Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2017 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package android.util.apk; |
| 18 | |
| 19 | import java.io.IOException; |
| 20 | import java.io.RandomAccessFile; |
| 21 | import java.nio.ByteBuffer; |
| 22 | import java.nio.ByteOrder; |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 23 | import java.security.DigestException; |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 24 | import java.security.MessageDigest; |
| 25 | import java.security.NoSuchAlgorithmException; |
| 26 | import java.util.ArrayList; |
| 27 | |
| 28 | /** |
| 29 | * ApkVerityBuilder builds the APK verity tree and the verity header, which will be used by the |
| 30 | * kernel to verity the APK content on access. |
| 31 | * |
| 32 | * <p>Unlike a regular Merkle tree, APK verity tree does not cover the content fully. Due to |
| 33 | * the existing APK format, it has to skip APK Signing Block and also has some special treatment for |
| 34 | * the "Central Directory offset" field of ZIP End of Central Directory. |
| 35 | * |
| 36 | * @hide |
| 37 | */ |
| 38 | abstract class ApkVerityBuilder { |
| 39 | private ApkVerityBuilder() {} |
| 40 | |
| 41 | private static final int CHUNK_SIZE_BYTES = 4096; // Typical Linux block size |
| 42 | private static final int DIGEST_SIZE_BYTES = 32; // SHA-256 size |
| 43 | private static final int FSVERITY_HEADER_SIZE_BYTES = 64; |
| 44 | private static final int ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE = 4; |
| 45 | private static final int ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_OFFSET = 16; |
| 46 | private static final String JCA_DIGEST_ALGORITHM = "SHA-256"; |
| 47 | private static final byte[] DEFAULT_SALT = new byte[8]; |
| 48 | |
| 49 | static class ApkVerityResult { |
| 50 | public final ByteBuffer fsverityData; |
| 51 | public final byte[] rootHash; |
| 52 | |
| 53 | ApkVerityResult(ByteBuffer fsverityData, byte[] rootHash) { |
| 54 | this.fsverityData = fsverityData; |
| 55 | this.rootHash = rootHash; |
| 56 | } |
| 57 | } |
| 58 | |
| 59 | /** |
| 60 | * Generates fsverity metadata and the Merkle tree into the {@link ByteBuffer} created by the |
| 61 | * {@link ByteBufferFactory}. The bytes layout in the buffer will be used by the kernel and is |
| 62 | * ready to be appended to the target file to set up fsverity. For fsverity to work, this data |
| 63 | * must be placed at the next page boundary, and the caller must add additional padding in that |
| 64 | * case. |
| 65 | * |
| 66 | * @return ApkVerityResult containing the fsverity data and the root hash of the Merkle tree. |
| 67 | */ |
| 68 | static ApkVerityResult generateApkVerity(RandomAccessFile apk, |
| 69 | SignatureInfo signatureInfo, ByteBufferFactory bufferFactory) |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 70 | throws IOException, SecurityException, NoSuchAlgorithmException, DigestException { |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 71 | long signingBlockSize = |
| 72 | signatureInfo.centralDirOffset - signatureInfo.apkSigningBlockOffset; |
Victor Hsieh | d48e954 | 2018-01-24 12:06:43 -0800 | [diff] [blame] | 73 | long dataSize = apk.length() - signingBlockSize; |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 74 | int[] levelOffset = calculateVerityLevelOffset(dataSize); |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 75 | int merkleTreeSize = levelOffset[levelOffset.length - 1]; |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 76 | |
| 77 | ByteBuffer output = bufferFactory.create( |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 78 | merkleTreeSize |
| 79 | + CHUNK_SIZE_BYTES); // maximum size of fsverity metadata |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 80 | output.order(ByteOrder.LITTLE_ENDIAN); |
| 81 | |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 82 | ByteBuffer tree = slice(output, 0, merkleTreeSize); |
| 83 | ByteBuffer header = slice(output, merkleTreeSize, |
| 84 | merkleTreeSize + FSVERITY_HEADER_SIZE_BYTES); |
| 85 | ByteBuffer extensions = slice(output, merkleTreeSize + FSVERITY_HEADER_SIZE_BYTES, |
| 86 | merkleTreeSize + CHUNK_SIZE_BYTES); |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 87 | byte[] apkDigestBytes = new byte[DIGEST_SIZE_BYTES]; |
| 88 | ByteBuffer apkDigest = ByteBuffer.wrap(apkDigestBytes); |
| 89 | apkDigest.order(ByteOrder.LITTLE_ENDIAN); |
| 90 | |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 91 | // NB: Buffer limit is set inside once finished. |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 92 | calculateFsveritySignatureInternal(apk, signatureInfo, tree, apkDigest, header, extensions); |
| 93 | |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 94 | // Put the reverse offset to fs-verity header at the end. |
| 95 | output.position(merkleTreeSize + FSVERITY_HEADER_SIZE_BYTES + extensions.limit()); |
| 96 | output.putInt(FSVERITY_HEADER_SIZE_BYTES + extensions.limit() |
| 97 | + 4); // size of this integer right before EOF |
| 98 | output.flip(); |
| 99 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 100 | return new ApkVerityResult(output, apkDigestBytes); |
| 101 | } |
| 102 | |
| 103 | /** |
| 104 | * Calculates the fsverity root hash for integrity measurement. This needs to be consistent to |
| 105 | * what kernel returns. |
| 106 | */ |
| 107 | static byte[] generateFsverityRootHash(RandomAccessFile apk, ByteBuffer apkDigest, |
| 108 | SignatureInfo signatureInfo) |
| 109 | throws NoSuchAlgorithmException, DigestException, IOException { |
| 110 | ByteBuffer verityBlock = ByteBuffer.allocate(CHUNK_SIZE_BYTES) |
| 111 | .order(ByteOrder.LITTLE_ENDIAN); |
| 112 | ByteBuffer header = slice(verityBlock, 0, FSVERITY_HEADER_SIZE_BYTES); |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 113 | ByteBuffer extensions = slice(verityBlock, FSVERITY_HEADER_SIZE_BYTES, |
| 114 | CHUNK_SIZE_BYTES - FSVERITY_HEADER_SIZE_BYTES); |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 115 | |
| 116 | calculateFsveritySignatureInternal(apk, signatureInfo, null, null, header, extensions); |
| 117 | |
| 118 | MessageDigest md = MessageDigest.getInstance(JCA_DIGEST_ALGORITHM); |
Victor Hsieh | 2120323 | 2018-01-29 15:10:56 -0800 | [diff] [blame] | 119 | md.update(header); |
| 120 | md.update(extensions); |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 121 | md.update(apkDigest); |
| 122 | return md.digest(); |
| 123 | } |
| 124 | |
Victor Hsieh | 2120323 | 2018-01-29 15:10:56 -0800 | [diff] [blame] | 125 | /** |
| 126 | * Internal method to generate various parts of FSVerity constructs, including the header, |
| 127 | * extensions, Merkle tree, and the tree's root hash. The output buffer is flipped to the |
| 128 | * generated data size and is readey for consuming. |
| 129 | */ |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 130 | private static void calculateFsveritySignatureInternal( |
| 131 | RandomAccessFile apk, SignatureInfo signatureInfo, ByteBuffer treeOutput, |
| 132 | ByteBuffer rootHashOutput, ByteBuffer headerOutput, ByteBuffer extensionsOutput) |
| 133 | throws IOException, NoSuchAlgorithmException, DigestException { |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 134 | assertSigningBlockAlignedAndHasFullPages(signatureInfo); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 135 | long signingBlockSize = |
| 136 | signatureInfo.centralDirOffset - signatureInfo.apkSigningBlockOffset; |
Victor Hsieh | 4cf7382 | 2018-04-23 14:43:19 -0700 | [diff] [blame] | 137 | long dataSize = apk.length() - signingBlockSize; |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 138 | int[] levelOffset = calculateVerityLevelOffset(dataSize); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 139 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 140 | if (treeOutput != null) { |
| 141 | byte[] apkRootHash = generateApkVerityTree(apk, signatureInfo, DEFAULT_SALT, |
| 142 | levelOffset, treeOutput); |
| 143 | if (rootHashOutput != null) { |
| 144 | rootHashOutput.put(apkRootHash); |
Victor Hsieh | 2120323 | 2018-01-29 15:10:56 -0800 | [diff] [blame] | 145 | rootHashOutput.flip(); |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 146 | } |
| 147 | } |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 148 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 149 | if (headerOutput != null) { |
Victor Hsieh | d48e954 | 2018-01-24 12:06:43 -0800 | [diff] [blame] | 150 | headerOutput.order(ByteOrder.LITTLE_ENDIAN); |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 151 | generateFsverityHeader(headerOutput, apk.length(), levelOffset.length - 1, |
| 152 | DEFAULT_SALT); |
| 153 | } |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 154 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 155 | if (extensionsOutput != null) { |
Victor Hsieh | d48e954 | 2018-01-24 12:06:43 -0800 | [diff] [blame] | 156 | extensionsOutput.order(ByteOrder.LITTLE_ENDIAN); |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 157 | generateFsverityExtensions(extensionsOutput, signatureInfo.apkSigningBlockOffset, |
| 158 | signingBlockSize, signatureInfo.eocdOffset); |
| 159 | } |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 160 | } |
| 161 | |
| 162 | /** |
| 163 | * A helper class to consume and digest data by block continuously, and write into a buffer. |
| 164 | */ |
| 165 | private static class BufferedDigester implements DataDigester { |
| 166 | /** Amount of the data to digest in each cycle before writting out the digest. */ |
| 167 | private static final int BUFFER_SIZE = CHUNK_SIZE_BYTES; |
| 168 | |
| 169 | /** |
| 170 | * Amount of data the {@link MessageDigest} has consumed since the last reset. This must be |
| 171 | * always less than BUFFER_SIZE since {@link MessageDigest} is reset whenever it has |
| 172 | * consumed BUFFER_SIZE of data. |
| 173 | */ |
| 174 | private int mBytesDigestedSinceReset; |
| 175 | |
| 176 | /** The final output {@link ByteBuffer} to write the digest to sequentially. */ |
| 177 | private final ByteBuffer mOutput; |
| 178 | |
| 179 | private final MessageDigest mMd; |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 180 | private final byte[] mDigestBuffer = new byte[DIGEST_SIZE_BYTES]; |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 181 | private final byte[] mSalt; |
| 182 | |
| 183 | private BufferedDigester(byte[] salt, ByteBuffer output) throws NoSuchAlgorithmException { |
| 184 | mSalt = salt; |
| 185 | mOutput = output.slice(); |
| 186 | mMd = MessageDigest.getInstance(JCA_DIGEST_ALGORITHM); |
| 187 | mMd.update(mSalt); |
| 188 | mBytesDigestedSinceReset = 0; |
| 189 | } |
| 190 | |
| 191 | /** |
| 192 | * Consumes and digests data up to BUFFER_SIZE (may continue from the previous remaining), |
| 193 | * then writes the final digest to the output buffer. Repeat until all data are consumed. |
| 194 | * If the last consumption is not enough for BUFFER_SIZE, the state will stay and future |
| 195 | * consumption will continuous from there. |
| 196 | */ |
| 197 | @Override |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 198 | public void consume(ByteBuffer buffer) throws DigestException { |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 199 | int offset = buffer.position(); |
| 200 | int remaining = buffer.remaining(); |
| 201 | while (remaining > 0) { |
| 202 | int allowance = (int) Math.min(remaining, BUFFER_SIZE - mBytesDigestedSinceReset); |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 203 | // Optimization: set the buffer limit to avoid allocating a new ByteBuffer object. |
| 204 | buffer.limit(buffer.position() + allowance); |
| 205 | mMd.update(buffer); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 206 | offset += allowance; |
| 207 | remaining -= allowance; |
| 208 | mBytesDigestedSinceReset += allowance; |
| 209 | |
| 210 | if (mBytesDigestedSinceReset == BUFFER_SIZE) { |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 211 | mMd.digest(mDigestBuffer, 0, mDigestBuffer.length); |
| 212 | mOutput.put(mDigestBuffer); |
| 213 | // After digest, MessageDigest resets automatically, so no need to reset again. |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 214 | mMd.update(mSalt); |
| 215 | mBytesDigestedSinceReset = 0; |
| 216 | } |
| 217 | } |
| 218 | } |
| 219 | |
Victor Hsieh | 3a0032f | 2018-02-20 15:22:28 -0800 | [diff] [blame] | 220 | public void assertEmptyBuffer() throws DigestException { |
| 221 | if (mBytesDigestedSinceReset != 0) { |
| 222 | throw new IllegalStateException("Buffer is not empty: " + mBytesDigestedSinceReset); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 223 | } |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 224 | } |
| 225 | |
| 226 | private void fillUpLastOutputChunk() { |
Victor Hsieh | b62a64e | 2018-01-19 12:46:23 -0800 | [diff] [blame] | 227 | int lastBlockSize = (int) (mOutput.position() % BUFFER_SIZE); |
| 228 | if (lastBlockSize == 0) { |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 229 | return; |
| 230 | } |
Victor Hsieh | b62a64e | 2018-01-19 12:46:23 -0800 | [diff] [blame] | 231 | mOutput.put(ByteBuffer.allocate(BUFFER_SIZE - lastBlockSize)); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 232 | } |
| 233 | } |
| 234 | |
| 235 | /** |
| 236 | * Digest the source by chunk in the given range. If the last chunk is not a full chunk, |
| 237 | * digest the remaining. |
| 238 | */ |
| 239 | private static void consumeByChunk(DataDigester digester, DataSource source, int chunkSize) |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 240 | throws IOException, DigestException { |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 241 | long inputRemaining = source.size(); |
| 242 | long inputOffset = 0; |
| 243 | while (inputRemaining > 0) { |
| 244 | int size = (int) Math.min(inputRemaining, chunkSize); |
| 245 | source.feedIntoDataDigester(digester, inputOffset, size); |
| 246 | inputOffset += size; |
| 247 | inputRemaining -= size; |
| 248 | } |
| 249 | } |
| 250 | |
| 251 | // Rationale: 1) 1 MB should fit in memory space on all devices. 2) It is not too granular |
| 252 | // thus the syscall overhead is not too big. |
| 253 | private static final int MMAP_REGION_SIZE_BYTES = 1024 * 1024; |
| 254 | |
| 255 | private static void generateApkVerityDigestAtLeafLevel(RandomAccessFile apk, |
| 256 | SignatureInfo signatureInfo, byte[] salt, ByteBuffer output) |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 257 | throws IOException, NoSuchAlgorithmException, DigestException { |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 258 | BufferedDigester digester = new BufferedDigester(salt, output); |
| 259 | |
| 260 | // 1. Digest from the beginning of the file, until APK Signing Block is reached. |
| 261 | consumeByChunk(digester, |
| 262 | new MemoryMappedFileDataSource(apk.getFD(), 0, signatureInfo.apkSigningBlockOffset), |
| 263 | MMAP_REGION_SIZE_BYTES); |
| 264 | |
| 265 | // 2. Skip APK Signing Block and continue digesting, until the Central Directory offset |
| 266 | // field in EoCD is reached. |
| 267 | long eocdCdOffsetFieldPosition = |
| 268 | signatureInfo.eocdOffset + ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_OFFSET; |
| 269 | consumeByChunk(digester, |
| 270 | new MemoryMappedFileDataSource(apk.getFD(), signatureInfo.centralDirOffset, |
| 271 | eocdCdOffsetFieldPosition - signatureInfo.centralDirOffset), |
| 272 | MMAP_REGION_SIZE_BYTES); |
| 273 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 274 | // 3. Consume offset of Signing Block as an alternative EoCD. |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 275 | ByteBuffer alternativeCentralDirOffset = ByteBuffer.allocate( |
| 276 | ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE).order(ByteOrder.LITTLE_ENDIAN); |
| 277 | alternativeCentralDirOffset.putInt(Math.toIntExact(signatureInfo.apkSigningBlockOffset)); |
| 278 | alternativeCentralDirOffset.flip(); |
| 279 | digester.consume(alternativeCentralDirOffset); |
| 280 | |
| 281 | // 4. Read from end of the Central Directory offset field in EoCD to the end of the file. |
| 282 | long offsetAfterEocdCdOffsetField = |
| 283 | eocdCdOffsetFieldPosition + ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE; |
| 284 | consumeByChunk(digester, |
| 285 | new MemoryMappedFileDataSource(apk.getFD(), offsetAfterEocdCdOffsetField, |
| 286 | apk.length() - offsetAfterEocdCdOffsetField), |
| 287 | MMAP_REGION_SIZE_BYTES); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 288 | |
Victor Hsieh | 3a0032f | 2018-02-20 15:22:28 -0800 | [diff] [blame] | 289 | // 5. Pad 0s up to the nearest 4096-byte block before hashing. |
| 290 | int lastIncompleteChunkSize = (int) (apk.length() % CHUNK_SIZE_BYTES); |
| 291 | if (lastIncompleteChunkSize != 0) { |
| 292 | digester.consume(ByteBuffer.allocate(CHUNK_SIZE_BYTES - lastIncompleteChunkSize)); |
| 293 | } |
| 294 | digester.assertEmptyBuffer(); |
| 295 | |
| 296 | // 6. Fill up the rest of buffer with 0s. |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 297 | digester.fillUpLastOutputChunk(); |
| 298 | } |
| 299 | |
| 300 | private static byte[] generateApkVerityTree(RandomAccessFile apk, SignatureInfo signatureInfo, |
| 301 | byte[] salt, int[] levelOffset, ByteBuffer output) |
Victor Hsieh | def64f2 | 2017-11-08 10:25:11 -0800 | [diff] [blame] | 302 | throws IOException, NoSuchAlgorithmException, DigestException { |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 303 | // 1. Digest the apk to generate the leaf level hashes. |
| 304 | generateApkVerityDigestAtLeafLevel(apk, signatureInfo, salt, slice(output, |
| 305 | levelOffset[levelOffset.length - 2], levelOffset[levelOffset.length - 1])); |
| 306 | |
| 307 | // 2. Digest the lower level hashes bottom up. |
| 308 | for (int level = levelOffset.length - 3; level >= 0; level--) { |
| 309 | ByteBuffer inputBuffer = slice(output, levelOffset[level + 1], levelOffset[level + 2]); |
| 310 | ByteBuffer outputBuffer = slice(output, levelOffset[level], levelOffset[level + 1]); |
| 311 | |
| 312 | DataSource source = new ByteBufferDataSource(inputBuffer); |
| 313 | BufferedDigester digester = new BufferedDigester(salt, outputBuffer); |
| 314 | consumeByChunk(digester, source, CHUNK_SIZE_BYTES); |
Victor Hsieh | 3a0032f | 2018-02-20 15:22:28 -0800 | [diff] [blame] | 315 | digester.assertEmptyBuffer(); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 316 | digester.fillUpLastOutputChunk(); |
| 317 | } |
| 318 | |
| 319 | // 3. Digest the first block (i.e. first level) to generate the root hash. |
| 320 | byte[] rootHash = new byte[DIGEST_SIZE_BYTES]; |
| 321 | BufferedDigester digester = new BufferedDigester(salt, ByteBuffer.wrap(rootHash)); |
| 322 | digester.consume(slice(output, 0, CHUNK_SIZE_BYTES)); |
Victor Hsieh | 3a0032f | 2018-02-20 15:22:28 -0800 | [diff] [blame] | 323 | digester.assertEmptyBuffer(); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 324 | return rootHash; |
| 325 | } |
| 326 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 327 | private static ByteBuffer generateFsverityHeader(ByteBuffer buffer, long fileSize, int depth, |
| 328 | byte[] salt) { |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 329 | if (salt.length != 8) { |
| 330 | throw new IllegalArgumentException("salt is not 8 bytes long"); |
| 331 | } |
| 332 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 333 | // TODO(b/30972906): update the reference when there is a better one in public. |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 334 | buffer.put("TrueBrew".getBytes()); // magic |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 335 | |
Victor Hsieh | 2c8fbd6 | 2018-01-25 16:08:58 -0800 | [diff] [blame] | 336 | buffer.put((byte) 1); // major version |
| 337 | buffer.put((byte) 0); // minor version |
| 338 | buffer.put((byte) 12); // log2(block-size): log2(4096) |
| 339 | buffer.put((byte) 7); // log2(leaves-per-node): log2(4096 / 32) |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 340 | |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 341 | buffer.putShort((short) 1); // meta algorithm, SHA256 == 1 |
| 342 | buffer.putShort((short) 1); // data algorithm, SHA256 == 1 |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 343 | |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 344 | buffer.putInt(0); // flags |
Victor Hsieh | d48e954 | 2018-01-24 12:06:43 -0800 | [diff] [blame] | 345 | buffer.putInt(0); // reserved |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 346 | |
Victor Hsieh | d48e954 | 2018-01-24 12:06:43 -0800 | [diff] [blame] | 347 | buffer.putLong(fileSize); // original file size |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 348 | |
Victor Hsieh | 4cf7382 | 2018-04-23 14:43:19 -0700 | [diff] [blame] | 349 | buffer.put((byte) 2); // authenticated extension count |
| 350 | buffer.put((byte) 0); // unauthenticated extension count |
Victor Hsieh | d48e954 | 2018-01-24 12:06:43 -0800 | [diff] [blame] | 351 | buffer.put(salt); // salt (8 bytes) |
Victor Hsieh | 2120323 | 2018-01-29 15:10:56 -0800 | [diff] [blame] | 352 | skip(buffer, 22); // reserved |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 353 | |
Victor Hsieh | 2120323 | 2018-01-29 15:10:56 -0800 | [diff] [blame] | 354 | buffer.flip(); |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 355 | return buffer; |
| 356 | } |
| 357 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 358 | private static ByteBuffer generateFsverityExtensions(ByteBuffer buffer, long signingBlockOffset, |
| 359 | long signingBlockSize, long eocdOffset) { |
| 360 | // Snapshot of the FSVerity structs (subject to change once upstreamed). |
| 361 | // |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 362 | // struct fsverity_extension_elide { |
| 363 | // __le64 offset; |
| 364 | // __le64 length; |
| 365 | // } |
| 366 | // |
| 367 | // struct fsverity_extension_patch { |
| 368 | // __le64 offset; |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 369 | // u8 databytes[]; |
| 370 | // }; |
| 371 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 372 | final int kSizeOfFsverityExtensionHeader = 8; |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 373 | final int kExtensionSizeAlignment = 8; |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 374 | |
| 375 | { |
| 376 | // struct fsverity_extension #1 |
| 377 | final int kSizeOfFsverityElidedExtension = 16; |
| 378 | |
Victor Hsieh | 4cf7382 | 2018-04-23 14:43:19 -0700 | [diff] [blame] | 379 | // First field is total size of extension, padded to 64-bit alignment |
| 380 | buffer.putInt(kSizeOfFsverityExtensionHeader + kSizeOfFsverityElidedExtension); |
| 381 | buffer.putShort((short) 1); // ID of elide extension |
| 382 | skip(buffer, 2); // reserved |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 383 | |
| 384 | // struct fsverity_extension_elide |
| 385 | buffer.putLong(signingBlockOffset); |
| 386 | buffer.putLong(signingBlockSize); |
| 387 | } |
| 388 | |
| 389 | { |
| 390 | // struct fsverity_extension #2 |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 391 | final int kTotalSize = kSizeOfFsverityExtensionHeader |
| 392 | + 8 // offset size |
| 393 | + ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_SIZE; |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 394 | |
Victor Hsieh | 4cf7382 | 2018-04-23 14:43:19 -0700 | [diff] [blame] | 395 | buffer.putInt(kTotalSize); // Total size of extension, padded to 64-bit alignment |
| 396 | buffer.putShort((short) 2); // ID of patch extension |
| 397 | skip(buffer, 2); // reserved |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 398 | |
| 399 | // struct fsverity_extension_patch |
Victor Hsieh | cccad19 | 2018-03-19 15:57:02 -0700 | [diff] [blame] | 400 | buffer.putLong(eocdOffset + ZIP_EOCD_CENTRAL_DIR_OFFSET_FIELD_OFFSET); // offset |
| 401 | buffer.putInt(Math.toIntExact(signingBlockOffset)); // databytes |
| 402 | |
| 403 | // The extension needs to be 0-padded at the end, since the length may not be multiple |
| 404 | // of 8. |
| 405 | int kPadding = kExtensionSizeAlignment - kTotalSize % kExtensionSizeAlignment; |
| 406 | if (kPadding == kExtensionSizeAlignment) { |
| 407 | kPadding = 0; |
| 408 | } |
Victor Hsieh | 4cf7382 | 2018-04-23 14:43:19 -0700 | [diff] [blame] | 409 | skip(buffer, kPadding); // padding |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 410 | } |
| 411 | |
Victor Hsieh | 2120323 | 2018-01-29 15:10:56 -0800 | [diff] [blame] | 412 | buffer.flip(); |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 413 | return buffer; |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 414 | } |
| 415 | |
| 416 | /** |
| 417 | * Returns an array of summed area table of level size in the verity tree. In other words, the |
| 418 | * returned array is offset of each level in the verity tree file format, plus an additional |
| 419 | * offset of the next non-existing level (i.e. end of the last level + 1). Thus the array size |
| 420 | * is level + 1. Thus, the returned array is guarantee to have at least 2 elements. |
| 421 | */ |
| 422 | private static int[] calculateVerityLevelOffset(long fileSize) { |
| 423 | ArrayList<Long> levelSize = new ArrayList<>(); |
| 424 | while (true) { |
| 425 | long levelDigestSize = divideRoundup(fileSize, CHUNK_SIZE_BYTES) * DIGEST_SIZE_BYTES; |
| 426 | long chunksSize = CHUNK_SIZE_BYTES * divideRoundup(levelDigestSize, CHUNK_SIZE_BYTES); |
| 427 | levelSize.add(chunksSize); |
| 428 | if (levelDigestSize <= CHUNK_SIZE_BYTES) { |
| 429 | break; |
| 430 | } |
| 431 | fileSize = levelDigestSize; |
| 432 | } |
| 433 | |
| 434 | // Reverse and convert to summed area table. |
| 435 | int[] levelOffset = new int[levelSize.size() + 1]; |
| 436 | levelOffset[0] = 0; |
| 437 | for (int i = 0; i < levelSize.size(); i++) { |
| 438 | // We don't support verity tree if it is larger then Integer.MAX_VALUE. |
| 439 | levelOffset[i + 1] = levelOffset[i] |
| 440 | + Math.toIntExact(levelSize.get(levelSize.size() - i - 1)); |
| 441 | } |
| 442 | return levelOffset; |
| 443 | } |
| 444 | |
| 445 | private static void assertSigningBlockAlignedAndHasFullPages(SignatureInfo signatureInfo) { |
| 446 | if (signatureInfo.apkSigningBlockOffset % CHUNK_SIZE_BYTES != 0) { |
| 447 | throw new IllegalArgumentException( |
| 448 | "APK Signing Block does not start at the page boundary: " |
| 449 | + signatureInfo.apkSigningBlockOffset); |
| 450 | } |
| 451 | |
| 452 | if ((signatureInfo.centralDirOffset - signatureInfo.apkSigningBlockOffset) |
| 453 | % CHUNK_SIZE_BYTES != 0) { |
| 454 | throw new IllegalArgumentException( |
| 455 | "Size of APK Signing Block is not a multiple of 4096: " |
| 456 | + (signatureInfo.centralDirOffset - signatureInfo.apkSigningBlockOffset)); |
| 457 | } |
| 458 | } |
| 459 | |
| 460 | /** Returns a slice of the buffer which shares content with the provided buffer. */ |
| 461 | private static ByteBuffer slice(ByteBuffer buffer, int begin, int end) { |
| 462 | ByteBuffer b = buffer.duplicate(); |
| 463 | b.position(0); // to ensure position <= limit invariant. |
| 464 | b.limit(end); |
| 465 | b.position(begin); |
| 466 | return b.slice(); |
| 467 | } |
| 468 | |
Victor Hsieh | 3051d78 | 2018-01-12 08:28:03 -0800 | [diff] [blame] | 469 | /** Skip the {@code ByteBuffer} position by {@code bytes}. */ |
| 470 | private static void skip(ByteBuffer buffer, int bytes) { |
| 471 | buffer.position(buffer.position() + bytes); |
| 472 | } |
| 473 | |
Victor Hsieh | 3271d04 | 2017-10-24 15:46:32 -0700 | [diff] [blame] | 474 | /** Divides a number and round up to the closest integer. */ |
| 475 | private static long divideRoundup(long dividend, long divisor) { |
| 476 | return (dividend + divisor - 1) / divisor; |
| 477 | } |
| 478 | } |