Handler javaslatára teszteltem az exec-shield patchet (lásd előző cikk) két tesztprogrammal. A tesztprogramok a libsafe-2.0-16 és a paxtest-0.9.1 voltak. Az eredmények érdekesek. Lássuk a teszteket:
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sunshine:/home/trey/exec/libsafe-2.0-16/exploits# echo "2" > /proc/sys/kernel/exec-shield
sunshine:/home/trey/exec/libsafe-2.0-16/exploits# cat /proc/sys/kernel/exec-shield
2
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libsafe-2.0-16 (exec-shield teljes védelem):
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./canary-exploit
This program tries to use printf("%n") to overwrite the
return address on the stack.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./exploit-non-exec-stack
This program demonstrates how a (stack) buffer overflow
can attack linux kernels with *non-executable* stacks.
This is variation on return-int-libc attack.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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---------------------------------------------------------------------
trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t1
This program tries to use strcpy() to overflow the buffer.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
Szegmens hiba
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t1w
This program tries to use strcpy() to overflow the buffer.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
Szegmens hiba
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t3
This program will exec() a new program. The new program will
overflow the buffer using strcpy().
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
Szegmens hiba
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t3w
This program will exec() a new program. The new program will
overflow the buffer using strcpy().
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
Szegmens hiba
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t4
This program will fork() child process, and the child
will overflow the buffer using strcpy().
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
parent process terminating
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t4w
This program will fork() child process, and the child
will overflow the buffer using strcpy().
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
parent process terminating
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t5
This program tries to use strcat() to overflow the buffer.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
Szegmens hiba
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t6
This program tries to use scanf() to overflow the buffer.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
Szegmens hiba
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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sunshine:/home/trey/exec/libsafe-2.0-16/exploits# echo "0" > /proc/sys/kernel/exec-shield
sunshine:/home/trey/exec/libsafe-2.0-16/exploits# cat /proc/sys/kernel/exec-shield
0
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libsafe-2.0-16 (exec-shield kikapcsolva):
---------------------------------------------------------------------
trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./canary-exploit
This program tries to use printf("%n") to overwrite the
return address on the stack.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
---------------------------------------------------------------------
---------------------------------------------------------------------
trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./exploit-non-exec-stack
This program demonstrates how a (stack) buffer overflow
can attack linux kernels with *non-executable* stacks.
This is variation on return-int-libc attack.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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---------------------------------------------------------------------
trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t1
This program tries to use strcpy() to overflow the buffer.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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---------------------------------------------------------------------
trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t1w
This program tries to use strcpy() to overflow the buffer.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t3
This program will exec() a new program. The new program will
overflow the buffer using strcpy().
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
You have new mail in /var/mail/trey
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t3w
This program will exec() a new program. The new program will
overflow the buffer using strcpy().
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t4
This program will fork() child process, and the child
will overflow the buffer using strcpy().
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
parent process terminating
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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---------------------------------------------------------------------
trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t5
This program tries to use strcat() to overflow the buffer.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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trey@sunshine:~/exec/libsafe-2.0-16/exploits$ ./t6
This program tries to use scanf() to overflow the buffer.
If you get a /bin/sh prompt, then the exploit has worked.
Press any key to continue...
sh-2.05b$ exit
exit
trey@sunshine:~/exec/libsafe-2.0-16/exploits$
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Eredmény: bekapcsolt exec-shiled-del 10-ből 8 esetben nem adtak shell-t az exploitok, "csak" segfaultoltak. Kikapcsolt exec-shield-del 10 alkalomból 10-szer adtak shellt.
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sunshine:/home/trey/exec/paxtest-0.9.1# echo "2" > /proc/sys/kernel/exec-shield
sunshine:/home/trey/exec/paxtest-0.9.1# cat /proc/sys/kernel/exec-shield
2
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paxtest-0.9.1 (exec-shield bekapcsolva):
trey@sunshine:~/exec/paxtest-0.9.1$ ./paxtest
It may take a while for the tests to complete
Test results:
Executable anonymous mapping : Killed
Executable bss : Vulnerable
Executable data : Vulnerable
Executable heap : Killed
Executable stack : Killed
Executable anonymous mapping (mprotect) : Killed
Executable bss (mprotect) : Vulnerable
Executable data (mprotect) : Vulnerable
Executable heap (mprotect) : Vulnerable
Executable shared library bss (mprotect) : Vulnerable
Executable shared library data (mprotect): Vulnerable
Executable stack (mprotect) : Vulnerable
Anonymous mapping randomisation test : 8 bits (guessed)
Heap randomisation test (ET_EXEC) : 13 bits (guessed)
Heap randomisation test (ET_DYN) : 13 bits (guessed)
Main executable randomisation (ET_EXEC) : No randomisation
Main executable randomisation (ET_DYN) : 12 bits (guessed)
Shared library randomisation test : 12 bits (guessed)
Stack randomisation test (SEGMEXEC) : 17 bits (guessed)
Stack randomisation test (PAGEEXEC) : 17 bits (guessed)
Return to function (strcpy) : Vulnerable
Return to function (memcpy) : Vulnerable
Executable shared library bss : Vulnerable
Executable shared library data : Vulnerable
Writable text segments : Vulnerable
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sunshine:/home/trey/exec/paxtest-0.9.1# echo "0" > /proc/sys/kernel/exec-shield
sunshine:/home/trey/exec/paxtest-0.9.1# cat /proc/sys/kernel/exec-shield
0
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paxtest-0.9.1 (exec-shield kikapcsolva):
trey@sunshine:~/exec/paxtest-0.9.1$ ./paxtest
It may take a while for the tests to complete
Test results:
Executable anonymous mapping : Vulnerable
Executable bss : Vulnerable
Executable data : Vulnerable
Executable heap : Vulnerable
Executable stack : Vulnerable
Executable anonymous mapping (mprotect) : Vulnerable
Executable bss (mprotect) : Vulnerable
Executable data (mprotect) : Vulnerable
Executable heap (mprotect) : Vulnerable
Executable shared library bss (mprotect) : Vulnerable
Executable shared library data (mprotect): Vulnerable
Executable stack (mprotect) : Vulnerable
Anonymous mapping randomisation test : No randomisation
Heap randomisation test (ET_EXEC) : No randomisation
Heap randomisation test (ET_DYN) : No randomisation
Main executable randomisation (ET_EXEC) : No randomisation
Main executable randomisation (ET_DYN) : No randomisation
Shared library randomisation test : No randomisation
Stack randomisation test (SEGMEXEC) : No randomisation
Stack randomisation test (PAGEEXEC) : No randomisation
Return to function (strcpy) : Vulnerable
Return to function (memcpy) : Vulnerable
Executable shared library bss : Vulnerable
Executable shared library data : Vulnerable
Writable text segments : Vulnerable
Eredmény: a bekapcsolt exec-shield 4 exploitot "killelt" ki, míg kikapcsolt állapotban az összes teszt sebezhetőséget mutatott.
A tesztek azt igazolják, hogy van értelme patchelni a kernelt az exec-shield-del, hiszen negatív következménye nincs (vagy még nem jött elő), viszont néhány exploittal szemben hatékony lehet.