--------------------------------------------------------------------- modzero Security Advisory: BlackBerry Z 10 - Storage and Access File-Exchange Authentication By-Pass [MZ-13-04] --------------------------------------------------------------------- --------------------------------------------------------------------- 1. 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. --------------------------------------------------------------------- 2. 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. --------------------------------------------------------------------- 3. 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: 1. Disconnect all cables 2. 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. 3. Power down the phone. The process to reproduce the problem: 1. Boot the phone. 2. Enter the PIN for the SIM card. 3. Enter the device password. 4. Open Settings 5. 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. 6. For the tests, "Mobile Hotspot" is "Not Connected" and "Internet Tethering" is off. This setting is likely not critical. 7. Open "Storage and Access". 8. 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. 9. Open Nautilus with: nautilus smb://10.0.0.149 10. If Nautilus fails to display a lost of shares, close Nautilus and open it again. 11. 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: 1. Connect phone to the PC via USB cable 2. Open Settings / "Storage and Access" and make sure "Access using Wi-Fi" is turned off. 3. Power down the phone. The process to reproduce the problem: 1. Boot the phone. 2. Enter the PIN for the SIM card. 3. Enter the device password. 4. Open Settings 5. Open "Network Connections". Make sure that Wi-Fi is switched off, "Mobile Hotspot" is "Not Connected" and "Internet Tethering" is off. 6. Open "Development Mode" and enable it. The phone's IP address is set to 169.254.0.1. 7. Wait for the message: "Developer mode active ...". 8. Wait for the message: "Connected to PC ...". 9. Open "Storage and Access", make sure "Access using Wi-Fi" is disabled. 10. Open the Gnome file browser Nautilus from the command line with: nautilus smb://169.254.0.1 11. If Nautilus does not show any share, close Nautilus and open it again. If it is still empty, repeat the step. 12. 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. 13. Close Nautilus 14. Open Nautilus, again, and leave the Nautilus window open. 15. 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. 16. Click on a share, again. The share will be opened without asking for a password. 17. Disconnect share and open Nautilus again with: nautilus smb://169.254.0.1 18. Open a share. Nautilus will show the contents of the share. 19. Create a folder and create a file. Shutdown process: 1. Disconnect shares 2. Disable "Access using Wi-Fi" in the phone's settings. 3. Shut down the phone. A video of a demonstration is available at [3]. --------------------------------------------------------------------- 4. 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. --------------------------------------------------------------------- 5. Workaround --------------------------------------------------------------------- To reduce the risks in public wireless networks, disable "Access using Wi-Fi" in the "Settings / Storage and Access" dialog. --------------------------------------------------------------------- 6. Fix --------------------------------------------------------------------- Vendor provided bugfix. --------------------------------------------------------------------- 7. Credits --------------------------------------------------------------------- * David Gullasch (dagu@modzero.ch) * Max Moser (mmo@modzero.ch) * Martin Schobert (martin@modzero.ch) --------------------------------------------------------------------- 8. About modzero --------------------------------------------------------------------- The independent Swiss company modzero AG assists clients with security analysis in the complex areas of computer technology. The focus lies on highly detailed technical analysis of concepts, software and hardware components as well as the development of individual solutions. Colleagues at modzero AG work exclusively in practical, highly technical computer-security areas and can draw on decades of experience in various platforms, system concepts, and designs. http://modzero.ch contact@modzero.ch --------------------------------------------------------------------- 9. 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. --------------------------------------------------------------------- 10. References --------------------------------------------------------------------- [1] Moving or copying media files and documents: http://docs.blackberry.com/en/smartphone_users/deliverables/47561/als1334683894417.jsp [2] How to copy files to and from a BlackBerry Z10 over a Wi-Fi network: http://helpblog.blackberry.com/2013/03/copy-z10-files-wifi/ [3] Proof-of-Concept video: http://modzero.ch/advisories/media/mz-13-04-poc.mp4