linux-kernel - Re: [PATCH] IMA: Handle early boot data measurement

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Message-ID: <958853ec-5354-fbcb-3fa0-2002954c3e40@linux.microsoft.com>
Date:   Tue, 25 Aug 2020 12:35:19 -0700
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, stephen.smalley.work@...il.com,
        casey@...aufler-ca.com
Cc:     tyhicks@...ux.microsoft.com, tusharsu@...ux.microsoft.com,
        sashal@...nel.org, jmorris@...ei.org,
        linux-integrity@...r.kernel.org, selinux@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] IMA: Handle early boot data measurement

On 8/25/20 11:03 AM, Mimi Zohar wrote:
> On Tue, 2020-08-25 at 10:55 -0700, Lakshmi Ramasubramanian wrote:
>> On 8/25/20 10:42 AM, Mimi Zohar wrote:
>>
>>>>> Please limit the changes in this patch to renaming the functions and/or
>>>>> files.  For example, adding "measure_payload_hash" should be a separate
>>>>> patch, not hidden here.
>>>>>
>>>>
>>>> Thanks for the feedback Mimi.
>>>>
>>>> I'll split this into 2 patches:
>>>>
>>>> PATCH 1: Rename files + rename CONFIG
>>>> PATCH 2: Update IMA hook to utilize early boot data measurement.
>>>
>>> I'm referring to introducing the "measure_payload_hash" flag.  I assume
>>> this is to indicate whether the buffer should be hashed or not.
>>>
>>> Example 1: ima_alloc_key_entry() and ima_alloc_data_entry(0 comparison
>>>> -static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
>>>> -                                                const void *payload,
>>>> -                                                size_t payload_len)
>>>> -{
>>>> +static struct ima_data_entry *ima_alloc_data_entry(const char *event_name,
>>>> +                                                  const void *payload,
>>>> +                                                  size_t payload_len,
>>>> +                                                  const char *event_data,
>>>> +                                                  enum ima_hooks func,
>>>> +                                                  bool measure_payload_hash)  <====
>>>> +{
>>>
>>> Example 2:
>>> diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
>>> index a74095793936..65423754765f 100644
>>> --- a/security/integrity/ima/ima_asymmetric_keys.c
>>> +++ b/security/integrity/ima/ima_asymmetric_keys.c
>>> @@ -37,9 +37,10 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
>>>           if (!payload || (payload_len == 0))
>>>                   return;
>>>    
>>> -       if (ima_should_queue_key())
>>> -               queued = ima_queue_key(keyring, payload, payload_len);
>>> -
>>> +       if (ima_should_queue_data())
>>> +               queued = ima_queue_data(keyring->description, payload,
>>> +                                       payload_len, keyring->description,
>>> +                                       KEY_CHECK, false);   <===
>>>           if (queued)
>>>                   return;
>>>
>>> But in general, as much as possible function and file name changes
>>> should be done independently of other changes.
>>>
>>> thanks,
>>
>> I agree - but in this case, Tushar's patch series on adding support for
>> "Critical Data" measurement has already introduced
>> "measure_payload_hash" flag. His patch updates
>> "process_buffer_measurement()" to take this new flag and measure hash of
>> the given data.
>>
>> My patches extend that to queuing the early boot requests and processing
>> them after a custom IMA policy is loaded.
>>
>> If you still think "measure_payload_hash" flag should be introduced in
>> the queuing change as a separate patch I'll split the patches further.
>> Please let me know.
> 
> There's a major problem if his changes add new function arguments
> without modifying all the callers of the function.  I assume the kernel
> would fail to compile properly.

Tushar's patch series does update all the existing callers of 
process_buffer_measurement() to handle the new arguments. His patch 
series is self contained, and builds and works fine.

> 
> Changing the function parameters to include "measure_payload_hash"
> needs to be a separate patch, whether it is part of his patch set or
> yours.
> 

ok - I'll split the queuing patch to include "measure_payload_hash" in a 
separate patch.

thanks,
  -lakshmi