From c7ea1cc2acd93c8e56eee463b52e1be826c5d100 Mon Sep 17 00:00:00 2001
From: Kenta Iwasaki <kenta@lithdew.net>
Date: Sat, 13 Jun 2020 04:23:02 +0900
Subject: [PATCH] sdk/js: do not allow for backtracking upon backpressure in
 monte socket

---
 ts/monte.js | 55 +++++++++++++++++++++++++++--------------------------
 1 file changed, 28 insertions(+), 27 deletions(-)

diff --git a/ts/monte.js b/ts/monte.js
index aace08b..4ea4623 100644
--- a/ts/monte.js
+++ b/ts/monte.js
@@ -56,6 +56,7 @@ class MonteSocket extends Duplex {
         this.counter = 0;
 
         this._paused = false;
+        this._state = 0;
 
         this.conn.on('close', had_error => this.emit('close', had_error));
         this.conn.on('connect', () => this.emit('connect'));
@@ -196,37 +197,37 @@ class MonteSocket extends Duplex {
 
     _readable() {
         while (!this._paused) {
-            const header = this.conn.read(4);
-            if (!header) return;
-
-            const length = header.readUInt32BE();
-
-            let frame = this.conn.read(length);
-            if (!frame) {
-                console.log(`Trying to read ${length} byte(s), only ${this.conn.readableLength} byte(s) available.`)
-                this.conn.unshift(header);
-                return;
-            }
-
-            frame = this.decrypt(frame);
-            if (frame.byteLength <= 4) {
-                this.conn.destroy(new Error(`Packet is too small: no sequence number field found in packet.`));
-                return;
-            }
+            if (this._state === 0) {
+                const header = this.conn.read(4);
+                if (!header) return;
+
+                this._length = header.readUInt32BE();
+                this._state = 1;
+            } else if (this._state === 1) {
+                let frame = this.conn.read(this._length);
+                if (!frame) return;
+
+                frame = this.decrypt(frame);
+                if (frame.byteLength <= 4) {
+                    this.conn.destroy(new Error(`Packet is too small: no sequence number field found in packet.`));
+                    return;
+                }
 
-            const seq = frame.readUInt32BE();
-            frame = frame.slice(4);
+                const seq = frame.readUInt32BE();
+                frame = frame.slice(4);
 
-            if (seq === 0 || this.pending.listenerCount(`${seq}`) === 0) {
-                try {
-                    if (!this.push({seq, frame})) {
-                        this._paused = true;
+                if (seq === 0 || this.pending.listenerCount(`${seq}`) === 0) {
+                    try {
+                        if (!this.push({seq, frame})) {
+                            this._paused = true;
+                        }
+                    } catch (err) {
+                        this.emit("error", err);
                     }
-                } catch (err) {
-                    this.emit("error", err);
+                } else {
+                    this.pending.emit(`${seq}`, frame);
                 }
-            } else {
-                this.pending.emit(`${seq}`, frame);
+                this._state = 0;
             }
         }
     }