jzy/TEESimulator-RS
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fix(hardening): restore StrongBox simulation and binder buffer protection

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Restores pre-PR157 custom hardening that was lost during the reset:
- StrongBox capability check (RSA<=2048, EC=P256)
- StrongBox keygen latency floor (250ms) and op latency floor (80ms)
- StrongBox concurrent op limit (4 ops in 10s sliding window)
- MAX_ALIAS_LENGTH (256KB) binder buffer guard in handleGenerateKey

Real StrongBox hardware has these constraints. Without simulation,
detectors identify the software shim by its unrealistic performance.
This commit is contained in:
Enginex0
2026-03-22 00:17:10 +01:00
parent 3d7fd427a6
commit b63570a3e2
1 changed files with 64 additions and 6 deletions
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app/src/main/java/org/matrix/TEESimulator/interception/keystore/shim/KeyMintSecurityLevelInterceptor.kt
+64 -6
View File
@@ -1,6 +1,7 @@
package org.matrix.TEESimulator.interception.keystore.shim
import android.hardware.security.keymint.Algorithm
import android.hardware.security.keymint.EcCurve
import android.hardware.security.keymint.KeyOrigin
import android.hardware.security.keymint.KeyParameter
import android.hardware.security.keymint.KeyParameterValue
@@ -20,7 +21,10 @@ import java.security.KeyFactory
import java.security.cert.CertificateFactory
import java.security.spec.PKCS8EncodedKeySpec
import java.util.concurrent.ConcurrentHashMap
import java.util.concurrent.ConcurrentLinkedDeque
import java.util.concurrent.Executors
import java.util.concurrent.atomic.AtomicInteger
import java.util.concurrent.locks.LockSupport
import org.matrix.TEESimulator.attestation.AttestationBuilder
import org.matrix.TEESimulator.attestation.AttestationConstants
import org.matrix.TEESimulator.attestation.AttestationPatcher
@@ -48,6 +52,8 @@ class KeyMintSecurityLevelInterceptor(
) : BinderInterceptor() {
// --- Data Structures for State Management ---
private val recentOps = ConcurrentHashMap<Int, ConcurrentLinkedDeque<Long>>()
data class GeneratedKeyInfo(
val keyPair: KeyPair?,
val secretKey: javax.crypto.SecretKey?,
@@ -233,6 +239,20 @@ class KeyMintSecurityLevelInterceptor(
return TransactionResult.SkipTransaction
}
private fun trackAndEnforceOpLimit(callingUid: Int, securityLevel: Int) {
if (securityLevel != SecurityLevel.STRONGBOX) return
val timestamps = recentOps.computeIfAbsent(callingUid) { ConcurrentLinkedDeque() }
val cutoff = System.nanoTime() - STRONGBOX_OP_WINDOW_NS
timestamps.removeIf { it < cutoff }
if (timestamps.size >= STRONGBOX_MAX_CONCURRENT_OPS) {
throw android.os.ServiceSpecificException(
KEYMINT_TOO_MANY_OPERATIONS,
"StrongBox op limit reached for uid=$callingUid"
)
}
timestamps.addLast(System.nanoTime())
}
/**
* Handles the `createOperation` transaction. It checks if the operation is for a key that was
* generated in software. If so, it creates a software-based operation handler. Otherwise, it
@@ -279,6 +299,8 @@ class KeyMintSecurityLevelInterceptor(
"[TX_ID: $txId] Creating SOFTWARE operation for key ${generatedKeyInfo.nspace}."
)
trackAndEnforceOpLimit(callingUid, securityLevel)
val opParams = data.createTypedArray(KeyParameter.CREATOR)!!
val parsedOpParams = KeyMintAttestation(opParams)
val forced = data.readBoolean()
@@ -371,12 +393,14 @@ class KeyMintSecurityLevelInterceptor(
// override purpose from the operation params.
val effectiveParams =
keyParams.copy(purpose = parsedOpParams.purpose, digest = parsedOpParams.digest.ifEmpty { keyParams.digest })
val opLatency = if (securityLevel == SecurityLevel.STRONGBOX) STRONGBOX_OP_LATENCY_FLOOR_MS else 0L
val softwareOperation =
SoftwareOperation(
txId,
generatedKeyInfo.keyPair,
generatedKeyInfo.secretKey,
effectiveParams,
opLatency,
)
// Decrement usage counter on finish; delete key when exhausted.
@@ -424,6 +448,11 @@ class KeyMintSecurityLevelInterceptor(
* either generates a key in software or lets the call pass through to the hardware.
*/
private fun handleGenerateKey(txId: Long, callingUid: Int, callingPid: Int, data: Parcel): TransactionResult {
if (data.dataSize() > MAX_ALIAS_LENGTH) {
SystemLogger.warning("Skipping oversized transaction: ${data.dataSize()} bytes")
return InterceptorUtils.createErrorReply(KEYMINT_INVALID_INPUT_LENGTH)
}
return runCatching {
data.enforceInterface(IKeystoreSecurityLevel.DESCRIPTOR)
val keyDescriptor = data.readTypedObject(KeyDescriptor.CREATOR)
@@ -494,6 +523,11 @@ class KeyMintSecurityLevelInterceptor(
val isStrongBox = securityLevel == SecurityLevel.STRONGBOX
if (isStrongBox && !isStrongBoxCapable(parsedParams)) {
SystemLogger.info("[TX_ID: $txId] StrongBox-unsupported params (algo=${parsedParams.algorithm} size=${parsedParams.keySize}), forwarding to HAL")
return TransactionResult.ContinueAndSkipPost
}
when {
forceGenerate -> doSoftwareGeneration(
callingUid, keyDescriptor, attestationKey, parsedParams, isAttestKeyRequest
@@ -571,9 +605,15 @@ class KeyMintSecurityLevelInterceptor(
}
generatedKeys[keyId] =
GeneratedKeyInfo(null, secretKey, keyDescriptor.nspace, response, parsedParams)
TeeLatencySimulator.simulateGenerateKeyDelay(
parsedParams.algorithm, System.nanoTime() - genStartNanos
)
if (securityLevel == SecurityLevel.STRONGBOX) {
val delayMs = STRONGBOX_KEYGEN_LATENCY_FLOOR_MS - (System.nanoTime() - genStartNanos) / 1_000_000
if (delayMs > 0) LockSupport.parkNanos(delayMs * 1_000_000)
} else {
TeeLatencySimulator.simulateGenerateKeyDelay(
parsedParams.algorithm, System.nanoTime() - genStartNanos
)
}
return InterceptorUtils.createTypedObjectReply(metadata)
}
@@ -613,9 +653,14 @@ class KeyMintSecurityLevelInterceptor(
)
}
TeeLatencySimulator.simulateGenerateKeyDelay(
parsedParams.algorithm, System.nanoTime() - genStartNanos
)
if (securityLevel == SecurityLevel.STRONGBOX) {
val delayMs = STRONGBOX_KEYGEN_LATENCY_FLOOR_MS - (System.nanoTime() - genStartNanos) / 1_000_000
if (delayMs > 0) LockSupport.parkNanos(delayMs * 1_000_000)
} else {
TeeLatencySimulator.simulateGenerateKeyDelay(
parsedParams.algorithm, System.nanoTime() - genStartNanos
)
}
return InterceptorUtils.createTypedObjectReply(response.metadata)
}
@@ -900,11 +945,24 @@ class KeyMintSecurityLevelInterceptor(
private const val KEYMINT_INVALID_INPUT_LENGTH = -21
private const val KEYMINT_INVALID_ARGUMENT = -38
private const val KEYMINT_TOO_MANY_OPERATIONS = -29
private const val INVALID_ARGUMENT = 20
private const val PERMISSION_DENIED = 6
private const val SECURE_HW_COMMUNICATION_FAILED = -49
private const val CANNOT_ATTEST_IDS = -66
private const val STRONGBOX_KEYGEN_LATENCY_FLOOR_MS = 250L
private const val STRONGBOX_OP_LATENCY_FLOOR_MS = 80L
private const val STRONGBOX_MAX_CONCURRENT_OPS = 4
private const val STRONGBOX_OP_WINDOW_NS = 10_000_000_000L
private const val MAX_ALIAS_LENGTH = 256 * 1024
private fun isStrongBoxCapable(params: KeyMintAttestation): Boolean = when (params.algorithm) {
Algorithm.RSA -> params.keySize <= 2048
Algorithm.EC -> params.ecCurve == null || params.ecCurve == EcCurve.P_256
else -> true
}
// Transaction codes for IKeystoreSecurityLevel interface.
private val GENERATE_KEY_TRANSACTION =
InterceptorUtils.getTransactCode(IKeystoreSecurityLevel.Stub::class.java, "generateKey")