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Tier 2: - request_signature decomposed into named gates (latch, freshness, intent, policy, signer, firewall) - ledger: O(1) tail-read appends under a dedicated lock file (survives rotation rename); hash-chained segment rotation at policy ledger.rotate_at; verify-ledger walks all segments to genesis; archive tampering detected (tested) - docs/threat-model.md (attacker matrix 1-9, proven-vs-trusted, design invariants) + docs/runbook-latch.md (diagnose-first recovery) - lecture 10: executable corrupt-a-member exercise (capsule pin catches one appended byte), honest note on what the pin does NOT stop Lightweight policy engine (POLICY_DENIED wired): - policy.json: per-request/per-day amount ceilings, counterparty allow/deny lists, per-identity overrides; rules make their intent fields mandatory; daily sums from the ledger - Agent UX: - signed refusal receipts travel inside MCP errors (receipt + receipt_path in structuredContent) - airgap over MCP: request_signature signer=airgap + request_id, new airgap_pending tool; park -> list -> device answers -> complete (tested end-to-end) - all 8 tools carry readOnly/destructive annotations - sliding-window rate limiter per tool class (custody/verify/liveness); RATE_LIMITED refusal code; surface control, not ledgered warden-treasury LIVE: - treasury.py: stdlib base58, compact-u16, legacy+v0 wire parsing; every required signature quorum-verified over exact message bytes; completeness gap named in every verdict; RPC fetch uses response as bytes only - - live-quorum test: synthetic Solana tx signed with wallet key -> authentic via 4 proven forks; flipped byte -> not authentic 100 tests green (was 85). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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3.9 KiB
warden threat model
Who can attack the wallet, what each attacker can and cannot achieve, and which control stops them. "Proven" below means certificate-covered by the Lean corpus attested in the transparency log; everything else is named trusted base. The honest summary first: warden's strongest guarantees are about deciding what to believe (inbound) and catching its own signer lying (firewall); an attacker who fully owns the host owns the wallet.
Attacker matrix
| # | attacker controls | can achieve | cannot achieve | stopped / bounded by |
|---|---|---|---|---|
| 1 | the network path | delay, reorder, withhold traffic | forge an accepted authorization | quorum verification (proven); freshness policy bounds staleness |
| 2 | the RPC provider (treasury) | withhold transactions (completeness) | fabricate a transaction the wallet believes | quorum re-verification of every signature (proven); verdict notes the completeness gap explicitly |
| 3 | a counterparty agent | spam requests; submit garbage | drain funds; grind the ledger unboundedly | MCP rate limiter (surface control); intent binding; spending policy (POLICY_DENIED); refusals cheap, custody calls scarce |
| 4 | ONE quorum member binary on disk (swap/corrupt) | cause divergence | pass a forged signature (needs all four) | capsule hash-pin catches swap at assembly; unexplained divergence latches custody |
| 5 | the signing key (exfiltrated) | sign arbitrary payloads AS this wallet elsewhere | make THIS wallet release out-of-policy signatures | policy + intent gates still bind the wallet's own releases; key custody itself is trusted base — use the airgap profile when this attacker is in scope |
| 6 | the airgap channel (tampered device response) | return a wrong signature | get it released | the firewall: verify-after-sign through the quorum; wrong signature is quarantined and latches |
| 7 | the wallet host (root) | everything: edit ledger, replace binaries AND capsule, read keys | escape detection by an OFF-HOST copy of the ledger head | out of scope for on-host controls — this is the warden-choir rationale (cross-witnessed heads) and the airgap rationale (key not on host) |
| 8 | the log operator (LTL) | attest falsely that proofs re-check | change verdicts (consumers re-derive from cones); rewrite history unnoticed (append-only, witnessed) | observation-not-verdict; STH pinning; witness mirror |
| 9 | the wallet operator (insider) | unlatch carelessly; loosen policy.json | do either invisibly | latch/unlatch and policy live in artifacts; unlatch requires a note recorded permanently in the hash-chained ledger |
What is proven vs. trusted, one line each
- Proven (Lean certificates, log-attested): the verify path of each of the four quorum members — field arithmetic through the full signature acceptance equation.
- Trusted base: the signing path (attested artifact, fenced by the firewall); SHA-512 (oracle); wire parsers in the forks (hypotheses) and the ~120-line Solana wire parser in treasury mode; the OS, filesystem, and Python runtime; compilers; key custody.
- Deliberately absent: reproducible builds, side-channel hardening (R5 frontier); ML-DSA (fail-closed — no proven implementation exists).
Design invariants the controls enforce
- Unanimity or nothing: no majority voting; any divergence fails closed. A lone honest member is sufficient to block.
- A signature that failed the firewall never leaves the process — quarantined bytes, latched custody.
- Nothing custody-relevant is un-ledgered; nothing in the ledger can be edited without breaking the chain (single-flight lock, fsync, rotation with chained segments).
- Refusals are receipts: machine-actionable, signed when the wallet still trusts its own boundary, deliberately unsigned when latched.
- Policy failures are named (
POLICY_DENIED), never silent, and policy rules make their inputs mandatory rather than waving through requests that omit them.