From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Wiklander To: op-tee@lists.trustedfirmware.org Subject: Re: [RFC PATCH] tee: add support for application-based session login methods Date: Mon, 28 Sep 2020 15:43:47 +0200 Message-ID: <20200928134347.GA76106@jade> In-Reply-To: <20200917183803.4a0c5263@akathisia> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0562570478278028591==" List-Id: --===============0562570478278028591== Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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. >=20 > 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. >=20 > 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. >=20 > Signed-off-by: Elvira Khabirova > --- > drivers/tee/Kconfig | 29 +++++++++ > drivers/tee/tee_core.c | 136 ++++++++++++++++++++++++++++++++++++++++- > 2 files changed, 164 insertions(+), 1 deletion(-) >=20 > 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). > =20 > +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 rem= oved). > + > if TEE > =20 > 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 @@ > =20 > #include > #include > +#include > #include > #include > +#include > #include > #include > #include > @@ -17,11 +19,15 @@ > #include > #include "tee_private.h" > =20 > +#ifdef CONFIG_TEE_APPID_SECURITY No need for the ifdef, just inlude the file unconditionally above. > +#include > +#endif > + > #define TEE_NUM_DEVICES 32 > =20 > #define TEE_IOCTL_PARAM_SIZE(x) (sizeof(struct tee_param) * (x)) > =20 > -#define TEE_UUID_NS_NAME_SIZE 128 > +#define TEE_UUID_NS_NAME_SIZE PATH_MAX > =20 > /* > * TEE Client UUID name space identifier (UUIDv4) > @@ -125,6 +131,67 @@ static int tee_release(struct inode *inode, struct fil= e *filp) > return 0; > } > =20 > +#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 =3D CONFIG_TEE_APPID_SECURITY_XATTR; > + int len; > + > + exe_file =3D 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 =3D 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 =3D kzalloc(TEE_UUID_NS_NAME_SIZE, GFP_KERNEL); > + if (!*data) > + return ERR_PTR(-ENOMEM); > + > + exe_file =3D get_mm_exe_file(current->mm); > + if (!exe_file) { > + kfree(*data); > + return ERR_PTR(-ENOENT); > + } > + > + path =3D 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 conn= ection_method, > gid_t ns_grp =3D (gid_t)-1; > kgid_t grp =3D INVALID_GID; > char *name =3D NULL; > + void *application_id_data =3D NULL; This isn't needed > + const char *application_id =3D NULL; char *app_id =3D NULL; > int name_len; > int rc; > =20 > @@ -217,6 +286,14 @@ int tee_session_calc_client_uuid(uuid_t *uuid, u32 con= nection_method, > * For TEEC_LOGIN_GROUP: > * gid=3D > * > + * For TEEC_LOGIN_APPLICATION: > + * app=3D > + * > + * For TEEC_LOGIN_USER_APPLICATION: > + * uid=3D:app=3D > + * > + * For TEEC_LOGIN_GROUP_APPLICATION: > + * gid=3D:app=3D > */ > =20 > name =3D kzalloc(TEE_UUID_NS_NAME_SIZE, GFP_KERNEL); > @@ -249,6 +326,63 @@ int tee_session_calc_client_uuid(uuid_t *uuid, u32 con= nection_method, > } > break; > =20 > + case TEE_IOCTL_LOGIN_APPLICATION: > + application_id =3D tee_session_get_application_id(&application_id_data); > + if (IS_ERR(application_id)) { > + rc =3D PTR_ERR(application_id); > + goto out_free_name; > + } > + > + name_len =3D snprintf(name, TEE_UUID_NS_NAME_SIZE, "app=3D%s", > + application_id); > + tee_session_free_application_id(application_id_data); > + > + if (name_len >=3D TEE_UUID_NS_NAME_SIZE) { > + rc =3D -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 =3D uuid_v5(uuid, &tee_client_uuid_ns, name, name_len); else rc =3D -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 =3D tee_session_get_application_id(&application_id_data); > + if (IS_ERR(application_id)) { > + rc =3D PTR_ERR(application_id); > + goto out_free_name; > + } > + > + name_len =3D snprintf(name, TEE_UUID_NS_NAME_SIZE, "uid=3D%x:app=3D%s", > + current_euid().val, application_id); > + tee_session_free_application_id(application_id_data); > + > + if (name_len >=3D TEE_UUID_NS_NAME_SIZE) { > + rc =3D -E2BIG; > + goto out_free_name; > + } > + break; > + > + case TEE_IOCTL_LOGIN_GROUP_APPLICATION: > + memcpy(&ns_grp, connection_data, sizeof(gid_t)); > + grp =3D make_kgid(current_user_ns(), ns_grp); > + if (!gid_valid(grp) || !in_egroup_p(grp)) { > + rc =3D -EPERM; > + goto out_free_name; > + } > + > + application_id =3D tee_session_get_application_id(&application_id_data); > + if (IS_ERR(application_id)) { > + rc =3D PTR_ERR(application_id); > + goto out_free_name; > + } > + name_len =3D snprintf(name, TEE_UUID_NS_NAME_SIZE, "gid=3D%x:app=3D%s", > + grp.val, application_id); > + tee_session_free_application_id(application_id_data); > + > + if (name_len >=3D TEE_UUID_NS_NAME_SIZE) { > + rc =3D -E2BIG; > + goto out_free_name; > + } > + break; > + > default: > rc =3D -EINVAL; > goto out_free_name; > --=20 > 2.28.0 >=20 --===============0562570478278028591==--