import okhttp3.CertificatePinner;
import okhttp3.Interceptor;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public final class CheckHandshake {
  /** Rejects otherwise-trusted certificates. */
  private static final Interceptor CHECK_HANDSHAKE_INTERCEPTOR = new Interceptor() {
    final Set<String> denylist = Collections.singleton(
        "sha256/afwiKY3RxoMmLkuRW1l7QsPZTJPwDS2pdDROQjXw8ig=");

    sslContext.init(null, new TrustManager[] { trustManager }, null);

    return sslContext.getSocketFactory();
  }

  /** Returns a trust manager that trusts the VM's default certificate authorities. */
  private X509TrustManager defaultTrustManager() throws GeneralSecurityException {
    TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(
        TrustManagerFactory.getDefaultAlgorithm());

  ) {
    enum class Type {
      Handshake,
      Plaintext,
      Encrypted,
      Setup,
      Unknown,
    }

    val type: Type
      get() =
        when {
          message == "adding as trusted certificates" -> Type.Setup
          message == "Raw read" || message == "Raw write" -> Type.Encrypted
          message == "Plaintext before ENCRYPTION" || message == "Plaintext after DECRYPTION" -> Type.Plaintext

Use [CertificatePinner](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-certificate-pinner/) to restrict which certificates and certificate authorities are trusted. Certificate pinning increases security, but limits your server team’s abilities to update their TLS certificates. **Do not use certificate pinning without the blessing of your server’s TLS administrator!**

    } else {
      Log.i(Tag, message, t)
    }
  }

  /**
   * A trust manager for Android applications that customize the trust manager.
   *
   * This class exploits knowledge of Android implementation details. This class is potentially
   * much faster to initialize than [BasicTrustRootIndex] because it doesn't need to load and
   * index trusted CA certificates.
   */
  internal data class CustomTrustRootIndex(

 * [okhttp-stats](https://github.com/flipkart-incubator/okhttp-stats): Get stats like average network speed.
 * [okhttp-system-keystore](https://github.com/charleskorn/okhttp-system-keystore): Use trusted certificates from the operating system keystore (Keychain on macOS, Certificate Store on Windows).
 * ⬜️ [Okio](https://github.com/square/okio/): A modern I/O API for Java.

import okhttp3.internal.toCanonicalHost
import okio.ByteString
import okio.ByteString.Companion.decodeBase64
import okio.ByteString.Companion.toByteString

/**
 * Constrains which certificates are trusted. Pinning certificates defends against attacks on
 * certificate authorities. It also prevents connections through man-in-the-middle certificate
 * authorities either known or unknown to the application's user.

          // Consuming ServerHello handshake message
          // Consuming server Certificate handshake message
          // Consuming server CertificateStatus handshake message
          // Found trusted certificate
          // Consuming ECDH ServerKeyExchange handshake message
          // Consuming ServerHelloDone handshake message
          // Produced ECDHE ClientKeyExchange handshake message

  /**
   * Configure the server to [want client auth][SSLSocket.setWantClientAuth]. If the
   * client presents a certificate that is [trusted][TrustManager] the handshake will
   * proceed normally. The connection will also proceed normally if the client presents no
   * certificate at all! But if the client presents an untrusted certificate the handshake
   * will fail and no connection will be established.
   */
  public fun requestClientAuth() {

    Regex(
      buildString {
        append("^(?:")
        append(
          listOf(
            "Inaccessible trust store",
            "trustStore is",
            "Reload the trust store",
            "Reload trust certs",
            "Reloaded",
            "adding as trusted certificates",
            "Ignore disabled cipher suite",
            "Ignore unsupported cipher suite",