[v2,0/4] powerpc: expose secure variables to the kernel and userspace

Message

Nayna Jain Aug. 21, 2019, 3:08 p.m. UTC

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. This patchset is
dependent on the base CONFIG PPC_SECURE_BOOT added by ima arch specific
patches for POWER[3]

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):
[PK]$ ls -l
total 0
-r--r--r--. 1 root root 32000 Aug 21 08:28 data
-r--r--r--. 1 root root 65536 Aug 21 08:28 name
-r--r--r--. 1 root root 65536 Aug 21 08:28 size
--w-------. 1 root root 32000 Aug 21 08:28 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. The new version with the changes are going to be posted soon.
[2] https://lkml.org/lkml/2019/6/13/1644
[3] https://lkml.org/lkml/2019/8/19/402

Changelog:

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 into kernel keyring

 Documentation/ABI/testing/sysfs-secvar        |  27 +++
 arch/powerpc/Kconfig                          |   9 +
 arch/powerpc/include/asm/opal-api.h           |   5 +-
 arch/powerpc/include/asm/opal.h               |   6 +
 arch/powerpc/include/asm/secvar.h             |  55 +++++
 arch/powerpc/kernel/Makefile                  |   3 +-
 arch/powerpc/kernel/secvar-ops.c              |  25 +++
 arch/powerpc/kernel/secvar-sysfs.c            | 210 ++++++++++++++++++
 arch/powerpc/platforms/powernv/Kconfig        |   6 +
 arch/powerpc/platforms/powernv/Makefile       |   1 +
 arch/powerpc/platforms/powernv/opal-call.c    |   3 +
 arch/powerpc/platforms/powernv/opal-secvar.c  | 102 +++++++++
 arch/powerpc/platforms/powernv/opal.c         |   5 +
 security/integrity/Kconfig                    |   9 +
 security/integrity/Makefile                   |   6 +-
 .../platform_certs/keyring_handler.c          |  80 +++++++
 .../platform_certs/keyring_handler.h          |  35 +++
 .../integrity/platform_certs/load_powerpc.c   |  94 ++++++++
 security/integrity/platform_certs/load_uefi.c |  67 +-----
 19 files changed, 679 insertions(+), 69 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