51 lines
2.1 KiB
ReStructuredText
51 lines
2.1 KiB
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=============================================
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Virtual TPM Proxy Driver for Linux Containers
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=============================================
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| Authors:
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| Stefan Berger <stefanb@linux.vnet.ibm.com>
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This document describes the virtual Trusted Platform Module (vTPM)
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proxy device driver for Linux containers.
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Introduction
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============
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The goal of this work is to provide TPM functionality to each Linux
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container. This allows programs to interact with a TPM in a container
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the same way they interact with a TPM on the physical system. Each
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container gets its own unique, emulated, software TPM.
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Design
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======
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To make an emulated software TPM available to each container, the container
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management stack needs to create a device pair consisting of a client TPM
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character device ``/dev/tpmX`` (with X=0,1,2...) and a 'server side' file
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descriptor. The former is moved into the container by creating a character
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device with the appropriate major and minor numbers while the file descriptor
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is passed to the TPM emulator. Software inside the container can then send
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TPM commands using the character device and the emulator will receive the
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commands via the file descriptor and use it for sending back responses.
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To support this, the virtual TPM proxy driver provides a device ``/dev/vtpmx``
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that is used to create device pairs using an ioctl. The ioctl takes as
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an input flags for configuring the device. The flags for example indicate
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whether TPM 1.2 or TPM 2 functionality is supported by the TPM emulator.
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The result of the ioctl are the file descriptor for the 'server side'
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as well as the major and minor numbers of the character device that was created.
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Besides that the number of the TPM character device is returned. If for
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example ``/dev/tpm10`` was created, the number (``dev_num``) 10 is returned.
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Once the device has been created, the driver will immediately try to talk
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to the TPM. All commands from the driver can be read from the file descriptor
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returned by the ioctl. The commands should be responded to immediately.
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UAPI
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====
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.. kernel-doc:: include/uapi/linux/vtpm_proxy.h
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.. kernel-doc:: drivers/char/tpm/tpm_vtpm_proxy.c
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:functions: vtpmx_ioc_new_dev
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