linux-kernel - Re: [PATCH v10 6/6] IMA: Read keyrings= option from the IMA policy

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Date:   Tue, 10 Dec 2019 17:43:53 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        linux-integrity@...r.kernel.org
Cc:     eric.snowberg@...cle.com, dhowells@...hat.com,
        mathew.j.martineau@...ux.intel.com, matthewgarrett@...gle.com,
        sashal@...nel.org, jamorris@...ux.microsoft.com,
        linux-kernel@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH v10 6/6] IMA: Read keyrings= option from the IMA policy

On Wed, 2019-12-04 at 14:41 -0800, Lakshmi Ramasubramanian wrote:
> Read "keyrings=" option, if specified in the IMA policy, and store in
> the list of IMA rules when the configured IMA policy is read.
> 
> This patch defines a new policy token enum namely Opt_keyrings
> and an option flag IMA_KEYRINGS for reading "keyrings=" option
> from the IMA policy.
> 
> Updated ima_parse_rule() to parse "keyrings=" option in the policy.
> Updated ima_policy_show() to display "keyrings=" option.
> 
> The following example illustrates how key measurement can be verified.
> 
> Sample "key" measurement rule in the IMA policy:
> 
> measure func=KEY_CHECK uid=0 keyrings=.ima|.evm template=ima-buf
> 
> Display "key" measurement in the IMA measurement list:
> 
> cat /sys/kernel/security/ima/ascii_runtime_measurements
> 
> 10 faf3...e702 ima-buf
> sha256:27c915b8ddb9fae7214cf0a8a7043cc3eeeaa7539bcb136f8427067b5f6c3
> b7b .ima 308202863082...4aee
> 
> Verify "key" measurement data for a key added to ".ima" keyring:
> 
> cat /sys/kernel/security/integrity/ima/ascii_runtime_measurements |
> grep ".ima" | cut -d' ' -f 6 | xxd -r -p |tee ima-cert.der |
> sha256sum | cut -d' ' -f 1
> 

The dot needs to be quoted, otherwise it matches any character.  I
would also limit the above command to the first instance (eg. grep -m
1 "\.ima).

> The output of the above command should match the sha256 hash
> in the "key" measurement entry in the IMA measurement list.

There are multiple hashes in a measurement list record.  Perhaps refer
to the 2nd hash as the "template hash".

Mimi

> 
> The file namely "ima-cert.der" generated by the above command
> should be a valid x509 certificate (in DER format) and should match
> the one that was used to import the key to the .ima keyring.
> The certificate file can be verified using openssl tool.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>