lkml.org 
[lkml]   [2020]   [Sep]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH] tee: add support for application-based session login methods
Hi Elvira,

On Thu, Sep 17, 2020 at 06:38:03PM +0300, Elvira Khabirova wrote:
> GP TEE Client API in addition to login methods already supported
> in the kernel also defines several application-based methods:
> TEEC_LOGIN_APPLICATION, TEEC_LOGIN_USER_APPLICATION, and
> TEEC_LOGIN_GROUP_APPLICATION.
>
> It specifies credentials generated for TEEC_LOGIN_APPLICATION as only
> depending on the identity of the program, being persistent within one
> implementation, across multiple invocations of the application
> and across power cycles, enabling them to be used to disambiguate
> persistent storage. The exact nature is REE-specific.
>
> As the exact method of generating application identifier strings may
> vary between vendors, setups and installations, add two suggested
> methods and an exact framework for vendors to extend upon.
>
> Signed-off-by: Elvira Khabirova <e.khabirova@omprussia.ru>
> ---
> drivers/tee/Kconfig | 29 +++++++++
> drivers/tee/tee_core.c | 136 ++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 164 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tee/Kconfig b/drivers/tee/Kconfig
> index e99d840c2511..4cd6e0d2aad5 100644
> --- a/drivers/tee/Kconfig
> +++ b/drivers/tee/Kconfig
> @@ -11,6 +11,35 @@ config TEE
> This implements a generic interface towards a Trusted Execution
> Environment (TEE).
>
> +choice
> + prompt "Application ID for client UUID"
> + depends on TEE
> + default TEE_APPID_PATH
> + help
> + This option allows to choose which method will be used to generate
> + application identifiers for client UUID generation when login methods
> + TEE_LOGIN_APPLICATION, TEE_LOGIN_USER_APPLICATION
> + and TEE_LOGIN_GROUP_APPLICATION are used.
> + Please be mindful of the security of each method in your particular
> + installation.
> +
> + config TEE_APPID_PATH
> + bool "Path-based application ID"
> + help
> + Use the executable's path as an application ID.
> +
> + config TEE_APPID_SECURITY
> + bool "Security extended attribute based application ID"
> + help
> + Use the executable's security extended attribute as an application ID.
> +endchoice
> +
> +config TEE_APPID_SECURITY_XATTR
> + string "Security extended attribute to use for application ID"
> + depends on TEE_APPID_SECURITY
> + help
> + Attribute to be used as an application ID (with the security prefix removed).
> +
> if TEE
>
> menu "TEE drivers"
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index 64637e09a095..19c965dd212b 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -7,8 +7,10 @@
>
> #include <linux/cdev.h>
> #include <linux/cred.h>
> +#include <linux/file.h>
> #include <linux/fs.h>
> #include <linux/idr.h>
> +#include <linux/mm.h>
> #include <linux/module.h>
> #include <linux/slab.h>
> #include <linux/tee_drv.h>
> @@ -17,11 +19,15 @@
> #include <crypto/sha.h>
> #include "tee_private.h"
>
> +#ifdef CONFIG_TEE_APPID_SECURITY
No need for the ifdef, just inlude the file unconditionally above.

> +#include <linux/security.h>
> +#endif
> +
> #define TEE_NUM_DEVICES 32
>
> #define TEE_IOCTL_PARAM_SIZE(x) (sizeof(struct tee_param) * (x))
>
> -#define TEE_UUID_NS_NAME_SIZE 128
> +#define TEE_UUID_NS_NAME_SIZE PATH_MAX
>
> /*
> * TEE Client UUID name space identifier (UUIDv4)
> @@ -125,6 +131,67 @@ static int tee_release(struct inode *inode, struct file *filp)
> return 0;
> }
>
> +#ifdef CONFIG_TEE_APPID_SECURITY
> +static const char *tee_session_get_application_id(void **data)
static char *get_app_id(void) should be enough.

> +{
> + struct file *exe_file;
> + const char *name = CONFIG_TEE_APPID_SECURITY_XATTR;
> + int len;
> +
> + exe_file = get_mm_exe_file(current->mm);
> + if (!exe_file)
> + return ERR_PTR(-ENOENT);
> +
> + if (!exe_file->f_inode) {
> + fput(exe_file);
> + return ERR_PTR(-ENOENT);
> + }
> +

You could perhaps add a comment here on the expected properties of this
data. Something along (don't know if I'm even close) "string
representation of the the hash of the binary and time stamp".

> + len = security_inode_getsecurity(exe_file->f_inode, name, data, true);
> + if (len < 0)
> + return ERR_PTR(len);
> +
> + fput(exe_file);
> +
> + return *data;
> +}
> +#endif /* CONFIG_TEE_APPID_SECURITY */
> +
> +#ifdef CONFIG_TEE_APPID_PATH
> +static const char *tee_session_get_application_id(void **data)
> +{
> + struct file *exe_file;
> + char *path;
> +
> + *data = kzalloc(TEE_UUID_NS_NAME_SIZE, GFP_KERNEL);
> + if (!*data)
> + return ERR_PTR(-ENOMEM);
> +
> + exe_file = get_mm_exe_file(current->mm);
> + if (!exe_file) {
> + kfree(*data);
> + return ERR_PTR(-ENOENT);
> + }
> +
> + path = file_path(exe_file, *data, TEE_UUID_NS_NAME_SIZE);
> + if (IS_ERR(path)) {
> + kfree(*data);
> + return path;
> + }
> +
> + fput(exe_file);
> +
> + return path;
> +}
> +#endif /* CONFIG_TEE_APPID_PATH */
> +
> +#if defined(CONFIG_TEE_APPID_PATH) || defined(CONFIG_TEE_APPID_SECURITY)
> +static void tee_session_free_application_id(void *data)
> +{
> + kfree(data);
> +}
This function isn't needed, we can call kfree() directly.

> +#endif /* CONFIG_TEE_APPID_PATH || CONFIG_TEE_APPID_SECURITY */
> +
> /**
> * uuid_v5() - Calculate UUIDv5
> * @uuid: Resulting UUID
> @@ -197,6 +264,8 @@ int tee_session_calc_client_uuid(uuid_t *uuid, u32 connection_method,
> gid_t ns_grp = (gid_t)-1;
> kgid_t grp = INVALID_GID;
> char *name = NULL;
> + void *application_id_data = NULL;
This isn't needed

> + const char *application_id = NULL;
char *app_id = NULL;

> int name_len;
> int rc;
>
> @@ -217,6 +286,14 @@ 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);
> @@ -249,6 +326,63 @@ 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(&application_id_data);
> + if (IS_ERR(application_id)) {
> + rc = PTR_ERR(application_id);
> + goto out_free_name;
> + }
> +
> + name_len = snprintf(name, TEE_UUID_NS_NAME_SIZE, "app=%s",
> + application_id);
> + tee_session_free_application_id(application_id_data);
> +
> + if (name_len >= TEE_UUID_NS_NAME_SIZE) {
> + rc = -E2BIG;
> + goto out_free_name;
> + }
It looks like we remove these tests and replace them with
if (name_len < TEE_UUID_NS_NAME_SIZE)
rc = uuid_v5(uuid, &tee_client_uuid_ns, name, name_len);
else
rc = -E2BIG

below, just above the "out_free_name:" label.

This function is small and simple enough that it should be easy to see
what's going on any way.

Thanks,
Jens

> + break;
> +
> + case TEE_IOCTL_LOGIN_USER_APPLICATION:
> + application_id = tee_session_get_application_id(&application_id_data);
> + if (IS_ERR(application_id)) {
> + rc = PTR_ERR(application_id);
> + goto out_free_name;
> + }
> +
> + 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_data);
> +
> + 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(&application_id_data);
> + if (IS_ERR(application_id)) {
> + rc = PTR_ERR(application_id);
> + goto out_free_name;
> + }
> + name_len = snprintf(name, TEE_UUID_NS_NAME_SIZE, "gid=%x:app=%s",
> + grp.val, application_id);
> + tee_session_free_application_id(application_id_data);
> +
> + if (name_len >= TEE_UUID_NS_NAME_SIZE) {
> + rc = -E2BIG;
> + goto out_free_name;
> + }
> + break;
> +
> default:
> rc = -EINVAL;
> goto out_free_name;
> --
> 2.28.0
>

\
 
 \ /
  Last update: 2020-09-28 15:44    [W:0.054 / U:0.776 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site