Activity 3
![](images/ttu/images/pic3.jpg)
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
- 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
(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.)
↠1.6★ ★ ★ Self-Assessment ★ ★ ★
Please complete the following self-assessment over Activity 3
Start Assessment↠1.7 Activity 3 - Feedback πππΆππ
Please complete the following survey questions over Activity 3
Start Survey Questions