dh: fix libcrypto leak via ssh_dh_keypair_set_keys
Upon SSH_OK, callers of ssh_dh_keypair_set_keys expect for ownership
of the priv and pub values to be transferred away and eventually
later managed by way of the struct dh_ctx at hand.
The mbedTLS and gcrypt builds transfer ownership of these values in
that way, but the libcrypto ssh_dh_keypair_set_keys is copying the
given values with BN_dup. This causes a memory leak that can be
seen with pkd and valgrind:
valgrind --leak-check=full \ ./pkd_hello -i1 -t torture_pkd_openssh_dsa_rsa_diffie_hellman_group16_sha512
Fix the leak by replacing the BN_dup with direct assignment.
Now the bignums will eventually be freed via ssh_dh_cleanup.
Signed-off-by: Jon Simons <email@example.com>
Reviewed-by: Andreas Schneider <firstname.lastname@example.org>