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mobisys2018_nexmon_channel_state_information_extractor
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7
README.md
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@ -28,7 +28,12 @@ broadcasted UDP frame that includes the CSI information:
nexutil -m1
tcpdump -i wlan0 -xxx
```
Soon, we will publish a MATLAB script to analyze those raw CSI dumps.
To analyze the dumped CSI information, we provide some MATLAB functions in the
`matlab` directory. They rely on reading dumped CSI information from pcap files
created using tcpdump. As an example, we provide the captures created for our
MobiSys 2018 paper. The result looks as follows:
![SEEMOO logo](https://raw.githubusercontent.com/seemoo-lab/mobisys2018_nexmon_channel_state_information_extractor/master/matlab/result.png)
# Extract from our License

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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% ########### ########### ########## ########## %
% ############ ############ ############ ############ %
% ## ## ## ## ## ## ## %
% ## ## ## ## ## ## ## %
% ########### #### ###### ## ## ## ## ###### %
% ########### #### # ## ## ## ## # # %
% ## ## ###### ## ## ## ## # # %
% ## ## # ## ## ## ## # # %
% ############ ##### ###### ## ## ## ##### ###### %
% ########### ########### ## ## ## ########## %
% %
% S E C U R E M O B I L E N E T W O R K I N G %
% %
% License: %
% %
% Copyright (c) 2018 Jakob Link, Matthias Schulz %
% %
% Permission is hereby granted, free of charge, to any person obtaining a %
% copy of this software and associated documentation files (the %
% "Software"), to deal in the Software without restriction, including %
% without limitation the rights to use, copy, modify, merge, publish, %
% distribute, sublicense, and/or sell copies of the Software, and to %
% permit persons to whom the Software is furnished to do so, subject to %
% the following conditions: %
% %
% 1. The above copyright notice and this permission notice shall be %
% include in all copies or substantial portions of the Software. %
% %
% 2. Any use of the Software which results in an academic publication or %
% other publication which includes a bibliography must include %
% citations to the nexmon project a) and the paper cited under b) or %
% the thesis cited under c): %
% %
% a) "Matthias Schulz, Daniel Wegemer and Matthias Hollick. Nexmon: %
% The C-based Firmware Patching Framework. https://nexmon.org" %
% %
% b) "Matthias Schulz, Jakob Link, Francesco Gringoli, and Matthias %
% Hollick. Shadow Wi-Fi: Teaching Smartphones to Transmit Raw %
% Signals and to Extract Channel State Information to Implement %
% Practical Covert Channels over Wi-Fi. Accepted to appear in %
% Proceedings of the 16th ACM International Conference on Mobile %
% Systems, Applications, and Services (MobiSys 2018), June 2018." %
% %
% c) "Matthias Schulz. Teaching Your Wireless Card New Tricks: %
% Smartphone Performance and Security Enhancements through Wi-Fi %
% Firmware Modifications. Dr.-Ing. thesis, Technische Universität %
% Darmstadt, Germany, February 2018." %
% %
% 3. The Software is not used by, in cooperation with, or on behalf of %
% any armed forces, intelligence agencies, reconnaissance agencies, %
% defense agencies, offense agencies or any supplier, contractor, or %
% research associated. %
% %
% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS %
% OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF %
% MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. %
% IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY %
% CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, %
% TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE %
% SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function csi_plot(csi_buff_microwave, csi_buff_outside)
xticks = [4:25:254];
subplot(4,2,1)
plot(-128:127, abs(csi_buff_microwave(1,:)))
xlim([-128 127])
set(gca,'xtick',xticks - 129);
title('Nexus 5 in microwave')
ylabel('CSI Amplitude')
subplot(4,2,2)
plot(-128:127, abs(csi_buff_outside(1,:)))
xlim([-128 127])
set(gca,'xtick',xticks - 129);
title('Nexus 5 outside microwave')
ylabel('CSI Amplitude')
subplot(4,2,[3 5 7])
imagesc(abs(csi_buff_microwave))
set(gca,'xtick',xticks);
set(gca,'xticklabel',xticks - 129);
set(gca,'ytick',0:500:2500);
set(gca,'yticklabel',(0:500:2500)/10);
colorbar('southoutside')
xlabel('Subcarrier at 80 MHz bandwidth')
ylabel('Time in seconds')
subplot(4,2,[4 6 8])
imagesc(abs(csi_buff_outside))
set(gca,'xtick',xticks);
set(gca,'xticklabel',xticks - 129);
set(gca,'ytick',0:500:2500);
set(gca,'yticklabel',(0:500:2500)/10);
colorbar('southoutside')
xlabel('Subcarrier at 80 MHz bandwidth')
ylabel('Time in seconds')
end

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%READCSI Extract and interpret CSI values.
% READCSI(BASE_FILENAME, SHOULD_SAVE, SHOULD_PLOT) opens the
% BASE_FILENAME.pcap to extract channel state information (CSI) dumped
% using nexmon's CSI Extractor firmware patch. If SHOULD_SAVE is 1,
% extracted values will be written to BASE_FILENAME.mat. If SHOULD_PLOT
% is 1, then CSI values will directly be plotted.
%
% Payload format:
% 14 byte: Ethernet header
% 20 byte: IPv4 header
% 8 byte: UDP header
% 4 byte: Magic String "CSIS"(0x43 0x53 0x49 0x53)
% 6 byte: HW address
% 4 byte: reserved
% 1020 byte: 255 CSI value pairs
%
% CSI value pair format:
% 2 byte: two's complement real
% 2 byte: two's complement imag
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% ########### ########### ########## ########## %
% ############ ############ ############ ############ %
% ## ## ## ## ## ## ## %
% ## ## ## ## ## ## ## %
% ########### #### ###### ## ## ## ## ###### %
% ########### #### # ## ## ## ## # # %
% ## ## ###### ## ## ## ## # # %
% ## ## # ## ## ## ## # # %
% ############ ##### ###### ## ## ## ##### ###### %
% ########### ########### ## ## ## ########## %
% %
% S E C U R E M O B I L E N E T W O R K I N G %
% %
% License: %
% %
% Copyright (c) 2018 Jakob Link, Matthias Schulz %
% %
% Permission is hereby granted, free of charge, to any person obtaining a %
% copy of this software and associated documentation files (the %
% "Software"), to deal in the Software without restriction, including %
% without limitation the rights to use, copy, modify, merge, publish, %
% distribute, sublicense, and/or sell copies of the Software, and to %
% permit persons to whom the Software is furnished to do so, subject to %
% the following conditions: %
% %
% 1. The above copyright notice and this permission notice shall be %
% include in all copies or substantial portions of the Software. %
% %
% 2. Any use of the Software which results in an academic publication or %
% other publication which includes a bibliography must include %
% citations to the nexmon project a) and the paper cited under b) or %
% the thesis cited under c): %
% %
% a) "Matthias Schulz, Daniel Wegemer and Matthias Hollick. Nexmon: %
% The C-based Firmware Patching Framework. https://nexmon.org" %
% %
% b) "Matthias Schulz, Jakob Link, Francesco Gringoli, and Matthias %
% Hollick. Shadow Wi-Fi: Teaching Smartphones to Transmit Raw %
% Signals and to Extract Channel State Information to Implement %
% Practical Covert Channels over Wi-Fi. Accepted to appear in %
% Proceedings of the 16th ACM International Conference on Mobile %
% Systems, Applications, and Services (MobiSys 2018), June 2018." %
% %
% c) "Matthias Schulz. Teaching Your Wireless Card New Tricks: %
% Smartphone Performance and Security Enhancements through Wi-Fi %
% Firmware Modifications. Dr.-Ing. thesis, Technische Universität %
% Darmstadt, Germany, February 2018." %
% %
% 3. The Software is not used by, in cooperation with, or on behalf of %
% any armed forces, intelligence agencies, reconnaissance agencies, %
% defense agencies, offense agencies or any supplier, contractor, or %
% research associated. %
% %
% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS %
% OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF %
% MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. %
% IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY %
% CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, %
% TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE %
% SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function csi_buff = readcsi(base_filename, should_save, should_plot)
%% parameters
% configure WLAN object and get parameters
cfgVHT = wlanVHTConfig; % legacy mode
%cfgVHT.Modulation = 'OFDM'; % OFDM
cfgVHT.ChannelBandwidth = 'CBW80'; % 20MHz
cfgVHT.MCS = 0; % BPSK 6Mbps
cfgVHT.NumTransmitAntennas = 1; % one antenna
FFTLength = helperFFTLength(cfgVHT); % get fft length
% get data, pilot, and null carrier indices
[dataIdx,pilotIdx] = helperSubcarrierIndices(cfgVHT,'VHT');
dpIdx = [dataIdx; pilotIdx];
nullIdx = 1:FFTLength;
nullIdx(dpIdx) = [];
%% helper
% anonymous function: sign extend and convert binary 14-bit-twocompl to int16
twos2dec = @(x) typecast(uint16(bin2dec(x)),'int16');
%% read file
p = readpcap();
p.open([base_filename '.pcap']);
%n = min(length(p.all()),100);
n = p.length();
p.from_start();
ts = zeros(n,1);
% matrix to store calculated csi for each packet
csi_buff = complex(zeros(n,FFTLength),0);
k = 1; % target matrix counter
% iterate over each packet
while (k <= n)
f = p.next();
if isempty(f)
disp('no more frames');
break;
end
if f.header.orig_len ~= 1076
continue;
end
ts(k) = double(f.header.ts_sec) + double(f.header.ts_usec) * 1e-6;
payload = f.payload;
% convert to binary
binary = dec2bin(payload,32);
%disp(dec2hex(payload(14),8))
% remove none-csi
binary = binary(15:end,:);
% extract imaginary and real parts
real_b = binary(:,1:16);
imag_b = binary(:,17:end);
% group to cells
real_b_cells = num2cell(real_b,2);
imag_b_cells = num2cell(imag_b,2);
% apply twos2dec for each cell
real_d = cellfun(twos2dec,real_b_cells);
imag_d = cellfun(twos2dec,imag_b_cells);
% build complex numbers
cmplx = complex(double(real_d), double(imag_d));
% throw away constant value at beginning
% and extract used carriers
if FFTLength <= 254
% for 20 and 40 MHz
cmplx_bw = fftshift(cmplx(2:FFTLength+1));
else
% exact format for 80 MHz currently unknown
% only 255 values in CSI UDP, but FFTLength is 256
cmplx_bw = fftshift([cmplx(1:FFTLength-1); 10000]);
end
% zero set null carriers
cmplx_bw(nullIdx) = 0.0;
% store csi
csi_buff(k,:) = cmplx_bw.';
k = k + 1;
end
%% save results
if (should_save)
save([base_filename '.mat'], 'csi_buff', '-v7.3');
end
%% plot
if (should_plot)
% y-Axis ticks and ticklabels for phase
ticky = [-180:45:180];
tickyL = {'-180','','-90','','0°', '', '90°', '', '180°'};
% x-Axis
x = -FFTLength/2:FFTLength/2-1;
for n = 1:size(csi_buff,1)
plot_chan = csi_buff(n,:);
figure(1);
% plot magnitude
subplot(2,1,1)
bha = bar(x,abs(plot_chan),'BarWidth',1);
set(bha,'FaceColor',[0 0 1])
set(bha,'EdgeColor',[0 0 0])
title('CSI Magnitude')
xlabel('Subcarrier Index')
ylabel('Magnitude')
grid on
myAxis = axis();
axis([min(x), max(x), myAxis(3), myAxis(4)])
% plot phase
subplot(2,1,2)
bha = bar(x,rad2deg(angle(plot_chan)),'BarWidth',1);
set(bha,'FaceColor',[1 0 0])
set(bha,'EdgeColor',[0 0 0])
title('CSI Phase')
xlabel('Subcarrier Index')
ylabel('Phase in °')
grid on
set(gca,'YTick',ticky)
set(gca,'YTickLabel',tickyL)
myAxis = axis();
axis([min(x), max(x), myAxis(3), myAxis(4)])
% wait for user input
waitforbuttonpress();
end
end
end

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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% ########### ########### ########## ########## %
% ############ ############ ############ ############ %
% ## ## ## ## ## ## ## %
% ## ## ## ## ## ## ## %
% ########### #### ###### ## ## ## ## ###### %
% ########### #### # ## ## ## ## # # %
% ## ## ###### ## ## ## ## # # %
% ## ## # ## ## ## ## # # %
% ############ ##### ###### ## ## ## ##### ###### %
% ########### ########### ## ## ## ########## %
% %
% S E C U R E M O B I L E N E T W O R K I N G %
% %
% License: %
% %
% Copyright (c) 2018 Matthias Schulz %
% %
% Permission is hereby granted, free of charge, to any person obtaining a %
% copy of this software and associated documentation files (the %
% "Software"), to deal in the Software without restriction, including %
% without limitation the rights to use, copy, modify, merge, publish, %
% distribute, sublicense, and/or sell copies of the Software, and to %
% permit persons to whom the Software is furnished to do so, subject to %
% the following conditions: %
% %
% 1. The above copyright notice and this permission notice shall be %
% include in all copies or substantial portions of the Software. %
% %
% 2. Any use of the Software which results in an academic publication or %
% other publication which includes a bibliography must include %
% citations to the nexmon project a) and the paper cited under b) or %
% the thesis cited under c): %
% %
% a) "Matthias Schulz, Daniel Wegemer and Matthias Hollick. Nexmon: %
% The C-based Firmware Patching Framework. https://nexmon.org" %
% %
% b) "Matthias Schulz, Jakob Link, Francesco Gringoli, and Matthias %
% Hollick. Shadow Wi-Fi: Teaching Smartphones to Transmit Raw %
% Signals and to Extract Channel State Information to Implement %
% Practical Covert Channels over Wi-Fi. Accepted to appear in %
% Proceedings of the 16th ACM International Conference on Mobile %
% Systems, Applications, and Services (MobiSys 2018), June 2018." %
% %
% c) "Matthias Schulz. Teaching Your Wireless Card New Tricks: %
% Smartphone Performance and Security Enhancements through Wi-Fi %
% Firmware Modifications. Dr.-Ing. thesis, Technische Universität %
% Darmstadt, Germany, February 2018." %
% %
% 3. The Software is not used by, in cooperation with, or on behalf of %
% any armed forces, intelligence agencies, reconnaissance agencies, %
% defense agencies, offense agencies or any supplier, contractor, or %
% research associated. %
% %
% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS %
% OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF %
% MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. %
% IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY %
% CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, %
% TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE %
% SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
classdef readpcap < handle
%READPCAP Summary of this class goes here
% Detailed explanation goes here
properties
fid;
global_header;
prev_len;
end
methods
function open(obj, filename)
obj.fid = fopen(filename);
% should be 0xA1B2C3D4
obj.global_header.magic_number = fread(obj.fid, 1, '*uint32');
% major version number
obj.global_header.version_major = fread(obj.fid, 1, '*uint16');
% minor version number
obj.global_header.version_minor = fread(obj.fid, 1, '*uint16');
% GMT to local correction
obj.global_header.thiszone = fread(obj.fid, 1, '*int32');
% accuracy of timestamps
obj.global_header.sigfigs = fread(obj.fid, 1, '*uint32');
% max length of captured packets, in octets
obj.global_header.snaplen = fread(obj.fid, 1, '*uint32');
% data link type
obj.global_header.network = fread(obj.fid, 1, '*uint32');
end
function frame = next(obj)
% timestamp seconds
frame.header.ts_sec = fread(obj.fid, 1, '*uint32');
% timestamp microseconds
frame.header.ts_usec = fread(obj.fid, 1, '*uint32');
% number of octets of packet saved in file
frame.header.incl_len = fread(obj.fid, 1, '*uint32');
% actual length of packet
frame.header.orig_len = fread(obj.fid, 1, '*uint32');
if isempty(frame.header.incl_len)
frame = [];
return;
end
% packet data
if (mod(frame.header.incl_len,4)==0)
frame.payload = fread(obj.fid, frame.header.incl_len/4, '*uint32');
else
frame.payload = fread(obj.fid, frame.header.incl_len, '*uint8');
end
end
function frame = next_header(obj)
% timestamp seconds
frame.header.ts_sec = fread(obj.fid, 1, '*uint32');
% timestamp microseconds
frame.header.ts_usec = fread(obj.fid, 1, '*uint32');
% number of octets of packet saved in file
frame.header.incl_len = fread(obj.fid, 1, '*uint32');
% actual length of packet
frame.header.orig_len = fread(obj.fid, 1, '*uint32');
if isempty(frame.header.incl_len)
frame = [];
return;
end
fseek(obj.fid, frame.header.incl_len, 0);
end
function from_start(obj)
fseek(obj.fid, 24, -1);
end
function frames = all(obj)
i = 1;
frames = cell(1);
obj.from_start();
while true
frame = obj.next();
if isempty(frame)
break;
end
frames{i} = frame;
i = i + 1;
end
end
function len = length(obj)
len = 0;
obj.from_start();
f = obj.next_header();
while ~isempty(f)
len = len + 1;
f = obj.next_header();
end
end
end
end

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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% ########### ########### ########## ########## %
% ############ ############ ############ ############ %
% ## ## ## ## ## ## ## %
% ## ## ## ## ## ## ## %
% ########### #### ###### ## ## ## ## ###### %
% ########### #### # ## ## ## ## # # %
% ## ## ###### ## ## ## ## # # %
% ## ## # ## ## ## ## # # %
% ############ ##### ###### ## ## ## ##### ###### %
% ########### ########### ## ## ## ########## %
% %
% S E C U R E M O B I L E N E T W O R K I N G %
% %
% License: %
% %
% Copyright (c) 2018 Jakob Link, Matthias Schulz %
% %
% Permission is hereby granted, free of charge, to any person obtaining a %
% copy of this software and associated documentation files (the %
% "Software"), to deal in the Software without restriction, including %
% without limitation the rights to use, copy, modify, merge, publish, %
% distribute, sublicense, and/or sell copies of the Software, and to %
% permit persons to whom the Software is furnished to do so, subject to %
% the following conditions: %
% %
% 1. The above copyright notice and this permission notice shall be %
% include in all copies or substantial portions of the Software. %
% %
% 2. Any use of the Software which results in an academic publication or %
% other publication which includes a bibliography must include %
% citations to the nexmon project a) and the paper cited under b) or %
% the thesis cited under c): %
% %
% a) "Matthias Schulz, Daniel Wegemer and Matthias Hollick. Nexmon: %
% The C-based Firmware Patching Framework. https://nexmon.org" %
% %
% b) "Matthias Schulz, Jakob Link, Francesco Gringoli, and Matthias %
% Hollick. Shadow Wi-Fi: Teaching Smartphones to Transmit Raw %
% Signals and to Extract Channel State Information to Implement %
% Practical Covert Channels over Wi-Fi. Accepted to appear in %
% Proceedings of the 16th ACM International Conference on Mobile %
% Systems, Applications, and Services (MobiSys 2018), June 2018." %
% %
% c) "Matthias Schulz. Teaching Your Wireless Card New Tricks: %
% Smartphone Performance and Security Enhancements through Wi-Fi %
% Firmware Modifications. Dr.-Ing. thesis, Technische Universität %
% Darmstadt, Germany, February 2018." %
% %
% 3. The Software is not used by, in cooperation with, or on behalf of %
% any armed forces, intelligence agencies, reconnaissance agencies, %
% defense agencies, offense agencies or any supplier, contractor, or %
% research associated. %
% %
% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS %
% OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF %
% MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. %
% IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY %
% CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, %
% TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE %
% SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
disp('Reading PCAP files - this takes a while ...');
csi_buff_microwave = readcsi('experiment2c_microwave', 0, 0);
csi_buff_outside = readcsi('experiment2c_outside', 0, 0);
csi_plot(csi_buff_microwave, csi_buff_outside);