static _read()

in src/messages.js [257:282]

• 21 lines of code
• 6 McCabe index (conditional complexity)

  static _read(buf) {
    // Fixed value for legacy_version.
    if (buf.readUint16() !== VERSION_TLS_1_2) {
      throw new TLSError(ALERT_DESCRIPTION.ILLEGAL_PARAMETER);
    }
    // Random bytes from the server.
    const random = buf.readBytes(32);
    // It should have echoed our vector for legacy_session_id.
    const sessionId = buf.readVectorBytes8();
    // It should have selected our single offered ciphersuite.
    if (buf.readUint16() !== TLS_AES_128_GCM_SHA256) {
      throw new TLSError(ALERT_DESCRIPTION.ILLEGAL_PARAMETER);
    }
    // legacy_compression_method must be zero.
    if (buf.readUint8() !== 0) {
      throw new TLSError(ALERT_DESCRIPTION.ILLEGAL_PARAMETER);
    }
    const extensions = this._readExtensions(HANDSHAKE_TYPE.SERVER_HELLO, buf);
    if (! extensions.has(EXTENSION_TYPE.SUPPORTED_VERSIONS)) {
      throw new TLSError(ALERT_DESCRIPTION.MISSING_EXTENSION);
    }
    if (extensions.get(EXTENSION_TYPE.SUPPORTED_VERSIONS).selectedVersion !== VERSION_TLS_1_3) {
      throw new TLSError(ALERT_DESCRIPTION.ILLEGAL_PARAMETER);
    }
    return new this(random, sessionId, extensions);
  }