src/java.base/windows/native/libjava/WinCAPISeedGenerator.c

/*
 * Copyright (c) 2002, 2022, 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
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 */

#include <windows.h>
#include <wincrypt.h>
#include <jni.h>
#include "sun_security_provider_NativeSeedGenerator.h"

/*
 * Get a random seed from the MS CryptoAPI. Return true if successful, false
 * otherwise.
 *
 * Some early versions of Windows 95 do not support the required functions.
 * Use runtime linking to avoid problems.
 *
 */
JNIEXPORT jboolean JNICALL Java_sun_security_provider_NativeSeedGenerator_nativeGenerateSeed
  (JNIEnv *env, jclass clazz, jbyteArray randArray)
{
    HCRYPTPROV hCryptProv;
    jboolean result = JNI_FALSE;
    jsize numBytes;
    jbyte* randBytes;

    if (CryptAcquireContextA(&hCryptProv, "J2SE", NULL, PROV_RSA_FULL, 0) == FALSE) {
        /* If CSP context hasn't been created, create one. */
        if (CryptAcquireContextA(&hCryptProv, "J2SE", NULL, PROV_RSA_FULL,
                CRYPT_NEWKEYSET) == FALSE) {
            return result;
        }
    }

    numBytes = (*env)->GetArrayLength(env, randArray);
    randBytes = (*env)->GetByteArrayElements(env, randArray, NULL);
    if (randBytes == NULL) {
        goto cleanup;
    }

    if (CryptGenRandom(hCryptProv, numBytes, randBytes)) {
        result = JNI_TRUE;
    }
    (*env)->ReleaseByteArrayElements(env, randArray, randBytes, 0);

cleanup:
    CryptReleaseContext(hCryptProv, 0);

    return result;
}