test/py: efi_secboot: add a test for a forged signed image

In this test case, a image binary, helloworld.efi.signed, is willfully
modified to print a corrupted message while the signature itself is
unchanged.

This binary must be rejected under secure boot mode.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
3 files changed