Hi,
On 2/8/21 0:44, aitor wrote:
Better said, the suid binary can check whether or not the gui has
handled the signal as expected because
the default behavior of SIGUSR1 (User defined signal 1) is to
terminate the process. See the table at the
end of the link:
https://en.wikipedia.org/wiki/Signal_(IPC)#POSIX_signals
<https://en.wikipedia.org/wiki/Signal_(IPC)#POSIX_signals>
I.e., when such a intruder is acting the
PSTAT_BINARY="SOMEWHERE_DEFINED_NAME" with process ID="PID"
no longer exists.
Here you are the code:
https://www.gnuinos.org/suid/ <https://www.gnuinos.org/suid/>
** HOWTO: **
1) Install Jude Nelson's libpstat:
$ git clone https://github.com/jcnelson/libpstat.git
$ cd libpstat
$ make OS=LINUX
$ sudo make install PREFIX=/ INCLUDE_PREFIX=/usr
2) Open an empty directory and download the files:
$ wget https://www.gnuinos.org/suid/Makefile
$ wget https://www.gnuinos.org/suid/gui.c
$ wget https://www.gnuinos.org/suid/suid.c
$ wget https://www.gnuinos.org/suid/intruder.c
3) Install libgtk-3-dev:
$ sudo apt-get install libgtk-3-dev
4) Build the files:
$ make
5) Run the GUI in the command line and click on the button several times:
$ ./gui
You'll get:
From GUI: Received a 10 (SIGUSR1) signal sent from the suid
From SUID: Ok, go on!
6) Open a new tab in the command line and run the intruder (the GUI
remains running):
$ ./intruder
You'll get:
Foreign PID to use: 4301
From SUID: Stop, you're an intruder!
If you have a look at the code of both programs, they're trying to do
the same (using the intruder a foreign pid).
Keep in mind that, for our testing purposes, all the binaries must be
located in the same directory, since
we're using:
key_t key = ftok(".", 's');
to access the same shared memory segment.
Cheers,
Aitor.
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