fix(sandbox): Landlock + relative-token block for workspace FS escapes - #74
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…kens Allowlist only flagged tokens starting with / ~ ., so relative symlink indirection (python os.sep symlink + cat leak) and interpreter path obfuscation bypassed workspace_only. Namespaces alone do not hide the host FS. Apply Landlock to the configured workspace in sandbox_exec and resolve bare relative tokens against the workspace in the allowlist. Co-authored-by: esadrianno <esadrianno@gmail.com>
Passing REFER/TRUNCATE in handled_access_fs makes create_ruleset fail on ABI 1, skipping the whole FS policy. Probe the ABI, mask unknown bits, and pass the ABI-1 attr size to avoid E2BIG. Co-authored-by: esadrianno <esadrianno@gmail.com>
This was referenced Aug 27, 2026
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Summary
CRITICAL workspace escape that survived open PRs #66/#68:
With
sandbox.enabled+workspace_only,has_path_charsonly flags tokens starting with/~.. Concrete trigger on main:python3 -c 'import os; os.symlink(os.path.join(os.sep,"etc","passwd"),"leak")'→ allowlist allow (no absolute/fragment; survives fix(sandbox,gateway): shell allowlist quoted-path bypass + bind to configured host #68 embedded-path scan)cat leak→ allowlist allow (bare relative name)unshare(CLONE_NEWNS)alone does not hide the host FS, so the shell tool could read host secrets.Fix
sandbox_exec: whenworkspace_pathis set, apply a Linux Landlock ruleset (workspace RW + minimal RO system paths for/bin/sh/ interpreters). Blocks symlink andchr(47)/os.sepindirection at execution time.allowlist_check_shell_command: resolve bare relative tokens against the workspace and reject whenrealpathescapes (defense-in-depth forcat leak).Test plan
tests/test_allowlist—test_relative_symlink_indirectiontests/test_sandbox— Landlock symlink + obfuscated python/etc/passwdread blockedcat leakblocked by allowlist; sandbox output has noroot:x: