Rate-limit per-UID hardware keygen and harden importKey eviction
Sliding window limits each UID to 2 hardware generateKey calls per 30s burst window with max 2 concurrent. Overflow falls back to software cert generation. importKey post-hook retains patched chains instead of full eviction, preventing detectors from using generate-then-import to bypass attestation patching. getKeyEntry serves retained chains for imported keys that overwrote attested aliases.
This commit is contained in:
Enginex0
+8
-1
@@ -235,9 +235,16 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
|
||||
?.let { it.keyParameter.value.origin }
|
||||
|
||||
if (origin == KeyOrigin.IMPORTED || origin == KeyOrigin.SECURELY_IMPORTED) {
|
||||
SystemLogger.info("[TX_ID: $txId] Skip patching for imported keys.")
|
||||
val keyId = KeyIdentifier(callingUid, keyDescriptor.alias)
|
||||
val retainedChain = KeyMintSecurityLevelInterceptor.getPatchedChain(keyId)
|
||||
if (retainedChain == null) {
|
||||
SystemLogger.info("[TX_ID: $txId] Skip patching for imported key (no prior attestation).")
|
||||
return TransactionResult.SkipTransaction
|
||||
}
|
||||
SystemLogger.info("[TX_ID: $txId] Imported key overwrote attested alias, serving retained chain for $keyId")
|
||||
CertificateHelper.updateCertificateChain(response.metadata, retainedChain).getOrThrow()
|
||||
return InterceptorUtils.createTypedObjectReply(response)
|
||||
}
|
||||
|
||||
if (originalChain == null || originalChain.size < 2) {
|
||||
SystemLogger.info(
|
||||
|
||||
+94
-35
@@ -16,6 +16,7 @@ import java.security.cert.Certificate
|
||||
import java.security.cert.CertificateFactory
|
||||
import java.security.spec.PKCS8EncodedKeySpec
|
||||
import java.util.concurrent.ConcurrentHashMap
|
||||
import java.util.concurrent.atomic.AtomicInteger
|
||||
import org.matrix.TEESimulator.attestation.AttestationPatcher
|
||||
import org.matrix.TEESimulator.attestation.KeyMintAttestation
|
||||
import org.matrix.TEESimulator.config.ConfigurationManager
|
||||
@@ -52,7 +53,7 @@ class KeyMintSecurityLevelInterceptor(
|
||||
GENERATE_KEY_TRANSACTION -> {
|
||||
logTransaction(txId, transactionNames[code]!!, callingUid, callingPid)
|
||||
|
||||
if (!shouldSkip) return handleGenerateKey(callingUid, data)
|
||||
if (!shouldSkip) return handleGenerateKey(txId, callingUid, data)
|
||||
}
|
||||
CREATE_OPERATION_TRANSACTION -> {
|
||||
logTransaction(txId, transactionNames[code]!!, callingUid, callingPid)
|
||||
@@ -93,6 +94,11 @@ class KeyMintSecurityLevelInterceptor(
|
||||
reply: Parcel?,
|
||||
resultCode: Int,
|
||||
): TransactionResult {
|
||||
if (code == GENERATE_KEY_TRANSACTION && hardwareKeygenTxIds.remove(txId)) {
|
||||
val remaining = hardwareKeygenCount(callingUid).decrementAndGet()
|
||||
SystemLogger.info("[TX_ID: $txId] PERMIT_RELEASED uid=$callingUid concurrent_remaining=$remaining result=${if (resultCode == 0) "OK" else "ERROR($resultCode)"}")
|
||||
}
|
||||
|
||||
// We only care about successful transactions.
|
||||
if (resultCode != 0 || reply == null || InterceptorUtils.hasException(reply))
|
||||
return TransactionResult.SkipTransaction
|
||||
@@ -104,7 +110,14 @@ class KeyMintSecurityLevelInterceptor(
|
||||
val keyDescriptor =
|
||||
data.readTypedObject(KeyDescriptor.CREATOR)
|
||||
?: return TransactionResult.SkipTransaction
|
||||
cleanupKeyData(KeyIdentifier(callingUid, keyDescriptor.alias))
|
||||
// Evict generated key data but retain patched chains so detectors
|
||||
// can't use importKey to force unpatched getKeyEntry responses.
|
||||
val keyId = KeyIdentifier(callingUid, keyDescriptor.alias)
|
||||
if (generatedKeys.remove(keyId) != null) {
|
||||
SystemLogger.debug("Remove generated key on importKey $keyId")
|
||||
GeneratedKeyPersistence.delete(keyId)
|
||||
}
|
||||
attestationKeys.remove(keyId)
|
||||
} else if (code == CREATE_OPERATION_TRANSACTION) {
|
||||
logTransaction(txId, "post-${transactionNames[code]!!}", callingUid, callingPid)
|
||||
|
||||
@@ -212,18 +225,17 @@ class KeyMintSecurityLevelInterceptor(
|
||||
return InterceptorUtils.createTypedObjectReply(response)
|
||||
}
|
||||
|
||||
private fun handleGenerateKey(callingUid: Int, data: Parcel): TransactionResult {
|
||||
private fun handleGenerateKey(txId: Long, callingUid: Int, data: Parcel): TransactionResult {
|
||||
if (data.dataSize() > MAX_ALIAS_LENGTH) {
|
||||
SystemLogger.warning("Skipping oversized transaction: ${data.dataSize()} bytes")
|
||||
return TransactionResult.ContinueAndSkipPost
|
||||
}
|
||||
|
||||
return runCatching {
|
||||
data.enforceInterface(IKeystoreSecurityLevel.DESCRIPTOR)
|
||||
val keyDescriptor = data.readTypedObject(KeyDescriptor.CREATOR)!!
|
||||
val attestationKey = data.readTypedObject(KeyDescriptor.CREATOR)
|
||||
|
||||
// Reject oversized aliases to prevent binder buffer exhaustion (Issue #109)
|
||||
if (keyDescriptor.alias.length > MAX_ALIAS_LENGTH) {
|
||||
SystemLogger.warning("Rejecting oversized alias: ${keyDescriptor.alias.length} bytes (max: $MAX_ALIAS_LENGTH)")
|
||||
return TransactionResult.ContinueAndSkipPost
|
||||
}
|
||||
|
||||
SystemLogger.debug(
|
||||
"Handling generateKey ${keyDescriptor.alias}, attestKey=${attestationKey?.alias}"
|
||||
)
|
||||
@@ -241,25 +253,56 @@ class KeyMintSecurityLevelInterceptor(
|
||||
isAttestationKey(KeyIdentifier(callingUid, attestationKey.alias)))
|
||||
|
||||
if (needsSoftwareGeneration) {
|
||||
keyDescriptor.nspace = secureRandom.nextLong()
|
||||
SystemLogger.info(
|
||||
"Generating software key for ${keyDescriptor.alias}[${keyDescriptor.nspace}]."
|
||||
)
|
||||
return doSoftwareKeyGen(callingUid, keyDescriptor, attestationKey, parsedParams, keyId, isAttestKeyRequest)
|
||||
} else if (parsedParams.attestationChallenge != null) {
|
||||
val windowUsed = hardwareKeygenWindowCount(callingUid)
|
||||
val concurrentUsed = hardwareKeygenCount(callingUid).get()
|
||||
|
||||
val keyData =
|
||||
CertificateGenerator.generateAttestedKeyPair(
|
||||
callingUid,
|
||||
keyDescriptor.alias,
|
||||
attestationKey?.alias,
|
||||
parsedParams,
|
||||
securityLevel,
|
||||
// Sliding window rate limit
|
||||
if (windowUsed >= MAX_HW_KEYGEN_PER_WINDOW) {
|
||||
SystemLogger.info("[TX_ID: $txId] RATE_LIMITED uid=$callingUid window=$windowUsed/$MAX_HW_KEYGEN_PER_WINDOW concurrent=$concurrentUsed → software fallback")
|
||||
return doSoftwareKeyGen(callingUid, keyDescriptor, attestationKey, parsedParams, keyId, isAttestKeyRequest)
|
||||
}
|
||||
// Concurrent cap
|
||||
if (hardwareKeygenCount(callingUid).incrementAndGet() > MAX_CONCURRENT_HW_KEYGEN_PER_UID) {
|
||||
hardwareKeygenCount(callingUid).decrementAndGet()
|
||||
SystemLogger.info("[TX_ID: $txId] CONCURRENT_LIMITED uid=$callingUid window=$windowUsed/$MAX_HW_KEYGEN_PER_WINDOW concurrent=${concurrentUsed + 1}/$MAX_CONCURRENT_HW_KEYGEN_PER_UID → software fallback")
|
||||
return doSoftwareKeyGen(callingUid, keyDescriptor, attestationKey, parsedParams, keyId, isAttestKeyRequest)
|
||||
}
|
||||
// Both checks passed — commit the window permit and forward to hardware TEE
|
||||
recordHardwareKeygen(callingUid)
|
||||
hardwareKeygenTxIds.add(txId)
|
||||
SystemLogger.info("[TX_ID: $txId] HARDWARE_KEYGEN uid=$callingUid window=${windowUsed + 1}/$MAX_HW_KEYGEN_PER_WINDOW concurrent=${concurrentUsed + 1}/$MAX_CONCURRENT_HW_KEYGEN_PER_UID → forwarding to TEE")
|
||||
return TransactionResult.Continue
|
||||
}
|
||||
|
||||
cleanupKeyData(keyId)
|
||||
TransactionResult.ContinueAndSkipPost
|
||||
}
|
||||
.getOrElse {
|
||||
SystemLogger.error("Error during generateKey handling for UID $callingUid.", it)
|
||||
TransactionResult.ContinueAndSkipPost
|
||||
}
|
||||
}
|
||||
|
||||
private fun doSoftwareKeyGen(
|
||||
callingUid: Int,
|
||||
keyDescriptor: KeyDescriptor,
|
||||
attestationKey: KeyDescriptor?,
|
||||
parsedParams: KeyMintAttestation,
|
||||
keyId: KeyIdentifier,
|
||||
isAttestKeyRequest: Boolean,
|
||||
): TransactionResult {
|
||||
keyDescriptor.nspace = secureRandom.nextLong()
|
||||
SystemLogger.info("Generating software key for ${keyDescriptor.alias}[${keyDescriptor.nspace}].")
|
||||
|
||||
val keyData = CertificateGenerator.generateAttestedKeyPair(
|
||||
callingUid, keyDescriptor.alias, attestationKey?.alias, parsedParams, securityLevel,
|
||||
) ?: throw Exception("CertificateGenerator failed to create key pair.")
|
||||
|
||||
cleanupKeyData(keyId)
|
||||
val response =
|
||||
buildKeyEntryResponse(keyData.second, parsedParams, keyDescriptor)
|
||||
generatedKeys[keyId] =
|
||||
GeneratedKeyInfo(keyData.first, keyDescriptor.nspace, response)
|
||||
val response = buildKeyEntryResponse(keyData.second, parsedParams, keyDescriptor)
|
||||
generatedKeys[keyId] = GeneratedKeyInfo(keyData.first, keyDescriptor.nspace, response)
|
||||
if (isAttestKeyRequest) attestationKeys.add(keyId)
|
||||
|
||||
GeneratedKeyPersistence.save(
|
||||
@@ -277,17 +320,6 @@ class KeyMintSecurityLevelInterceptor(
|
||||
)
|
||||
|
||||
return InterceptorUtils.createTypedObjectReply(response.metadata)
|
||||
} else if (parsedParams.attestationChallenge != null) {
|
||||
return TransactionResult.Continue
|
||||
}
|
||||
|
||||
cleanupKeyData(keyId)
|
||||
TransactionResult.ContinueAndSkipPost
|
||||
}
|
||||
.getOrElse {
|
||||
SystemLogger.error("Error during generateKey handling for UID $callingUid.", it)
|
||||
TransactionResult.ContinueAndSkipPost
|
||||
}
|
||||
}
|
||||
|
||||
private fun buildKeyEntryResponse(
|
||||
@@ -395,6 +427,33 @@ class KeyMintSecurityLevelInterceptor(
|
||||
// Maximum alias length to prevent binder buffer exhaustion (Issue #109)
|
||||
// Binder buffer is ~1MB; 256KB provides 4x safety margin for transaction overhead
|
||||
private const val MAX_ALIAS_LENGTH = 256 * 1024
|
||||
private const val MAX_CONCURRENT_HW_KEYGEN_PER_UID = 2
|
||||
// Sliding window: max hardware keygen permits per UID within the burst window
|
||||
private const val MAX_HW_KEYGEN_PER_WINDOW = 2
|
||||
private const val BURST_WINDOW_MS = 30_000L
|
||||
|
||||
private val uidHardwareKeygenCount = ConcurrentHashMap<Int, AtomicInteger>()
|
||||
private val hardwareKeygenTxIds = ConcurrentHashMap.newKeySet<Long>()
|
||||
private val uidKeygenTimestamps = ConcurrentHashMap<Int, MutableList<Long>>()
|
||||
|
||||
private fun hardwareKeygenCount(uid: Int): AtomicInteger =
|
||||
uidHardwareKeygenCount.computeIfAbsent(uid) { AtomicInteger(0) }
|
||||
|
||||
private fun hardwareKeygenWindowCount(uid: Int): Int {
|
||||
val now = System.currentTimeMillis()
|
||||
val timestamps = uidKeygenTimestamps.computeIfAbsent(uid) { mutableListOf() }
|
||||
synchronized(timestamps) {
|
||||
timestamps.removeAll { now - it > BURST_WINDOW_MS }
|
||||
return timestamps.size
|
||||
}
|
||||
}
|
||||
|
||||
private fun recordHardwareKeygen(uid: Int) {
|
||||
val timestamps = uidKeygenTimestamps.computeIfAbsent(uid) { mutableListOf() }
|
||||
synchronized(timestamps) {
|
||||
timestamps.add(System.currentTimeMillis())
|
||||
}
|
||||
}
|
||||
|
||||
private val GENERATE_KEY_TRANSACTION =
|
||||
InterceptorUtils.getTransactCode(IKeystoreSecurityLevel.Stub::class.java, "generateKey")
|
||||
|
||||
Reference in New Issue
Block a user