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>

1 files changed, 126 insertions, 0 deletions

diff --git a/crypto/rng.c b/crypto/rng.c
new file mode 100644
index 000000000000..6e94bc735578
--- /dev/null
+++ b/crypto/rng.c
@@ -0,0 +1,126 @@
+/*
+ * Cryptographic API.
+ *
+ * RNG operations.
+ *
+ * Copyright (c) 2008 Neil Horman <nhorman@tuxdriver.com>
+ *
+ * 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 option)
+ * any later version.
+ *
+ */
+
+#include <asm/atomic.h>
+#include <crypto/internal/rng.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/random.h>
+#include <linux/seq_file.h>
+#include <linux/string.h>
+
+static DEFINE_MUTEX(crypto_default_rng_lock);
+struct crypto_rng *crypto_default_rng;
+EXPORT_SYMBOL_GPL(crypto_default_rng);
+static int crypto_default_rng_refcnt;
+
+static int rngapi_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
+{
+        u8 *buf = NULL;
+        int err;
+
+        if (!seed && slen) {
+                buf = kmalloc(slen, GFP_KERNEL);
+                if (!buf)
+                        return -ENOMEM;
+
+                get_random_bytes(buf, slen);
+                seed = buf;
+        }
+
+        err = crypto_rng_alg(tfm)->rng_reset(tfm, seed, slen);
+
+        kfree(buf);
+        return err;
+}
+
+static int crypto_init_rng_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
+{
+        struct rng_alg *alg = &tfm->__crt_alg->cra_rng;
+        struct rng_tfm *ops = &tfm->crt_rng;
+
+        ops->rng_gen_random = alg->rng_make_random;
+        ops->rng_reset = rngapi_reset;
+
+        return 0;
+}
+
+static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
+        __attribute__ ((unused));
+static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
+{
+        seq_printf(m, "type         : rng\n");
+        seq_printf(m, "seedsize     : %u\n", alg->cra_rng.seedsize);
+}
+
+static unsigned int crypto_rng_ctxsize(struct crypto_alg *alg, u32 type,
+                                       u32 mask)
+{
+        return alg->cra_ctxsize;
+}
+
+const struct crypto_type crypto_rng_type = {
+        .ctxsize = crypto_rng_ctxsize,
+        .init = crypto_init_rng_ops,
+#ifdef CONFIG_PROC_FS
+        .show = crypto_rng_show,
+#endif
+};
+EXPORT_SYMBOL_GPL(crypto_rng_type);
+
+int crypto_get_default_rng(void)
+{
+        struct crypto_rng *rng;
+        int err;
+
+        mutex_lock(&crypto_default_rng_lock);
+        if (!crypto_default_rng) {
+                rng = crypto_alloc_rng("stdrng", 0, 0);
+                err = PTR_ERR(rng);
+                if (IS_ERR(rng))
+                        goto unlock;
+
+                err = crypto_rng_reset(rng, NULL, crypto_rng_seedsize(rng));
+                if (err) {
+                        crypto_free_rng(rng);
+                        goto unlock;
+                }
+
+                crypto_default_rng = rng;
+        }
+
+        crypto_default_rng_refcnt++;
+        err = 0;
+
+unlock:
+        mutex_unlock(&crypto_default_rng_lock);
+
+        return err;
+}
+EXPORT_SYMBOL_GPL(crypto_get_default_rng);
+
+void crypto_put_default_rng(void)
+{
+        mutex_lock(&crypto_default_rng_lock);
+        if (!--crypto_default_rng_refcnt) {
+                crypto_free_rng(crypto_default_rng);
+                crypto_default_rng = NULL;
+        }
+        mutex_unlock(&crypto_default_rng_lock);
+}
+EXPORT_SYMBOL_GPL(crypto_put_default_rng);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Random Number Genertor");