Commit cb8164b0 authored by armfazh's avatar armfazh Committed by Pauli
Browse files

Fix tls_cbc_digest_record is slow using SHA-384 and short messages 



The formula used for this is now

kVarianceBlocks = ((255 + 1 + md_size + md_block_size - 1) / md_block_size) + 1

Notice that md_block_size=64 for SHA256, which results on the
magic constant kVarianceBlocks = 6.
However, md_block_size=128 for SHA384 leading to kVarianceBlocks = 4.

CLA:trivial

Reviewed-by: default avatarMatt Caswell <matt@openssl.org>
Reviewed-by: default avatarPaul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/7342)
parent dc5831da

ssl/s3_cbc.c

+3 −2
Original line number Diff line number Diff line
@@ -256,12 +256,13 @@ int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx, 
     * of hash termination (0x80 + 64-bit length) don't fit in the final

     * block, we say that the final two blocks can vary based on the padding.

     * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not

     * required to be minimal. Therefore we say that the final six blocks can

     * required to be minimal. Therefore we say that the final |variance_blocks|

     * blocks can

     * vary based on the padding. Later in the function, if the message is

     * short and there obviously cannot be this many blocks then

     * variance_blocks can be reduced.

     */

    variance_blocks = is_sslv3 ? 2 : 6;

    variance_blocks = is_sslv3 ? 2 : ( ((255 + 1 + md_size + md_block_size - 1) / md_block_size) + 1);

    /*

     * From now on we're dealing with the MAC, which conceptually has 13

     * bytes of `header' before the start of the data (TLS) or 71/75 bytes