fix: payment verification hardening -- cost units, close group, DoS prevention by grumbach · Pull Request #58 · WithAutonomi/ant-node

grumbach · 2026-04-02T09:18:39Z

Summary

Move ML-DSA-65 signature validation BEFORE on-chain RPC calls to prevent DoS via garbage proofs triggering expensive chain queries
Add CloseGroupChecker callback to PaymentVerifierConfig: when wired up, nodes verify they are in the close group before accepting merkle-paid data (currently None, ready for routing table integration)

Independent

This PR is self-contained. Uses only published evmlib 0.7.0 APIs already on main. No dependencies on other PRs.

Test plan

cfd passes
All builds, clippy, fmt, docs, security audit pass
Ubuntu tests pass. macOS/Windows test timeouts are pre-existing CI flakiness (runner resource limits)

Copilot

Pull request overview

Hardens merkle payment verification by validating candidate signatures earlier, adding optional close-group gating, and enforcing cost-unit integrity against on-chain commitments to prevent under/over-payment manipulation.

Changes:

Added close_group_checker callback option to PaymentVerifierConfig and threaded it through node/devnet/test configurations.
Moved ML-DSA-65 candidate signature validation before on-chain RPC calls to reduce DoS potential.
Added cost-unit verification by comparing signed metrics-derived commitments against on-chain packed commitments.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
`src/payment/verifier.rs`	Implements close-group callback, earlier signature validation, and cost-unit verification against on-chain commitments.
`src/node.rs`	Supplies `close_group_checker: None` when constructing `PaymentVerifierConfig`.
`src/devnet.rs`	Supplies `close_group_checker: None` for devnet nodes’ payment verifier config.
`src/storage/handler.rs`	Updates storage handler tests to include the new config field.
`tests/e2e/testnet.rs`	Updates e2e testnet node protocol construction to include the new config field.
`tests/e2e/data_types/chunk.rs`	Updates e2e chunk tests’ protocol construction to include the new config field.

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Copilot · 2026-04-02T09:22:31Z

src/payment/verifier.rs

@@ -76,6 +80,26 @@ pub struct PaymentVerifierConfig {
    /// Local node's rewards address.
    /// The verifier rejects payments that don't include this node as a recipient.
    pub local_rewards_address: RewardsAddress,
+    /// Optional close group checker for merkle payments.
+    ///
+    /// Given a data address, returns the rewards addresses of nodes in the local
+    /// close group view for that address. Used to verify the storing node is
+    /// actually responsible for the data. If `None`, the check is skipped.
+    pub close_group_checker: Option<CloseGroupChecker>,
+}


PaymentVerifierConfig used to derive Clone (and is re-exported as part of the public API). The new manual Debug impl removed the Clone derive, which is a breaking change for downstream crates and makes it harder to reuse configs. Consider re-adding #[derive(Clone)] (custom Debug can stay) or implementing Clone manually so existing callers continue to compile.

Copilot · 2026-04-02T09:22:32Z

src/payment/verifier.rs

+            // Verify cost units: ensure on-chain packed commitments match what
+            // the signed node metrics produce. This prevents clients from submitting
+            // inflated/deflated cost units to manipulate pricing.
+            let packed_commitments = merkle_payment_vault::get_merkle_payment_packed_commitments(
+                &self.config.evm.network,
+                pool_hash,
+                on_chain_info.merkle_payment_timestamp,
+            )
+            .await
+            .map_err(|e| {
+                Error::Payment(format!(
+                    "Failed to get packed commitments for cost unit verification: {e}"
+                ))
+            })?;
+
+            merkle_proof
+                .winner_pool
+                .verify_cost_units(&packed_commitments, &pool_hash)
+                .map_err(|e| {
+                    Error::Payment(format!(
+                        "Cost unit verification failed for pool {}: {e}",
+                        hex::encode(pool_hash)
+                    ))
+                })?;


get_merkle_payment_packed_commitments() is an additional on-chain RPC call that currently happens immediately after fetching get_merkle_payment_info(), before running other local validations that might fail (e.g., verify_merkle_proof, paid-node index checks). To minimize RPC amplification from invalid proofs, consider deferring the packed-commitments RPC until after the local proof validations succeed, and only then run verify_cost_units() + cache the pool.

Copilot · 2026-04-02T09:22:32Z

src/payment/verifier.rs

+        // Verify this node is in the close group for the data address.
+        // This prevents nodes from accepting data they're not responsible for.
+        if let Some(ref checker) = self.config.close_group_checker {
+            let close_group_addrs = checker(xorname);
+            if !close_group_addrs.contains(&self.config.local_rewards_address) {
+                return Err(Error::Payment(format!(
+                    "This node is not in the close group for address {}",
+                    hex::encode(xorname)
+                )));
+            }
+        }


The close-group membership check is performed after the on-chain queries and other verification steps. Since it only depends on xorname and local state, consider moving it earlier (right after the address match, or at least before any RPC calls) so nodes can reject out-of-responsibility PUTs without spending resources on chain lookups.

Copilot · 2026-04-02T09:22:32Z

src/payment/verifier.rs

+        // Verify this node is in the close group for the data address.
+        // This prevents nodes from accepting data they're not responsible for.
+        if let Some(ref checker) = self.config.close_group_checker {
+            let close_group_addrs = checker(xorname);
+            if !close_group_addrs.contains(&self.config.local_rewards_address) {
+                return Err(Error::Payment(format!(
+                    "This node is not in the close group for address {}",
+                    hex::encode(xorname)
+                )));
+            }
+        }


New behavior when close_group_checker is Some(_) is currently untested. Consider adding unit tests covering both acceptance (local rewards address is in returned close group) and rejection (not in close group), using the existing merkle-proof helpers + pre-populated pool_cache to avoid RPC calls.

- Move ML-DSA-65 signature validation BEFORE on-chain RPC calls to prevent DoS via garbage proofs triggering expensive chain queries - Add CloseGroupChecker callback to PaymentVerifierConfig: when wired up, nodes verify they are in the close group before accepting merkle-paid data (currently None, ready for routing table integration)

mickvandijke · 2026-04-03T09:28:00Z

Partially replaced by #61

The close group check will be part of a follow up PR.

Copilot AI review requested due to automatic review settings April 2, 2026 09:18

grumbach mentioned this pull request Apr 2, 2026

fix: upload reliability hardening -- retry, fault tolerance, spill cleanup WithAutonomi/ant-client#26

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Copilot started reviewing on behalf of grumbach April 2, 2026 09:19 View session

Copilot AI reviewed Apr 2, 2026

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grumbach force-pushed the fix/payment-upload-hardening branch from 03d94db to 0098f72 Compare April 3, 2026 02:50

mickvandijke mentioned this pull request Apr 3, 2026

fix: validate ML-DSA-65 signatures before on-chain RPC queries #61

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mickvandijke closed this Apr 3, 2026

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fix: payment verification hardening -- cost units, close group, DoS prevention#58

fix: payment verification hardening -- cost units, close group, DoS prevention#58
grumbach wants to merge 1 commit intomainfrom
fix/payment-upload-hardening

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grumbach commented Apr 2, 2026 •

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