/peer-scoring-correctness

name: "peer-scoring-correctness"
description: "L1 trigger - audits peer reputation and scoring logic for symmetry, farming resistance, and penalty coverage."

Injectable Skill: Peer Scoring Correctness

> **L1 trigger**: `P2P` flag AND (`score_peer`, `peer_score`, `reputation`, `misbehavior`, `ban_peer`, `peer_scoring` detected) > **Inject Into**: `depth-network-surface` > **Language**: Go and Rust > **Finding prefix**: `[PSC-N]`

1. Reward / Penalty Symmetry

Enumerate all score increments and all score decrements. For every reward path, identify the matching penalty path and ask whether a malicious peer can gain trust faster than it can lose it.

Tag: `[PEER-SCORE:SYMMETRY]`

**Required full-leg matrix**: Do not stop after the first scoring bug. Build a complete table of every score mutation and every peer-performance observation:

| Leg | Event / endpoint | Reward? | Penalty? | Error classes penalized | Can attacker farm? | |---|---|---|---|---|---| | block validation | valid / invalid block | | | | | | block pool / orphan handling | unknown parent, invalid data, timeout | | | | | | health check | HTTP 200, non-200, timeout, parse error | | | | | | data/chunk request | delivery success, delivery fail, no response | | | | | | gossip | valid message, invalid message, duplicate, re-gossip | | | | | | bootstrap / peer list | useful peer, bogus peer, stale address | | | | |

Every blank `Penalty?` for a harmful event is a candidate finding. Every blank `Can attacker farm?` for a reward event is incomplete analysis.

2. Penalty Coverage

Build a failure-mode table and verify every harmful action has a score impact:

| Failure mode | Penalized? | Immediate? | Resettable? | |---|---|---|---| | Invalid block / tx | | | | | Timeout / stall | | | | | Malformed gossip | | | | | Health-check failure | | | | | Excessive requests | | | | | Non-response / timeout | | | | | Non-200 HTTP response | | | | | Delivery failure after accepted request | | | | | Invalid block held in cache / orphan pool | | | | | Stale peer address update | | | |

Tag: `[PEER-SCORE:COVERAGE]`

3. Farming / Free-Riding

Check whether peers can cheaply farm score via ping loops, `get_data` style requests, acknowledgements without contribution, or reconnect-based resets. Quantify attacker cost versus defender work.

For each positive score path, identify the cost the peer actually pays. A peer must not gain score for:

• returning any HTTP 200 when the requested data was not delivered;
• responding to health checks without serving blocks/chunks;
• causing the victim to fetch data from the attacker while the attacker withholds

useful data;

• reconnecting to clear a negative history and immediately earning fresh rewards.

Tag: `[PEER-SCORE:FARMING]`

3b. Direction and Sign Sanity

For every `increase_score`, `decrease_score`, `reward`, `penalize`, or raw `score +=/-=` site, verify the sign matches the semantic event. Common miss: error branches log failure but do not call the penalty path, or non-200 responses are treated as success because transport completed.

Tag: `[PEER-SCORE:DIRECTION:{file}:{line}]`

4. Reset and Persistence Semantics

• Does disconnect/reconnect reset score?
• Is score keyed by peer ID, IP, ENR, or connection object?
• Can bans be bypassed by cheap identity rotation?
• Are penalties persisted across restart?

Tag: `[PEER-SCORE:RESET]`

5. Selection Stability

Trace where score affects sync-source selection, top-peer preference, or bandwidth allocation. A manipulable score that changes any of those choices is an enabler finding even if the scoring bug alone is not terminal.

Tag: `[PEER-SCORE:SELECTION]`

6. Output Requirement

Always include the full-leg matrix in the output, even when every row is SAFE. If a row is not applicable, write `N/A` and cite the file/line proving the protocol does not implement that leg. Missing rows are treated as incomplete peer-scoring coverage.