Android: apply bsdiff patches during package install

Author: ofalvai

android/app/build.gradle

@@ -96,6 +96,7 @@ dependencies {
     implementation 'com.nimbusds:nimbus-jose-jwt:9.37.3'
 
     testImplementation 'junit:junit:4.13.2'
+    testImplementation 'org.json:json:20231013'
 
     androidTestImplementation 'junit:junit:4.13.2'
     androidTestImplementation 'androidx.test.ext:junit:1.2.1'

android/app/src/main/java/com/microsoft/codepush/react/CodePushConstants.java

@@ -10,6 +10,8 @@ public class CodePushConstants {
     public static final String CURRENT_PACKAGE_KEY = "currentPackage";
     public static final String DEFAULT_JS_BUNDLE_NAME = "index.android.bundle";
     public static final String DIFF_MANIFEST_FILE_NAME = "hotcodepush.json";
+    // Folder within the update ZIP that contains the diff patches. Must be in sync with server-side impl.
+    public static final String DIFF_PATCHES_FOLDER_NAME = "__hcp_patches";
     public static final int DOWNLOAD_BUFFER_SIZE = 1024 * 256;
     public static final String DOWNLOAD_FILE_NAME = "download.zip";
     public static final String DOWNLOAD_PROGRESS_EVENT_NAME = "CodePushDownloadProgress";

android/app/src/main/java/com/microsoft/codepush/react/CodePushUpdateManager.java

@@ -2,6 +2,11 @@
 
 import android.os.Build;
 
+import com.microsoft.codepush.react.diffpatch.BinaryDiffPatcher;
+import com.microsoft.codepush.react.diffpatch.DiffManifest;
+import com.microsoft.codepush.react.diffpatch.DiffManifestKt;
+
+import org.json.JSONException;
 import org.json.JSONObject;
 
 import java.io.BufferedInputStream;
@@ -237,14 +242,33 @@ public void downloadPackage(JSONObject updatePackage, String expectedBundleFileN
             String diffManifestFilePath = CodePushUtils.appendPathComponent(unzippedFolderPath,
                     CodePushConstants.DIFF_MANIFEST_FILE_NAME);
             boolean isDiffUpdate = FileUtils.fileAtPathExists(diffManifestFilePath);
+            DiffManifest diffManifest = null;
             if (isDiffUpdate) {
+                try {
+                    diffManifest = DiffManifestKt.parseDiffManifest(CodePushUtils.getJsonObjectFromFile(diffManifestFilePath));
+                } catch (JSONException e) {
+                    throw new CodePushMalformedDataException(diffManifestFilePath, e);
+                }
                 String currentPackageFolderPath = getCurrentPackageFolderPath();
-                CodePushUpdateUtils.copyNecessaryFilesFromCurrentPackage(diffManifestFilePath, currentPackageFolderPath, newUpdateFolderPath);
+                CodePushUpdateUtils.copyNecessaryFilesFromCurrentPackage(diffManifest, currentPackageFolderPath, newUpdateFolderPath);
                 File diffManifestFile = new File(diffManifestFilePath);
                 diffManifestFile.delete();
             }
 
             FileUtils.copyDirectoryContents(unzippedFolderPath, newUpdateFolderPath);
+
+            if (isDiffUpdate) {
+                // Run patching after copyNecessaryFilesFromCurrentPackage() so patched output overwrites
+                // bytes copied in from the old package at the same paths.
+                if (diffManifest.getVersion() == 2) {
+                    String currentPackageFolderPath = getCurrentPackageFolderPath();
+                    BinaryDiffPatcher.applyBinaryDiffPatches(diffManifest, new File(currentPackageFolderPath), new File(unzippedFolderPath), new File(newUpdateFolderPath));
+                    FileUtils.deleteDirectoryAtPath(new File(newUpdateFolderPath, CodePushConstants.DIFF_PATCHES_FOLDER_NAME).getPath());
+                } else if (diffManifest.getVersion() > 2) {
+                    throw new IOException("Diff manifest version " + diffManifest.getVersion() + " is not supported by this SDK version.");
+                }
+            }
+
             FileUtils.deleteFileAtPathSilently(unzippedFolderPath);
 
             // For zip updates, we need to find the relative path to the jsBundle and save it in the

android/app/src/main/java/com/microsoft/codepush/react/CodePushUpdateUtils.java

@@ -3,26 +3,24 @@
 import android.content.Context;
 import android.util.Base64;
 
+import com.microsoft.codepush.react.diffpatch.DiffManifest;
+import com.microsoft.codepush.react.diffpatch.Sha256;
+
 import com.nimbusds.jose.JWSVerifier;
 import com.nimbusds.jose.crypto.RSASSAVerifier;
 import com.nimbusds.jwt.SignedJWT;
 
 import java.security.interfaces.*;
 
 import org.json.JSONArray;
-import org.json.JSONException;
-import org.json.JSONObject;
 
 import java.io.ByteArrayInputStream;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
-import java.security.DigestInputStream;
 import java.security.KeyFactory;
-import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
 import java.security.PublicKey;
 import java.security.spec.X509EncodedKeySpec;
 import java.util.ArrayList;
@@ -73,51 +71,25 @@ private static void addContentsOfFolderToManifest(String folderPath, String path
     }
 
     private static String computeHash(InputStream dataStream) {
-        MessageDigest messageDigest = null;
-        DigestInputStream digestInputStream = null;
         try {
-            messageDigest = MessageDigest.getInstance("SHA-256");
-            digestInputStream = new DigestInputStream(dataStream, messageDigest);
-            byte[] byteBuffer = new byte[1024 * 8];
-            while (digestInputStream.read(byteBuffer) != -1) ;
-        } catch (NoSuchAlgorithmException | IOException e) {
+            return Sha256.sha256Hex(dataStream);
+        } catch (Exception e) {
             // Should not happen.
             throw new CodePushUnknownException("Unable to compute hash of update contents.", e);
-        } finally {
-            try {
-                if (digestInputStream != null) {
-                    digestInputStream.close();
-                }
-                if (dataStream != null) {
-                    dataStream.close();
-                }
-            } catch (IOException e) {
-                e.printStackTrace();
-            }
         }
-
-        byte[] hash = messageDigest.digest();
-        return String.format("%064x", new java.math.BigInteger(1, hash));
     }
 
-    public static void copyNecessaryFilesFromCurrentPackage(String diffManifestFilePath, String currentPackageFolderPath, String newPackageFolderPath) throws IOException {
+    public static void copyNecessaryFilesFromCurrentPackage(DiffManifest diffManifest, String currentPackageFolderPath, String newPackageFolderPath) throws IOException {
         if (currentPackageFolderPath == null || !new File(currentPackageFolderPath).exists()) {
             CodePushUtils.log("Unable to copy files from current package during diff update, because currentPackageFolderPath is invalid.");
             return;
         }
         FileUtils.copyDirectoryContents(currentPackageFolderPath, newPackageFolderPath);
-        JSONObject diffManifest = CodePushUtils.getJsonObjectFromFile(diffManifestFilePath);
-        try {
-            JSONArray deletedFiles = diffManifest.getJSONArray("deletedFiles");
-            for (int i = 0; i < deletedFiles.length(); i++) {
-                String fileNameToDelete = deletedFiles.getString(i);
-                File fileToDelete = new File(newPackageFolderPath, fileNameToDelete);
-                if (fileToDelete.exists()) {
-                    fileToDelete.delete();
-                }
+        for (String fileNameToDelete : diffManifest.getDeletedFiles()) {
+            File fileToDelete = new File(newPackageFolderPath, fileNameToDelete);
+            if (fileToDelete.exists()) {
+                fileToDelete.delete();
             }
-        } catch (JSONException e) {
-            throw new CodePushUnknownException("Unable to copy files from current package during diff update", e);
         }
     }
 

android/app/src/main/java/com/microsoft/codepush/react/diffpatch/BinaryDiffPatcher.kt

@@ -0,0 +1,54 @@
+@file:JvmName("BinaryDiffPatcher")
+package com.microsoft.codepush.react.diffpatch
+
+import java.io.File
+import java.io.IOException
+
+class BinaryDiffApplyException(val relativePath: String, reason: String) :
+    IOException("Failed to apply binary diff patch for \"$relativePath\": $reason")
+
+@JvmOverloads
+fun applyBinaryDiffPatches(
+    manifest: DiffManifest,
+    currentPackageFolder: File,
+    unzippedFolder: File,
+    newUpdateFolder: File,
+    patchApplier: PatchApplier = NativeBsdiffPatchApplier,
+) {
+    for ((relativePath, entry) in manifest.patchedFiles) {
+        if (entry.algo != "bsdiff") {
+            throw BinaryDiffApplyException(relativePath, "unsupported patch algorithm: ${entry.algo}")
+        }
+    }
+
+    for ((relativePath, entry) in manifest.patchedFiles) {
+        val oldFile = resolveWithin(currentPackageFolder, relativePath)
+        if (sha256Hex(oldFile) != entry.baseHash) {
+            throw BinaryDiffApplyException(relativePath, "baseHash mismatch")
+        }
+
+        val diffFile = resolveWithin(unzippedFolder, entry.patch)
+        val newFile = resolveWithin(newUpdateFolder, relativePath).apply { parentFile?.mkdirs() }
+
+        val result = patchApplier.apply(oldFile, diffFile, newFile)
+        if (result != DiffPatch.PatchResult.OK) {
+            throw BinaryDiffApplyException(relativePath, "patch failed: $result")
+        }
+
+        if (sha256Hex(newFile) != entry.targetHash) {
+            throw BinaryDiffApplyException(relativePath, "targetHash mismatch")
+        }
+    }
+}
+
+// Manifest-supplied paths come from the update's JSON, so we treat them as untrusted.
+// Resolve them strictly under `base` and reject anything ("../../etc", an absolute path) that would otherwise
+// let a manifest entry read or write outside the package/patch folders.
+private fun resolveWithin(base: File, relativePath: String): File {
+    val baseCanonical = base.canonicalFile
+    val resolved = File(base, relativePath).canonicalFile
+    if (resolved != baseCanonical && !resolved.path.startsWith(baseCanonical.path + File.separator)) {
+        throw BinaryDiffApplyException(relativePath, "path escapes expected directory")
+    }
+    return resolved
+}

android/app/src/main/java/com/microsoft/codepush/react/diffpatch/DiffManifest.kt

@@ -0,0 +1,55 @@
+package com.microsoft.codepush.react.diffpatch
+
+import org.json.JSONException
+import org.json.JSONObject
+
+data class PatchedFileEntry(
+    // The only value this client understands at the moment is "bsdiff".
+    val algo: String,
+    // SHA-256 hex of the file's content in the currently installed package
+    // Should be checked before patching.
+    val baseHash: String,
+    // SHA-256 hex the patched output must match, should be checked after patching.
+    val targetHash: String,
+    // Zip-relative path to the patch file, under the reserved prefix (CodePushConstants.DIFF_PATCHES_FOLDER_NAME).
+    val patch: String,
+)
+
+data class DiffManifest(
+    // No version field, or version 1: original format, file-by-file patching only.
+    // Version 2: adds support for binary diff patching.
+    val version: Int,
+    // Relative paths, from the old package, to delete rather than carry over into the new one.
+    val deletedFiles: List<String>,
+    // Map key: file's relative path in the package being installed.
+    val patchedFiles: Map<String, PatchedFileEntry>,
+)
+
+@Throws(JSONException::class)
+fun parseDiffManifest(json: JSONObject): DiffManifest {
+    val version = if (json.has("version")) json.getInt("version") else 1
+
+    val deletedFilesJson = json.optJSONArray("deletedFiles")
+    val deletedFiles = if (deletedFilesJson != null) {
+        (0 until deletedFilesJson.length()).map { deletedFilesJson.getString(it) }
+    } else {
+        emptyList()
+    }
+
+    val patchedFilesJson = json.optJSONObject("patchedFiles")
+    val patchedFiles = if (patchedFilesJson != null) {
+        patchedFilesJson.keys().asSequence().associateWith { relativePath ->
+            val entry = patchedFilesJson.getJSONObject(relativePath)
+            PatchedFileEntry(
+                algo = entry.getString("algo"),
+                baseHash = entry.getString("baseHash"),
+                targetHash = entry.getString("targetHash"),
+                patch = entry.getString("patch"),
+            )
+        }
+    } else {
+        emptyMap()
+    }
+
+    return DiffManifest(version = version, deletedFiles = deletedFiles, patchedFiles = patchedFiles)
+}

android/app/src/main/java/com/microsoft/codepush/react/diffpatch/DiffPatch.kt

@@ -1,5 +1,19 @@
 package com.microsoft.codepush.react.diffpatch
 
+import java.io.File
+
+// Purposes of this interface:
+// 1. Allows unit testing the business logic by substituting a fake PatchApplier.
+// 2. Allows the SDK to support multiple patching algorithms in the future, if we ever need to.
+interface PatchApplier {
+    fun apply(oldFile: File, diffFile: File, newFile: File): DiffPatch.PatchResult
+}
+
+object NativeBsdiffPatchApplier : PatchApplier {
+    override fun apply(oldFile: File, diffFile: File, newFile: File) =
+        DiffPatch.applyPatch(oldFile.path, diffFile.path, newFile.path)
+}
+
 object DiffPatch {
 
     /**

android/app/src/main/java/com/microsoft/codepush/react/diffpatch/Sha256.kt

@@ -0,0 +1,21 @@
+@file:JvmName("Sha256")
+package com.microsoft.codepush.react.diffpatch
+
+import java.io.File
+import java.io.InputStream
+import java.math.BigInteger
+import java.security.DigestInputStream
+import java.security.MessageDigest
+
+fun sha256Hex(file: File): String = file.inputStream().use { sha256Hex(it) }
+
+fun sha256Hex(inputStream: InputStream): String {
+    val messageDigest = MessageDigest.getInstance("SHA-256")
+    DigestInputStream(inputStream, messageDigest).use { digestInputStream ->
+        val buffer = ByteArray(1024 * 8)
+        while (digestInputStream.read(buffer) != -1) {
+            // Drain the stream; DigestInputStream updates the digest as a side effect.
+        }
+    }
+    return String.format("%064x", BigInteger(1, messageDigest.digest()))
+}