Replace Signal's getFileDescriptorOwner with K-9's SafeContentResolver

build.gradle

@@ -62,6 +62,11 @@ dependencies {
         exclude group: 'com.google.android.gms'
     }
 
+    // Replacement for ContentResolver
+    // that protects against the Surreptitious Sharing attack.
+    // <https://github.com/cketti/SafeContentResolver>
+    implementation 'de.cketti.safecontentresolver:safe-content-resolver-v14:1.0.0'
+
     testImplementation 'junit:junit:4.13.1'
     testImplementation 'org.assertj:assertj-core:1.7.1'
     testImplementation 'org.mockito:mockito-core:1.9.5'

jni/Android.mk

@@ -30,8 +30,6 @@ LOCAL_CFLAGS 	:= -Werror -Wno-pointer-to-int-cast -Wno-int-to-pointer-cast -DNUL
 LOCAL_CFLAGS 	+= -Drestrict='' -D__EMX__ -DFIXED_POINT -DUSE_ALLOCA -DHAVE_LRINT -DHAVE_LRINTF -fno-math-errno
 LOCAL_CFLAGS 	+= -DANDROID_NDK -DDISABLE_IMPORTGL -fno-strict-aliasing -DAVOID_TABLES -DANDROID_TILE_BASED_DECODE -DANDROID_ARMV6_IDCT -ffast-math -D__STDC_CONSTANT_MACROS
 
-LOCAL_SRC_FILES := \
-utils/org_thoughtcrime_securesms_util_FileUtils.cpp \
-dc_wrapper.c
+LOCAL_SRC_FILES := dc_wrapper.c
 
 include $(BUILD_SHARED_LIBRARY)

src/org/thoughtcrime/securesms/ResolveMediaTask.java

@@ -13,13 +13,16 @@
 
 import java.io.File;
 import java.io.FileInputStream;
-import java.io.IOException;
+import java.io.FileNotFoundException;
 import java.io.InputStream;
 import java.lang.ref.WeakReference;
 import java.util.HashSet;
 
 import static org.thoughtcrime.securesms.util.MediaUtil.getMimeType;
 
+import de.cketti.safecontentresolver.SafeContentResolver;
+import de.cketti.safecontentresolver.SafeContentResolverCompat;
+
 public class ResolveMediaTask extends AsyncTask<Uri, Void, Uri> {
 
     private static final String TAG = ResolveMediaTask.class.getSimpleName();
@@ -51,16 +54,8 @@ protected Uri doInBackground(Uri... uris) {
                 String fileName = null;
                 Long fileSize = null;
 
-                if (hasFileScheme(uri)) {
-                    inputStream = this.openFileUri(uri);
-                    if (uri.getPath() != null) {
-                        File file = new File(uri.getPath());
-                        fileName = file.getName();
-                        fileSize = file.length();
-                    }
-                } else {
-                    inputStream = contextRef.get().getContentResolver().openInputStream(uri);
-                }
+                SafeContentResolver safeContentResolver = SafeContentResolverCompat.newInstance(contextRef.get());
+                inputStream = safeContentResolver.openInputStream(uri);
 
                 if (inputStream == null) {
                     return null;
@@ -87,7 +82,7 @@ protected Uri doInBackground(Uri... uris) {
 
                 String mimeType = getMimeType(contextRef.get(), uri);
                 return PersistentBlobProvider.getInstance().create(contextRef.get(), inputStream, mimeType, fileName, fileSize);
-            } catch (NullPointerException | IOException ioe) {
+            } catch (NullPointerException | FileNotFoundException ioe) {
                 Log.w(TAG, ioe);
                 return null;
             }
@@ -119,20 +114,6 @@ public static void cancelTasks() {
             }
         }
 
-        private InputStream openFileUri(Uri uri) throws IOException {
-            FileInputStream fin = new FileInputStream(uri.getPath());
-            int owner = FileUtils.getFileDescriptorOwner(fin.getFD());
-
-
-            if (owner == -1 || owner == Process.myUid()) {
-                fin.close();
-                throw new IOException("File owned by application");
-            }
-
-            return fin;
-        }
-
-
     private boolean hasFileScheme(Uri uri) {
         if (uri == null) {
             return false;

src/org/thoughtcrime/securesms/util/FileUtils.java

@@ -7,8 +7,6 @@
 
 public class FileUtils {
 
-  public static native int getFileDescriptorOwner(FileDescriptor fileDescriptor);
-
   public static String sanitizeFilename(String name) {
     if (TextUtils.isEmpty(name) || ".".equals(name) || "..".equals(name)) {
       return "(invalid)";