module

Linux Polkit pkexec helper PTRACE_TRACEME local root exploit

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Disclosed
2019-07-04
Created
2019-10-23

Description

This module exploits an issue in ptrace_link in kernel/ptrace.c before Linux
kernel 5.1.17. This issue can be exploited from a Linux desktop terminal, but
not over an SSH session, as it requires execution from within the context of
a user with an active Polkit agent.
In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles
the recording of the credentials of a process that wants to create a ptrace
relationship, which allows local users to obtain root access by leveraging
certain scenarios with a parent-child process relationship, where a parent drops
privileges and calls execve (potentially allowing control by an attacker). One
contributing factor is an object lifetime issue (which can also cause a panic).
Another contributing factor is incorrect marking of a ptrace relationship as
privileged, which is exploitable through (for example) Polkit's pkexec helper
with PTRACE_TRACEME.

Authors

Jann Horn
bcoles bcoles@gmail.com
timwr

Platform

Linux

Architectures

x64

References

Module Options

To display the available options, load the module within the Metasploit console and run the commands ‘show options’ or ‘show advanced’:


    msf > use exploit/linux/local/ptrace_traceme_pkexec_helper
    msf exploit(ptrace_traceme_pkexec_helper) > show targets
        ...targets...
    msf exploit(ptrace_traceme_pkexec_helper) > set TARGET < target-id >
    msf exploit(ptrace_traceme_pkexec_helper) > show options
        ...show and set options...
    msf exploit(ptrace_traceme_pkexec_helper) > exploit
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