[PATCH v9 0/4] powerpc: expose secure variables to the kernel and userspace

From: Nayna Jain
Date: Sun Nov 10 2019 - 22:10:55 EST

In order to verify the OS kernel on PowerNV systems, secure boot requires
X.509 certificates trusted by the platform. These are stored in secure
variables controlled by OPAL, called OPAL secure variables. In order to
enable users to manage the keys, the secure variables need to be exposed
to userspace.

OPAL provides the runtime services for the kernel to be able to access the
secure variables[1]. This patchset defines the kernel interface for the
OPAL APIs. These APIs are used by the hooks, which load these variables
to the keyring and expose them to the userspace for reading/writing.

The previous version[2] of the patchset added support only for the sysfs
interface. This patch adds two more patches that involves loading of
the firmware trusted keys to the kernel keyring.

Overall, this patchset adds the following support:

* expose secure variables to the kernel via OPAL Runtime API interface
* expose secure variables to the userspace via kernel sysfs interface
* load kernel verification and revocation keys to .platform and
.blacklist keyring respectively.

The secure variables can be read/written using simple linux utilities
cat/hexdump.

For example:
Path to the secure variables is:
/sys/firmware/secvar/vars

Each secure variable is listed as directory.
$ ls -l
total 0
drwxr-xr-x. 2 root root 0 Aug 20 21:20 db
drwxr-xr-x. 2 root root 0 Aug 20 21:20 KEK
drwxr-xr-x. 2 root root 0 Aug 20 21:20 PK

The attributes of each of the secure variables are(for example: PK):
[db]$ ls -l
total 0
-r--r--r--. 1 root root 4096 Oct 1 15:10 data
-r--r--r--. 1 root root 65536 Oct 1 15:10 size
--w-------. 1 root root 4096 Oct 1 15:12 update

The "data" is used to read the existing variable value using hexdump. The
data is stored in ESL format.
The "update" is used to write a new value using cat. The update is
to be submitted as AUTH file.

[1] Depends on skiboot OPAL API changes which removes metadata from
the API. https://lists.ozlabs.org/pipermail/skiboot/2019-September/015203.html.
[2] https://lkml.org/lkml/2019/6/13/1644

Changelog:
v9:
* Updated Patch 1,2,4 to search secvar device tree node based on
generic compatible string.
* Renamed "backend" attribute to "format" attribute, and updated it
with the value of "format" property of secvar backend
* Updated Patch 4/4 to look for "format" property to ensure
edk2-compat-v1 variables format

v8
* rebased on v5.4-rc6
* Patch 2 related to sysfs
* fixed error message as per Greg's feedback
* fixed minor formatting
* renamed error code from ret to rc in backend_show()
* Patch 4 - loading of keys to keyring
* as per Michael's feedback, removed select for LOAD_PPC_KEYS, instead
made it default "yes" if the pre-requisites are satisfied
* fixed an error message for more clarity

v7 (on behalf of Nayna, by Eric Richter):
* secvar-sysfs now a bool rather than a tristate option
* added documentation for backend sysfs entry

v6 (on behalf of Nayna, by Eric Richter):
* updated device tree layout
* secvar node now sets compatible based on backend
* all ibm,secvar-v1 compatible-checking code checks for
ibm,edk2-compat-v1
* added backend attribute to secvar-sysfs to expose backend version to
userspace
* loading certs from db now depends on backend (not all backends may
have a "db")
* fixed device node leaks
* fixed leaking string on early exit

v5:
* rebased to v5.4-rc3
* includes Oliver's feedbacks
* changed OPAL API as platform driver
* sysfs are made default enabled and dependent on PPC_SECURE_BOOT
* fixed code specific changes in both OPAL API and sysfs
* reading size of the "data" and "update" file from device-tree.
* fixed sysfs documentation to also reflect the data and update file
size interpretation
* This patchset is no more dependent on ima-arch/blacklist patchset

v4:
* rebased to v5.4-rc1
* uses __BIN_ATTR_WO macro to create binary attribute as suggested by
Greg
* removed email id from the file header
* renamed argument keysize to keybufsize in get_next() function
* updated default binary file sizes to 0, as firmware handles checking
against the maximum size
* fixed minor formatting issues in Patch 4/4
* added Greg's and Mimi's Reviewed-by and Ack-by

v3:
* includes Greg's feedbacks:
* fixes in Patch 2/4
* updates the Documentation.
* fixes code feedbacks
* adds SYSFS Kconfig dependency for SECVAR_SYSFS
* fixes mixed tabs and spaces
* removes "name" attribute for each of the variable name based
directories
* fixes using __ATTR_RO() and __BIN_ATTR_RO() and statics and const
* fixes the racing issue by using kobj_type default groups. Also,
fixes the kobject leakage.
* removes extra print messages
* updates patch description for Patch 3/4
* removes file name from Patch 4/4 file header comment and removed
def_bool y from the LOAD_PPC_KEYS Kconfig

* includes Oliver's feedbacks:
* fixes Patch 1/2
* moves OPAL API wrappers after opal_nx_proc_init(), fixed the
naming, types and removed extern.
* fixes spaces
* renames get_variable() to get(), get_next_variable() to get_next()
and set_variable() to set()
* removed get_secvar_ops() and defined secvar_ops as global
* fixes consts and statics
* removes generic secvar_init() and defined platform specific
opal_secar_init()
* updates opal_secvar_supported() to check for secvar support even
before checking the OPAL APIs support and also fixed the error codes.
* addes function that converts OPAL return codes to linux errno
* moves secvar check support in the opal_secvar_init() and defined its
prototype in opal.h
* fixes Patch 2/2
* fixes static/const
* defines macro for max name size
* replaces OPAL error codes with linux errno and also updated error
handling
* moves secvar support check before creating sysfs kobjects in
secvar_sysfs_init()
* fixes spaces

v2:
* removes complete efi-sms from the sysfs implementation and is simplified
* includes Greg's and Oliver's feedbacks:
* adds sysfs documentation
* moves sysfs code to arch/powerpc
* other code related feedbacks.
* adds two new patches to load keys to .platform and .blacklist keyring.
These patches are added to this series as they are also dependent on
OPAL APIs.

Nayna Jain (4):
powerpc/powernv: Add OPAL API interface to access secure variable
powerpc: expose secure variables to userspace via sysfs
x86/efi: move common keyring handler functions to new file
powerpc: load firmware trusted keys/hashes into kernel keyring

Documentation/ABI/testing/sysfs-secvar | 46 ++++
arch/powerpc/Kconfig | 11 +
arch/powerpc/include/asm/opal-api.h | 5 +-
arch/powerpc/include/asm/opal.h | 7 +
arch/powerpc/include/asm/secvar.h | 35 +++
arch/powerpc/kernel/Makefile | 3 +-
arch/powerpc/kernel/secvar-ops.c | 16 ++
arch/powerpc/kernel/secvar-sysfs.c | 248 +++++++++++++++++++++
arch/powerpc/platforms/powernv/Makefile | 2 +-
arch/powerpc/platforms/powernv/opal-call.c | 3 +
arch/powerpc/platforms/powernv/opal-secvar.c | 140 ++++++++++++
arch/powerpc/platforms/powernv/opal.c | 3 +
security/integrity/Kconfig | 9 +
security/integrity/Makefile | 7 +-
.../integrity/platform_certs/keyring_handler.c | 80 +++++++
.../integrity/platform_certs/keyring_handler.h | 32 +++
security/integrity/platform_certs/load_powerpc.c | 99 ++++++++
security/integrity/platform_certs/load_uefi.c | 67 +-----
18 files changed, 742 insertions(+), 71 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-secvar
create mode 100644 arch/powerpc/include/asm/secvar.h
create mode 100644 arch/powerpc/kernel/secvar-ops.c
create mode 100644 arch/powerpc/kernel/secvar-sysfs.c
create mode 100644 arch/powerpc/platforms/powernv/opal-secvar.c
create mode 100644 security/integrity/platform_certs/keyring_handler.c
create mode 100644 security/integrity/platform_certs/keyring_handler.h
create mode 100644 security/integrity/platform_certs/load_powerpc.c

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2.13.6