openwifi/doc/app_notes/csi_fuzzer.md
2021-07-06 12:08:43 +02:00

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SPDX-FileCopyrightText: 2021 UGent
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[ACM WiSec 2021. Openwifi CSI fuzzer for authorized sensing and covert channels](https://dl.acm.org/doi/pdf/10.1145/3448300.3468255)
CSI (Channel State Information) of WiFi systems is available in some WiFi chips and can be used for sensing the environment (keystrokes, people, object) passively and secretly.
## Concept
How could a CSI fuzzer stop unauthorized sensing?
![](./csi-fuzzer-system-before-vs-now.png)
CSI fuzzer implementation principle.
![](./csi-fuzzer-principle.png)
## Demo instructions
Thanks to the full-duplex capability and CSI extraction feature of openwifi, you can monitor the artificial channel response via [side channel](./csi.md) by Tx-Rx over the air coupling without affecting the normal operation/traffic of openwifi. Before the self-monitoring, the auto-mute during Tx needs to be disabled.
The full demo steps are:
```
ssh root@192.168.10.122
(password: openwifi)
cd openwifi
./fosdem-11ag.sh
(setup openwifi AP)
./sdrctl dev sdr0 set reg xpu 1 1
(Disable auto-muting to listen self-TX)
insmod side_ch.ko num_eq_init=0
./side_ch_ctl wh1h2001
./side_ch_ctl wh6hffffffff
(Let's only monitor self-beacon-TX CSI over-the-air loopback)
./side_ch_ctl g1
```
Go to openwifi/user_space/side_ch_ctl_src, and run `python3 side_info_display.py 0`. You should see the over-the-air loopback CSI when CSI fuzzer is not enabled. Then stop the python3 side_info_display.py script to ease the next step.
Start another ssh session to the openwifi board:
```
ssh root@192.168.10.122
(password: openwifi)
cd openwifi
./csi_fuzzer_scan.sh 1
(CSI fuzzer applies possible artificial CSI by scanning all values)
(csi_fuzzer.sh is called. Please read both scripts to understand these commands)
```
Go to openwifi/user_space/side_ch_ctl_src, and run `python3 side_info_display.py 0`. Now you should see that CSI keeps changing like in this [video](https://youtu.be/aOPYwT77Qdw).
# Further explanation on parameters
CSI fuzzer in openwifi system architecture and related commands.
![](./csi-fuzzer-implementation.png)
# Example fuzzed CSI
CSI self-monitoring before fuzzing.
![](./csi-fuzzer-beacon-ant-back-0.jpg)
CSI self-monitoring after fuzzing command: `csi_fuzzer.sh 1 45 0 13`
![](./csi-fuzzer-beacon-ant-back-1-45-0-13.jpg)
`csi_fuzzer_scan.sh` can scan the c1 and c2 in different styles/modes by calling `csi_fuzzer.sh`.