feat(interception): dynamically register SecurityLevel binder interceptors

keystore2 may return a different BBinder for each getSecurityLevel call,
so the initial registration during setup might not cover all binder
instances that client apps receive. Intercept getSecurityLevel replies
to register our hook on every new BBinder, deduplicated by identity hash.

app/src/main/java/org/matrix/TEESimulator/interception/keystore/Keystore2Interceptor.kt

@@ -6,11 +6,13 @@ import android.os.Build
 import android.os.IBinder
 import android.os.Parcel
 import android.system.keystore2.Domain
+import android.system.keystore2.IKeystoreSecurityLevel
 import android.system.keystore2.IKeystoreService
 import android.system.keystore2.KeyDescriptor
 import android.system.keystore2.KeyEntryResponse
 import java.security.SecureRandom
 import java.security.cert.Certificate
+import java.util.Collections
 import java.util.concurrent.ConcurrentHashMap
 import org.matrix.TEESimulator.attestation.AttestationPatcher
 import org.matrix.TEESimulator.attestation.KeyMintAttestation
@@ -47,6 +49,8 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
         else null
     private val GET_NUMBER_OF_ENTRIES_TRANSACTION =
         InterceptorUtils.getTransactCode(stubBinderClass, "getNumberOfEntries")
+    private val GET_SECURITY_LEVEL_TRANSACTION =
+        InterceptorUtils.getTransactCode(stubBinderClass, "getSecurityLevel")
 
     private val transactionNames: Map<Int, String> by lazy {
         stubBinderClass.declaredFields
@@ -60,6 +64,17 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
     // Keys whose certs were updated via updateSubcomponent; skip re-patching on getKeyEntry.
     private val userUpdatedKeys = ConcurrentHashMap.newKeySet<KeyIdentifier>()
 
+    // Backdoor binder for registering new interceptors at runtime.
+    private var backdoorBinder: IBinder? = null
+
+    // Per-security-level interceptor instances, keyed by SecurityLevel constant.
+    private val securityLevelInterceptors = ConcurrentHashMap<Int, KeyMintSecurityLevelInterceptor>()
+
+    // Identity set of SecurityLevel binders already registered with the native hook,
+    // tracked by System.identityHashCode to avoid re-registering the same BBinder.
+    private val registeredSecurityLevelBinders: MutableSet<Int> =
+        Collections.newSetFromMap(ConcurrentHashMap())
+
     override val serviceName = "android.system.keystore2.IKeystoreService/default"
     override val processName = "keystore2"
     override val injectionCommand = "exec ./inject `pidof keystore2` libTEESimulator.so entry"
@@ -72,6 +87,7 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
                 LIST_ENTRIES_TRANSACTION,
                 LIST_ENTRIES_BATCHED_TRANSACTION,
                 GET_NUMBER_OF_ENTRIES_TRANSACTION,
+                GET_SECURITY_LEVEL_TRANSACTION,
             )
             .toIntArray()
     }
@@ -81,6 +97,7 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
      * security level sub-services (e.g., TEE, StrongBox).
      */
     override fun onInterceptorReady(service: IBinder, backdoor: IBinder) {
+        backdoorBinder = backdoor
         val keystoreInterface = IKeystoreService.Stub.asInterface(service)
         setupSecurityLevelInterceptors(keystoreInterface, backdoor)
     }
@@ -92,11 +109,11 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
                     SystemLogger.info("Found TEE SecurityLevel. Registering interceptor...")
                     val interceptor =
                         KeyMintSecurityLevelInterceptor(tee, SecurityLevel.TRUSTED_ENVIRONMENT)
-                    register(
+                    securityLevelInterceptors[SecurityLevel.TRUSTED_ENVIRONMENT] = interceptor
+                    registerSecurityLevelBinder(
                         backdoor,
                         tee.asBinder(),
                         interceptor,
-                        KeyMintSecurityLevelInterceptor.INTERCEPTED_CODES,
                     )
                     interceptor.loadPersistedKeys()
                 }
@@ -109,11 +126,11 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
                     SystemLogger.info("Found StrongBox SecurityLevel. Registering interceptor...")
                     val interceptor =
                         KeyMintSecurityLevelInterceptor(strongbox, SecurityLevel.STRONGBOX)
-                    register(
+                    securityLevelInterceptors[SecurityLevel.STRONGBOX] = interceptor
+                    registerSecurityLevelBinder(
                         backdoor,
                         strongbox.asBinder(),
                         interceptor,
-                        KeyMintSecurityLevelInterceptor.INTERCEPTED_CODES,
                     )
                     interceptor.loadPersistedKeys()
                 }
@@ -121,6 +138,30 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
             .onFailure { SystemLogger.error("Failed to intercept StrongBox SecurityLevel.", it) }
     }
 
+    /**
+     * Registers an interceptor for a SecurityLevel binder, tracking the binder identity
+     * to avoid duplicate registrations when keystore2 returns the same BBinder.
+     */
+    private fun registerSecurityLevelBinder(
+        backdoor: IBinder,
+        binder: IBinder,
+        interceptor: KeyMintSecurityLevelInterceptor,
+    ) {
+        val identity = System.identityHashCode(binder)
+        if (registeredSecurityLevelBinders.add(identity)) {
+            register(
+                backdoor,
+                binder,
+                interceptor,
+                KeyMintSecurityLevelInterceptor.INTERCEPTED_CODES,
+            )
+        } else {
+            SystemLogger.debug(
+                "SecurityLevel binder $binder (identity=$identity) already registered, skipping."
+            )
+        }
+    }
+
     override fun onPreTransact(
         txId: Long,
         target: IBinder,
@@ -210,6 +251,13 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
                 KeyMintParameterLogger.logParameter(it.keyParameter)
             }
             return InterceptorUtils.createTypedObjectReply(response)
+        } else if (code == GET_SECURITY_LEVEL_TRANSACTION) {
+            // Pass through to post-hook so we can register interceptors for newly-created
+            // SecurityLevel binders. keystore2 may create a new BBinder per call, so the
+            // initial registration in setupSecurityLevelInterceptors might not cover all
+            // binder instances that clients receive.
+            logTransaction(txId, "getSecurityLevel", callingUid, callingPid)
+            return TransactionResult.Continue
         } else {
             logTransaction(
                 txId,
@@ -238,6 +286,10 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
         if (target != keystoreService || reply == null || InterceptorUtils.hasException(reply))
             return TransactionResult.SkipTransaction
 
+        if (code == GET_SECURITY_LEVEL_TRANSACTION) {
+            return handlePostGetSecurityLevel(txId, data, reply)
+        }
+
         if (code == GET_NUMBER_OF_ENTRIES_TRANSACTION) {
             logTransaction(txId, "post-${transactionNames[code]!!}", callingUid, callingPid)
             return runCatching {
@@ -442,4 +494,67 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
 
         return InterceptorUtils.createSuccessReply(writeResultCode = false)
     }
+
+    /**
+     * Intercepts the reply from getSecurityLevel to dynamically register our interceptor
+     * for the returned IKeystoreSecurityLevel binder.
+     *
+     * keystore2 may create a new BBinder for each getSecurityLevel call, so the binder
+     * registered during initial setup (in setupSecurityLevelInterceptors) might not be the
+     * same one that client apps receive. By intercepting every getSecurityLevel reply, we
+     * ensure that all SecurityLevel binders are covered.
+     */
+    private fun handlePostGetSecurityLevel(
+        txId: Long,
+        data: Parcel,
+        reply: Parcel,
+    ): TransactionResult {
+        val backdoor = backdoorBinder
+        if (backdoor == null) {
+            SystemLogger.warning("[TX_ID: $txId] post-getSecurityLevel: backdoor not available")
+            return TransactionResult.SkipTransaction
+        }
+
+        return runCatching {
+            // Read the security level argument from the original request.
+            data.enforceInterface(IKeystoreService.DESCRIPTOR)
+            val requestedLevel = data.readInt()
+
+            // hasException already consumed the exception header from the reply.
+            // Next item is the IKeystoreSecurityLevel binder.
+            val secLevelBinder = reply.readStrongBinder()
+            if (secLevelBinder == null) {
+                SystemLogger.verbose(
+                    "[TX_ID: $txId] getSecurityLevel($requestedLevel) returned null binder"
+                )
+                return@runCatching TransactionResult.SkipTransaction
+            }
+
+            // Only intercept TEE and StrongBox security levels.
+            if (requestedLevel != SecurityLevel.TRUSTED_ENVIRONMENT &&
+                requestedLevel != SecurityLevel.STRONGBOX
+            ) {
+                return@runCatching TransactionResult.SkipTransaction
+            }
+
+            // Get or create the interceptor for this security level. The interceptor may not
+            // exist yet if the initial setupSecurityLevelInterceptors call failed for this level.
+            val interceptor = securityLevelInterceptors.getOrPut(requestedLevel) {
+                val secLevelInterface =
+                    IKeystoreSecurityLevel.Stub.asInterface(secLevelBinder)
+                SystemLogger.info(
+                    "[TX_ID: $txId] Late-creating interceptor for security level $requestedLevel"
+                )
+                KeyMintSecurityLevelInterceptor(secLevelInterface, requestedLevel).also {
+                    it.loadPersistedKeys()
+                }
+            }
+
+            registerSecurityLevelBinder(backdoor, secLevelBinder, interceptor)
+            TransactionResult.SkipTransaction
+        }.getOrElse {
+            SystemLogger.error("[TX_ID: $txId] Failed to process post-getSecurityLevel.", it)
+            TransactionResult.SkipTransaction
+        }
+    }
 }