tpm2_policypcr.1.md 3.0 KB
% tpm2_policypcr(1) tpm2-tools | General Commands Manual
NAME
tpm2_policypcr(1) - Create a policy that includes specific PCR values.
SYNOPSIS
tpm2_policypcr [OPTIONS]
DESCRIPTION
tpm2_policypcr(1) - Generates a PCR policy event with the TPM. A PCR policy event creates a policy bound to specific PCR values and is useful within larger policies constructed using policyor and policyauthorize events. See tpm2_policyor(1) and tpm2_policyauthorize(1) respectively for their usages. The PCR data factored into the policy can be specified in one of 3 ways:
- A file containing a concatenated list of PCR values as in the output from tpm2_pcrread.
- Requiring the PCR values be read off the TPM by not specifying a PCR file input.
- The digest of all the PCR values directly specified as an argument.
OPTIONS
-L, --policy=FILE:
File to save the policy digest.
-f, --pcr=FILE:
Optional Path or Name of the file containing expected PCR values for the specified index. Default is to read the current PCRs per the set list.
-l, --pcr-list=PCR:
The list of PCR banks and selected PCRs' ids for each bank.
-S, --session=FILE:
The policy session file generated via the -S option to tpm2_startauthsession(1).
ARGUMENT: The calculated digest of all PCR values specified as a hex byte stream. Eg:
openssl dgst -sha256 -binary pcr.bin | xxd -p -c 32
References
context object format details the methods for specifying OBJECT.
authorization formatting details the methods for specifying AUTH.
pcr bank specifiers details the syntax for specifying pcr list PCR.
common options collection of common options that provide information many users may expect.
common tcti options collection of options used to configure the various known TCTI modules.
EXAMPLES
Starts a trial session, builds a PCR policy and uses that policy in the creation of an object. Then, it uses a policy session to unseal some data stored in the object.
Step 1: create a policy
tpm2_createprimary -C e -g sha256 -G ecc -c primary.ctx
tpm2_pcrread -o pcr.dat "sha1:0,1,2,3"
tpm2_startauthsession -S session.dat
tpm2_policypcr -S session.dat -l "sha1:0,1,2,3" -f pcr.dat -L policy.dat
tpm2_flushcontext session.dat
Step 2: create an object using that policy
tpm2_create -Q -u key.pub -r key.priv -C primary.ctx -L policy.dat \
-i- <<< "12345678"
tpm2_load -C primary.ctx -u key.pub -r key.priv -n unseal.key.name \
-c unseal.key.ctx
Step 3: Satisfy the policy
tpm2_startauthsession --policy-session -S session.dat
tpm2_policypcr -S session.dat -l "sha1:0,1,2,3" -f pcr.dat -L policy.dat
Step 4: Use the policy
tpm2_unseal -psession:session.dat -c unseal.key.ctx
12345678
tpm2_flushcontext session.dat