Android API Level < 24 ignore SSL Pinning

[josera21]

Describe the bug The SSL Pinning is not working on Android 6 Marshmallow but it works fine for Android N and above

To Reproduce

1. Initialized and config Truskit correctly
2. On the xml/network_security_config file, put some invalid certificates
3. Run the app on Android 6 and Android >= 7
4. The https request on Android => 7 are rejected correctly, but on Android 6 it work just tine.

Expected behavior The request with an invalid certificates should not work on both Android 6 and => 7.

TrustKit configuration network_security_config.xml

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
  <base-config cleartextTrafficPermitted="true">
    <trust-anchors>
      <certificates src="system"/>
      <certificates src="user" />
    </trust-anchors>
  </base-config>
  <!-- Pin the domain example.com-->
  <!-- Official Android N API -->
  <domain-config>
    <domain includeSubdomains="true">example.com</domain>
    <pin-set>
      <pin digest="SHA-256">JlgeWvslDDLd6LweqYxg4gANDQkZKDE7+ER3G/FP3BM=</pin>
      <pin digest="SHA-256">jQJTbIh0grw0/1TkHSumWb+Fs0Ggogr621gT3PvPKG0=</pin>
    </pin-set>
    <trustkit-config enforcePinning="true">
    </trustkit-config>
  </domain-config>
</network-security-config>

MainActivity.java

@Override
  protected void onCreate(Bundle savedInstanceState) {
    /* Start of certificate pinning */
    try {
      TrustKit.initializeWithNetworkSecurityConfiguration(this);
    } catch (Exception e) {
      e.printStackTrace();
    }

    // OkHttp 3.3.x and higher
    OkHttpClient client =
            new OkHttpClient.Builder()
                    .sslSocketFactory(OkHttp3Helper.getSSLSocketFactory(), OkHttp3Helper.getTrustManager())
                    .addInterceptor(OkHttp3Helper.getPinningInterceptor())
                    .followRedirects(false)
                    .followSslRedirects(false)
                    .build();
    /* End of certificate pinning */
    super.onCreate(savedInstanceState);
  }

App details:

• App target SDK: 30
• App language: React Native 0.66.3
• Android version to reproduce the bug Android 6 (Marshmallow)