@reclaimprotocol/tls/lib/utils/parse-client-hello.js

WebCrypto Based Cross Platform TLS

import { SUPPORTED_RECORD_TYPE_MAP } from "./constants.js";
import { getTlsVersionFromBytes } from "./generics.js";
import { expectReadWithLength } from "./packets.js";
import { parseClientExtensions } from "./parse-extensions.js";
/**
 * Parse a full client hello message
 */
export function parseClientHello(data) {
    const packetType = read(1)[0];
    if (packetType !== SUPPORTED_RECORD_TYPE_MAP.CLIENT_HELLO) {
        throw new Error(`Invalid record type for client hello (${packetType})`);
    }
    data = readWLength(3);
    const versionBytes = read(2);
    const version = getTlsVersionFromBytes(versionBytes);
    const serverRandom = read(32);
    const sessionId = readWLength(1);
    const cipherSuitesBytes = readWLength(2);
    const compressionMethodByte = readWLength(1)[0];
    const extensions = parseClientExtensions(data);
    return {
        version,
        serverRandom,
        sessionId,
        cipherSuitesBytes,
        compressionMethodByte,
        extensions,
    };
    function read(bytes) {
        const result = data.slice(0, bytes);
        data = data.slice(bytes);
        return result;
    }
    function readWLength(bytesLength = 2) {
        const content = expectReadWithLength(data, bytesLength);
        data = data.slice(content.length + bytesLength);
        return content;
    }
}