volume: gate FetchAndWriteNeedle behind admin auth and refuse internal endpoints (#9441)

volume: require admin auth and refuse loopback endpoints in FetchAndWriteNeedle

Gate the RPC behind checkGrpcAdminAuth for parity with the rest of the
destructive volume-server RPCs, and reject cluster-internal remote S3
endpoints (loopback / link-local / IMDS / RFC 1918 / CGNAT) before
dialing. Pin the validated address against DNS rebinding by routing the
AWS SDK through an HTTP transport whose DialContext re-resolves the host
and re-applies the deny list on every dial, so an endpoint that resolves
to a public IP at validate-time and then flips to 127.0.0.1 at connect
time is refused. Operators that legitimately fetch from private hosts
can opt out with -volume.allowUntrustedRemoteEndpoints.

weed/command/server.go

@@ -155,6 +155,7 @@ func init() {
 
 	serverOptions.v.hasSlowRead = cmdServer.Flag.Bool("volume.hasSlowRead", true, "<experimental> if true, this prevents slow reads from blocking other requests, but large file read P99 latency will increase.")
 	serverOptions.v.readBufferSizeMB = cmdServer.Flag.Int("volume.readBufferSizeMB", 4, "<experimental> larger values can optimize query performance but will increase some memory usage,Use with hasSlowRead normally")
+	serverOptions.v.allowUntrustedRemoteEndpoints = cmdServer.Flag.Bool("volume.allowUntrustedRemoteEndpoints", false, "if true, FetchAndWriteNeedle accepts arbitrary remote S3 endpoints including loopback / link-local hosts. Default rejects internal / metadata endpoints.")
 
 	s3Options.port = cmdServer.Flag.Int("s3.port", 8333, "s3 server http listen port")
 	s3Options.portHttps = cmdServer.Flag.Int("s3.port.https", 0, "s3 server https listen port")