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[PATCH v2] crypto: sun4i-ss: support the Security System PRNG

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  [PATCH v2] crypto: sun4i-ss: support the Security System PRNG Corentin Labbe <clabbe.montjoie@gmail.com> - 2016-12-05 12:00 +0100
    Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG Herbert Xu <herbert@gondor.apana.org.au> - 2016-12-05 13:40 +0100
      Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG Corentin Labbe <clabbe.montjoie@gmail.com> - 2016-12-05 14:00 +0100
        Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG Herbert Xu <herbert@gondor.apana.org.au> - 2016-12-07 13:10 +0100
          Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG Corentin Labbe <clabbe.montjoie@gmail.com> - 2016-12-07 14:00 +0100
            Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG Herbert Xu <herbert@gondor.apana.org.au> - 2016-12-08 10:10 +0100
              Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG Corentin Labbe <clabbe.montjoie@gmail.com> - 2016-12-08 10:30 +0100
                Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com> - 2016-12-08 12:10 +0100

#1535993 — [PATCH v2] crypto: sun4i-ss: support the Security System PRNG

From: LABBE Corentin <clabbe.montjoie@gmail.com>

The Security System have a PRNG.
This patch add support for it as an hwrng.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
---
Changes since v1:
 - Replaced all spin_lock_bh by simple spin_lock
 - Removed handling of size not modulo 4 which will never happen
 - Added add_random_ready_callback()

 drivers/crypto/Kconfig                   |  8 +++
 drivers/crypto/sunxi-ss/Makefile         |  1 +
 drivers/crypto/sunxi-ss/sun4i-ss-core.c  | 14 +++++
 drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c | 99 ++++++++++++++++++++++++++++++++
 drivers/crypto/sunxi-ss/sun4i-ss.h       |  9 +++
 5 files changed, 131 insertions(+)
 create mode 100644 drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c

diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
index 4d2b81f..38f7aca 100644
--- a/drivers/crypto/Kconfig
+++ b/drivers/crypto/Kconfig
@@ -538,6 +538,14 @@ config CRYPTO_DEV_SUN4I_SS
 	  To compile this driver as a module, choose M here: the module
 	  will be called sun4i-ss.
 
+config CRYPTO_DEV_SUN4I_SS_PRNG
+	bool "Support for Allwinner Security System PRNG"
+	depends on CRYPTO_DEV_SUN4I_SS
+	select HW_RANDOM
+	help
+	  This driver provides kernel-side support for the Pseudo-Random
+	  Number Generator found in the Security System.
+
 config CRYPTO_DEV_ROCKCHIP
 	tristate "Rockchip's Cryptographic Engine driver"
 	depends on OF && ARCH_ROCKCHIP
diff --git a/drivers/crypto/sunxi-ss/Makefile b/drivers/crypto/sunxi-ss/Makefile
index 8f4c7a2..ca049ee 100644
--- a/drivers/crypto/sunxi-ss/Makefile
+++ b/drivers/crypto/sunxi-ss/Makefile
@@ -1,2 +1,3 @@
 obj-$(CONFIG_CRYPTO_DEV_SUN4I_SS) += sun4i-ss.o
 sun4i-ss-y += sun4i-ss-core.o sun4i-ss-hash.o sun4i-ss-cipher.o
+sun4i-ss-$(CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG) += sun4i-ss-hwrng.o
diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-core.c b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
index 3ac6c6c..fa739de 100644
--- a/drivers/crypto/sunxi-ss/sun4i-ss-core.c
+++ b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
@@ -359,6 +359,16 @@ static int sun4i_ss_probe(struct platform_device *pdev)
 		}
 	}
 	platform_set_drvdata(pdev, ss);
+
+#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
+	/* Voluntarily made the PRNG optional */
+	err = sun4i_ss_hwrng_register(&ss->hwrng);
+	if (!err)
+		dev_info(ss->dev, "sun4i-ss PRNG loaded");
+	else
+		dev_err(ss->dev, "sun4i-ss PRNG failed");
+#endif
+
 	return 0;
 error_alg:
 	i--;
@@ -386,6 +396,10 @@ static int sun4i_ss_remove(struct platform_device *pdev)
 	int i;
 	struct sun4i_ss_ctx *ss = platform_get_drvdata(pdev);
 
+#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
+	sun4i_ss_hwrng_remove(&ss->hwrng);
+#endif
+
 	for (i = 0; i < ARRAY_SIZE(ss_algs); i++) {
 		switch (ss_algs[i].type) {
 		case CRYPTO_ALG_TYPE_ABLKCIPHER:
diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
new file mode 100644
index 0000000..8319cae
--- /dev/null
+++ b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
@@ -0,0 +1,99 @@
+#include "sun4i-ss.h"
+
+static void sun4i_ss_seed(struct random_ready_callback *rdy)
+{
+	struct sun4i_ss_ctx *ss;
+
+	ss = container_of(rdy, struct sun4i_ss_ctx, random_ready);
+	get_random_bytes(ss->seed, SS_SEED_LEN);
+	ss->random_ready.func = NULL;
+}
+
+static int sun4i_ss_hwrng_init(struct hwrng *hwrng)
+{
+	struct sun4i_ss_ctx *ss;
+	int ret;
+
+	ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
+
+	ss->random_ready.owner = THIS_MODULE;
+	ss->random_ready.func = sun4i_ss_seed;
+
+	ret = add_random_ready_callback(&ss->random_ready);
+	switch (ret) {
+	case 0:
+		break;
+	case -EALREADY:
+		get_random_bytes(ss->seed, SS_SEED_LEN);
+		ss->random_ready.func = NULL;
+		ret = 0;
+		break;
+	default:
+		ss->random_ready.func = NULL;
+	}
+
+	return ret;
+}
+
+static int sun4i_ss_hwrng_read(struct hwrng *hwrng, void *buf,
+			       size_t max, bool wait)
+{
+	int i;
+	u32 v;
+	u32 *data = buf;
+	const u32 mode = SS_OP_PRNG | SS_PRNG_CONTINUE | SS_ENABLED;
+	size_t len;
+	struct sun4i_ss_ctx *ss;
+
+	ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
+	len = min_t(size_t, SS_DATA_LEN, max);
+
+	/* If the PRNG is not seeded */
+	if (ss->random_ready.func)
+		return -EAGAIN;
+
+	spin_lock(&ss->slock);
+
+	writel(mode, ss->base + SS_CTL);
+
+	/* write the seed */
+	for (i = 0; i < SS_SEED_LEN / 4; i++)
+		writel(ss->seed[i], ss->base + SS_KEY0 + i * 4);
+	writel(mode | SS_PRNG_START, ss->base + SS_CTL);
+
+	/* Read the random data */
+	readsl(ss->base + SS_TXFIFO, data, len / 4);
+
+	/* Update the seed */
+	for (i = 0; i < SS_SEED_LEN / 4; i++) {
+		v = readl(ss->base + SS_KEY0 + i * 4);
+		ss->seed[i] = v;
+	}
+
+	writel(0, ss->base + SS_CTL);
+	spin_unlock(&ss->slock);
+	return len;
+}
+
+int sun4i_ss_hwrng_register(struct hwrng *hwrng)
+{
+	hwrng->name = "sun4i Security System PRNG";
+	hwrng->init = sun4i_ss_hwrng_init;
+	hwrng->read = sun4i_ss_hwrng_read;
+	hwrng->quality = 1000;
+
+	/* Cannot use devm_hwrng_register() since we need to hwrng_unregister
+	 * before stopping clocks/regulator
+	 */
+	return hwrng_register(hwrng);
+}
+
+void sun4i_ss_hwrng_remove(struct hwrng *hwrng)
+{
+	struct sun4i_ss_ctx *ss;
+
+	ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
+	if (ss->random_ready.func)
+		del_random_ready_callback(&ss->random_ready);
+	hwrng_unregister(hwrng);
+}
diff --git a/drivers/crypto/sunxi-ss/sun4i-ss.h b/drivers/crypto/sunxi-ss/sun4i-ss.h
index f04c0f8..85772d7 100644
--- a/drivers/crypto/sunxi-ss/sun4i-ss.h
+++ b/drivers/crypto/sunxi-ss/sun4i-ss.h
@@ -23,6 +23,7 @@
 #include <linux/scatterlist.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
+#include <linux/hw_random.h>
 #include <crypto/md5.h>
 #include <crypto/sha.h>
 #include <crypto/hash.h>
@@ -125,6 +126,9 @@
 #define SS_RXFIFO_EMP_INT_ENABLE	(1 << 2)
 #define SS_TXFIFO_AVA_INT_ENABLE	(1 << 0)
 
+#define SS_SEED_LEN (192 / 8)
+#define SS_DATA_LEN (160 / 8)
+
 struct sun4i_ss_ctx {
 	void __iomem *base;
 	int irq;
@@ -134,6 +138,9 @@ struct sun4i_ss_ctx {
 	struct device *dev;
 	struct resource *res;
 	spinlock_t slock; /* control the use of the device */
+	struct random_ready_callback random_ready;
+	struct hwrng hwrng;
+	u32 seed[SS_SEED_LEN / 4];
 };
 
 struct sun4i_ss_alg_template {
@@ -199,3 +206,5 @@ int sun4i_ss_des_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
 			unsigned int keylen);
 int sun4i_ss_des3_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
 			 unsigned int keylen);
+int sun4i_ss_hwrng_register(struct hwrng *hwrng);
+void sun4i_ss_hwrng_remove(struct hwrng *hwrng);
-- 
2.7.3

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#1536061

On Mon, Dec 05, 2016 at 11:48:42AM +0100, Corentin Labbe wrote:
> From: LABBE Corentin <clabbe.montjoie@gmail.com>
> 
> The Security System have a PRNG.
> This patch add support for it as an hwrng.
> 
> Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>

Please don't add PRNGs to hwrng.  If we have existing PRNGs in
there please let me know so that we can remove them.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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#1536073

On Mon, Dec 05, 2016 at 08:37:05PM +0800, Herbert Xu wrote:
> On Mon, Dec 05, 2016 at 11:48:42AM +0100, Corentin Labbe wrote:
> > From: LABBE Corentin <clabbe.montjoie@gmail.com>
> > 
> > The Security System have a PRNG.
> > This patch add support for it as an hwrng.
> > 
> > Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
> 
> Please don't add PRNGs to hwrng.  If we have existing PRNGs in
> there please let me know so that we can remove them.
> 

So how to expose PRNG to user space ? or more generally how to "use" a PRNG ?

I found hisi-rng, crypto4xx_ and exynos-rng which seems to be PRNG used as hwrng.

Regards

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#1537706

On Mon, Dec 05, 2016 at 01:57:38PM +0100, Corentin Labbe wrote:
>
> So how to expose PRNG to user space ? or more generally how to "use" a PRNG ?

We do have the algif_rng interface.

> I found hisi-rng, crypto4xx_ and exynos-rng which seems to be PRNG used as hwrng.

Thanks for checking.  Patches to remove these are welcome.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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#1537729

On Wed, Dec 07, 2016 at 08:09:00PM +0800, Herbert Xu wrote:
> On Mon, Dec 05, 2016 at 01:57:38PM +0100, Corentin Labbe wrote:
> >
> > So how to expose PRNG to user space ? or more generally how to "use" a PRNG ?
> 
> We do have the algif_rng interface.
> 

So I must expose it as a crypto_rng ?

Could you explain why PRNG must not be used as hw_random ?

Regards
Corentin Labbe

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#1538388

On Wed, Dec 07, 2016 at 01:51:27PM +0100, Corentin Labbe wrote:
> 
> So I must expose it as a crypto_rng ?

If it is to be exposed at all then algif_rng would be the best
place.

> Could you explain why PRNG must not be used as hw_random ?

The hwrng interface was always meant to be an interface for real
hardware random number generators.  People rely on that so we
should not provide bogus entropy sources through this interface.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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#1538402

On Thu, Dec 08, 2016 at 05:06:18PM +0800, Herbert Xu wrote:
> On Wed, Dec 07, 2016 at 01:51:27PM +0100, Corentin Labbe wrote:
> > 
> > So I must expose it as a crypto_rng ?
> 
> If it is to be exposed at all then algif_rng would be the best
> place.
> 

I have badly said my question.
So I need to use the HW PRNG in a crypto_rng "provider" that could be thereafter used from user space via algif_rng. right ?

> > Could you explain why PRNG must not be used as hw_random ?
> 
> The hwrng interface was always meant to be an interface for real
> hardware random number generators.  People rely on that so we
> should not provide bogus entropy sources through this interface.
> 

Why not adding a KCONFIG HW_RANDOM_ACCEPT_ALSO_PRNG with big warning ?
Or a HW_PRNG Kconfig which do the same than hwrandom with /dev/prng ?
With that it will be much easier to convert in-tree PRNG that you want to remove.

Regards
Corentin Labbe

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#1538435

>> The hwrng interface was always meant to be an interface for real
>> hardware random number generators.  People rely on that so we
>> should not provide bogus entropy sources through this interface.
>>
>
> Why not adding a KCONFIG HW_RANDOM_ACCEPT_ALSO_PRNG with big warning ?
> Or a HW_PRNG Kconfig which do the same than hwrandom with /dev/prng ?
> With that it will be much easier to convert in-tree PRNG that you want to remove.

I do have driver for a PRNG that I was planning to post in sometime.
Upon seeing this thread I think the code has to be changed.

I completely agree with Corentin, adding /dev/prng or /dev/hw_prng
will make it easier to move existing code. It can be made explicit
that using new device will provide only pseudo random number.

Thanks,
PrasannaKumar

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