fix(security): write job sidecar files with 0600 mode (#3753)#3809
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Async job sidecar files (jobs/result-<jobId>.json) were written with the default umask. Defense-in-depth (#3753): the payload may carry job-result data, so restrict to the owner in case NEXUS_DATA_DIR is ever shared across users. Not exploitable today (per-user stdio MCP, randomUUID jobIds) — pure hardening. - Extract persistJobRecord(path, record) (DRY over the 4 writers: pending/complete/ failed/cancelled) — writeFileSync with mode 0o600 + chmodSync after, so the mode holds even when a terminal status overwrites a pre-existing default-umask pending file (the writeFileSync mode option only applies on create). - 4 new tests assert 0600 on each terminal write, on pending-create, and the pending->complete overwrite path. 11 + 81 jobs tests pass; typecheck + lint clean. Closes #3753. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Closes #3753.
What
Async job sidecar files (
<NEXUS_DATA_DIR>/jobs/result-<jobId>.json) were written with the default umask. Defense-in-depth (post-session security audit finding): the payload may carry job-result data, so restrict to the owner ifNEXUS_DATA_DIRis ever shared across users. Not exploitable today (per-user stdio MCP, randomUUID jobIds, sha256 idempotency filenames) — pure hardening.How
persistJobRecord(path, record)— DRY over the four writers (writeJobPending/Complete/Failed/Cancelled, previously four identicalwriteFileSynccalls). It writes with{ mode: 0o600 }andchmodSync(path, 0o600)after — thechmodguarantees the mode even when a terminal status overwrites a pre-existing pending file (thewriteFileSyncmode option only applies on file create, not overwrite).Tests (TDD red→green)
4 new tests: 0600 on each terminal write (complete/failed/cancelled), on
writeJobPendingcreate, and on the pending→complete overwrite path (the case thechmodcovers). 11 store tests + 81 jobs-suite tests pass; typecheck + lint clean.🤖 Generated with Claude Code