How to enable certificate pinning with OkHttp

Question

How can I enable certificate pinning using OkHttp for my Android / Java application?

Answer 1

The OkHttp documentation gives us a clear way to do this complete with sample code. In case it goes away, here it is pasted in below:

1. Add a broken CertificatePinner and make a request. Any request will do, even if it doesn't exist. You can do this in your Android application, or just create a dummy Java application and run this as well.

For example, to pin https://publicobject.com, start with a broken configuration:

String hostname = "publicobject.com";
CertificatePinner certificatePinner = new CertificatePinner.Builder()
    .add(hostname, "sha256/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=")
    .build();
OkHttpClient client = OkHttpClient.Builder()
    .certificatePinner(certificatePinner)
    .build();

Request request = new Request.Builder()
    .url("https://" + hostname)
    .build();
client.newCall(request).execute();

As expected, this fails with a certificate pinning exception:

javax.net.ssl.SSLPeerUnverifiedException: Certificate pinning failure!
   Peer certificate chain:
     sha256/afwiKY3RxoMmLkuRW1l7QsPZTJPwDS2pdDROQjXw8ig=: CN=publicobject.com, OU=PositiveSSL
     sha256/klO23nT2ehFDXCfx3eHTDRESMz3asj1muO+4aIdjiuY=: CN=COMODO RSA Secure Server CA
     sha256/grX4Ta9HpZx6tSHkmCrvpApTQGo67CYDnvprLg5yRME=: CN=COMODO RSA Certification Authority
     sha256/lCppFqbkrlJ3EcVFAkeip0+44VaoJUymbnOaEUk7tEU=: CN=AddTrust External CA Root
   Pinned certificates for publicobject.com:
     sha256/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
   at okhttp3.CertificatePinner.check(CertificatePinner.java)
   at okhttp3.Connection.upgradeToTls(Connection.java)
   at okhttp3.Connection.connect(Connection.java)
   at okhttp3.Connection.connectAndSetOwner(Connection.java)

2. Configure your OkHttp Client Correctly:

CertificatePinner certificatePinner = new CertificatePinner.Builder()
    .add("publicobject.com", "sha256/afwiKY3RxoMmLkuRW1l7QsPZTJPwDS2pdDROQjXw8ig=")
    .add("publicobject.com", "sha256/klO23nT2ehFDXCfx3eHTDRESMz3asj1muO+4aIdjiuY=")
    .add("publicobject.com", "sha256/grX4Ta9HpZx6tSHkmCrvpApTQGo67CYDnvprLg5yRME=")
    .add("publicobject.com", "sha256/lCppFqbkrlJ3EcVFAkeip0+44VaoJUymbnOaEUk7tEU=")
    .build();

That's all there is to it!

This method will give you all your certificates in the entire chain. This is advantageous since it's safer as only one certificate in the chain has to match for the request to succeed. It's likely at some point in the future, your certificates will be updated, but as long as the entire chain isn't updated, your application shouldn't break.