PULLING THE APK FROM THE DEVICE 6 • Often the APKs are downloaded from Google Play on the device, how can we extract them? Some solutions: 1. adb backup -apk com.mypackage (Works on Android 4.0 and newer)
2. Use a backup application (ASTRO File manager, Titanium Backup…)
3. adb shell , cd /data/app/, find your apk, then you can pull it with adb pull /data/app/ mypackage.apk (requires a adb root shell on the device)
FREE TOOLS • apktool and smali/baksmali It will provide us a disassembled representation of the Dalvik bytecode, so sort “low level”, with registers, but very understandable because of bytecode metadata. Very useful to disable tampering protections, the code can be modified and the application can be recompiled and resigned. 7
TAMPERING DETECTION 18 • Check at runtime if the application has been modified in any way or if the signature is changed. • It can be done with the PackageManager class, retrieving the Signature[] array of your app and comparing with known values. If an attacker resigned the app, the signing key will be different.
• Do the checks in multiple code points and use obfuscation, to avoid that it can be easily bypassed.
• If your app ships only through Google Play, check with the APIs that it has been installed from Google Play and not from Unknown Sources.
• If something is wrong, close the application without leaking informations where the protection code is, to make attacker’s life harder.
LOGGING • Remove Logcat logging from your production builds. • It can be done with few lines in Proguard and Dexguard, they remove all the calls to Log.d, Log.e etc in the build process
• It’s very easy for third party malware or an attacker to access the Logs on Android. 20
EXTERNAL STORAGE • Try to avoid storing your data in the shared storage, almost any application can read it. (In 4.4 a small protection at permission level was added android.permission.READ_EXTERNAL _STORAGE, usually users does not check permissions too much anyway… Don’t rely on this.) 21 My Personal Data stored in a Evernote Note,
PRIVATE APP FOLDER • Encrypt your preferences/files • With root access they can be modified, avoid store sensitive data at all if possible
• With a backup, they can be retrieved from the device usually
• The private folder can be found on the device at path /data/data/yourpackage 22 That’s right.. It’s my User and my 36 character Password in PLAIN TEXT CASE STUDY
SECURE NETWORK COMMUNICATIONS • It’s your responsibility to protect data in transit! • Don’t transmit sensitive information without SSL/TLS • Implement if possibile Certificate Pinning, in this way your communications will be more resistant to MITM attacks, for example if a malicious certificate is pushed into the device, or if an attacker can impersonate your web service with a trusted certificate. 26
THE ANDROID MANIFEST 27 • Avoid the flag android:debuggable=true in production, an attacker can attach with a debugger and execute arbitrary code in your app.
• Double check your exported components. Export a component to other processes only if it’s strictly necessary and at least protect the component with a permission. Android has some permissive defaults, some components are exported even if they are not declared exported=true, check the documentation.
• If you export a content provider or another component that grants access to data and accepts untrusted output, be careful on the input to avoid sql injections and path traversal attacks.
RAM MEMORY ATTACKS • An easiest way to get an incomplete (VM only) chunk of live memory from our application is to use the “Dump HPROF” functionality in the monitor tool, with a debuggable application or a device with the flag ro.debuggable=1 30
RUNTIME MANIPULATION Why modify the code of the application recompiling it when we can modify the code at runtime, without alerting the basic tampering detection? 32
RUNTIME MANIPULATION 33 We can change the behaviour of the applications and the system without touching any APK and we can enable/disable plugins with ease.
! We must have a rooted phone and install a framework that will modify some low level components of the Android OS, to make our life easier.
1PASSWORD READER • Password wallet application for Android, a companion application of the Mac/Windows client, to be able to share our passwords between our PC and the mobile device, leveraging Dropbox or the Shared Storage. 51 CASE STUDY
BE CAREFUL WITH BROADCASTED INTENTS 52 Vulnerable unprotected Broadcast Receiver to make the app timeout, with a Broadcasted Intent (Dangerous!) CASE STUDY
RESULTS 54 The Malware catch the Broadcast Intent before of the wallet. It suppress it, so the Wallet never get the Intent and never go to timeout its session.
! What we learned: The system often is not trusted when doing IPC with Intents, and in any case we must protect the exposed parts of our application, auditing and remediating. CASE STUDY
1PASSWORD: WHY SHARED STORAGE AND DROPBOX? • This choices are forced for technical limitation in the sharing process between the PC and the device.
• Without root permissions, the user can only write in the shared folder, or the application can use third party services, such file sharing API by Dropbox, to share the wallet file. 55 CASE STUDY
FIRST LOOK • The 1Password wallet is totally unobfuscated, so an attacker can easily understand the logic of the application and the weak points.
• First weak spot: LOGS, the application disabled in productions the logging of the user credentials and other internal information to the Logcat, but the logs are only disabled, the code that logs at the critical points (even the user password) it’s in there. 56 CASE STUDY
marcograss
hirokunimaeta
.jpg){kind=avatar}
gtnao
konpay
pocke
ancaghenade
tmokmss
mukky620
yumakann
shinmiy
satoshi7190
jmatsu
numeroanddev
chrislema
danielanewman
jmmastey
tammielis
brianwarren
destraynor
rmw
caitiem20
morganepeng
searls
kastner
trallard