Functions to create an ECDH key exchange

Allows 2 users to securely obtain a shared key for usage with AES.

client/src/builtin/E2EE.js

@@ -13,6 +13,7 @@ import { WebpackModules, ReactComponents, MonkeyPatch, Patcher } from 'modules';
 import { VueInjector, Reflection } from 'ui';
 import E2EEComponent from './E2EEComponent.vue';
 import aes256 from 'aes256';
+import crypto from 'crypto';
 
 export default new class E2EE extends BuiltinModule {
 
@@ -36,6 +37,29 @@ export default new class E2EE extends BuiltinModule {
     handleSubmit(component, args, retVal) {
         component.props.value = aes256.encrypt('randomkey', component.props.value);
     }
+    
+    get ecdh() {
+        if (!this._ecdh) this._ecdh = {};
+        return this._ecdh;
+    }
+
+    createKeyExchange(userID) {
+        this.ecdh[userID] = crypto.createECDH('secp521r1');
+        return this.ecdh[userID].generateKeys('base64');
+    }
+
+    publicKeyFor(userID) {
+        return this.ecdh[userID].getPublicKey('base64');
+    }
+
+    computeSecret(userID, otherKey) {
+        const secret = this.ecdh[userID].computeSecret(otherKey, 'base64', 'base64');
+        delete this.ecdh[userID];
+        // Hashing the shared secret future-proofs against some possible attacks.
+        const hash = crypto.createHash('sha256');
+        hash.update(secret);
+        return hash.digest('base64');
+    }
 
     disabled(e) {
         for (const patch of Patcher.getPatchesByCaller('BD:E2EE')) patch.unpatch();