linux-kernel - Re: [PATCH v9 6/6] IMA: Read keyrings= option from the IMA policy

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Message-ID: <3fb64c8a-59d3-3390-07c6-283099f55f86@linux.microsoft.com>
Date:   Wed, 27 Nov 2019 14:05:56 -0800
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, linux-integrity@...r.kernel.org
Cc:     eric.snowberg@...cle.com, dhowells@...hat.com,
        matthewgarrett@...gle.com, sashal@...nel.org,
        jamorris@...ux.microsoft.com, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org
Subject: Re: [PATCH v9 6/6] IMA: Read keyrings= option from the IMA policy

On 11/27/19 11:32 AM, Mimi Zohar wrote:

> 
> The example is really too colloquial/verbose.  Please truncate it,
> leaving just a sample "key" policy rule, with directions for verifying
> the template data against the digest included in the measurement list.

I'll truncate the example and keep it to the point.

>> The following command verifies if the SHA256 hash generated from
>> the payload in the IMA log entry (listed above) for the .ima key
>> matches the SHA256 hash in the IMA log entry. The output of this
>> command should match the SHA256 hash given in the IMA log entry
>> (In this case, it should be
>> 27c915b8ddb9fae7214cf0a8a7043cc3eeeaa7539bcb136f8427067b5f6c3b7b)
> 
> Previously you didn't use the hash value, but ".ima" to locate the
> "key" measurement in the measurement list.  In each of the commands
> above, it might be clearer.

If the IMA measurement list has only one IMA key then locating it with 
".ima" would work - hash won't be needed for locating the entry.

But for describing key verification we can have just one IMA key. I'll 
change the description to locate the entry using ".ima".

>> # cat /sys/kernel/security/integrity/ima/ascii_runtime_measurements
>> | grep
>> 27c915b8ddb9fae7214cf0a8a7043cc3eeeaa7539bcb136f8427067b5f6c3b7b |
> 
>> cut -d' ' -f 6 | xxd -r -p |tee ima-cert.der | sha256sum | cut -d' '
>> -f 1
>>
>> The above command also creates a binary file namely ima-cert.der
>> using the payload in the IMA log entry. This file should be a valid
>> x509 certificate which can be verified using openssl as given below:
>>
>> root@...mas:/home/nramas
> 
> ditto
> 
> 
>> # openssl x509 -in ima-cert.der -inform DER -text
>>
>> The above command should display the contents of the file ima-cert.der
>> as an x509 certificate.
> 
> Either the comments should be above or below the commands, not both.

I'll update the comment.

> 
>>
>> The IMA policy used here allows measurement of keys added to
>> ".ima" and ".evm" keyrings only. Add a key to any other keyring and
>> verify that the key is not measured.
> 
> This comment would be included, if desired, when defining the policy
> rule, not here.

Will remove the above from this patch description.

thanks,
  -lakshmi