finalize multi-device

WASignalGroup/sender_key_message.js

@@ -0,0 +1,92 @@
+const CiphertextMessage = require('./ciphertext_message');
+const curve = require('libsignal/src/curve');
+const protobufs = require('./protobufs');
+
+class SenderKeyMessage extends CiphertextMessage {
+  SIGNATURE_LENGTH = 64;
+
+  constructor(
+    keyId = null,
+    iteration = null,
+    ciphertext = null,
+    signatureKey = null,
+    serialized = null
+  ) {
+    super();
+    if (serialized) {
+      const version = serialized[0];
+      const message = serialized.slice(1, serialized.length - this.SIGNATURE_LENGTH);
+      const signature = serialized.slice(-1 * this.SIGNATURE_LENGTH);
+      const senderKeyMessage = protobufs.SenderKeyMessage.decode(message).toJSON();
+      senderKeyMessage.ciphertext = Buffer.from(senderKeyMessage.ciphertext, 'base64');
+
+      this.serialized = serialized;
+      this.messageVersion = (version & 0xff) >> 4;
+
+      this.keyId = senderKeyMessage.id;
+      this.iteration = senderKeyMessage.iteration;
+      this.ciphertext = senderKeyMessage.ciphertext;
+      this.signature = signature;
+    } else {
+      const version = (((this.CURRENT_VERSION << 4) | this.CURRENT_VERSION) & 0xff) % 256;
+      ciphertext = Buffer.from(ciphertext); // .toString('base64');
+      const message = protobufs.SenderKeyMessage.encode(
+        protobufs.SenderKeyMessage.create({
+          id: keyId,
+          iteration,
+          ciphertext,
+        })
+      ).finish();
+
+      const signature = this.getSignature(
+        signatureKey,
+        Buffer.concat([Buffer.from([version]), message])
+      );
+      this.serialized = Buffer.concat([Buffer.from([version]), message, Buffer.from(signature)]);
+      this.messageVersion = this.CURRENT_VERSION;
+      this.keyId = keyId;
+      this.iteration = iteration;
+      this.ciphertext = ciphertext;
+      this.signature = signature;
+    }
+  }
+
+  getKeyId() {
+    return this.keyId;
+  }
+
+  getIteration() {
+    return this.iteration;
+  }
+
+  getCipherText() {
+    return this.ciphertext;
+  }
+
+  verifySignature(signatureKey) {
+    const part1 = this.serialized.slice(0, this.serialized.length - this.SIGNATURE_LENGTH + 1);
+    const part2 = this.serialized.slice(-1 * this.SIGNATURE_LENGTH);
+    const res = curve.verifySignature(signatureKey, part1, part2);
+    if (!res) throw new Error('Invalid signature!');
+  }
+
+  getSignature(signatureKey, serialized) {
+    const signature = Buffer.from(
+      curve.calculateSignature(
+        signatureKey,
+        serialized
+      )
+    );
+    return signature;
+  }
+
+  serialize() {
+    return this.serialized;
+  }
+
+  getType() {
+    return 4;
+  }
+}
+
+module.exports = SenderKeyMessage;