[dezren39]

Fixes #2121

tuple::decode recursed on every NESTED tag with no depth limit. The decoder is reached for peer-written iroh-docs entry keys (tag alpha/omega keys), so a crafted ~100 KB key with ~50k nested tags aborted the process with a stack overflow instead of returning an error.

Change (pkgs/id/crates/id-core/src/tuple.rs — the module moved here in the id-core crate split; the unbounded recursion was identical)

• Add named pub const MAX_TUPLE_NESTING_DEPTH: usize = 64, matching the peer-CBOR RECURSION_LIMIT = 64 in chain.rs.
• Thread the current depth through decode_one; a nested element beyond the cap returns an ordinary anyhow error before recursing further. Alpha/omega tag-key decoders get this automatically since they call tuple::decode.
• Document the cap and the existing encoder asymmetry: TupleEncoder stays infallible and can encode deeper than decode accepts — no breaking change to its public signature in this fix.

Tests (new, in-module)

• test_decode_at_nesting_limit_roundtrips — exactly 64 nested tuples decode and walk down to the innermost value.
• test_decode_one_over_nesting_limit_errors — 65 nested tuples return Err.
• test_decode_hostile_depth_errors_on_small_stack — 50k NESTED bytes decode on a 2 MiB-stack thread and return Err instead of aborting.

Existing tuple/tag tests run in CI on this PR (CI-first verification; no local build run — laptop load was >50 during this shift and local fleet builds are banned by policy in favour of Actions).

Queue: task 5100 (repo-health-code-pilot), lane F.

---

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-02T06:46:57.531168Z	a538f12	Manual request

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[dezren39]

🤖 Agent note · parked

• Agent: queue worker (repo-worker-code), lane F
• Session / ID: task 5100
• Found via: queue claim
• Task: PR id(tuple): cap nested tuple decode depth at 64 #4083 opened for issue id(tuple): decode recurses on NESTED with no depth limit — a crafted 100 KB tag key (50k nested tags) aborts the process with a stack overflow #2121 (commit a538f12, branch queue/5100-2121-tuple-decode-limit). Codex review completed with no findings. Parked because CI was still pending after the 5-minute poll window.
• Expectation: resume when PR id(tuple): cap nested tuple decode depth at 64 #4083 checks settle: merge if green, complete task 5100; fix forward on the same branch if red.
• Links: PR id(tuple): cap nested tuple decode depth at 64 #4083 id(tuple): cap nested tuple decode depth at 64 #4083

[dezren39]

@codex review — resuming task 5100; no Codex review on head a538f12 yet. Note: the broad basic-tier failures on this head are Magic Nix Cache throttling (HTTP 418 / ResourceExhausted in job logs), not the change; guard + native arm64 are SUCCESS.

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🎉

Reviewed commit: a538f128a2

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