Summary

Workspace boundary enforcement currently has three related bypass risks. This issue tracks fixing all three in one pull request.

Details

R1 - Dangling Symlink Component Bypass

• What happens: Path validation can miss dangling symlink components during traversal checks.
• Why it matters: A symlink that is unresolved at validation time can later resolve to an external location.
• Impact: Read and write operations may escape workspace boundaries.
• Affected area: src/security/path.rs (check_symlink_escape).

R2 - TOCTOU Between Validation and Use

• What happens: The path is validated first, then used later for filesystem operations.
• Why it matters: A concurrent filesystem change can swap path components after validation but before open/write.
• Impact: Race-based workspace escape is possible.
• Affected area: Filesystem and file-consuming tools that call validate_path_in_workspace before I/O.

R3 - Hardlink Alias Bypass

• What happens: A file inside workspace can be a hardlink to an inode outside the intended workspace trust boundary.
• Why it matters: Prefix and symlink checks can pass while data access still mutates or reads external content.
• Impact: Policy bypass for read/write operations.
• Affected area: Any tool that reads or writes via validated paths.

Risk Matrix

PoC

R1 - Dangling symlink component bypass

1. Create a symlink inside workspace pointing to a missing target.
2. Validate a path traversing that symlink.
3. Create the target directory outside workspace after validation.
4. Perform file operation and observe potential boundary escape if not fail-closed.

R2 - TOCTOU between validation and use

1. Validate a candidate in-workspace path.
2. Before open/write, replace an intermediate component with a link to external location.
3. Continue with the file operation.
4. Observe boundary escape if operation trusts only stale validation result.

R3 - Hardlink alias bypass

1. Place a hardlink inside workspace that points to an external inode.
2. Validate the in-workspace hardlink path.
3. Read or write through this path.
4. Observe external inode access through a path that appears in-scope.

Impacts

Unauthorized cross path boundary

Credit

@zpbrent

Patch

f50c17e11ae3e2d40c96730abac41974ef2ee2a8