linux/crypto/jitterentropy-kcapi.c

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/*
* Non-physical true random number generator based on timing jitter --
* Linux Kernel Crypto API specific code
*
* Copyright Stephan Mueller <smueller@chronox.de>, 2015
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, and the entire permission notice in its entirety,
* including the disclaimer of warranties.
* 2. 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.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* ALTERNATIVELY, this product may be distributed under the terms of
* the GNU General Public License, in which case the provisions of the GPL2 are
* required INSTEAD OF the above restrictions. (This clause is
* necessary due to a potential bad interaction between the GPL and
* the restrictions contained in a BSD-style copyright.)
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
* WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR 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 NOT ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/fips.h>
#include <linux/time.h>
#include <crypto/internal/rng.h>
#include "jitterentropy.h"
/***************************************************************************
* Helper function
***************************************************************************/
void *jent_zalloc(unsigned int len)
{
return kzalloc(len, GFP_KERNEL);
}
void jent_zfree(void *ptr)
{
mm, treewide: rename kzfree() to kfree_sensitive() As said by Linus: A symmetric naming is only helpful if it implies symmetries in use. Otherwise it's actively misleading. In "kzalloc()", the z is meaningful and an important part of what the caller wants. In "kzfree()", the z is actively detrimental, because maybe in the future we really _might_ want to use that "memfill(0xdeadbeef)" or something. The "zero" part of the interface isn't even _relevant_. The main reason that kzfree() exists is to clear sensitive information that should not be leaked to other future users of the same memory objects. Rename kzfree() to kfree_sensitive() to follow the example of the recently added kvfree_sensitive() and make the intention of the API more explicit. In addition, memzero_explicit() is used to clear the memory to make sure that it won't get optimized away by the compiler. The renaming is done by using the command sequence: git grep -w --name-only kzfree |\ xargs sed -i 's/kzfree/kfree_sensitive/' followed by some editing of the kfree_sensitive() kerneldoc and adding a kzfree backward compatibility macro in slab.h. [akpm@linux-foundation.org: fs/crypto/inline_crypt.c needs linux/slab.h] [akpm@linux-foundation.org: fix fs/crypto/inline_crypt.c some more] Suggested-by: Joe Perches <joe@perches.com> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: David Howells <dhowells@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Cc: James Morris <jmorris@namei.org> Cc: "Serge E. Hallyn" <serge@hallyn.com> Cc: Joe Perches <joe@perches.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: David Rientjes <rientjes@google.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: "Jason A . Donenfeld" <Jason@zx2c4.com> Link: http://lkml.kernel.org/r/20200616154311.12314-3-longman@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-07 06:18:13 +00:00
kfree_sensitive(ptr);
}
int jent_fips_enabled(void)
{
return fips_enabled;
}
void jent_panic(char *s)
{
panic("%s", s);
}
void jent_memcpy(void *dest, const void *src, unsigned int n)
{
memcpy(dest, src, n);
}
/*
* Obtain a high-resolution time stamp value. The time stamp is used to measure
* the execution time of a given code path and its variations. Hence, the time
* stamp must have a sufficiently high resolution.
*
* Note, if the function returns zero because a given architecture does not
* implement a high-resolution time stamp, the RNG code's runtime test
* will detect it and will not produce output.
*/
void jent_get_nstime(__u64 *out)
{
__u64 tmp = 0;
tmp = random_get_entropy();
/*
* If random_get_entropy does not return a value, i.e. it is not
* implemented for a given architecture, use a clock source.
* hoping that there are timers we can work with.
*/
if (tmp == 0)
tmp = ktime_get_ns();
*out = tmp;
}
/***************************************************************************
* Kernel crypto API interface
***************************************************************************/
struct jitterentropy {
spinlock_t jent_lock;
struct rand_data *entropy_collector;
unsigned int reset_cnt;
};
static int jent_kcapi_init(struct crypto_tfm *tfm)
{
struct jitterentropy *rng = crypto_tfm_ctx(tfm);
int ret = 0;
rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
if (!rng->entropy_collector)
ret = -ENOMEM;
spin_lock_init(&rng->jent_lock);
return ret;
}
static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
{
struct jitterentropy *rng = crypto_tfm_ctx(tfm);
spin_lock(&rng->jent_lock);
if (rng->entropy_collector)
jent_entropy_collector_free(rng->entropy_collector);
rng->entropy_collector = NULL;
spin_unlock(&rng->jent_lock);
}
static int jent_kcapi_random(struct crypto_rng *tfm,
const u8 *src, unsigned int slen,
u8 *rdata, unsigned int dlen)
{
struct jitterentropy *rng = crypto_rng_ctx(tfm);
int ret = 0;
spin_lock(&rng->jent_lock);
/* Return a permanent error in case we had too many resets in a row. */
if (rng->reset_cnt > (1<<10)) {
ret = -EFAULT;
goto out;
}
ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
/* Reset RNG in case of health failures */
if (ret < -1) {
pr_warn_ratelimited("Reset Jitter RNG due to health test failure: %s failure\n",
(ret == -2) ? "Repetition Count Test" :
"Adaptive Proportion Test");
rng->reset_cnt++;
ret = -EAGAIN;
} else {
rng->reset_cnt = 0;
/* Convert the Jitter RNG error into a usable error code */
if (ret == -1)
ret = -EINVAL;
}
out:
spin_unlock(&rng->jent_lock);
return ret;
}
static int jent_kcapi_reset(struct crypto_rng *tfm,
const u8 *seed, unsigned int slen)
{
return 0;
}
static struct rng_alg jent_alg = {
.generate = jent_kcapi_random,
.seed = jent_kcapi_reset,
.seedsize = 0,
.base = {
.cra_name = "jitterentropy_rng",
.cra_driver_name = "jitterentropy_rng",
.cra_priority = 100,
.cra_ctxsize = sizeof(struct jitterentropy),
.cra_module = THIS_MODULE,
.cra_init = jent_kcapi_init,
.cra_exit = jent_kcapi_cleanup,
}
};
static int __init jent_mod_init(void)
{
int ret = 0;
ret = jent_entropy_init();
if (ret) {
pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
return -EFAULT;
}
return crypto_register_rng(&jent_alg);
}
static void __exit jent_mod_exit(void)
{
crypto_unregister_rng(&jent_alg);
}
module_init(jent_mod_init);
module_exit(jent_mod_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
MODULE_ALIAS_CRYPTO("jitterentropy_rng");