1 ============================================= 2 Virtual TPM Proxy Driver for Linux Containers 3 ============================================= 4 5 | Authors: 6 | Stefan Berger <stefanb@linux.vnet.ibm.com> 7 8 This document describes the virtual Trusted Platform Module (vTPM) 9 proxy device driver for Linux containers. 10 11 Introduction 12 ============ 13 14 The goal of this work is to provide TPM functionality to each Linux 15 container. This allows programs to interact with a TPM in a container 16 the same way they interact with a TPM on the physical system. Each 17 container gets its own unique, emulated, software TPM. 18 19 Design 20 ====== 21 22 To make an emulated software TPM available to each container, the container 23 management stack needs to create a device pair consisting of a client TPM 24 character device ``/dev/tpmX`` (with X=0,1,2...) and a 'server side' file 25 descriptor. The former is moved into the container by creating a character 26 device with the appropriate major and minor numbers while the file descriptor 27 is passed to the TPM emulator. Software inside the container can then send 28 TPM commands using the character device and the emulator will receive the 29 commands via the file descriptor and use it for sending back responses. 30 31 To support this, the virtual TPM proxy driver provides a device ``/dev/vtpmx`` 32 that is used to create device pairs using an ioctl. The ioctl takes as 33 an input flags for configuring the device. The flags for example indicate 34 whether TPM 1.2 or TPM 2 functionality is supported by the TPM emulator. 35 The result of the ioctl are the file descriptor for the 'server side' 36 as well as the major and minor numbers of the character device that was created. 37 Besides that the number of the TPM character device is returned. If for 38 example ``/dev/tpm10`` was created, the number (``dev_num``) 10 is returned. 39 40 Once the device has been created, the driver will immediately try to talk 41 to the TPM. All commands from the driver can be read from the file descriptor 42 returned by the ioctl. The commands should be responded to immediately. 43 44 UAPI 45 ==== 46 47 .. kernel-doc:: include/uapi/linux/vtpm_proxy.h 48 49 .. kernel-doc:: drivers/char/tpm/tpm_vtpm_proxy.c 50 :functions: vtpmx_ioc_new_dev
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