pczt: Add a Verifier role

This isn't a real role per se; it's instead a way for accessing the parsed protocol-specific bundles for individual access and verification.
zcash · Dec 13, 2024 · f97f6fa · f97f6fa
1 parent 205d4c9
commit f97f6fa
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Showing 10 changed files with 260 additions and 71 deletions.
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -190,5 +190,5 @@ debug = true
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(zcash_unstable, values("zfuture"))'] }
 
 [patch.crates-io]
-orchard = { git = "https://github.com/zcash/orchard.git", rev = "bcd08e1d23e70c42a338f3e3f79d6f4c0c219805" }
-sapling-crypto = { git = "https://github.com/zcash/sapling-crypto.git", rev = "29cff9683cdf2f0c522ff3224081dfb4fbc80248" }
+orchard = { git = "https://github.com/zcash/orchard.git", rev = "3d951b4201a63f3c07cba8b179dd9abde142cf33" }
+sapling-crypto = { git = "https://github.com/zcash/sapling-crypto.git", rev = "231f81911628499a8877be57e66e60c09e55bdea" }
diff --git a/pczt/src/roles.rs b/pczt/src/roles.rs
@@ -3,6 +3,8 @@ pub mod creator;
 #[cfg(feature = "io-finalizer")]
 pub mod io_finalizer;
 
+pub mod verifier;
+
 pub mod updater;
 
 #[cfg(feature = "prover")]

diff --git a/pczt/src/roles/signer/mod.rs b/pczt/src/roles/signer/mod.rs
@@ -140,37 +140,16 @@ impl Signer {
             .get_mut(index)
             .ok_or(Error::InvalidIndex)?;
 
-        // Check consistency of the input being signed.
-        let note_from_fields = spend
-            .recipient()
-            .zip(spend.value().as_ref())
-            .zip(spend.rseed().as_ref())
-            .map(|((recipient, value), rseed)| {
-                sapling::Note::from_parts(recipient, *value, *rseed)
-            });
-
-        if let Some(note) = note_from_fields {
-            let tx_spend = self
-                .tx_data
-                .sapling_bundle()
-                .expect("index checked above")
-                .shielded_spends()
-                .get(index)
-                .expect("index checked above");
-
-            let proof_generation_key = spend
-                .proof_generation_key()
-                .as_ref()
-                .ok_or(Error::MissingProofGenerationKey)?;
-
-            let nk = proof_generation_key.to_viewing_key().nk;
-
-            let merkle_path = spend.witness().as_ref().ok_or(Error::MissingWitness)?;
-
-            if &note.nf(&nk, merkle_path.position().into()) != tx_spend.nullifier() {
-                return Err(Error::InvalidNullifier);
-            }
+        // Check consistency of the input being signed if we have its note components.
+        match spend.verify_nullifier(None) {
+            Err(
+                sapling::pczt::VerifyError::MissingRecipient
+                | sapling::pczt::VerifyError::MissingValue
+                | sapling::pczt::VerifyError::MissingRandomSeed,
+            ) => Ok(()),
+            r => r,
         }
+        .map_err(Error::SaplingVerify)?;
 
         spend
             .sign(self.shielded_sighash, ask, OsRng)
@@ -201,39 +180,17 @@ impl Signer {
             .get_mut(index)
             .ok_or(Error::InvalidIndex)?;
 
-        // Check consistency of the input being signed.
-        let note_from_fields = action
-            .spend()
-            .recipient()
-            .zip(action.spend().value().as_ref())
-            .zip(action.spend().rho().as_ref())
-            .zip(action.spend().rseed().as_ref())
-            .map(|(((recipient, value), rho), rseed)| {
-                orchard::Note::from_parts(recipient, *value, *rho, *rseed)
-                    .into_option()
-                    .ok_or(Error::InvalidNote)
-            })
-            .transpose()?;
-
-        if let Some(note) = note_from_fields {
-            let tx_action = self
-                .tx_data
-                .orchard_bundle()
-                .expect("index checked above")
-                .actions()
-                .get(index)
-                .expect("index checked above");
-
-            let fvk = action
-                .spend()
-                .fvk()
-                .as_ref()
-                .ok_or(Error::MissingFullViewingKey)?;
-
-            if &note.nullifier(fvk) != tx_action.nullifier() {
-                return Err(Error::InvalidNullifier);
-            }
+        // Check consistency of the input being signed if we have its note components.
+        match action.spend().verify_nullifier(None) {
+            Err(
+                orchard::pczt::VerifyError::MissingRecipient
+                | orchard::pczt::VerifyError::MissingValue
+                | orchard::pczt::VerifyError::MissingRho
+                | orchard::pczt::VerifyError::MissingRandomSeed,
+            ) => Ok(()),
+            r => r,
         }
+        .map_err(Error::OrchardVerify)?;
 
         action
             .sign(self.shielded_sighash, ask, OsRng)
@@ -317,17 +274,14 @@ pub enum Error {
     Global(GlobalError),
     IncompatibleLockTimes,
     InvalidIndex,
-    InvalidNote,
-    InvalidNullifier,
-    MissingFullViewingKey,
-    MissingProofGenerationKey,
-    MissingWitness,
     OrchardExtract(orchard::pczt::TxExtractorError),
     OrchardParse(orchard::pczt::ParseError),
     OrchardSign(orchard::pczt::SignerError),
+    OrchardVerify(orchard::pczt::VerifyError),
     SaplingExtract(sapling::pczt::TxExtractorError),
     SaplingParse(sapling::pczt::ParseError),
     SaplingSign(sapling::pczt::SignerError),
+    SaplingVerify(sapling::pczt::VerifyError),
     TransparentExtract(transparent::pczt::TxExtractorError),
     TransparentParse(transparent::pczt::ParseError),
     TransparentSign(transparent::pczt::SignerError),

diff --git a/pczt/src/roles/verifier/mod.rs b/pczt/src/roles/verifier/mod.rs
@@ -0,0 +1,32 @@
+use crate::Pczt;
+
+#[cfg(feature = "orchard")]
+mod orchard;
+#[cfg(feature = "orchard")]
+pub use orchard::OrchardError;
+
+#[cfg(feature = "sapling")]
+mod sapling;
+#[cfg(feature = "sapling")]
+pub use sapling::SaplingError;
+
+#[cfg(feature = "transparent")]
+mod transparent;
+#[cfg(feature = "transparent")]
+pub use transparent::TransparentError;
+
+pub struct Verifier {
+    pczt: Pczt,
+}
+
+impl Verifier {
+    /// Instantiates the Verifier role with the given PCZT.
+    pub fn new(pczt: Pczt) -> Self {
+        Self { pczt }
+    }
+
+    /// Finishes the Verifier role, returning the updated PCZT.
+    pub fn finish(self) -> Pczt {
+        self.pczt
+    }
+}
diff --git a/pczt/src/roles/verifier/orchard.rs b/pczt/src/roles/verifier/orchard.rs
@@ -0,0 +1,43 @@
+use crate::Pczt;
+
+impl super::Verifier {
+    /// Parses the Orchard bundle and then verifies it in the given closure.
+    pub fn with_orchard<E, F>(self, f: F) -> Result<Self, OrchardError<E>>
+    where
+        F: FnOnce(&orchard::pczt::Bundle) -> Result<(), OrchardError<E>>,
+    {
+        let Pczt {
+            global,
+            transparent,
+            sapling,
+            orchard,
+        } = self.pczt;
+
+        let bundle = orchard.into_parsed().map_err(OrchardError::Parse)?;
+
+        f(&bundle)?;
+
+        Ok(Self {
+            pczt: Pczt {
+                global,
+                transparent,
+                sapling,
+                orchard: crate::orchard::Bundle::serialize_from(bundle),
+            },
+        })
+    }
+}
+
+/// Errors that can occur while verifying the Orchard bundle of a PCZT.
+#[derive(Debug)]
+pub enum OrchardError<E> {
+    Parse(orchard::pczt::ParseError),
+    Verify(orchard::pczt::VerifyError),
+    Custom(E),
+}
+
+impl<E> From<orchard::pczt::VerifyError> for OrchardError<E> {
+    fn from(e: orchard::pczt::VerifyError) -> Self {
+        OrchardError::Verify(e)
+    }
+}
diff --git a/pczt/src/roles/verifier/sapling.rs b/pczt/src/roles/verifier/sapling.rs
@@ -0,0 +1,43 @@
+use crate::Pczt;
+
+impl super::Verifier {
+    /// Parses the Sapling bundle and then verifies it in the given closure.
+    pub fn with_sapling<E, F>(self, f: F) -> Result<Self, SaplingError<E>>
+    where
+        F: FnOnce(&sapling::pczt::Bundle) -> Result<(), SaplingError<E>>,
+    {
+        let Pczt {
+            global,
+            transparent,
+            sapling,
+            orchard,
+        } = self.pczt;
+
+        let bundle = sapling.into_parsed().map_err(SaplingError::Parser)?;
+
+        f(&bundle)?;
+
+        Ok(Self {
+            pczt: Pczt {
+                global,
+                transparent,
+                sapling: crate::sapling::Bundle::serialize_from(bundle),
+                orchard,
+            },
+        })
+    }
+}
+
+/// Errors that can occur while verifying the Sapling bundle of a PCZT.
+#[derive(Debug)]
+pub enum SaplingError<E> {
+    Parser(sapling::pczt::ParseError),
+    Verifier(sapling::pczt::VerifyError),
+    Custom(E),
+}
+
+impl<E> From<sapling::pczt::VerifyError> for SaplingError<E> {
+    fn from(e: sapling::pczt::VerifyError) -> Self {
+        SaplingError::Verifier(e)
+    }
+}
diff --git a/pczt/src/roles/verifier/transparent.rs b/pczt/src/roles/verifier/transparent.rs
@@ -0,0 +1,47 @@
+use zcash_primitives::transaction::components::transparent;
+
+use crate::Pczt;
+
+impl super::Verifier {
+    /// Parses the Transparent bundle and then verifies it in the given closure.
+    pub fn with_transparent<E, F>(self, f: F) -> Result<Self, TransparentError<E>>
+    where
+        F: FnOnce(&transparent::pczt::Bundle) -> Result<(), TransparentError<E>>,
+    {
+        let Pczt {
+            global,
+            transparent,
+            sapling,
+            orchard,
+        } = self.pczt;
+
+        let bundle = transparent
+            .into_parsed()
+            .map_err(TransparentError::Parser)?;
+
+        f(&bundle)?;
+
+        Ok(Self {
+            pczt: Pczt {
+                global,
+                transparent: crate::transparent::Bundle::serialize_from(bundle),
+                sapling,
+                orchard,
+            },
+        })
+    }
+}
+
+/// Errors that can occur while verifying the Transparent bundle of a PCZT.
+#[derive(Debug)]
+pub enum TransparentError<E> {
+    Parser(transparent::pczt::ParseError),
+    Verifier(transparent::pczt::VerifyError),
+    Custom(E),
+}
+
+impl<E> From<transparent::pczt::VerifyError> for TransparentError<E> {
+    fn from(e: transparent::pczt::VerifyError) -> Self {
+        TransparentError::Verifier(e)
+    }
+}
diff --git a/zcash_primitives/src/transaction/components/transparent/pczt.rs b/zcash_primitives/src/transaction/components/transparent/pczt.rs
@@ -14,6 +14,9 @@ use crate::{
 mod parse;
 pub use parse::ParseError;
 
+mod verify;
+pub use verify::VerifyError;
+
 mod updater;
 pub use updater::{InputUpdater, OutputUpdater, Updater, UpdaterError};
 

diff --git a/zcash_primitives/src/transaction/components/transparent/pczt/verify.rs b/zcash_primitives/src/transaction/components/transparent/pczt/verify.rs
@@ -0,0 +1,65 @@
+use ripemd::Ripemd160;
+use sha2::{Digest, Sha256};
+
+use crate::legacy::TransparentAddress;
+
+impl super::Input {
+    /// Verifies the consistency of this transparent input.
+    ///
+    /// If the `redeem_script` field is set, its validity will be checked.
+    pub fn verify(&self) -> Result<(), VerifyError> {
+        match self.script_pubkey().address() {
+            Some(TransparentAddress::PublicKeyHash(_)) => {
+                if self.redeem_script().is_some() {
+                    return Err(VerifyError::NotP2sh);
+                }
+            }
+            Some(TransparentAddress::ScriptHash(hash)) => {
+                if let Some(redeem_script) = self.redeem_script() {
+                    if hash[..] != Ripemd160::digest(Sha256::digest(&redeem_script.0))[..] {
+                        return Err(VerifyError::WrongRedeemScript);
+                    }
+                }
+            }
+            None => return Err(VerifyError::UnsupportedScriptPubkey),
+        }
+
+        Ok(())
+    }
+}
+
+impl super::Output {
+    /// Verifies the consistency of this transparent output.
+    ///
+    /// If the `redeem_script` field is set, its validity will be checked.
+    pub fn verify(&self) -> Result<(), VerifyError> {
+        match self.script_pubkey().address() {
+            Some(TransparentAddress::PublicKeyHash(_)) => {
+                if self.redeem_script().is_some() {
+                    return Err(VerifyError::NotP2sh);
+                }
+            }
+            Some(TransparentAddress::ScriptHash(hash)) => {
+                if let Some(redeem_script) = self.redeem_script() {
+                    if hash[..] != Ripemd160::digest(Sha256::digest(&redeem_script.0))[..] {
+                        return Err(VerifyError::WrongRedeemScript);
+                    }
+                }
+            }
+            None => return Err(VerifyError::UnsupportedScriptPubkey),
+        }
+
+        Ok(())
+    }
+}
+
+/// Errors that can occur while verifying a PCZT bundle.
+#[derive(Debug)]
+pub enum VerifyError {
+    /// A `redeem_script` can only be set on a P2SH coin.
+    NotP2sh,
+    /// The `script_pubkey` kind is unsupported.
+    UnsupportedScriptPubkey,
+    /// The provided `redeem_script` does not match the input's `script_pubkey`.
+    WrongRedeemScript,
+}