[lwshang]

Summary

A subnet can sign a certificate that verifies correctly but has an unexpected shape inside. Several lookups in ic-agent assumed the shape and would panic. They now return an AgentError:

Location	Before	After
lookup_incomplete_subnet	Principal::from_slice panics on a /subnet/<id>/node/<label> longer than 29 bytes	try_from_slice → AgentError::PrincipalError
lookup_canister_ranges	shard[0] panics when /canister_ranges/<id> is a bare leaf	shard paths must be exactly one label, otherwise CertificateVerificationFailed
lookup_api_boundary_nodes	path[0] panics when /api_boundary_nodes is a bare leaf	CertificateVerificationFailed
fetch_subnet_by_canister	Principal::from_slice(&delegation.subnet_id) panics on a blob longer than 29 bytes	try_from_slice → AgentError::PrincipalError

Affected public APIs: Agent::fetch_subnet_by_id, Agent::fetch_subnet_by_canister (and therefore get_subnet_by_canister), Agent::fetch_api_boundary_nodes_by_{canister,subnet}_id.

Only a subnet that signs malformed state can trigger these. That matters for cloud engines, which are not trusted the way regular subnets are. The delegation subnet_id case is NNS-signed, so it isn't reachable in practice; this change just makes it fail gracefully. A core protocol teammate reported these issues.

check_delegation already handled the shard-path case safely; this change makes the other lookups consistent with it.

Release

The second commit prepares 0.49.3. It bumps all workspace crates and Cargo.lock, and cuts the Unreleased changelog section, which also contains #743.

CI fix

The third commit bumps async-trait from 0.1.89 to 0.1.92 in Cargo.lock. Rust 1.99's clippy flags double_must_use on code generated by #[async_trait], which broke lint for any branch based on main; the problem was already there before this PR. The new version pulls in syn 3, and both crates need Rust 1.71 or newer, so the MSRV (1.88) is unaffected. I checked this with cargo +1.88.0 check --workspace.

Testing

• New unit tests in response_authentication.rs build malformed trees for the first three cases. Each test panics on main and passes on this branch.
• cargo test -p ic-agent --lib: 61 passed.
• The delegation.subnet_id case has no test, because building it would require a delegation that passes verification.

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

The targeted guards preserve valid-data behavior, regression tests cover the reported malformed-tree cases, and no blocking issues remain.

No open issues 🎉

What changed in this PR

This PR hardens ic-agent against malformed certified data by returning errors instead of panicking, and prepares release 0.49.3.

Changes:

• Adds fallible principal parsing and tree-path validation, with three malformed-tree regression tests.
• Updates workspace versions and release notes, including the earlier root-attested subnet-routing fix.
• Updates the locked async-trait dependency and adds syn 3 to address the reported Clippy failure.

File	Description
ic-agent/​src/​agent/​response_authentication.rs	Validates malformed node IDs and tree paths; adds regression tests.
ic-agent/​src/​agent/​mod.rs	Returns an error for oversized delegation subnet IDs.
CHANGELOG.md	Documents the fixes in release 0.49.3.
Cargo.toml	Bumps workspace and internal dependency versions to 0.49.3.
Cargo.lock	Records release versions and the procedural-macro dependency update.

_{Review effort: Balanced}

[zeropath-ai]

✅ No security or compliance issues detected. Reviewed everything up to 22a26f3.

Security Overview

• 🔎 Scanned files: 5 changed file(s)
• 🔗 Scan Link: https://zeropath.com/app/repositories/a3a96bf1-e1e7-4946-9d69-cd1493c911f8?scanId=9fbe8ad6-bfc3-48c1-8fc4-6e0d9dfcfee7&codeScanTypes=PrScan&tab=issues&detectionTypes=traditional,businessLogic,customRule,IAC,SECRETS,CICD,EOL,uncategorized

Detected Code Changes

Change Type

Relevant files

Enhancement

► ic-agent/src/agent/mod.rs       Change subnet_id extraction to use Principal::try_from_slice ► ic-agent/src/agent/response_authentication.rs       Update node_id extraction to use Principal::try_from_slice ► ic-agent/src/agent/response_authentication.rs       Adjust canister ranges lookup path to shard handling ► ic-agent/src/agent/response_authentication.rs       Update canister_ranges_tree lookups to use shard.as_bytes ► ic-agent/src/agent/response_authentication.rs       Update api_boundary_nodes extraction to use first path label bytes ► ic-agent/src/agent/response_authentication.rs       Add tests for certificate/lookup validations in response authentication