It was not easily possible to separate configuration of an interface and
credentials when using the configuration file instead of the control
interface or D-Bus interface for setting up the network profiles. This
makes it hard to distribute configuration across a set of nodes which
use wpa_supplicant without also having to store credentials in the same
file. While this can be solved via scripting, having a native way to
achieve this would be preferable.
Turns out there already is a framework to have external password
storages. It only had a single "test" backend though, which is kind of
an in-memory store which gets initialized with all passwords up front
and is mainly for testing purposes. This isn't really suitable for the
above use case: the backend cannot be initialized as part of the central
configuration given that it needs the credentials, and we want to avoid
scripting.
This commit thus extends the infrastructure to implement a new backend,
which instead uses a simple configuration file containing key-value
pairs. The file follows the format which wpa_supplicant.conf(5) uses:
empty lines and comments are ignored, while passwords can be specified
with simple `password-name=password-value` assignments.
With this new backend, splitting up credentials and configuration
becomes trivial:
# /etc/wpa_supplicant/wpa_supplicant.conf
ext_password_backend=file:/etc/wpa_supplicant/psk.conf
network={
ssid="foobar"
psk=ext:foobar
}
# /etc/wpa_supplicant/psk.conf
foobar=ecdabff9c80632ec6fcffc4a8875e95d45cf93376d3b99da6881298853dc686b
Alternative approaches would be to support including other configuration
files in the main configuration, such that common configuration and
network declarations including credentials are split up into separate
files. But the implementation would probably have been more complex
compared to reusing the already-existing framework for external password
backends.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
e680a51e94