Truncate outgoing lines to 512 bytes; safe UTF-8 input handling

Outgoing: cap line at 512 bytes including CRLF, never split a multi-byte
UTF-8 character; 510-byte payload limit + truncate-utf8-bytes helper.

Incoming: read via InputStreamReader (UTF-8) so byte-per-byte input
doesn't decode partial multi-byte sequences as U+FFFD.

1 files changed, 35 insertions, 5 deletions

diff --git a/src/papod.clj b/src/papod.clj
index 6e53997..5e81533 100644
--- a/src/papod.clj
+++ b/src/papod.clj
@@ -848,11 +848,39 @@
                     [?m :papod.memo/read? false]]}
           (d/db conn) nick))))
 
+(defn- truncate-utf8-bytes
+  ^bytes [^bytes bytes max-len]
+  (let [n (alength bytes)]
+    (if (<= n max-len)
+      bytes
+      (loop [i 0]
+        (if (>= i n)
+          bytes
+          (let [b   (bit-and (aget bytes i) 0xff)
+                len (cond
+                      (zero? (bit-and b 0x80))   1
+                      (= (bit-and b 0xe0) 0xc0)  2
+                      (= (bit-and b 0xf0) 0xe0)  3
+                      (= (bit-and b 0xf8) 0xf0)  4
+                      :else                      1)
+                end (+ i len)]
+            (if (or (> end n) (> end max-len))
+              (java.util.Arrays/copyOfRange bytes 0 i)
+              (recur end))))))))
+
 (defn- deliver-to-client!
   [w line]
   (try
-    (let [bytes (.getBytes (str line +delimiter+) +charset+)]
-      (.write w bytes 0 (count bytes))
+    (let [body  (.getBytes (str line) +charset+)
+          delim (.getBytes +delimiter+ +charset+)
+          body' (truncate-utf8-bytes body
+                  (- 512 (alength delim)))
+          out   (byte-array (+ (alength body')
+                               (alength delim)))]
+      (System/arraycopy body' 0 out 0 (alength body'))
+      (System/arraycopy delim 0 out (alength body')
+        (alength delim))
+      (.write w out 0 (alength out))
       (.flush w))
     (catch Exception _)))
 
@@ -3824,9 +3852,11 @@
                     (when s
                       (.setSoTimeout s (int +idle-timeout-ms+))))
                   (catch Exception _))
-        r       (java.nio.channels.Channels/newInputStream socket)
+        r       (java.io.InputStreamReader.
+                  (java.nio.channels.Channels/newInputStream socket)
+                  +charset+)
         w       (java.nio.channels.Channels/newOutputStream socket)
-        b       (make-array Byte/TYPE +buffer-size+)
+        b       (char-array +buffer-size+)
         conn-id (java.util.UUID/randomUUID)
         client  (atom {:nick nil :user nil :pass nil :registered? false
                         :w w :connection-id conn-id
@@ -3844,7 +3874,7 @@
         (let [n (.read r b)]
           (when (pos? n)
             (let [new-acc (process-input!
-                           (str acc (String. b 0 n +charset+))
+                           (str acc (String. b 0 n))
                            w client components)]
               (when-not (:quit? @client)
                 (recur new-acc))))))