Merge pull request #1007 from zcash/sapling-trymapauth-etc

Changes to Sapling bundle mapping

zcash_primitives/CHANGELOG.md

@@ -12,9 +12,20 @@ and this library adheres to Rust's notion of
   - `circuit` module (moved from `zcash_proofs::circuit::sapling`).
   - `constants` module.
   - `prover::{SpendProver, OutputProver}`
+  - `impl Debug for keys::{ExpandedSpendingKey, ProofGenerationKey}`
+- `zcash_primitives::transaction::components::sapling`:
+  - `Bundle::try_map_authorization`
+  - `TryMapAuth`
+  - `impl {MapAuth, TryMapAuth} for (FnMut, FnMut, FnMut, FnMut)` helpers to
+    enable calling `Bundle::{map_authorization, try_map_authorization}` with a
+    set of closures.
 - Test helpers, behind the `test-dependencies` feature flag:
   - `zcash_primitives::prover::mock::{MockSpendProver, MockOutputProver}`
 
+### Changed
+- `zcash_primitives::transaction::components::sapling`:
+  - `MapAuth` trait methods now take `&mut self` instead of `&self`.
+
 ### Removed
 - `zcash_primitives::constants`:
   - All `const` values (moved to `zcash_primitives::sapling::constants`).

zcash_primitives/src/sapling/circuit.rs

@@ -1,5 +1,7 @@
 //! The Sapling circuits.
 
+use core::fmt;
+
 use group::{ff::PrimeField, Curve};
 
 use bellman::{Circuit, ConstraintSystem, SynthesisError};
@@ -46,6 +48,7 @@ impl ValueCommitmentOpening {
 }
 
 /// This is an instance of the `Spend` circuit.
+#[derive(Clone)]
 pub struct Spend {
     /// The opening of a Pedersen commitment to the value being spent.
     pub value_commitment_opening: Option<ValueCommitmentOpening>,
@@ -71,7 +74,16 @@ pub struct Spend {
     pub anchor: Option<bls12_381::Scalar>,
 }
 
+impl fmt::Debug for Spend {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Spend")
+            .field("anchor", &self.anchor)
+            .finish_non_exhaustive()
+    }
+}
+
 /// This is an output circuit instance.
+#[derive(Clone)]
 pub struct Output {
     /// The opening of a Pedersen commitment to the value being spent.
     pub value_commitment_opening: Option<ValueCommitmentOpening>,
@@ -86,6 +98,12 @@ pub struct Output {
     pub esk: Option<jubjub::Fr>,
 }
 
+impl fmt::Debug for Output {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Output").finish_non_exhaustive()
+    }
+}
+
 /// Exposes a Pedersen commitment to the value as an
 /// input to the circuit
 fn expose_value_commitment<CS>(

zcash_primitives/src/sapling/keys.rs

@@ -4,6 +4,7 @@
 //!
 //! [section 4.2.2]: https://zips.z.cash/protocol/protocol.pdf#saplingkeycomponents
 
+use std::fmt;
 use std::io::{self, Read, Write};
 
 use super::{
@@ -46,6 +47,13 @@ pub struct ExpandedSpendingKey {
     pub ovk: OutgoingViewingKey,
 }
 
+impl fmt::Debug for ExpandedSpendingKey {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("ExpandedSpendingKey")
+            .finish_non_exhaustive()
+    }
+}
+
 impl ExpandedSpendingKey {
     pub fn from_spending_key(sk: &[u8]) -> Self {
         let ask = jubjub::Fr::from_bytes_wide(prf_expand(sk, &[0x00]).as_array());
@@ -119,6 +127,14 @@ pub struct ProofGenerationKey {
     pub nsk: jubjub::Fr,
 }
 
+impl fmt::Debug for ProofGenerationKey {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("ProofGenerationKey")
+            .field("ak", &self.ak)
+            .finish_non_exhaustive()
+    }
+}
+
 impl ProofGenerationKey {
     pub fn to_viewing_key(&self) -> ViewingKey {
         ViewingKey {
@@ -473,16 +489,9 @@ impl SharedSecret {
 pub mod testing {
     use proptest::collection::vec;
     use proptest::prelude::*;
-    use std::fmt::{self, Debug, Formatter};
 
     use super::{ExpandedSpendingKey, FullViewingKey, SaplingIvk};
 
-    impl Debug for ExpandedSpendingKey {
-        fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-            write!(f, "Spending keys cannot be Debug-formatted.")
-        }
-    }
-
     prop_compose! {
         pub fn arb_expanded_spending_key()(v in vec(any::<u8>(), 32..252)) -> ExpandedSpendingKey {
             ExpandedSpendingKey::from_spending_key(&v)

zcash_primitives/src/transaction/components/sapling.rs

@@ -56,11 +56,14 @@ impl Authorization for Authorized {
     type AuthSig = redjubjub::Signature;
 }
 
+/// A map from one bundle authorization to another.
+///
+/// For use with [`Bundle::map_authorization`].
 pub trait MapAuth<A: Authorization, B: Authorization> {
-    fn map_spend_proof(&self, p: A::SpendProof) -> B::SpendProof;
-    fn map_output_proof(&self, p: A::OutputProof) -> B::OutputProof;
-    fn map_auth_sig(&self, s: A::AuthSig) -> B::AuthSig;
-    fn map_authorization(&self, a: A) -> B;
+    fn map_spend_proof(&mut self, p: A::SpendProof) -> B::SpendProof;
+    fn map_output_proof(&mut self, p: A::OutputProof) -> B::OutputProof;
+    fn map_auth_sig(&mut self, s: A::AuthSig) -> B::AuthSig;
+    fn map_authorization(&mut self, a: A) -> B;
 }
 
 /// The identity map.
@@ -71,31 +74,98 @@ pub trait MapAuth<A: Authorization, B: Authorization> {
 /// [`TransactionData::map_authorization`]: crate::transaction::TransactionData::map_authorization
 impl MapAuth<Authorized, Authorized> for () {
     fn map_spend_proof(
-        &self,
+        &mut self,
         p: <Authorized as Authorization>::SpendProof,
     ) -> <Authorized as Authorization>::SpendProof {
         p
     }
 
     fn map_output_proof(
-        &self,
+        &mut self,
         p: <Authorized as Authorization>::OutputProof,
     ) -> <Authorized as Authorization>::OutputProof {
         p
     }
 
     fn map_auth_sig(
-        &self,
+        &mut self,
         s: <Authorized as Authorization>::AuthSig,
     ) -> <Authorized as Authorization>::AuthSig {
         s
     }
 
-    fn map_authorization(&self, a: Authorized) -> Authorized {
+    fn map_authorization(&mut self, a: Authorized) -> Authorized {
         a
     }
 }
 
+/// A helper for implementing `MapAuth` with a set of closures.
+impl<A, B, F, G, H, I> MapAuth<A, B> for (F, G, H, I)
+where
+    A: Authorization,
+    B: Authorization,
+    F: FnMut(A::SpendProof) -> B::SpendProof,
+    G: FnMut(A::OutputProof) -> B::OutputProof,
+    H: FnMut(A::AuthSig) -> B::AuthSig,
+    I: FnMut(A) -> B,
+{
+    fn map_spend_proof(&mut self, p: A::SpendProof) -> B::SpendProof {
+        self.0(p)
+    }
+
+    fn map_output_proof(&mut self, p: A::OutputProof) -> B::OutputProof {
+        self.1(p)
+    }
+
+    fn map_auth_sig(&mut self, s: A::AuthSig) -> B::AuthSig {
+        self.2(s)
+    }
+
+    fn map_authorization(&mut self, a: A) -> B {
+        self.3(a)
+    }
+}
+
+/// A fallible map from one bundle authorization to another.
+///
+/// For use with [`Bundle::try_map_authorization`].
+pub trait TryMapAuth<A: Authorization, B: Authorization> {
+    type Error;
+    fn try_map_spend_proof(&mut self, p: A::SpendProof) -> Result<B::SpendProof, Self::Error>;
+    fn try_map_output_proof(&mut self, p: A::OutputProof) -> Result<B::OutputProof, Self::Error>;
+    fn try_map_auth_sig(&mut self, s: A::AuthSig) -> Result<B::AuthSig, Self::Error>;
+    fn try_map_authorization(&mut self, a: A) -> Result<B, Self::Error>;
+}
+
+/// A helper for implementing `TryMapAuth` with a set of closures.
+impl<A, B, E, F, G, H, I> TryMapAuth<A, B> for (F, G, H, I)
+where
+    A: Authorization,
+    B: Authorization,
+    F: FnMut(A::SpendProof) -> Result<B::SpendProof, E>,
+    G: FnMut(A::OutputProof) -> Result<B::OutputProof, E>,
+    H: FnMut(A::AuthSig) -> Result<B::AuthSig, E>,
+    I: FnMut(A) -> Result<B, E>,
+{
+    type Error = E;
+
+    fn try_map_spend_proof(&mut self, p: A::SpendProof) -> Result<B::SpendProof, Self::Error> {
+        self.0(p)
+    }
+
+    fn try_map_output_proof(&mut self, p: A::OutputProof) -> Result<B::OutputProof, Self::Error> {
+        self.1(p)
+    }
+
+    fn try_map_auth_sig(&mut self, s: A::AuthSig) -> Result<B::AuthSig, Self::Error> {
+        self.2(s)
+    }
+
+    fn try_map_authorization(&mut self, a: A) -> Result<B, Self::Error> {
+        self.3(a)
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct Bundle<A: Authorization> {
     shielded_spends: Vec<SpendDescription<A>>,
@@ -160,7 +230,8 @@ impl<A: Authorization> Bundle<A> {
         &self.authorization
     }
 
-    pub fn map_authorization<B: Authorization, F: MapAuth<A, B>>(self, f: F) -> Bundle<B> {
+    /// Transitions this bundle from one authorization state to another.
+    pub fn map_authorization<B: Authorization, F: MapAuth<A, B>>(self, mut f: F) -> Bundle<B> {
         Bundle {
             shielded_spends: self
                 .shielded_spends
@@ -190,6 +261,45 @@ impl<A: Authorization> Bundle<A> {
             authorization: f.map_authorization(self.authorization),
         }
     }
+
+    /// Transitions this bundle from one authorization state to another.
+    pub fn try_map_authorization<B: Authorization, F: TryMapAuth<A, B>>(
+        self,
+        mut f: F,
+    ) -> Result<Bundle<B>, F::Error> {
+        Ok(Bundle {
+            shielded_spends: self
+                .shielded_spends
+                .into_iter()
+                .map(|d| {
+                    Ok(SpendDescription {
+                        cv: d.cv,
+                        anchor: d.anchor,
+                        nullifier: d.nullifier,
+                        rk: d.rk,
+                        zkproof: f.try_map_spend_proof(d.zkproof)?,
+                        spend_auth_sig: f.try_map_auth_sig(d.spend_auth_sig)?,
+                    })
+                })
+                .collect::<Result<_, _>>()?,
+            shielded_outputs: self
+                .shielded_outputs
+                .into_iter()
+                .map(|o| {
+                    Ok(OutputDescription {
+                        cv: o.cv,
+                        cmu: o.cmu,
+                        ephemeral_key: o.ephemeral_key,
+                        enc_ciphertext: o.enc_ciphertext,
+                        out_ciphertext: o.out_ciphertext,
+                        zkproof: f.try_map_output_proof(o.zkproof)?,
+                    })
+                })
+                .collect::<Result<_, _>>()?,
+            value_balance: self.value_balance,
+            authorization: f.try_map_authorization(self.authorization)?,
+        })
+    }
 }
 
 impl DynamicUsage for Bundle<Authorized> {