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Implement verity header and extension generation

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Test: build
Bug: 30972906
Change-Id: I3eff98231525fc248a7df2fb9b74a4c3b9f708b7
This commit is contained in:
Victor Hsieh
2018-01-12 08:28:03 -08:00
parent 69995cddbb
commit 3051d78225
1 changed files with 159 additions and 34 deletions
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193
core/java/android/util/apk/ApkVerityBuilder.java
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@@ -68,31 +68,78 @@ abstract class ApkVerityBuilder {
static ApkVerityResult generateApkVerity(RandomAccessFile apk,
SignatureInfo signatureInfo, ByteBufferFactory bufferFactory)
throws IOException, SecurityException, NoSuchAlgorithmException, DigestException {
long signingBlockSize =
signatureInfo.centralDirOffset - signatureInfo.apkSigningBlockOffset;
long dataSize = apk.length() - signingBlockSize - ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE;
int[] levelOffset = calculateVerityLevelOffset(dataSize);
ByteBuffer output = bufferFactory.create(
CHUNK_SIZE_BYTES + // fsverity header + extensions + padding
levelOffset[levelOffset.length - 1]); // Merkle tree size
output.order(ByteOrder.LITTLE_ENDIAN);
ByteBuffer header = slice(output, 0, FSVERITY_HEADER_SIZE_BYTES);
ByteBuffer extensions = slice(output, FSVERITY_HEADER_SIZE_BYTES, CHUNK_SIZE_BYTES);
ByteBuffer tree = slice(output, CHUNK_SIZE_BYTES, output.limit());
byte[] apkDigestBytes = new byte[DIGEST_SIZE_BYTES];
ByteBuffer apkDigest = ByteBuffer.wrap(apkDigestBytes);
apkDigest.order(ByteOrder.LITTLE_ENDIAN);
calculateFsveritySignatureInternal(apk, signatureInfo, tree, apkDigest, header, extensions);
output.rewind();
return new ApkVerityResult(output, apkDigestBytes);
}
/**
* Calculates the fsverity root hash for integrity measurement. This needs to be consistent to
* what kernel returns.
*/
static byte[] generateFsverityRootHash(RandomAccessFile apk, ByteBuffer apkDigest,
SignatureInfo signatureInfo)
throws NoSuchAlgorithmException, DigestException, IOException {
ByteBuffer verityBlock = ByteBuffer.allocate(CHUNK_SIZE_BYTES)
.order(ByteOrder.LITTLE_ENDIAN);
ByteBuffer header = slice(verityBlock, 0, FSVERITY_HEADER_SIZE_BYTES);
ByteBuffer extensions = slice(verityBlock, FSVERITY_HEADER_SIZE_BYTES, CHUNK_SIZE_BYTES);
calculateFsveritySignatureInternal(apk, signatureInfo, null, null, header, extensions);
MessageDigest md = MessageDigest.getInstance(JCA_DIGEST_ALGORITHM);
md.update(DEFAULT_SALT);
md.update(verityBlock);
md.update(apkDigest);
return md.digest();
}
private static void calculateFsveritySignatureInternal(
RandomAccessFile apk, SignatureInfo signatureInfo, ByteBuffer treeOutput,
ByteBuffer rootHashOutput, ByteBuffer headerOutput, ByteBuffer extensionsOutput)
throws IOException, NoSuchAlgorithmException, DigestException {
assertSigningBlockAlignedAndHasFullPages(signatureInfo);
long signingBlockSize =
signatureInfo.centralDirOffset - signatureInfo.apkSigningBlockOffset;
long dataSize = apk.length() - signingBlockSize - ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE;
int[] levelOffset = calculateVerityLevelOffset(dataSize);
ByteBuffer output = bufferFactory.create(
CHUNK_SIZE_BYTES + // fsverity header + extensions + padding
levelOffset[levelOffset.length - 1] + // Merkle tree size
FSVERITY_HEADER_SIZE_BYTES); // second fsverity header (verbatim copy)
// Start generating the tree from the block boundary as the kernel will expect.
ByteBuffer treeOutput = slice(output, CHUNK_SIZE_BYTES,
output.limit() - FSVERITY_HEADER_SIZE_BYTES);
byte[] rootHash = generateApkVerityTree(apk, signatureInfo, DEFAULT_SALT, levelOffset,
treeOutput);
if (treeOutput != null) {
byte[] apkRootHash = generateApkVerityTree(apk, signatureInfo, DEFAULT_SALT,
levelOffset, treeOutput);
if (rootHashOutput != null) {
rootHashOutput.put(apkRootHash);
}
}
ByteBuffer integrityHeader = generateFsverityHeader(apk.length(), DEFAULT_SALT);
output.put(integrityHeader);
output.put(generateFsverityExtensions());
if (headerOutput != null) {
generateFsverityHeader(headerOutput, apk.length(), levelOffset.length - 1,
DEFAULT_SALT);
}
integrityHeader.rewind();
output.put(integrityHeader);
output.rewind();
return new ApkVerityResult(output, rootHash);
if (extensionsOutput != null) {
generateFsverityExtensions(extensionsOutput, signatureInfo.apkSigningBlockOffset,
signingBlockSize, signatureInfo.eocdOffset);
}
}
/**
@@ -211,7 +258,7 @@ abstract class ApkVerityBuilder {
eocdCdOffsetFieldPosition - signatureInfo.centralDirOffset),
MMAP_REGION_SIZE_BYTES);
// 3. Fill up the rest of buffer with 0s.
// 3. Consume offset of Signing Block as an alternative EoCD.
ByteBuffer alternativeCentralDirOffset = ByteBuffer.allocate(
ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE).order(ByteOrder.LITTLE_ENDIAN);
alternativeCentralDirOffset.putInt(Math.toIntExact(signatureInfo.apkSigningBlockOffset));
@@ -259,36 +306,109 @@ abstract class ApkVerityBuilder {
return rootHash;
}
private static ByteBuffer generateFsverityHeader(long fileSize, byte[] salt) {
private static ByteBuffer generateFsverityHeader(ByteBuffer buffer, long fileSize, int depth,
byte[] salt) {
if (salt.length != 8) {
throw new IllegalArgumentException("salt is not 8 bytes long");
}
ByteBuffer buffer = ByteBuffer.allocate(FSVERITY_HEADER_SIZE_BYTES);
buffer.order(ByteOrder.LITTLE_ENDIAN);
// TODO(b/30972906): insert a reference when there is a public one.
// TODO(b/30972906): update the reference when there is a better one in public.
buffer.put("TrueBrew".getBytes()); // magic
buffer.put((byte) 1); // major version
buffer.put((byte) 0); // minor version
buffer.put((byte) 12); // log2(block-size) == log2(4096)
buffer.put((byte) 7); // log2(leaves-per-node) == log2(block-size / digest-size)
// == log2(4096 / 32)
buffer.putShort((short) 1); // meta algorithm, 1: SHA-256 FIXME finalize constant
buffer.putShort((short) 1); // data algorithm, 1: SHA-256 FIXME finalize constant
buffer.putInt(0x1); // flags, 0x1: has extension, FIXME also hide it
buffer.putInt(0); // reserved
buffer.putLong(fileSize); // original i_size
buffer.put(salt); // salt (8 bytes)
buffer.put((byte) 12); // log2(block-size): log2(4096)
buffer.put((byte) 7); // log2(leaves-per-node): log2(4096 / 32)
// TODO(b/30972906): Add extension.
buffer.putShort((short) 1); // meta algorithm, SHA256_MODE == 1
buffer.putShort((short) 1); // data algorithm, SHA256_MODE == 1
buffer.putInt(0x1); // flags, 0x1: has extension
buffer.putInt(0); // reserved
buffer.putLong(fileSize); // original file size
buffer.put((byte) 0); // auth block offset, disabled here
buffer.put(salt); // salt (8 bytes)
// skip(buffer, 22); // reserved
buffer.rewind();
return buffer;
}
private static ByteBuffer generateFsverityExtensions() {
return ByteBuffer.allocate(64); // TODO(b/30972906): implement this.
private static ByteBuffer generateFsverityExtensions(ByteBuffer buffer, long signingBlockOffset,
long signingBlockSize, long eocdOffset) {
// Snapshot of the FSVerity structs (subject to change once upstreamed).
//
// struct fsverity_header_extension {
// u8 extension_count;
// u8 reserved[7];
// };
//
// struct fsverity_extension {
// __le16 length;
// u8 type;
// u8 reserved[5];
// };
//
// struct fsverity_extension_elide {
// __le64 offset;
// __le64 length;
// }
//
// struct fsverity_extension_patch {
// __le64 offset;
// u8 length;
// u8 reserved[7];
// u8 databytes[];
// };
// struct fsverity_header_extension
buffer.put((byte) 2); // extension count
skip(buffer, 3); // reserved
final int kSizeOfFsverityExtensionHeader = 8;
{
// struct fsverity_extension #1
final int kSizeOfFsverityElidedExtension = 16;
buffer.putShort((short) // total size of extension, padded to 64-bit alignment
(kSizeOfFsverityExtensionHeader + kSizeOfFsverityElidedExtension));
buffer.put((byte) 0); // ID of elide extension
skip(buffer, 5); // reserved
// struct fsverity_extension_elide
buffer.putLong(signingBlockOffset);
buffer.putLong(signingBlockSize);
}
{
// struct fsverity_extension #2
final int kSizeOfFsverityPatchExtension =
8 + // offset size
1 + // size of length from offset (up to 255)
7 + // reserved
ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE;
final int kPadding = (int) divideRoundup(kSizeOfFsverityPatchExtension % 8, 8);
buffer.putShort((short) // total size of extension, padded to 64-bit alignment
(kSizeOfFsverityExtensionHeader + kSizeOfFsverityPatchExtension + kPadding));
buffer.put((byte) 1); // ID of patch extension
skip(buffer, 5); // reserved
// struct fsverity_extension_patch
buffer.putLong(eocdOffset); // offset
buffer.put((byte) ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE); // length
skip(buffer, 7); // reserved
buffer.putInt(Math.toIntExact(signingBlockOffset)); // databytes
// There are extra kPadding bytes of 0s here, included in the total size field of the
// extension header. The output ByteBuffer is assumed to be initialized to 0.
}
buffer.rewind();
return buffer;
}
/**
@@ -344,6 +464,11 @@ abstract class ApkVerityBuilder {
return b.slice();
}
/** Skip the {@code ByteBuffer} position by {@code bytes}. */
private static void skip(ByteBuffer buffer, int bytes) {
buffer.position(buffer.position() + bytes);
}
/** Divides a number and round up to the closest integer. */
private static long divideRoundup(long dividend, long divisor) {
return (dividend + divisor - 1) / divisor;