Fix CVE-2021-33560: Libgcrypt before 1.8.8 and 1.9.x before 1.9.3
mishandles ElGamal encryption because it lacks exponent blinding to
address a side-channel attack against mpi_powm, and the window size is
not chosen appropriately. (There is also an interoperability problem
because the selection of the k integer value does not properly consider
the differences between basic ElGamal encryption and generalized ElGamal
encryption.) This, for example, affects use of ElGamal in OpenPGP.
https://dev.gnupg.org/T5305
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
878b57ca3b