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Verify Secret correctness as part of loading.

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Improve tests
This commit is contained in:
Christopher O'Grady 2025-01-08 22:12:03 -05:00
parent f4974c8705
commit 9871f0420f
5 changed files with 163 additions and 32 deletions
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5
app/src/main/java/com/github/nacabaro/vbhelper/source/ApkSecretsImporter.kt
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@ -3,13 +3,14 @@ package com.github.nacabaro.vbhelper.source
import java.io.InputStream
import java.util.zip.ZipInputStream
class ApkSecretsImporter(private val dexFileSecretsImporter: DexFileSecretsImporter = DexFileSecretsImporter()) {
class ApkSecretsImporter(private val dexFileSecretsImporter: SecretsImporter = DexFileSecretsImporter()): SecretsImporter {
companion object {
const val DEX_FILE = "classes.dex"
}
fun importSecrets(inputStream: InputStream): Map<UShort, Secrets> {
// importSecrets imports the secrets from the apk input stream, and validates them.
override fun importSecrets(inputStream: InputStream): Map<UShort, Secrets> {
ZipInputStream(inputStream).use { zip ->
var zipEntry = zip.nextEntry
while(zipEntry != null) {

52
app/src/main/java/com/github/nacabaro/vbhelper/source/DexFileSecretsImporter.kt
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@ -5,9 +5,10 @@ import java.io.InputStream
import java.nio.ByteBuffer
import java.nio.ByteOrder
import java.nio.charset.StandardCharsets
import java.security.InvalidKeyException
class DexFileSecretsImporter {
class DexFileSecretsImporter: SecretsImporter {
companion object {
const val VBDM_SUBSTITUTION_CIPHER_IDX = 1080145
@ -20,20 +21,31 @@ class DexFileSecretsImporter {
const val BE_HMAC_KEY_1_IDX = 1580157
const val BE_HMAC_KEY_2_IDX = 1593759
const val AES_KEY_IDX = 1277527
val TEST_TAG = byteArrayOf(0x34, 0x01, 0x10, 0xff.toByte(), 0xf5.toByte(), 0x00, 0xa2.toByte())
const val BE_TEST_TAG_PASSWORD = "be29a87e"
const val VBDM_TEST_TAG_PASSWORD = "6ea33673"
const val VBC_TEST_TAG_PASSWORD = "a71dfb22"
}
fun importSecrets(inputStream: InputStream): Map<UShort, Secrets> {
override fun importSecrets(inputStream: InputStream): Map<UShort, Secrets> {
val deviceToSecrets = readSecrets(inputStream)
verifySecretCorrectness(deviceToSecrets)
return deviceToSecrets
}
private fun readSecrets(inputStream: InputStream): Map<UShort, Secrets> {
val dexFile = inputStream.readBytes()
val byteOrder = ByteOrder.BIG_ENDIAN
val vbdmSubstitutionCipher = dexFile.sliceArray(VBDM_SUBSTITUTION_CIPHER_IDX until VBDM_SUBSTITUTION_CIPHER_IDX+(16*4)).toIntArray(byteOrder)
val beSubstitutionCipher = dexFile.sliceArray(BE_SUBSTITUTION_CIPHER_IDX until BE_SUBSTITUTION_CIPHER_IDX+(16*4)).toIntArray(byteOrder)
val aesKey = dexFile.sliceArray(AES_KEY_IDX until AES_KEY_IDX+24).toString(StandardCharsets.UTF_8)
val cryptographicTransformerByDevices = mapOf(
val secretsByDevices = mapOf(
Pair(DeviceType.VitalSeriesDeviceType, buildSecrets(dexFile, VBDM_HMAC_KEY_1_IDX, VBDM_HMAC_KEY_2_IDX, aesKey, vbdmSubstitutionCipher)),
Pair(DeviceType.VitalBraceletBEDeviceType, buildSecrets(dexFile, BE_HMAC_KEY_1_IDX, BE_HMAC_KEY_2_IDX, aesKey, beSubstitutionCipher)),
Pair(DeviceType.VitalCharactersDeviceType, buildSecrets(dexFile, VBC_HMAC_KEY_1_IDX, VBC_HMAC_KEY_2_IDX, aesKey, vbdmSubstitutionCipher)),
)
return cryptographicTransformerByDevices
return secretsByDevices
}
private fun buildSecrets(dexFile: ByteArray, hmacKeyIdx1: Int, hmacKeyIdx2: Int, aesKey: String, substitutionCipher: IntArray): Secrets {
@ -41,6 +53,38 @@ class DexFileSecretsImporter {
val hmacKey2 = dexFile.sliceArray(hmacKeyIdx2 until hmacKeyIdx2+24).toString(StandardCharsets.UTF_8)
return Secrets(hmacKey1, hmacKey2, aesKey, substitutionCipher)
}
@OptIn(ExperimentalStdlibApi::class)
private fun verifySecretCorrectness(deviceToSecrets: Map<UShort, Secrets>) {
for (keyValue in deviceToSecrets) {
when(keyValue.key) {
DeviceType.VitalBraceletBEDeviceType -> {
val result = keyValue.value.toCryptographicTransformer().createNfcPassword(
TEST_TAG
)
if( result.toHexString() != BE_TEST_TAG_PASSWORD) {
throw InvalidKeyException("Secrets were loaded, but were unsuccessful at generating the test password: ${result.toHexString()}")
}
}
DeviceType.VitalCharactersDeviceType -> {
val result = keyValue.value.toCryptographicTransformer().createNfcPassword(
TEST_TAG
)
if( result.toHexString() != VBC_TEST_TAG_PASSWORD) {
throw InvalidKeyException("Secrets were loaded, but were unsuccessful at generating the test password: ${result.toHexString()}")
}
}
DeviceType.VitalSeriesDeviceType -> {
val result = keyValue.value.toCryptographicTransformer().createNfcPassword(
TEST_TAG
)
if( result.toHexString() != VBDM_TEST_TAG_PASSWORD) {
throw InvalidKeyException("Secrets were loaded, but were unsuccessful at generating the test password: ${result.toHexString()}")
}
}
}
}
}
}
fun ByteArray.toIntArray(byteOrder: ByteOrder): IntArray {

7
app/src/main/java/com/github/nacabaro/vbhelper/source/SecretsImporter.kt Normal file
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@ -0,0 +1,7 @@
package com.github.nacabaro.vbhelper.source
import java.io.InputStream
fun interface SecretsImporter {
fun importSecrets(inputStream: InputStream): Map<UShort, Secrets>
}

67
app/src/test/java/com/github/nacabaro/vbhelper/source/ApkSecretsImporterTest.kt
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@ -3,14 +3,63 @@ package com.github.nacabaro.vbhelper.source
import com.github.cfogrady.vbnfc.data.DeviceType
import org.junit.Assert
import org.junit.Test
import java.io.ByteArrayInputStream
import java.io.ByteArrayOutputStream
import java.io.File
import java.net.URL
import java.nio.charset.StandardCharsets
import java.util.zip.ZipEntry
import java.util.zip.ZipOutputStream
class ApkSecretsImporterTest {
@OptIn(ExperimentalStdlibApi::class)
@Test
fun importSecretsTest() {
val apkSecretsImporter = ApkSecretsImporter()
fun testThatRealImportSecretsHasAllDeviceTypes() {
val apkFileSecretsImporter = ApkSecretsImporter()
val url = getAndAssertApkFile()
val file = File(url.path)
file.inputStream().use {
val deviceIdToSecrets = apkFileSecretsImporter.importSecrets(it)
Assert.assertNotNull("BE Device Type", deviceIdToSecrets[DeviceType.VitalBraceletBEDeviceType])
Assert.assertNotNull("VBDM Device Type", deviceIdToSecrets[DeviceType.VitalSeriesDeviceType])
Assert.assertNotNull("VBC Device Type", deviceIdToSecrets[DeviceType.VitalCharactersDeviceType])
}
}
@Test
fun testThatApkSecretsImporterCallsDexSecretImporterOnDexFile() {
val expectedDexContents = byteArrayOf(0, 1, 2, 3, 4, 5, 6, 7, 6, 5, 4, 3, 2, 1)
var foundFile = false
val apkFileSecretsImporter = ApkSecretsImporter {
val inputStreamContents = it.readAllBytes()
Assert.assertTrue("Unexpected file contents received by DexSecretsImporter", inputStreamContents.contentEquals(expectedDexContents))
foundFile = true
emptyMap()
}
val apkBytes = constructTestApk(expectedDexContents)
ByteArrayInputStream(apkBytes).use {
apkFileSecretsImporter.importSecrets(it)
}
Assert.assertTrue("${ApkSecretsImporter.DEX_FILE} not found", foundFile)
}
fun constructTestApk(dexContents: ByteArray): ByteArray {
val byteArrayOutputStream = ByteArrayOutputStream()
ZipOutputStream(byteArrayOutputStream).use { zipOutputStream ->
zipOutputStream.putNextEntry(ZipEntry("dummy.txt"))
zipOutputStream.write("This is a text file".toByteArray(StandardCharsets.UTF_8))
zipOutputStream.putNextEntry(ZipEntry("AndroidManifest.xml"))
zipOutputStream.write("Malformed xml!".toByteArray(StandardCharsets.UTF_8))
zipOutputStream.putNextEntry(ZipEntry("assets/"))
zipOutputStream.putNextEntry(ZipEntry("assets/bad.assets"))
zipOutputStream.write("Malformed asset!".toByteArray(StandardCharsets.UTF_8))
zipOutputStream.putNextEntry(ZipEntry(ApkSecretsImporter.DEX_FILE))
zipOutputStream.write(dexContents)
}
return byteArrayOutputStream.toByteArray()
}
private fun getAndAssertApkFile(): URL {
val url = javaClass.getResource("com.bandai.vitalbraceletarena.apk")
if(url == null) {
Assert.assertTrue("""
@ -19,16 +68,6 @@ class ApkSecretsImporterTest {
should never be checked in and should be on the .gitignore.
""".trimIndent(), false)
}
val file = File(url.path)
val testTagId = byteArrayOf(0x04, 0x40, 0xaf.toByte(), 0xa2.toByte(), 0xee.toByte(), 0x0f, 0x90.toByte())
file.inputStream().use {
val deviceIdToCryptographicTransformer = apkSecretsImporter.importSecrets(it)
var password = deviceIdToCryptographicTransformer[DeviceType.VitalBraceletBEDeviceType]!!.toCryptographicTransformer().createNfcPassword(testTagId)
Assert.assertEquals("5651b1c8", password.toHexString())
password = deviceIdToCryptographicTransformer[DeviceType.VitalSeriesDeviceType]!!.toCryptographicTransformer().createNfcPassword(testTagId)
Assert.assertEquals("dd2ceb84", password.toHexString())
password = deviceIdToCryptographicTransformer[DeviceType.VitalCharactersDeviceType]!!.toCryptographicTransformer().createNfcPassword(testTagId)
Assert.assertEquals("515e0c12", password.toHexString())
}
return url!!
}
}

64
app/src/test/java/com/github/nacabaro/vbhelper/source/DexFileSecretsImporterTest.kt
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@ -3,14 +3,44 @@ package com.github.nacabaro.vbhelper.source
import com.github.cfogrady.vbnfc.data.DeviceType
import org.junit.Assert
import org.junit.Test
import java.io.ByteArrayInputStream
import java.io.File
import java.net.URL
import java.nio.ByteOrder
import java.security.InvalidKeyException
class DexFileSecretsImporterTest {
@OptIn(ExperimentalStdlibApi::class)
@Test
fun importSecretsTest() {
fun testThatImportSecretsHasAllDeviceTypes() {
val dexFileSecretsImporter = DexFileSecretsImporter()
val url = getAndAssertClassesDexFile()
val file = File(url.path)
file.inputStream().use {
val deviceIdToSecrets = dexFileSecretsImporter.importSecrets(it)
Assert.assertNotNull("BE Device Type", deviceIdToSecrets[DeviceType.VitalBraceletBEDeviceType])
Assert.assertNotNull("VBDM Device Type", deviceIdToSecrets[DeviceType.VitalSeriesDeviceType])
Assert.assertNotNull("VBC Device Type", deviceIdToSecrets[DeviceType.VitalCharactersDeviceType])
}
}
@Test
fun testThatImportWrongSecretsThrows() {
val dexFileSecretsImporter = DexFileSecretsImporter()
val url = getAndAssertClassesDexFile()
val file = File(url.path)
val content = file.readBytes()
val badCipher = intArrayOf(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15).toByteArray(ByteOrder.BIG_ENDIAN)
badCipher.copyInto(content, DexFileSecretsImporter.BE_SUBSTITUTION_CIPHER_IDX)
ByteArrayInputStream(content).use {
Assert.assertThrows("Secrets are validated", InvalidKeyException::class.java) {
dexFileSecretsImporter.importSecrets(it)
}
}
}
private fun getAndAssertClassesDexFile(): URL {
val url = javaClass.getResource("classes.dex")
if(url == null) {
Assert.assertTrue("""
@ -19,16 +49,26 @@ class DexFileSecretsImporterTest {
checked in and should be on the .gitignore.
""".trimIndent(), false)
}
val file = File(url.path)
val testTagId = byteArrayOf(0x04, 0x40, 0xaf.toByte(), 0xa2.toByte(), 0xee.toByte(), 0x0f, 0x90.toByte())
file.inputStream().use {
val deviceIdToCryptographicTransformer = dexFileSecretsImporter.importSecrets(it)
var password = deviceIdToCryptographicTransformer[DeviceType.VitalBraceletBEDeviceType]!!.toCryptographicTransformer().createNfcPassword(testTagId)
Assert.assertEquals("5651b1c8", password.toHexString())
password = deviceIdToCryptographicTransformer[DeviceType.VitalSeriesDeviceType]!!.toCryptographicTransformer().createNfcPassword(testTagId)
Assert.assertEquals("dd2ceb84", password.toHexString())
password = deviceIdToCryptographicTransformer[DeviceType.VitalCharactersDeviceType]!!.toCryptographicTransformer().createNfcPassword(testTagId)
Assert.assertEquals("515e0c12", password.toHexString())
return url!!
}
}
fun IntArray.toByteArray(byteOrder: ByteOrder = ByteOrder.nativeOrder()): ByteArray {
val byteArray = ByteArray(this.size*4)
for(i in this.indices) {
val byteArrayIndex = i*4
this[i].toByteArray(byteArray, byteArrayIndex, byteOrder)
}
return byteArray
}
fun Int.toByteArray(bytes: ByteArray, dstIndex: Int, byteOrder: ByteOrder = ByteOrder.nativeOrder()) {
val asUInt = this.toUInt()
for(i in 0 until 4) {
if(byteOrder == ByteOrder.LITTLE_ENDIAN) {
bytes[i+dstIndex] = ((asUInt shr 8*i) and 255u).toByte()
} else {
bytes[(3-i) + dstIndex] = ((asUInt shr 8*i) and 255u).toByte()
}
}
}