User Selected PCR Monitoring


This page is still under development and not complete. It will be so until this warning is removed.

Using use the tpm_policy feature in Keylime, it is possible to monitor a remote machine for any given PCR.

This can be used for Trusted Boot checks for both the rhboot shim loader and Trusted Grub 2.

How to use

Select which PCRs you would like Keylime to measure, by using the tpm2_pcrread from the tpm2-tools tool.

Now you can set the PCR values as a JSON data structure in either the keylime.conf file:

tpm_policy = {"22":["0000000000000000000000000000000000000001","0000000000000000000000000000000000000000000000000000000000000001","000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001","ffffffffffffffffffffffffffffffffffffffff","ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff","ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"],"15":["0000000000000000000000000000000000000000","0000000000000000000000000000000000000000000000000000000000000000","000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"]}

Or you can add a node to using keylime_tenant:

keylime_tenant -v -t -f /root/excludes.txt \
--uuid D432FBB3-D2F1-4A97-9EF7-75BD81C00000 \
--allowlist /root/allowlist.txt \
--exclude /root/exclude.txt \
--tpm_policy  {"22":["0000000000000000000000000000000000000001","0000000000000000000000000000000000000000000000000000000000000001","000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001","ffffffffffffffffffffffffffffffffffffffff","ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff","ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"],"15":["0000000000000000000000000000000000000000","0000000000000000000000000000000000000000000000000000000000000000","000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"]} \
-c add

rhboot shim-loader

The following is sourced from the rhboot shim repository please visit the upstream README to ensure information is still accurate

The following PCRs are extended by shim:

PCR4: - the Authenticode hash of the binary being loaded will be extended into

PCR4 before SB verification.

  • the hash of any binary for which Verify is called through the shim_lock protocol

PCR7: - Any certificate in one of our certificate databases that matches a binary

we try to load will be extended into PCR7. That includes: - DBX - the system denylist, logged as “dbx” - MokListX - the Mok denylist, logged as “MokListX” - vendor_dbx - shim’s built-in vendor denylist, logged as “dbx” - DB - the system allowlist, logged as “db” - MokList the Mok allowlist, logged as “MokList” - vendor_cert - shim’s built-in vendor allowlist, logged as “Shim” - shim_cert - shim’s build-time generated allowlist, logged as “Shim”

  • MokSBState will be extended into PCR7 if it is set, logged as “MokSBState”.

PCR8: - If you’re using the grub2 TPM patchset we cary in Fedora, the kernel command

line and all grub commands (including all of grub.cfg that gets run) are measured into PCR8.

PCR9: - If you’re using the grub2 TPM patchset we cary in Fedora, the kernel,

initramfs, and any multiboot modules loaded are measured into PCR9.

PCR14: - MokList, MokListX, and MokSBState will be extended into PCR14 if they are