Re: One question about trusted key of keyring in Linux kernel.

[Jarkko Sakkinen]

On Tue, Nov 26, 2019 at 02:27:36PM -0500, Mimi Zohar wrote:
> On Tue, 2019-11-26 at 07:32 +0000, Zhao, Shirley wrote:
> > Thanks for your feedback, Mimi. 
> > But the document of dracut can't solve my problem. 
> > 
> > I did more test these days and try to descript my question in more detail. 
> > 
> > In my scenario, the trusted key will be sealed into TPM with PCR policy. 
> > And there are some related options in manual like 
> >        hash=         hash algorithm name as a string. For TPM 1.x the only
> >                      allowed value is sha1. For TPM 2.x the allowed values
> >                      are sha1, sha256, sha384, sha512 and sm3-256.
> >        policydigest= digest for the authorization policy. must be calculated
> >                      with the same hash algorithm as specified by the 'hash='
> >                      option.
> >        policyhandle= handle to an authorization policy session that defines the
> >                      same policy and with the same hash algorithm as was used to
> >                      seal the key. 
> > 
> > Here is my test step. 
> > Firstly, the pcr policy is generated as below: 
> > $ tpm2_createpolicy --policy-pcr --pcr-list sha256:7 --policy pcr7_bin.policy > pcr7.policy
> > 
> > Pcr7.policy is the ascii hex of policy:
> > $ cat pcr7.policy
> > 321fbd28b60fcc23017d501b133bd5dbf2889814588e8a23510fe10105cb2cc9
> > 
> > Then generate the trusted key and configure policydigest and get the key ID: 
> > $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha256 policydigest=`cat pcr7.policy`" @u
> > 874117045
> > 
> > Save the trusted key. 
> > $ keyctl pipe 874117045 > kmk.blob
> > 
> > Reboot and load the key. 
> > Start a auth session to generate the policy:
> > $ tpm2_startauthsession -S session.ctx
> > session-handle: 0x3000000
> > $ tpm2_pcrlist -L sha256:7 -o pcr7.sha256
> > $ tpm2_policypcr -S session.ctx -L sha256:7 -F pcr7.sha256 -f pcr7.policy
> > policy-digest: 0x321FBD28B60FCC23017D501B133BD5DBF2889814588E8A23510FE10105CB2CC9
> > 
> > Input the policy handle to load trusted key:
> > $ keyctl add trusted kmk "load `cat kmk.blob` keyhandle=0x81000001 policyhandle=0x3000000" @u
> > add_key: Operation not permitted
> > 
> > The error should be policy check failed, because I use TPM command to unseal directly with error of policy check failed. 
> > $ tpm2_unseal -c 0x81000001 -L sha256:7
> > ERROR on line: "81" in file: "./lib/log.h": Tss2_Sys_Unseal(0x99D) - tpm:session(1):a policy check failed
> > ERROR on line: "213" in file: "tools/tpm2_unseal.c": Unseal failed!
> > ERROR on line: "166" in file: "tools/tpm2_tool.c": Unable to run tpm2_unseal
> > 
> > So my question is:
> > 1. How to use the option, policydigest, policyhandle?? Is there any example? 
> > 2. What's wrong with my test step? 
> 
> When reporting a problem please state which kernel is experiencing
> this problem.  Recently there was a trusted key regression.  Refer to
> commit e13cd21ffd50 "tpm: Wrap the buffer from the caller to tpm_buf
> in tpm_send()" for the details.
> 
> Before delving into this particular problem, first please make sure
> you are able to create, save, remove, and then reload a trusted key
> not sealed to a PCR.

Please re-test with rc1 when available.

/Jarkko