Normally in OpenSSL EC groups always have a co-factor present and this is
used in side channel resistant code paths. However, in some cases, it is
possible to construct a group using explicit parameters (instead of using a
named curve). In those cases it is possible that such a group does not have
the cofactor present. This can occur even where all the parameters match a
known named curve. If such a curve is used then OpenSSL falls back to
non-side channel resistant code paths which may result in full key recovery
during an ECDSA signature operation. In order to be vulnerable an attacker
would have to have the ability to time the creation of a large number of
signatures where explicit parameters with no co-factor present are in use
by an application using libcrypto. For the avoidance of doubt libssl is not
vulnerable because explicit parameters are never used. Fixed in OpenSSL
1.1.1d (Affected 1.1.1-1.1.1c). Fixed in OpenSSL 1.1.0l (Affected
1.1.0-1.1.0k). Fixed in OpenSSL 1.0.2t (Affected 1.0.2-1.0.2s).

mdeslaur

mdeslaur

code isn't compiled into edk2