fix: Potential fix for code scanning alert no. 7: Uncontrolled data used in path expression

[skyoo2003]

Potential fix for https://github.com/skyoo2003/devcloud/security/code-scanning/7

General fix: ensure user-derived path components are validated as safe path components, and enforce canonical containment checks using filepath.Rel (or equivalent), while handling all path resolution errors.

Best fix here without changing functionality:

1. In internal/services/lambda/store.go, harden codePath:
   • Reject accountID / functionName if they are absolute, contain separators, or contain ...
   • Build candidate path as before.
   • Resolve s.codeDir and candidate to absolute paths with error checks.
   • Use filepath.Rel(absBase, absCandidate) and reject if it starts with .. or is absolute.
   • Return the absolute candidate path (safe canonical path).
2. No behavioral change to API contract; only invalid/path-traversal names now fail deterministically.

No changes are required in provider.go for this specific sink once store-layer validation is robust (defense-in-depth at sink boundary).

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

[sourcery-ai]

Reviewer's Guide

Hardens Lambda code storage path construction to validate user-derived path components and enforce robust canonical containment checks against the configured code directory, returning a fully resolved safe absolute path or a deterministic error on invalid/traversal input.

File-Level Changes

Change	Details	Files
Harden Lambda function code path construction against path traversal by validating components and enforcing canonical containment within codeDir with proper error handling.	Introduce an isSafeComponent helper to reject empty, relative, absolute, or separator-containing accountID and functionName values. Construct the code.zip path as before via filepath.Join and filepath.Clean, but then resolve both base directory and candidate path to absolute paths with error checks. Use filepath.Rel to compute the relative path from the base directory to the candidate, rejecting results that escape the base (".." prefix) or are absolute. Return the canonical absolute code path instead of the cleaned but potentially relative path.	internal/services/lambda/store.go

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[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• Returning absCleaned instead of the previously relative cleaned value changes the function’s output semantics; double-check callers aren’t relying on codePath returning a path relative to s.codeDir before making this behavior change.
• The isSafeComponent helper rejects any value containing "..", which is stricter than just blocking ".." as a component and may unexpectedly reject valid names (e.g., "user..1"); consider tightening the check to disallow only path-segment traversal rather than any substring.
• The new path validation logic (clean + Abs + Rel checks) is fairly intricate; consider adding a short comment or extracting it into a reusable helper to clarify the invariants (e.g., which inputs are considered valid components and why) and reduce the chance of future regressions.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Returning `absCleaned` instead of the previously relative `cleaned` value changes the function’s output semantics; double-check callers aren’t relying on `codePath` returning a path relative to `s.codeDir` before making this behavior change.
- The `isSafeComponent` helper rejects any value containing `".."`, which is stricter than just blocking `".."` as a component and may unexpectedly reject valid names (e.g., `"user..1"`); consider tightening the check to disallow only path-segment traversal rather than any substring.
- The new path validation logic (clean + Abs + Rel checks) is fairly intricate; consider adding a short comment or extracting it into a reusable helper to clarify the invariants (e.g., which inputs are considered valid components and why) and reduce the chance of future regressions.

## Individual Comments

### Comment 1
<location path="internal/services/lambda/store.go" line_range="157" />
<code_context>
-// It validates the result stays under codeDir to prevent path traversal.
+// It validates path components and ensures the resolved path stays under codeDir.
 func (s *LambdaStore) codePath(accountID, functionName string) (string, error) {
+	isSafeComponent := func(v string) bool {
+		if v == "" || v == "." || v == ".." {
+			return false
+		}
+		if filepath.IsAbs(v) {
+			return false
+		}
+		if strings.Contains(v, "/") || strings.Contains(v, "\\") || strings.Contains(v, "..") {
+			return false
+		}
</code_context>
<issue_to_address>
**suggestion (bug_risk):** The `strings.Contains(v, "..")` check may be stricter than necessary and disallow valid IDs with consecutive dots.

This condition rejects any value containing ".." anywhere (e.g. "user..1"), which may be valid depending on how IDs are defined. If the aim is only to block path traversal, `filepath.Clean` + `Rel` plus the explicit `v == ".."` check already cover that. Consider dropping the `strings.Contains(v, "..")` check and relying on the path normalization instead, unless you explicitly want to forbid all such IDs.

```suggestion
		if strings.Contains(v, "/") || strings.Contains(v, "\\") {
```
</issue_to_address>

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