Re: [PATCH 1/1] SecurityPkg/AuthVariableLib: Check SHA-256 OID with ContentInfo present

["Jan Bobek" <jbobek@nvidia.com>]

Anothing ping. Comments/reviews/merge highly appreciated.

Thank you,
-Jan

Jan Bobek writes:

> Ping. Can I get a review and/or some comments on this patch, please?
>
> Thanks,
> -Jan
>
> Jan Bobek writes:
>
>> Based on whether the DER-encoded ContentInfo structure is present in
>> authenticated SetVariable payload or not, the SHA-256 OID can be
>> located at different places.
>>
>> UEFI specification explicitly states the driver shall support both
>> cases, but the old code assumed ContentInfo was not present and
>> incorrectly rejected authenticated variable updates when it were
>> present.
>>
>> Cc: Jiewen Yao <jiewen.yao@intel.com>
>> Cc: Jian J Wang <jian.j.wang@intel.com>
>> Cc: Min Xu <min.m.xu@intel.com>
>> Signed-off-by: Jan Bobek <jbobek@nvidia.com>
>> ---
>>  .../Library/AuthVariableLib/AuthService.c      | 18 +++++++++++-------
>>  1 file changed, 11 insertions(+), 7 deletions(-)
>>
>> diff --git a/SecurityPkg/Library/AuthVariableLib/AuthService.c b/SecurityPkg/Library/AuthVariableLib/AuthService.c
>> index 054ee4d1d988..de8baccab410 100644
>> --- a/SecurityPkg/Library/AuthVariableLib/AuthService.c
>> +++ b/SecurityPkg/Library/AuthVariableLib/AuthService.c
>> @@ -1933,15 +1933,19 @@ VerifyTimeBasedPayload (
>>    //            .... }
>>    //    The DigestAlgorithmIdentifiers can be used to determine the hash algorithm
>>    //    in VARIABLE_AUTHENTICATION_2 descriptor.
>> -  //    This field has the fixed offset (+13) and be calculated based on two bytes of length encoding.
>> +  //    This field has the fixed offset (+13) or (+32) based on whether the DER-encoded
>> +  //    ContentInfo structure is present or not, and can be calculated based on two
>> +  //    bytes of length encoding.
>>    //
>>    if ((Attributes & EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) != 0) {
>> -    if (SigDataSize >= (13 + sizeof (mSha256OidValue))) {
>> -      if (((*(SigData + 1) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE) ||
>> -          (CompareMem (SigData + 13, &mSha256OidValue, sizeof (mSha256OidValue)) != 0))
>> -      {
>> -        return EFI_SECURITY_VIOLATION;
>> -      }
>> +    if (  (  (SigDataSize >= (13 + sizeof (mSha256OidValue)))
>> +          && (  ((*(SigData + 1) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE)
>> +             || (CompareMem (SigData + 13, &mSha256OidValue, sizeof (mSha256OidValue)) != 0)))
>> +       && (  (SigDataSize >= (32 + sizeof (mSha256OidValue)))
>> +          && (  ((*(SigData + 20) & TWO_BYTE_ENCODE) != TWO_BYTE_ENCODE)
>> +             || (CompareMem (SigData + 32, &mSha256OidValue, sizeof (mSha256OidValue)) != 0))))
>> +    {
>> +      return EFI_SECURITY_VIOLATION;
>>      }
>>    }