QT + OpenSSL + Android

Decision:

1a) correct way: compile openssl libraries for android (use 1.0.2+, don't use 1.1. * - at least for Qt 5.9.2)

or

1b) quick and dirty way: GET THEM FROM any existing APK application (warning: deprecated libs ==> security risk) if you need a quick and dirty solution. Search for libssl.so and libcrypto.so inside the arm APK directory.

THEN

2a) open Qt Creator, Projects -> [project] -> Build and Run -> Android for armeabi-> v7a -> Build -> Build Android APK -> Android -> Additional Libraries -> Add .. (add libssl.so, libcrypto.so is there)

or

2b) in make. make add the following:

ANDROID_PACKAGE_SOURCE_DIR = $$PWD/android
contains(ANDROID_TARGET_ARCH,armeabi-v7a) {
     ANDROID_EXTRA_LIBS = \
        $$PWD/android/libs/arm/libcrypto.so \
        $$PWD/android/libs/arm/libssl.so
}

      

        
        
        
      

    

($$ PWD / android / .. this is your path inside your project where you put these libraries). ANDROID_PACKAGE_SOURCE_DIR looks like optional for this case.

THEN

3) Add them to load in AndroidManifest (valid at least for Qt 5.9.2): carefully add them here to the existing main activity metadata and out-of-process services, if any.

        <meta-data android:name="android.app.load_local_libs" android:value="-- %%INSERT_LOCAL_LIBS%% --:lib/libssl.so:lib/libcrypto.so"/>

      

        
        
        
      

    

"lib" MUST be "lib" here, this refers to the layout of the device directory, not your project structure.

THEN

4) build your apk. Check that your libraries are in the correct location:

$ jar tvf ./android-build/build/outputs/apk/android-build-debug.apk| grep libssl
344388 Tue Apr 11 12:35:36 EEST 2017 lib/armeabi-v7a/libssl.so

      

        
        
        
      

    

I put this instruction here because I spent too much time looking for an answer and everything without ANDROID_EXTRA_LIBS did not work for me.

N.B.

Why is this so problematic? As androids up to 6.0 may contain their own libssl / libcrypto, and linking via "-l" will add an autoload entry to your main binary (not Qt-managed), and system libraries may be of the wrong version or load SILENTLY INSTEAD OF YOUR shipped binaries thus masking the bug with Android 7. Android 7 definitely does not contain libssl, and "-l" will fail and characters will not be resolved at runtime.

By not using "-l" and using Qt "android.app.load_local_libs" instead, you force QtLoader to use your lib version. Remember openssl 1.0.2 works with the default android Qt installation and 1.1. * Will NOT work due to different characters. (SSL_init_library - 1.0.2, OPENSSL_init_library - 1.1. *)

Interestingly, due to these complexities, the "1b" "method might not work. The APK you selected might contain libssl.so, but its author built it incorrectly and loaded it incorrectly, so its libssl.so might be the wrong version of the generic a library that generally doesn't work on android, but the author used -l and never loaded a native lib (the system was used instead) and never knew his library would not load on Android.