[U-Boot] [PATCH 2/4] rsa: Verify RSA padding programatically

[Simon Glass]

On 8 November 2016 at 11:53, aduda <aduda at meraki.com> wrote:
> From: Andrew Duda <aduda at meraki.com>
>
> Padding verification was done against static SHA/RSA pair arrays which
> take up a lot of static memory, are mostly 0xff, and cannot be reused
> for additional SHA/RSA pairings. The padding can be easily computed
> according to PKCS#1v2.1 as:
>
>   EM = 0x00 || 0x01 || PS || 0x00 || T
>
> where PS is (emLen - tLen - 3) octets of 0xff and T is DER encoding
> of the hash.
>
> Store DER prefix in checksum_algo and create rsa_verify_padding
> function to handle verification of a message for any SHA/RSA pairing.
>
> Signed-off-by: Andrew Duda <aduda at meraki.com>
> Signed-off-by: aduda <aduda at meraki.com>
> ---
>
>  common/image-sig.c            |   9 ++--
>  include/image.h               |   3 +-
>  include/u-boot/rsa-checksum.h |   4 --
>  include/u-boot/sha1.h         |   3 ++
>  include/u-boot/sha256.h       |   3 ++
>  lib/rsa/rsa-checksum.c        | 121 ------------------------------------------
>  lib/rsa/rsa-verify.c          |  38 ++++++++++++-
>  lib/sha1.c                    |   5 ++
>  lib/sha256.c                  |   6 +++
>  9 files changed, 61 insertions(+), 131 deletions(-)

Reviewed-by: Simon Glass <sjg at chromium.org>

How much memory does this save?