linux-kernel - Re: [PATCH v9 5/8] ima: make process_buffer

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Message-ID: <8a97301a-0e25-2718-bd81-d778cb58e1d3@linux.microsoft.com>
Date:   Fri, 25 Oct 2019 10:32:53 -0700
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Nayna Jain <nayna@...ux.vnet.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>, linuxppc-dev@...abs.org,
        linux-efi@...r.kernel.org, linux-integrity@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Jeremy Kerr <jk@...abs.org>,
        Matthew Garret <matthew.garret@...ula.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Claudio Carvalho <cclaudio@...ux.ibm.com>,
        George Wilson <gcwilson@...ux.ibm.com>,
        Elaine Palmer <erpalmer@...ibm.com>,
        Eric Ricther <erichte@...ux.ibm.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Prakhar Srivastava <prsriva02@...il.com>
Subject: Re: [PATCH v9 5/8] ima: make process_buffer_measurement() generic



On 10/25/2019 10:24 AM, Nayna Jain wrote:
> 
> On 10/24/19 10:20 AM, Lakshmi Ramasubramanian wrote:
>> On 10/23/19 8:47 PM, Nayna Jain wrote:
>>
>> Hi Nayna,
>>
>>> +void process_buffer_measurement(const void *buf, int size,
>>> +                const char *eventname, enum ima_hooks func,
>>> +                int pcr)
>>>   {
>>>       int ret = 0;
>>>       struct ima_template_entry *entry = NULL;
>>
>>> +    if (func) {
>>> +        security_task_getsecid(current, &secid);
>>> +        action = ima_get_action(NULL, current_cred(), secid, 0, func,
>>> +                    &pcr, &template);
>>> +        if (!(action & IMA_MEASURE))
>>> +            return;
>>> +    }
>>
>> In your change set process_buffer_measurement is called with NONE for 
>> the parameter func. So ima_get_action (the above if block) will not be 
>> executed.
>>
>> Wouldn't it better to update ima_get_action (and related functions) to 
>> handle the ima policy (func param)?
> 
> 
> The idea is to use ima-buf template for the auxiliary measurement 
> record. The auxiliary measurement record is an additional record to the 
> one already created based on the existing policy. When func is passed as 
> NONE, it represents it is an additional record. I am not sure what you 
> mean by updating ima_get_action, it is already handling the ima policy.
>

I was referring to using "func" in process_buffer_measurement to 
determine ima action. In my opinion, process_buffer_measurement should 
be generic.

ima_get_action() should instead determine the required ima action, 
template, pcr, etc. based on "func" passed to it.

thanks,
  -lakshmi