Secrets

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Overview

Fusion's secrets subsystem provides encrypted-at-rest secret storage with project scope (.fusion/fusion.db) and global scope (~/.fusion/fusion-central.db).

Implementation Status

Surface	Status	Follow-up	Source of truth
AES-256-GCM encryption primitives	Shipped	—	packages/core/src/secrets-crypto.ts
SecretsStore CRUD + revealSecret	Shipped	—	packages/core/src/secrets-store.ts
Per-secret access policy + global fallback resolver	Shipped	—	packages/core/src/secret-access-policy.ts
MasterKeyManager (keychain primary, file fallback)	Shipped	—	packages/core/src/master-key.ts
fn_secret_get pi-extension tool (auto/prompt/deny + missing-key)	Shipped	—	packages/cli/src/extension.ts
secret:read / secret:approval-requested / secret:approval-denied audit events	Shipped	—	packages/cli/src/extension.ts (emitSecretAudit)
Approval API integration for prompt policy (ApprovalRequestStore + POST /api/approvals/:id/decision)	Shipped	—	packages/cli/src/extension.ts
secrets-sync.ts wrap/unwrap core (scrypt → AES-256-GCM, version 1, typed errors)	Shipped	—	packages/core/src/secrets-sync.ts
Dashboard SecretsView CRUD UI	Shipped	—	packages/dashboard/app/components/SecretsView.tsx
secretsEnv.* settings + worktree .env materialization + fingerprint cleanup	Shipped	—	packages/core/src/types.ts, packages/engine/src/secrets-env-writer.ts
secretsSyncPassphraseConfigured global read-only probe + reserved secret storage (__sync_passphrase__)	Shipped	—	packages/core/src/types.ts, packages/core/src/secrets-sync-passphrase.ts
Cross-node sync REST endpoints (/api/nodes/:id/secrets/{push,pull}, /api/secrets/sync-receive, /api/secrets/sync-export)	Shipped	—	packages/dashboard/src/routes/register-secrets-sync-routes.ts, packages/dashboard/src/routes/register-secrets-sync-inbound-routes.ts
Audit-event registration on FilesystemMutationType for secret:env-* and secret:sync-*	Shipped	—	packages/engine/src/run-audit.ts
Master-key rotation UX	Pending	—	n/a
Per-secret TTL / rotation, KMS/Vault backends, per-node asymmetric sync	Out of scope	—	n/a

Current shipped behavior in this branch includes:

• AES-256-GCM encryption primitives (packages/core/src/secrets-crypto.ts)
• CRUD + reveal APIs via SecretsStore (packages/core/src/secrets-store.ts)
• Per-secret access policy metadata (auto / prompt / deny)
• Schema-backed read metadata (last_read_at, last_read_by)

Threat-model baseline:

• Secret plaintext is not stored in SQLite.
• Ciphertext + nonce are persisted; plaintext exists only in process memory during create/reveal.
• Secret values must never be logged.
• MCP server settings store only secret references for sensitive env/header/token fields; imports surface plaintext as secret-creation descriptors instead of persisting it in settings.
• MCP server secret references are materialized only at session/probe creation time for MCP-capable AI lanes and POST /api/mcp/validate; responses and structured logs include status/count metadata only, never resolved env/header values.

See also: Storage, Multi-project, Architecture, Settings reference, and MCP for MCP-specific secret-reference workflows.

Architecture

Fusion stores secrets in two SQLite tables:

• Project scope: secrets in .fusion/fusion.db
• Global scope: secrets_global in ~/.fusion/fusion-central.db

Both tables share the same column contract:

Column	Type	Notes
id	TEXT	Primary key UUID.
key	TEXT	Unique secret key (idxSecretsKey / idxSecretsGlobalKey).
value_ciphertext	BLOB	AES-GCM ciphertext payload (includes auth tag).
nonce	BLOB	Per-row random nonce.
description	TEXT	Optional metadata.
access_policy	TEXT	CHECK constrained to auto, prompt, deny.
env_exportable	INTEGER	0/1 flag for env-materialization intent metadata.
env_export_key	TEXT	Optional env variable key metadata.
created_at	TEXT	ISO timestamp.
updated_at	TEXT	ISO timestamp.
last_read_at	TEXT	Last reveal timestamp.
last_read_by	TEXT	Agent/user identifier recorded on reveal.

For broader database inventory, see docs/storage.md.

Encryption

Secret crypto uses AES-256-GCM with:

• 32-byte master key
• 12-byte random nonce per encrypt operation
• 16-byte auth tag appended to ciphertext

Implementation reference: packages/core/src/secrets-crypto.ts.

Master Key Resolution

The current implementation exposes a MasterKeyProvider abstraction consumed by createSecretCipher / SecretsStore.

• Required contract: async provider that returns a 32-byte key.
• Validation failures return non-sensitive SecretCryptoError codes.

Runtime keychain/filesystem resolution is shipped via MasterKeyManager (packages/core/src/master-key.ts) with keychain-primary lookup and ~/.fusion/master.key fallback (mode 0600); rotation UX remains follow-up work.

Access Policies

Per-secret policy values are:

• auto
• prompt
• deny

Resolution helper (resolveSecretAccessPolicy) uses:

1. Row-level secret policy (if set)
2. Global settings default secretsAccessPolicy (if set)
3. Fallback: prompt

Implementation references:

• packages/core/src/secret-access-policy.ts
• packages/core/src/types.ts (GlobalSettings.secretsAccessPolicy)

Approval integration is active through fn_secret_get policy handling (packages/cli/src/extension.ts:1581-1611) and approvals lifecycle APIs.

Dashboard CRUD

Dashboard secrets CRUD is shipped via SecretsView (packages/dashboard/app/components/SecretsView.tsx), backed by the existing secrets API/store surfaces.

Agent Access (fn_secret_get)

fn_secret_get is shipped in packages/cli/src/extension.ts:1542-1629.

Tool contract:

• Params: key (required), scope?: "project" | "global".
• Resolution: when scope is omitted, lookup is project → global; when provided, only that scope is queried. Missing key returns { error: "not-found" }.
• Policy outcomes:
  • auto → reveals and returns plaintext value (secret:read audit at extension.ts:1615).
  • prompt → creates ApprovalRequestStore request (secret-read:{scope}:{key}:{agentId} dedupe key) and returns { outcome: "pending_approval", approvalRequestId } (extension.ts:1607-1611).
  • deny → immediate refusal and secret:approval-denied audit (extension.ts:1581-1583).

.env Auto-write into Worktrees

Fusion can materialize env-exportable secrets into each acquired task worktree when project settings enable it (secretsEnv.enabled=true).

• Supported settings: enabled, filename (default .env, validated as local filename only), overwritePolicy (skip/merge/replace), keyPrefix, requireGitignored (default true).
• Safety guard: when requireGitignored is enabled, Fusion runs git check-ignore -- <filename> and refuses writes unless the file is ignored.
• Write contract: managed content is canonicalized and written atomically with mode 0o600; audit metadata includes keys and counts, never values.
• Fingerprint sidecar: successful writes persist .fusion-secrets-env.fingerprint containing <sha256>\n<filename>\n (mode 0o600) so teardown can verify file integrity before deletion.
• Teardown cleanup: when a worktree is removed, Fusion deletes the managed env file only when the on-disk fingerprint still matches; edited files are preserved and only the sidecar is removed.

Settings shape is split by scope: project-level secrets settings include ProjectSettings.secretsEnv and MCP secret references in ProjectSettings.mcpServers, while cross-node sync passphrase state is stored only as the reserved __sync_passphrase__ row in secrets_global and exposed read-only through GlobalSettings.secretsSyncPassphraseConfigured (packages/core/src/types.ts). Settings never carry plaintext passphrases or MCP credentials; MCP env/header/token fields use { secretRef, scope } and materialize through SecretsStore.revealSecret(...) only at the runtime use seam.

Test locations

The settings contract (SecretsEnvSettings shape, defaults, project round-trip) is covered in @fusion/core:

• packages/core/src/__tests__/secrets-env.test.ts — type contract + defaults
• packages/core/src/__tests__/store-settings.test.ts — secretsEnv project round-trip
• packages/core/src/__tests__/store-settings-sync-passphrase-probe.test.ts — read-only secretsSyncPassphraseConfigured derivation + write-strip behavior

The materialization implementation lives in @fusion/engine and is covered there:

• packages/engine/src/secrets-env-writer.ts — writeSecretsEnvFile / cleanupSecretsEnvFile
• packages/engine/src/__tests__/secrets-env-writer.test.ts — writer/cleanup unit coverage
• packages/engine/src/__tests__/worktree-acquisition-secrets-env.test.ts — acquisition-time write
• packages/engine/src/__tests__/worktree-pool-secrets-env-cleanup.test.ts — pool prune cleanup
• packages/engine/src/__tests__/reliability-interactions/secrets-env-materialization.test.ts — cross-layer backstop

New FN tasks that need to verify env materialization should target the engine-side files; the core-side test only guards the settings contract.

Cross-node Sync

Fusion now exposes four secrets sync endpoints:

• POST /api/nodes/:id/secrets/push — wraps local secrets into a passphrase-protected envelope and sends it to a remote node.
• POST /api/nodes/:id/secrets/pull — fetches a remote envelope from GET /api/secrets/sync-export and applies it locally.
• POST /api/secrets/sync-receive — inbound apply endpoint (Bearer apiKey required).
• GET /api/secrets/sync-export — inbound export endpoint (Bearer apiKey required).

Envelope format is WrappedSecretsBundle from packages/core/src/secrets-sync.ts:33-38: { version, ciphertext, salt, nonce, kdf, kdfParams } plus transport metadata (sourceNodeId, exportedAt). Wrapping uses scrypt (N=32768, r=8, p=1, keyLen=32, secrets-sync.ts:17-22) and AES-256-GCM with base64 ciphertext/salt/nonce (secrets-sync.ts:68-78).

Sync passphrase storage is local-only: reserved key __sync_passphrase__ in secrets_global with access_policy="deny" and env_exportable=false, encrypted under the local master key. The passphrase is never transmitted and never returned by HTTP endpoints.

Dashboard UX now exposes this through SecretsView → Cross-Node Sync Passphrase. The panel uses GET/PUT/DELETE /api/secrets/sync-passphrase; the GET route returns only { configured: boolean } (no plaintext readback), and the reserved __sync_passphrase__ row is filtered from the regular GET /api/secrets list.

Error mapping:

• SecretsSyncError codes (wrong-passphrase, version-mismatch, malformed) return HTTP 400 with { "error": <code> }.
• Missing passphrase returns HTTP 400 with { "error": "passphrase-not-configured" }.
• Bearer auth failures return HTTP 401.

Inbound auth contract is enforced in route code (packages/dashboard/src/routes/register-secrets-sync-inbound-routes.ts:99-114, :181-196): missing/invalid Bearer Authorization or mismatched local apiKey returns 401.

Audit payloads exclude plaintext values, passphrases, and envelope crypto material (ciphertext, salt, nonce).

Audit Events

Filesystem-domain secret audit taxonomy:

• secret:read
• secret:create
• secret:update
• secret:delete
• secret:approval-requested
• secret:approval-granted
• secret:approval-denied
• secret:sync-push
• secret:sync-pull
• secret:env-write
• secret:env-write-skipped
• secret:env-cleanup
• secret:env-cleanup-skipped

All listed events are enumerated in packages/engine/src/run-audit.ts:261-274 (union at run-audit.ts:325). Route/tool emitters include: secret:sync-push (packages/dashboard/src/routes/register-secrets-sync-routes.ts:92), secret:sync-pull (register-secrets-sync-routes.ts:180, register-secrets-sync-inbound-routes.ts:158-164), secret:read + approval events (packages/cli/src/extension.ts:1581-1615), env materialization/cleanup (packages/engine/src/secrets-env-writer.ts:99-217).

Track follow-up: FN-5031 (missing packages/core/src/__tests__/secrets-env.test.ts contract file).

Plaintext prohibition: audit payload metadata must never include plaintext, decrypted values, ciphertext, or nonce fields. Use assertNoSecretPlaintext(...) as the canonical enforcement helper before emitting secret audit events.

Operational Notes

• Backups: preserve both SQLite data and master-key material/provider source used by deployment.
• If master key material is lost, encrypted secret values become unrecoverable.
• Pending advanced capabilities:
  • Master-key rotation UX and key lifecycle tooling
  • TTL/rotation automation, env-set profiles, KMS/Vault backends, per-node asymmetric sync