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

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Message-ID: <52d2204b-5b6e-e13f-d0dd-192a776812bc@linux.microsoft.com>
Date:   Tue, 25 Aug 2020 10:55:46 -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 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.

thanks,
  -lakshmi