zcash_primitives: Add marker types for omitting transaction parts

zcash_primitives/src/transaction/components.rs

@@ -3,6 +3,7 @@
 use std::io;
 use std::marker::PhantomData;
 
+use zcash_encoding::CompactSize;
 use zcash_protocol::value::BalanceError;
 
 pub mod amount {
@@ -42,6 +43,12 @@ pub trait ShieldedValueBalance {
     fn value_balance(&self) -> Amount;
 }
 
+impl ShieldedValueBalance for () {
+    fn value_balance(&self) -> Amount {
+        Amount::zero()
+    }
+}
+
 impl<A: ::sapling::bundle::Authorization> ShieldedValueBalance for ::sapling::Bundle<A, Amount> {
     fn value_balance(&self) -> Amount {
         *self.value_balance()
@@ -64,6 +71,23 @@ pub trait TransparentPart {
         F: FnMut(&OutPoint) -> Result<Amount, E>;
 }
 
+pub enum NoTransparent {}
+
+impl TransparentPart for NoTransparent {
+    /// Values of this type are not exposed in the public API (the transaction method is
+    /// gated off).
+    type Bundle = ();
+    type Authorization = transparent::Authorized;
+
+    fn value_balance<E, F>(_: &Self::Bundle, _: F) -> Result<Amount, E>
+    where
+        E: From<BalanceError>,
+        F: FnMut(&OutPoint) -> Result<Amount, E>,
+    {
+        Ok(Amount::zero())
+    }
+}
+
 #[derive(Debug)]
 pub struct Transparent<A: transparent::Authorization> {
     _auth: PhantomData<A>,
@@ -89,6 +113,15 @@ pub trait SaplingPart {
     type Authorization: ::sapling::bundle::Authorization;
 }
 
+pub enum NoSapling {}
+
+impl SaplingPart for NoSapling {
+    /// Values of this type are not exposed in the public API (the transaction method is
+    /// gated off).
+    type Bundle = ();
+    type Authorization = ::sapling::bundle::Authorized;
+}
+
 #[derive(Debug)]
 pub struct Sapling<A: ::sapling::bundle::Authorization> {
     _auth: PhantomData<A>,
@@ -104,6 +137,15 @@ pub trait OrchardPart {
     type Authorization: ::orchard::bundle::Authorization;
 }
 
+pub enum NoOrchard {}
+
+impl OrchardPart for NoOrchard {
+    /// Values of this type are not exposed in the public API (the transaction method is
+    /// gated off).
+    type Bundle = ();
+    type Authorization = ::orchard::bundle::Authorized;
+}
+
 #[derive(Debug)]
 pub struct Orchard<A: ::orchard::bundle::Authorization> {
     _auth: PhantomData<A>,
@@ -122,6 +164,29 @@ pub(super) trait TransparentEnc:
     fn write<W: io::Write>(bundle: Option<&Self::Bundle>, writer: W) -> io::Result<()>;
 }
 
+impl TransparentEnc for NoTransparent {
+    fn read<R: io::Read>(mut reader: R) -> io::Result<Option<Self::Bundle>> {
+        match CompactSize::read(&mut reader)? {
+            0 => match CompactSize::read(&mut reader)? {
+                0 => Ok(None),
+                n => Err(io::Error::new(
+                    io::ErrorKind::InvalidData,
+                    format!("Expected no transparent outputs, found {}", n),
+                )),
+            },
+            n => Err(io::Error::new(
+                io::ErrorKind::InvalidData,
+                format!("Expected no transparent inputs, found {}", n),
+            )),
+        }
+    }
+
+    fn write<W: io::Write>(_: Option<&Self::Bundle>, mut writer: W) -> io::Result<()> {
+        CompactSize::write(&mut writer, 0)?;
+        CompactSize::write(&mut writer, 0)
+    }
+}
+
 pub(super) trait SaplingEnc:
     SaplingPart<Authorization = ::sapling::bundle::Authorized>
 {
@@ -155,10 +220,115 @@ pub(super) trait SaplingEnc:
     fn write_v5_bundle<W: io::Write>(bundle: Option<&Self::Bundle>, writer: W) -> io::Result<()>;
 }
 
+impl SaplingEnc for NoSapling {
+    type V4Components = ();
+
+    fn read_v4_components<R: io::Read>(
+        mut reader: R,
+        tx_has_sapling: bool,
+    ) -> io::Result<Self::V4Components> {
+        if tx_has_sapling {
+            const ZERO: Amount = Amount::zero();
+
+            match super::Transaction::read_amount(&mut reader)? {
+                ZERO => match CompactSize::read(&mut reader)? {
+                    0 => match CompactSize::read(&mut reader)? {
+                        0 => Ok(()),
+                        n => Err(io::Error::new(
+                            io::ErrorKind::InvalidData,
+                            format!("Expected no Sapling Outputs, found {}", n),
+                        )),
+                    },
+                    n => Err(io::Error::new(
+                        io::ErrorKind::InvalidData,
+                        format!("Expected no Sapling Spends, found {}", n),
+                    )),
+                },
+                vb => Err(io::Error::new(
+                    io::ErrorKind::InvalidData,
+                    format!(
+                        "Expected no Sapling valueBalance, found {} zatoshis",
+                        i64::from(vb)
+                    ),
+                )),
+            }
+        } else {
+            Ok(())
+        }
+    }
+
+    fn read_v4_binding_sig<R: io::Read>(
+        _: R,
+        _: bool,
+        _: Self::V4Components,
+    ) -> io::Result<Option<Self::Bundle>> {
+        Ok(None)
+    }
+
+    fn write_v4_components<W: io::Write>(
+        _: Option<&Self::Bundle>,
+        mut writer: W,
+        tx_has_sapling: bool,
+    ) -> io::Result<()> {
+        if tx_has_sapling {
+            writer.write_all(&Amount::zero().to_i64_le_bytes())?;
+            CompactSize::write(&mut writer, 0)?;
+            CompactSize::write(&mut writer, 0)?;
+        }
+
+        Ok(())
+    }
+
+    fn write_v4_binding_sig<W: io::Write>(
+        _: Option<&Self::Bundle>,
+        _: W,
+        _: bool,
+    ) -> io::Result<()> {
+        Ok(())
+    }
+
+    fn read_v5_bundle<R: io::Read>(mut reader: R) -> io::Result<Option<Self::Bundle>> {
+        match CompactSize::read(&mut reader)? {
+            0 => match CompactSize::read(&mut reader)? {
+                0 => Ok(None),
+                n => Err(io::Error::new(
+                    io::ErrorKind::InvalidData,
+                    format!("Expected no Sapling Outputs, found {}", n),
+                )),
+            },
+            n => Err(io::Error::new(
+                io::ErrorKind::InvalidData,
+                format!("Expected no Sapling Spends, found {}", n),
+            )),
+        }
+    }
+
+    fn write_v5_bundle<W: io::Write>(_: Option<&Self::Bundle>, mut writer: W) -> io::Result<()> {
+        CompactSize::write(&mut writer, 0)?;
+        CompactSize::write(&mut writer, 0)
+    }
+}
+
 pub(super) trait OrchardEnc:
     OrchardPart<Authorization = ::orchard::bundle::Authorized>
 {
     fn read_v5_bundle<R: io::Read>(reader: R) -> io::Result<Option<Self::Bundle>>;
 
     fn write_v5_bundle<W: io::Write>(bundle: Option<&Self::Bundle>, writer: W) -> io::Result<()>;
 }
+
+impl OrchardEnc for NoOrchard {
+    fn read_v5_bundle<R: io::Read>(reader: R) -> io::Result<Option<Self::Bundle>> {
+        match CompactSize::read(reader)? {
+            0 => Ok(None),
+            n => Err(io::Error::new(
+                io::ErrorKind::InvalidData,
+                format!("Expected no Orchard Actions, found {}", n),
+            )),
+        }
+    }
+
+    fn write_v5_bundle<W: io::Write>(_: Option<&Self::Bundle>, writer: W) -> io::Result<()> {
+        CompactSize::write(writer, 0)
+    }
+}

zcash_primitives/src/transaction/sighash_v4.rs

@@ -15,7 +15,8 @@ use super::{
         sapling as sapling_serialization,
         sprout::JsDescription,
         transparent::{self, TxIn, TxOut},
-        OrchardPart, Sapling, SaplingPart, ShieldedValueBalance, Transparent, TransparentPart,
+        NoSapling, NoTransparent, OrchardPart, Sapling, SaplingPart, ShieldedValueBalance,
+        Transparent, TransparentPart,
     },
     sighash::{SignableInput, SIGHASH_ANYONECANPAY, SIGHASH_MASK, SIGHASH_NONE, SIGHASH_SINGLE},
     TransactionData,
@@ -57,6 +58,37 @@ pub trait TransparentSigDigester: TransparentPart {
     ) -> Vec<u8>;
 }
 
+impl TransparentSigDigester for NoTransparent {
+    fn digest_prevout(_: Option<&Self::Bundle>) -> Blake2bHash {
+        Blake2bParams::new()
+            .hash_length(32)
+            .personal(ZCASH_PREVOUTS_HASH_PERSONALIZATION)
+            .hash(&[])
+    }
+
+    fn digest_sequence(_: Option<&Self::Bundle>) -> Blake2bHash {
+        Blake2bParams::new()
+            .hash_length(32)
+            .personal(ZCASH_SEQUENCE_HASH_PERSONALIZATION)
+            .hash(&[])
+    }
+
+    fn digest_outputs(_: Option<&Self::Bundle>) -> Blake2bHash {
+        Blake2bParams::new()
+            .hash_length(32)
+            .personal(ZCASH_OUTPUTS_HASH_PERSONALIZATION)
+            .hash(&[])
+    }
+
+    fn digest_single_output(_: Option<&Self::Bundle>, _: &SignableInput<'_>) -> [u8; 32] {
+        [0; 32]
+    }
+
+    fn digest_signable_input(_: Option<&Self::Bundle>, _: &SignableInput<'_>) -> Vec<u8> {
+        panic!("A request has been made to sign a transparent input, but none are present.");
+    }
+}
+
 impl<A: transparent::Authorization> TransparentSigDigester for Transparent<A> {
     fn digest_prevout(transparent_bundle: Option<&Self::Bundle>) -> Blake2bHash {
         prevout_hash(transparent_bundle.map_or(&[], |b| b.vin.as_slice()))
@@ -190,6 +222,16 @@ pub trait SaplingSigDigester: SaplingPart {
     fn digest_outputs(sapling_bundle: Option<&Self::Bundle>) -> [u8; 32];
 }
 
+impl SaplingSigDigester for NoSapling {
+    fn digest_spends(_: Option<&Self::Bundle>) -> [u8; 32] {
+        [0; 32]
+    }
+
+    fn digest_outputs(_: Option<&Self::Bundle>) -> [u8; 32] {
+        [0; 32]
+    }
+}
+
 impl<A> SaplingSigDigester for Sapling<A>
 where
     A: sapling::bundle::Authorization<SpendProof = GrothProofBytes, OutputProof = GrothProofBytes>,

zcash_primitives/src/transaction/sighash_v5.rs

@@ -6,7 +6,7 @@ use zcash_encoding::Array;
 use crate::transaction::{
     components::{
         transparent::{self, TxOut},
-        OrchardPart, SaplingPart, Transparent, TransparentPart,
+        NoTransparent, OrchardPart, SaplingPart, Transparent, TransparentPart,
     },
     sighash::{
         SignableInput, TransparentAuthorizingContext, SIGHASH_ANYONECANPAY, SIGHASH_MASK,
@@ -47,6 +47,15 @@ pub trait TransparentSigDigester: TransparentPart {
     ) -> Blake2bHash;
 }
 
+impl TransparentSigDigester for NoTransparent {
+    fn digest(
+        _: Option<(&Self::Bundle, &TransparentDigests<Blake2bHash>)>,
+        _: &SignableInput<'_>,
+    ) -> Blake2bHash {
+        hash_transparent_txid_data(None)
+    }
+}
+
 impl<A: TransparentAuthorizingContext> TransparentSigDigester for Transparent<A> {
     fn digest(
         tx_data: Option<(&Self::Bundle, &TransparentDigests<Blake2bHash>)>,

zcash_primitives/src/transaction/txid.rs

@@ -19,7 +19,8 @@ use super::{
     components::{
         amount::Amount,
         transparent::{self, TxIn, TxOut},
-        Orchard, OrchardPart, Sapling, SaplingPart, Transparent, TransparentPart,
+        NoOrchard, NoSapling, NoTransparent, Orchard, OrchardPart, Sapling, SaplingPart,
+        Transparent, TransparentPart,
     },
     TransactionDigest, TransparentDigests, TxDigests, TxId, TxVersion,
 };
@@ -204,6 +205,12 @@ trait TransparentDigester: TransparentPart {
         -> Option<TransparentDigests<Blake2bHash>>;
 }
 
+impl TransparentDigester for NoTransparent {
+    fn digest(_: Option<&Self::Bundle>) -> Option<TransparentDigests<Blake2bHash>> {
+        None
+    }
+}
+
 impl<A: transparent::Authorization> TransparentDigester for Transparent<A> {
     fn digest(
         transparent_bundle: Option<&Self::Bundle>,
@@ -272,6 +279,12 @@ trait SaplingDigester: SaplingPart {
     fn digest(sapling_bundle: Option<&Self::Bundle>) -> Option<Blake2bHash>;
 }
 
+impl SaplingDigester for NoSapling {
+    fn digest(_: Option<&Self::Bundle>) -> Option<Blake2bHash> {
+        None
+    }
+}
+
 impl<A: sapling::bundle::Authorization> SaplingDigester for Sapling<A> {
     fn digest(sapling_bundle: Option<&Self::Bundle>) -> Option<Blake2bHash> {
         sapling_bundle.map(hash_sapling_txid_data)
@@ -303,6 +316,12 @@ trait OrchardDigester: OrchardPart {
     fn digest(orchard_bundle: Option<&Self::Bundle>) -> Option<Blake2bHash>;
 }
 
+impl OrchardDigester for NoOrchard {
+    fn digest(_: Option<&Self::Bundle>) -> Option<Blake2bHash> {
+        None
+    }
+}
+
 impl<A: orchard::Authorization> OrchardDigester for Orchard<A> {
     fn digest(orchard_bundle: Option<&Self::Bundle>) -> Option<Blake2bHash> {
         orchard_bundle.map(|b| b.commitment().0)