Optionally use noise padding

syndicate/distributed/noise.rkt

@@ -29,7 +29,10 @@
   (for/list [(i (in-range 0 len chunk-size))]
     (subbytes bs i (min (+ i chunk-size) len))))
 
-(define (fragment bs [f values])
+(define (fragment bs0 padding [f values])
+  (define bs (if (zero? padding)
+                 bs0
+                 (bytes-append bs0 (make-bytes (modulo (- (bytes-length bs0)) padding) #x80))))
   (if (> (bytes-length bs) PACKET-LIMIT)
       (Packet-fragmented (map f (chunk-bytes bs PACKET-LIMIT)))
       (Packet-complete (f bs))))
@@ -39,13 +42,15 @@
                          #:acceptor-ref acceptor-ref
                          #:import import-handler
                          #:preshared-keys [psks #f]
-                         #:pattern [pattern #f])
+                         #:pattern [pattern #f]
+                         #:padding [padding 0])
   (noise* #:role 'initiator
           #:service-selector service-selector
           #:remote-static-pk remote-static-pk
           #:import import-handler
           #:preshared-keys psks
           #:pattern pattern
+          #:padding padding
           (lambda (set-peer-session! handle-message)
             (at acceptor-ref
               (assert (Resolve (Step (NoiseStepType) service-selector)
@@ -65,13 +70,15 @@
                          #:export initial-ref
                          #:observer observer
                          #:preshared-keys [psks #f]
-                         #:pattern [pattern #f])
+                         #:pattern [pattern #f]
+                         #:padding [padding 0])
   (noise* #:role 'responder
           #:service-selector service-selector
           #:static-keypair static-keypair
           #:export initial-ref
           #:preshared-keys psks
           #:pattern pattern
+          #:padding padding
           (lambda (set-peer-session! handle-message)
             (at observer
               (assert (Resolved-accepted
@@ -91,6 +98,7 @@
                 #:import [import-handler #f]
                 #:preshared-keys [psks #f]
                 #:pattern [pattern #f]
+                #:padding [padding 0]
                 f)
   (define H (Noise-*-25519_ChaChaPoly_BLAKE2s
              (or pattern "NK")
@@ -108,7 +116,7 @@
 
   (define (start-relay css)
     (set!-values (encrypt! decrypt!) (css->procedures css))
-    (run-relay #:packet-writer (lambda (bs) (send! peer-session (fragment bs encrypt!)))
+    (run-relay #:packet-writer (lambda (bs) (send! peer-session (fragment bs padding encrypt!)))
                #:setup-inputs (lambda (tr)
                                 (set! relay tr)
                                 (for [(m (in-list (reverse buffered-inputs-rev)))]

syndicate/relay.rkt

@@ -111,6 +111,8 @@
                  [(? eof-object?)
                   (when (positive? start-pos)
                     (set-tunnel-relay-read-buffer! tr (subbytes buffer start-pos)))]
+                 [#f
+                  (read-more)]
                  [packet
                   (accept-packet tr packet)
                   (read-more)]))))))