Sign packets

static/js/modules/crypto/main.js

@@ -1,4 +1,4 @@
 import { generate_keypair } from "./paillier.js";
-import { generate_rsa_keypair } from "./rsa.js";
+import { generate_rsa_keypair, RsaPubKey } from "./rsa.js";
 
-export { generate_keypair, generate_rsa_keypair };
+export { generate_keypair, generate_rsa_keypair, RsaPubKey };

static/js/modules/crypto/rsa.js

@@ -3,18 +3,29 @@ import { mod_exp, mod_inv } from "./math.js";
 
 let p, q, pubKey, privKey;
 
-class PubKey {
-    constructor(p, q) {
-        this.n = p * q;
-        this.e = 65537n;
+export class RsaPubKey {
+    constructor(n, e) {
+        this.n = n;
+        this.e = e;
     }
 
     encrypt(m) {
         return mod_exp(m, this.e, this.n);
     }
+
+    toJSON() {
+        return {
+            n: "0x" + this.n.toString(16),
+            e: "0x" + this.e.toString(16),
+        };
     }
 
-class PrivKey {
+    static fromJSON(data) {
+        return new RsaPubKey(BigInt(data.n), BigInt(data.e));
+    }
+}
+
+class RsaPrivKey {
     constructor(p, q) {
         this.n = p * q;
         this.d = mod_inv(65537n, (q - 1n) * (p - 1n));
@@ -40,8 +51,8 @@ export function generate_rsa_keypair() {
         q = BigInt(window.sessionStorage.getItem("rsa_q"));
     }
 
-    pubKey = new PubKey(p, q);
-    privKey = new PrivKey(p, q);
+    pubKey = new RsaPubKey(p * q, 65537n);
+    privKey = new RsaPrivKey(p, q);
 
     return { pubKey, privKey };
 }

static/js/modules/interface/game.js

@@ -36,11 +36,11 @@ export class Game {
         return Object.values(this.players).filter((p) => p.isPlaying)[0];
     }
 
-    addPlayer(id, is_us) {
+    addPlayer(id, is_us, pubkey) {
         let is_new = this.players[id] === undefined;
 
         if (this.isWaiting()) {
-            this.players[id] = new Player(id, is_us);
+            this.players[id] = new Player(id, is_us, pubkey);
             if (is_us) {
                 this.us = this.players[id];
             }

static/js/modules/interface/main.js

@@ -26,14 +26,29 @@ document.addEventListener("DOMContentLoaded", () => {
     socket.on("connect", () => {
         window.console.log("Connected!");
         window.console.log(`We are: ${ID}`);
-        socket.emit("message", Packet.createAnnounce());
-        game.addPlayer(ID, true);
+        socket.emit("message", Packet.createAnnounce(window.rsa));
+        game.addPlayer(ID, true, window.rsa.pubKey);
     });
 
-    socket.on("message", async (data) => {
+    socket.on("message", async (packet) => {
+        let data = packet.payload;
         window.console.log(data);
 
-        // todo validate signature
+        const sender = game.players[data.author];
+        if (sender === undefined) {
+            window.console.warn(
+                `Not able to verify signature on packet ${data.id} as the sender is unknown.`
+            );
+        } else {
+            let sig = BigInt(packet.sig);
+            // decrypt and compare signature
+            let dehash = sender.rsaPubKey.encrypt(sig).toString(16);
+            let hash = CryptoJS.SHA3(JSON.stringify(data)).toString();
+            if (dehash !== hash) {
+                window.console.error(`Signature invalid! Ignoring packet ${data.id}.`);
+                return;
+            }
+        }
 
         switch (data.type) {
             case "RANDOM":
@@ -67,11 +82,11 @@ document.addEventListener("ANNOUNCE", (ev) => {
     const data = ev.detail;
     if (data.author === ID) return;
 
-    let is_new = game.addPlayer(data.author, false);
+    let is_new = game.addPlayer(data.author, false, data.rsaPubKey);
 
     // When a new player is seen, all announce to ensure they know all players.
     if (is_new) {
-        socket.emit("message", Packet.createAnnounce());
+        socket.emit("message", Packet.createAnnounce(window.rsa));
     }
 });
 

static/js/modules/interface/packet.js

@@ -9,30 +9,51 @@ export class Packet {
         };
     }
 
-    static createAnnounce() {
+    static _sign(data) {
+        // compute hash of data
+        let hash = CryptoJS.SHA3(JSON.stringify(data));
+        let res = 0n;
+        for (let word32 of hash.words) {
+            // remove any sign
+            let bi = BigInt.asUintN(32, BigInt(word32));
+            res = (res << 32n) | bi;
+        }
+
+        // sign hash
+        let sig = window.rsa.privKey.decrypt(res);
+
+        // return new packet
         return {
-            ...this._createBase("ANNOUNCE"),
+            sig: "0x" + sig.toString(16),
+            payload: data,
         };
     }
 
+    static createAnnounce(rsaKeyPair) {
+        return this._sign({
+            ...this._createBase("ANNOUNCE"),
+            rsaPubKey: rsaKeyPair.pubKey.toJSON(),
+        });
+    }
+
     static createDisconnect() {
-        return this._createBase("DISCONNECT");
+        return this._sign(this._createBase("DISCONNECT"));
     }
 
     static createKeepAlive() {
-        return this._createBase("KEEPALIVE");
+        return this._sign(this._createBase("KEEPALIVE"));
     }
 
     static createSetReady(nowReady) {
-        return {
+        return this._sign({
             ...this._createBase("ACT"),
             action: "READY",
             ready: nowReady,
-        };
+        });
     }
 
     static createBarrierSignal() {
-        return this._createBase("BARRIER");
+        return this._sign(this._createBase("BARRIER"));
     }
 
     static createRegionClaim(region) {
@@ -43,27 +64,27 @@ export class Packet {
     }
 
     static createAction(action, startRegion, endRegion, amount) {
-        return {
+        return this._sign({
             ...this._createBase("ACT"),
             startRegion: startRegion,
             endRegion: endRegion,
             strength: amount,
             action: action,
-        };
+        });
     }
 
     static createDefense(amount) {
-        return {
+        return this._sign({
             ...this._createBase("ACT"),
             action: "DEFENSE",
             amount: amount,
-        };
+        });
     }
 
     static createEndTurn() {
-        return {
+        return this._sign({
             ...this._createBase("ACT"),
             action: "END",
-        };
+        });
     }
 }

static/js/modules/interface/player.js

@@ -1,5 +1,6 @@
 import { Packet } from "./packet.js";
 import { socket } from "./main.js";
+import { RsaPubKey } from "../crypto/rsa.js";
 
 // Timeout to consider a player disconnected
 const TIMEOUT = 30_000;
@@ -11,10 +12,11 @@ const PHASE_FORTIFY = 3;
 let totalDice = 0;
 
 export class Player {
-    constructor(id, local) {
+    constructor(id, local, pubkey) {
         this.timeout = null;
         this.id = id;
         this.ready = false;
+        this.rsaPubKey = RsaPubKey.fromJSON(pubkey);
 
         // Data which is reset every turn
         this.isPlaying = false;