Fix path traversal vulnerabilities in MediaProvider

Canonicalize filepath provided by the caller when hanling SCAN_FILE_CALL
method call in MediaProvider.
Additionally, make sure to check access permission in SCAN_FILE_CALL
(using enforceCallingPermissionInternal()).

Preemptively canonicalize Files provided as an arguments to the public
API methods in ModernMediaScanner (scanFile(), scanDirectory() and
onDirectoryDirty()) to prevent path traversal attacks.

Bug: 262244882
Test: atest MediaProviderTests
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:4c867764086b90a27e745ec82e383d63fb9b6232)
Merged-In: I61e77d69ae857984b819fa0ea27bec5c26a34842
Change-Id: I61e77d69ae857984b819fa0ea27bec5c26a34842

3 files changed, 90 insertions, 37 deletions

diff --git a/src/com/android/providers/media/MediaProvider.java b/src/com/android/providers/media/MediaProvider.java
index e96030627..7aa43dbcb 100644
--- a/src/com/android/providers/media/MediaProvider.java
+++ b/src/com/android/providers/media/MediaProvider.java
@@ -6418,38 +6418,51 @@ public class MediaProvider extends ContentProvider {
                 }
                 return null;
             }
-            case MediaStore.SCAN_FILE_CALL:
+            case MediaStore.SCAN_FILE_CALL: {
+                final LocalCallingIdentity token = clearLocalCallingIdentity();
+                final CallingIdentity providerToken = clearCallingIdentity();
+
+                final String filePath = arg;
+                final Uri uri;
+                try {
+                    File file;
+                    try {
+                        file = FileUtils.getCanonicalFile(filePath);
+                    } catch (IOException e) {
+                        file = null;
+                    }
+
+                    uri = file != null ? scanFile(file, REASON_DEMAND) : null;
+                } finally {
+                    restoreCallingIdentity(providerToken);
+                    restoreLocalCallingIdentity(token);
+                }
+
+                // TODO(b/262244882): maybe enforceCallingPermissionInternal(uri, ...)
+
+                final Bundle res = new Bundle();
+                res.putParcelable(Intent.EXTRA_STREAM, uri);
+                return res;
+            }
             case MediaStore.SCAN_VOLUME_CALL: {
                 final int userId = uidToUserId(Binder.getCallingUid());
                 final LocalCallingIdentity token = clearLocalCallingIdentity();
                 final CallingIdentity providerToken = clearCallingIdentity();
+
+                final String volumeName = arg;
                 try {
-                    final Bundle res = new Bundle();
-                    switch (method) {
-                        case MediaStore.SCAN_FILE_CALL: {
-                            final File file = new File(arg);
-                            res.putParcelable(Intent.EXTRA_STREAM, scanFile(file, REASON_DEMAND));
-                            break;
-                        }
-                        case MediaStore.SCAN_VOLUME_CALL: {
-                            final String volumeName = arg;
-                            try {
-                                MediaVolume volume = mVolumeCache.findVolume(volumeName,
-                                        UserHandle.of(userId));
-                                MediaService.onScanVolume(getContext(), volume, REASON_DEMAND);
-                            } catch (FileNotFoundException e) {
-                                Log.w(TAG, "Failed to find volume " + volumeName, e);
-                            }
-                            break;
-                        }
-                    }
-                    return res;
+                    final MediaVolume volume = mVolumeCache.findVolume(volumeName,
+                            UserHandle.of(userId));
+                    MediaService.onScanVolume(getContext(), volume, REASON_DEMAND);
+                } catch (FileNotFoundException e) {
+                    Log.w(TAG, "Failed to find volume " + volumeName, e);
                 } catch (IOException e) {
                     throw new RuntimeException(e);
                 } finally {
                     restoreCallingIdentity(providerToken);
                     restoreLocalCallingIdentity(token);
                 }
+                return Bundle.EMPTY;
             }
             case MediaStore.GET_VERSION_CALL: {
                 final String volumeName = extras.getString(Intent.EXTRA_TEXT);
diff --git a/src/com/android/providers/media/scan/ModernMediaScanner.java b/src/com/android/providers/media/scan/ModernMediaScanner.java
index 0a84838a5..55a4a813e 100644
--- a/src/com/android/providers/media/scan/ModernMediaScanner.java
+++ b/src/com/android/providers/media/scan/ModernMediaScanner.java
@@ -241,12 +241,17 @@ public class ModernMediaScanner implements MediaScanner {
     @Override
     public void scanDirectory(@NonNull File file, @ScanReason int reason) {
         requireNonNull(file);
+        try {
+            file = file.getCanonicalFile();
+        } catch (IOException e) {
+            Log.e(TAG, "Couldn't canonicalize directory to scan" + file, e);
+            return;
+        }
 
         try (Scan scan = new Scan(file, reason)) {
             scan.run();
         } catch (FileNotFoundException e) {
             Log.e(TAG, "Couldn't find directory to scan", e);
-            return;
         } catch (OperationCanceledException ignored) {
             // No-op.
         }
@@ -256,6 +261,12 @@ public class ModernMediaScanner implements MediaScanner {
     @Nullable
     public Uri scanFile(@NonNull File file, @ScanReason int reason) {
         requireNonNull(file);
+        try {
+            file = file.getCanonicalFile();
+        } catch (IOException e) {
+            Log.e(TAG, "Couldn't canonicalize file to scan" + file, e);
+            return null;
+        }
 
         try (Scan scan = new Scan(file, reason)) {
             scan.run();
@@ -292,10 +303,18 @@ public class ModernMediaScanner implements MediaScanner {
     }
 
     @Override
-    public void onDirectoryDirty(File dir) {
+    public void onDirectoryDirty(@NonNull File dir) {
+        requireNonNull(dir);
+        try {
+            dir = dir.getCanonicalFile();
+        } catch (IOException e) {
+            Log.e(TAG, "Couldn't canonicalize directory" + dir, e);
+            return;
+        }
+
         synchronized (mPendingCleanDirectories) {
             mPendingCleanDirectories.remove(dir.getPath());
-            FileUtils.setDirectoryDirty(dir, /*isDirty*/ true);
+            FileUtils.setDirectoryDirty(dir, /* isDirty */ true);
         }
     }
 
diff --git a/src/com/android/providers/media/util/FileUtils.java b/src/com/android/providers/media/util/FileUtils.java
index 376cdf355..00504f4c7 100644
--- a/src/com/android/providers/media/util/FileUtils.java
+++ b/src/com/android/providers/media/util/FileUtils.java
@@ -1113,18 +1113,25 @@ public class FileUtils {
     }
 
     public static @Nullable String extractRelativePath(@Nullable String data) {
-        data = getCanonicalPath(data);
         if (data == null) return null;
 
-        final Matcher matcher = PATTERN_RELATIVE_PATH.matcher(data);
+        final String path;
+        try {
+            path = getCanonicalPath(data);
+        } catch (IOException e) {
+            Log.d(TAG, "Unable to get canonical path from invalid data path: " + data, e);
+            return null;
+        }
+
+        final Matcher matcher = PATTERN_RELATIVE_PATH.matcher(path);
         if (matcher.find()) {
-            final int lastSlash = data.lastIndexOf('/');
+            final int lastSlash = path.lastIndexOf('/');
             if (lastSlash == -1 || lastSlash < matcher.end()) {
                 // This is a file in the top-level directory, so relative path is "/"
                 // which is different than null, which means unknown path
                 return "/";
             } else {
-                return data.substring(matcher.end(), lastSlash + 1);
+                return path.substring(matcher.end(), lastSlash + 1);
             }
         } else {
             return null;
@@ -1817,15 +1824,29 @@ public class FileUtils {
         return new File(file.getPath().replaceFirst(FUSE_FS_PREFIX, LOWER_FS_PREFIX));
     }
 
-    @Nullable
-    private static String getCanonicalPath(@Nullable String path) {
-        if (path == null) return null;
+    /**
+     * Returns the canonical {@link File} for the provided abstract pathname.
+     *
+     * @return The canonical pathname string denoting the same file or directory as this abstract
+     *         pathname
+     * @see File#getCanonicalFile()
+     */
+    @NonNull
+    public static File getCanonicalFile(@NonNull String path) throws IOException {
+        Objects.requireNonNull(path);
+        return new File(path).getCanonicalFile();
+    }
 
-        try {
-            return new File(path).getCanonicalPath();
-        } catch (IOException e) {
-            Log.d(TAG, "Unable to get canonical path from invalid data path: " + path, e);
-            return null;
-        }
+    /**
+     * Returns the canonical pathname string of the provided abstract pathname.
+     *
+     * @return The canonical pathname string denoting the same file or directory as this abstract
+     *         pathname.
+     * @see File#getCanonicalPath()
+     */
+    @NonNull
+    public static String getCanonicalPath(@NonNull String path) throws IOException {
+        Objects.requireNonNull(path);
+        return new File(path).getCanonicalPath();
     }
 }