feat(loading): sandbox local loading with WithRoot (GHSA-v2xp-g8xf-22pf)#203
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Allow for optional secure sandboxing of the spec loader when reading local files. The defaults remain non-secure as it would introduce severe breaking changes downstream. Sandboxing therefore remains opt-in. LoadFromFileOrHTTP resolved file:// URIs and bare paths straight to os.ReadFile with no confinement, so a caller that forwards untrusted input could read any file the process can access (file:///etc/passwd, absolute paths, etc.). The advised mitigation, WithFS(os.DirFS(dir)), blocks ".." traversal but not symlinks that escape the root. Add WithRoot(dir): an opt-in, non-breaking option that confines local reads to dir via os.Root. It resolves every requested path relative to dir and rejects absolute paths, ".." traversal, and escaping symlinks -- including the symlink case os.DirFS misses. The root is opened per read and closed (no fd leak); the open error is wrapped with ErrLoader. WithRoot and WithFS are mutually exclusive (last applied wins). Also fix a latent bug in LoadStrategy: it applied native separators (filepath.FromSlash) to fs-backed loaders, breaking multi-segment paths on Windows for any fs.FS. fs-backed loaders now receive forward slashes on all platforms, preserving embed.FS's existing always-"/" rule; the native path is kept only for the default os.ReadFile loader. Document the default permissive behavior and steer untrusted-input callers to WithRoot in the package and function godoc. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Signed-off-by: Frederic BIDON <fredbi@yahoo.com>
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #203 +/- ##
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+ Coverage 92.48% 92.53% +0.04%
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Files 54 54
Lines 2582 2598 +16
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+ Hits 2388 2404 +16
Misses 148 148
Partials 46 46 ☔ View full report in Codecov by Sentry. |
The remote loader is a thin wrapper over a standard net/http client and, like http.DefaultClient, follows redirects and applies no destination filtering. A caller that forwards untrusted URLs can thus trigger server-side request forgery (internal services, cloud metadata). Embedding a network policy (IP denylists, allowlists) in a general fetch utility is the wrong layer and invites false confidence: the existing WithHTTPClient option already lets a caller install a guarded transport that filters destinations at dial time, which is the only point that survives redirects and DNS rebinding. Document the exposure in the package godoc and add a runnable, self-validating example showing the WithHTTPClient + net.Dialer.Control recipe. Separately, fix a latent correctness bug: LoadStrategy routed any path with a bare "http" prefix to the remote loader, so a local file named e.g. "httpbin.json" was misrouted, and an uppercase "HTTP://" URL was sent to the local loader. Require a real, case-insensitive http:// or https:// scheme instead. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Signed-off-by: Frederic BIDON <fredbi@yahoo.com>
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Allow for optional secure sandboxing of the spec loader when reading local files.
The defaults remain non-secure as it would introduce severe breaking changes downstream. Sandboxing therefore remains opt-in.
LoadFromFileOrHTTP resolved file:// URIs and bare paths straight to os.ReadFile with no confinement, so a caller that forwards untrusted input could read any file the process can access (file:///etc/passwd, absolute paths, etc.). The advised mitigation, WithFS(os.DirFS(dir)), blocks ".." traversal but not symlinks that escape the root.
Add WithRoot(dir): an opt-in, non-breaking option that confines local reads to dir via os.Root. It resolves every requested path relative to dir and rejects absolute paths, ".." traversal, and escaping symlinks -- including the symlink case os.DirFS misses. The root is opened per read and closed (no fd leak); the open error is wrapped with ErrLoader. WithRoot and WithFS are mutually exclusive (last applied wins).
Also fix a latent bug in LoadStrategy: it applied native separators (filepath.FromSlash) to fs-backed loaders, breaking multi-segment paths on Windows for any fs.FS. fs-backed loaders now receive forward slashes on all platforms, preserving embed.FS's existing always-"/" rule; the native path is kept only for the default os.ReadFile loader.
Document the default permissive behavior and steer untrusted-input callers to WithRoot in the package and function godoc.
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Please select: 🆕 New feature or enhancement|🔧 Bug fix'|📃 Documentation update
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