Re: [PATCH v8 2/4] KEYS: trusted: Introduce TEE based Trusted Keys

Ahmad Fatoum
2021-01-20T13:36:11Z

[-- Attachment #1: Type: text/plain, Size: 12818 bytes --]

Hello Sumit,

On 03.11.20 17:01, Sumit Garg wrote:
> Add support for TEE based trusted keys where TEE provides the functionality
> to seal and unseal trusted keys using hardware unique key.
>
> Refer to Documentation/tee.txt for detailed information about TEE.
>
> Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
> ---
> include/keys/trusted_tee.h | 55 ++++++
> security/keys/trusted-keys/Makefile | 1 +
> security/keys/trusted-keys/trusted_core.c | 4 +
> security/keys/trusted-keys/trusted_tee.c | 278 ++++++++++++++++++++++++++++++
> 4 files changed, 338 insertions(+)
> create mode 100644 include/keys/trusted_tee.h
> create mode 100644 security/keys/trusted-keys/trusted_tee.c
>
> diff --git a/include/keys/trusted_tee.h b/include/keys/trusted_tee.h
> new file mode 100644
> index 0000000..2e2bb15
> --- /dev/null
> +++ b/include/keys/trusted_tee.h
> @@ -0,0 +1,55 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2019-2020 Linaro Ltd.
> + *
> + * Author:
> + * Sumit Garg <sumit.garg@linaro.org>
> + */
> +
> +#ifndef __TEE_TRUSTED_KEY_H
> +#define __TEE_TRUSTED_KEY_H
> +
> +#include <linux/tee_drv.h>
> +
> +#define DRIVER_NAME "tee-trusted-key"

Looks unusual to define this in a header, especially when
it's included in trusted_core.c as well. Could you move it?

> +
> +/*
> + * Get random data for symmetric key
> + *
> + * [out] memref[0] Random data
> + */
> +#define TA_CMD_GET_RANDOM 0x0
> +
> +/*
> + * Seal trusted key using hardware unique key
> + *
> + * [in] memref[0] Plain key
> + * [out] memref[1] Sealed key datablob
> + */
> +#define TA_CMD_SEAL 0x1
> +
> +/*
> + * Unseal trusted key using hardware unique key
> + *
> + * [in] memref[0] Sealed key datablob
> + * [out] memref[1] Plain key
> + */
> +#define TA_CMD_UNSEAL 0x2

These also look like implementation-specific stuff
that should go into trusted_tee.c?

> +
> +/**
> + * struct trusted_key_private - TEE Trusted key private data
> + * @dev: TEE based Trusted key device.
> + * @ctx: TEE context handler.
> + * @session_id: Trusted key TA session identifier.
> + * @shm_pool: Memory pool shared with TEE device.
> + */
> +struct trusted_key_private {

This is name is a bit too generic. Either move it to trusted_tee
or put a caam_ prefix in front?

> + struct device *dev;
> + struct tee_context *ctx;
> + u32 session_id;
> + struct tee_shm *shm_pool;
> +};
> +
> +extern struct trusted_key_ops tee_trusted_key_ops;

This looks like the only thing that must be in this header.

> +
> +#endif
> diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
> index 49e3bcf..012dd78 100644
> --- a/security/keys/trusted-keys/Makefile
> +++ b/security/keys/trusted-keys/Makefile
> @@ -7,3 +7,4 @@ obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
> trusted-y += trusted_core.o
> trusted-y += trusted_tpm1.o
> trusted-y += trusted_tpm2.o
> +trusted-y += trusted_tee.o

Shouldn't this depend on CONFIG_TEE or similar? Otherwise without LTO, you'd
run into linker errors.

[Apologies if these points were raised in previous review cycles, I just
recently subscribed]

Cheers,
Ahmad

> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> index aa4f2a0..15b1b0f3 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -8,6 +8,7 @@
>
> #include <keys/user-type.h>
> #include <keys/trusted-type.h>
> +#include <keys/trusted_tee.h>
> #include <keys/trusted_tpm.h>
> #include <linux/capability.h>
> #include <linux/err.h>
> @@ -29,6 +30,9 @@ static const struct trusted_key_source trusted_key_sources[] = {
> #if defined(CONFIG_TCG_TPM)
> { "tpm", &tpm_trusted_key_ops },
> #endif
> +#if defined(CONFIG_TEE)
> + { "tee", &tee_trusted_key_ops },
> +#endif
> };
>
> DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init);
> diff --git a/security/keys/trusted-keys/trusted_tee.c b/security/keys/trusted-keys/trusted_tee.c
> new file mode 100644
> index 0000000..da8785a
> --- /dev/null
> +++ b/security/keys/trusted-keys/trusted_tee.c
> @@ -0,0 +1,278 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019-2020 Linaro Ltd.
> + *
> + * Author:
> + * Sumit Garg <sumit.garg@linaro.org>
> + */
> +
> +#include <linux/err.h>
> +#include <linux/key-type.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/uuid.h>
> +
> +#include <keys/trusted-type.h>
> +#include <keys/trusted_tee.h>
> +
> +static struct trusted_key_private pvt_data;
> +
> +/*
> + * Have the TEE seal(encrypt) the symmetric key
> + */
> +static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
> +{
> + int ret;
> + struct tee_ioctl_invoke_arg inv_arg;
> + struct tee_param param[4];
> + struct tee_shm *reg_shm_in = NULL, *reg_shm_out = NULL;
> +
> + memset(&inv_arg, 0, sizeof(inv_arg));
> + memset(&param, 0, sizeof(param));
> +
> + reg_shm_in = tee_shm_register(pvt_data.ctx, (unsigned long)p->key,
> + p->key_len, TEE_SHM_DMA_BUF |
> + TEE_SHM_KERNEL_MAPPED);
> + if (IS_ERR(reg_shm_in)) {
> + dev_err(pvt_data.dev, "key shm register failed\n");
> + return PTR_ERR(reg_shm_in);
> + }
> +
> + reg_shm_out = tee_shm_register(pvt_data.ctx, (unsigned long)p->blob,
> + sizeof(p->blob), TEE_SHM_DMA_BUF |
> + TEE_SHM_KERNEL_MAPPED);
> + if (IS_ERR(reg_shm_out)) {
> + dev_err(pvt_data.dev, "blob shm register failed\n");
> + ret = PTR_ERR(reg_shm_out);
> + goto out;
> + }
> +
> + inv_arg.func = TA_CMD_SEAL;
> + inv_arg.session = pvt_data.session_id;
> + inv_arg.num_params = 4;
> +
> + param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
> + param[0].u.memref.shm = reg_shm_in;
> + param[0].u.memref.size = p->key_len;
> + param[0].u.memref.shm_offs = 0;
> + param[1].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
> + param[1].u.memref.shm = reg_shm_out;
> + param[1].u.memref.size = sizeof(p->blob);
> + param[1].u.memref.shm_offs = 0;
> +
> + ret = tee_client_invoke_func(pvt_data.ctx, &inv_arg, param);
> + if ((ret < 0) || (inv_arg.ret != 0)) {
> + dev_err(pvt_data.dev, "TA_CMD_SEAL invoke err: %x\n",
> + inv_arg.ret);
> + ret = -EFAULT;
> + } else {
> + p->blob_len = param[1].u.memref.size;
> + }
> +
> +out:
> + if (reg_shm_out)
> + tee_shm_free(reg_shm_out);
> + if (reg_shm_in)
> + tee_shm_free(reg_shm_in);
> +
> + return ret;
> +}
> +
> +/*
> + * Have the TEE unseal(decrypt) the symmetric key
> + */
> +static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
> +{
> + int ret;
> + struct tee_ioctl_invoke_arg inv_arg;
> + struct tee_param param[4];
> + struct tee_shm *reg_shm_in = NULL, *reg_shm_out = NULL;
> +
> + memset(&inv_arg, 0, sizeof(inv_arg));
> + memset(&param, 0, sizeof(param));
> +
> + reg_shm_in = tee_shm_register(pvt_data.ctx, (unsigned long)p->blob,
> + p->blob_len, TEE_SHM_DMA_BUF |
> + TEE_SHM_KERNEL_MAPPED);
> + if (IS_ERR(reg_shm_in)) {
> + dev_err(pvt_data.dev, "blob shm register failed\n");
> + return PTR_ERR(reg_shm_in);
> + }
> +
> + reg_shm_out = tee_shm_register(pvt_data.ctx, (unsigned long)p->key,
> + sizeof(p->key), TEE_SHM_DMA_BUF |
> + TEE_SHM_KERNEL_MAPPED);
> + if (IS_ERR(reg_shm_out)) {
> + dev_err(pvt_data.dev, "key shm register failed\n");
> + ret = PTR_ERR(reg_shm_out);
> + goto out;
> + }
> +
> + inv_arg.func = TA_CMD_UNSEAL;
> + inv_arg.session = pvt_data.session_id;
> + inv_arg.num_params = 4;
> +
> + param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
> + param[0].u.memref.shm = reg_shm_in;
> + param[0].u.memref.size = p->blob_len;
> + param[0].u.memref.shm_offs = 0;
> + param[1].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
> + param[1].u.memref.shm = reg_shm_out;
> + param[1].u.memref.size = sizeof(p->key);
> + param[1].u.memref.shm_offs = 0;
> +
> + ret = tee_client_invoke_func(pvt_data.ctx, &inv_arg, param);
> + if ((ret < 0) || (inv_arg.ret != 0)) {
> + dev_err(pvt_data.dev, "TA_CMD_UNSEAL invoke err: %x\n",
> + inv_arg.ret);
> + ret = -EFAULT;
> + } else {
> + p->key_len = param[1].u.memref.size;
> + }
> +
> +out:
> + if (reg_shm_out)
> + tee_shm_free(reg_shm_out);
> + if (reg_shm_in)
> + tee_shm_free(reg_shm_in);
> +
> + return ret;
> +}
> +
> +/*
> + * Have the TEE generate random symmetric key
> + */
> +static int trusted_tee_get_random(unsigned char *key, size_t key_len)
> +{
> + int ret;
> + struct tee_ioctl_invoke_arg inv_arg;
> + struct tee_param param[4];
> + struct tee_shm *reg_shm = NULL;
> +
> + memset(&inv_arg, 0, sizeof(inv_arg));
> + memset(&param, 0, sizeof(param));
> +
> + reg_shm = tee_shm_register(pvt_data.ctx, (unsigned long)key, key_len,
> + TEE_SHM_DMA_BUF | TEE_SHM_KERNEL_MAPPED);
> + if (IS_ERR(reg_shm)) {
> + dev_err(pvt_data.dev, "key shm register failed\n");
> + return PTR_ERR(reg_shm);
> + }
> +
> + inv_arg.func = TA_CMD_GET_RANDOM;
> + inv_arg.session = pvt_data.session_id;
> + inv_arg.num_params = 4;
> +
> + param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
> + param[0].u.memref.shm = reg_shm;
> + param[0].u.memref.size = key_len;
> + param[0].u.memref.shm_offs = 0;
> +
> + ret = tee_client_invoke_func(pvt_data.ctx, &inv_arg, param);
> + if ((ret < 0) || (inv_arg.ret != 0)) {
> + dev_err(pvt_data.dev, "TA_CMD_GET_RANDOM invoke err: %x\n",
> + inv_arg.ret);
> + ret = -EFAULT;
> + } else {
> + ret = param[0].u.memref.size;
> + }
> +
> + tee_shm_free(reg_shm);
> +
> + return ret;
> +}
> +
> +static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
> +{
> + if (ver->impl_id == TEE_IMPL_ID_OPTEE)
> + return 1;
> + else
> + return 0;
> +}
> +
> +static int trusted_key_probe(struct device *dev)
> +{
> + struct tee_client_device *rng_device = to_tee_client_device(dev);
> + int ret;
> + struct tee_ioctl_open_session_arg sess_arg;
> +
> + memset(&sess_arg, 0, sizeof(sess_arg));
> +
> + pvt_data.ctx = tee_client_open_context(NULL, optee_ctx_match, NULL,
> + NULL);
> + if (IS_ERR(pvt_data.ctx))
> + return -ENODEV;
> +
> + memcpy(sess_arg.uuid, rng_device->id.uuid.b, TEE_IOCTL_UUID_LEN);
> + sess_arg.clnt_login = TEE_IOCTL_LOGIN_REE_KERNEL;
> + sess_arg.num_params = 0;
> +
> + ret = tee_client_open_session(pvt_data.ctx, &sess_arg, NULL);
> + if ((ret < 0) || (sess_arg.ret != 0)) {
> + dev_err(dev, "tee_client_open_session failed, err: %x\n",
> + sess_arg.ret);
> + ret = -EINVAL;
> + goto out_ctx;
> + }
> + pvt_data.session_id = sess_arg.session;
> +
> + ret = register_key_type(&key_type_trusted);
> + if (ret < 0)
> + goto out_sess;
> +
> + pvt_data.dev = dev;
> +
> + return 0;
> +
> +out_sess:
> + tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
> +out_ctx:
> + tee_client_close_context(pvt_data.ctx);
> +
> + return ret;
> +}
> +
> +static int trusted_key_remove(struct device *dev)
> +{
> + unregister_key_type(&key_type_trusted);
> + tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
> + tee_client_close_context(pvt_data.ctx);
> +
> + return 0;
> +}
> +
> +static const struct tee_client_device_id trusted_key_id_table[] = {
> + {UUID_INIT(0xf04a0fe7, 0x1f5d, 0x4b9b,
> + 0xab, 0xf7, 0x61, 0x9b, 0x85, 0xb4, 0xce, 0x8c)},
> + {}
> +};
> +MODULE_DEVICE_TABLE(tee, trusted_key_id_table);
> +
> +static struct tee_client_driver trusted_key_driver = {
> + .id_table = trusted_key_id_table,
> + .driver = {
> + .name = DRIVER_NAME,
> + .bus = &tee_bus_type,
> + .probe = trusted_key_probe,
> + .remove = trusted_key_remove,
> + },
> +};
> +
> +static int trusted_tee_init(void)
> +{
> + return driver_register(&trusted_key_driver.driver);
> +}
> +
> +static void trusted_tee_exit(void)
> +{
> + driver_unregister(&trusted_key_driver.driver);
> +}
> +
> +struct trusted_key_ops tee_trusted_key_ops = {
> + .migratable = 0, /* non-migratable */
> + .init = trusted_tee_init,
> + .seal = trusted_tee_seal,
> + .unseal = trusted_tee_unseal,
> + .get_random = trusted_tee_get_random,
> + .exit = trusted_tee_exit,
> +};
>

--
Pengutronix e.K. | |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |