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Fix SCA vulnerability when using PVK and MSBLOB key formats

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This commit addresses a side-channel vulnerability present when
PVK and MSBLOB key formats are loaded into OpenSSL.
The public key was not computed using a constant-time exponentiation
function.

This issue was discovered and reported by the NISEC group at TAU Finland.

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9638)
This commit is contained in:
Cesar Pereida Garcia 2019-08-19 10:33:14 +03:00 committed by Matt Caswell
parent 7fafaf27c2
commit 55611d549b
1 changed files with 2 additions and 0 deletions
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2
crypto/pem/pvkfmt.c
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@ -327,6 +327,8 @@ static EVP_PKEY *b2i_dss(const unsigned char **in, unsigned int length,
} else { } else {
if (!read_lebn(&p, 20, &dsa->priv_key)) if (!read_lebn(&p, 20, &dsa->priv_key))
goto memerr; goto memerr;
/* Set constant time flag before public key calculation */
BN_set_flags(dsa->priv_key, BN_FLG_CONSTTIME);
/* Calculate public key */ /* Calculate public key */
if (!(dsa->pub_key = BN_new())) if (!(dsa->pub_key = BN_new()))
goto memerr; goto memerr;