fix(security): block SSRF via user-supplied ICS feed URLs#259
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This was referenced May 29, 2026
## Why this change is needed `/user/add-ics-calendar-account` lets an authenticated user store an arbitrary `feedUrl`, and `ICSCalendar.GetCalendarEvents` later fetched it with a plain `http.Get(cal.FeedURL)`. Because the URL is fully attacker-controlled, this is a Server-Side Request Forgery (SSRF) primitive: a user could point the feed at - the cloud metadata endpoint (`http://169.254.169.254/...`) to try to steal instance credentials, - internal-only services reachable from the server, or - `localhost` admin interfaces, and have the server issue the request from inside the trust boundary. ## What this does - Adds `safeGet` (services/calendar/safe_http.go), which only allows `http`/ `https` URLs and dials through a client whose `Control` hook rejects any connection to a non-public IP (loopback, RFC1918 private, link-local incl. 169.254.169.254, unspecified, multicast, and CGNAT 100.64.0.0/10). - Because the check runs on the resolved address at connect time, it also defeats DNS-rebinding and re-validates on every redirect hop. - `ICSCalendar.GetCalendarEvents` now uses `safeGet` instead of `http.Get`. - Adds unit tests for the IP classification and scheme rejection. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Severity: 🟡 Medium — authenticated SSRF
The problem
/user/add-ics-calendar-accountstores an arbitrary user-suppliedfeedUrl, andICSCalendar.GetCalendarEventslater fetched it with:The URL is fully attacker-controlled, giving any signed-in user an SSRF primitive. They can make the server fetch:
http://169.254.169.254/…(instance credential theft),localhostadmin interfaces.The fix
New
safeGetinservices/calendar/safe_http.go:http/httpsschemes.http.Clientwhosenet.Dialer.Controlhook rejects any non-public resolved IP: loopback, RFC1918 private, link-local (incl.169.254.169.254), unspecified, multicast, and CGNAT100.64.0.0/10.ICSCalendar.GetCalendarEventsnow callssafeGet. Added unit tests for the IP classifier and scheme rejection (both pass).🤖 Generated with Claude Code