Make U2F devices blink on empty allow list

Currently when empty allow list is passed on as a parameter to
GetAssertion request, all requests to U2F devices are dropped. This is
in accordance with current version of the CTAP spec, as empty allow list
implies resident key credentials and U2F devices do not support resident

However, this behavior causes requests to U2F devices to be dropped
without U2F devices blinking, which causes user confusion. In order to
minimize user confusion, sent fake registration call to U2F devices for
GetAssertion request with empty allow list.

Bug: 860062
Change-Id: I8e62d01e46cd90f393035149254286b58a932e78
Commit-Queue: Jun Choi <>
Reviewed-by: Kim Paulhamus <>
Cr-Commit-Position: refs/heads/master@{#575363}
9 files changed