Miguel's second P1 on #2975, and he is right that my first fix only closed half
of it. `resolve()` and `relative()` are string operations and do not follow
links. Registry items are copied in recursively with symlinks preserved, so a
PR shipping `escape -> /tmp/outside` and declaring `target: "escape/pwned.txt"`
passed the lexical check, `mkdirSync` followed the link, and `cpSync` wrote
outside the project.
Reproduced before fixing: the old predicate returned one allowed copy and the
file appeared outside the project. Both directions were exposed — a symlinked
`path` reads a runner file in just as readily.
Containment is now filesystem-aware. No existing component of a candidate may
be a symlink, and the candidate's real location — resolved through its deepest
existing ancestor — has to sit under the project's own real path. A symlink is
refused rather than followed, even one pointing back inside the project:
nothing in the registry needs one, and following it would mean trusting the
target not to change between the check and the copy.
The tests are real fixtures now instead of string cases, because a purely
lexical suite is exactly what stayed green through the bypass. Twelve of them,
covering a symlinked target directory, a symlinked source file, a deeper path
through a symlinked component, an inward-pointing symlink, plus the lexical and
absolute cases from before.
Miguel's P1 on #2975, and it is real. `catalog-previews.yml` triggers on
`pull_request` for anything under `registry/blocks/**` or
`registry/components/**`, so `registry-item.json` arrives from the pull request
and is untrusted. `mirrorRegistryTargets` joined `files[].path` and
`files[].target` under the temp project and called `cpSync` on the result, and
`join()` walks out of its first argument. A `path` of `../../../../etc/passwd`
reads an arbitrary runner file into the project — which the job then uploads as
an artifact — and a `target` of the same shape writes an arbitrary runner path.
Both sides are now resolved and rejected when `relative(projectDir, candidate)`
is absolute or starts with `..`. Traversal that lands back inside the project
still works, so `nested/../demo.html` is unaffected.
Containment lives in `scripts/registry-target-paths.mjs` rather than inline,
because the traversal cases have to be testable and importing
`generate-catalog-previews.ts` drags in the producer. `existsSync` is injected
so the decision cannot depend on whether the target happens to exist on the
runner. Eight tests, covering traversal on each field separately, absolute
paths on each field, the sibling directory that shares the project's prefix,
and traversal that returns inside.
Verified end to end on a real tree, not only in unit tests: a manifest asking
to read `../secret.txt` and write `../pwned.txt` produces neither file, while
the legitimate entry still copies.
I introduced the wrapper when I extracted this block for a complexity finding
earlier in the stack, and did not look at what it was joining.
ukimsanov