Activity 3


                                                                                  Estimated Time: 15 Minutes

1.1 Objective

  • In this Activity 3, a new APK file is built with modified code and signed with key store file.

1.2 Description

With malicious code injected into one of the files of APK in Activity 2, we will re-build the APK file now and sign it with same java key store file generated during Activity1.


1.3 Prerequisites

For this Activity you need to download, install jdk and set environment variables 'Path' & 'JAVA_HOME' in windows. This is required for running 'jarsigner' command to build the modified APK file. You can watch below YouTube video for reference.
   How to Install Java JDK 18 on Windows 10


1.4 Artifacts

Click below link to download modified APK file
login.apk


1.5 Instructions

  • Step 1: After updating code of "RestClient.smali" file in Activity 2, we will re-build app-release.apk file in this Activity.

  • Step 2: Open command prompt and go to path where you have placed files "app-release.apk" & "apktool_2.0.0rc3.jar" initially.

  • Step 3: Execute below command to build app-release folder and create new "app-release.apk" file.
  •    java -jar apktool_2.0.0rc3.jar b app-release

  • Step 4: Observe that a new file "app-release.apk" is created under sub-folder /app-release/dist/

  • Step 5: Since the code has changed, old signature is invalid. So, we need to sign it again.

  • Step 6: Open command prompt and execute below command.
  •    jarsigner -verbose p9cert.jks app-release/dist/app-release.apk proj9key
       (Note: If you are getting "jarsigner not found" error, it means Java configurations is not set correctly in your windows system.
       Please refer section "Activity 3: Pre-Requisites" for setting environment variables correctly.)

  • Step 7: To save time, modified APK file with name as "login.apk" is provided under "Activity 3: Artifacts" section. Kindly use it for subsequent Activities


1.6★ ★ ★ Self-Assessment ★ ★ ★

Please complete the following self-assessment over Activity 3

Start Assessment

1.7 Activity 3 - Feedback πŸ˜πŸ˜πŸ˜ΆπŸ™πŸ˜ž

Please complete the following survey questions over Activity 3

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