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The pseries platform can support dynamic secure boot (i.e. secure boot using user-defined keys) using variables contained with the PowerVM LPAR Platform KeyStore (PLPKS). Using the powerpc secvar API, expose the relevant variables for pseries dynamic secure boot through the existing secvar filesystem layout. The relevant variables for dynamic secure boot are signed in the keystore, and can only be modified using the H_PKS_SIGNED_UPDATE hcall. Object labels in the keystore are encoded using ucs2 format. With our fixed variable names we don't have to care about encoding outside of the necessary byte padding. When a user writes to a variable, the first 8 bytes of data must contain the signed update flags as defined by the hypervisor. When a user reads a variable, the first 4 bytes of data contain the policies defined for the object. Limitations exist due to the underlying implementation of sysfs binary attributes, as is the case for the OPAL secvar implementation - partial writes are unsupported and writes cannot be larger than PAGE_SIZE. (Even when using bin_attributes, which can be larger than a single page, sysfs only gives us one page's worth of write buffer at a time, and the hypervisor does not expose an interface for partial writes.) Co-developed-by: Nayna Jain <nayna@linux.ibm.com> Signed-off-by: Nayna Jain <nayna@linux.ibm.com> Co-developed-by: Andrew Donnellan <ajd@linux.ibm.com> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com> Signed-off-by: Russell Currey <ruscur@russell.cc> [mpe: Add NLS dependency to fix build errors, squash fix from ajd] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20230210080401.345462-25-ajd@linux.ibm.com
120 lines
4.6 KiB
Plaintext
120 lines
4.6 KiB
Plaintext
What: /sys/firmware/secvar
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Date: August 2019
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: This directory is created if the POWER firmware supports OS
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secureboot, thereby secure variables. It exposes interface
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for reading/writing the secure variables
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What: /sys/firmware/secvar/vars
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Date: August 2019
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: This directory lists all the secure variables that are supported
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by the firmware.
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What: /sys/firmware/secvar/format
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Date: August 2019
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: A string indicating which backend is in use by the firmware.
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This determines the format of the variable and the accepted
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format of variable updates.
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On powernv/OPAL, this value is provided by the OPAL firmware
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and is expected to be "ibm,edk2-compat-v1".
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On pseries/PLPKS, this is generated by the kernel based on the
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version number in the SB_VERSION variable in the keystore, and
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has the form "ibm,plpks-sb-v<version>", or
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"ibm,plpks-sb-unknown" if there is no SB_VERSION variable.
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What: /sys/firmware/secvar/vars/<variable name>
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Date: August 2019
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: Each secure variable is represented as a directory named as
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<variable_name>. The variable name is unique and is in ASCII
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representation. The data and size can be determined by reading
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their respective attribute files.
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What: /sys/firmware/secvar/vars/<variable_name>/size
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Date: August 2019
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: An integer representation of the size of the content of the
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variable. In other words, it represents the size of the data.
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What: /sys/firmware/secvar/vars/<variable_name>/data
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Date: August 2019
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: A read-only file containing the value of the variable. The size
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of the file represents the maximum size of the variable data.
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What: /sys/firmware/secvar/vars/<variable_name>/update
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Date: August 2019
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: A write-only file that is used to submit the new value for the
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variable. The size of the file represents the maximum size of
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the variable data that can be written.
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What: /sys/firmware/secvar/config
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Date: February 2023
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: This optional directory contains read-only config attributes as
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defined by the secure variable implementation. All data is in
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ASCII format. The directory is only created if the backing
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implementation provides variables to populate it, which at
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present is only PLPKS on the pseries platform.
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What: /sys/firmware/secvar/config/version
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Date: February 2023
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: Config version as reported by the hypervisor in ASCII decimal
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format.
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Currently only provided by PLPKS on the pseries platform.
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What: /sys/firmware/secvar/config/max_object_size
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Date: February 2023
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: Maximum allowed size of objects in the keystore in bytes,
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represented in ASCII decimal format.
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This is not necessarily the same as the max size that can be
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written to an update file as writes can contain more than
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object data, you should use the size of the update file for
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that purpose.
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Currently only provided by PLPKS on the pseries platform.
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What: /sys/firmware/secvar/config/total_size
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Date: February 2023
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: Total size of the PLPKS in bytes, represented in ASCII decimal
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format.
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Currently only provided by PLPKS on the pseries platform.
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What: /sys/firmware/secvar/config/used_space
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Date: February 2023
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: Current space consumed by the key store, in bytes, represented
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in ASCII decimal format.
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Currently only provided by PLPKS on the pseries platform.
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What: /sys/firmware/secvar/config/supported_policies
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Date: February 2023
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: Bitmask of supported policy flags by the hypervisor,
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represented as an 8 byte hexadecimal ASCII string. Consult the
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hypervisor documentation for what these flags are.
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Currently only provided by PLPKS on the pseries platform.
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What: /sys/firmware/secvar/config/signed_update_algorithms
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Date: February 2023
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Contact: Nayna Jain <nayna@linux.ibm.com>
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Description: Bitmask of flags indicating which algorithms the hypervisor
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supports for signed update of objects, represented as a 16 byte
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hexadecimal ASCII string. Consult the hypervisor documentation
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for what these flags mean.
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Currently only provided by PLPKS on the pseries platform.
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