security: prevent SSRF DNS rebinding by dialing validated IP directly (#3)#582
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…#3) ValidateEndpointURL() resolved DNS during validation, but http.NewRequest re-resolved the hostname when actually dialing. An attacker controlling authoritative DNS could return a public IP for the validation lookup and a private IP (e.g. 169.254.169.254 cloud metadata) for the dial — a TOCTOU DNS rebinding bypass. Add validators.SafeHTTPClient that resolves the host once, rejects any private/loopback/link-local IPs, and pins http.Transport.DialContext to the validated IP. TLS still uses ServerName=host so SNI and certificate validation work normally. Updated callers: - internal/graphql/test_endpoint.go (admin webhook test) - internal/events/events.go (webhook dispatcher) Save-time validators (add_webhook.go, update_webhook.go) keep using ValidateEndpointURL since they don't make outbound HTTP requests.
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Summary
Closes a TOCTOU / DNS rebinding hole in webhook endpoint validation.
ValidateEndpointURLresolved DNS during validation buthttp.NewRequestre-resolved when dialing — an attacker controlling DNS could return a public IP for validation and a private IP (e.g.169.254.169.254) for the actual dial.Changes
validators.SafeHTTPClient(ctx, rawURL, timeout)that resolves the host once, rejects private/loopback/link-local IPs, and pinshttp.Transport.DialContextto the validated IP. TLS still usesServerName=hostso SNI and cert validation work normally.internal/graphql/test_endpoint.goandinternal/events/events.gonow useSafeHTTPClientinstead of constructing a freshhttp.Client.ValidateEndpointURLcallers (add_webhook.go,update_webhook.go) keep the existing format check — they don't make outbound HTTP.Test plan
go build ./...go test ./internal/validators/...http://169.254.169.254/) is rejected