rng: add OP-TEE based Random Number Generator

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>

diff --git a/MAINTAINERS b/MAINTAINERS
index 0fc034f01fcb8054f90d8f651823eb5dac705e71..6142504284495bded10bcfe64d93a73bcf53edd4 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -486,6 +486,7 @@ 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 b1c5ab93d15dd21263309959fc5bb1800b1fa6f4..c10f7d345bdafdb9546dc98ad08793961bb7f3c2 100644 (file)
--- 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 39f7ee3f03157a71e1bb170a64840c25ddeeffa4..435b3b965adbd6f0ccc0bb2226871f6b9d848f50 100644 (file)
--- 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 (file)
index 0000000..aa8ce86
--- /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,
+};