DoNuT DoNuT - 1 year ago 129
Java Question

Java SSL Certificate Revocation Checking

I'm currently writing a network TCP server using SSL. In production, we'll finally require clients to authenticate with a certificate.

In order to revoke certificates in case of a emergency, we would also like to establish a CRL.

My question is: Does Java check CRLs (if provided with the certificate) out of the box or do I need to manually implement such checks?

For testing, I prepared a certificate with a CRL set but Java does not seem to try to validate it (I dropped it into a local web server and there's no access).

I only found the VM option, but apparently it doesn't query the CRL. VM debugging set to does not generate any output, either...

Java seems to have related classes in its subsystems (e.g., but it does not come into play, obviously.

I wrote a small maven-style project using Apache Mina as client server that initializes a SSLContext based on key/truststores and self-signed certificates for client/server which can be downloaded here as ZIP archive:

Answer Source

I figured how to enable CRL checking within a SSLContext without implementing a custom validator, as suggested in the comments.

It is mainly about properly initializing the SSLContext's TrustManagers with a revocation checker, only a few lines, no custom check logic and the CRL is now checked automatically as well as the verification path.

Here's a snippet...

KeyStore ts = KeyStore.getInstance("JKS");
FileInputStream tfis = new FileInputStream(trustStorePath);
ts.load(tfis, trustStorePass.toCharArray());

KeyManagerFactory kmf =  KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());

// initialize certification path checking for the offered certificates and revocation checks against CLRs
CertPathBuilder cpb = CertPathBuilder.getInstance("PKIX");
PKIXRevocationChecker rc = (PKIXRevocationChecker)cpb.getRevocationChecker();
    PKIXRevocationChecker.Option.PREFER_CRLS, // prefer CLR over OCSP
    PKIXRevocationChecker.Option.SOFT_FAIL, // handshake should not fail when CRL is not available
PKIXRevocationChecker.Option.NO_FALLBACK)); // don't fall back to OCSP checking

PKIXBuilderParameters pkixParams = new PKIXBuilderParameters(ts, new X509CertSelector());

tmf.init( new CertPathTrustManagerParameters(pkixParams) );
// init KeyManagerFactory

SSLContext ctx = SSLContext.getInstance("TLS");
ctx.init(kmf.getKeyManagers), tmf.getTrustManagers(), null);

That essentially did what I needed in my application, checking whether a certificate issued to a client is revoked in our CRL. Only checking the end entity and allowing the CRL check to fail is accepted because its all our infrastructure.

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