Merge "Support regular fs-verity Merkle tree" (c3c71728) · Commits · e / os / android_frameworks_base

core/java/android/util/apk/ApkVerityBuilder.java

+91 −25

Original line number	Diff line number	Diff line
		@@ -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 {
		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;
		long dataSize = apk.length() - signingBlockSize;
		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);
		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.
		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.
		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--) {
		@@ -434,7 +499,8 @@ 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: "