mirror of https://gitee.com/openkylin/linux.git
72 lines
2.9 KiB
Plaintext
72 lines
2.9 KiB
Plaintext
Virtual TPM Proxy Driver for Linux Containers
|
|
|
|
Authors: Stefan Berger (IBM)
|
|
|
|
This document describes the virtual Trusted Platform Module (vTPM)
|
|
proxy device driver for Linux containers.
|
|
|
|
INTRODUCTION
|
|
------------
|
|
|
|
The goal of this work is to provide TPM functionality to each Linux
|
|
container. This allows programs to interact with a TPM in a container
|
|
the same way they interact with a TPM on the physical system. Each
|
|
container gets its own unique, emulated, software TPM.
|
|
|
|
|
|
DESIGN
|
|
------
|
|
|
|
To make an emulated software TPM available to each container, the container
|
|
management stack needs to create a device pair consisting of a client TPM
|
|
character device /dev/tpmX (with X=0,1,2...) and a 'server side' file
|
|
descriptor. The former is moved into the container by creating a character
|
|
device with the appropriate major and minor numbers while the file descriptor
|
|
is passed to the TPM emulator. Software inside the container can then send
|
|
TPM commands using the character device and the emulator will receive the
|
|
commands via the file descriptor and use it for sending back responses.
|
|
|
|
To support this, the virtual TPM proxy driver provides a device /dev/vtpmx
|
|
that is used to create device pairs using an ioctl. The ioctl takes as
|
|
an input flags for configuring the device. The flags for example indicate
|
|
whether TPM 1.2 or TPM 2 functionality is supported by the TPM emulator.
|
|
The result of the ioctl are the file descriptor for the 'server side'
|
|
as well as the major and minor numbers of the character device that was created.
|
|
Besides that the number of the TPM character device is return. If for
|
|
example /dev/tpm10 was created, the number (dev_num) 10 is returned.
|
|
|
|
The following is the data structure of the TPM_PROXY_IOC_NEW_DEV ioctl:
|
|
|
|
struct vtpm_proxy_new_dev {
|
|
__u32 flags; /* input */
|
|
__u32 tpm_num; /* output */
|
|
__u32 fd; /* output */
|
|
__u32 major; /* output */
|
|
__u32 minor; /* output */
|
|
};
|
|
|
|
Note that if unsupported flags are passed to the device driver, the ioctl will
|
|
fail and errno will be set to EOPNOTSUPP. Similarly, if an unsupported ioctl is
|
|
called on the device driver, the ioctl will fail and errno will be set to
|
|
ENOTTY.
|
|
|
|
See /usr/include/linux/vtpm_proxy.h for definitions related to the public interface
|
|
of this vTPM device driver.
|
|
|
|
Once the device has been created, the driver will immediately try to talk
|
|
to the TPM. All commands from the driver can be read from the file descriptor
|
|
returned by the ioctl. The commands should be responded to immediately.
|
|
|
|
Depending on the version of TPM the following commands will be sent by the
|
|
driver:
|
|
|
|
- TPM 1.2:
|
|
- the driver will send a TPM_Startup command to the TPM emulator
|
|
- the driver will send commands to read the command durations and
|
|
interface timeouts from the TPM emulator
|
|
- TPM 2:
|
|
- the driver will send a TPM2_Startup command to the TPM emulator
|
|
|
|
The TPM device /dev/tpmX will only appear if all of the relevant commands
|
|
were responded to properly.
|