Malicious Threats, Vulnerabilities and Defenses in WhatsApp and Mobile Instant Messaging Platforms

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MALICIOUS THREATS, VULNERABILITIES AND
DEFENSES IN WHATSAPP AND MOBILE I.M. PLATFORMS

MALICIOUS THREATS, VULNERABILITIES AND DEFENSES IN WHATSAPP AND MOBILE I.M. PLATFORMS

WHO
WE
ARE
Jaime Sánchez
- Computer Engineer & Security Researcher

- Executive MBA, CISSP, CISA and CISM

- Speaker at Rootedcon, Nuit du Hack, BH USA
Arsenal, Defcon, NoConName, BH Sao Paulo etc.

- Twitter: @segofensiva

- http://www.seguridadofensiva.com

!
!
Pablo San Emeterio
- Computer Engineer / I+D Optenet

- Master of Science in Computer Security by UPM,
CISA and CISM

- Speaker at NoConName and CiberSeg

- Previous experience with WhatsApp :)

- Twitter: @psaneme
SHMOOCON 2014


SHHHHHHMOOCON!!
SHMOOCON 2014


SHMOOCON 2014


- Messaging volumes will be double that of SMS text messages by the end of 2013,
as consumers look for more ﬂexible, real-time messaging that circumvents billing
from their mobile carrier.

!

- Facts:

- Most IM usage is driven by teens

- There’s a smaller social graph associated with IM than Facebook

- IM lives purely in the present. Your past history with a messaging app is far less
than relevant
SHMOOCON 2014


- Some of the most common applications are:

- But, are our communications secure? Business are requited to protect
information related to their customers, vendors and their own trade secret, but
several speciﬁc issues come up with IM:

- Identity Theft

- Cyber Stalking

- Lack of Encryption

- SPAM

- Remote storage of malware

- Remote Denial of Service Attacks
SHMOOCON 2014


¿
WHAT
IS
SNAPCHAT
?
- Snapchat is a mobile app you can download to
your iPhone or Android smartphone, which you can
then use to ¿chat? with friends through photos,
videos and captions.

!

- You can sort of think of it to be like texting with
pictures or videos.

!

- One of the most unique things about Snapchat is
the self-destructing feature for photos a few
seconds after photos have been viewed.

!

- When you chat with a friend by sending them a
photo, the photo is instantly deleted seconds after it’s
been opened by the recipient.
SHMOOCON 2014


SOME
STATISTICS
STATS

SHMOOCON 2014


A
LESSON
IN
HOW
NOT
TO
DO
SECURITY
- Think those embarrassing images you sent over
Snapchat are safe? THINK AGAIN.

!
- SnapHack: an app that lets you save and re-open
Snapchat messages, without the sender ever knowing,
has now been launched.
- Hackers published 4.6 million Snapchat
usernames and phone numbers on a
website called snapchatdb.info after a
full disclosure of their API implementation.

!

- The main problem was that they ignored
a responsible repor t by secur ity
researchers
SHMOOCON 2014


SENDING
SNAPS
- Thing you will need:

- We’ll use /ph/retry instead of /ph/upload + /ph/send:
which account ?
teamsnapchat

- Let’s make some magic!! }:)
SHMOOCON 2014


SENDING
SNAPS
II
- It seems Snapchat noticed req_token & username were important ﬁelds to
check on 6th January 2014.

!

- We realized it on four days after, on 9th January:

!
!
!
!
!
!

- It seems we are unable to spoof sender username anymore.

ANY OTHER BIG IDEA??
SHMOOCON 2014


SPAM
- "We want to apologize for any unwanted Snaps and let you know our
team is working on resolving the issue”, said Snapchat in a company blog post.

!
- Is still possible to send spam to almost every user in the 4.6 million user names
and phone numbers database ?

!
- For how long is the req_token valid ?

Capture and reply the http request

We coded our own script to post images
SHMOOCON 2014


SPAM
II

SHMOOCON 2014


¿
WHAT
IS
WHATSAPP
?
It’s interesting to compare
that stat to Twitter,
which has 230 million
active monthly users,
and to Instagram, which
has 150 million on its
platform.

400
STATS

SHMOOCON 2014


Just how much is 10
billion messages?
416,666,670 messages an hour
6,944,440 messages a minute
115,704 messages a second

WhatsApp has done to SMS on mobile phones what Skype did to international
calling on landlines!
SHMOOCON 2014


SECURITY
FLAWS
- WhatsApp communications were not encrypted, and data was sent and received
in plaintext, meaning messages to easily be read if packet traces are available
(WhatsApp Sniffer)

!

- WhatsApp began using IMEI numbers and MAC addresses as passwords.

!

- Remote storage of virus, programs, html etc. on WhatsApp servers

!

- Data stored in plaintext on database

!
- An unknown hacker published a website (WhatsAppStatus.net) that made it
possible to change the status of an arbitrary WhatsApp user, as long as the phone
number was known. (To make it work, it only required a restart of the app)

SHMOOCON 2014


MORE
SECURITY
FLAWS
- On January 13, 2012, WhatsApp was pulled from the iOS App Store, and the
reason was not disclosed. The app was added back to the App Store four days later

!
- Priyanka appeared spreading on Whatsapp through a contacts file that if you add
to your contacts.

!
- WhatsApp Voyeur: allows you to view the profile picture and current "Status" of
every user without using a mobile phone or registered account

!

- No authorization required to send messages, so any user can contact you or any
custom designed bot could be created to send you spam.

!
- Serious WhatsApp flaw allows decrypting user messages

!
!
!

- This is what we know so far ...
SHMOOCON 2014


StealGenie: Spy and Dump Instant Messengers data

Android Game Steals WhatsApp Conversations

E-Mail with fake WhatsApp notiﬁcation

Fake Spy App on Smartphones
SHMOOCON 2014


THE
IDEA

SHMOOCON 2014


GOALS
- The main objective of the research is to add a new layer of security and privacy to
ensure that in the exchange of messages between members of a conversation both the
integrity and confidentiality could not be affected by an external attacker:
- Add secure encryption to the client. If
an attacker intercepts the messages, or any
governments try to intercept our messages
at WhatsApp's server , they won't find any
legible information.

- Give a certain level of anonymity to the
conversation by using fake/anonymous
accounts and intermediate communication
nodes.

- Modify the inner workings of the
application, routing all tr affic and
conversation messages to own server
(XMPP).
SHMOOCON 2014


WHY
??

SHMOOCON 2014


SURVEILLANCE
- Repor ts and documents leaked by Edward
Snowden in June 2013 indicate that PRISM is used
for monitoring communications and other stored
information.

!

- The data that the NSA is supposedly able to get by
PRISM includes email, video, voice chat, photos, IP
addresses, login notifications, file transfer and details
about social networking profiles.

!
- Internet companies such as Microsoft, Google,
Yahoo, Dropbox, Apple and Facebook are inside
the program.

!

- The objectives of the PRISM program are those
citizens living outside the United States, but U.S.
citizens are included too.
SHMOOCON 2014


SMS
SURVEILLANCE
- The National Security Agency has collected almost 200 million text messages a day
from across the globe, using them to extract data including location, contact networks
and credit card details, according to top-secret documents.
- On average, each day the NSA was able to extract:

• More than 5 million missed-call alerts, for use
in contact-chaining analysis

• Details of 1.6 million border crossings a day,
from network roaming alerts

• More than 110,000 names, from electronic
business cards

• Over 800,000 ﬁnancial transactions

¿ Could IM protocols be the next target ?
SHMOOCON 2014


INSIDE
THE
WORLD
OF

WHATSAPP

SHMOOCON 2014

!

!

!


57:41
01:02

=>
=>

LOGIN

WA
PROTOCOL VERSION 1.2

f8:05:01:c8:ab:a5:fc:12:69:50:68:6f:6e:65:2d:32:2e:31:30:2e:32:2d:35:32:32:32:00:00
0x01 => stream:stream 0xc8 => to 0xab: s.whatsapp.net 0xa5 => resource
0xfc => String 12caracteres => iPhone-2.10.2-5222
<stream:stream to=”s.whatsapp.net” resource=”iPhone-2.10.2-5222” />
f8:02:bb
=>
0xbb => stream:features
f8:04
f8:03:70:31:ca
=>
0x70 => message_acks
f8:01:9c
=>
0x9c => receipt_acks
f8:03:e4:cb:0c
=>
0xe4 => w:profile:picture
f8:03:b9:7c:ca
=>
0xb9 => status
<stream:features>
<message_acks enable=TRUE />
<receipt_acks />
<w:profile:picture type=ALL />
<status notification=TRUE />
</stream:features>

0x31 => enable

0xca => TRUE

0xcb => type
0x7c => notification

0x0c => all
0xca => TRUE

f8:08:10:6d:ec:da:fc:0b:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:X:e8:cf
0x10 => auth
0x6d => mechanism
0xec => WAUTH-1
user => 34XXXXXXXXX 0x31 => enable
0xe8 => xmlns
0xcf => urn:ietf:params:xml:ns:xmpp-sasl
<auth mechanism=”WAUTH-1” user=”XXXXXXXXXXX”
xmlns=”urn:ietf:params:xml:ns:xmpp-sasl” />
SHMOOCON 2014


LOGGING
IN
ON
A
NEW
DEVICE
1) WhatsApp will send the user’s phone number to servers, through HTTPS,
requesting an authentication code

2) The mobile phone receives, through text message, the authentication code

3) This authentication code is sent and compared, and if matches, WhatsApp
obtains the password

!

- To log in, the client uses a custom SASL mechanism, called WAUTH-1. First, the
client sends:

!

<auth xmlns="urn:ietf:params:xml:ns:xmpp-sasl" user="XXXXXXXXXXXX"
mechanism="WAUTH-1" />

- Server will answer with a challenge:

!

<challenge xmlns="urn:ietf:params:xml:ns:xmpp-sasl">YYYYYYYYYYYYYYYYYYYY
</challenge>

- To respond the challenge, the client will generate a key using PKBDF2 with user’s
password, challenge as salt and SHA1 as hash function. Only 20 bytes from result will
be used as key <phone number> || <20 bytes> || UNIX timestamp:

<response xmlns="urn:ietf:params:xml:ns:xmpp-sasl">ZZZZZZZZZZZZZ</response>

SHMOOCON 2014


ARE
MY
MESSAGES
SECURE
?

- RC4, the most widely used software stream cipher and is used in popular protocols
such as Transport Layer Security (TLS) and WEP, was designed by Ron Rivest of RSA
Security in 1987

!

- RC4 has two stages - a KSA, that initializes the state table to be a "random"
permutation based on the key, and the PRGA, which actually returns a random byte.

¿ Where is the problem ?
SHMOOCON 2014


EVERY
TIME
ALICE
ENCRYPTS
A
MESSAGE ,
GOD
KILLS
A
KITTEN
...
Suppose Alice wants to send encryptions of m1 and m2 to Bob
over a public channel. Alice and Bob have a shared key k; however,
both messages are the same length as the key k. Since Alice is
extraordinary lazy (and doesn't know about stream ciphers), she
decides to just reuse the key.

!

Alice sends ciphertexts c1 = m1 ⊕ k and c2 = m2 ⊕ k to Bob
through a public channel. Unfortunately, Eve intercepts both of
these ciphertexts and calculates c1 ⊕ c2= m1 ⊕ m2.

c1 = m1 ⊕ k
c2 = m2 ⊕ k

m1 = c1 ⊕ k
m2 = c2 ⊕ k

REUSED KEY ATTACK
c1 ⊕ c2 = m1 ⊕ m2

SHMOOCON 2014


ATTACKING
WHATSAPP’S
ENCRYPTION
- From here, the task becomes separating the two plaintexts from one another
(plaintext attack or Crib-Dragging), following the steps bellow:

1) Guess a word that might appear in one of the messages

2) Encode the word from step 1 to a hex string

3) XOR the two cipher-text messages

4) XOR the hex string from step 2 at each position of the XOR of the two
cipher-texts (from step 3)

5) When the result from step 4 is readable text, we guess the English word and
expand our crib search.

6) If the result is not readable text, we try an XOR of the crib word at the next
position.

!

- To do this, we have to do a little guessing about the

plaintexts themselves.

!

- The idea is to use a Frecuency Analysis based on

the original language used in the plaintext.
SHMOOCON 2014


OTHER 
ATTACKS
?

SHMOOCON 2014


ATTACKING
WHATSAPP’S
ENCRYPTION
- From here, the task becomes separating the two plaintexts from one another
(plaintext attack or Crib-Dragging), following the steps bellow:

1) Guess a word that might appear in one of the messages

2) Encode the word from step 1 to a hex string

3) XOR the two cipher-text messages

4) XOR the hex string from step 2 at each position of the XOR of the two
cipher-texts (from step 3)

5) When the result from step 4 is readable text, we guess the English word and
expand our crib search.

6) If the result is not readable text, we try an XOR of the crib word at the next
position.

!

ADDITIONAL

ENCRYPTION

- To do this, we have to do a little guessing about the

plaintexts themselves.

!

- The idea is to use a Frecuency Analysis based on

the original language used in the plaintext.
SHMOOCON 2014


INTERCEPT
MESSAGES
- We have veriﬁed that the encryption used to
protect the information and privacy of our
conversations is easy to break.

!

- ¿What can we do? We will intercept WhatsApp's
message before you leaving the mobile phone. We'll
decipher the original message with our key and we
will apply a new cipher and then encrypt it with the
original algorithm and key, not breaking the
application.

!

- From now on, we’ll be working this way:
REAL-TIME
MODIFICATION

SHMOOCON 2014


CHALLENGE
AND
iOS
- In iOS version we’ll use a little trick to get the challenge. Instead of exchanging it during the login, WhatsApp sends the challenge for the next session while connected.

!

- We’ll ﬂip some random bytes, forcing WhatsApp to negotiate it again:

- The result for the log in of the second mobile is the same:

SHMOOCON 2014


SENDING
MESSAGES
- The message is sent from the client. Our program detects it, and using the RC4 session key used
by WhatsApp, decrypts the message and extracts text. Once the text is clear, encrypts it with our
algorithm and key, and re-wrap it in the original format with RC4 encryption it again, not breaking
the operation of WhatsApp:

- You can see how our program has decoded the original message: Bello

!

- HMAC is deleted in the decoded message and we calculate it again before sending. Finally, the
message will leave our mobile phone. We can see that the new message is different from the
original because is has a layer encryption implemented by us:
HMAC

SHMOOCON 2014


RECEIVING
MESSAGES
- In the screenshot you can see how we received an normal WhatsApp message, but it’s really
special. When we use the RC4 key to decrypt the text inside, we find is completely unreadable.

- Using the same private key and algorithm, our program will decrypt the message text and
reassemble the original text, so WhatsApp will be able to process it.

!
!

- The final message can be read as usually by the user, and it’s the same as the first one:

SHMOOCON 2014


WITHOUT
PRIVATE
KEY

SHMOOCON 2014


ANONYMITY
SHMOOCON 2014


ANONYMITY
- Remove identity identifying details of our original account

!

- We’ll use several WhatsApp hops using Yowsup

!

- Yowsup is a python library that allows you to do all the previous in your own app. It
allows you to login and use the Whatsapp service and provides you with all
capabilities of an ofﬁcial client,.

!

- Protects ourselves from metadata extraction

VIRTUAL NUMBERS

SHMOOCON 2014


EXTERNAL

XMPP
SERVER
SHMOOCON 2014


HIDING
OUR
MESSAGES
- The above method allows us to encrypt our messages,
so other attackers capable of intercepting our trafﬁc will
not be able to get the contents of messages.

!

- But, ¿ what if we want the trafﬁc to directly bypass
the WhatsApp's server ?

EXTERNAL XMPP SERVER

SHMOOCON 2014


USING
AN
EXTERNAL
XMPP
SERVER
- We analyze the outgoing message and decrypt it using the RC4 key.

!

- Then, we extract the original text and send it to our external XMPP server:

<destination number>¿<message_id>¿<original text>

- The program will replace every character in the original text with our wildcard character, so the
original message will never pass through WhatsApp's servers (this step is necessary or destination
will reject our messages)

!

- Recipient receives our message full of wildcard characters, querys our XMPP server and
replaces the wildcard characters with the original text.
SHMOOCON 2014


WHATSAPP
CAN
ONLY
SEE
...

SHMOOCON 2014


THANK

!

YOU
SHMOOCON 2014

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