Using the JarSigner with RSASSA-PSS

Question

Im trying to RSA-PSS-sign a JAR file with the JarSigner using PKCS#11. To specify the signature algorithm the JarSigner uses the sigalg flag. The JDK 14 Docs of the JarSigner does not specify which sigalgs are explicitly supported. I have tested that the JarSigner accepts "RSASSA-PSS" as a valid algorithm. The JarSigner does not accept "SHA256withRSASSA-PSS" or similar RSASSA-PSS variants that Java Crypto Service Providers, such as the SunPKCS11 Crypto Service Provider, often support. When trying to sign with the sigalg "RSASSA-PSS" the JarSigner returns

jarsigner: unable to sign jar: java.security.SignatureException: Parameters required for RSASSA-PSS signature

This exception means that the PSS parameters are not set. I have traced the problem down to the JarSigner

• not having any way to pass PSS parameters through the command line (see JDK 14 Docs of the JarSigner)
• never setting PSS parameters - the JarSigner.java never directly (see line 831 to 843) or indirectly (see Signature.java and P11PSSSignature.java) calls setParameter->setEngineParameter->setSigParams, which is responsible for setting the required PSS params.

Am I missing something? If yes, how can I RSA-PSS-sign a JAR file? If no, is this a bug? After all, the JarSigner clearly accepts RSASSA-PSS as a valid sigalg. Or is this rather an incompatibility between the JarSigner and the SunPKCS11 implementation? After all, SunPKCS11 could just be using hardcoded PSS param values in such a case.

Answer 1

It looks like this is not supported yet. I can reproduce this behaviour both with the jarsigner command line tool and with Java code like this:

import jdk.security.jarsigner.JarSigner;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.*;
import java.security.cert.CertPath;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.util.Arrays;
import java.util.zip.ZipFile;

class JarSignerDemo {
  public static void main(String[] args) throws IOException, CertificateException, NoSuchAlgorithmException, KeyStoreException, UnrecoverableKeyException {
    char[] password = "changeit".toCharArray();
    KeyStore keyStore = KeyStore.getInstance(new File("keystore.jks"), password);
    PrivateKey privateKey = (PrivateKey) keyStore.getKey("mykey", password);
    CertPath certPath = CertificateFactory.getInstance("X.509").generateCertPath(Arrays.asList(keyStore.getCertificateChain("mykey")));
    JarSigner jarSigner = new JarSigner.Builder(privateKey, certPath)
      .digestAlgorithm("SHA-256")
      .signatureAlgorithm("RSASSA-PSS")
      .build();
    try (
      ZipFile jarFile = new ZipFile("my.jar");
      FileOutputStream signedJarFile = new FileOutputStream("my-signed.jar")
    )
    {
      jarSigner.sign(jarFile, signedJarFile);
    }
  }
}

Exception in thread "main" jdk.security.jarsigner.JarSignerException: Error creating signature
    at jdk.jartool/jdk.security.jarsigner.JarSigner.sign(JarSigner.java:573)
    at JarSignerDemo.main(scratch_3.java:28)
Caused by: java.security.SignatureException: Parameters required for RSASSA-PSS signatures
    at java.base/sun.security.rsa.RSAPSSSignature.ensureInit(RSAPSSSignature.java:295)
    at java.base/sun.security.rsa.RSAPSSSignature.engineUpdate(RSAPSSSignature.java:346)
    at java.base/java.security.Signature$Delegate.engineUpdate(Signature.java:1393)
    at java.base/java.security.Signature.update(Signature.java:902)
    at java.base/java.security.Signature.update(Signature.java:871)
    at jdk.jartool/jdk.security.jarsigner.JarSigner.sign0(JarSigner.java:841)
    at jdk.jartool/jdk.security.jarsigner.JarSigner.sign(JarSigner.java:562)
    ... 1 more

It looks like JDK-8245274 is meant to add this feature to Java 16. I am not 100% sure, but it looks like your issue. You may want to watch it.

---

Update: Slightly off-topic, but it looks like you can sign with RSASSA-PSS using BouncyCastle. I am not sure if that is an alternative for you, though. Maybe you just want to switch to another key type.