1 files changed, 52 insertions, 0 deletions
diff --git a/core/src/main/java/org/bouncycastle/crypto/tls/TlsRSAUtils.java b/core/src/main/java/org/bouncycastle/crypto/tls/TlsRSAUtils.java
new file mode 100644
index 00000000..f67e572f
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/crypto/tls/TlsRSAUtils.java
@@ -0,0 +1,52 @@
+package org.bouncycastle.crypto.tls;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+import org.bouncycastle.crypto.InvalidCipherTextException;
+import org.bouncycastle.crypto.encodings.PKCS1Encoding;
+import org.bouncycastle.crypto.engines.RSABlindedEngine;
+import org.bouncycastle.crypto.params.ParametersWithRandom;
+import org.bouncycastle.crypto.params.RSAKeyParameters;
+
+public class TlsRSAUtils
+{
+    public static byte[] generateEncryptedPreMasterSecret(TlsContext context, RSAKeyParameters rsaServerPublicKey,
+                                                          OutputStream output)
+        throws IOException
+    {
+        /*
+         * Choose a PremasterSecret and send it encrypted to the server
+         */
+        byte[] premasterSecret = new byte[48];
+        context.getSecureRandom().nextBytes(premasterSecret);
+        TlsUtils.writeVersion(context.getClientVersion(), premasterSecret, 0);
+
+        PKCS1Encoding encoding = new PKCS1Encoding(new RSABlindedEngine());
+        encoding.init(true, new ParametersWithRandom(rsaServerPublicKey, context.getSecureRandom()));
+
+        try
+        {
+            byte[] encryptedPreMasterSecret = encoding.processBlock(premasterSecret, 0, premasterSecret.length);
+
+            if (context.getServerVersion().isSSL())
+            {
+                // TODO Do any SSLv3 servers actually expect the length?
+                output.write(encryptedPreMasterSecret);
+            }
+            else
+            {
+                TlsUtils.writeOpaque16(encryptedPreMasterSecret, output);
+            }
+        }
+        catch (InvalidCipherTextException e)
+        {
+            /*
+             * This should never happen, only during decryption.
+             */
+            throw new TlsFatalAlert(AlertDescription.internal_error);
+        }
+
+        return premasterSecret;
+    }
+}