A weakness in the initial client taxonomy mechanism is from storing both
the Probe and Associate in struct sta_info. struct sta_info is created
after a client associates (or starts authentication frame exchange),
which means that any Probe Request frames sent prior to association are
not retained. The Associate Request frame has to be seen, and then
another Probe Request frame after association, before we have a
signature for the client.
Most clients send lots of Probe Request frames (lots and lots and lots
of Probes, actually), but a few do not. ChromeOS is notably sparing in
sending Probe Request frames, it can take a long time before a signature
for a ChromeOS device is available.
Store the most recent Probe Request frame in struct hostapd_sta_info
tracking list. When a struct sta_info is created, move the Probe Request
frame information from struct hostapd_sta_info to struct sta_info.
Signed-off-by: dgentry@google.com (Denton Gentry)
Signed-off-by: denny@geekhold.com (Denton Gentry)
Signed-off-by: rofrankel@google.com (Richard Frankel)
Signed-off-by: richard@frankel.tv (Richard Frankel)
Implement the signature mechanism described in the paper
"Passive Taxonomy of Wifi Clients using MLME Frame Contents"
published by Denton Gentry and Avery Pennarun.
http://research.google.com/pubs/pub45429.htmlhttps://arxiv.org/abs/1608.01725
This involves:
1. Add a CONFIG_TAXONOMY compile option. Enabling taxonomy incurs
a memory overhead of up to several kilobytes per associated
station.
2. If enabled, store the Probe Request and (Re)Associate Request frame in
struct sta_info.
3. Implement code to extract the ID of each Information Element,
plus selected fields and bitmasks from certain IEs, into a
descriptive text string. This is done in a new source file,
src/ap/taxonomy.c.
4. Implement a "signature qq:rr:ss:tt:uu:vv" command
in hostapd_cli to retrieve the signature.
Signatures take the form of a text string. For example, a signature
for the Nexus 5X is:
wifi4|probe:0,1,127,45,191,htcap:01ef,htagg:03,htmcs:0000ffff,vhtcap:338061b2,
vhtrxmcs:030cfffa,vhttxmcs:030cfffa,extcap:00000a0201000040|assoc:0,1,48,45,
221(0050f2,2),191,127,htcap:01ef,htagg:03,htmcs:0000ffff,vhtcap:339071b2,
vhtrxmcs:030cfffa,vhttxmcs:030cfffa,extcap:0000000000000040
Signed-off-by: dgentry@google.com (Denton Gentry)
Signed-off-by: denny@geekhold.com (Denton Gentry)
Signed-off-by: rofrankel@google.com (Richard Frankel)
Signed-off-by: richard@frankel.tv (Richard Frankel)
