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- =============================================
- Virtual TPM Proxy Driver for Linux Containers
- =============================================
- | Authors:
- | Stefan Berger <[email protected]>
- 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 returned. If for
- example ``/dev/tpm10`` was created, the number (``dev_num``) 10 is returned.
- 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.
- UAPI
- ====
- .. kernel-doc:: include/uapi/linux/vtpm_proxy.h
- .. kernel-doc:: drivers/char/tpm/tpm_vtpm_proxy.c
- :functions: vtpmx_ioc_new_dev
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