Re: [PATCH ] ima: fix buffer overrun in ima_eventdigest_init_common

[samasth.norway.ananda@oracle.com]

On 6/21/24 3:44 PM, Mimi Zohar wrote:
> Hi Samasth,
> 
> On Thu, 2024-06-20 at 12:46 -0700, Samasth Norway Ananda wrote:
>> Function ima_eventdigest_init() can call ima_eventdigest_init_common()
>> with HASH_ALGO__LAST which is then used to access the array
>> hash_digest_size[] leading to buffer overrun. Have a conditional
>> statement to handle this.
> 
> The original 'ima' template ("d|n") digest is not prefixed with the digest
> algorithm, since it is hard coded to sha1.  ima_eventdigest_init() intentionally
> calls ima_eventdigest_init_common() with HASH_ALGO__LAST.  To avoid ...
> 
>>
>> Fixes: 9fab303a2cb3 ("ima: fix violation measurement list record")
>> Signed-off-by: Samasth Norway Ananda <samasth.norway.ananda@oracle.com>
>> ---
>>   security/integrity/ima/ima_template_lib.c | 8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
>> index 4183956c53af..14c000fe8312 100644
>> --- a/security/integrity/ima/ima_template_lib.c
>> +++ b/security/integrity/ima/ima_template_lib.c
>> @@ -320,13 +320,17 @@ static int ima_eventdigest_init_common(const u8 *digest, u32 digestsize,
>>   
>>   	if (digest)
> 
> Please add a brace after "digest" and before "else".
> 
> Refer to the section titled "3) Placing Braces and Spaces" in "
> https://www.kernel.org/doc/html/v4.10/process/coding-style.html.
> 
> 
>>   		memcpy(buffer + offset, digest, digestsize);
>> -	else
>> +	else {
>>   		/*
>>   		 * If digest is NULL, the event being recorded is a violation.
>>   		 * Make room for the digest by increasing the offset by the
>>   		 * hash algorithm digest size.
>>   		 */
> 
> Please update the comment to reflect the case when the hash algorithm isn't
> specified.
> 
>> -		offset += hash_digest_size[hash_algo];
>> +		if (hash_algo < HASH_ALGO__LAST)
>> +                        offset += hash_digest_size[hash_algo];
>> +               else
>> +                        offset += IMA_DIGEST_SIZE;
>> +	}
>>   
>>   	return ima_write_template_field_data(buffer, offset + digestsize,
>>   					     fmt, field_data);
> 
> Please fix the other scripts/checkpatch.pl complaints.

Thanks for correcting me Mimi. I should have checked that before 
sending. I will make the changes and send a v2 of the patch.

> 
> thanks,
> 
> Mimi
>