DroidLysis

DroidLysis is a pre-analysis tool for Android apps: it performs repetitive and boring tasks we'd typically do at the beginning of any reverse engineering. It disassembles the Android sample, organizes output in directories, and searches for suspicious spots in the code to look at. The output helps the reverse engineer speed up the first few steps of analysis.

DroidLysis can be used over Android packages (apk), Dalvik executables (dex), Zip files (zip), Rar files (rar) or directories of files.

Installing DroidLysis

1. Install required system packages

sudo apt-get install default-jre git python3 python3-pip unzip wget libmagic-dev libxml2-dev libxslt-dev

2. Install Android disassembly tools

• Apktool ,
• Baksmali, and optionally
• Dex2jar and

$ mkdir -p ~/softs
$ cd ~/softs
$ wget https://bitbucket.org/iBotPeaches/apktool/downloads/apktool_2.9.3.jar
$ wget https://bitbucket.org/JesusFreke/smali/downloads/baksmali-2.5.2.jar
$ wget https://github.com/pxb1988/dex2jar/releases/download/v2.4/dex-tools-v2.4.zip
$ unzip dex-tools-v2.4.zip 
$ rm -f dex-tools-v2.4.zip 

3. Get DroidLysis from the Git repository (preferred) or from pip

Install from Git in a Python virtual environment (python3 -m venv, or pyenv virtual environments etc).

$ python3 -m venv venv
$ source ./venv/bin/activate
(venv) $ pip3 install git+https://github.com/cryptax/droidlysis

Alternatively, you can install DroidLysis directly from PyPi (pip3 install droidlysis).

4. Configure conf/general.conf. In particular make sure to change /home/axelle with your appropriate directories.

[tools]
apktool = /home/axelle/softs/apktool_2.9.3.jar
baksmali = /home/axelle/softs/baksmali-2.5.2.jar
dex2jar = /home/axelle/softs/dex-tools-v2.4/d2j-dex2jar.sh
keytool = /usr/bin/keytool
...

5. Run it:

python3 ./droidlysis3.py --help

Configuration

The configuration file is ./conf/general.conf (you can switch to another file with the --config option). This is where you configure the location of various external tools (e.g. Apktool), the name of pattern files (by default ./conf/smali.conf, ./conf/wide.conf, ./conf/arm.conf, ./conf/kit.conf) and the name of the database file (only used if you specify --enable-sql)

Be sure to specify the correct paths for disassembly tools, or DroidLysis won't find them.

Usage

DroidLysis uses Python 3. To launch it and get options:

droidlysis --help

For example, test it on Signal's APK:

droidlysis --input Signal-website-universal-release-6.26.3.apk --output /tmp --config /PATH/TO/DROIDLYSIS/conf/general.conf

DroidLysis outputs:

• A summary on the console (see image above)
• The unzipped, pre-processed sample in a subdirectory of your output dir. The subdirectory is named using the sample's filename and sha256 sum. For example, if we analyze the Signal application and set --output /tmp, the analysis will be written to /tmp/Signalwebsiteuniversalrelease4.52.4.apk-f3c7d5e38df23925dd0b2fe1f44bfa12bac935a6bc8fe3a485a4436d4487a290.
• A database (by default, SQLite droidlysis.db) containing properties it noticed.

Options

Get usage with droidlysis --help

• The input can be a file or a directory of files to recursively look into. DroidLysis knows how to process Android packages, DEX, ODEX and ARM executables, ZIP, RAR. DroidLysis won't fail on other type of files (unless there is a bug...) but won't be able to understand the content.

• When processing directories of files, it is typically quite helpful to move processed samples to another location to know what has been processed. This is handled by option --movein. Also, if you are only interested in statistics, you should probably clear the output directory which contains detailed information for each sample: this is option --clearoutput. If you want to store all statistics in a SQL database, use --enable-sql (see here)

• DroidLysis's analysis does not inspect known 3rd party SDK by default, i.e. for instance it won't report any suspicious activity from these. If you want them to be inspected, use option --no-kit-exception. This usually creates many more detected properties for the sample, as SDKs (e.g. advertisment) use lots of flagged APIs (get GPS location, get IMEI, get IMSI, HTTP POST...).

Sample output directory (--output DIR)

This directory contains (when applicable):

• A readable AndroidManifest.xml
• Readable resources in res
• Libraries lib, assets assets
• Disassembled Smali code: smali (and others)
• Package meta information: META-INF
• Package contents when simply unzipped in ./unzipped
• DEX executable classes.dex (and others), and converted to jar: classes-dex2jar.jar, and unjarred in ./unjarred

The following files are generated by DroidLysis:

• autoanalysis.md: lists each pattern DroidLysis detected and where.
• report.md: same as what was printed on the console

If you do not need the sample output directory to be generated, use the option --clearoutput.

Import trackers from Exodus etc (--import-exodus)

$ python3 ./droidlysis3.py --import-exodus --verbose
Processing file: ./droidurl.pyc ...
DEBUG:droidconfig.py:Reading configuration file: './conf/./smali.conf'
DEBUG:droidconfig.py:Reading configuration file: './conf/./wide.conf'
DEBUG:droidconfig.py:Reading configuration file: './conf/./arm.conf'
DEBUG:droidconfig.py:Reading configuration file: '/home/axelle/.cache/droidlysis/./kit.conf'
DEBUG:droidproperties.py:Importing ETIP Exodus trackers from https://etip.exodus-privacy.eu.org/api/trackers/?format=json
DEBUG:connectionpool.py:Starting new HTTPS connection (1): etip.exodus-privacy.eu.org:443
DEBUG:connectionpool.py:https://etip.exodus-privacy.eu.org:443 "GET /api/trackers/?format=json HTTP/1.1" 200 None
DEBUG:droidproperties.py:Appending imported trackers to /home/axelle/.cache/droidlysis/./kit.conf

Trackers from Exodus which are not present in your initial kit.conf are appended to ~/.cache/droidlysis/kit.conf. Diff the 2 files and check what trackers you wish to add.

SQLite database{#sqlite_database}

If you want to process a directory of samples, you'll probably like to store the properties DroidLysis found in a database, to easily parse and query the findings. In that case, use the option --enable-sql. This will automatically dump all results in a database named droidlysis.db, in a table named samples. Each entry in the table is relative to a given sample. Each column is properties DroidLysis tracks.

For example, to retrieve all filename, SHA256 sum and smali properties of the database:

sqlite> select sha256, sanitized_basename, smali_properties from samples;
f3c7d5e38df23925dd0b2fe1f44bfa12bac935a6bc8fe3a485a4436d4487a290|Signalwebsiteuniversalrelease4.52.4.apk|{"send_sms": true, "receive_sms": true, "abort_broadcast": true, "call": false, "email": false, "answer_call": false, "end_call": true, "phone_number": false, "intent_chooser": true, "get_accounts": true, "contacts": false, "get_imei": true, "get_external_storage_stage": false, "get_imsi": false, "get_network_operator": false, "get_active_network_info": false, "get_line_number": true, "get_sim_country_iso": true,
...

Property patterns

What DroidLysis detects can be configured and extended in the files of the ./conf directory.

A pattern consist of:

• a tag name: example send_sms. This is to name the property. Must be unique across the .conf file.
• a pattern: this is a regexp to be matched. Ex: ;->sendTextMessage|;->sendMultipartTextMessage|SmsManager;->sendDataMessage. In the smali.conf file, this regexp is match on Smali code. In this particular case, there are 3 different ways to send SMS messages from the code: sendTextMessage, sendMultipartTextMessage and sendDataMessage.
• a description (optional): explains the importance of the property and what it means.

[send_sms]
pattern=;->sendTextMessage|;->sendMultipartTextMessage|SmsManager;->sendDataMessage
description=Sending SMS messages

Importing Exodus Privacy Trackers

Exodus Privacy maintains a list of various SDKs which are interesting to rule out in our analysis via conf/kit.conf. Add option --import_exodus to the droidlysis command line: this will parse existing trackers Exodus Privacy knows and which aren't yet in your kit.conf. Finally, it will append all new trackers to ~/.cache/droidlysis/kit.conf.

Afterwards, you may want to sort your kit.conf file:

import configparser
import collections
import os

config = configparser.ConfigParser({}, collections.OrderedDict)
config.read(os.path.expanduser('~/.cache/droidlysis/kit.conf'))
# Order all sections alphabetically
config._sections = collections.OrderedDict(sorted(config._sections.items(), key=lambda t: t[0] ))
with open('sorted.conf','w') as f:
    config.write(f)

JEB script for smali properties

This script helps you search for methods on JEB UI that contain code that matches the smali pattern and easily navigates to those functions. When you load the script and select details.md file among the droidlysis analysis files, a search box will appear. Once moved, you can easily bring up the search windows again by using recent script execution shortcut.

• JEB > File > Scripts > Script selector > script/DroidlysisSearch.py
• JEB > File > Scripts > Run last Script

Updates

• v3.4.6 - Detecting manifest feature that automatically loads APK at install
• v3.4.5 - Creating a writable user kit.conf file
• v3.4.4 - Bug fix #14
• v3.4.3 - Using configuration files
• v3.4.2 - Adding import of Exodus Privacy Trackers
• v3.4.1 - Removed dependency to Androguard
• v3.4.0 - Multidex support
• v3.3.1 - Improving detection of Base64 strings
• v3.3.0 - Dumping data to JSON
• v3.2.1 - IP address detection
• v3.2.0 - Dex2jar is optional
• v3.1.0 - Detection of Base64 strings