Connecting open network with nmcli is working even while providing password

[Alexis Lothoré <alexis lothore gmail com>]

Hello,
I am currently working on a Linux-based embedded device, which heavily
relies on Network Manager for the connectivity side. I am using nmcli
to manage some parts of the connectivity. The firmware is generated
with buildroot 2018.02, so Network Manager is on version 1.10. My
issue is the following : I have set an access point with the following
parameters : SSID set to "Negative, no security, beacon interval set
to 100, channel set to 6.
I am trying to connect this access point with the following command :
nmcli dev wifi connect Negative password 123456789. Since security is
disabled on my access point, I expect this command to fail (I should
have called "nmcli dev wifi connect Negative").

However, the connection process goes smoothly and NetworkManager
manages to connect to my AP :

# nmcli dev wifi connect Negative password 12345678
[ 7405.844425] Connecting with 00:14:d1:e0:69:97 ssid "Negative", len
(8) channel=6
[ 7405.844425]
[ 7405.903392] wl_bss_connect_done succeeded with 00:14:d1:e0:69:97
[ 7405.939109] wl_bss_connect_done succeeded with 00:14:d1:e0:69:97
Device 'wlan0' successfully activated with
'4f09ed1c-393c-444f-92cc-5b7328568ad5'.

In NetworkManager logs, I see the following :

Jan  1 02:03:22 NetworkManager[675]: <info>  [946692202.4946] keyfile:
add connection in-memory
(4f09ed1c-393c-444f-92cc-5b7328568ad5,"Negative")
Jan  1 02:03:22 NetworkManager[675]: <info>  [946692202.5449] device
(wlan0): Activation: starting connection 'Negative'
(4f09ed1c-393c-444f-92cc-5b7328568ad5)
Jan  1 02:03:22 NetworkManager[675]: <info>  [946692202.7058]
settings-connection[0x12e4338,4f09ed1c-393c-444f-92cc-5b7328568ad5]:
write: successfully commited (keyfile: update
/etc/NetworkManager/system-connections/Negative
(4f09ed1c-393c-444f-92cc-5
Jan  1 02:03:22 NetworkManager[675]: <info>  [946692202.7126] audit:
op="connection-add-activate"
uuid="4f09ed1c-393c-444f-92cc-5b7328568ad5" name="Negative" pid=687
uid=0 result="success"
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.1336] device
(wlan0): state change: disconnected -> prepare (reason 'none',
sys-iface-state: 'managed')
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.1437] manager:
NetworkManager state is now CONNECTING
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.2078] device
(wlan0): state change: prepare -> config (reason 'none',
sys-iface-state: 'managed')
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.2198] device
(wlan0): Activation: (wifi) connection 'Negative' requires no
security.  No secrets needed.
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.2214] Config:
added 'ssid' value 'Negative'
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.2223] Config:
added 'scan_ssid' value '1'
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.2248] Config:
added 'bgscan' value 'simple:30:-80:86400'
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.2250] Config:
added 'key_mgmt' value 'NONE'
Jan  1 02:03:23 NetworkManager[675]: <info>  [946692203.3280] device
(wlan0): supplicant interface state: ready -> scanning
Jan  1 02:03:24 NetworkManager[675]: <info>  [946692204.7803] device
(wlan0): supplicant interface state: scanning -> associating
Jan  1 02:03:24 NetworkManager[675]: <info>  [946692204.8083] device
(wlan0): supplicant interface state: associating -> completed
Jan  1 02:03:24 NetworkManager[675]: <info>  [946692204.8088] device
(wlan0): Activation: (wifi) Stage 2 of 5 (Device Configure)
successful.  Connected to wireless network 'Negative'.
Jan  1 02:03:24 NetworkManager[675]: <info>  [946692204.9426] device
(wlan0): state change: config -> ip-config (reason 'none',
sys-iface-state: 'managed')
Jan  1 02:03:24 NetworkManager[675]: <info>  [946692204.9760] dhcp4
(wlan0): activation: beginning transaction (timeout in 45 seconds)
Jan  1 02:03:24 NetworkManager[675]: <info>  [946692204.9949] dhcp4
(wlan0): dhclient started with pid 692
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.4248] dhcp4
(wlan0):   address 192.168.10.103
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.4264] dhcp4
(wlan0):   plen 24 (255.255.255.0)
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.4270] dhcp4
(wlan0):   gateway 192.168.10.1
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.4330] dhcp4
(wlan0):   lease time 604800
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.4343] dhcp4
(wlan0):   nameserver '192.168.10.1'
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.4344] dhcp4
(wlan0):   domain name 'TRENDnet'
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.4346] dhcp4
(wlan0): state changed unknown -> bound
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.5032] device
(wlan0): state change: ip-config -> ip-check (reason 'none',
sys-iface-state: 'managed')
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.5399] device
(wlan0): state change: ip-check -> secondaries (reason 'none',
sys-iface-state: 'managed')
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.5619] device
(wlan0): state change: secondaries -> activated (reason 'none',
sys-iface-state: 'managed')
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.5756] manager:
NetworkManager state is now CONNECTED_LOCAL
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.6060] manager:
NetworkManager state is now CONNECTED_SITE
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.6120] policy:
set 'Negative' (wlan0) as default for IPv4 routing and DNS
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.6216] device
(wlan0): Activation: successful, device activated.
Jan  1 02:03:25 dbus-daemon[234]: [system] Activating service
name='org.freedesktop.nm_dispatcher' requested by ':1.10' (uid=0
pid=675 comm="/usr/sbin/NetworkManager ") (using servicehelper)
Jan  1 02:03:25 NetworkManager[675]: <info>  [946692205.6744] manager:
NetworkManager state is now CONNECTED_GLOBAL
Jan  1 02:03:26 NetworkManager[675]: <warn>  [946692206.9398]
platform-linux: do-add-ip6-address[3: fe80::276:b1ff:fe07:47]: failure
22 (Invalid argument)

My question here is : is it a bug or a feature ? From syslog's logs,
it does seem that Network check the wifi security, and just ignore the
provided password if it is not needed. Could you confirm that it is
the expected behavior ? Or does Network Manager is supposed to raise
an error ? In my case, this scenario belongs to a group of tests for a
certification, so I would like to know if I am supposed to manage it
in my upper binary managing connection with nmcli or if it is supposed
to be fixed/worked around in Network Manager.

Regards,
-- 
Alexis Lothoré