Fix path fence bypass for relative paths with leading ".."

[dxbjavid]

PathFence.apply() calls path.normalize().toAbsolutePath(), so leading .. segments survive normalize() and toAbsolutePath() then prepends the working directory. The component-wise startsWith(root) check matches the prefix even though the real path escapes the fence, e.g. ${file:UTF-8:../secret} reads outside a fence rooted at the working directory. Resolve to absolute first, then normalize, for both the roots and the candidate path.

[garydgregory]

@dxbjavid
Thank you for the PR.
You must provide a unit test that fails when the changes to main are not applied. Otherwise, this is a regression waiting to happen.

[dxbjavid]

Added one. The existing ../ tests only passed because the escaped file didn't exist, so the read failed and got rethrown as IllegalArgumentException anyway. The new test in FileStringLookupTest points a relative .. path at a real file outside the fence: on current main the fence lets it through and the file is read (nothing thrown), with the fix it's rejected.

[garydgregory]

Hello @dxbjavid
Thank you for your prompt update.
I can see the new test failing now without the main changes; BUT the changes to the constructor are not needed for the test to pass.
Would you please add another test to validate the change to the constructor?
TY!

[dxbjavid]

Added testFenceRootWithParentSegment. It builds a fence rooted at target/.. (which resolves to the working dir) and reads an in-fence file. Without the constructor normalize the root keeps the trailing .., so the component-wise startsWith never matches and the legit file is wrongly rejected. The test fails on main and passes with the fix.

[garydgregory]

@dxbjavid
Thank you, merged.