WhatsApp Blocking Encrypted Calls to All Saudi Numbers

WhatsAppSaudi.txt

Suppose I have a friend named Alice. Alice has registered to WhatsApp with a
Saudi number but resides in Europe. We chat over WhatsApp regularly. We are both
using the latest version of WhatsApp for Android (2.16.155).

However, Alice is unable to receive or initiate WhatsApp calls, even though she
is in Europe and is using European WiFi. If you can test this, I suggest you do.
Get a Saudi phone number, register to WhatsApp, and then fly to France and make
a call. You will encounter the same result even if you're on French WiFi.

WhatsApp claims that "the Saudis are blocking the initial handshake [for
encrypted calls]" and that this is why encrypted calls are dropped. However, I
insist that WhatsApp is dropping all encrypted calls made by, or received by any
WhatsApp user that registers with a Saudi number, regardless of whether they are
connectiing from Saudi Arabia, the United States via WiFi, or Tahiti.

Here is what initially led me to call this claim into question:

Reason 1: The call-prohibiting screen [0] is obtained even when Alice is in
Europe and using European WiFi. How can "Saudi firewalls" affect her phone then
and "drop the initial handshake?"

Reason 2: How could Saudi firewalls distinguish an initial encrypted call
handshake from a regular Signal protocol handshake if both handshakes are
transported over the same Noise-encrypted transport layer? Are they
man-in-the-middling the transport layer? How is this accomplished in a way that
bypasses static server authentication on behalf of WhatsApp clients?

  This explanation doesn't make sense even in that respect. Since WhatsApp
messages and encrypted phone calls are both initiated and carried over Noise
pipes, they are indistinguishable to an active attacker (such as a Saudi telco
agency.) WhatsApp knows this, and I strongly suspect they chose to block calls
in their apps so that the Saudi government wouldn't blanket-block regular
WhatsApp messages as well by dropping all Noise pipe key exchanges: the only way
the Saudi government could have stopped encrypted calls is by also dropping
encrypted WhatsApp messages, and WhatsApp is dropping calls made from/to Saudi
numbers in order to save their text messaging business.
  
  To put it simply: because of the way WhatsApp clients communicate with
WhatsApp servers, I find it impossible to believe that the Saudi government
could drop phone calls and not messages, especially at the key exchange level
(which occurs bundled atop a regular Signal session!) This makes me suspect that
the WhatsApp client itself is dropping calls if the caller/callee is registered
with a +966 number.
  
I then decided to decompile the APK binary of the latest WhatsApp release
(again, version 2.16.155). I found evidence that strongly supports my assertion
that WhatsApp is blocking encrypted calls purely based on the country code of
the registered phone number and without any attempt to even connect the call in
the first place, thereby not even giving the Saudi telcoms a chance to "drop the
initial handshake":
  1. In `res/values/public.xml`, we find the string `%s is in a country where
WhatsApp Calling is unavailable.`, which is the UI string I presented in [0].
The string is referenced with the identifier `0x7f070612`. [1]
  2. This identifier, `0x7f070612`, pops up in
`com/whatsapp/VoipNotAllowedActivity.java`, which references it in a code block
that can be triggered programatically to render [0]. [2]
  3. The function triggered in [2], `VoipNotAllowedActivity`, can be seen called
by a central call provisioning method in `com/whatsapp/App.java` [3]. This
central provisioning function first calls a series of functions which determine
whether the call recipient has registered with a phone number that is capable of
receiving encrypted phone calls.
  
I strongly urge that WhatsApp stop blocking encrypted phone calls based on phone
number and allow Saudis to communicate safely. At the very least, WhatsApp should
allow users with Saudi numbers to make calls when using data and WiFi networks
that are outside Saudi jurisdiction. However the only true solution that respects
the human rights of Saudi users is to give them encrypted calls no matter the 
consequences, instead of downgrading them to using regular Saudi phone lines, 
which are tapped by a religious dictatorship.

Addendum: WhatsApp's claim of Saudis "dropping the initial handshake"
is contradicted by their own website. [4]


References and media:
[0] http://i.imgur.com/rQu9Ocf.jpg
[1] http://i.imgur.com/bOfMIPD.png
[2] http://i.imgur.com/d6NdoGO.png
[3] http://i.imgur.com/i1R6Mu7.png
[4] https://www.whatsapp.com/faq/en/general/28030008