fix(sandbox): normalize launcher names before the command-prefix denylist - #934
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Ahead of tightening which command prefixes may be approved, make the upgrade path safe. A grant already on disk that the narrower rules reject fails validation on read, and that path rejects the entire grants file rather than the one entry. Every caller treats a read error as "no grant" (engine.go LookupCommandPrefix, ApprovedCommandPrefixes, and the Lookup in Evaluate), so one stale prefix would silently disable the user's persisted deny grants too, with the error text never reaching them. Bump the approval policy version instead and let the store's existing migration handle it: it backs the file up, keeps deny grants, invalidates prior approvals, and reports the counts once through the startup notice that both frontends already print. That is what the mechanism was built for. The v1-migration test pinned the policy version as a literal, so it now derives the expected value from the constant and will not need editing on the next bump.
…list unsafeCommandPrefixLauncher matched the program name as written, so python3.11, python2.7, python.exe, node.exe and git.exe all validated as ordinary commands and could be persisted as command-prefix grants. Lookup is a string-prefix match, so a single approval then auto-allowed every later invocation: granting [python3.11 -c] covers `python3.11 -c "import os; os.system(...)"` with no further prompt. internal/agent's commandName already normalizes case and Windows executable extensions for the allow side of the same decision; the deny side did not, and the two disagreeing is the bug. Reduce the program to the launcher it actually runs and match on that: executable extension, Windows' trailing dots and spaces (python. starts python.exe), CPython ABI flags, then a trailing version, testing the digit-stripped form as well so python3.11 and python3 both arrive as python. A name is only ever narrowed toward an existing entry, so the failure direction is an extra permission prompt, never a silent grant. Digits without a separator stay part of the name, which keeps base64, 7z and sha256sum grantable. Two Windows spellings cannot be resolved by name at all, so the shape is refused alongside a path: 8.3 short names truncate the stem, which makes POWERS~1.EXE unrecognizable, and python.exe::$DATA reaches the same executable through its default stream. Normalizing the first token before the banned-suggestion comparison keeps git.exe at parity with git. The list also gains launchers of the same class it already covers and that normalization cannot reach: cmd, wsl, the remaining POSIX shells, busybox, uv and uvx. Entries normalization now covers (/bin/bash, /bin/zsh, powershell.exe, python3, pypy3) are gone; the first two were already unreachable behind the path check above them. Covers the persisted store, the session-scoped grants the agent takes during a turn, the legacy-schema migration that prunes such a grant per entry, and the Windows spellings hermetically.
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Included review availability: 2 reviews are currently available. Your included PR review attempts over the past 7 days set your current allowance at 5 reviews per hour. WalkthroughCommand-prefix validation now normalizes launcher spellings before denylist checks. Policy version 2 invalidates affected approvals. Tests cover executable aliases, versioned names, Windows forms, migrations, and ordinary commands. ChangesCommand Prefix Security
Estimated code review effort: 3 (Moderate) | ~25 minutes Merge Risk: ⚪ Minimal · up to The change normalizes launcher names and retires affected persisted approvals through the existing policy migration path. No actionable merge-blocking risk remains beyond normal checks and review. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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In `@internal/sandbox/command_prefix.go`:
- Around line 232-240: Update trimLauncherABISuffix to recognize the
free-threaded CPython ABI suffix t alongside the existing suffixes, so
NormalizeCommandPrefix rejects python3.13t and python3.13t.exe from receiving
command-prefix grants. Add regression coverage for both launcher spellings.
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internal/agent/command_prefix_test.gointernal/execution/contracts.gointernal/sandbox/command_prefix.gointernal/sandbox/command_prefix_test.gointernal/sandbox/grants_test.go
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The ABI flags came from the pre-3.13 set, so "python3.13t" and "python3.13t.exe" normalized to themselves and stayed grantable as command prefixes while the GIL build "python3.13" was refused. A free-threaded interpreter runs arbitrary code just the same. Add "t" to the flags trimmed under the existing digit guard, which is what keeps ordinary names intact: "zstd" and "cat" have no digit beneath the trimmed letters, so they keep their own names and stay grantable. Reported by CodeRabbit on Gitlawb#934.
Same defect as the free-threaded build, found by sweeping the families already on the list for names it cannot reach: - nodejs is node on Debian and Ubuntu, and was grantable. - python3-dbg, python3.11-dbg and python3.13t-dbg are interpreters that run arbitrary code; so are bash-static, pwsh-preview and node-nightly. A closed set of build-channel suffixes now normalizes them. The set stays closed deliberately: a general "-word" strip would also swallow node-gyp, python3-config and ruby-lsp, which are ordinary tools a user should still be able to approve, and those are pinned as must-stay-grantable. - pnpm, yarn and bunx run package scripts exactly as npm and npx do, and npm and npx are already refused. - sudoedit escalates like sudo. The launcher-wrapper family (winpty, chroot, unshare, nsenter, parallel, script, unbuffer, taskset, flock) has the same inconsistency against the env/nohup/timeout/setsid entries already on the list, and is left for a separate decision rather than widened here.
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🤖 Prompt for all review comments with AI agents
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Inline comments:
In `@internal/sandbox/command_prefix_test.go`:
- Around line 20-24: Add rejection cases for the -debug and -beta suffixes in
the command-prefix test table, including examples such as python3-debug and
node-beta, so both deny paths have regression coverage.
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internal/sandbox/command_prefix.gointernal/sandbox/command_prefix_test.go
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Four of the six build-channel suffixes had regression cases; -debug and -beta did not, so removing either from the set left every test green. Both now fail RED when their entry is dropped. Reported by CodeRabbit on Gitlawb#934.
Update after the first review roundThree commits since the initial push, all green locally ( CodeRabbit found a real one and it is fixed ( That was a class rather than a letter, so I swept the families already on the list for spellings
Two decisions I did not make for you1. The policy bump means every user re-approves once. Not only users holding an affected grant. 2. The wrapper family is inconsistent and I left it alone. Worth stating plainly for both decisions: approving a prefix sets Separately, |
2 participants
Closes #933.
unsafeCommandPrefixLaunchermatched the program name as written, sopython3.11,python.exe,node.exeandcmdvalidated as ordinary commands and could be approved ascommand-prefix grants. Lookup is a string-prefix match, so one approved
[python3.11]grantauto-allows every later
python3.11 ...for that tool.internal/agent'scommandNamealready normalizes case and Windows executable extensions for the allow side of the same
decision; the deny side did not, and the two disagreeing is the bug.
What changed
Two commits, in this order on purpose.
1. Retire recorded approvals through a policy bump. A grant already on disk that the
narrower rules reject fails validation on read, and that path rejects the whole grants file
rather than the one entry. Every caller treats a read error as "no grant" (
engine.go:116,:130, and theLookupinEvaluate), so without this commit one stale prefix wouldsilently disable the user's persisted deny grants too, with the error text never reaching
them. Bumping
execution.PolicyVersionroutes the file through the migration the storealready has: it backs the file up, keeps deny grants, invalidates prior approvals and reports
the counts once through the startup notice both frontends print.
2. Normalize launcher names. Reduce the program to the launcher it runs before matching:
executable extension, Windows' trailing dots and spaces (
python.startspython.exe),CPython ABI flags, then a trailing version, testing the digit-stripped form as well so
python3.11andpython3both arrive aspython. A name is only ever narrowed toward anexisting entry, so the failure direction is an extra permission prompt, never a silent grant;
digits without a separator stay part of the name, which keeps
base64,7zandsha256sumgrantable.
Two Windows spellings cannot be resolved by name at all, so the shape is refused alongside a
path: 8.3 short names truncate the stem, which makes
POWERS~1.EXEunrecognizable, andpython.exe::$DATAreaches the same executable through its default stream.The list also gains launchers of the same class it already covers and that normalization
cannot reach:
cmd,wsl, the remaining POSIX shells,busybox,uvanduvx. Entriesnormalization now covers (
/bin/bash,/bin/zsh,powershell.exe,python3,pypy3) aregone; the first two were already unreachable behind the path check above them.
Verification
python3,python,node,git,sh,bash,sudo) stay refused; 24 previously accepted spellings are now refused; a30-command corpus (
cargo,kubectl,docker,base64,sha256sum,gcc-13,node-gyp,python3-config,s3cmd, ...) stays grantable.test, then GREEN with it restored.
holding
[python3.11 -c]keeps its deny grant, re-approves prefixes, writesgrants.json.policy-v1.backup, and prints[zero] sandbox grants updated for policy v2: migrated 1, invalidated 2; backup: ...once.per entry and keeps the valid prefix beside the retired one.
go test ./...,-raceoninternal/sandbox,internal/agent,internal/execution,go vet,gofmt, andgo buildfor linux, darwin and windows.Two things for maintainers
The policy bump is a product call, not just a fix detail. It means every user re-approves
their allow grants and prefix grants once on upgrade, not only users holding an affected one.
Denies survive and a backup is written.
migrateChangedPolicyalready drops all prefixes onany policy change, so this is the existing behavior of that mechanism rather than something
new, and approvals recorded under broken validation seemed worth retiring. If you would rather
keep the blast radius to the affected entries, say so and I will swap commit 1 for a
prefix-only drop on the read path.
#570 touches the same function. It adds trailing-wildcard tokens to
internal/sandbox/command_prefix.go, so whichever lands second needs a small rebase. Nobehavioral conflict: its wildcard is only valid on a non-first token, and everything here
applies to the program token.
Known limitation, left alone deliberately: a program name containing a zero-width space is
still grantable. It names a different file than the interpreter, so the grant does not execute
anything, and refusing it would be unicode policy rather than launcher normalization.
Summary by CodeRabbit
Security
cargo build.Bug Fixes
Migration