fix: Potential fix for code scanning alert no. 4: Uncontrolled data used in path expression

[skyoo2003]

Potential fix for https://github.com/skyoo2003/devcloud/security/code-scanning/4

Best fix: validate untrusted path components as single safe names before path construction, then keep robust containment verification.

In internal/services/lambda/store.go, update codePath to:

1. Reject empty accountID/functionName.
2. Reject any value containing /, \, or .. (single-component policy).
3. Resolve both base and target via filepath.Abs and handle errors.
4. Keep a strict “within base directory” check before returning path.

This preserves existing behavior (store code under codeDir/accountID/functionName/code.zip) while preventing traversal through crafted names.

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

[sourcery-ai]

Reviewer's Guide

Tightens validation and containment checks for Lambda function code paths by enforcing single-component identifiers, resolving absolute paths safely, and using a robust relative-path containment check to prevent path traversal.

File-Level Changes

Change	Details	Files
Harden codePath to validate path components and perform safer containment checks against the base code directory.	Introduce validPathComponent helper to enforce that account and function identifiers are single, non-traversing path components with no separators or '..' Reject empty accountID or functionName and return descriptive errors for invalid path components before constructing paths Resolve both the base code directory and the computed code path to absolute paths with error handling instead of ignoring resolution errors Replace prefix-based containment check with a filepath.Rel-based check that rejects paths that resolve outside the base directory	internal/services/lambda/store.go

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[sourcery-ai]

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

• The manual checks for /, \, and .. in accountID and functionName are a bit repetitive; consider extracting a small helper (e.g., validatePathComponent) or using strings.ContainsAny for the separator checks to reduce duplication and make the validation rules clearer.
• The containment check uses HasPrefix(absCleaned, absBase+string(filepath.Separator)), which excludes the case where absCleaned == absBase; if storing a zip directly under codeDir is ever expected, consider explicitly allowing equality instead of requiring a subdirectory.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The manual checks for `/`, `\`, and `..` in `accountID` and `functionName` are a bit repetitive; consider extracting a small helper (e.g., `validatePathComponent`) or using `strings.ContainsAny` for the separator checks to reduce duplication and make the validation rules clearer.
- The containment check uses `HasPrefix(absCleaned, absBase+string(filepath.Separator))`, which excludes the case where `absCleaned == absBase`; if storing a zip directly under `codeDir` is ever expected, consider explicitly allowing equality instead of requiring a subdirectory.

## Individual Comments

### Comment 1
<location path="internal/services/lambda/store.go" line_range="164-175" />
<code_context>
-	absBase, _ := filepath.Abs(s.codeDir)
-	absCleaned, _ := filepath.Abs(cleaned)
+
+	absBase, err := filepath.Abs(s.codeDir)
+	if err != nil {
+		return "", fmt.Errorf("resolve base code directory: %w", err)
+	}
+	absCleaned, err := filepath.Abs(cleaned)
+	if err != nil {
+		return "", fmt.Errorf("resolve code path: %w", err)
+	}
+
 	if !strings.HasPrefix(absCleaned, absBase+string(filepath.Separator)) {
 		return "", fmt.Errorf("path traversal detected: %s", cleaned)
 	}
</code_context>
<issue_to_address>
**🚨 suggestion (security):** Using `HasPrefix` for directory containment can be fragile; `filepath.Rel` would be more robust.

String prefix checks can fail if path normalization or casing changes (especially on Windows) or if separator assumptions differ. A safer approach is to compute the relative path from the base and ensure it doesn’t escape:

```go
rel, err := filepath.Rel(absBase, absCleaned)
if err != nil {
    return "", fmt.Errorf("resolve relative code path: %w", err)
}
if strings.HasPrefix(rel, ".."+string(filepath.Separator)) || rel == ".." {
    return "", fmt.Errorf("path traversal detected: %s", cleaned)
}
```

This checks containment without relying on absolute-path string prefixes.

```suggestion
	absBase, err := filepath.Abs(s.codeDir)
	if err != nil {
		return "", fmt.Errorf("resolve base code directory: %w", err)
	}
	absCleaned, err := filepath.Abs(cleaned)
	if err != nil {
		return "", fmt.Errorf("resolve code path: %w", err)
	}

	rel, err := filepath.Rel(absBase, absCleaned)
	if err != nil {
		return "", fmt.Errorf("resolve relative code path: %w", err)
	}
	if rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
		return "", fmt.Errorf("path traversal detected: %s", cleaned)
	}
```
</issue_to_address>

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[skyoo2003]

@sourcery-ai review

[sourcery-ai]

Hey - I've reviewed your changes and they look great!

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_{Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.}