fix(shadowsocks): treat frame-boundary EOF as clean end; accept empty AEAD chunks like canon

app/src/main/java/chat/vojo/proxy/core/crypto/ShadowsocksStream.kt

@@ -1,9 +1,9 @@
 package chat.vojo.proxy.core.crypto
 
 import chat.vojo.proxy.core.net.readExact
+import chat.vojo.proxy.core.net.readFully
 import chat.vojo.proxy.core.net.u16be
 import java.io.ByteArrayOutputStream
-import java.io.EOFException
 import java.io.IOException
 import java.io.InputStream
 import java.io.OutputStream
@@ -74,27 +74,40 @@ class SsInputStream(
     private var plainPos = 0
 
     private fun fill(): Boolean {
-        try {
+        if (subkey == null) {
-            if (subkey == null) {
+            // Clean EOF before any salt = the peer closed without sending anything.
-                val salt = inp.readExact(aead.saltSize)
+            val first = inp.read()
-                subkey = ShadowsocksCrypto.sessionSubkey(masterKey, salt, aead.keySize)
+            if (first < 0) return false
-            }
+            val salt = ByteArray(aead.saltSize)
-            val key = subkey!!
+            salt[0] = first.toByte()
-            val encLen = inp.readExact(2 + aead.tagSize)
+            inp.readFully(salt, 1, salt.size - 1)
-            val lenPlain = aead.open(key, nonce, encLen)
+            subkey = ShadowsocksCrypto.sessionSubkey(masterKey, salt, aead.keySize)
-            ShadowsocksCrypto.incrementNonce(nonce)
-            val payloadLen = u16be(lenPlain[0].toInt(), lenPlain[1].toInt())
-            if (payloadLen <= 0 || payloadLen > MAX_PAYLOAD) {
-                throw IOException("invalid shadowsocks chunk length $payloadLen")
-            }
-            val encPayload = inp.readExact(payloadLen + aead.tagSize)
-            plain = aead.open(key, nonce, encPayload)
-            ShadowsocksCrypto.incrementNonce(nonce)
-            plainPos = 0
-            return true
-        } catch (e: EOFException) {
-            return false
         }
+        val key = subkey!!
+        // EOF *at a frame boundary* is a clean end of stream (-1). EOF *inside* a
+        // frame is truncation: once we've consumed any byte of the length header the
+        // payload must follow, so a short read there throws EOFException and propagates
+        // as an error — the relay then full-closes instead of signalling "complete".
+        val firstLen = inp.read()
+        if (firstLen < 0) return false
+        val encLen = ByteArray(2 + aead.tagSize)
+        encLen[0] = firstLen.toByte()
+        inp.readFully(encLen, 1, encLen.size - 1)
+        val lenPlain = aead.open(key, nonce, encLen)
+        ShadowsocksCrypto.incrementNonce(nonce)
+        val payloadLen = u16be(lenPlain[0].toInt(), lenPlain[1].toInt())
+        // Accept payloadLen == 0 (a tag-only keep-alive / empty frame): shadowsocks-rust and
+        // sing-shadowsocks both accept it, so rejecting it would desync against a compliant
+        // peer. An empty record opens to an empty payload and read() simply fills the next
+        // frame. Only an over-MAX length is a real protocol violation.
+        if (payloadLen > MAX_PAYLOAD) {
+            throw IOException("invalid shadowsocks chunk length $payloadLen")
+        }
+        val encPayload = inp.readExact(payloadLen + aead.tagSize)
+        plain = aead.open(key, nonce, encPayload)
+        ShadowsocksCrypto.incrementNonce(nonce)
+        plainPos = 0
+        return true
     }
 
     @Synchronized

app/src/main/java/chat/vojo/proxy/core/upstream/ShadowsocksUpstream.kt

@@ -53,7 +53,9 @@ private class ShadowsocksUdpAssociation(
 ) : UdpAssociation {
 
     private val server = InetSocketAddress(InetAddress.getByName(cfg.host), cfg.port)
-    private val udp = DatagramSocket().also { protector.protect(it) }
+    // Pinned to the SS server so the kernel drops datagrams from any other source.
+    // (AEAD already authenticates each datagram; this just sheds spoofed noise early.)
+    private val udp = DatagramSocket().also { protector.protect(it); runCatching { it.connect(server) } }
 
     override fun send(dest: Destination, data: ByteArray, off: Int, len: Int) {
         val plain = ByteArray(dest.raw.size + len)