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Date: Thu, 04 Jun 2009 15:14:10 -0500
From: Matt Mackall <mpm@...enic.com>
To: Neil Horman <nhorman@...driver.com>
Cc: linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
herbert@...dor.apana.org.au, davem@...emloft.net
Subject: Re: [PATCH] crypto: add optional continuous repetition test to
entropy store based rngs
On Thu, 2009-06-04 at 15:50 -0400, Neil Horman wrote:
> FIPS-140 requires that all random number generators implement continuous self
> tests in which each extracted block of data is compared against the last block
> for repetition. The ansi_cprng implements such a test, but it would be nice if
> the hw rng's did the same thing. Obviously its not something thats always
> needed, but it seems like it would be a nice feature to have on occasion. I've
> written the below patch which allows individual entropy stores to be flagged as
> desiring a continuous test to be run on them as is extracted. By default this
> option is off, but is enabled in the event that fips mode is selected during
> bootup.
>
> Neil
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>
>
> diff --git a/crypto/internal.h b/crypto/internal.h
> index fc76e1f..150d389 100644
> --- a/crypto/internal.h
> +++ b/crypto/internal.h
> @@ -26,12 +26,6 @@
> #include <linux/rwsem.h>
> #include <linux/slab.h>
>
> -#ifdef CONFIG_CRYPTO_FIPS
> -extern int fips_enabled;
> -#else
> -#define fips_enabled 0
> -#endif
> -
> /* Crypto notification events. */
> enum {
> CRYPTO_MSG_ALG_REQUEST,
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 8c74448..fbdfc70 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -250,6 +250,8 @@
> #include <asm/irq.h>
> #include <asm/io.h>
>
> +#include <crypto/algapi.h>
> +
I think we'd rather not make random.c incestuous with crypto/.
> /*
> * Configuration information
> */
> @@ -400,6 +402,7 @@ module_param(debug, bool, 0644);
> **********************************************************************/
>
> struct entropy_store;
> +#define ENT_F_CONT_TEST 1
> struct entropy_store {
> /* read-only data: */
> struct poolinfo *poolinfo;
> @@ -413,6 +416,8 @@ struct entropy_store {
> unsigned add_ptr;
> int entropy_count;
> int input_rotate;
> + int flags;
> + __u8 *last_data;
> };
>
> static __u32 input_pool_data[INPUT_POOL_WORDS];
> @@ -424,7 +429,9 @@ static struct entropy_store input_pool = {
> .name = "input",
> .limit = 1,
> .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock),
> - .pool = input_pool_data
> + .pool = input_pool_data,
> + .flags = 0,
> + .last_data = NULL
> };
No need to null-initialize these things.
> static struct entropy_store blocking_pool = {
> @@ -433,7 +440,9 @@ static struct entropy_store blocking_pool = {
> .limit = 1,
> .pull = &input_pool,
> .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock),
> - .pool = blocking_pool_data
> + .pool = blocking_pool_data,
> + .flags = 0,
> + .last_data = NULL
> };
>
> static struct entropy_store nonblocking_pool = {
> @@ -441,7 +450,9 @@ static struct entropy_store nonblocking_pool = {
> .name = "nonblocking",
> .pull = &input_pool,
> .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock),
> - .pool = nonblocking_pool_data
> + .pool = nonblocking_pool_data,
> + .flags = 0,
> + .last_data = NULL
> };
>
> /*
> @@ -852,12 +863,21 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
> {
> ssize_t ret = 0, i;
> __u8 tmp[EXTRACT_SIZE];
> + unsigned long flags;
>
> xfer_secondary_pool(r, nbytes);
> nbytes = account(r, nbytes, min, reserved);
>
> while (nbytes) {
> extract_buf(r, tmp);
> +
> + if (r->flags & ENT_F_CONT_TEST) {
> + spin_lock_irqsave(&r->lock, flags);
> + if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
> + panic("Hardware RNG duplicated output!\n");
> + memcpy(r->last_data, tmp, EXTRACT_SIZE);
> + spin_unlock_irqrestore(&r->lock, flags);
> + }
This should go in extract_buf. I think we can avoid adding flags to the
pool struct by simply checking that last_data is not null.
> i = min_t(int, nbytes, EXTRACT_SIZE);
> memcpy(buf, tmp, i);
> nbytes -= i;
> @@ -940,6 +960,14 @@ static void init_std_data(struct entropy_store *r)
> now = ktime_get_real();
> mix_pool_bytes(r, &now, sizeof(now));
> mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
> + /* Enable continuous test in fips mode */
> + if (fips_enabled) {
> + r->last_data = kmalloc(EXTRACT_SIZE, GFP_KERNEL);
> + if (r->last_data)
> + r->flags |= ENT_F_CONT_TEST;
> + else
> + panic("Could not alloc data for rng test\n");
> + }
> }
>
> static int rand_initialize(void)
> diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h
> index 0105454..88e9535 100644
> --- a/include/crypto/algapi.h
> +++ b/include/crypto/algapi.h
> @@ -20,6 +20,12 @@ struct module;
> struct rtattr;
> struct seq_file;
>
> +#ifdef CONFIG_CRYPTO_FIPS
> +extern int fips_enabled;
> +#else
> +#define fips_enabled 0
> +#endif
> +
> struct crypto_type {
> unsigned int (*ctxsize)(struct crypto_alg *alg, u32 type, u32 mask);
> unsigned int (*extsize)(struct crypto_alg *alg,
> --
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