Confirmed with the product team that the official GUI client applies no
client-side SSRF interception to downloads, so the IP-literal refusal
was the last remaining client-side interception beyond transport
hygiene. Dedicated deployments make every host dimension (domain,
port, network location) unenumerable, and an IP-literal host is just
another network location.
- ValidateDownloadURL accepts any HTTPS host, IP literals included;
HTTPS scheme, userinfo refusal, and per-hop redirect re-validation
stay as the transport baseline
- this retires the third and last interception layer after the host
allowlist removal and the dial-time public-IP refusal (be52ca5d)
- upload targets stay unaffected: trustedUploadHost keeps rejecting
non-DingTalk/OSS hosts, so local file bytes cannot be PUT to an IP
- regressions: IP-literal URLs pass validation on the shared and chat
download paths; userinfo and plain-HTTP URLs stay rejected