1 files changed, 116 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/tls/TlsRSAUtils.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/tls/TlsRSAUtils.java
new file mode 100644
index 000000000..70ef035d7
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/tls/TlsRSAUtils.java
@@ -0,0 +1,116 @@
+package org.spongycastle.crypto.tls;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+import org.spongycastle.crypto.InvalidCipherTextException;
+import org.spongycastle.crypto.encodings.PKCS1Encoding;
+import org.spongycastle.crypto.engines.RSABlindedEngine;
+import org.spongycastle.crypto.params.ParametersWithRandom;
+import org.spongycastle.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 (TlsUtils.isSSL(context))
+            {
+                // 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;
+    }
+
+    public static byte[] safeDecryptPreMasterSecret(TlsContext context, TlsEncryptionCredentials encryptionCredentials,
+        byte[] encryptedPreMasterSecret)
+    {
+        /*
+         * RFC 5246 7.4.7.1.
+         */
+
+        ProtocolVersion clientVersion = context.getClientVersion();
+
+        // TODO Provide as configuration option?
+        boolean versionNumberCheckDisabled = false;
+
+        /*
+         * See notes regarding Bleichenbacher/Klima attack. The code here implements the first
+         * construction proposed there, which is RECOMMENDED.
+         */
+        byte[] R = new byte[48];
+        context.getSecureRandom().nextBytes(R);
+
+        byte[] M = TlsUtils.EMPTY_BYTES;
+        try
+        {
+            M = encryptionCredentials.decryptPreMasterSecret(encryptedPreMasterSecret);
+        }
+        catch (Exception e)
+        {
+            /*
+             * In any case, a TLS server MUST NOT generate an alert if processing an
+             * RSA-encrypted premaster secret message fails, or the version number is not as
+             * expected. Instead, it MUST continue the handshake with a randomly generated
+             * premaster secret.
+             */
+        }
+
+        if (M.length != 48)
+        {
+            TlsUtils.writeVersion(clientVersion, R, 0);
+            return R;
+        }
+
+        /*
+         * If ClientHello.client_version is TLS 1.1 or higher, server implementations MUST
+         * check the version number [..].
+         */
+        if (versionNumberCheckDisabled && clientVersion.isEqualOrEarlierVersionOf(ProtocolVersion.TLSv10))
+        {
+            /*
+             * If the version number is TLS 1.0 or earlier, server implementations SHOULD
+             * check the version number, but MAY have a configuration option to disable the
+             * check.
+             */
+        }
+        else
+        {
+            /*
+             * Note that explicitly constructing the pre_master_secret with the
+             * ClientHello.client_version produces an invalid master_secret if the client
+             * has sent the wrong version in the original pre_master_secret.
+             */
+            TlsUtils.writeVersion(clientVersion, M, 0);
+        }
+
+        return M;
+    }
+}