Add OS prng intended for use with getrandom()

Add the prng_os.c module, using the name previously occupied by what
is now prng_device.c.  Unlike prng_device.c, this PRNG module
maintains no file descriptor and just uses k5_os_random(), which is
most efficient on platforms which have a getrandom() system call.

[ghudson@mit.edu: expanded on commit message]

ticket: 8499

diff --git a/src/lib/crypto/krb/prng_os.c b/src/lib/crypto/krb/prng_os.c
new file mode 100644 (file)
index 0000000..8ea13e7
--- /dev/null
+++ b/src/lib/crypto/krb/prng_os.c
@@ -0,0 +1,72 @@
+/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
+/* lib/crypto/krb/prng_os.c - OS PRNG implementation */
+/*
+ * Copyright (C) 2016 by the Massachusetts Institute of Technology.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in
+ *   the documentation and/or other materials provided with the
+ *   distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * This file implements a PRNG module which relies on the system's PRNG.  An
+ * OS packager can select this module given sufficient confidence in the
+ * operating system's native PRNG quality.
+ */
+
+#include "crypto_int.h"
+
+int
+k5_prng_init(void)
+{
+    return 0;
+}
+
+void
+k5_prng_cleanup(void)
+{
+}
+
+krb5_error_code KRB5_CALLCONV
+krb5_c_random_add_entropy(krb5_context context, unsigned int randsource,
+                          const krb5_data *indata)
+{
+    return 0;
+}
+
+krb5_error_code KRB5_CALLCONV
+krb5_c_random_make_octets(krb5_context context, krb5_data *outdata)
+{
+    krb5_boolean res;
+
+    res = k5_get_os_entropy((uint8_t *)outdata->data, outdata->length, 0);
+    return res ? 0 : KRB5_CRYPTO_INTERNAL;
+}
+
+krb5_error_code KRB5_CALLCONV
+krb5_c_random_os_entropy(krb5_context context, int strong, int *success)
+{
+    return 0;
+}