BlackBerry Z 10 - Storage and Access File-Exchange Authentication By-Pass [MZ-13-04]

2014-08-2600:00:00

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modzero Security Advisory: BlackBerry Z 10 - Storage and Access
File-Exchange Authentication By-Pass [MZ-13-04]

Timeline

2013-06-23: Vendor has been contacted.
2013-06-24: Vendor response.
2013-06-27: Vendor meeting and information exchange.
2013-08-20: Advisory and more details sent to the vendor.
2013-10-15 or after patch-release: Advisory will be published.
2013-12-05: Vendor requested delay of release, until a high level
of carrier uptake has been achieved.
2014-04-02: Vulnerabilities were fixed, but vendor requested delay
of release, until a higher level of carrier uptake has
been achieved.
2014-08-11: Vendor achieved sufficient customer availability for
this issue and announced release on August 12th, 2014.
2014-08-12: Release of security advisory in cooperation with
vendor.

Summary

Vendor: BlackBerry

Products known to be affected:

Blackberry Z10 model STL100-2
Software release: 10.1.0.2312
OS version: 10.1.0.2354
Build ID: 524717

Severity: Medium
Remote exploitable: Yes
CVE: CVE-2014-2388

The mobile phone offers a network service ("Storage and Access") for
adhoc file-exchange [1] between the phone and a network client [2].
To achieve these goals, the mobile device deploys a Samba fileserver,
which can be used to upload or download files to or from the
Blackberry phone. To enable fileserver access from wireless networks,
the user has to explicitly enable "Access using Wi-Fi" on the phone.
Afterwards, the Z10 asks the user to enter a password that is
required to get access to the fileserver. The fileserver
implementation or the password handling that is used on the Z10 is
affected by an authentication by-pass vulnerability: The fileserver
fails to ask for a password and allows unauthenticated users to
obtain read and write access to the offered shares. The severity is
considered medium to high, as an attacker may be able to distribute
targeted malware or access confidential data.

Details

The problem occurs, when "Sharing via Wi-Fi" has been enabled on the
Z10. The "Storage and Access" dialog of the Z10 asks the user for a
password that shall be used to access data on the fileserver. Under
certain circumstances, the fileserver fails to ask for a password and
allows access even without specifying credentials. This behaviour
does not always occur but is reproducible within at most one of ten
different tries via Wi-Fi.

The following lists describe the steps of different methods to
reproduce the issue. The fist approach let users access the
fileserver via the wireless LAN interface without using the developer
mode, which is the most common scenario. The second approach gives
access via USB cable. In this second approach, the developer mode is
activated to enable TCP/IP communication via USB. The second method
is more reliable for reproducing the effect and for tracking down the
root cause.

The root cause of the vulnerability is not known at the time of this
writing. The test was performed with an Ubuntu Linux as a network
client. References to specific Linux tools are presented for the sake
of completeness.

3.1 Method 1

Prepare the phone:

Disconnect all cables
Open Settings / "Storage and Access" and make sure "Access using
Wi-Fi" is turned off. This is not strictly necessary, but
recommended to reproduce the effect.
Power down the phone.

The process to reproduce the problem:

Boot the phone.
Enter the PIN for the SIM card.
Enter the device password.
Open Settings
Open "Network Connections". Make sure that Wi-Fi is enabled and
the phone is a client in a wireless LAN. In the test environment,
the client IP address is 10.0.0.149.
For the tests, "Mobile Hotspot" is "Not Connected" and "Internet
Tethering" is off. This setting is likely not critical.
Open "Storage and Access".
Enable "Access using Wi-Fi" on the phone. The phone will ask
for a password. Use a password, which you never used before
(for the server) to make sure, that credentials are not loaded
from the Gnome keychain.
Open Nautilus with: nautilus smb://10.0.0.149
If Nautilus fails to display a lost of shares, close Nautilus and
open it again.
Try to access a share. If the server asks for a password, disable
"Access using Wi-Fi", reboot the phone and try again.

3.2 Method 2

Prepare the phone:

Connect phone to the PC via USB cable
Open Settings / "Storage and Access" and make sure "Access using
Wi-Fi" is turned off.
Power down the phone.

The process to reproduce the problem:

Boot the phone.
Enter the PIN for the SIM card.
Enter the device password.
Open Settings
Open "Network Connections". Make sure that Wi-Fi is switched off,
"Mobile Hotspot" is "Not Connected" and "Internet Tethering" is
off.
Open "Development Mode" and enable it. The phone's IP address is
set to 169.254.0.1.
Wait for the message: "Developer mode active …".
Wait for the message: "Connected to PC …".
Open "Storage and Access", make sure "Access using Wi-Fi" is
disabled.
Open the Gnome file browser Nautilus from the command line with:
nautilus smb://169.254.0.1
If Nautilus does not show any share, close Nautilus and open it
again. If it is still empty, repeat the step.
Try to open a share: Nautilus will ask for a password. Click
cancel. Nautilus will just ask again, press Cancel, again. This
is expected behavior.
Close Nautilus
Open Nautilus, again, and leave the Nautilus window open.
Enable "Access using Wi-Fi" on the phone. The phone will ask for
a password. Use a password, which you never used before (for the
server) to make sure, that credentials are not stored in the Gnome
keychain.
Click on a share, again. The share will be opened without asking
for a password.
Disconnect share and open Nautilus again with:
nautilus smb://169.254.0.1
Open a share. Nautilus will show the contents of the share.
Create a folder and create a file.

Shutdown process:

Disconnect shares
Disable "Access using Wi-Fi" in the phone's settings.
Shut down the phone.

A video of a demonstration is available at [3].

Impact

The authentication by-pass results in read and write access to
enabled shares. Thus, sensitive data may be accessed by unauthorized
or malicious network clients or users. Since the share is also
writable, attackers are able to distribute targeted malware to
certain mobile-phone users.

Workaround

To reduce the risks in public wireless networks, disable "Access
using Wi-Fi" in the "Settings / Storage and Access" dialog.

Vendor provided bugfix.

Credits

David Gullasch ([email protected])
Max Moser ([email protected])
Martin Schobert ([email protected])

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Disclaimer

The information in the advisory is believed to be accurate at the
time of publishing based on currently available information. Use of
the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct,
indirect, or consequential loss or damage arising from use of, or
reliance on, this information.