Signing Android apps

All Android applications have to be digitally signed before they are made available to the public to confirm their author and guarantee that the code has not been altered or corrupted since it was signed. There are several ways to set up code signing for Android apps.

Signing Android apps using Gradle

This example shows how to set up code signing using Gradle.

Set your signing configuration in build.gradle as follows:

...
  android {
      ...
      defaultConfig { ... }

      signingConfigs {
          release {
              if (System.getenv()["CI"]) { // CI=true is exported by Codemagic
                  storeFile file(System.getenv()["FCI_KEYSTORE_PATH"])
                  storePassword System.getenv()["FCI_KEYSTORE_PASSWORD"]
                  keyAlias System.getenv()["FCI_KEY_ALIAS"]
                  keyPassword System.getenv()["FCI_KEY_PASSWORD"]
              } else {
                  storeFile file("/path/to/local/myreleasekey.keystore")
                  storePassword "password"
                  keyAlias "MyReleaseKey"
                  keyPassword "password"
              }
          }
      }

      buildTypes {
          release {
              ...
              signingConfig signingConfigs.release
          }
      }
  }
  ...

Add your keystore and keystore details in the environment section of the configuration file. Encrypt your keystore file, keystore password (if keystore is password-protected), key alias and key alias password (if key alias is password-protected) and set the encrypted values to the following environment variables. Note that when encrypting files via UI, they will be base64 encoded and would have to be decoded during the build.

environment:
  FCI_KEYSTORE_PATH: /tmp/keystore.keystore
  FCI_KEYSTORE: Encrypted(...)
  FCI_KEYSTORE_PASSWORD: Encrypted(...)
  FCI_KEY_ALIAS: Encrypted(...)
  FCI_KEY_PASSWORD: Encrypted(...)

In the scripts section of the configuration file, you will need to decode the keystore file and add it before the build command. You can choose any path to your keystore file. For example:

scripts:
  - name: Build Android
    script: |
      echo $FCI_KEYSTORE | base64 --decode > $FCI_KEYSTORE_PATH
      cd android && ./gradlew assembleRelease

Signing Android apps using key.properties

The following templates show code signing using key.properties.

Set up default debug key.properties

- name: Set up debug key.properties
  script: |
    keytool -genkeypair \
      -alias androiddebugkey \
      -keypass android \
      -keystore ~/.android/debug.keystore \
      -storepass android \
      -dname 'CN=Android Debug,O=Android,C=US' \
      -keyalg 'RSA' \
      -keysize 2048 \
      -validity 10000

Set up code signing with user-specified keys

In order to do code signing encrypt your keystore file, keystore password (if keystore is password protected), key alias and key alias password (if key alias is password protected) and set the encrypted values to the following environment variables:

FCI_KEYSTORE_PATH: /tmp/keystore.keystore
FCI_KEYSTORE: Encrypted(...)
FCI_KEYSTORE_PASSWORD: Encrypted(...)
FCI_KEY_ALIAS: Encrypted(...)
FCI_KEY_PASSWORD: Encrypted(...)

Use the following script:

- name: Set up key.properties
  script: |
    echo $FCI_KEYSTORE | base64 --decode > $FCI_KEYSTORE_PATH
    cat >> "$FCI_BUILD_DIR/project_directory/android/key.properties" <<EOF
    storePassword=$FCI_KEYSTORE_PASSWORD
    keyPassword=$FCI_KEY_PASSWORD
    keyAlias=$FCI_KEY_ALIAS
    storeFile=$FCI_KEYSTORE_PATH
    EOF