[dm-devel] [PATCH v3 0/6] crypto: switch to crypto API for ESSIV generation

[Milan Broz]

On 20/06/2019 15:52, Ard Biesheuvel wrote:
>>>> Does this include configurations that combine authenc with essiv?
>>>
>>> Hm, seems that we are missing these in luks2-integrity-test. I'll add them there.
>>>
>>> I also used this older test
>>> https://gitlab.com/omos/dm-crypt-test-scripts/blob/master/root/test_dmintegrity.sh
>>>
>>> (just aes-gcm-random need to be commented out, we never supported this format, it was
>>> written for some devel version)
>>>
>>> But seems ESSIV is there tested only without AEAD composition...
>>>
>>> So yes, this AEAD part need more testing.
>>
>> And unfortunately it does not work - it returns EIO on sectors where it should not be data corruption.
>>
>> I added few lines with length-preserving mode with ESSIV + AEAD, please could you run luks2-integrity-test
>> in cryptsetup upstream?
>>
>> This patch adds the tests:
>> https://gitlab.com/cryptsetup/cryptsetup/commit/4c74ff5e5ae328cb61b44bf99f98d08ffee3366a
>>
>> It is ok on mainline kernel, fails with the patchset:
>>
>> # ./luks2-integrity-test
>> [aes-cbc-essiv:sha256:hmac-sha256:128:512][FORMAT][ACTIVATE]sha256sum: /dev/mapper/dmi_test: Input/output error
>> [FAIL]
>>  Expecting ee501705a084cd0ab6f4a28014bcf62b8bfa3434de00b82743c50b3abf06232c got .
>>
>> FAILED backtrace:
>> 77 ./luks2-integrity-test
>> 112 intformat ./luks2-integrity-test
>> 127 main ./luks2-integrity-test
>>
> 
> OK, I will investigate.
> 
> I did my testing in a VM using a volume that was created using a
> distro kernel, and mounted and used it using a kernel with these
> changes applied.
> 
> Likewise, if I take a working key.img and mode-test.img, i can mount
> it and use it on the system running these patches.
> 
> I noticed that this test uses algif_skcipher not algif_aead when it
> formats the volume, and so I wonder if the way userland creates the
> image is affected by this?

Not sure if I understand the question, but I do not think userspace even touch data area here
(except direct-io wiping after the format, but it does not read it back).

It only encrypts keyslots - and here we cannot use AEAD (in fact it is already
authenticated by a LUKS digest).

So if the data area uses AEAD (or composition of length-preserving mode and
some authentication tag like HMAC), we fallback to non-AEAD for keyslot encryption.

In short, to test it, you need to activate device (that works ok with your patches)
and *access* the data, testing LUKS format and just keyslot access will never use AEAD.

So init the data by direct-io writes, and try to read them back (with dd).

For testing data on dm-integrity (or dm-crypt with AEAD encryption stacked oved dm-integrity)
I used small utility, maybe it could be useful https://github.com/mbroz/dm_int_tools 

Milan