--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/sun/security/rsa/MGF1.java	Fri May 11 15:53:12 2018 -0700
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package sun.security.rsa;
+
+import java.security.*;
+
+/**
+ * This class implements the MGF1 mask generation function defined in PKCS#1
+ * v2.2 B.2.1. A mask generation function takes an octet string of variable
+ * length and a desired output length as input and outputs an octet string of
+ * the desired length. MGF1 is a mask generation function based on a hash
+ * function, i.e. message digest algorithm.
+ *
+ * @since   11
+ */
+public final class MGF1 {
+
+    private final MessageDigest md;
+
+    /**
+     * Construct an instance of MGF1 based on the specified digest algorithm.
+     */
+    MGF1(String mdAlgo) throws NoSuchAlgorithmException {
+        this.md = MessageDigest.getInstance(mdAlgo);
+    }
+
+    /**
+     * Using the specified seed bytes, generate the mask, xor the mask
+     * with the specified output buffer and store the result into the
+     * output buffer (essentially replaced in place).
+     *
+     * @param seed the buffer holding the seed bytes
+     * @param seedOfs the index of the seed bytes
+     * @param seedLen the length of the seed bytes to be used by MGF1
+     * @param maskLen the intended length of the generated mask
+     * @param out the output buffer holding the mask
+     * @param outOfs the index of the output buffer for the mask
+     */
+    void generateAndXor(byte[] seed, int seedOfs, int seedLen, int maskLen,
+            byte[] out, int outOfs) throws RuntimeException {
+        byte[] C = new byte[4]; // 32 bit counter
+        byte[] digest = new byte[md.getDigestLength()];
+        while (maskLen > 0) {
+            md.update(seed, seedOfs, seedLen);
+            md.update(C);
+            try {
+                md.digest(digest, 0, digest.length);
+            } catch (DigestException e) {
+                // should never happen
+                throw new RuntimeException(e.toString());
+            }
+            for (int i = 0; (i < digest.length) && (maskLen > 0); maskLen--) {
+                out[outOfs++] ^= digest[i++];
+            }
+            if (maskLen > 0) {
+                // increment counter
+                for (int i = C.length - 1; (++C[i] == 0) && (i > 0); i--) {
+                    // empty
+                }
+            }
+        }
+    }
+
+    /**
+     * Returns the name of this MGF1 instance, i.e. "MGF1" followed by the
+     * digest algorithm it based on.
+     */
+    String getName() {
+        return "MGF1" + md.getAlgorithm();
+    }
+}