Re: [edk2-devel] [PATCH RESEND v1 5/7] MdePkg/AesLib: Definition for AES library class interface

["PierreGondois" <pierre.gondois@arm.com>]

Hello Jiewen,

On 7/1/22 13:55, Yao, Jiewen wrote:
> I have two concern:
> 
> 1) I am worried that this API might be misused. Usually, a crypto API should be secure enough to avoid misuse. For example, if a program wants to use AES encryption, it must NOT use this AES API. Instead it must use AES_CCB + MAC or AES_GCM. (or equivalent)
> I doubt if this is right direction to expose this publicly in MdePkg.
> 
> 2) I am not sure how this API will be used in CryptoLib.
> Ideally, an EDKII program should use crypto lib API for any crypto function.
> However, I do not understand how that is done.
> 

The reason the AesLib was put in MdePkg:
- The DrbgLib was thought to be generic enough to be in MdePkg
   (this is arguable).
- The MdePkg must be self-contained (i.e. not use libraries/modules
   defined in other packages). Thus if an AesLib is created, it must be
   in the MdePkg.
I don't mind moving the DrbgLib (and the AesLib) to another package if
this is the common agreement.

Why a single block AesLib should be created:
- The DrbgLib requires to have Aes single block encryption. A software
   implementation of Aes is also available (and used) at [2] in the
   SecurityPkg. This implementation is limited to a module scope.
   Thus, there is a need create a common library for this.
- I agree that this AesLib should not be mistaken with something else
   (cf your comment about AES_CCB + MAC or AES_GCM). However, the new
   interface needed is for a single block encryption. So adding these
   new functions to:
   CryptoPkg/Include/Library/BaseCryptLib.h
   won't make it safer.

Please let me know if there are still concerns,
Regards,
Pierre

Note:
The functions in AesLib are equivalent to the ones in [4].

[1] https://edk2.groups.io/g/devel/files/Designs/2021/0116/EDKII%20-%20Proposed%20update%20to%20RNG%20implementation.pdf
[2] https://github.com/tianocore/edk2/blob/f966093f5bb88e6fccac8e0b9eeca6c73aef0c35/SecurityPkg/RandomNumberGenerator/RngDxe/Rand/AesCore.c#L215
[3] https://github.com/tianocore/edk2/blob/f966093f5bb88e6fccac8e0b9eeca6c73aef0c35/CryptoPkg/Include/Library/BaseCryptLib.h#L1128
[4] https://github.com/openssl/openssl/blob/master/crypto/aes/aes_core.c


> 
> I think it is good idea to enable ARM AES hardware accelerator.
> And I would like to see a total solution.
> 
> It will be great, if you also submit the cryptopkg patch to help me understand how to achieve that.
> 
> Thank you
> Yao Jiewen
> 
> 
>> -----Original Message-----
>> From: Pierre Gondois <pierre.gondois@arm.com>
>> Sent: Friday, July 1, 2022 5:49 PM
>> To: Yao, Jiewen <jiewen.yao@intel.com>; devel@edk2.groups.io
>> Cc: Sami Mujawar <sami.mujawar@arm.com>; Leif Lindholm
>> <quic_llindhol@quicinc.com>; Ard Biesheuvel <ardb+tianocore@kernel.org>;
>> Rebecca Cran <rebecca@bsdio.com>; Kinney, Michael D
>> <michael.d.kinney@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>;
>> Edward Pickup <Edward.Pickup@arm.com>
>> Subject: Re: [edk2-devel] [PATCH RESEND v1 5/7] MdePkg/AesLib: Definition for
>> AES library class interface
>>
>> Hello Yao,
>>
>> On 6/30/22 02:29, Yao, Jiewen wrote:
>>> Hi
>>> 1) Would you please educate me, how this library be used in cryptolib? -
>> https://github.com/tianocore/edk2/blob/master/CryptoPkg/Include/Library/Bas
>> eCryptLib.h#L1091
>>>
>>> Currently, we have AES_CBC. We are going to add AES_GCM in near future.
>>>
>>
>> We are currently looking forward to do that. Just to be sure, the
>> AesInit() function pointed above is for AesCbcEncrypt(), which can
>> encrypt a buffer.
>> The AesInitCtx() in this file is for a single block encryption. So
>> there should be nothing preventing from implementing CBC (or other)
>> encryption based on the Aes block encryption added by this patch-set.
>>
>>> 2) For Intel AES_NI, we added support in OpensslLib directly -
>> https://github.com/tianocore/edk2/tree/master/CryptoPkg/Library/OpensslLib/
>> X64, can ARM use the similar model?
>>>
>>
>> We also need to have a look at this. However this might be a bit more
>> difficult if we want to avoid Openssl license.
>>
>>> 3) Do you have chance to take a look if this interface is good enough to
>> implement Intel AES_NI instruction?
>>>
>>
>> We have not looked at the AES_NI instruction, but the interface
>> definition should be generic enough to accept any implementation.
>> Please tell us if you think this requires modification.
>>
>> Regards,
>> Pierre
>>
>>> Thank you
>>> Yao Jiewen
>>>
>>>> -----Original Message-----
>>>> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of
>>>> PierreGondois
>>>> Sent: Thursday, June 30, 2022 3:14 AM
>>>> To: devel@edk2.groups.io
>>>> Cc: Sami Mujawar <sami.mujawar@arm.com>; Leif Lindholm
>>>> <quic_llindhol@quicinc.com>; Ard Biesheuvel <ardb+tianocore@kernel.org>;
>>>> Rebecca Cran <rebecca@bsdio.com>; Kinney, Michael D
>>>> <michael.d.kinney@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>;
>>>> Edward Pickup <Edward.Pickup@arm.com>
>>>> Subject: [edk2-devel] [PATCH RESEND v1 5/7] MdePkg/AesLib: Definition for
>> AES
>>>> library class interface
>>>>
>>>> From: Pierre Gondois <Pierre.Gondois@arm.com>
>>>>
>>>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3970
>>>>
>>>> The FIPS PUB 197: "Advanced Encryption Standard (AES)"
>>>> details the AES algorithm. Add a library to allow
>>>> different architecture specific implementations.
>>>>
>>>> Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
>>>> ---
>>>>    MdePkg/Include/Library/AesLib.h | 104
>> ++++++++++++++++++++++++++++++++
>>>>    MdePkg/MdePkg.dec               |   4 ++
>>>>    2 files changed, 108 insertions(+)
>>>>    create mode 100644 MdePkg/Include/Library/AesLib.h
>>>>
>>>> diff --git a/MdePkg/Include/Library/AesLib.h
>> b/MdePkg/Include/Library/AesLib.h
>>>> new file mode 100644
>>>> index 000000000000..bc3408bb249b
>>>> --- /dev/null
>>>> +++ b/MdePkg/Include/Library/AesLib.h
>>>> @@ -0,0 +1,104 @@
>>>> +/** @file
>>>> +  AES library.
>>>> +
>>>> +  Copyright (c) 2022, Arm Limited. All rights reserved.<BR>
>>>> +
>>>> +  SPDX-License-Identifier: BSD-2-Clause-Patent
>>>> +
>>>> +  @par Reference(s):
>>>> +   - FIPS 197 November 26, 2001:
>>>> +     Specification for the ADVANCED ENCRYPTION STANDARD (AES)
>>>> +**/
>>>> +
>>>> +#ifndef AES_LIB_H_
>>>> +#define AES_LIB_H_
>>>> +
>>>> +/// Key size in bytes.
>>>> +#define AES_KEY_SIZE_128  16
>>>> +#define AES_KEY_SIZE_192  24
>>>> +#define AES_KEY_SIZE_256  32
>>>> +#define AES_BLOCK_SIZE    16
>>>> +
>>>> +/*
>>>> +   The Key Expansion generates a total of Nb (Nr + 1) words with:
>>>> +    - Nb = 4:
>>>> +      Number of columns (32-bit words) comprising the State
>>>> +    - Nr = 10, 12, or 14:
>>>> +      Number of rounds.
>>>> + */
>>>> +#define AES_MAX_KEYLENGTH_U32  (4 * (14 + 1))
>>>> +
>>>> +/** A context holding information to for AES encryption/decryption.
>>>> + */
>>>> +typedef struct {
>>>> +  /// Expanded encryption key.
>>>> +  UINT32    ExpEncKey[AES_MAX_KEYLENGTH_U32];
>>>> +  /// Expanded decryption key.
>>>> +  UINT32    ExpDecKey[AES_MAX_KEYLENGTH_U32];
>>>> +  /// Key size, in bytes.
>>>> +  /// Must be one of 16|24|32.
>>>> +  UINT32    KeySize;
>>>> +} AES_CTX;
>>>> +
>>>> +/** Encrypt an AES block.
>>>> +
>>>> +  Buffers are little-endian. Overlapping is not checked.
>>>> +
>>>> +  @param [in]  AesCtx    AES context.
>>>> +                         AesCtx is initialized with AesInitCtx ().
>>>> +  @param [in]  InBlock   Input Block. The block to cipher.
>>>> +  @param [out] OutBlock  Output Block. The ciphered block.
>>>> +
>>>> +  @retval RETURN_SUCCESS            Success.
>>>> +  @retval RETURN_INVALID_PARAMETER  Invalid parameter.
>>>> +  @retval RETURN_UNSUPPORTED        Unsupported.
>>>> +**/
>>>> +RETURN_STATUS
>>>> +EFIAPI
>>>> +AesEncrypt (
>>>> +  IN  AES_CTX      *AesCtx,
>>>> +  IN  UINT8 CONST  *InBlock,
>>>> +  OUT UINT8        *OutBlock
>>>> +  );
>>>> +
>>>> +/** Decrypt an AES block.
>>>> +
>>>> +  Buffers are little-endian. Overlapping is not checked.
>>>> +
>>>> +  @param [in]  AesCtx    AES context.
>>>> +                         AesCtx is initialized with AesInitCtx ().
>>>> +  @param [in]  InBlock   Input Block. The block to de-cipher.
>>>> +  @param [out] OutBlock  Output Block. The de-ciphered block.
>>>> +
>>>> +  @retval RETURN_SUCCESS            Success.
>>>> +  @retval RETURN_INVALID_PARAMETER  Invalid parameter.
>>>> +  @retval RETURN_UNSUPPORTED        Unsupported.
>>>> +**/
>>>> +RETURN_STATUS
>>>> +EFIAPI
>>>> +AesDecrypt (
>>>> +  IN  AES_CTX      *AesCtx,
>>>> +  IN  UINT8 CONST  *InBlock,
>>>> +  OUT UINT8        *OutBlock
>>>> +  );
>>>> +
>>>> +/** Initialize an AES_CTX structure.
>>>> +
>>>> +  @param [in]       Key       AES key. Buffer of KeySize bytes.
>>>> +                              The buffer is little endian.
>>>> +  @param [in]       KeySize   Size of the key. Must be one of 128|192|256.
>>>> +  @param [in, out]  AesCtx    AES context to initialize.
>>>> +
>>>> +  @retval RETURN_SUCCESS            Success.
>>>> +  @retval RETURN_INVALID_PARAMETER  Invalid parameter.
>>>> +  @retval RETURN_UNSUPPORTED        Unsupported.
>>>> +**/
>>>> +RETURN_STATUS
>>>> +EFIAPI
>>>> +AesInitCtx (
>>>> +  IN      UINT8    *Key,
>>>> +  IN      UINT32   KeySize,
>>>> +  IN OUT  AES_CTX  *AesCtx
>>>> +  );
>>>> +
>>>> +#endif // AES_LIB_H_
>>>> diff --git a/MdePkg/MdePkg.dec b/MdePkg/MdePkg.dec
>>>> index 7ff26e22f915..078ae9323ba6 100644
>>>> --- a/MdePkg/MdePkg.dec
>>>> +++ b/MdePkg/MdePkg.dec
>>>> @@ -280,6 +280,10 @@ [LibraryClasses]
>>>>      #
>>>>      TrngLib|Include/Library/TrngLib.h
>>>>
>>>> +  ##  @libraryclass  Provides AES encryption/decryption services.
>>>> +  #
>>>> +  AesLib|Include/Library/AesLib.h
>>>> +
>>>>    [LibraryClasses.IA32, LibraryClasses.X64, LibraryClasses.AARCH64]
>>>>      ##  @libraryclass  Provides services to generate random number.
>>>>      #
>>>> --
>>>> 2.25.1
>>>>
>>>>
>>>>
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