Re: [tpm2] Issues experimenting with tpm2-tools and keyctl trusted keys

[Javier Martinez Canillas <javierm at redhat.com>]

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Hello Thibaut,

On 1/21/19 9:16 AM, Thibaut Sautereau wrote:
> Hello folks,
> 
> I'm experimenting with TPM 2.0 (using swtpm 0.1.0), tpm2-tools 3.1.3,
> tpm2-tss 2.1.0 and the Linux 4.19.16 kernel's trusted keys. I found this
> thread [1] about the "policydigest" and "policyhandle" options added to
> keyctl but I cannot reproduce the given example [2] using tpm2-tools
> instead of the author's Python testing scripts [3]. I wonder if I do
> something wrong by executing the following commands:
>

Did it work for you when using Jarkko's test scripts?
 
> export TPM2TOOLS_TCTI="device:/dev/tpmrm0"
> tpm2_takeownership --clear
> # I tried fiddling with the object attributes in the following command
> # but AIUI the default ones should be OK
> tpm2_createprimary --hierarchy=o --halg=sha256 --kalg=rsa \
> 	--context=/tmp/primary.context 
> tpm2_evictcontrol --auth=o --context=/tmp/primary.context \
> 	--handle=0x80ffffff --persistent=0x81010001
> tpm2_createpolicy --policy-file=/tmp/policy.digest --policy-pcr \
> 	--set-list=sha256:0 --policy-digest-alg=sha256
> policydigest=$(xxd -p /tmp/policy.digest | tr -d '\n')
> keyid=$(keyctl add trusted test \
> 	"new 32 keyhandle=0x81010001 hash=sha256 policydigest=$policydigest" @u)
> keyctl link @us @s
> keyctl pipe $keyid > /tmp/blob.hex
> 
> Until here, everything works fine.
> 
> Now for testing I want to reimport the key from the blob file, but I
> need a handle to a TPM_SE_POLICY and thus need to directly use the TPM
> device, as the in-kernel resource manager I was using so far would
> prevent me from keeping a policy session "opened". So I re-export
> TPM2TOOLS_TCTI just as Javier Martinez Canillas showed on GitHub [4]:
> 
> export TPM2TOOLS_TCTI="device:/dev/tpm0"
> # --auth-policy-session implies --extend-policy-session
> tpm2_createpolicy --policy-pcr --set-list=sha256:0 \
> 	--policy-digest-alg=sha256 --auth-policy-session
> keyctl add trusted test2 \
> 	"load $(cat /tmp/blob.hex) keyhandle=0x81010001 policyhandle=0x03000000" @u
> 

You have the policy handle hardcoded to 0x03000000 here, I guess that's correct
and is the value printed by tpm2_createpolicy in EXTENDED_POLICY_SESSION_HANDLE?

Sorry for saying the obvious, but just in case since I don't see anything wrong
with your commands.

> This last command causes: "add_key: Operation not permitted".
> In kernel logs, I have:
> 	[ 1350.287556] tpm tpm0: A TPM error (2466) occurred unsealing
> 	[ 1350.289856] trusted_key: key_unseal failed (-1)
> 
> The TPM error is 0x9a2, i.e. TPM2_RC_BAD_AUTH. I cannot see what I'm
> doing wrong. Do you see something obvious?
> 
> [1] https://lkml.org/lkml/2015/11/17/520
> [2] https://lkml.org/lkml/2015/11/21/125
> [3] https://github.com/jsakkine-intel/tpm2-scripts
> [4] https://github.com/tpm2-software/tpm2-tools/issues/510#issuecomment-331385565
> 
> Thanks a lot for your time and your work!
> 

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat