Merge "Support regular fs-verity Merkle tree"

1 files changed, 91 insertions, 25 deletions

diff --git a/core/java/android/util/apk/ApkVerityBuilder.java b/core/java/android/util/apk/ApkVerityBuilder.java
index 553511d73670..edd09f8f73c4 100644
--- a/core/java/android/util/apk/ApkVerityBuilder.java
+++ b/core/java/android/util/apk/ApkVerityBuilder.java
@@ -40,7 +40,7 @@ import java.util.ArrayList;
  *
  * @hide
  */
-abstract class ApkVerityBuilder {
+public abstract class ApkVerityBuilder {
     private ApkVerityBuilder() {}
 
     private static final int CHUNK_SIZE_BYTES = 4096;  // Typical Linux block size
@@ -51,12 +51,18 @@ abstract class ApkVerityBuilder {
     private static final String JCA_DIGEST_ALGORITHM = "SHA-256";
     private static final byte[] DEFAULT_SALT = new byte[8];
 
-    static class ApkVerityResult {
+    /** Result generated by the builder. */
+    public static class ApkVerityResult {
+        /** Raw fs-verity metadata and Merkle tree ready to be deployed on disk. */
         public final ByteBuffer verityData;
+
+        /** Size of the Merkle tree in {@code verityData}. */
         public final int merkleTreeSize;
+
+        /** Root hash of the Merkle tree. */
         public final byte[] rootHash;
 
-        ApkVerityResult(ByteBuffer verityData, int merkleTreeSize, byte[] rootHash) {
+        private ApkVerityResult(ByteBuffer verityData, int merkleTreeSize, byte[] rootHash) {
             this.verityData = verityData;
             this.merkleTreeSize = merkleTreeSize;
             this.rootHash = rootHash;
@@ -65,19 +71,47 @@ abstract class ApkVerityBuilder {
 
     /**
      * Generates the 4k, SHA-256 based Merkle tree for the given APK and stores in the {@link
-     * ByteBuffer} created by the {@link ByteBufferFactory}.  The Merkle tree is suitable to be used
-     * as the on-disk format for apk-verity.
+     * ByteBuffer} created by the {@link ByteBufferFactory}.  The output is suitable to be used as
+     * the on-disk format for fs-verity to use.
      *
      * @return ApkVerityResult containing a buffer with the generated Merkle tree stored at the
      *         front, the tree size, and the calculated root hash.
      */
     @NonNull
-    static ApkVerityResult generateApkVerityTree(@NonNull RandomAccessFile apk,
+    public static ApkVerityResult generateFsVerityTree(@NonNull RandomAccessFile apk,
+            @NonNull ByteBufferFactory bufferFactory)
+            throws IOException, SecurityException, NoSuchAlgorithmException, DigestException {
+        return generateVerityTree(apk, bufferFactory, null /* signatureInfo */,
+                false /* skipSigningBlock */);
+    }
+
+    /**
+     * Generates the 4k, SHA-256 based Merkle tree for the given APK and stores in the {@link
+     * ByteBuffer} created by the {@link ByteBufferFactory}.  The Merkle tree does not cover Signing
+     * Block specificed in {@code signatureInfo}.  The output is suitable to be used as the on-disk
+     * format for fs-verity to use (with elide and patch extensions).
+     *
+     * @return ApkVerityResult containing a buffer with the generated Merkle tree stored at the
+     *         front, the tree size, and the calculated root hash.
+     */
+    @NonNull
+    public static ApkVerityResult generateApkVerityTree(@NonNull RandomAccessFile apk,
             @Nullable SignatureInfo signatureInfo, @NonNull ByteBufferFactory bufferFactory)
             throws IOException, SecurityException, NoSuchAlgorithmException, DigestException {
-        long signingBlockSize =
-                signatureInfo.centralDirOffset - signatureInfo.apkSigningBlockOffset;
-        long dataSize = apk.length() - signingBlockSize;
+        return generateVerityTree(apk, bufferFactory, signatureInfo, true /* skipSigningBlock */);
+    }
+
+    @NonNull
+    private static ApkVerityResult generateVerityTree(@NonNull RandomAccessFile apk,
+            @NonNull ByteBufferFactory bufferFactory, @Nullable SignatureInfo signatureInfo,
+            boolean skipSigningBlock)
+            throws IOException, SecurityException, NoSuchAlgorithmException, DigestException {
+        long dataSize = apk.length();
+        if (skipSigningBlock) {
+            long signingBlockSize =
+                    signatureInfo.centralDirOffset - signatureInfo.apkSigningBlockOffset;
+            dataSize -= signingBlockSize;
+        }
         int[] levelOffset = calculateVerityLevelOffset(dataSize);
         int merkleTreeSize = levelOffset[levelOffset.length - 1];
 
@@ -85,10 +119,11 @@ abstract class ApkVerityBuilder {
                 merkleTreeSize
                 + CHUNK_SIZE_BYTES);  // maximum size of apk-verity metadata
         output.order(ByteOrder.LITTLE_ENDIAN);
-
         ByteBuffer tree = slice(output, 0, merkleTreeSize);
-        byte[] apkRootHash = generateApkVerityTreeInternal(apk, signatureInfo, DEFAULT_SALT,
-                levelOffset, tree);
+        // Only use default salt in legacy case.
+        byte[] salt = skipSigningBlock ? DEFAULT_SALT : null;
+        byte[] apkRootHash = generateVerityTreeInternal(apk, signatureInfo, salt, levelOffset,
+                tree, skipSigningBlock);
         return new ApkVerityResult(output, merkleTreeSize, apkRootHash);
     }
 
@@ -138,7 +173,8 @@ abstract class ApkVerityBuilder {
             throws IOException, SignatureNotFoundException, SecurityException, DigestException,
                    NoSuchAlgorithmException {
         try (RandomAccessFile apk = new RandomAccessFile(apkPath, "r")) {
-            ApkVerityResult result = generateApkVerityTree(apk, signatureInfo, bufferFactory);
+            ApkVerityResult result = generateVerityTree(apk, bufferFactory, signatureInfo,
+                    true /* skipSigningBlock */);
             ByteBuffer footer = slice(result.verityData, result.merkleTreeSize,
                     result.verityData.limit());
             generateApkVerityFooter(apk, signatureInfo, footer);
@@ -170,11 +206,14 @@ abstract class ApkVerityBuilder {
         private final byte[] mDigestBuffer = new byte[DIGEST_SIZE_BYTES];
         private final byte[] mSalt;
 
-        private BufferedDigester(byte[] salt, ByteBuffer output) throws NoSuchAlgorithmException {
+        private BufferedDigester(@Nullable byte[] salt, @NonNull ByteBuffer output)
+                throws NoSuchAlgorithmException {
             mSalt = salt;
             mOutput = output.slice();
             mMd = MessageDigest.getInstance(JCA_DIGEST_ALGORITHM);
-            mMd.update(mSalt);
+            if (mSalt != null) {
+                mMd.update(mSalt);
+            }
             mBytesDigestedSinceReset = 0;
         }
 
@@ -201,7 +240,9 @@ abstract class ApkVerityBuilder {
                     mMd.digest(mDigestBuffer, 0, mDigestBuffer.length);
                     mOutput.put(mDigestBuffer);
                     // After digest, MessageDigest resets automatically, so no need to reset again.
-                    mMd.update(mSalt);
+                    if (mSalt != null) {
+                        mMd.update(mSalt);
+                    }
                     mBytesDigestedSinceReset = 0;
                 }
             }
@@ -242,6 +283,26 @@ abstract class ApkVerityBuilder {
     // thus the syscall overhead is not too big.
     private static final int MMAP_REGION_SIZE_BYTES = 1024 * 1024;
 
+    private static void generateFsVerityDigestAtLeafLevel(RandomAccessFile file, ByteBuffer output)
+            throws IOException, NoSuchAlgorithmException, DigestException {
+        BufferedDigester digester = new BufferedDigester(null /* salt */, output);
+
+        // 1. Digest the whole file by chunks.
+        consumeByChunk(digester,
+                new MemoryMappedFileDataSource(file.getFD(), 0, file.length()),
+                MMAP_REGION_SIZE_BYTES);
+
+        // 2. Pad 0s up to the nearest 4096-byte block before hashing.
+        int lastIncompleteChunkSize = (int) (file.length() % CHUNK_SIZE_BYTES);
+        if (lastIncompleteChunkSize != 0) {
+            digester.consume(ByteBuffer.allocate(CHUNK_SIZE_BYTES - lastIncompleteChunkSize));
+        }
+        digester.assertEmptyBuffer();
+
+        // 3. Fill up the rest of buffer with 0s.
+        digester.fillUpLastOutputChunk();
+    }
+
     private static void generateApkVerityDigestAtLeafLevel(RandomAccessFile apk,
             SignatureInfo signatureInfo, byte[] salt, ByteBuffer output)
             throws IOException, NoSuchAlgorithmException, DigestException {
@@ -288,15 +349,19 @@ abstract class ApkVerityBuilder {
     }
 
     @NonNull
-    private static byte[] generateApkVerityTreeInternal(@NonNull RandomAccessFile apk,
-            @Nullable SignatureInfo signatureInfo, @NonNull byte[] salt,
-            @NonNull int[] levelOffset, @NonNull ByteBuffer output)
+    private static byte[] generateVerityTreeInternal(@NonNull RandomAccessFile apk,
+            @Nullable SignatureInfo signatureInfo, @Nullable byte[] salt,
+            @NonNull int[] levelOffset, @NonNull ByteBuffer output, boolean skipSigningBlock)
             throws IOException, NoSuchAlgorithmException, DigestException {
-        assertSigningBlockAlignedAndHasFullPages(signatureInfo);
-
         // 1. Digest the apk to generate the leaf level hashes.
-        generateApkVerityDigestAtLeafLevel(apk, signatureInfo, salt, slice(output,
-                    levelOffset[levelOffset.length - 2], levelOffset[levelOffset.length - 1]));
+        if (skipSigningBlock) {
+            assertSigningBlockAlignedAndHasFullPages(signatureInfo);
+            generateApkVerityDigestAtLeafLevel(apk, signatureInfo, salt, slice(output,
+                        levelOffset[levelOffset.length - 2], levelOffset[levelOffset.length - 1]));
+        } else {
+            generateFsVerityDigestAtLeafLevel(apk, slice(output,
+                        levelOffset[levelOffset.length - 2], levelOffset[levelOffset.length - 1]));
+        }
 
         // 2. Digest the lower level hashes bottom up.
         for (int level = levelOffset.length - 3; level >= 0; level--) {
@@ -434,10 +499,11 @@ abstract class ApkVerityBuilder {
         return levelOffset;
     }
 
-    private static void assertSigningBlockAlignedAndHasFullPages(SignatureInfo signatureInfo) {
+    private static void assertSigningBlockAlignedAndHasFullPages(
+            @NonNull SignatureInfo signatureInfo) {
         if (signatureInfo.apkSigningBlockOffset % CHUNK_SIZE_BYTES != 0) {
             throw new IllegalArgumentException(
-                    "APK Signing Block does not start at the page  boundary: "
+                    "APK Signing Block does not start at the page boundary: "
                     + signatureInfo.apkSigningBlockOffset);
         }