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feat(attestation): align attestation extension and cert generation with AOSP

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KeyMintAttestation now carries all 17 enforcement tags that AOSP's
authorize_create and buildKeyDescription paths expect. AttestationBuilder
populates BLOCK_MODE as SET OF INTEGER, gates version-guarded tags
(RSA_OAEP_MGF_DIGEST >=100, ROLLBACK_RESISTANCE >=3, EARLY_BOOT_ONLY >=4),
computes INCLUDE_UNIQUE_ID via HMAC-SHA256 per KeyMint HAL spec, and
gates AAID on challenge presence.

CertificateGenerator uses AOSP cert validity defaults (epoch notBefore,
9999-12-31 notAfter), returns ServiceSpecificException(-75) for missing
keybox, and adds RSA exponent null safety.
This commit is contained in:
Enginex0
2026-03-19 07:32:53 +01:00
parent 4a103c9231
commit 468b6f5121
4 changed files with 258 additions and 68 deletions
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app/src/main/java/org/matrix/TEESimulator/attestation/AttestationBuilder.kt
+176 -45
View File
@@ -2,8 +2,11 @@ package org.matrix.TEESimulator.attestation
import android.content.pm.PackageManager
import android.os.Build
import java.nio.ByteBuffer
import java.nio.charset.StandardCharsets
import java.security.MessageDigest
import javax.crypto.Mac
import javax.crypto.spec.SecretKeySpec
import org.bouncycastle.asn1.ASN1Boolean
import org.bouncycastle.asn1.ASN1Encodable
import org.bouncycastle.asn1.ASN1Enumerated
@@ -127,33 +130,59 @@ object AttestationBuilder {
return properties
}
/** Constructs the main `KeyDescription` sequence, which is the core of the attestation. */
private fun buildKeyDescription(
params: KeyMintAttestation,
uid: Int,
securityLevel: Int,
): ASN1Sequence {
val creationTime = System.currentTimeMillis()
val teeEnforced = buildTeeEnforcedList(params, uid, securityLevel)
val softwareEnforced = buildSoftwareEnforcedList(uid, securityLevel)
val softwareEnforced = buildSoftwareEnforcedList(params, uid, securityLevel, creationTime)
val uniqueId =
if (params.includeUniqueId == true && params.attestationChallenge != null) {
computeUniqueId(creationTime, createApplicationId(uid).octets)
} else {
ByteArray(0)
}
val fields =
arrayOf(
ASN1Integer(
AndroidDeviceUtils.getAttestVersion(securityLevel).toLong()
), // attestationVersion
ASN1Enumerated(securityLevel), // attestationSecurityLevel
ASN1Integer(
AndroidDeviceUtils.getKeymasterVersion(securityLevel).toLong()
), // keymasterVersion
ASN1Enumerated(securityLevel), // keymasterSecurityLevel
DEROctetString(params.attestationChallenge ?: ByteArray(0)), // attestationChallenge
DEROctetString(ByteArray(0)), // uniqueId
ASN1Integer(AndroidDeviceUtils.getAttestVersion(securityLevel).toLong()),
ASN1Enumerated(securityLevel),
ASN1Integer(AndroidDeviceUtils.getKeymasterVersion(securityLevel).toLong()),
ASN1Enumerated(securityLevel),
DEROctetString(params.attestationChallenge ?: ByteArray(0)),
DEROctetString(uniqueId),
softwareEnforced,
teeEnforced,
)
return DERSequence(fields)
}
private fun computeUniqueId(creationTimeMs: Long, aaidDer: ByteArray): ByteArray {
val temporalCounter = creationTimeMs / 2592000000L
val message =
ByteBuffer.allocate(8 + aaidDer.size + 1)
.putLong(temporalCounter)
.put(aaidDer)
.put(0x00)
.array()
val mac = Mac.getInstance("HmacSHA256")
mac.init(SecretKeySpec(hbk, "HmacSHA256"))
return mac.doFinal(message).copyOf(16)
}
private val hbk: ByteArray by lazy {
val file = java.io.File(ConfigurationManager.CONFIG_PATH, "hbk")
if (file.exists() && file.length() == 32L) {
file.readBytes()
} else {
SystemLogger.warning("hbk not found, generating ephemeral HBK.")
ByteArray(32).also { java.security.SecureRandom().nextBytes(it) }
}
}
/** Builds the `TeeEnforced` authorization list. These are properties the TEE "guarantees". */
private fun buildTeeEnforcedList(
params: KeyMintAttestation,
@@ -194,6 +223,16 @@ object AttestationBuilder {
)
}
if (params.blockMode.isNotEmpty()) {
list.add(
DERTaggedObject(
true,
AttestationConstants.TAG_BLOCK_MODE,
DERSet(params.blockMode.map { ASN1Integer(it.toLong()) }.toTypedArray()),
)
)
}
if (params.padding.isNotEmpty()) {
list.add(
DERTaggedObject(
@@ -214,14 +253,61 @@ object AttestationBuilder {
)
}
val attestVersion = AndroidDeviceUtils.getAttestVersion(securityLevel)
if (params.rsaOaepMgfDigest.isNotEmpty() && attestVersion >= 100) {
list.add(
DERTaggedObject(
true,
AttestationConstants.TAG_RSA_OAEP_MGF_DIGEST,
DERSet(params.rsaOaepMgfDigest.map { ASN1Integer(it.toLong()) }.toTypedArray()),
)
)
}
if (params.rollbackResistance == true && attestVersion >= 3) {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_ROLLBACK_RESISTANCE, DERNull.INSTANCE)
)
}
if (params.earlyBootOnly == true && attestVersion >= 4) {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_EARLY_BOOT_ONLY, DERNull.INSTANCE)
)
}
if (params.noAuthRequired == true) {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_NO_AUTH_REQUIRED, DERNull.INSTANCE)
)
}
if (params.allowWhileOnBody == true) {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_ALLOW_WHILE_ON_BODY, DERNull.INSTANCE)
)
}
if (params.trustedUserPresenceRequired == true && attestVersion >= 3) {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_TRUSTED_USER_PRESENCE_REQUIRED, DERNull.INSTANCE)
)
}
if (params.trustedConfirmationRequired == true && attestVersion >= 3) {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_TRUSTED_CONFIRMATION_REQUIRED, DERNull.INSTANCE)
)
}
list.addAll(
listOf(
DERTaggedObject(true, AttestationConstants.TAG_NO_AUTH_REQUIRED, DERNull.INSTANCE),
DERTaggedObject(
true,
AttestationConstants.TAG_ORIGIN,
ASN1Integer(0L),
), // KeyOrigin.GENERATED
ASN1Integer((params.origin ?: 0).toLong()),
),
DERTaggedObject(
true,
AttestationConstants.TAG_ROOT_OF_TRUST,
@@ -325,20 +411,32 @@ object AttestationBuilder {
* Builds the `SoftwareEnforced` authorization list. These are properties guaranteed by
* Keystore.
*/
private fun buildSoftwareEnforcedList(uid: Int, securityLevel: Int): DERSequence {
val list =
mutableListOf<ASN1Encodable>(
DERTaggedObject(
true,
AttestationConstants.TAG_CREATION_DATETIME,
ASN1Integer(System.currentTimeMillis()),
),
private fun buildSoftwareEnforcedList(
params: KeyMintAttestation,
uid: Int,
securityLevel: Int,
creationTimeMs: Long = System.currentTimeMillis(),
): DERSequence {
val list = mutableListOf<ASN1Encodable>()
list.add(
DERTaggedObject(
true,
AttestationConstants.TAG_CREATION_DATETIME,
ASN1Integer(creationTimeMs),
)
)
if (params.attestationChallenge != null) {
list.add(
DERTaggedObject(
true,
AttestationConstants.TAG_ATTESTATION_APPLICATION_ID,
createApplicationId(uid),
),
)
)
}
if (AndroidDeviceUtils.getAttestVersion(securityLevel) >= 400) {
list.add(
DERTaggedObject(
@@ -348,7 +446,34 @@ object AttestationBuilder {
)
)
}
return DERSequence(list.toTypedArray())
params.activeDateTime?.let {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_ACTIVE_DATETIME, ASN1Integer(it.time))
)
}
params.originationExpireDateTime?.let {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_ORIGINATION_EXPIRE_DATETIME, ASN1Integer(it.time))
)
}
params.usageExpireDateTime?.let {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_USAGE_EXPIRE_DATETIME, ASN1Integer(it.time))
)
}
params.usageCountLimit?.let {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_USAGE_COUNT_LIMIT, ASN1Integer(it.toLong()))
)
}
if (params.unlockedDeviceRequired == true) {
list.add(
DERTaggedObject(true, AttestationConstants.TAG_UNLOCKED_DEVICE_REQUIRED, DERNull.INSTANCE)
)
}
return DERSequence(list.sortedBy { (it as DERTaggedObject).tagNo }.toTypedArray())
}
/**
@@ -376,6 +501,11 @@ object AttestationBuilder {
*/
@Throws(Throwable::class)
internal fun createApplicationId(uid: Int): DEROctetString {
val appUid = uid % 100000
if (appUid == 0 || appUid == 1000) {
return buildApplicationIdDer(listOf("AndroidSystem" to 1L), emptySet())
}
val pm =
ConfigurationManager.getPackageManager()
?: throw IllegalStateException("PackageManager not found!")
@@ -383,12 +513,11 @@ object AttestationBuilder {
pm.getPackagesForUid(uid) ?: throw IllegalStateException("No packages for UID $uid")
val sha256 = MessageDigest.getInstance("SHA-256")
val packageInfoList = mutableListOf<DERSequence>()
val packageInfoList = mutableListOf<Pair<String, Long>>()
val signatureDigests = mutableSetOf<Digest>()
// Process all packages associated with the UID in a single loop.
val userId = uid / 100000
packages.forEach { packageName ->
val userId = uid / 100000
val packageInfo =
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
pm.getPackageInfo(
@@ -401,34 +530,36 @@ object AttestationBuilder {
pm.getPackageInfo(packageName, PackageManager.GET_SIGNING_CERTIFICATES, userId)
}
// Add package information (name and version code) to our list.
packageInfoList.add(
DERSequence(
arrayOf(
DEROctetString(packageInfo.packageName.toByteArray(StandardCharsets.UTF_8)),
ASN1Integer(packageInfo.longVersionCode),
)
)
)
packageInfoList.add(packageInfo.packageName to packageInfo.longVersionCode)
// Collect unique signature digests from the signing history.
packageInfo.signingInfo?.signingCertificateHistory?.forEach { signature ->
val digest = sha256.digest(signature.toByteArray())
signatureDigests.add(Digest(digest))
signatureDigests.add(Digest(sha256.digest(signature.toByteArray())))
}
}
// The application ID is a sequence of two sets:
// 1. A set of package information (name and version).
// 2. A set of SHA-256 digests of the signing certificates.
return buildApplicationIdDer(packageInfoList, signatureDigests)
}
private fun buildApplicationIdDer(
packages: List<Pair<String, Long>>,
digests: Set<Digest>,
): DEROctetString {
val packageInfoList =
packages.map { (name, version) ->
DERSequence(
arrayOf(
DEROctetString(name.toByteArray(StandardCharsets.UTF_8)),
ASN1Integer(version),
)
)
}
val applicationIdSequence =
DERSequence(
arrayOf(
DERSet(packageInfoList.toTypedArray()),
DERSet(signatureDigests.map { DEROctetString(it.digest) }.toTypedArray()),
DERSet(digests.map { DEROctetString(it.digest) }.toTypedArray()),
)
)
return DEROctetString(applicationIdSequence.encoded)
}
}
app/src/main/java/org/matrix/TEESimulator/attestation/AttestationConstants.kt
+6
View File
@@ -44,9 +44,11 @@ object AttestationConstants {
// --- Key Lifetime and Usage Control ---
const val TAG_ROLLBACK_RESISTANCE = 303
const val TAG_EARLY_BOOT_ONLY = 305
const val TAG_ACTIVE_DATETIME = 400
const val TAG_ORIGINATION_EXPIRE_DATETIME = 401
const val TAG_USAGE_EXPIRE_DATETIME = 402
const val TAG_MAX_BOOT_LEVEL = 403
const val TAG_MAX_USES_PER_BOOT = 404
const val TAG_USAGE_COUNT_LIMIT = 405
@@ -56,6 +58,10 @@ object AttestationConstants {
const val TAG_NO_AUTH_REQUIRED = 503
const val TAG_USER_AUTH_TYPE = 504
const val TAG_AUTH_TIMEOUT = 505
const val TAG_ALLOW_WHILE_ON_BODY = 506
const val TAG_TRUSTED_USER_PRESENCE_REQUIRED = 507
const val TAG_TRUSTED_CONFIRMATION_REQUIRED = 508
const val TAG_UNLOCKED_DEVICE_REQUIRED = 509
// --- Attestation and Application Info ---
const val TAG_APPLICATION_ID = 601
app/src/main/java/org/matrix/TEESimulator/attestation/KeyMintAttestation.kt
+50 -2
View File
@@ -41,13 +41,29 @@ data class KeyMintAttestation(
val manufacturer: ByteArray?,
val model: ByteArray?,
val secondImei: ByteArray?,
val activeDateTime: Date?,
val originationExpireDateTime: Date?,
val usageExpireDateTime: Date?,
val usageCountLimit: Int?,
val callerNonce: Boolean?,
val unlockedDeviceRequired: Boolean?,
val includeUniqueId: Boolean?,
val rollbackResistance: Boolean?,
val earlyBootOnly: Boolean?,
val allowWhileOnBody: Boolean?,
val trustedUserPresenceRequired: Boolean?,
val trustedConfirmationRequired: Boolean?,
val noAuthRequired: Boolean?,
val maxUsesPerBoot: Int?,
val maxBootLevel: Int?,
val minMacLength: Int?,
val rsaOaepMgfDigest: List<Int>,
) {
/** Secondary constructor that populates the fields by parsing an array of `KeyParameter`. */
constructor(
params: Array<KeyParameter>
) : this(
// AOSP: [key_param(tag = KEY_SIZE, field = Integer)]
keySize = params.findInteger(Tag.KEY_SIZE) ?: 0,
keySize = params.findInteger(Tag.KEY_SIZE) ?: params.deriveKeySizeFromCurve(),
// AOSP: [key_param(tag = ALGORITHM, field = Algorithm)]
algorithm = params.findAlgorithm(Tag.ALGORITHM) ?: 0,
@@ -100,6 +116,23 @@ data class KeyMintAttestation(
manufacturer = params.findBlob(Tag.ATTESTATION_ID_MANUFACTURER),
model = params.findBlob(Tag.ATTESTATION_ID_MODEL),
secondImei = params.findBlob(Tag.ATTESTATION_ID_SECOND_IMEI),
activeDateTime = params.findDate(Tag.ACTIVE_DATETIME),
originationExpireDateTime = params.findDate(Tag.ORIGINATION_EXPIRE_DATETIME),
usageExpireDateTime = params.findDate(Tag.USAGE_EXPIRE_DATETIME),
usageCountLimit = params.findInteger(Tag.USAGE_COUNT_LIMIT),
callerNonce = params.findBoolean(Tag.CALLER_NONCE),
unlockedDeviceRequired = params.findBoolean(Tag.UNLOCKED_DEVICE_REQUIRED),
includeUniqueId = params.findBoolean(Tag.INCLUDE_UNIQUE_ID),
rollbackResistance = params.findBoolean(Tag.ROLLBACK_RESISTANCE),
earlyBootOnly = params.findBoolean(Tag.EARLY_BOOT_ONLY),
allowWhileOnBody = params.findBoolean(Tag.ALLOW_WHILE_ON_BODY),
trustedUserPresenceRequired = params.findBoolean(Tag.TRUSTED_USER_PRESENCE_REQUIRED),
trustedConfirmationRequired = params.findBoolean(Tag.TRUSTED_CONFIRMATION_REQUIRED),
noAuthRequired = params.findBoolean(Tag.NO_AUTH_REQUIRED),
maxUsesPerBoot = params.findInteger(Tag.MAX_USES_PER_BOOT),
maxBootLevel = params.findInteger(Tag.MAX_BOOT_LEVEL),
minMacLength = params.findInteger(Tag.MIN_MAC_LENGTH),
rsaOaepMgfDigest = params.findAllDigests(Tag.RSA_OAEP_MGF_DIGEST),
) {
// Log all parsed parameters for debugging purposes.
params.forEach { KeyMintParameterLogger.logParameter(it) }
@@ -156,6 +189,21 @@ private fun Array<KeyParameter>.findAllKeyPurpose(tag: Int): List<Int> =
private fun Array<KeyParameter>.findAllDigests(tag: Int): List<Int> =
this.filter { it.tag == tag }.map { it.value.digest }
private fun Array<KeyParameter>.findBoolean(tag: Int): Boolean? =
if (this.any { it.tag == tag }) true else null
private fun Array<KeyParameter>.deriveKeySizeFromCurve(): Int {
val curveId = this.find { it.tag == Tag.EC_CURVE }?.value?.ecCurve ?: return 0
return when (curveId) {
EcCurve.P_224 -> 224
EcCurve.P_256 -> 256
EcCurve.P_384 -> 384
EcCurve.P_521 -> 521
EcCurve.CURVE_25519 -> 256
else -> 0
}
}
/**
* Derives the EC Curve name. Logic: Checks specific EC_CURVE tag first (field=EcCurve), falls back
* to KEY_SIZE (field=Integer).
app/src/main/java/org/matrix/TEESimulator/pki/CertificateGenerator.kt
+26 -21
View File
@@ -8,7 +8,6 @@ import java.math.BigInteger
import java.security.KeyPair
import java.security.KeyPairGenerator
import java.security.cert.Certificate
import java.security.cert.X509Certificate
import java.security.spec.ECGenParameterSpec
import java.security.spec.RSAKeyGenParameterSpec
import java.util.Date
@@ -36,6 +35,8 @@ import org.matrix.TEESimulator.logging.SystemLogger
*/
object CertificateGenerator {
private const val UNDEFINED_NOT_AFTER = 253402300799000L
/**
* Generates a software-based cryptographic key pair.
*
@@ -49,7 +50,10 @@ object CertificateGenerator {
Algorithm.EC -> "EC" to ECGenParameterSpec(params.ecCurveName)
Algorithm.RSA ->
"RSA" to
RSAKeyGenParameterSpec(params.keySize, params.rsaPublicExponent)
RSAKeyGenParameterSpec(
params.keySize,
params.rsaPublicExponent ?: RSAKeyGenParameterSpec.F4,
)
else ->
throw IllegalArgumentException(
"Unsupported algorithm: ${params.algorithm}"
@@ -88,11 +92,9 @@ object CertificateGenerator {
"Attestation challenge exceeds length limit (${challenge.size} > ${AttestationConstants.CHALLENGE_LENGTH_LIMIT})"
)
return runCatching {
return try {
val keybox = getKeyboxForAlgorithm(uid, params.algorithm)
// Determine the signing key and issuer. If an attestKey is provided, use it.
// Otherwise, fall back to the root key from the keybox.
val (signingKey, issuer) =
if (attestKeyAlias != null && Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
getAttestationKeyInfo(uid, attestKeyAlias)?.let { it.first to it.second }
@@ -101,20 +103,20 @@ object CertificateGenerator {
keybox.keyPair to getIssuerFromKeybox(keybox)
}
// Build the new leaf certificate with the simulated attestation.
val leafCert =
buildCertificate(subjectKeyPair, signingKey, issuer, params, uid, securityLevel)
// If not self-attesting, the chain is just the leaf. Otherwise, append the keybox
// chain.
if (attestKeyAlias != null) {
listOf(leafCert)
} else {
listOf(leafCert) + keybox.certificates
}
} catch (e: android.os.ServiceSpecificException) {
throw e
} catch (e: Exception) {
SystemLogger.error("Failed to generate certificate chain.", e)
null
}
.onFailure { SystemLogger.error("Failed to generate certificate chain.", it) }
.getOrNull()
}
/**
@@ -128,7 +130,7 @@ object CertificateGenerator {
params: KeyMintAttestation,
securityLevel: Int,
): Pair<KeyPair, List<Certificate>>? {
return runCatching {
return try {
SystemLogger.info(
"Generating new attested key pair for alias: '$alias' (UID: $uid)"
)
@@ -144,11 +146,12 @@ object CertificateGenerator {
"Successfully generated new certificate chain for alias: '$alias'."
)
Pair(newKeyPair, chain)
} catch (e: android.os.ServiceSpecificException) {
throw e
} catch (e: Exception) {
SystemLogger.error("Failed to generate attested key pair for alias '$alias'.", e)
null
}
.onFailure {
SystemLogger.error("Failed to generate attested key pair for alias '$alias'.", it)
}
.getOrNull()
}
fun getIssuerFromKeybox(keybox: KeyBox) =
@@ -163,7 +166,10 @@ object CertificateGenerator {
else -> throw IllegalArgumentException("Unsupported algorithm ID: $algorithm")
}
return KeyBoxManager.getAttestationKey(keyboxFile, algorithmName)
?: throw Exception("Could not load keybox for UID $uid and algorithm $algorithmName")
?: throw android.os.ServiceSpecificException(
-75, // ATTESTATION_KEYS_NOT_PROVISIONED
"No attestation key for algorithm $algorithmName in $keyboxFile",
)
}
/** Retrieves the key pair and issuer name for a given attestation key alias. */
@@ -214,16 +220,15 @@ object CertificateGenerator {
securityLevel: Int,
): Certificate {
val subject = params.certificateSubject ?: X500Name("CN=Android Keystore Key")
val leafNotAfter =
(signingKeyPair.public as? X509Certificate)?.notAfter
?: Date(System.currentTimeMillis() + 31536000000L)
val notBefore = params.certificateNotBefore ?: Date(0)
val notAfter = params.certificateNotAfter ?: Date(UNDEFINED_NOT_AFTER)
val builder =
JcaX509v3CertificateBuilder(
issuer,
params.certificateSerial ?: BigInteger.ONE,
params.certificateNotBefore ?: Date(),
params.certificateNotAfter ?: leafNotAfter,
notBefore,
notAfter,
subject,
subjectKeyPair.public,
)