fix: prevent path traversal via symlinks and cross-drive paths

[mluckydream]

Fixes #8313

Summary

Enhanced Filesystem.contains() to prevent directory escape attacks via symlinks and cross-drive paths on Windows.

Changes

• src/util/filesystem.ts: Enhanced contains() function
  • Use realpathSync() to resolve symlinks to canonical paths
  • Add Windows cross-drive validation (check drive letters match)
  • Fallback to lexical check if path doesn't exist
• src/file/index.ts: Removed resolved TODO comments (4 lines)

Security Improvements

Prevents symlink escape attacks
Prevents Windows cross-drive path bypass
Maintains backward compatibility

Testing

Tested on macOS (darwin-arm64):

• Created symlink pointing outside project directory
• Verified contains() correctly rejects escaped paths
• Verified normal paths still work correctly

Test scenario

# Create test symlink
ln -s /etc/passwd ./packages/opencode/test-symlink

# Verify it's rejected by containsPath()
# Expected: Access denied error

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found several related PRs that address similar security concerns with symlinks and filesystem containment checks. However, none of these are duplicates of PR #8316. Here are the related PRs:

Previously merged/closed security improvements:

1. PR fix: prevent symlink escape in Filesystem.contains #6403 - "fix: prevent symlink escape in Filesystem.contains"

   • Earlier attempt to address symlink escape vulnerabilities in the same Filesystem.contains() function

2. PR fix: Harden filesystem contains checks #7449 - "fix: Harden filesystem contains checks"

   • Another hardening effort for filesystem containment validation

3. PR fix: address external_directory gaps and improve symlink checks #7515 - "fix: address external_directory gaps and improve symlink checks"

   • Broader symlink check improvements alongside external_directory fixes

These PRs appear to be earlier iterations or related security work on the same vulnerability area, but PR #8316 represents a more comprehensive fix addressing both symlinks AND Windows cross-drive path traversal attacks.

No open duplicate PRs found - PR #8316 is the current attempt to address issue #8313 with enhanced protections.