naruyaizumi/lib/Signal/Group/sender-key-message.js

A WebSockets library for interacting with WhatsApp Web

import { calculateSignature, verifySignature } from "libsignal/src/curve.js";
import { proto } from "../../../WAProto/index.js";
import { CiphertextMessage } from "./ciphertext-message.js";
export class SenderKeyMessage extends CiphertextMessage {
    constructor(keyId, iteration, ciphertext, signatureKey, serialized) {
        super();
        this.SIGNATURE_LENGTH = 64;
        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 = proto.SenderKeyMessage.decode(message).toJSON();
            this.serialized = serialized;
            this.messageVersion = (version & 0xff) >> 4;
            this.keyId = senderKeyMessage.id;
            this.iteration = senderKeyMessage.iteration;
            this.ciphertext =
                typeof senderKeyMessage.ciphertext === "string"
                    ? Buffer.from(senderKeyMessage.ciphertext, "base64")
                    : senderKeyMessage.ciphertext;
            this.signature = signature;
        } else {
            const version = (((this.CURRENT_VERSION << 4) | this.CURRENT_VERSION) & 0xff) % 256;
            const ciphertextBuffer = Buffer.from(ciphertext);
            const message = proto.SenderKeyMessage.encode(
                proto.SenderKeyMessage.create({
                    id: keyId,
                    iteration: iteration,
                    ciphertext: ciphertextBuffer,
                })
            ).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 = ciphertextBuffer;
            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);
        const part2 = this.serialized.slice(-1 * this.SIGNATURE_LENGTH);
        const res = verifySignature(signatureKey, part1, part2);
        if (!res) throw new Error("Invalid signature!");
    }
    getSignature(signatureKey, serialized) {
        return Buffer.from(calculateSignature(signatureKey, serialized));
    }
    serialize() {
        return this.serialized;
    }
    getType() {
        return 4;
    }
}
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