[0/5] crypto: lib/sha256 - cleanup/optimization

Message

Arvind Sankar Oct. 19, 2020, 3:30 p.m. UTC

Patch 1 -- Use memzero_explicit() instead of structure assignment/plain
memset() to clear sensitive state.

Patch 2 -- I am not sure about this one: currently the temporary
variables used in the generic sha256 implementation are cleared, but the
clearing is optimized away due to lack of compiler barriers. I don't
think it's really necessary to clear them, but I'm not a cryptanalyst,
so I would like comment on whether it's indeed safe not to, or we should
instead add the required barriers to force clearing.

The last three patches are optimizations for generic sha256.

Arvind Sankar (5):
  crypto: Use memzero_explicit() for clearing state
  crypto: lib/sha256 - Don't clear temporary variables
  crypto: lib/sha256 - Clear W[] in sha256_update() instead of
    sha256_transform()
  crypto: lib/sha256 - Unroll SHA256 loop 8 times intead of 64
  crypto: lib/sha256 - Unroll LOAD and BLEND loops

 include/crypto/sha1_base.h   |   3 +-
 include/crypto/sha256_base.h |   3 +-
 include/crypto/sha512_base.h |   3 +-
 include/crypto/sm3_base.h    |   3 +-
 lib/crypto/sha256.c          | 202 ++++++++++-------------------------
 5 files changed, 62 insertions(+), 152 deletions(-)