fix(sandbox): keep Windows restricted-token SIDs narrow and fail closed on DenyRead - #1006
fix(sandbox): keep Windows restricted-token SIDs narrow and fail closed on DenyRead#1006euxaristia wants to merge 9 commits into
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Co-Authored-By: cairn-code <cairn-code@users.noreply.github.com>
…setup Skip inherited ACEs when preserving read deny entries, correct syntax in the command runner error message, and evaluate unsupported DenyRead profiles before the elevation check in Windows sandbox setup. Refs Gitlawb#640
…ean dead descendant machinery. Refs Gitlawb#640
Greptile SummaryThis PR rejects Windows restricted-token profiles containing DenyRead, narrows newly applied DenyWrite masks, and refreshes setup markers for legacy ACL migration.
Confidence Score: 3/5The PR should not merge until legacy descendant ACL migration and the malformed denied-write smoke probes are corrected. Setup refresh only migrates exact paths represented in the current plan, leaving previously propagated SYNCHRONIZE denies behind, while the new cmd.exe quoting can make confinement probes pass because of malformed redirects rather than enforced access denial. Files Needing Attention: internal/sandbox/windows_acl_apply_windows.go; internal/sandbox/runner_windows_integration_test.go
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| Filename | Overview |
|---|---|
| internal/sandbox/windows_acl_apply_windows.go | Adds exact-path in-place ACL migration, but leaves legacy descendant ACEs outside the migration path. |
| internal/sandbox/runner_windows_integration_test.go | Adds broader smoke probes, but command quoting can make denied writes fail syntactically and probe cleanup does not establish ownership. |
| internal/sandbox/windows_command_runner.go | Consistently rejects unsupported restricted-token DenyRead profiles before persistent setup or command launch. |
| internal/sandbox/windows_setup.go | Bumps the setup marker schema and adds early DenyRead rejection, though the resulting refresh cannot migrate unplanned descendant ACEs. |
| internal/sandbox/windows_acl.go | Extends ACL entry identity with inheritance shape and defines migration actions without introducing a current plan-generation path for revocation. |
Flowchart
%%{init: {'theme': 'neutral'}}%%
flowchart TD
A[Existing schema-v4 installation] --> B[Schema-v5 setup refresh]
B --> C[Build current ACL plan]
C --> D{Exact DenyWrite path and SID in plan?}
D -->|Yes| E[Migrate matching ACE to narrow mask]
D -->|No: legacy descendant| F[ACE is not visited]
F --> G[Legacy SYNCHRONIZE deny remains]
Reviews (1): Last reviewed commit: "Migrate legacy Windows DenyWrite ACEs, r..." | Re-trigger Greptile
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Included review availability: Your plan provides up to 4 included reviews per hour; 2 remain after this review. WalkthroughThe Windows sandbox now rejects ChangesWindows sandbox enforcement
Estimated code review effort: 4 (Complex) | ~60 minutes Merge Risk: ⚪ Minimal · up to Windows sandboxing now rejects unsupported DenyRead profiles before provisioning and safely migrates legacy DenyWrite ACL entries while preserving read-deny behavior. No current merge-blocking risk is identified. Sequence Diagram(s)sequenceDiagram
participant SandboxManager
participant WindowsCommandRunner
participant WindowsSetup
participant CapabilitySIDState
SandboxManager->>WindowsCommandRunner: validate restricted-token DenyRead profile
WindowsCommandRunner-->>SandboxManager: return unsupported-profile error
WindowsSetup->>WindowsCommandRunner: validate permission profile
WindowsCommandRunner-->>WindowsSetup: return status 1 before setup
WindowsCommandRunner->>CapabilitySIDState: load or create state only after validation
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Vasanthdev2004
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Vasanthdev2004
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The DenyRead decision is right and I verified it holds on the path that actually reaches it. One thing in the ACL migration needs fixing first.
The migration silently ignores NoInherit
prepareWindowsACLPathGroupEntries migrates a legacy deny in place and then continues, so the requested entry is never applied. The migration patches ace.Mask only, never ace.Header.AceFlags. On a directory that already carries a legacy inheritable deny, a NoInherit: true entry therefore leaves the inheritable ACE inheritable and never installs the direct-only one.
Seeded a legacy broad inheritable deny, then applied {Action: DenyWrite, NoInherit: true}:
BEFORE dir type=1 flags=0x0 mask=0x130116
BEFORE dir type=1 flags=0xb mask=0x40110000
AFTER dir type=1 flags=0x0 mask=0xf0156
AFTER dir type=1 flags=0xb mask=0xf0156 <- still inherit-only
AFTER child type=1 flags=0x13 mask=0xf0156 <- child still inherits
Control on a directory with no pre-existing deny for that SID:
PROBE clean dir type=1 flags=0x0 mask=0xf0156
PROBE RESULT: NoInherit WORKS on a clean directory
So NoInherit itself is fine; the migration defeats it, on exactly the upgraded hosts the migration exists for. That also contradicts the invariant this PR states in dedupeWindowsACLEntries, that collapsing the two shapes "could silently promote a deliberately non-inherited shared-path deny into an inheritable one". The migration does precisely that.
The consequence is over-application rather than a hole: the child gets a deny it should not have. On a shared system directory that is the propagation hazard the flag was added to avoid, since SetSecurityInfo pushes an inheritable ACE onto existing descendants.
Nothing in production emits NoInherit today, so this breaks nobody right now. I am still asking for it before merge, because the first caller that sets the flag on a path with a legacy deny gets no error and no effect. Either carry the entry's inheritance into the migrated ACE, or fall through to the normal EXPLICIT_ACCESS path when the requested inheritance differs from what is on the object.
Verified, for what it is worth
The rejection fires where it needs to. deny_read is reachable without any config key, through the request_permissions tool, and I drove that end to end into the plan builder:
PROBE profile DenyRead count = 1
PROBE level=unelevated -> rejected as intended
PROBE level=native -> rejected as intended
Both marker schema versions bumped, which is what makes the migration actually run on upgrade rather than sitting behind a cached marker. Good call.
Two smaller things
The description says it deletes unused descendant scanning and path resolution files. Those files exist at neither the merge base nor the head, so that bullet looks left over from an earlier revision.
Overlap you should know about
#808 makes the same call and refuses denyRead too, so whichever lands second will conflict in windows_setup_windows.go and windows_command_runner_windows.go. Yours is better placed than mine: it rejects on the profile at four entry points, where mine keys on the read grant appearing in the built plan. If this lands first I will drop my version and rebase onto yours.
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Inline comments:
In `@internal/sandbox/runner_windows_integration_test.go`:
- Around line 617-618: Update the cleanup logic around os.ReadFile in the test
to ignore only os.ErrNotExist and call t.Errorf for all other read failures,
including sharing, permission, and I/O errors. Preserve the existing handling
for successfully read files.
- Around line 619-620: Update the cleanup ownership check in the probe flow to
generate and retain a unique per-probe marker, write that marker into the file,
and remove the path only when its full content matches the marker. Replace the
broad strings.HasPrefix check around os.Remove so unrelated files in the shared
directory are preserved.
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Inline comments:
In `@internal/sandbox/windows_acl_apply_windows.go`:
- Line 385: Update the migration logic around migratedAce and
windowsIsExperimentalWriteDenyMask so converting a combined legacy read/write
deny ACE preserves its DenyRead bit while narrowing only the write-denial bits.
Split the ACE or otherwise retain non-write denial bits, and add a regression
test covering one combined deny ACE.
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internal/sandbox/runner_windows_integration_test.gointernal/sandbox/windows_acl_apply_windows.gointernal/sandbox/windows_acl_apply_windows_test.go
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Summary
Windows restricted-token sandboxing cannot support
DenyReadwithout access-time confinement because omittingUsers/Authenticated Usersprevents system binaries from executing, while adding those groups reopens ambient write access. This PR rejects unsupportedDenyReadconfigurations upfront before setup/token creation, migrates legacySYNCHRONIZEDenyWrite ACEs in-place withNoInheritsupport on upgraded hosts, and randomizes shared-directory smoke test probes with unique ownership tokens.Refs #639
Changes
DenyReadprofiles upfront ininternal/sandbox/windows_command_runner.goandwindows_setup_windows.go.DenyWriteACEs containingSYNCHRONIZEin-place while honoringNoInheritand preserving co-residentDenyReadininternal/sandbox/windows_acl_apply_windows.go.DenyReadbits and narrow write denial when migrating combined legacy read/write deny ACEs.allocateSharedDirectoryProbeand verify unique marker ownership on cleanup ininternal/sandbox/runner_windows_integration_test.go.Prior reviewer feedback addressed
NoInheritintowindowsMigrateDenyWriteInDACLto drop inherit-only ACEs and clear inheritance flags; removed stale references to deleted descendant scanning files from PR description.os.ErrNotExistread errors in probe cleanup and validated exact per-probe marker content before removal.DenyReadbits inwindowsMigrateDenyWriteInDACLandwindowsFilterDACLwhen migrating combined legacy read/write deny ACEs, updatedwindowsIsExperimentalWriteDenyMaskto avoid classifying combined masks as pure write-deny masks, and added regression testTestWindowsACLDenyWriteMigratesCombinedLegacyReadWriteDeny.Test plan
go test -v ./internal/sandbox -run TestWindowsACLgo test -v ./internal/sandbox -run TestSharedDirectoryProbeLifecyclego test ./internal/sandboxgo vet ./internal/sandbox/...go run ./cmd/zero-release buildgo run ./cmd/zero-release smokeSummary by CodeRabbit
DenyReadconfigurations before making system changes or launching commands.DenyReadlimitations for restricted-token modes.