crypto: rng - RNG interface and implementation

This patch adds a random number generator interface as well as a
cryptographic pseudo-random number generator based on AES.  It is
meant to be used in cases where a deterministic CPRNG is required.

One of the first applications will be as an input in the IPsec IV
generation process.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/krng.c

@@ -0,0 +1,66 @@
+/*
+ * RNG implementation using standard kernel RNG.
+ *
+ * Copyright (c) 2008 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * any later version.
+ *
+ */
+
+#include <crypto/internal/rng.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/random.h>
+
+static int krng_get_random(struct crypto_rng *tfm, u8 *rdata, unsigned int dlen)
+{
+	get_random_bytes(rdata, dlen);
+	return 0;
+}
+
+static int krng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
+{
+	return 0;
+}
+
+static struct crypto_alg krng_alg = {
+	.cra_name		= "stdrng",
+	.cra_driver_name	= "krng",
+	.cra_priority		= 200,
+	.cra_flags		= CRYPTO_ALG_TYPE_RNG,
+	.cra_ctxsize		= 0,
+	.cra_type		= &crypto_rng_type,
+	.cra_module		= THIS_MODULE,
+	.cra_list		= LIST_HEAD_INIT(krng_alg.cra_list),
+	.cra_u			= {
+		.rng = {
+			.rng_make_random	= krng_get_random,
+			.rng_reset		= krng_reset,
+			.seedsize		= 0,
+		}
+	}
+};
+
+
+/* Module initalization */
+static int __init krng_mod_init(void)
+{
+	return crypto_register_alg(&krng_alg);
+}
+
+static void __exit krng_mod_fini(void)
+{
+	crypto_unregister_alg(&krng_alg);
+	return;
+}
+
+module_init(krng_mod_init);
+module_exit(krng_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Kernel Random Number Generator");
+MODULE_ALIAS("stdrng");