Re: [PATCH v2 1/3] rng: add OP-TEE based Random Number Generator

On 3/28/22 15:11, Patrick Delaunay wrote:

Add driver for OP-TEE based Random Number Generator on ARM SoCs where hardware entropy sources are not accessible to normal world and the RNG service is provided by a HWRNG Trusted Application (TA).

This driver is based on the linux driver: char/hw_random/optee-rng.c

Series_changes: 2

• change SPDX-License-Identifier, becausee "GPL-2.0+” is obsolete reference: https://spdx.dev/ids/
• update Kconfig long help message as proposed by Heinrich
• replace memset(.., 0, sizeof(..)) by struct initialisation (= {0};)
• add function descriptions

Signed-off-by: Patrick Delaunay patrick.delaunay@foss.st.com

(no changes since v1)

MAINTAINERS | 1 + drivers/rng/Kconfig | 9 ++ drivers/rng/Makefile | 1 + drivers/rng/optee_rng.c | 180 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 191 insertions(+) create mode 100644 drivers/rng/optee_rng.c

diff --git a/MAINTAINERS b/MAINTAINERS index f25ca7cd00..3356c65dd0 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -481,6 +481,7 @@ F: drivers/power/regulator/stpmic1.c F: drivers/ram/stm32mp1/ F: drivers/remoteproc/stm32_copro.c F: drivers/reset/stm32-reset.c +F: drivers/rng/optee_rng.c F: drivers/rng/stm32mp1_rng.c F: drivers/rtc/stm32_rtc.c F: drivers/serial/serial_stm32.* diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig index b1c5ab93d1..c10f7d345b 100644 --- a/drivers/rng/Kconfig +++ b/drivers/rng/Kconfig @@ -31,6 +31,15 @@ config RNG_MSM This driver provides support for the Random Number Generator hardware found on Qualcomm SoCs.

+config RNG_OPTEE

• bool "OP-TEE based Random Number Generator support"
• depends on DM_RNG && OPTEE
• help

•  This driver provides support for the OP-TEE based Random Number
  

•  Generator on ARM SoCs where hardware entropy sources are not
  

•  accessible to normal world but reserved and used by the OP-TEE
  

•  to avoid the weakness of a software PRNG.
  

• config RNG_STM32MP1 bool "Enable random number generator for STM32MP1" depends on ARCH_STM32MP

diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile index 39f7ee3f03..435b3b965a 100644 --- a/drivers/rng/Makefile +++ b/drivers/rng/Makefile @@ -7,6 +7,7 @@ obj-$(CONFIG_DM_RNG) += rng-uclass.o obj-$(CONFIG_RNG_MESON) += meson-rng.o obj-$(CONFIG_RNG_SANDBOX) += sandbox_rng.o obj-$(CONFIG_RNG_MSM) += msm_rng.o +obj-$(CONFIG_RNG_OPTEE) += optee_rng.o obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o diff --git a/drivers/rng/optee_rng.c b/drivers/rng/optee_rng.c new file mode 100644 index 0000000000..7be428ac91 --- /dev/null +++ b/drivers/rng/optee_rng.c @@ -0,0 +1,180 @@ +// SPDX-License-Identifier: GPL-2.0-or-later OR BSD-3-Clause +/*

• • Copyright (C) 2022, STMicroelectronics - All Rights Reserved
• */

+#define LOG_CATEGORY UCLASS_RNG

+#include <common.h>

+#include <rng.h> +#include <tee.h> +#include <dm/device.h> +#include <dm/device_compat.h> +#include <linux/sizes.h>

+#define TEE_ERROR_HEALTH_TEST_FAIL 0x00000001

+/*

• • TA_CMD_GET_ENTROPY - Get Entropy from RNG
• • param[0] (inout memref) - Entropy buffer memory reference
• • param[1] unused
• • param[2] unused
• • param[3] unused
• • Result:
• • TEE_SUCCESS - Invoke command success
• • TEE_ERROR_BAD_PARAMETERS - Incorrect input param
• • TEE_ERROR_NOT_SUPPORTED - Requested entropy size greater than size of pool
• • TEE_ERROR_HEALTH_TEST_FAIL - Continuous health testing failed
• */

+#define TA_CMD_GET_ENTROPY 0x0

+#define MAX_ENTROPY_REQ_SZ SZ_4K

+#define TA_HWRNG_UUID { 0xab7a617c, 0xb8e7, 0x4d8f, \

• 	{ 0x83, 0x01, 0xd0, 0x9b, 0x61, 0x03, 0x6b, 0x64 } }
  

+/**

• • struct optee_rng_priv - OP-TEE Random Number Generator private data
• • @session_id: RNG TA session identifier.
• */

+struct optee_rng_priv {

• u32 session_id;

+};

+/**

• • get_optee_rng_data() - read RNG data from OP-TEE TA
• • @dev: device
• • @entropy_shm_pool: shared memory pool used for TEE message
• • @buf: buffer to receive data
• • @size: size of buffer, limited by entropy_shm_pool size
• • Return: 0 if ok
• */

+static int get_optee_rng_data(struct udevice *dev,

• 	      struct tee_shm *entropy_shm_pool,
  

• 	      void *buf, size_t *size)
  

+{

• struct optee_rng_priv *priv = dev_get_priv(dev);
• int ret = 0;
• struct tee_invoke_arg arg = {0};
• struct tee_param param = {0};
• /* Invoke TA_CMD_GET_ENTROPY function of Trusted App */
• arg.func = TA_CMD_GET_ENTROPY;
• arg.session = priv->session_id;
• /* Fill invoke cmd params */
• param.attr = TEE_PARAM_ATTR_TYPE_MEMREF_INOUT;
• param.u.memref.shm = entropy_shm_pool;
• param.u.memref.size = *size;
• ret = tee_invoke_func(dev->parent, &arg, 1, &param);
• if (ret || arg.ret) {

• if (!ret)
  

• 	ret = -EPROTO;
  

• dev_err(dev, "TA_CMD_GET_ENTROPY invoke err: %d 0x%x\n", ret, arg.ret);
  

• *size = 0;
  

• return ret;
  

• }
• memcpy(buf, param.u.memref.shm->addr, param.u.memref.size);
• *size = param.u.memref.size;
• return 0;

+}

+/**

• • optee_rng_read() - rng read ops for OP-TEE RNG device
• • @dev: device
• • @buf: buffer to receive data
• • @len: size of buffer
• • Return: 0 if ok
• */

+static int optee_rng_read(struct udevice *dev, void *buf, size_t len) +{

• size_t read = 0, rng_size = 0;
• struct tee_shm *entropy_shm_pool;
• u8 *data = buf;
• int ret;
• ret = tee_shm_alloc(dev->parent, MAX_ENTROPY_REQ_SZ, 0, &entropy_shm_pool);
• if (ret) {

• dev_err(dev, "tee_shm_alloc failed: %d\n", ret);
  

• return ret;
  

• }
• while (read < len) {

• rng_size = min(len - read, (size_t)MAX_ENTROPY_REQ_SZ);
  

• ret = get_optee_rng_data(dev, entropy_shm_pool, data, &rng_size);
  

• if (ret)
  

• 	goto shm_free;
  

• data += rng_size;
  

• read += rng_size;
  

• }

+shm_free:

• tee_shm_free(entropy_shm_pool);
• return ret;

+}

+/**

• • optee_rng_probe() - probe function for OP-TEE RNG device
• • @dev: device
• • Return: 0 if ok
• */

+static int optee_rng_probe(struct udevice *dev) +{

• const struct tee_optee_ta_uuid uuid = TA_HWRNG_UUID;
• struct optee_rng_priv *priv = dev_get_priv(dev);
• struct tee_open_session_arg sess_arg = {0};
• int ret;
• /* Open session with hwrng Trusted App */
• tee_optee_ta_uuid_to_octets(sess_arg.uuid, &uuid);
• sess_arg.clnt_login = TEE_LOGIN_PUBLIC;
• ret = tee_open_session(dev->parent, &sess_arg, 0, NULL);
• if (ret || sess_arg.ret) {

• if (!ret)
  

• 	ret = -EIO;
  

• dev_err(dev, "can't open session: %d 0x%x\n", ret, sess_arg.ret);
  

• return ret;
  

• }
• priv->session_id = sess_arg.session;

Is it really necessary to keep the session open? Or should we reopen a session whenever a random number is requested?

Best regards

Heinrich

• return 0;

+}

+/**

• • optee_rng_remove() - remove function for OP-TEE RNG device
• • @dev: device
• • Return: 0
• */

+static int optee_rng_remove(struct udevice *dev) +{

• struct optee_rng_priv *priv = dev_get_priv(dev);
• tee_close_session(dev->parent, priv->session_id);
• return 0;

+}

+static const struct dm_rng_ops optee_rng_ops = {

• .read = optee_rng_read,

+};

+U_BOOT_DRIVER(optee_rng) = {

• .name = "optee-rng",
• .id = UCLASS_RNG,
• .ops = &optee_rng_ops,
• .probe = optee_rng_probe,
• .remove = optee_rng_remove,
• .priv_auto = sizeof(struct optee_rng_priv),

+};