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refactor(sandbox): derive the private temp dir; drop the acl-session record

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The durable sandbox/acl-session event carried a workspace binding that
always equals the session cwd and a random temp path that only needed
to be stable per session. Both are now derived: the temp subdirectory
is sha256(session id + workspace), created exclusively and removed on
provider dispose, so fork/resume semantics fall out of the derivation
and the record, its fold/provision/tamper validation, the immediate
flush kick, and the session-store dependency all disappear.
This commit is contained in:
Huanqi Cao
2026-08-10 00:54:55 +08:00
parent a29966b71f
commit 976020f2bb
12 changed files with 257 additions and 487 deletions
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.agents/notes/implemented/feature/2026-08-08-windows-acl-restricted-token-sandbox.md
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@@ -10,7 +10,7 @@ The [sandbox decision](2026-07-06-sandbox.md) leaves `PLATFORM_CHAINS.win32` emp
## Decision
Implement the rung directly on the raw ACL mechanism: duplicate the caller's token into a `WRITE_RESTRICTED` token (`CreateRestrictedToken` with `WRITE_RESTRICTED` + `DISABLE_MAX_PRIVILEGE` + `LUA_TOKEN`) whose restricting SIDs include a write SID (`S-1-4-x-y`); the write SID's Write ACEs on the workspace and temp roots are the entire write allowlist, because `WRITE_RESTRICTED` intersects write accesses only and reads keep the caller's full ambient access. The mechanism is the one huoyaoyuan/windows-acl-restrict-poc (`10e4dfb`) demonstrates; this port checks every API call and fails closed (the POC fail-opened on every ignored return value). The write SID is the PER-WORKSPACE identity, derived deterministically from the canonical workspace path (`workspaceWriteSid` — sha256 → `S-1-4-x-y`) and stored NOWHERE: the workspace-root ACE therefore materializes once per workspace per machine — the standing ACE is the cross-session reuse cache, and every later provision hits the exact-ACE skip (idempotent re-grant skips the eager full-tree re-propagation — no garbage collection) — instead of once per session, which is what the earlier per-session random SID paid a full tree propagation per session for. The seam still provisions one log-only `sandbox/acl-session` event per session (fork mints a fresh one; resume replays the same one) carrying the session's workspace binding and PRIVATE temp subdirectory — no SID, so the record's old SID-tamper surface does not exist; a fresh provision kicks an immediate persistence flush right after the append (no write-behind debounce), so the record is durable within the flush latency — a crash inside that window can strand the private temp directory unrecorded, the one documented self-healing gap. The seam materializes the workspace ACE STANDING (never revoked — the cache) and the temp ACE REVOCABLY (revoked on provider dispose, so an inheritable ACE never outlives its session's temp directory on the ambient temp root); the record is BOUND to its owning session id and validated at the fold (workspace/temp shape): a fork's copied parent record never provisions the child, and a tampered record fails loud instead of materializing grants. The token's restricting list is the keep-alive group plus the write SID only under workspace-write: read-only = [logon SID, Everyone] and workspace-write = [logon SID, Everyone, write SID]. The keep-alive invariants are logon SID + Everyone (early DLL init dies with 0xC0000142 and CNG crashes pwsh with 0xE0434352 without them). Read-only carries no write SID: a standing grant ACE from an earlier workspace-write period stays INERT (the pass-2 check grants only what the list carries, so read-only remains strictly zero-grant across a `/permission` downgrade or a crash-resumed session, while the standing ACE keeps the re-upgrade free). Authenticated Users is absent from BOTH lists — the WMI namespace security check fails (0x80041003), so CIM is unavailable in every confined mode, and the C:\-root tree-creation escape (standing `AU:(AD)` + `AU:(OI)(CI)(IO)(M)` ACEs) is closed in both; INTERACTIVE/LOCAL are likewise absent from both (the Public tree writes are denied — pinned by the runner's Public-probe regression). Workspace-write children see a PRIVATE per-session temp subdirectory (`<temp>\dsh-<16 random hex>` — unguessable, created exclusively, reparse points rejected — TMP/TEMP rewritten by the runner — bwrap `--tmpfs /tmp` semantics). The restricted token's DEFAULT DACL is extended with a full-access write-SID ACE (`SetTokenInformation(TokenDefaultDacl)`): new objects created without an explicit security descriptor (anonymous pipes — CreatePipe, sync objects) then carry a restricting-SID ACE and pass the write pass-2 check at creation; NAMED pipes are exempt — their default security descriptor is the kernel's PUBLIC template (owner/SYSTEM/Admins full, Everyone read-only), which the token cannot influence, so piped stdio capture stays denied for confined grandchildren (the POC-documented boundary, pinned by the runner suite). It ships as [`@deepseek-ai/dsh-sandbox-windows-acl`](../../../../packages/sandbox/sandbox-windows-acl/README.md) (backend plus the `./runner` argv-prefix entry), the `win32` chain rung of [`dsh-sandbox-local`](../../../../packages/sandbox/sandbox-local/README.md), and [`@deepseek-ai/dsh-pwsh-sandbox`](../../../../packages/bash/pwsh-sandbox/README.md) as the confining executor; the Windows platform layer re-enables the full permission surface (sandbox/sandbox-policy/permission/approval/fs-sandbox) over the confined pwsh stack.
Implement the rung directly on the raw ACL mechanism: duplicate the caller's token into a `WRITE_RESTRICTED` token (`CreateRestrictedToken` with `WRITE_RESTRICTED` + `DISABLE_MAX_PRIVILEGE` + `LUA_TOKEN`) whose restricting SIDs include a write SID (`S-1-4-x-y`); the write SID's Write ACEs on the workspace and temp roots are the entire write allowlist, because `WRITE_RESTRICTED` intersects write accesses only and reads keep the caller's full ambient access. The mechanism is the one huoyaoyuan/windows-acl-restrict-poc (`10e4dfb`) demonstrates; this port checks every API call and fails closed (the POC fail-opened on every ignored return value). The write SID is the PER-WORKSPACE identity, derived deterministically from the canonical workspace path (`workspaceWriteSid` — sha256 → `S-1-4-x-y`) and stored NOWHERE: the workspace-root ACE therefore materializes once per workspace per machine — the standing ACE is the cross-session reuse cache, and every later provision hits the exact-ACE skip (idempotent re-grant skips the eager full-tree re-propagation — no garbage collection) — instead of once per session, which is what the earlier per-session random SID paid a full tree propagation per session for. The seam derives the session's PRIVATE temp subdirectory from the session id + workspace (sha256, 16 hex — stored nowhere, so no tamper surface exists) and creates it exclusively; it is removed on provider dispose, and a crash leaves it as `%TEMP%` litter whose next resume fails loudly at the exclusive creation until temp hygiene reclaims it. The seam materializes the workspace ACE STANDING (never revoked — the cache) and the temp ACE REVOCABLY (revoked on provider dispose, so an inheritable ACE never outlives its session's temp directory on the ambient temp root). The token's restricting list is the keep-alive group plus the write SID only under workspace-write: read-only = [logon SID, Everyone] and workspace-write = [logon SID, Everyone, write SID]. The keep-alive invariants are logon SID + Everyone (early DLL init dies with 0xC0000142 and CNG crashes pwsh with 0xE0434352 without them). Read-only carries no write SID: a standing grant ACE from an earlier workspace-write period stays INERT (the pass-2 check grants only what the list carries, so read-only remains strictly zero-grant across a `/permission` downgrade or a crash-resumed session, while the standing ACE keeps the re-upgrade free). Authenticated Users is absent from BOTH lists — the WMI namespace security check fails (0x80041003), so CIM is unavailable in every confined mode, and the C:\-root tree-creation escape (standing `AU:(AD)` + `AU:(OI)(CI)(IO)(M)` ACEs) is closed in both; INTERACTIVE/LOCAL are likewise absent from both (the Public tree writes are denied — pinned by the runner's Public-probe regression). Workspace-write children see a PRIVATE per-session temp subdirectory (`<temp>\dsh-<16 hex>` derived from the session id + workspace — created exclusively, reparse points rejected, removed on provider dispose — TMP/TEMP rewritten by the runner — bwrap `--tmpfs /tmp` semantics). The restricted token's DEFAULT DACL is extended with a full-access write-SID ACE (`SetTokenInformation(TokenDefaultDacl)`): new objects created without an explicit security descriptor (anonymous pipes — CreatePipe, sync objects) then carry a restricting-SID ACE and pass the write pass-2 check at creation; NAMED pipes are exempt — their default security descriptor is the Win32 layer's user-mode default SD template (built by KernelBase — owner/SYSTEM/Admins full, Everyone/ANONYMOUS read-only), which the token cannot influence, so piped stdio capture stays denied for confined grandchildren (the POC-documented boundary, pinned by the runner suite). It ships as [`@deepseek-ai/dsh-sandbox-windows-acl`](../../../../packages/sandbox/sandbox-windows-acl/README.md) (backend plus the `./runner` argv-prefix entry), the `win32` chain rung of [`dsh-sandbox-local`](../../../../packages/sandbox/sandbox-local/README.md), and [`@deepseek-ai/dsh-pwsh-sandbox`](../../../../packages/bash/pwsh-sandbox/README.md) as the confining executor; the Windows platform layer re-enables the full permission surface (sandbox/sandbox-policy/permission/approval/fs-sandbox) over the confined pwsh stack.
## How the restriction works (why no new identity)
@@ -32,11 +32,11 @@ The [landstrip evaluation](../../rejected/feature/2026-07-26-evaluate-landstrip-
## Consequences
Bought: write-only confinement with no new OS floor (`CreateRestrictedToken` predates the mxc releases by two decades), reads/network/process visibility untouched exactly as the mode vocabulary requires, and fail-closed errors carrying the API name and the exact Win32 code. Cost: no read-side or network isolation; console isolation unavailable (hidden-console children die with `STATUS_DLL_INIT_FAILED`; children share the host console); standing ACE mutations on the granted roots (caller-owned directories; workspace ACEs stand forever by design — the reuse cache, invisible residue when a workspace is renamed — temp ACEs revoked by provider dispose, self-healing across restarts via the durable per-session record — whose immediate flush precedes the ACEs, within the flush latency); grant materialization is an EAGER full-tree propagation (`SetNamedSecurityInfoW` walks every descendant immediately — tens of seconds on large workspaces), paid once per workspace per machine by the per-workspace identity; CIM is unavailable in BOTH confined modes (AuthUsers dropped from both lists — the WMI namespace security check fails, and `Get-ComputerInfo` silently returns incomplete results) as the price of closing the C:\-root tree-creation escape in both; FAT-class (non-ACL) targets outside the granted roots remain writable under both modes (no security descriptors to intersect — a legacy residue treated as unsupported, warn-only, documented in the README); NULL-DACL directories are not identity-preserving under a grant+revoke round-trip (documented edge, the POC shares it); `whoami` and token-inspection cmdlets fail under the restricted token (diagnostic noise, documented); and BOTH confined modes run `pwsh` in ConstrainedLanguage mode — the restricted token trips PowerShell's lockdown detection, so `Add-Type`, non-core .NET statics (`[System.IO.*]::`, `[math]::`), COM objects, and reflection fail with "only core types" errors while `-f` formatting, property access, and core cmdlets/types keep working, and the language mode cannot be lifted back to FullLanguage from inside — taught to the model in the pwsh tool description and documented in the package README's Known Limitations; BOTH confined modes also deny named-pipe opens — libuv's piped-stdio spawns fail with EPERM (the POC-documented "no output redirection" boundary; inherited/ignored stdio and anonymous pipes work) — documented in the package README's Known Limitations and taught to the model in the pwsh tool description.
Bought: write-only confinement with no new OS floor (`CreateRestrictedToken` predates the mxc releases by two decades), reads/network/process visibility untouched exactly as the mode vocabulary requires, and fail-closed errors carrying the API name and the exact Win32 code. Cost: no read-side or network isolation; console isolation unavailable (hidden-console children die with `STATUS_DLL_INIT_FAILED`; children share the host console); standing ACE mutations on the granted roots (caller-owned directories; workspace ACEs stand forever by design — the reuse cache, invisible residue when a workspace is renamed — temp ACEs revoked by provider dispose together with the derived private temp directory — a crash leaves both behind and the next resume fails loudly at the exclusive creation until temp hygiene reclaims the directory); grant materialization is an EAGER full-tree propagation (`SetNamedSecurityInfoW` walks every descendant immediately — tens of seconds on large workspaces), paid once per workspace per machine by the per-workspace identity; CIM is unavailable in BOTH confined modes (AuthUsers dropped from both lists — the WMI namespace security check fails, and `Get-ComputerInfo` silently returns incomplete results) as the price of closing the C:\-root tree-creation escape in both; FAT-class (non-ACL) targets outside the granted roots remain writable under both modes (no security descriptors to intersect — a legacy residue treated as unsupported, warn-only, documented in the README); NULL-DACL directories are not identity-preserving under a grant+revoke round-trip (documented edge, the POC shares it); `whoami` and token-inspection cmdlets fail under the restricted token (diagnostic noise, documented); and BOTH confined modes run `pwsh` in ConstrainedLanguage mode — the restricted token trips PowerShell's lockdown detection, so `Add-Type`, non-core .NET statics (`[System.IO.*]::`, `[math]::`), COM objects, and reflection fail with "only core types" errors while `-f` formatting, property access, and core cmdlets/types keep working, and the language mode cannot be lifted back to FullLanguage from inside — taught to the model in the pwsh tool description and documented in the package README's Known Limitations; BOTH confined modes also deny named-pipe opens — libuv's piped-stdio spawns fail with EPERM (the POC-documented "no output redirection" boundary; inherited/ignored stdio and anonymous pipes work) — documented in the package README's Known Limitations and taught to the model in the pwsh tool description.
## Testing
The product-visible Windows roster flip is win32-only, so the keyless snapshot fixtures — which must replay on macOS/Linux — cannot cover it; the bundle composition specs ([`base.spec.ts`](../../../../packages/bundle/base/tests/base.spec.ts), [`windows-shell.spec.ts`](../../../../apps/cli/tests/windows-shell.spec.ts)) plus the win32 real-runner suites (`packages/sandbox/sandbox-windows-acl/tests/`, `packages/bash/pwsh-sandbox/tests/`) are the substitute evidence, and the CI Windows lane owns the assembled signal. The grant machinery is pinned cross-platform by `packages/sandbox/sandbox-local/tests/acl-session.spec.ts` (record fold/provision with the ownership binding — a fork's copied parent record never provisions the child — tamper validation on the workspace/temp paths, one-shot materialization with the immediate-flush kick, exclusive temp creation with reparse-point rejection, fork/resume temp reuse, the standing-vs-revocable lifecycle across dispose and the mode-switch cycle, and the derived-SID argv contract — with the Win32 surface mocked) and on win32 by `workspace-sid.spec.ts` (derivation determinism/shape/distinctness), `grant.spec.ts` (real-DACL materialization: revocable paths revoke on dispose, standing paths survive it), the `acl.spec.ts` idempotent-grant fast-path and standing-ACE-after-dispose contract, the `failure-paths.spec.ts` suspension-orphan regression (AssignProcessToJobObject failure terminates the child), and the `runner.spec.ts` `--write-sid` contract (caller-owned grants, private temp subdir through TMP/TEMP, both-mode CIM-denial probes, the mode-downgrade regression — a standing grant ACE is inert under read-only and effective again on re-upgrade — the ambient-writable Public-probe regression (a C:\Users\Public subdirectory write is denied under both modes), and the ConstrainedLanguage pins in both modes, plus the grandchild-stdio matrix pins — inherited/ignored stdio spawns succeed while piped capture is DENIED in both modes). The runner-failure classification is exit-gated on 127 (a confined command that merely prints the `windows-acl-run:` signature on a non-127 exit is never misclassified as "the command did not run" — pinned in the pwsh-sandbox helper suite).
The product-visible Windows roster flip is win32-only, so the keyless snapshot fixtures — which must replay on macOS/Linux — cannot cover it; the bundle composition specs ([`base.spec.ts`](../../../../packages/bundle/base/tests/base.spec.ts), [`windows-shell.spec.ts`](../../../../apps/cli/tests/windows-shell.spec.ts)) plus the win32 real-runner suites (`packages/sandbox/sandbox-windows-acl/tests/`, `packages/bash/pwsh-sandbox/tests/`) are the substitute evidence, and the CI Windows lane owns the assembled signal. The grant machinery is pinned cross-platform by `packages/sandbox/sandbox-local/tests/acl-grants.spec.ts` (the derived private-temp identity — deterministic per session + workspace, distinct across sessions — one-shot materialization, exclusive temp creation with reparse-point rejection and self-cleanup on failure, clean-restart re-grant of the same derived directory, the standing-vs-revocable lifecycle across dispose and the mode-switch cycle, and the derived-SID argv contract — with the Win32 surface mocked) and on win32 by `workspace-sid.spec.ts` (derivation determinism/shape/distinctness), `grant.spec.ts` (real-DACL materialization: revocable paths revoke on dispose, standing paths survive it), the `acl.spec.ts` idempotent-grant fast-path and standing-ACE-after-dispose contract, the `failure-paths.spec.ts` suspension-orphan regression (AssignProcessToJobObject failure terminates the child), and the `runner.spec.ts` `--write-sid` contract (caller-owned grants, private temp subdir through TMP/TEMP, both-mode CIM-denial probes, the mode-downgrade regression — a standing grant ACE is inert under read-only and effective again on re-upgrade — the ambient-writable Public-probe regression (a C:\Users\Public subdirectory write is denied under both modes), and the ConstrainedLanguage pins in both modes, plus the grandchild-stdio matrix pins — inherited/ignored stdio spawns succeed while piped capture is DENIED in both modes). The runner-failure classification is exit-gated on 127 (a confined command that merely prints the `windows-acl-run:` signature on a non-127 exit is never misclassified as "the command did not run" — pinned in the pwsh-sandbox helper suite).
## Related