fix: Potential fix for code scanning alert no. 9: Uncontrolled data used in path expression

[skyoo2003]

Potential fix for https://github.com/skyoo2003/devcloud/security/code-scanning/9

General fix: validate untrusted path components before building paths, and enforce containment using path semantics (not just string prefix). For this code, the best minimal fix is to harden safePath in internal/services/s3/store.go:

1. Reject unsafe path components in parts:
   • empty component
   • . or ..
   • any path separator (/ or \)
2. Build and clean path as today.
3. Use filepath.Rel(fs.baseDir, cleaned) and reject if:
   • rel == ".." or starts with ".."+separator (escapes root)
   • filepath.IsAbs(rel) (unexpected absolute rel)

This preserves existing behavior for valid names while preventing traversal patterns and making the sanitizer recognizable and sounder for CodeQL.

Suggested fixes powered by Copilot Autofix. Review carefully before merging.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Hardens FileStore.safePath to defensively validate individual path components and enforce containment under baseDir using filepath.Rel-based path semantics instead of string-prefix checks, mitigating path traversal/code scanning issues.

File-Level Changes

Change	Details	Files
Strengthen safePath to reject unsafe components and use path-semantic containment checks to prevent directory traversal.	Add per-component validation rejecting empty components, dot/dot-dot segments, and any component containing path separators Keep existing join-and-clean behavior while still constructing the path under fs.baseDir Use filepath.Rel to compute the path of the cleaned target relative to baseDir and treat errors as invalid paths Replace the previous strings.HasPrefix-based containment check with checks on the relative path to detect escaping of baseDir or unexpected absolute paths	internal/services/s3/store.go

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[sourcery-ai]

Hey - I've left some high level feedback:

• Consider normalizing fs.baseDir (e.g., filepath.Abs + filepath.Clean) when constructing FileStore so that filepath.Join, filepath.Clean, and filepath.Rel all operate on a consistent, absolute base path and the containment check cannot be bypassed by variations in baseDir (e.g., trailing separators or relative components).
• In the safePath component validation loop, consider using os.IsPathSeparator or checking against filepath.Separator instead of hardcoding "/" and "\\" so the separator validation remains correct and portable across platforms.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Consider normalizing `fs.baseDir` (e.g., `filepath.Abs` + `filepath.Clean`) when constructing `FileStore` so that `filepath.Join`, `filepath.Clean`, and `filepath.Rel` all operate on a consistent, absolute base path and the containment check cannot be bypassed by variations in `baseDir` (e.g., trailing separators or relative components).
- In the `safePath` component validation loop, consider using `os.IsPathSeparator` or checking against `filepath.Separator` instead of hardcoding `"/"` and `"\\"` so the separator validation remains correct and portable across platforms.

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