Its-Just-Nans

Extract the APK from your device

• With APK Extractor app

  • install an APK Extractor app from the Store
  • launch the app
  • select the app you want to extract
  • the app will create an .apk file

• With adb

  https://developer.android.com/tools/adb

  • install adb on your computer
  • get the full app name with adb shell pm list packages | grep APP_NAME
  • get the apk path with adb shell pm path FULL_APP_NAME
  • pull the apk with adb pull APK_PATH

apktools

https://github.com/iBotPeaches/Apktool - https://apktool.org/docs/install

apktool can extract the .apk file into a directory with the resources and the classes

java -jar apktool.jar d APP_NAME.apk

dex2jar

https://github.com/pxb1988/dex2jar - https://github.com/pxb1988/dex2jar/releases

dex2jar can transform the .apk into a .jar file viewable by jd-gui

# download the latest release
# extract the zip file
d2j-dex2jar.sh APP_NAME.apk

jd-gui

https://github.com/java-decompiler/jd-gui - https://github.com/java-decompiler/jd-gui/releases

jd-gui can view the .jar file generated by dex2jar

java -jar jd-gui.jar APP_NAME-dex2jar.jar

jadx

https://github.com/skylot/jadx - https://github.com/skylot/jadx/releases

jadx can decompile the .apk file and view the source code

jadx -d out_folder APP_NAME.apk
jadx-gui # open the APK inside

Get signatures of the APK

apksigner verify --print-certs example.apk

Android keystore and keytool

The keystore is often a PKCS12 keystore type

# list the keys
keytool -keystore ~/path/to/keystore -list

# export the certificate
keytool -keystore ~/path/to/keystore -exportcert -alias key_alias -file exported_certificate.der

# convert JKS to PKCS12
keytool \
    -importkeystore \
    -srckeystore ~/path/to/keystore \
    -destkeystore PRIVATE_KEYSTORE.p12 \
    -srcstoretype JKS \
    -deststoretype PKCS12 \
    -srcstorepass $STORE \
    -deststorepass key_out \
    -srcalias key_alias \
    -destalias key_alias \
    -srckeypass $KEY \
    -destkeypass key_out \
    -noprompt

# export private key
openssl pkcs12 -in PRIVATE_KEYSTORE.p12 -nodes -nocerts -out private.key
# check the private.key file