Add tamper-evident integrity to spend-cap state#22
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The cap-state spend log was plain JSONL with no integrity, and load silently skipped malformed lines. The same OS user could therefore erase or rewrite spend history to bypass caps, and a garbage line that overwrote a real spend went unnoticed. Add a per-record chained HMAC-SHA256 (UseCapStateFileWithHMAC), keyed off the wallet identity via HKDF (info=pilot-cap-state-v1). Load now fails closed: a malformed line, an HMAC mismatch, or a signed-chain mixed with an unauthenticated record refuses to load rather than under-counting. A wholly-legacy file is migrated once to an authenticated chain; the legacy unauthenticated format stays readable via UseCapStateFile and still fails closed on malformed lines. Tests: tampered record detected, malformed line not silently dropped, HMAC round-trip survives restart, legacy migration then tamper-evident.
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Problem
The cap-state spend log (
cap-state.jsonl) was plain JSONL with no integrity, andloadSpendRecordssilently skipped malformed lines. The same OS user could therefore tamper with or erase spend history to bypass caps, and a garbage line overwriting a real spend went unnoticed (under-counting → cap loses force).Fix
info=pilot-cap-state-v1), exposed asUseCapStateFileWithHMAC.cmd/walletderives the key from theLocalSignerand uses the authenticated path by default.UseCapStateFilepath stays for unauthenticated files but also stops silently skipping malformed lines.The HKDF derivation matches pilotctl's reader (
appstore caps) so the daemon reads what the wallet writes.Tests
TestCapStateTamperedRecordDetected— altered amount with stale HMAC, and a plain record spliced into a signed chain, both caught.TestCapStateMalformedLineNotSilentlyDropped— garbage line errors (with and without a key) instead of being dropped.TestCapStateHMACRoundTrip— authenticated chain survives restart and the cap still holds.TestCapStateLegacyMigration— legacy file migrated, then tamper-evident.Validation
GOWORK=off go build/vet ./...clean;go test -race ./...green.