TEE Client API defines that from user space only information needed for specified login operations is group identifier for group based logins.

REE kernel is expected to formulate trustworthy client UUID and pass that to TEE environment. REE kernel is required to verify that provided group identifier for group based logins matches calling processes group memberships.

TEE specification only defines that the information passed from REE environment to TEE environment is encoded into on UUID.

In order to guarantee trustworthiness of client UUID user space is not allowed to freely pass client UUID.

UUIDv5 form is used encode variable amount of information needed for different login types.

Signed-off-by: Vesa Jääskeläinen vesa.jaaskelainen@vaisala.com --- drivers/tee/Kconfig | 1 + drivers/tee/tee_core.c | 153 ++++++++++++++++++++++++++++++++++++++++ include/linux/tee_drv.h | 16 +++++ 3 files changed, 170 insertions(+)

diff --git a/drivers/tee/Kconfig b/drivers/tee/Kconfig index 8da63f38e6bd..806eb87d4da0 100644 --- a/drivers/tee/Kconfig +++ b/drivers/tee/Kconfig @@ -3,6 +3,7 @@ config TEE tristate "Trusted Execution Environment support" depends on HAVE_ARM_SMCCC || COMPILE_TEST || CPU_SUP_AMD + select CRYPTO_SHA1 select DMA_SHARED_BUFFER select GENERIC_ALLOCATOR help diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c index 6aec502c495c..d5db206d6af2 100644 --- a/drivers/tee/tee_core.c +++ b/drivers/tee/tee_core.c @@ -6,18 +6,33 @@ #define pr_fmt(fmt) "%s: " fmt, __func__

#include <linux/cdev.h> +#include <linux/cred.h> #include <linux/fs.h> #include <linux/idr.h> #include <linux/module.h> #include <linux/slab.h> #include <linux/tee_drv.h> #include <linux/uaccess.h> +#include <crypto/hash.h> +#include <crypto/sha.h> #include "tee_private.h"

#define TEE_NUM_DEVICES 32

#define TEE_IOCTL_PARAM_SIZE(x) (sizeof(struct tee_param) * (x))

+#define TEE_UUID_NS_NAME_SIZE 128 + +/* + * TEE Client UUID name space identifier (UUIDv4) + * + * Value here is random UUID that is allocated as name space identifier for + * forming Client UUID's for TEE environment using UUIDv5 scheme. + */ +static const uuid_t tee_client_uuid_ns = UUID_INIT(0x58ac9ca0, 0x2086, 0x4683, + 0xa1, 0xb8, 0xec, 0x4b, + 0xc0, 0x8e, 0x01, 0xb6); + /* * Unprivileged devices in the lower half range and privileged devices in * the upper half range. @@ -110,6 +125,144 @@ static int tee_release(struct inode *inode, struct file *filp) return 0; }

+/** + * uuid_v5() - Calculate UUIDv5 + * @uuid: Resulting UUID + * @ns: Name space ID for UUIDv5 function + * @name: Name for UUIDv5 function + * @size: Size of name + * + * UUIDv5 is specific in RFC 4122. + * + * This implements section (for SHA-1): + * 4.3. Algorithm for Creating a Name-Based UUID + */ +static int uuid_v5(uuid_t *uuid, const uuid_t *ns, const void *name, + size_t size) +{ + unsigned char hash[SHA1_DIGEST_SIZE]; + struct crypto_shash *shash = NULL; + struct shash_desc *desc = NULL; + int rc; + + shash = crypto_alloc_shash("sha1", 0, 0); + if (IS_ERR(shash)) { + rc = PTR_ERR(shash); + pr_err("shash(sha1) allocation failed\n"); + return rc; + } + + desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(shash), + GFP_KERNEL); + if (!desc) { + rc = -ENOMEM; + goto out_free_shash; + } + + desc->tfm = shash; + + rc = crypto_shash_init(desc); + if (rc < 0) + goto out_free_desc; + + rc = crypto_shash_update(desc, (const u8 *)ns, sizeof(*ns)); + if (rc < 0) + goto out_free_desc; + + rc = crypto_shash_update(desc, (const u8 *)name, size); + if (rc < 0) + goto out_free_desc; + + rc = crypto_shash_final(desc, hash); + if (rc < 0) + goto out_free_desc; + + memcpy(uuid->b, hash, UUID_SIZE); + + /* Tag for version 5 */ + uuid->b[6] = (hash[6] & 0x0F) | 0x50; + uuid->b[8] = (hash[8] & 0x3F) | 0x80; + +out_free_desc: + kfree(desc); + +out_free_shash: + crypto_free_shash(shash); + return rc; +} + +int tee_session_calc_client_uuid(uuid_t *uuid, u32 connection_method, + const u8 connection_data[TEE_IOCTL_UUID_LEN]) +{ + const char *application_id = NULL; + gid_t ns_grp = (gid_t)-1; + kgid_t grp = INVALID_GID; + char *name = NULL; + int name_len; + int rc; + + if (connection_method == TEE_IOCTL_LOGIN_PUBLIC) { + /* Nil UUID to be passed to TEE environment */ + uuid_copy(uuid, &uuid_null); + return 0; + } + + /* + * In Linux environment client UUID is based on UUIDv5. + * + * Determine client UUID with following semantics for 'name': + * + * For TEEC_LOGIN_USER: + * uid=<uid> + * + * For TEEC_LOGIN_GROUP: + * gid=<gid> + * + */ + + name = kzalloc(TEE_UUID_NS_NAME_SIZE, GFP_KERNEL); + if (!name) + return -ENOMEM; + + switch (connection_method) { + case TEE_IOCTL_LOGIN_USER: + name_len = snprintf(name, TEE_UUID_NS_NAME_SIZE, "uid=%x", + current_euid().val); + if (name_len >= TEE_UUID_NS_NAME_SIZE) { + rc = -E2BIG; + goto out_free_name; + } + break; + + case TEE_IOCTL_LOGIN_GROUP: + memcpy(&ns_grp, connection_data, sizeof(gid_t)); + grp = make_kgid(current_user_ns(), ns_grp); + if (!gid_valid(grp) || !in_egroup_p(grp)) { + rc = -EPERM; + goto out_free_name; + } + + name_len = snprintf(name, TEE_UUID_NS_NAME_SIZE, "gid=%x", + grp.val); + if (name_len >= TEE_UUID_NS_NAME_SIZE) { + rc = -E2BIG; + goto out_free_name; + } + break; + + default: + rc = -EINVAL; + goto out_free_name; + } + + rc = uuid_v5(uuid, &tee_client_uuid_ns, name, name_len); +out_free_name: + kfree(name); + + return rc; +} +EXPORT_SYMBOL_GPL(tee_session_calc_client_uuid); + static int tee_ioctl_version(struct tee_context *ctx, struct tee_ioctl_version_data __user *uvers) { diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h index 1412e9cc79ce..8471b790e858 100644 --- a/include/linux/tee_drv.h +++ b/include/linux/tee_drv.h @@ -165,6 +165,22 @@ int tee_device_register(struct tee_device *teedev); */ void tee_device_unregister(struct tee_device *teedev);

+/** + * tee_session_calc_client_uuid() - Calculates client UUID for session + * @uuid: Resulting UUID + * @connection_method: Connection method for session (TEE_IOCTL_LOGIN_*) + * @connectuon_data: Connection data for opening session + * + * Based on connection method calculates UUIDv5 based client UUID. + * + * For group based logins verifies that calling process has specified + * credentials. + * + * @return < 0 on failure + */ +int tee_session_calc_client_uuid(uuid_t *uuid, u32 connection_method, + const u8 connection_data[TEE_IOCTL_UUID_LEN]); + /** * struct tee_shm - shared memory object * @ctx: context using the object

Linux kernel does not provide common contex for application identifier, instead different security frameworks provide own means to define application identifier for running process. Code includes place holder for such solutions but is left for later implementation.

Open questions:

1. App ID source

How to specify what source is used for app id?

Does it need to be protected on runtime? - Should this be Kconfig setting? - Cnfigure once during runtime thru sysfs or so? - Configure from device tree?

2. Formatting for App ID

Should there be common format? Or common keyword id?

3. How to handle custom App ID sources

Android has own App ID so does Tizen.

Should there be place holder for this where to make local patch?

Signed-off-by: Vesa Jääskeläinen vesa.jaaskelainen@vaisala.com --- drivers/tee/tee_core.c | 58 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+)

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c index d5db206d6af2..35ea20a99b9e 100644 --- a/drivers/tee/tee_core.c +++ b/drivers/tee/tee_core.c @@ -125,6 +125,15 @@ static int tee_release(struct inode *inode, struct file *filp) return 0; }

+static const char *tee_session_get_application_id(void) +{ + return NULL; +} + +static void tee_session_free_application_id(const char *app_id) +{ +} + /** * uuid_v5() - Calculate UUIDv5 * @uuid: Resulting UUID @@ -218,6 +227,14 @@ int tee_session_calc_client_uuid(uuid_t *uuid, u32 connection_method, * For TEEC_LOGIN_GROUP: * gid=<gid> * + * For TEEC_LOGIN_APPLICATION: + * app=<application id> + * + * For TEEC_LOGIN_USER_APPLICATION: + * uid=<uid>:app=<application id> + * + * For TEEC_LOGIN_GROUP_APPLICATION: + * gid=<gid>:app=<application id> */

name = kzalloc(TEE_UUID_NS_NAME_SIZE, GFP_KERNEL); @@ -250,6 +267,47 @@ int tee_session_calc_client_uuid(uuid_t *uuid, u32 connection_method, } break;

+ case TEE_IOCTL_LOGIN_APPLICATION: + application_id = tee_session_get_application_id(); + name_len = snprintf(name, TEE_UUID_NS_NAME_SIZE, "app=%s", + application_id); + tee_session_free_application_id(application_id); + if (name_len >= TEE_UUID_NS_NAME_SIZE) { + rc = -E2BIG; + goto out_free_name; + } + break; + + case TEE_IOCTL_LOGIN_USER_APPLICATION: + application_id = tee_session_get_application_id(); + name_len = snprintf(name, TEE_UUID_NS_NAME_SIZE, + "uid=%x:app=%s", current_euid().val, + application_id); + tee_session_free_application_id(application_id); + if (name_len >= TEE_UUID_NS_NAME_SIZE) { + rc = -E2BIG; + goto out_free_name; + } + break; + + case TEE_IOCTL_LOGIN_GROUP_APPLICATION: + memcpy(&ns_grp, connection_data, sizeof(gid_t)); + grp = make_kgid(current_user_ns(), ns_grp); + if (!gid_valid(grp) || !in_egroup_p(grp)) { + rc = -EPERM; + goto out_free_name; + } + + application_id = tee_session_get_application_id(); + name_len = snprintf(name, TEE_UUID_NS_NAME_SIZE, + "gid=%x:app=%s", grp.val, application_id); + tee_session_free_application_id(application_id); + if (name_len >= TEE_UUID_NS_NAME_SIZE) { + rc = -E2BIG; + goto out_free_name; + } + break; + default: rc = -EINVAL; goto out_free_name;