helpers.c: Fix undefined behavior in strndup()

Using strlen() or strdup() inside strndup() is problematic: if the
input string is not null-terminated, these functions can read past the
end of the buffer, which triggers undefined behavior. Rewrite the
function to never read past the provided `maxlen` bound.

Change-Id: Id34127024085879228626fbad59af03268ec5255
Signed-off-by: Xiang Wang <merle@hardenedliux.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/49741
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions