linux-kernel - RE: One question about trusted key of keyring in Linux kernel.

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Date:   Wed, 27 Nov 2019 02:46:44 +0000
From:   "Zhao, Shirley" <shirley.zhao@...el.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>
CC:     "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "'Mauro Carvalho Chehab'" <mchehab+samsung@...nel.org>,
        "Zhu, Bing" <bing.zhu@...el.com>,
        "Chen, Luhai" <luhai.chen@...el.com>
Subject: RE: One question about trusted key of keyring in Linux kernel.

Hi, Mimi, 

Answer your two questions:

1. Yes, I have verified trusted key works well without PCR policy protection as below: 
$ keyctl add trusted kmk "new 32 keyhandle=0x81000001" @u
1055240928
$ keyctl list @u
1 keys in keyring:
1055240928: --alswrv     0     0 trusted: kmk
$ keyctl pipe 1055240928 > kmk.blob
$ cat kmk.blob
007f0020ff808bd8b7239194e89aac6a95b4d210114742c20afa33493f002dffd0685d510010c12d7ad51eb83d6d93895de066bf3d39718cc503adb4802cb087b88b2fff4b040fe3a2be6a3f87c6749d087c9fb6e8734cb23f438d64087581a13bc83d5dc3b026e77a894ece6620d0eb85df6449ff3c609fd77d5f0caf79b4535b002e0008000b000000400000001000209a5b00b0d558fcf9e8c029522715e6b5906366eaec5f34367b8ab16c0fb9009a0073000000000020e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b85501000b0022000bdcdb694e102e13a0fba5111081cb6cf616c118d404936cac3e84db24c71e47d50022000b04b5db1aa52635dfb242e76f6bde8e2176ae48fc682946c6c76d96f608079d1f0000002036b6fcca8206c7f722de85821d7ecb4785976fdd642bc7538505a2a818c8a23880214000000100202aedde4508f548d108193ec8fe166a7befde19113fe727ae2b29901bdece96e5
$ keyctl clear @u
$ keyctl list @u
keyring is empty
$ keyctl add trusted kmk "load `cat kmk.blob` keyhandle=0x81000001" @u
1022963731
$ keyctl print 1022963731
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

2. The following kernel file is related with this problem. 
/security/keys/keyctl.c
/security/keys/key.c
/security/keys/trusted-keys/trusted_tpm1.c
/security/keys/trusted-keys/trusted_tpm2.c

To load the PCR policy protection trusted key, the call stack is: 
SYSCALL_DEFINE5(add_key,...) --> key_create_or_update() --> __key_instantiate_and_link() -->  trusted_instantiate() --> tpm2_unseal_trusted() --> tpm2_unseal_cmd(). 

Check dmesg, there will be error: 
[73336.351596] trusted_key: key_unseal failed (-1)

- Shirley 

-----Original Message-----
From: Mimi Zohar <zohar@...ux.ibm.com> 
Sent: Wednesday, November 27, 2019 3:28 AM
To: Zhao, Shirley <shirley.zhao@...el.com>; James Bottomley <jejb@...ux.ibm.com>; Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>; Jonathan Corbet <corbet@....net>
Cc: linux-integrity@...r.kernel.org; keyrings@...r.kernel.org; linux-doc@...r.kernel.org; linux-kernel@...r.kernel.org; 'Mauro Carvalho Chehab' <mchehab+samsung@...nel.org>; Zhu, Bing <bing.zhu@...el.com>; Chen, Luhai <luhai.chen@...el.com>
Subject: Re: One question about trusted key of keyring in Linux kernel.

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.

Mimi