WIP: add support for transparent-source-only addresses.

Signed-off-by: Daira-Emma Hopwood <[email protected]>

zcash_client_backend/CHANGELOG.md

@@ -76,6 +76,8 @@ and this library adheres to Rust's notion of
     constraint on its `<AccountId>` parameter has been strengthened to `Copy`.
 - `zcash_client_backend::fees`:
   - Arguments to `ChangeStrategy::compute_balance` have changed.
+- `zcash_client_backend::input_selection::GreedyInputSelectorError` has a
+  new variant `UnsupportedTransparentSourceOnlyAddress`.
 - `zcash_client_backend::proto`:
   - `ProposalDecodingError` has a new variant `TransparentMemo`.
 - `zcash_client_backend::zip321::render::amount_str` now takes a

zcash_client_backend/src/data_api/wallet.rs

@@ -1032,6 +1032,9 @@ where
                 }
                 transparent_output_meta.push((to, payment.amount));
             }
+            Address::TransparentSourceOnly(_) => {
+                panic!("Transparent-source-only addresses should not occur at this stage");
+            }
         }
     }
 

zcash_client_backend/src/data_api/wallet/input_selection.rs

@@ -31,7 +31,13 @@ use crate::{
 
 #[cfg(feature = "transparent-inputs")]
 use {
-    std::collections::BTreeSet, std::convert::Infallible,
+    crate::{
+        fees::TransactionBalance,
+        proposal::{StepOutput, StepOutputIndex},
+        zip321::Payment,
+    },
+    std::collections::BTreeSet,
+    std::convert::Infallible,
     zcash_primitives::legacy::TransparentAddress,
     zcash_primitives::transaction::components::OutPoint,
 };
@@ -206,6 +212,8 @@ pub enum GreedyInputSelectorError<ChangeStrategyErrT, NoteRefT> {
     Balance(BalanceError),
     /// A unified address did not contain a supported receiver.
     UnsupportedAddress(Box<UnifiedAddress>),
+    /// Support for transparent-source-only addresses requires the transparent-inputs feature.
+    UnsupportedTransparentSourceOnlyAddress,
     /// An error was encountered in change selection.
     Change(ChangeError<ChangeStrategyErrT, NoteRefT>),
 }
@@ -223,6 +231,9 @@ impl<CE: fmt::Display, N: fmt::Display> fmt::Display for GreedyInputSelectorErro
                 // don't have network parameters here
                 write!(f, "Unified address contains no supported receivers.")
             }
+            GreedyInputSelectorError::UnsupportedTransparentSourceOnlyAddress => {
+                write!(f, "Support for transparent-source-only addresses requires the transparent-inputs feature.")
+            }
             GreedyInputSelectorError::Change(err) => {
                 write!(f, "An error occurred computing change and fees: {}", err)
             }
@@ -343,6 +354,22 @@ where
         #[cfg(feature = "orchard")]
         let mut orchard_outputs = vec![];
         let mut payment_pools = BTreeMap::new();
+        #[cfg(feature = "transparent-inputs")]
+        let mut ephemeral_outputs: Vec<(usize, Payment)> = vec![];
+
+        // TR - a
+        //    - ephb
+        //    - ephc
+        //    - d
+        //
+        // becomes
+        //
+        // TR1 - a                 TR2 - b
+        //     - eph-placeholder       - c
+        //     - d                 Proposal2
+        //                             - spend from eph-placeholder
+        //
+
         for (idx, payment) in transaction_request.payments() {
             match &payment.recipient_address {
                 Address::Transparent(addr) => {
@@ -352,6 +379,28 @@ where
                         script_pubkey: addr.script(),
                     });
                 }
+                #[cfg(feature = "transparent-inputs")]
+                Address::TransparentSourceOnly(data) => {
+                    ephemeral_outputs.push((
+                        *idx,
+                        Payment {
+                            recipient_address: Address::Transparent(
+                                TransparentAddress::PublicKeyHash(*data),
+                            ),
+                            amount: payment.amount,
+                            memo: None,
+                            label: payment.label.clone(),
+                            message: payment.message.clone(),
+                            other_params: payment.other_params.clone(),
+                        },
+                    ));
+                }
+                #[cfg(not(feature = "transparent-inputs"))]
+                Address::TransparentSourceOnly(_) => {
+                    return Err(InputSelectorError::Selection(
+                        GreedyInputSelectorError::UnsupportedTransparentSourceOnlyAddress,
+                    ));
+                }
                 Address::Sapling(_) => {
                     payment_pools.insert(*idx, PoolType::Shielded(ShieldedProtocol::Sapling));
                     sapling_outputs.push(SaplingPayment(payment.amount));
@@ -386,6 +435,99 @@ where
             }
         }
 
+        #[cfg(feature = "transparent-inputs")]
+        struct Zip320SecondStep {
+            transaction_request: TransactionRequest,
+            payment_pools: BTreeMap<usize, PoolType>,
+            prior_step_inputs: StepOutput,
+            balance: TransactionBalance,
+        }
+
+        // If ephemeral state was detected, handle it here.
+        #[cfg(feature = "transparent-inputs")]
+        let (transaction_request, second_step) = if ephemeral_outputs.is_empty() {
+            (transaction_request, None)
+        } else {
+            // Construct a new TransactionRequest from `transaction_request` that excludes
+            // the ephemeral outputs, and in their place includes a single transparent
+            // output to the legacy address for this account.
+
+            let mut proposal1_excludes = BTreeSet::new();
+            let mut proposal2_payments = vec![];
+            let mut proposal2_payment_pools = BTreeMap::new();
+            let mut total_ephemeral_plus_fee: NonNegativeAmount = (|| todo!())();
+            let (first_idx, _) = ephemeral_outputs[0];
+            for (idx2, (idx1, payment)) in ephemeral_outputs.into_iter().enumerate() {
+                total_ephemeral_plus_fee = (total_ephemeral_plus_fee + payment.amount).ok_or(
+                    InputSelectorError::Selection(GreedyInputSelectorError::Balance(
+                        BalanceError::Overflow,
+                    )),
+                )?;
+                proposal1_excludes.insert(idx1);
+                proposal2_payments.push(payment);
+                proposal2_payment_pools.insert(idx2, PoolType::Transparent);
+            }
+
+            // TODO: Calculate fee for transaction request 2 and add it to
+            // total_ephemeral_plus_fee.
+
+            let proposal1_transaction_request = TransactionRequest::from_indexed(
+                transaction_request
+                    .payments()
+                    .iter()
+                    .filter_map(|(idx, payment)| {
+                        // If this is the first ephemeral output in the original request,
+                        // replace it with a transparent output to the legacy address.
+                        // We use the legacy address here only as a dummy address for the
+                        // ZIP-321 URI serialized in the proposal. It will be replaced by
+                        // a unique ephemeral P2PKH address when the proposal is created.
+                        if *idx == first_idx {
+                            let legacy_address: TransparentAddress = (|| todo!())();
+                            transparent_outputs.push(TxOut {
+                                value: total_ephemeral_plus_fee,
+                                script_pubkey: legacy_address.script(),
+                            });
+                            payment_pools.insert(first_idx, PoolType::Transparent);
+                            Some((
+                                first_idx,
+                                Payment {
+                                    recipient_address: Address::Transparent(legacy_address),
+                                    amount: total_ephemeral_plus_fee,
+                                    memo: None,
+                                    label: None,
+                                    message: None,
+                                    // TODO: Add ZIP 320 ephemeral marker, or shift this
+                                    // into being a change output (which seems to need
+                                    // changes to the Proposal protobuf, as it doesn't
+                                    // explicitly store change, or have any way to mark
+                                    // the ephemeral output).
+                                    other_params: vec![],
+                                },
+                            ))
+                        } else if proposal1_excludes.contains(&idx) {
+                            None
+                        } else {
+                            Some((*idx, payment.clone()))
+                        }
+                    })
+                    .collect(),
+            )
+            .expect("correct by construction");
+            let proposal2_transaction_request =
+                TransactionRequest::new(proposal2_payments).expect("correct by construction");
+
+            (
+                proposal1_transaction_request,
+                Some(Zip320SecondStep {
+                    transaction_request: proposal2_transaction_request,
+                    payment_pools: proposal2_payment_pools,
+                    // TODO: Update this depending on how the ephemeral output is represented.
+                    prior_step_inputs: StepOutput::new(0, StepOutputIndex::Payment(first_idx)),
+                    balance: (|| todo!())(),
+                }),
+            )
+        };
+
         let mut shielded_inputs: Vec<ReceivedNote<DbT::NoteRef, Note>> = vec![];
         let mut prior_available = NonNegativeAmount::ZERO;
         let mut amount_required = NonNegativeAmount::ZERO;
@@ -432,6 +574,16 @@ where
 
             match balance {
                 Ok(balance) => {
+                    #[cfg(feature = "transparent-inputs")]
+                    if let Some(zip320_step) = second_step {
+                        return Proposal::multi_step(
+                            (*self.change_strategy.fee_rule()).clone(),
+                            target_height,
+                            (|| todo!())(),
+                        )
+                        .map_err(InputSelectorError::Proposal);
+                    }
+
                     return Proposal::single_step(
                         transaction_request,
                         payment_pools,

zcash_client_backend/src/zip321.rs

@@ -551,7 +551,9 @@ mod parse {
                 Param::Amount(a) => payment.amount = a,
                 Param::Memo(m) => match payment.recipient_address {
                     Address::Sapling(_) | Address::Unified(_) => payment.memo = Some(m),
-                    Address::Transparent(_) => return Err(Zip321Error::TransparentMemo(i)),
+                    Address::Transparent(_) | Address::TransparentSourceOnly(_) => {
+                        return Err(Zip321Error::TransparentMemo(i))
+                    }
                 },
 
                 Param::Label(m) => payment.label = Some(m),
@@ -767,7 +769,7 @@ pub mod testing {
             other_params in btree_map(VALID_PARAMNAME, any::<String>(), 0..3),
         ) -> Payment {
             let is_shielded = match recipient_address {
-                Address::Transparent(_) => false,
+                Address::Transparent(_) | Address::TransparentSourceOnly(_) => false,
                 Address::Sapling(_) | Address::Unified(_) => true,
             };
 

zcash_client_sqlite/src/testing.rs

@@ -1266,7 +1266,9 @@ fn fake_compact_block_spending<P: consensus::Parameters, Fvk: TestFvk>(
             )
             .0,
         ),
-        Address::Transparent(_) => panic!("transparent addresses not supported in compact blocks"),
+        Address::Transparent(_) | Address::TransparentSourceOnly(_) => {
+            panic!("transparent addresses not supported in compact blocks")
+        }
         Address::Unified(ua) => {
             // This is annoying to implement, because the protocol-aware UA type has no
             // concept of ZIP 316 preference order.

zcash_client_sqlite/src/wallet/init/migrations/ufvk_support.rs

@@ -104,7 +104,7 @@ impl<P: consensus::Parameters> RusqliteMigration for Migration<P> {
                                     idx)));
                         }
                     }
-                    Address::Transparent(_) => {
+                    Address::Transparent(_) | Address::TransparentSourceOnly(_) => {
                         return Err(WalletMigrationError::CorruptedData(
                             "Address field value decoded to a transparent address; should have been Sapling or unified.".to_string()));
                     }
@@ -231,7 +231,9 @@ impl<P: consensus::Parameters> RusqliteMigration for Migration<P> {
                     Address::Sapling(_) => {
                         Ok(pool_code(PoolType::Shielded(ShieldedProtocol::Sapling)))
                     }
-                    Address::Transparent(_) => Ok(pool_code(PoolType::Transparent)),
+                    Address::Transparent(_) | Address::TransparentSourceOnly(_) => {
+                        Ok(pool_code(PoolType::Transparent))
+                    }
                     Address::Unified(_) => Err(WalletMigrationError::CorruptedData(
                         "Unified addresses should not yet appear in the sent_notes table."
                             .to_string(),

zcash_keys/src/address.rs

@@ -236,10 +236,22 @@ impl UnifiedAddress {
 /// An address that funds can be sent to.
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum Address {
+    /// A Sapling payment address.
     #[cfg(feature = "sapling")]
     Sapling(PaymentAddress),
+
+    /// A transparent address corresponding to either a public key or a `Script`.
     Transparent(TransparentAddress),
+
+    /// A [ZIP 316] Unified Address.
+    ///
+    /// [ZIP 316]: https://zips.z.cash/zip-0316
     Unified(UnifiedAddress),
+
+    /// A [ZIP 320] transparent-source-only P2PKH address, or "TEX address".
+    ///
+    /// [ZIP 320]: https://zips.z.cash/zip-0320
+    TransparentSourceOnly([u8; 20]),
 }
 
 #[cfg(feature = "sapling")]
@@ -287,6 +299,10 @@ impl TryFromRawAddress for Address {
     fn try_from_raw_transparent_p2sh(data: [u8; 20]) -> Result<Self, ConversionError<Self::Error>> {
         Ok(TransparentAddress::ScriptHash(data).into())
     }
+
+    fn try_from_raw_tex(data: [u8; 20]) -> Result<Self, ConversionError<Self::Error>> {
+        Ok(Address::TransparentSourceOnly(data))
+    }
 }
 
 impl Address {
@@ -310,6 +326,7 @@ impl Address {
                 }
             },
             Address::Unified(ua) => ua.to_address(net),
+            Address::TransparentSourceOnly(data) => ZcashAddress::from_tex(net, *data),
         }
         .to_string()
     }
@@ -320,7 +337,9 @@ impl Address {
             Address::Sapling(_) => {
                 matches!(pool_type, PoolType::Shielded(ShieldedProtocol::Sapling))
             }
-            Address::Transparent(_) => matches!(pool_type, PoolType::Transparent),
+            Address::Transparent(_) | Address::TransparentSourceOnly(_) => {
+                matches!(pool_type, PoolType::Transparent)
+            }
             Address::Unified(ua) => match pool_type {
                 PoolType::Transparent => ua.transparent().is_some(),
                 PoolType::Shielded(ShieldedProtocol::Sapling) => {
@@ -368,6 +387,7 @@ pub mod testing {
             arb_payment_address().prop_map(Address::Sapling),
             arb_transparent_addr().prop_map(Address::Transparent),
             arb_unified_addr(Network::TestNetwork, request).prop_map(Address::Unified),
+            proptest::array::uniform20(any::<u8>()).prop_map(Address::TransparentSourceOnly),
         ]
     }
 
@@ -376,6 +396,7 @@ pub mod testing {
         return prop_oneof![
             arb_transparent_addr().prop_map(Address::Transparent),
             arb_unified_addr(Network::TestNetwork, request).prop_map(Address::Unified),
+            proptest::array::uniform20(any::<u8>()).prop_map(Address::TransparentSourceOnly),
         ];
     }
 }