From 056359d8980828bc352f8d930733305547580c96 Mon Sep 17 00:00:00 2001
From: yrom <yrom@qq.com>
Date: Tue, 23 Oct 2018 16:19:49 +0800
Subject: [PATCH] Support writing chanel to apk that signed by android
 signature scheme v3

New scheme requires an extra dummy ID-value block padding to make size a multiple of 4096 bytes

See https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/util/apk/ApkVerityBuilder.java#445

Fixed Meituan-Dianping/walle#256 Meituan-Dianping/walle#255
---
 .../com/meituan/android/walle/ApkUtil.java    |  9 ++++++
 .../android/walle/ApkSigningPayload.java      | 10 +++++++
 .../meituan/android/walle/PayloadWriter.java  | 29 ++++++++++++++++++-
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/payload_reader/src/main/java/com/meituan/android/walle/ApkUtil.java b/payload_reader/src/main/java/com/meituan/android/walle/ApkUtil.java
index 1eba71f..e5151da 100644
--- a/payload_reader/src/main/java/com/meituan/android/walle/ApkUtil.java
+++ b/payload_reader/src/main/java/com/meituan/android/walle/ApkUtil.java
@@ -27,6 +27,15 @@ private ApkUtil() {
       */
     public static final int APK_SIGNATURE_SCHEME_V2_BLOCK_ID = 0x7109871a;
 
+    /**
+     * The padding in APK SIG BLOCK (V3 scheme introduced)
+     * See https://android.googlesource.com/platform/tools/apksig/+/master/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtils.java
+     */
+    public static final int VERITY_PADDING_BLOCK_ID = 0x42726577;
+
+    public static final int ANDROID_COMMON_PAGE_ALIGNMENT_BYTES = 4096;
+
+
     // Our Channel Block ID
     public static final int APK_CHANNEL_BLOCK_ID = 0x71777777;
 
diff --git a/payload_writer/src/main/java/com/meituan/android/walle/ApkSigningPayload.java b/payload_writer/src/main/java/com/meituan/android/walle/ApkSigningPayload.java
index 57fef02..4ba72fd 100644
--- a/payload_writer/src/main/java/com/meituan/android/walle/ApkSigningPayload.java
+++ b/payload_writer/src/main/java/com/meituan/android/walle/ApkSigningPayload.java
@@ -7,6 +7,7 @@
 class ApkSigningPayload {
     private final int id;
     private final ByteBuffer buffer;
+    private final int totalSize;
 
     ApkSigningPayload(final int id, final ByteBuffer buffer) {
         super();
@@ -15,6 +16,8 @@ class ApkSigningPayload {
             throw new IllegalArgumentException("ByteBuffer byte order must be little endian");
         }
         this.buffer = buffer;
+        // assume buffer is not consumed
+        this.totalSize = 8 + 4 + buffer.remaining(); // size + id + value
     }
 
     public int getId() {
@@ -27,4 +30,11 @@ public byte[] getByteBuffer() {
         return Arrays.copyOfRange(array, arrayOffset + buffer.position(),
                 arrayOffset + buffer.limit());
     }
+
+    /**
+     * Total bytes of this block
+     */
+    public int getTotalSize() {
+        return totalSize;
+    }
 }
diff --git a/payload_writer/src/main/java/com/meituan/android/walle/PayloadWriter.java b/payload_writer/src/main/java/com/meituan/android/walle/PayloadWriter.java
index 02e83ea..d34d82d 100644
--- a/payload_writer/src/main/java/com/meituan/android/walle/PayloadWriter.java
+++ b/payload_writer/src/main/java/com/meituan/android/walle/PayloadWriter.java
@@ -174,8 +174,35 @@ static void handleApkSigningBlock(final File apkFile, final ApkSigningBlockHandl
                         "No APK Signature Scheme v2 block in APK Signing Block");
             }
 
-
+            final boolean needPadding = originIdValues.remove(ApkUtil.VERITY_PADDING_BLOCK_ID) != null;
             final ApkSigningBlock apkSigningBlock = handler.handle(originIdValues);
+            // replace VERITY_PADDING_BLOCK with new one
+            if (needPadding) {
+                // uint64:  size (excluding this field)
+                // repeated ID-value pairs:
+                //     uint64:           size (excluding this field)
+                //     uint32:           ID
+                //     (size - 4) bytes: value
+                // (extra dummy ID-value for padding to make block size a multiple of 4096 bytes)
+                // uint64:  size (same as the one above)
+                // uint128: magic
+
+                int blocksSize = 0;
+                for (ApkSigningPayload payload : apkSigningBlock.getPayloads()) {
+                    blocksSize += payload.getTotalSize();
+                }
+
+                int resultSize = 8 + blocksSize + 8 + 16; // size(uint64) + pairs size + size(uint64) + magic(uint128)
+                if (resultSize % ApkUtil.ANDROID_COMMON_PAGE_ALIGNMENT_BYTES != 0) {
+                    int padding = ApkUtil.ANDROID_COMMON_PAGE_ALIGNMENT_BYTES - 12 // size(uint64) + id(uint32)
+                            - (resultSize % ApkUtil.ANDROID_COMMON_PAGE_ALIGNMENT_BYTES);
+                    if (padding < 0) {
+                        padding += ApkUtil.ANDROID_COMMON_PAGE_ALIGNMENT_BYTES;
+                    }
+                    final ByteBuffer dummy =  ByteBuffer.allocate(padding).order(ByteOrder.LITTLE_ENDIAN);
+                    apkSigningBlock.addPayload(new ApkSigningPayload(ApkUtil.VERITY_PADDING_BLOCK_ID,dummy));
+                }
+            }
 
             if (apkSigningBlockOffset != 0 && centralDirStartOffset != 0) {