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Yichen Jiang a90ccc4453 revert(sandbox): withdraw the credential-document read denial

The `readDenyPaths` policy field shipped in the previous commit broke Linux
confinement outright. bwrap has to create the `/dev/null` bind's mount point
inside a tree its own profile has already made read-only, so it refused the
entire confinement whenever the parent directory was absent — every host that
has not stored a credential yet, including a fresh install:

  bwrap: Can't mkdir parents for /home/runner/.dsh/.env: Read-only file system

which the executor correctly classifies as SANDBOX_UNAVAILABLE, so every
confined bash call failed closed. Landlock cannot subtract from its own `/`
read grant, so it reported `partial` enforcement on every confined call for a
file it never hid, with no way to switch the denial off (schemastery fills an
omitted array with `[]`, so empty and omitted were indistinguishable).

A protection that breaks confinement where it works and misreports it where it
does not is worse than a documented absence. Revert the field, both expressible
backends, the enforcement downgrade, and the policy default; state the residue
plainly in the credentials-local READMEs — file mode stops other OS users, not
the model — and keep the OS-keychain provider recorded as the real answer.

The narrower discipline stands: no surface hoists the credential document into
`process.env`, and the model is never handed a resolved path to it.

2026-07-30 17:09:42 +08:00

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dsh-sandbox-policy — the sandbox policy home (`ctx.sandboxPolicy`)

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The single owner of sandbox-policy resolution: the deployment's default SandboxMode and fallback root, plus each session's durable mode override and immutable workspace root. Every enforcing capability family receives one resolved mode-and-root policy per call.

Why a shared home

Two families enforce the same mode vocabulary: the sandboxed bash executor (@deepseek-ai/dsh-bash-sandbox) and the sandboxed filesystem provider (@deepseek-ai/dsh-fs-sandbox). If each resolved its own mode + workspaceRoot, the two could drift into a split world — bash confined to one root while fs fences another, exactly what the sandbox RFC warns against. Both tool layers resolve policy through ctx.sandboxPolicy, and both enforcing backends consume that complete per-call result. The cross-family fs sandbox RFC records the shared-policy decision.

Config

mode — the deployment default SandboxMode (read-only / workspace-write / danger-full-access), validated at load. Default read-only (fail-safe).
workspaceRoot — the fallback directory workspace-write may write under for agentless calls or sessions without a cwd. Default process.cwd(), resolved to its absolute filesystem identity either way. A normal agent call uses its session header's immutable cwd instead.

Surface

ctx.sandboxPolicy.resolve({ session?, mode? }) — resolves one complete per-call policy. An explicit approved mode outranks the session's last sandbox/mode event, which outranks defaultMode; the session's immutable cwd is canonicalized with filesystem semantics before becoming workspaceRoot, otherwise the configured fallback applies. Canonicalization precedes lexical normalization so symlink/.. agrees with process working-directory resolution.
ctx.sandboxPolicy.defaultMode / ctx.sandboxPolicy.workspaceRoot — the deployment default and fallback root used by resolve().
effectiveSandboxMode(events) — the pure fold of a session's sandbox/mode events (the last switch wins, or undefined), used inside resolve().
setSandboxMode(session, mode) — THE write path for a per-session override: appends exactly one sandbox/mode event. The switch IS its event; nothing mutates the mode out of band.
SANDBOX_MODES — every mode, for option advertisement and runtime validation.

The optional ./invariant companion rejects a forged durable sandbox/mode event whose value falls outside that closed vocabulary; Session and its companion own the surrounding storage and core execution-enclosure rules.

The per-session store

A runtime switch is one log-only sandbox/mode event on the session it applies to. effective = explicit grant ?? fold(events) ?? deployment default, so an override survives restart by replay and two sessions never see each other's state. Workspace identity does not need another event: the immutable SessionHeader.cwd recorded at creation is the root for every call in that session. The event is log-only (the approval/* precedent): the model learns the mode from the enforcing tools' denial markers, never from the event.

Model Experience

Indirectly, through dsh-tool-bash and dsh-tool-fs, which render the effective mode this service holds in their [sandbox: …] denial markers and escalation prompts; the sandbox/mode event itself never reaches the model.

KV Cache effect

No direct invalidation; the named consumers own any request-prefix changes, and the mode is deliberately absent from the prompt.

Known Limitations and Deferred Work

One primary workspace root per session — policy resolves SessionHeader.cwd; extra writable roots are not part of SandboxExecutionPolicy.
File-effect modes only — SandboxMode governs file effects; network and process policy are outside its vocabulary, so no knob here restricts them.

4.1 KiB Raw Blame History

dsh-sandbox-policy — the sandbox policy home (ctx.sandboxPolicy)