE.
   pub fn new(
     protocol: Protocol,
     inputs: Vec<SpendableOutput>,
     mut payments: Vec<(MoneroAddress, u64)>,
-    change_address: Option<MoneroAddress>,
+    change_address: Option<Change>,
     data: Vec<Vec<u8>>,
     fee_rate: Fee,
   ) -> Result<SignableTransaction, TransactionError> {
@@ -208,8 +289,8 @@ impl SignableTransaction {
       for payment in &payments {
         count(payment.0);
       }
-      if let Some(change) = change_address {
-        count(change);
+      if let Some(change) = change_address.as_ref() {
+        count(change.address);
       }
       if payment_ids > 1 {
         Err(TransactionError::MultiplePaymentIds)?;
@@ -232,12 +313,11 @@ impl SignableTransaction {
 
     // TODO TX MAX SIZE
 
-    // If we don't have two outputs, as required by Monero, add a second
-    let mut change = payments.len() == 1;
-    if change && change_address.is_none() {
+    // If we don't have two outputs, as required by Monero, error
+    if (payments.len() == 1) && change_address.is_none() {
       Err(TransactionError::NoChange)?;
     }
-    let outputs = payments.len() + usize::from(change);
+    let outputs = payments.len() + usize::from(change_address.is_some());
     // Add a dummy payment ID if there's only 2 payments
     has_payment_id |= outputs == 2;
 
@@ -245,37 +325,24 @@ impl SignableTransaction {
     let extra = Extra::fee_weight(outputs, has_payment_id, data.as_ref());
 
     // Calculate the fee.
-    let mut fee =
-      fee_rate.calculate(Transaction::fee_weight(protocol, inputs.len(), outputs, extra));
+    let fee = fee_rate.calculate(Transaction::fee_weight(protocol, inputs.len(), outputs, extra));
 
     // Make sure we have enough funds
     let in_amount = inputs.iter().map(|input| input.commitment().amount).sum::<u64>();
-    let mut out_amount = payments.iter().map(|payment| payment.1).sum::<u64>() + fee;
+    let out_amount = payments.iter().map(|payment| payment.1).sum::<u64>() + fee;
     if in_amount < out_amount {
       Err(TransactionError::NotEnoughFunds(in_amount, out_amount))?;
     }
 
-    // If we have yet to add a change output, do so if it's economically viable
-    if (!change) && change_address.is_some() && (in_amount != out_amount) {
-      // Check even with the new fee, there's remaining funds
-      let change_fee =
-        fee_rate.calculate(Transaction::fee_weight(protocol, inputs.len(), outputs + 1, extra)) -
-          fee;
-      if (out_amount + change_fee) < in_amount {
-        change = true;
-        out_amount += change_fee;
-        fee += change_fee;
-      }
-    }
-
-    if change {
-      payments.push((change_address.unwrap(), in_amount - out_amount));
-    }
-
-    if payments.len() > MAX_OUTPUTS {
+    if outputs > MAX_OUTPUTS {
       Err(TransactionError::TooManyOutputs)?;
     }
 
+    let mut payments = payments.drain(..).map(InternalPayment::Payment).collect::<Vec<_>>();
+    if let Some(change) = change_address {
+      payments.push(InternalPayment::Change(change, in_amount - out_amount));
+    }
+
     Ok(SignableTransaction { protocol, inputs, payments, data, fee })
   }
 
@@ -289,23 +356,93 @@ impl SignableTransaction {
 
     // Used for all non-subaddress outputs, or if there's only one subaddress output and a change
     let tx_key = Zeroizing::new(random_scalar(rng));
-    // TODO: Support not needing additional when one subaddress and non-subaddress change
-    let additional = self.payments.iter().filter(|payment| payment.0.is_subaddress()).count() != 0;
+    let mut tx_public_key = tx_key.deref() * &ED25519_BASEPOINT_TABLE;
+
+    // If any of these outputs are to a subaddress, we need keys distinct to them
+    // The only time this *does not* force having additional keys is when the only other output
+    // is a change output we have the view key for, enabling rewriting rA to aR
+    let mut has_change_view = false;
+    let subaddresses = self
+      .payments
+      .iter()
+      .filter(|payment| match *payment {
+        InternalPayment::Payment(payment) => payment.0.is_subaddress(),
+        InternalPayment::Change(change, _) => {
+          if change.view.is_some() {
+            has_change_view = true;
+            // It should not be possible to construct a change specification to a subaddress with a
+            // view key
+            debug_assert!(!change.address.is_subaddress());
+          }
+          change.address.is_subaddress()
+        }
+      })
+      .count() !=
+      0;
+
+    // We need additional keys if we have any subaddresses
+    let mut additional = subaddresses;
+    // Unless the above change view key path is taken
+    if (self.payments.len() == 2) && has_change_view {
+      additional = false;
+    }
+    let modified_change_ecdh = subaddresses && (!additional);
+
+    // If we're using the aR rewrite, update tx_public_key from rG to rB
+    if modified_change_ecdh {
+      for payment in &self.payments {
+        match payment {
+          InternalPayment::Payment(payment) => {
+            // This should be the only payment and it should be a subaddress
+            debug_assert!(payment.0.is_subaddress());
+            tx_public_key = tx_key.deref() * payment.0.spend;
+          }
+          InternalPayment::Change(_, _) => {}
+        }
+      }
+      debug_assert!(tx_public_key != (tx_key.deref() * &ED25519_BASEPOINT_TABLE));
+    }
 
     // Actually create the outputs
     let mut outputs = Vec::with_capacity(self.payments.len());
     let mut id = None;
-    for payment in self.payments.drain(..).enumerate() {
-      // If this is a subaddress, generate a dedicated r. Else, reuse the TX key
-      let dedicated = Zeroizing::new(random_scalar(&mut *rng));
-      let use_dedicated = additional && payment.1 .0.is_subaddress();
-      let r = if use_dedicated { &dedicated } else { &tx_key };
+    for (o, mut payment) in self.payments.drain(..).enumerate() {
+      // Downcast the change output to a payment output if it doesn't require special handling
+      // regarding it's view key
+      payment = if !modified_change_ecdh {
+        if let InternalPayment::Change(change, amount) = &payment {
+          InternalPayment::Payment((change.address, *amount))
+        } else {
+          payment
+        }
+      } else {
+        payment
+      };
 
-      let (mut output, payment_id) = SendOutput::new(r, uniqueness, payment);
-      // If this used the tx_key, randomize its R
-      if !use_dedicated {
-        output.R = dfg::EdwardsPoint::random(&mut *rng).0;
-      }
+      let (output, payment_id) = match payment {
+        InternalPayment::Payment(payment) => {
+          // If this is a subaddress, generate a dedicated r. Else, reuse the TX key
+          let dedicated = Zeroizing::new(random_scalar(&mut *rng));
+          let use_dedicated = additional && payment.0.is_subaddress();
+          let r = if use_dedicated { &dedicated } else { &tx_key };
+
+          let (mut output, payment_id) = SendOutput::new(r, uniqueness, (o, payment));
+          if modified_change_ecdh {
+            debug_assert_eq!(tx_public_key, output.R);
+          }
+          // If this used tx_key, randomize its R
+          if !use_dedicated {
+            output.R = dfg::EdwardsPoint::random(&mut *rng).0;
+          }
+          (output, payment_id)
+        }
+        InternalPayment::Change(change, amount) => {
+          // Instead of rA, use Ra, where R is r * subaddress_spend_key
+          // change.view must be Some as if it's None, this payment would've been downcast
+          let ecdh = tx_public_key * change.view.unwrap().deref();
+          SendOutput::change(&ecdh, uniqueness, (o, (change.address, amount)))
+        }
+      };
 
       outputs.push(output);
       id = id.or(payment_id);
@@ -330,7 +467,7 @@ impl SignableTransaction {
     // Create the TX extra
     let extra = {
       let mut extra = Extra::new(
-        tx_key.deref() * &ED25519_BASEPOINT_TABLE,
+        tx_public_key,
         if additional { outputs.iter().map(|output| output.R).collect() } else { vec![] },
       );
 

coins/monero/src/wallet/send/multisig.rs

@@ -4,6 +4,8 @@ use std::{
   collections::HashMap,
 };
 
+use zeroize::Zeroizing;
+
 use rand_core::{RngCore, CryptoRng, SeedableRng};
 use rand_chacha::ChaCha20Rng;
 
@@ -29,7 +31,9 @@ use crate::{
   },
   transaction::{Input, Transaction},
   rpc::Rpc,
-  wallet::{TransactionError, SignableTransaction, Decoys, key_image_sort, uniqueness},
+  wallet::{
+    TransactionError, InternalPayment, SignableTransaction, Decoys, key_image_sort, uniqueness,
+  },
 };
 
 /// FROST signing machine to produce a signed transaction.
@@ -108,8 +112,19 @@ impl SignableTransaction {
       transcript.append_message(b"input_shared_key", input.key_offset().to_bytes());
     }
     for payment in &self.payments {
-      transcript.append_message(b"payment_address", payment.0.to_string().as_bytes());
-      transcript.append_message(b"payment_amount", payment.1.to_le_bytes());
+      match payment {
+        InternalPayment::Payment(payment) => {
+          transcript.append_message(b"payment_address", payment.0.to_string().as_bytes());
+          transcript.append_message(b"payment_amount", payment.1.to_le_bytes());
+        }
+        InternalPayment::Change(change, amount) => {
+          transcript.append_message(b"change_address", change.address.to_string().as_bytes());
+          if let Some(view) = change.view.as_ref() {
+            transcript.append_message(b"change_view_key", Zeroizing::new(view.to_bytes()));
+          }
+          transcript.append_message(b"change_amount", amount.to_le_bytes());
+        }
+      }
     }
 
     let mut key_images = vec![];

coins/monero/tests/runner.rs

@@ -155,7 +155,7 @@ macro_rules! test {
         use monero_serai::{
           random_scalar,
           wallet::{
-            address::{Network, AddressSpec}, ViewPair, Scanner, SignableTransaction,
+            address::{Network, AddressSpec}, ViewPair, Scanner, Change, SignableTransaction,
             SignableTransactionBuilder,
           },
         };
@@ -196,7 +196,13 @@ macro_rules! test {
           let builder = SignableTransactionBuilder::new(
             rpc.get_protocol().await.unwrap(),
             rpc.get_fee().await.unwrap(),
-            Some(random_address().2),
+            Some(Change::new(
+              &ViewPair::new(
+                &random_scalar(&mut OsRng) * &ED25519_BASEPOINT_TABLE,
+                Zeroizing::new(random_scalar(&mut OsRng))
+              ),
+              false
+            )),
           );
 
           let sign = |tx: SignableTransaction| {

coins/monero/tests/send.rs

@@ -1,6 +1,7 @@
 use monero_serai::{
-  wallet::{ReceivedOutput, SpendableOutput},
+  wallet::{extra::Extra, address::SubaddressIndex, ReceivedOutput, SpendableOutput},
   transaction::Transaction,
+  rpc::Rpc,
 };
 
 mod runner;
@@ -49,3 +50,69 @@ test!(
     },
   ),
 );
+
+test!(
+  // Ideally, this would be single_R, yet it isn't feasible to apply allow(non_snake_case) here
+  single_r_subaddress_send,
+  (
+    // Consume this builder for an output we can use in the future
+    // This is needed because we can't get the input from the passed in builder
+    |_, mut builder: Builder, addr| async move {
+      builder.add_payment(addr, 1000000000000);
+      (builder.build().unwrap(), ())
+    },
+    |_, tx: Transaction, mut scanner: Scanner, _| async move {
+      let mut outputs = scanner.scan_transaction(&tx).not_locked();
+      outputs.sort_by(|x, y| x.commitment().amount.cmp(&y.commitment().amount));
+      assert_eq!(outputs[0].commitment().amount, 1000000000000);
+      outputs
+    },
+  ),
+  (
+    |rpc: Rpc, _, _, mut outputs: Vec<ReceivedOutput>| async move {
+      let change_view = ViewPair::new(
+        &random_scalar(&mut OsRng) * &ED25519_BASEPOINT_TABLE,
+        Zeroizing::new(random_scalar(&mut OsRng)),
+      );
+
+      let mut builder = SignableTransactionBuilder::new(
+        rpc.get_protocol().await.unwrap(),
+        rpc.get_fee().await.unwrap(),
+        Some(Change::new(&change_view, false)),
+      );
+      builder.add_input(SpendableOutput::from(&rpc, outputs.swap_remove(0)).await.unwrap());
+
+      // Send to a subaddress
+      let sub_view = ViewPair::new(
+        &random_scalar(&mut OsRng) * &ED25519_BASEPOINT_TABLE,
+        Zeroizing::new(random_scalar(&mut OsRng)),
+      );
+      builder.add_payment(
+        sub_view
+          .address(Network::Mainnet, AddressSpec::Subaddress(SubaddressIndex::new(0, 1).unwrap())),
+        1,
+      );
+      (builder.build().unwrap(), (change_view, sub_view))
+    },
+    |_, tx: Transaction, _, views: (ViewPair, ViewPair)| async move {
+      // Make sure the change can pick up its output
+      let mut change_scanner = Scanner::from_view(views.0, Some(HashSet::new()));
+      assert!(change_scanner.scan_transaction(&tx).not_locked().len() == 1);
+
+      // Make sure the subaddress can pick up its output
+      let mut sub_scanner = Scanner::from_view(views.1, Some(HashSet::new()));
+      sub_scanner.register_subaddress(SubaddressIndex::new(0, 1).unwrap());
+      let sub_outputs = sub_scanner.scan_transaction(&tx).not_locked();
+      assert!(sub_outputs.len() == 1);
+      assert_eq!(sub_outputs[0].commitment().amount, 1);
+
+      // Make sure only one R was included in TX extra
+      assert!(Extra::read::<&[u8]>(&mut tx.prefix.extra.as_ref())
+        .unwrap()
+        .keys()
+        .unwrap()
+        .1
+        .is_none());
+    },
+  ),
+);

coins/monero/tests/wallet2_compatibility.rs

@@ -21,7 +21,7 @@ use monero_serai::{
   transaction::Transaction,
   wallet::{
     address::{Network, AddressSpec, SubaddressIndex, MoneroAddress},
-    extra::MAX_TX_EXTRA_NONCE_SIZE,
+    extra::{MAX_TX_EXTRA_NONCE_SIZE, Extra},
     Scanner,
   },
   rpc::Rpc,
@@ -56,7 +56,7 @@ async fn initialize_rpcs() -> (WalletClient, Rpc, monero_rpc::monero::Address) {
   let wallet_rpc_addr = if address_resp.is_ok() {
     address_resp.unwrap().address
   } else {
-    wallet_rpc.create_wallet("test_wallet".to_string(), None, "English".to_string()).await.unwrap();
+    wallet_rpc.create_wallet("wallet".to_string(), None, "English".to_string()).await.unwrap();
     let addr = wallet_rpc.get_address(0, None).await.unwrap().address;
     daemon_rpc.generate_blocks(&addr.to_string(), 70).await.unwrap();
     addr
@@ -64,7 +64,7 @@ async fn initialize_rpcs() -> (WalletClient, Rpc, monero_rpc::monero::Address) {
   (wallet_rpc, daemon_rpc, wallet_rpc_addr)
 }
 
-async fn test_from_wallet_rpc_to_self(spec: AddressSpec) {
+async fn from_wallet_rpc_to_self(spec: AddressSpec) {
   // initialize rpc
   let (wallet_rpc, daemon_rpc, wallet_rpc_addr) = initialize_rpcs().await;
 
@@ -109,24 +109,23 @@ async fn test_from_wallet_rpc_to_self(spec: AddressSpec) {
 }
 
 async_sequential!(
-  async fn test_receipt_of_wallet_rpc_tx_standard() {
-    test_from_wallet_rpc_to_self(AddressSpec::Standard).await;
+  async fn receipt_of_wallet_rpc_tx_standard() {
+    from_wallet_rpc_to_self(AddressSpec::Standard).await;
   }
 
-  async fn test_receipt_of_wallet_rpc_tx_subaddress() {
-    test_from_wallet_rpc_to_self(AddressSpec::Subaddress(SubaddressIndex::new(0, 1).unwrap()))
-      .await;
+  async fn receipt_of_wallet_rpc_tx_subaddress() {
+    from_wallet_rpc_to_self(AddressSpec::Subaddress(SubaddressIndex::new(0, 1).unwrap())).await;
   }
 
-  async fn test_receipt_of_wallet_rpc_tx_integrated() {
+  async fn receipt_of_wallet_rpc_tx_integrated() {
     let mut payment_id = [0u8; 8];
     OsRng.fill_bytes(&mut payment_id);
-    test_from_wallet_rpc_to_self(AddressSpec::Integrated(payment_id)).await;
+    from_wallet_rpc_to_self(AddressSpec::Integrated(payment_id)).await;
   }
 );
 
 test!(
-  test_send_to_wallet_rpc_standard,
+  send_to_wallet_rpc_standard,
   (
     |_, mut builder: Builder, _| async move {
       // initialize rpc
@@ -151,7 +150,7 @@ test!(
 );
 
 test!(
-  test_send_to_wallet_rpc_subaddress,
+  send_to_wallet_rpc_subaddress,
   (
     |_, mut builder: Builder, _| async move {
       // initialize rpc
@@ -173,12 +172,20 @@ test!(
         data.0.get_transfer(Hash::from_slice(&tx.hash()), None).await.unwrap().unwrap();
       assert_eq!(transfer.amount.as_pico(), 1000000);
       assert_eq!(transfer.subaddr_index, Index { major: 0, minor: data.1 });
+
+      // Make sure only one R was included in TX extra
+      assert!(Extra::read::<&[u8]>(&mut tx.prefix.extra.as_ref())
+        .unwrap()
+        .keys()
+        .unwrap()
+        .1
+        .is_none());
     },
   ),
 );
 
 test!(
-  test_send_to_wallet_rpc_integrated,
+  send_to_wallet_rpc_integrated,
   (
     |_, mut builder: Builder, _| async move {
       // initialize rpc
@@ -205,7 +212,7 @@ test!(
 );
 
 test!(
-  test_send_to_wallet_rpc_with_arb_data,
+  send_to_wallet_rpc_with_arb_data,
   (
     |_, mut builder: Builder, _| async move {
       // initialize rpc

processor/src/coin/monero.rs

@@ -15,7 +15,7 @@ use monero_serai::{
   wallet::{
     ViewPair, Scanner,
     address::{Network, SubaddressIndex, AddressSpec, MoneroAddress},
-    Fee, SpendableOutput, SignableTransaction as MSignableTransaction, TransactionMachine,
+    Fee, SpendableOutput, Change, SignableTransaction as MSignableTransaction, TransactionMachine,
   },
 };
 
@@ -236,7 +236,8 @@ impl Coin for Monero {
         self.rpc.get_protocol().await.unwrap(), // TODO: Make this deterministic
         inputs.drain(..).map(|input| input.0).collect(),
         payments.to_vec(),
-        change.map(|change| self.address_internal(change, CHANGE_SUBADDRESS)),
+        change
+          .map(|change| Change::fingerprintable(self.address_internal(change, CHANGE_SUBADDRESS))),
         vec![],
         fee,
       )
@@ -316,7 +317,7 @@ impl Coin for Monero {
       self.rpc.get_protocol().await.unwrap(),
       outputs,
       vec![(address, amount - fee)],
-      Some(Self::test_address()),
+      Some(Change::new(&Self::test_view_pair(), true)),
       vec![],
       self.rpc.get_fee().await.unwrap(),
     )