API-SECURITY5 MIN READ
Walk the SSRF-safe fetcher
Sequence the main design controls for an API feature that fetches user-supplied URLs.
The feature Customers paste a webhook URL. Your API fetches it to validate reachability and show metadata. The server can reach places the customer cannot. SSRF defense chain Parse -> resolve -> restrict egress -> revalidate redirects -> cap response Each layer handles a bypass the previous layer cannot reliably catch alone. Shortcut if url starts with https then fetch A hostile URL fails closed before reaching internal services. Validate the destination at every point the destination can change. 01 Scheme 02 DNS/IP 03 Redirect 04 Fresh case
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