Re: [Opensc-devel] CardOS 5.3 driver

[Jakub J. <jj...@re...>]

On 03/19/2017 10:30 PM, Douglas E Engert wrote:
> In regards to RSA_X_509, it may be the algorithm flags are wrong.
>
>  An RSA_X_509 operation to a card can be the same operation used to sign
> a padded block the size of the key, or to decrypt a key size block and
> return the results, without removing any padding, which allows for using
> other other padding mechanisms.

The cardos driver has its method to compute signature, which works with 
a little bit of guesswork [1] what method will be available and in case 
in the need of the others, it fixes the padding, if I read the comments 
and code right. This can not be used by the decryption, because you 
don't know what random bytes were added as a padding while encrypting.

> It could also be the senv is setting flags that tell the card to remove
> the padding whenit should not, or the card can not do RSA_X_509.
>
> It would be interesting to see an opensc-debug.log for
>  sc_pkcs15_decipher
> when it calls sc_get_encoding_flags in padding.c

Without the first commit in my branch it fails during setting up 
security environment [2].

After adding this commit, RSA_X_509 mechanism succeeds and RSA_PKCS 
fails (the logs also in the linked gist [2]). In the readme, there are 
also command I used to create the encrypted data using OpenSSL (in case 
there could go something wrong, though the tests were performed also 
with the same testsuite I use for other cards).

Let me know if you want the whole logs.

[1] 
https://github.com/OpenSC/OpenSC/blob/master/src/libopensc/card-cardos.c#L888
[2] 
https://gist.github.com/Jakuje/5a993d2b2d8a9cac35203599e49e6831#file-opensc-master-log

Jakub

> On Fri, Mar 17, 2017 at 6:38 AM, Jakub Jelen <jj...@re...
> <mailto:jj...@re...>> wrote:
>
>     Hello all,
>     we got several CardOS 5.3 cards that I tried to implement support for in
>     OpenSC. The initial detection is already merged [1].
>
>     The approach used CardOS 5.0 was not working everywhere so before
>     submitting the pull request with all the changes, I would like to hear
>     some feedback on some questionable parts and preferable verify that the
>     changes are not breaking anything that worked with CardOS 5.0 as
>     originally implemented years ago (adding szikora, who implemented
>     initial CardOS 5.0 support in PR#170) or if some of the concepts in new
>     cards work also in the old ones.
>
>     All changes are in my branch [2] are in four commits
>
>     The first two make the signatures working:
>       * Separately detect 5.3 version and use p1 = 0x41 for security
>     environment -- will it work also in the old cards?
>       * Remove SC_ALGORITHM_NEED_USAGE which prevented using
>     cardos_compute_signature() with 5.3 cards. Does 5.0 or older cards need
>     that?
>
>     The last two changes are more hackish and used to make decipher
>     mechanisms working (it looks like the card strips all the padding). Or
>     is there any possibility to disable in OpenSC RSA_X_509 raw decipher
>     mechanisms for this driver?
>
>     Comments, thoughts?
>
>     [1] https://github.com/OpenSC/OpenSC/commit/ac96e73
>     <https://github.com/OpenSC/OpenSC/commit/ac96e73>
>     [2] https://github.com/Jakuje/OpenSC/commits/jjelen-cardos53
>     <https://github.com/Jakuje/OpenSC/commits/jjelen-cardos53>
>
>     Regards,
>     --
>     Jakub Jelen
>     Software Engineer
>     Security Technologies
>     Red Hat
>
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-- 
Jakub Jelen
Software Engineer
Security Technologies
Red Hat