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

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

Changes in v3: - don't keep the TEE session open and simplify the driver: add helper function open_session_ta_hwrng and remove struct optee_rng_priv and function optee_rng_remove()

Changes in v2: - change SPDX-License-Identifier, becausee "GPL-2.0+” is obsolete reference: https://spdx.dev/ids/ - update Kconfig long help message as proposed by Heinrich - replace memset(.., 0, sizeof(..))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

MAINTAINERS | 1 + drivers/rng/Kconfig | 9 ++ drivers/rng/Makefile | 1 + drivers/rng/optee_rng.c | 184 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 195 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..aa8ce864d3 --- /dev/null +++ b/drivers/rng/optee_rng.c @@ -0,0 +1,184 @@ +// 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 } } + +/** open_session_ta_hwrng() - Open session with hwrng Trusted App + * + * @dev: device + * @session_id: return the RNG TA session identifier + * Return: 0 if ok + */ +static int open_session_ta_hwrng(struct udevice *dev, u32 *session_id) +{ + const struct tee_optee_ta_uuid uuid = TA_HWRNG_UUID; + 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; + return ret; + } + + *session_id = sess_arg.session; + return 0; +} + +/** + * get_optee_rng_data() - read RNG data from OP-TEE TA + * + * @dev: device + * @session_id: the RNG TA session identifier + * @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, u32 session_id, + struct tee_shm *entropy_shm_pool, + void *buf, size_t *size) +{ + 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 = 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; + u32 session_id = 0; + + ret = open_session_ta_hwrng(dev, &session_id); + if (ret) { + dev_err(dev, "can't open session: %d\n", ret); + return 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); + goto session_close; + } + + while (read < len) { + rng_size = min(len - read, (size_t)MAX_ENTROPY_REQ_SZ); + ret = get_optee_rng_data(dev, session_id, 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); + +session_close: + tee_close_session(dev->parent, session_id); + + 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) +{ + int ret; + u32 session_id; + + ret = open_session_ta_hwrng(dev, &session_id); + if (ret) { + dev_err(dev, "can't open session: %d\n", ret); + return ret; + } + tee_close_session(dev->parent, 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, +};