[v4,2/6] crypto: caam - enable prediction resistance in HRWNG
diff mbox series

Message ID 20191121155554.1227-3-andrew.smirnov@gmail.com
State Superseded
Delegated to: Herbert Xu
Headers show
Series
  • enable CAAM's HWRNG as default
Related show

Commit Message

Andrey Smirnov Nov. 21, 2019, 3:55 p.m. UTC
Instantiate CAAM RNG with prediction resistance enabled to improve its
quality.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Horia Geantă <horia.geanta@nxp.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Iuliana Prodan <iuliana.prodan@nxp.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-imx@nxp.com
---
 drivers/crypto/caam/caamrng.c | 3 ++-
 drivers/crypto/caam/ctrl.c    | 8 +++++---
 drivers/crypto/caam/desc.h    | 2 ++
 drivers/crypto/caam/regs.h    | 4 +++-
 4 files changed, 12 insertions(+), 5 deletions(-)

Comments

Horia Geanta Nov. 26, 2019, 9:13 a.m. UTC | #1
On 11/21/2019 5:56 PM, Andrey Smirnov wrote:
> Instantiate CAAM RNG with prediction resistance enabled to improve its
> quality.
> 
It's worth noting there are two RNG operations being changed:
-instantiation
-generation

Generation with prediction resistance (PR) is only supported on
RNG state handles instantiated with PR option.

Using PR when generating randomness effectively forces a reseed
of the DRBG / PRNG - that's how quality is improved.

> diff --git a/drivers/crypto/caam/caamrng.c b/drivers/crypto/caam/caamrng.c
> index e8baacaabe07..6dde8ae3cd9b 100644
> --- a/drivers/crypto/caam/caamrng.c
> +++ b/drivers/crypto/caam/caamrng.c
> @@ -202,7 +202,8 @@ static inline int rng_create_sh_desc(struct caam_rng_ctx *ctx)
>  	init_sh_desc(desc, HDR_SHARE_SERIAL);
>  
>  	/* Generate random bytes */
> -	append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG);
> +	append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG |
> +			 OP_ALG_PR_ON);
>  
>  	/* Store bytes */
>  	append_seq_fifo_store(desc, RN_BUF_SIZE, FIFOST_TYPE_RNGSTORE);
> diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
> index df4db10e9fca..a1c879820286 100644
> --- a/drivers/crypto/caam/ctrl.c
> +++ b/drivers/crypto/caam/ctrl.c
> @@ -36,7 +36,8 @@ static void build_instantiation_desc(u32 *desc, int handle, int do_sk)
>  	init_job_desc(desc, 0);
>  
>  	op_flags = OP_TYPE_CLASS1_ALG | OP_ALG_ALGSEL_RNG |
> -			(handle << OP_ALG_AAI_SHIFT) | OP_ALG_AS_INIT;
> +			(handle << OP_ALG_AAI_SHIFT) | OP_ALG_AS_INIT |
> +			OP_ALG_PR_ON;
>  
>  	/* INIT RNG in non-test mode */
>  	append_operation(desc, op_flags);
> @@ -275,11 +276,12 @@ static int instantiate_rng(struct device *ctrldev, int state_handle_mask,
>  		return -ENOMEM;
>  
>  	for (sh_idx = 0; sh_idx < RNG4_MAX_HANDLES; sh_idx++) {
> +		const u32 rdsta_mask = (RDSTA_PR0 | RDSTA_IF0) << sh_idx;
>  		/*
>  		 * If the corresponding bit is set, this state handle
>  		 * was initialized by somebody else, so it's left alone.
>  		 */
> -		if ((1 << sh_idx) & state_handle_mask)
> +		if (rdsta_mask & state_handle_mask)
>  			continue;
>  
If a state handle was previously instantiated (e.g. by U-boot),
but without prediction resistance support, it won't be re-instantiated
("continue" / skip above).

The result is using a state handle without PR support.
Due to this, when extracting / generating randomness (in caamrng.c) with
the PR bit set, job descriptor will generate a prediction resistance error.

IMO the proper thing to do in case a state handle was instantiated
without PR support is to re-instantiate it.

There's an assumption here though: kernel handles RNG initialization only
in some cases, when it's effectively "controlling" it.
In cases when it's not, like when Management Complex (MC) f/w is present
(or OP-TEE OS, SECO etc.), kernel skips RNG init and only uses the job ring
interface for random generation.
==> MC, OP-TEE, SECO etc. have to be updated to initialize
RNG state handles with PR support

Horia

Patch
diff mbox series

diff --git a/drivers/crypto/caam/caamrng.c b/drivers/crypto/caam/caamrng.c
index e8baacaabe07..6dde8ae3cd9b 100644
--- a/drivers/crypto/caam/caamrng.c
+++ b/drivers/crypto/caam/caamrng.c
@@ -202,7 +202,8 @@  static inline int rng_create_sh_desc(struct caam_rng_ctx *ctx)
 	init_sh_desc(desc, HDR_SHARE_SERIAL);
 
 	/* Generate random bytes */
-	append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG);
+	append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG |
+			 OP_ALG_PR_ON);
 
 	/* Store bytes */
 	append_seq_fifo_store(desc, RN_BUF_SIZE, FIFOST_TYPE_RNGSTORE);
diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
index df4db10e9fca..a1c879820286 100644
--- a/drivers/crypto/caam/ctrl.c
+++ b/drivers/crypto/caam/ctrl.c
@@ -36,7 +36,8 @@  static void build_instantiation_desc(u32 *desc, int handle, int do_sk)
 	init_job_desc(desc, 0);
 
 	op_flags = OP_TYPE_CLASS1_ALG | OP_ALG_ALGSEL_RNG |
-			(handle << OP_ALG_AAI_SHIFT) | OP_ALG_AS_INIT;
+			(handle << OP_ALG_AAI_SHIFT) | OP_ALG_AS_INIT |
+			OP_ALG_PR_ON;
 
 	/* INIT RNG in non-test mode */
 	append_operation(desc, op_flags);
@@ -275,11 +276,12 @@  static int instantiate_rng(struct device *ctrldev, int state_handle_mask,
 		return -ENOMEM;
 
 	for (sh_idx = 0; sh_idx < RNG4_MAX_HANDLES; sh_idx++) {
+		const u32 rdsta_mask = (RDSTA_PR0 | RDSTA_IF0) << sh_idx;
 		/*
 		 * If the corresponding bit is set, this state handle
 		 * was initialized by somebody else, so it's left alone.
 		 */
-		if ((1 << sh_idx) & state_handle_mask)
+		if (rdsta_mask & state_handle_mask)
 			continue;
 
 		/* Create the descriptor for instantiating RNG State Handle */
@@ -302,7 +304,7 @@  static int instantiate_rng(struct device *ctrldev, int state_handle_mask,
 
 		rdsta_val = rd_reg32(&ctrl->r4tst[0].rdsta) & RDSTA_IFMASK;
 		if ((status && status != JRSTA_SSRC_JUMP_HALT_CC) ||
-		    !(rdsta_val & (1 << sh_idx))) {
+		    (rdsta_val & rdsta_mask) != rdsta_mask) {
 			ret = -EAGAIN;
 			break;
 		}
diff --git a/drivers/crypto/caam/desc.h b/drivers/crypto/caam/desc.h
index 4b6854bf896a..e796d3cb9be8 100644
--- a/drivers/crypto/caam/desc.h
+++ b/drivers/crypto/caam/desc.h
@@ -1254,6 +1254,8 @@ 
 #define OP_ALG_ICV_OFF		(0 << OP_ALG_ICV_SHIFT)
 #define OP_ALG_ICV_ON		(1 << OP_ALG_ICV_SHIFT)
 
+#define OP_ALG_PR_ON		BIT(1)
+
 #define OP_ALG_DIR_SHIFT	0
 #define OP_ALG_DIR_MASK		1
 #define OP_ALG_DECRYPT		0
diff --git a/drivers/crypto/caam/regs.h b/drivers/crypto/caam/regs.h
index c191e8fd0fa7..fe1f8c1409fd 100644
--- a/drivers/crypto/caam/regs.h
+++ b/drivers/crypto/caam/regs.h
@@ -524,9 +524,11 @@  struct rng4tst {
 	u32 rsvd1[40];
 #define RDSTA_SKVT 0x80000000
 #define RDSTA_SKVN 0x40000000
+#define RDSTA_PR0 BIT(4)
+#define RDSTA_PR1 BIT(5)
 #define RDSTA_IF0 0x00000001
 #define RDSTA_IF1 0x00000002
-#define RDSTA_IFMASK (RDSTA_IF1 | RDSTA_IF0)
+#define RDSTA_IFMASK (RDSTA_PR1 | RDSTA_PR0 | RDSTA_IF1 | RDSTA_IF0)
 	u32 rdsta;
 	u32 rsvd2[15];
 };