android: fix crash with Android <12 and go 1.23

Due to golang/go#70508, the BitBoxApp crashes
on versions of Android older than 12 if upgrading to Go 1.23.

Therefore we are applying the workaround described at
golang/go#70508 (comment) which
is to intercept and ignore SIGSYS signals.

Author: bznein

.gitignore

@@ -7,6 +7,7 @@
 
 .DS_Store
 .idea
+.cxx/
 
 
 ### Vim ###

frontends/android/BitBoxApp/app/build.gradle

@@ -10,6 +10,11 @@ android {
         versionCode 59
         versionName "android-4.47.0"
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+        externalNativeBuild {
+            cmake {
+                cppFlags '-std=c++11'
+            }
+        }
     }
     buildTypes {
         release {
@@ -23,6 +28,12 @@ android {
         }
     }
     namespace 'ch.shiftcrypto.bitboxapp'
+    externalNativeBuild {
+        cmake {
+            path file('src/main/cpp/CMakeLists.txt')
+            version '3.31.6'
+        }
+    }
 }
 
 dependencies {

frontends/android/BitBoxApp/app/src/main/cpp/CMakeLists.txt

@@ -0,0 +1,23 @@
+cmake_minimum_required(VERSION 3.16)
+
+project(signal_handler)
+
+add_library( # Specifies the name of the library.
+             signal_handler
+
+             # Sets the library as a shared library.
+             SHARED
+
+             # Provides a relative path to your source file(s).
+             signal_handler.c
+)
+
+find_library(
+        log-lib
+        log
+)
+
+target_link_libraries(
+        signal_handler
+        ${log-lib}
+)

frontends/android/BitBoxApp/app/src/main/cpp/signal_handler.c

@@ -0,0 +1,28 @@
+// signal_handler.c
+#include <jni.h>
+#include <signal.h>
+#include <android/log.h>
+
+#define LOG_TAG "SignalHandler"
+#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
+
+void sigsys_handler(int signum, siginfo_t *info, void *context) {
+    LOGI("SIGSYS signal received and ignored.");
+}
+
+void setup_sigsys_handler() {
+    struct sigaction sa;
+    sa.sa_flags = SA_SIGINFO;
+    sa.sa_sigaction = sigsys_handler;
+    sigemptyset(&sa.sa_mask);
+    if (sigaction(SIGSYS, &sa, NULL) == -1) {
+        LOGI("Failed to set up SIGSYS handler");
+    } else {
+        LOGI("SIGSYS handler set up successfully");
+    }
+
+}
+
+JNIEXPORT void JNICALL Java_ch_shiftcrypto_bitboxapp_MainActivity_initsignalhandler(JNIEnv *env, jobject thisObj) {
+  setup_sigsys_handler();
+}

frontends/android/BitBoxApp/app/src/main/java/ch/shiftcrypto/bitboxapp/MainActivity.java

@@ -60,6 +60,10 @@
 import mobileserver.Mobileserver;
 
 public class MainActivity extends AppCompatActivity {
+    static {
+        System.loadLibrary("signal_handler");
+    }
+    public native void initsignalhandler();
     private final int PERMISSIONS_REQUEST_CAMERA_QRCODE = 0;
     private static final String ACTION_USB_PERMISSION = "ch.shiftcrypto.bitboxapp.USB_PERMISSION";
     // The WebView is configured with this as the base URL. The purpose is so that requests made
@@ -123,13 +127,12 @@ public void onReceive(Context context, Intent intent) {
         @Override
         public void onReceive(Context context, Intent intent) {
             Mobileserver.usingMobileDataChanged();
-         }
+        }
     };
 
 
-
     @Override
-    public void onConfigurationChanged(Configuration newConfig){
+    public void onConfigurationChanged(Configuration newConfig) {
         int currentNightMode = newConfig.uiMode & Configuration.UI_MODE_NIGHT_MASK;
         switch (currentNightMode) {
             case Configuration.UI_MODE_NIGHT_NO:
@@ -172,6 +175,8 @@ protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         Util.log("lifecycle: onCreate");
 
+        initsignalhandler();
+
         getSupportActionBar().hide(); // hide title bar with app name.
         onConfigurationChanged(getResources().getConfiguration());
         setContentView(R.layout.activity_main);

scripts/docker_install.sh

@@ -101,4 +101,4 @@ gem install --no-document fpm
 # Needed for Android.
 apt-get install -y --no-install-recommends openjdk-17-jdk
 # Keep versions in sync with build.gradle and frontends/android/Makefile.
-/opt/android-sdk/cmdline-tools/tools/bin/sdkmanager "ndk;21.2.6472646" "platforms;android-34" "build-tools;34.0.0" "platform-tools"
+/opt/android-sdk/cmdline-tools/tools/bin/sdkmanager "ndk;21.2.6472646" "platforms;android-34" "build-tools;34.0.0" "platform-tools" "cmake;3.31.6"