validation: Report lack of signature

If we're trying to cryptographically validate a message, not having a
signature is not a success (exit 0). Use a specific return code for this
condition and report it.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
1 file changed