cl: ban zero valued outputs

goas/cl/ledger/src/bundle.rs

@@ -1,4 +1,4 @@
-use crate::error::Result;
+use crate::error::{Error, Result};
 
 pub struct ProvedBundle {
     pub bundle: cl::Bundle,
@@ -6,7 +6,7 @@ pub struct ProvedBundle {
 }
 
 impl ProvedBundle {
-    pub fn prove(bundle: &cl::Bundle, bundle_witness: &cl::BundleWitness) -> Self {
+    pub fn prove(bundle: &cl::Bundle, bundle_witness: &cl::BundleWitness) -> Result<Self> {
         // need to show that bundle is balanced.
         // i.e. the sum of ptx balances is 0
 
@@ -23,7 +23,7 @@ impl ProvedBundle {
         let opts = risc0_zkvm::ProverOpts::succinct();
         let prove_info = prover
             .prove_with_opts(env, nomos_cl_risc0_proofs::BUNDLE_ELF, &opts)
-            .unwrap();
+            .map_err(|_| Error::Risc0ProofFailed)?;
 
         println!(
             "STARK 'bundle' prover time: {:.2?}, total_cycles: {}",
@@ -33,10 +33,10 @@ impl ProvedBundle {
 
         let receipt = prove_info.receipt;
 
-        Self {
+        Ok(Self {
             bundle: bundle.clone(),
             risc0_receipt: receipt,
-        }
+        })
     }
 
     pub fn public(&self) -> Result<cl::Balance> {

goas/cl/ledger/src/error.rs

@@ -6,4 +6,6 @@ pub type Result<T> = core::result::Result<T, Error>;
 pub enum Error {
     #[error("risc0 failed to serde")]
     Risc0Serde(#[from] risc0_zkvm::serde::Error),
+    #[error("risc0 failed to prove execution of the zkvm")]
+    Risc0ProofFailed,
 }

goas/cl/ledger/src/input.rs

@@ -1,6 +1,6 @@
 use proof_statements::input::{InputPrivate, InputPublic};
 
-use crate::error::Result;
+use crate::error::{Error, Result};
 
 const MAX_NOTE_COMMS: usize = 2usize.pow(8);
 
@@ -11,7 +11,10 @@ pub struct ProvedInput {
 }
 
 impl ProvedInput {
-    pub fn prove(input: &cl::InputWitness, note_commitments: &[cl::NoteCommitment]) -> Self {
+    pub fn prove(
+        input: &cl::InputWitness,
+        note_commitments: &[cl::NoteCommitment],
+    ) -> Result<Self> {
         let output_cm = input.note_commitment();
 
         let cm_leaves = note_commitment_leaves(note_commitments);
@@ -42,7 +45,7 @@ impl ProvedInput {
         let opts = risc0_zkvm::ProverOpts::succinct();
         let prove_info = prover
             .prove_with_opts(env, nomos_cl_risc0_proofs::INPUT_ELF, &opts)
-            .unwrap();
+            .map_err(|_| Error::Risc0ProofFailed)?;
 
         println!(
             "STARK 'input' prover time: {:.2?}, total_cycles: {}",
@@ -52,13 +55,13 @@ impl ProvedInput {
         // extract the receipt.
         let receipt = prove_info.receipt;
 
-        Self {
+        Ok(Self {
             input: InputPublic {
                 cm_root: cl::merkle::root(cm_leaves),
                 input: input.commit(),
             },
             risc0_receipt: receipt,
-        }
+        })
     }
 
     pub fn public(&self) -> Result<InputPublic> {
@@ -103,7 +106,7 @@ mod test {
 
         let notes = vec![input.note_commitment()];
 
-        let mut proved_input = ProvedInput::prove(&input, &notes);
+        let mut proved_input = ProvedInput::prove(&input, &notes).unwrap();
 
         let expected_public_inputs = InputPublic {
             cm_root: cl::merkle::root(note_commitment_leaves(&notes)),

goas/cl/ledger/src/output.rs

@@ -1,4 +1,4 @@
-use crate::error::Result;
+use crate::error::{Error, Result};
 
 pub struct ProvedOutput {
     pub output: cl::Output,
@@ -6,7 +6,7 @@ pub struct ProvedOutput {
 }
 
 impl ProvedOutput {
-    pub fn prove(witness: &cl::OutputWitness) -> Self {
+    pub fn prove(witness: &cl::OutputWitness) -> Result<Self> {
         let env = risc0_zkvm::ExecutorEnv::builder()
             .write(&witness)
             .unwrap()
@@ -20,7 +20,7 @@ impl ProvedOutput {
         let opts = risc0_zkvm::ProverOpts::succinct();
         let prove_info = prover
             .prove_with_opts(env, nomos_cl_risc0_proofs::OUTPUT_ELF, &opts)
-            .unwrap();
+            .map_err(|_| Error::Risc0ProofFailed)?;
 
         println!(
             "STARK 'output' prover time: {:.2?}, total_cycles: {}",
@@ -30,10 +30,10 @@ impl ProvedOutput {
 
         let receipt = prove_info.receipt;
 
-        Self {
+        Ok(Self {
             output: witness.commit(),
             risc0_receipt: receipt,
-        }
+        })
     }
 
     pub fn public(&self) -> Result<cl::Output> {
@@ -70,7 +70,7 @@ mod test {
             nonce: cl::NullifierNonce::random(&mut rng),
         };
 
-        let mut proved_output = ProvedOutput::prove(&output);
+        let mut proved_output = ProvedOutput::prove(&output).unwrap();
 
         let expected_output_cm = output.commit();
 
@@ -100,4 +100,17 @@ mod test {
             assert!(!proved_output.verify());
         }
     }
+
+    #[test]
+    fn test_zero_output_is_rejected() {
+        let mut rng = thread_rng();
+
+        let output = cl::OutputWitness::random(
+            cl::NoteWitness::basic(0, "NMO"),
+            cl::NullifierSecret::random(&mut rng).commit(),
+            &mut rng,
+        );
+
+        assert!(ProvedOutput::prove(&output).is_err());
+    }
 }

goas/cl/ledger/src/partial_tx.rs

@@ -2,7 +2,9 @@ use std::collections::BTreeMap;
 
 use proof_statements::death_constraint::DeathConstraintPublic;
 
-use crate::{death_constraint::DeathProof, input::ProvedInput, output::ProvedOutput};
+use crate::{
+    death_constraint::DeathProof, error::Result, input::ProvedInput, output::ProvedOutput,
+};
 
 #[derive(Debug, Clone)]
 pub struct PartialTxInput {
@@ -29,18 +31,27 @@ impl ProvedPartialTx {
         ptx: &cl::PartialTxWitness,
         mut death_proofs: BTreeMap<cl::Nullifier, DeathProof>,
         note_commitments: &[cl::NoteCommitment],
-    ) -> ProvedPartialTx {
-        Self {
-            inputs: Vec::from_iter(ptx.inputs.iter().map(|i| {
-                PartialTxInput {
-                    input: ProvedInput::prove(i, note_commitments),
+    ) -> Result<ProvedPartialTx> {
+        let inputs = ptx
+            .inputs
+            .iter()
+            .map(|i| {
+                Ok(PartialTxInput {
+                    input: ProvedInput::prove(i, note_commitments)?,
                     death: death_proofs
                         .remove(&i.nullifier())
                         .expect("Input missing death proof"),
-                }
-            })),
-            outputs: Vec::from_iter(ptx.outputs.iter().map(ProvedOutput::prove)),
-        }
+                })
+            })
+            .collect::<Result<_>>()?;
+
+        let outputs = ptx
+            .outputs
+            .iter()
+            .map(ProvedOutput::prove)
+            .collect::<Result<_>>()?;
+
+        Ok(Self { inputs, outputs })
     }
 
     pub fn ptx(&self) -> cl::PartialTx {

goas/cl/ledger/tests/simple_transfer.rs

@@ -68,7 +68,7 @@ fn test_simple_transfer() {
 
     // assume we only have one note commitment on chain for now ...
     let note_commitments = vec![utxo.commit_note()];
-    let proved_ptx = ProvedPartialTx::prove(&ptx_witness, death_proofs, &note_commitments);
+    let proved_ptx = ProvedPartialTx::prove(&ptx_witness, death_proofs, &note_commitments).unwrap();
 
     assert!(proved_ptx.verify()); // It's a valid ptx.
 
@@ -80,6 +80,6 @@ fn test_simple_transfer() {
         balance_blinding: ptx_witness.balance_blinding(),
     };
 
-    let proved_bundle = ProvedBundle::prove(&bundle, &bundle_witness);
+    let proved_bundle = ProvedBundle::prove(&bundle, &bundle_witness).unwrap();
     assert!(proved_bundle.verify()); // The bundle is balanced.
 }

goas/cl/risc0_proofs/output/src/main.rs

@@ -7,6 +7,12 @@ use risc0_zkvm::guest::env;
 
 fn main() {
     let output: cl::OutputWitness = env::read();
+
+    // 0 does not contribute to balance, implications of this are unclear
+    // therefore out of an abundance of caution, we disallow these zero
+    // valued "dummy notes".
+    assert!(output.note.value > 0);
+
     let output_cm = output.commit();
     env::commit(&output_cm);
 }