gplazma: add public key size information to gPlazma results printer

Recent changes to JVMs have shown that key-size can be an importact
factor when understanding why a login has failed; specifically,
new JVMs now disallow certificates with RSA keys with less than 1024
bits.

This patch adds support for printing the number of bits in the public
key(s).  Unfortunately the interface (PublicKey) provides no mechanism
for discovering this information so we must down-cast to known
classes to discover the information.

Requires-notes: yes
Requires-book: no
Acked-by: Gerd Behrmann
Patch: http://rb.dcache.org/r/6274
Target: master
Request: 2.7
Request: 2.6
Request: 2.2

modules/gplazma2/src/main/java/org/dcache/gplazma/monitor/LoginResultPrinter.java

@@ -10,13 +10,15 @@
 import org.glite.voms.ac.AttributeCertificate;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import sun.security.rsa.RSAPublicKeyImpl;
 
 import javax.security.auth.x500.X500Principal;
 
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.security.Principal;
+import java.security.PublicKey;
 import java.security.cert.CertPath;
 import java.security.cert.CertificateParsingException;
 import java.security.cert.X509Certificate;
@@ -240,6 +242,7 @@ private String print(X509Certificate certificate)
         }
         sb.append("  +--Validity: ").append(validityStatementFor(certificate)).append('\n');
         sb.append("  +--Algorithm: ").append(nameForOid(certificate.getSigAlgOID())).append('\n');
+        sb.append("  +--Public key: ").append(describePublicKey(certificate.getPublicKey())).append('\n');
 
         String sanInfo = subjectAlternateNameInfoFor(certificate);
         if(!sanInfo.isEmpty()) {
@@ -285,6 +288,23 @@ private String print(X509Certificate certificate)
         return sb.toString();
     }
 
+    private static String describePublicKey(PublicKey key)
+    {
+        StringBuilder sb = new StringBuilder();
+
+        sb.append(key.getAlgorithm());
+
+        if (key instanceof RSAPublicKeyImpl) {
+            int bits = (((RSAPublicKeyImpl)key).getModulus().bitLength() + 7) & ~7;
+            sb.append(' ').append(bits).append(" bits");
+        } else {
+            sb.append(" (unknown ").append(key.getClass().getCanonicalName()).
+                    append(")");
+        }
+
+        return sb.toString();
+    }
+
     private static String subjectAlternateNameInfoFor(X509Certificate certificate)
     {
         StringBuilder sb = new StringBuilder();