fix(coderd): block SSRF in MCP OAuth2 discovery and client registration (#27989)

coderd/coderd.go

@@ -13,6 +13,7 @@ import (
 	"math"
 	"net/http"
 	httppprof "net/http/pprof"
+	"net/netip"
 	"net/url"
 	"path/filepath"
 	"regexp"
@@ -261,6 +262,13 @@ type Options struct {
 	SSHConfig codersdk.SSHConfigResponse
 
 	HTTPClient *http.Client
+	// MCPOAuth2DiscoveryAllowedIPRanges exempts IP ranges from the
+	// SSRF guard applied to MCP OAuth2 metadata discovery and dynamic
+	// client registration, which refuse private/internal destinations
+	// by default. This is a seam for tests, which serve their mock MCP
+	// servers on loopback; there is intentionally no user-facing
+	// configuration for it.
+	MCPOAuth2DiscoveryAllowedIPRanges []netip.Prefix
 	// ChatStreamPartsDialer dials remote chat stream parts.
 	// Set by enterprise for HA deployments. Nil uses chatd's local
 	// in-process channel dialer.