Security improvements to HandleSSHConfig endpoint:
- Add defer r.Body.Close() for proper resource cleanup
- Return 413 status for oversized requests with errors.As check
- Switch from blocklist to allowlist-based directive validation
- Use case-insensitive parsing with comment stripping via bufio.Scanner
- Add Content-Type: application/json header to response
Codex identified that blocklist approach was insufficient and recommended
allowlist validation to prevent unexpected directives. Only permits the
specific SSH directives Pulse needs for ProxyJump configuration.
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