Re: [RFC] MemoryProtectionLib for Dynamic Memory Guard Settings

["Taylor Beebe" <t@taylorbeebe.com>]

Of course - here are a couple of rough drafts:

Option 1: https://github.com/TaylorBeebe/edk2/tree/memory_protection_lib_2
Option 2: https://github.com/TaylorBeebe/edk2/tree/memory_protection_lib

On 7/29/2021 6:57 PM, Yao, Jiewen wrote:
> Hi
> Sorry, I am not able to follow the discussion.
> 
> Is there any sample or POC code to show the concept?
> 
>> -----Original Message-----
>> From: Taylor Beebe <t@taylorbeebe.com>
>> Sent: Friday, July 30, 2021 9:55 AM
>> To: Wang, Jian J <jian.j.wang@intel.com>; devel@edk2.groups.io
>> Cc: spbrogan@outlook.com; Dong, Eric <eric.dong@intel.com>; Ni, Ray
>> <ray.ni@intel.com>; Kumar, Rahul1 <rahul1.kumar@intel.com>;
>> mikuback@linux.microsoft.com; Wu, Hao A <hao.a.wu@intel.com>; Bi, Dandan
>> <dandan.bi@intel.com>; gaoliming@byosoft.com.cn; Dong, Guo
>> <guo.dong@intel.com>; Ma, Maurice <maurice.ma@intel.com>; You, Benjamin
>> <benjamin.you@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>
>> Subject: Re: [RFC] MemoryProtectionLib for Dynamic Memory Guard Settings
>>
>> Thanks for your feedback, Jian.
>>
>> In option 2, a most basic implementation would returning the current
>> FixedAtBuild PCDs assuming they are kept. If they aren't, the library
>> implementer could simply hard-code the return value for each memory
>> protection setting.
>>
>> In option 1, the HOB would be published in pre-mem and I'm not an expert
>> on exploiting the pre-mem environment. Jiewen may have more to say on this.
>>
>> -Taylor
>>
>> On 7/28/2021 7:18 PM, Wang, Jian J wrote:
>>> Thanks for the RFC. I'm not object to this idea. The only concern from me
>>> is the potential security holes introduced by the changes. According to your
>>> description, it allows 3rd party software to violate memory protection policy.
>>> I'd like to see more explanations on how to avoid it to be exploited.
>>>
>>> +Jiewen, what's current process to evaluate the security threat?
>>>
>>> Regards,
>>> Jian
>>>
>>>> -----Original Message-----
>>>> From: Taylor Beebe <t@taylorbeebe.com>
>>>> Sent: Friday, July 23, 2021 8:33 AM
>>>> To: devel@edk2.groups.io
>>>> Cc: spbrogan@outlook.com; Dong, Eric <eric.dong@intel.com>; Ni, Ray
>>>> <ray.ni@intel.com>; Kumar, Rahul1 <Rahul1.Kumar@intel.com>;
>>>> mikuback@linux.microsoft.com; Wang, Jian J <jian.j.wang@intel.com>; Wu,
>>>> Hao A <hao.a.wu@intel.com>; Bi, Dandan <dandan.bi@intel.com>;
>>>> gaoliming@byosoft.com.cn; Dong, Guo <guo.dong@intel.com>; Ma,
>> Maurice
>>>> <maurice.ma@intel.com>; You, Benjamin <benjamin.you@intel.com>
>>>> Subject: [RFC] MemoryProtectionLib for Dynamic Memory Guard Settings
>>>>
>>>> Current memory protection settings rely on FixedAtBuild PCD values
>>>> (minus PcdSetNxForStack). Because of this, the memory protection
>>>> configuration interface is fixed in nature. Cases arise in which memory
>>>> protections might need to be adjusted between boots (if platform design
>>>> allows) to avoid disabling a system. For example, platforms might choose
>>>> to allow the user to control their protection policies such as allow
>>>> execution of critical 3rd party software that might violate memory
>>>> protections.
>>>>
>>>> This RFC seeks your feedback regarding introducing an interface that
>>>> allows dynamic configuration of memory protection settings.
>>>>
>>>> I would like to propose two options:
>>>> 1. Describing the memory protection setting configuration in a HOB that
>>>> is produced by the platform.
>>>> 2. Introducing a library class (e.g. MemoryProtectionLib) that allows
>>>> abstraction of the memory protection setting configuration data source.
>>>>
>>>> In addition, I would like to know if the memory protection FixedAtBuild
>>>> PCDs currently in MdeModulePkg can be removed so we can move the
>>>> configuration interface entirely to an option above.
>>>>
>>>> In any case, I would like the settings to be visible to environments
>>>> such as Standalone MM where dynamic PCDs are not accessible.
>>>>
>>>> I am seeking your feedback on this proposal in preparation for sending
>>>> an edk2 patch series.
>>>>
>>>> --
>>>> Taylor Beebe
>>>> Software Engineer @ Microsoft
>>
>> --
>> Taylor Beebe
>> Software Engineer @ Microsoft

-- 
Taylor Beebe
Software Engineer @ Microsoft