Made key assertion optional for hardcoded issuing authority to avoid …

…the need for minimal wallet server. (#825)

Signed-off-by: Peter Sorotokin <[email protected]>

identity-issuance-api/src/commonMain/kotlin/com/android/identity/issuance/CredentialConfiguration.kt

@@ -14,6 +14,11 @@ data class CredentialConfiguration(
      */
     val challenge: ByteString,
 
+    /**
+     * Key assertion parameter to [RequestCredentialsFlow.sendCredentials] is required.
+     */
+    val keyAssertionRequired: Boolean,
+
     /**
      * The configuration for the device-bound key for e.g. access control.
      *

identity-issuance-api/src/commonMain/kotlin/com/android/identity/issuance/RequestCredentialsFlow.kt

@@ -33,12 +33,14 @@ interface RequestCredentialsFlow : FlowBase {
      *
      * @param credentialRequests a list of credentials requests, each representing a
      *   request for a issuer data generation along with the format requested.
+     * @param keysAssertion DeviceAssertion that wraps AssertionBindingKeys, only required
+     *   if [CredentialConfiguration.keyAssertionRequired] is true
      * @throws IllegalArgumentException if the issuer rejects the one or more of the requests.
      */
     @FlowMethod
     suspend fun sendCredentials(
         credentialRequests: List<CredentialRequest>,
-        keysAssertion: DeviceAssertion  // wraps AssertionBindingKeys
+        keysAssertion: DeviceAssertion?
     ): List<KeyPossessionChallenge>
 
     @FlowMethod

identity-issuance/src/main/java/com/android/identity/issuance/funke/FunkeIssuingAuthorityState.kt

@@ -329,8 +329,9 @@ class FunkeIssuingAuthorityState(
         val purposes = setOf(KeyPurpose.SIGN, KeyPurpose.AGREE_KEY)
         val configuration = if (document.secureAreaIdentifier!!.startsWith("CloudSecureArea?")) {
             CredentialConfiguration(
-                ByteString(cNonce.toByteArray()),
-                SecureAreaConfigurationCloud(
+                challenge = ByteString(cNonce.toByteArray()),
+                keyAssertionRequired = true,
+                secureAreaConfiguration = SecureAreaConfigurationCloud(
                     purposes = KeyPurpose.encodeSet(purposes),
                     curve = EcCurve.P256.coseCurveIdentifier,
                     cloudSecureAreaId = document.secureAreaIdentifier!!,
@@ -343,8 +344,9 @@ class FunkeIssuingAuthorityState(
             )
         } else {
             CredentialConfiguration(
-                ByteString(cNonce.toByteArray()),
-                SecureAreaConfigurationAndroidKeystore(
+                challenge = ByteString(cNonce.toByteArray()),
+                keyAssertionRequired = true,
+                secureAreaConfiguration = SecureAreaConfigurationAndroidKeystore(
                     purposes = KeyPurpose.encodeSet(purposes),
                     curve = EcCurve.P256.coseCurveIdentifier,
                     useStrongBox = true,

identity-issuance/src/main/java/com/android/identity/issuance/funke/FunkeProofingState.kt

@@ -443,10 +443,12 @@ class FunkeProofingState(
             val assertionMaker = env.getInterface(DeviceAssertionMaker::class)!!
             applicationSupport.createJwtClientAssertion(
                 clientKeyInfo.attestation,
-                assertionMaker.makeDeviceAssertion(AssertionDPoPKey(
-                    clientKeyInfo.publicKey,
-                    credentialIssuerUri
-                ))
+                assertionMaker.makeDeviceAssertion {
+                    AssertionDPoPKey(
+                        clientKeyInfo.publicKey,
+                        credentialIssuerUri
+                    )
+                }
             )
         } else {
             ApplicationSupportState(clientId).createJwtClientAssertion(

identity-issuance/src/main/java/com/android/identity/issuance/funke/RequestCredentialsUsingKeyAttestation.kt

@@ -38,12 +38,12 @@ class RequestCredentialsUsingKeyAttestation(
     fun sendCredentials(
         env: FlowEnvironment,
         credentialRequests: List<CredentialRequest>,
-        keysAssertion: DeviceAssertion // holds AssertionBingingKeys
+        keysAssertion: DeviceAssertion? // holds AssertionBingingKeys
     ): List<KeyPossessionChallenge> {
         credentialRequestSets.add(CredentialRequestSet(
             format = format!!,
             keyAttestations = credentialRequests.map { it.secureAreaBoundKeyAttestation },
-            keysAssertion = keysAssertion
+            keysAssertion = keysAssertion!!
         ))
         return emptyList()
     }

identity-issuance/src/main/java/com/android/identity/issuance/funke/RequestCredentialsUsingProofOfPossession.kt

@@ -49,7 +49,7 @@ class RequestCredentialsUsingProofOfPossession(
     suspend fun sendCredentials(
         env: FlowEnvironment,
         newCredentialRequests: List<CredentialRequest>,
-        keysAssertion: DeviceAssertion
+        keysAssertion: DeviceAssertion?
     ): List<KeyPossessionChallenge> {
         if (credentialRequests != null) {
             throw IllegalStateException("Credentials were already sent")
@@ -61,7 +61,7 @@ class RequestCredentialsUsingProofOfPossession(
             env = env,
             deviceAttestation = clientRecord.deviceAttestation,
             keyAttestations = newCredentialRequests.map { it.secureAreaBoundKeyAttestation },
-            deviceAssertion = keysAssertion,
+            deviceAssertion = keysAssertion!!,
             nonce = credentialConfiguration.challenge
         )
         val nonce = JsonPrimitive(String(credentialConfiguration.challenge.toByteArray()))

identity-issuance/src/main/java/com/android/identity/issuance/hardcoded/IssuingAuthorityState.kt

@@ -289,31 +289,31 @@ class IssuingAuthorityState(
             walletApplicationCapabilities,
             issuerDocument.collectedEvidence
         )
-        return RequestCredentialsState(clientId, documentId, credentialConfiguration)
+        return RequestCredentialsState(documentId, credentialConfiguration)
     }
 
     @FlowJoin
     suspend fun completeRequestCredentials(env: FlowEnvironment, state: RequestCredentialsState) {
         val issuerDocument = loadIssuerDocument(env, state.documentId)
-        for (bindingKeySet in state.bindingKeys) {
+        for (request in state.credentialRequests) {
             // Skip if we already have a request for the authentication key
-            for (authenticationKey in bindingKeySet.publicKeys) {
-                if (hasCpoRequestForAuthenticationKey(issuerDocument, authenticationKey)) {
-                    continue
-                }
-                val presentationData = createPresentationData(
-                    env,
-                    state.format!!,
-                    issuerDocument.documentConfiguration!!,
-                    authenticationKey
-                )
-                val simpleCredentialRequest = SimpleCredentialRequest(
-                    authenticationKey,
-                    CredentialFormat.MDOC_MSO,
-                    presentationData,
-                )
-                issuerDocument.simpleCredentialRequests.add(simpleCredentialRequest)
+            if (hasCpoRequestForAuthenticationKey(issuerDocument,
+                    request.secureAreaBoundKeyAttestation.publicKey)) {
+                continue
             }
+            val authenticationKey = request.secureAreaBoundKeyAttestation.publicKey
+            val presentationData = createPresentationData(
+                env,
+                state.format!!,
+                issuerDocument.documentConfiguration!!,
+                authenticationKey
+            )
+            val simpleCredentialRequest = SimpleCredentialRequest(
+                authenticationKey,
+                CredentialFormat.MDOC_MSO,
+                presentationData,
+            )
+            issuerDocument.simpleCredentialRequests.add(simpleCredentialRequest)
         }
         updateIssuerDocument(env, state.documentId, issuerDocument)
     }

identity-issuance/src/main/java/com/android/identity/issuance/hardcoded/RequestCredentialsState.kt

@@ -1,33 +1,26 @@
 package com.android.identity.issuance.hardcoded
 
 import com.android.identity.cbor.annotation.CborSerializable
-import com.android.identity.device.AssertionBindingKeys
 import com.android.identity.device.DeviceAssertion
 import com.android.identity.flow.annotation.FlowMethod
 import com.android.identity.flow.annotation.FlowState
 import com.android.identity.flow.server.FlowEnvironment
-import com.android.identity.flow.server.Storage
 import com.android.identity.issuance.CredentialConfiguration
 import com.android.identity.issuance.CredentialFormat
 import com.android.identity.issuance.CredentialRequest
 import com.android.identity.issuance.KeyPossessionChallenge
 import com.android.identity.issuance.KeyPossessionProof
 import com.android.identity.issuance.RequestCredentialsFlow
-import com.android.identity.issuance.validateDeviceAssertionBindingKeys
-import com.android.identity.issuance.wallet.ClientRecord
-import com.android.identity.issuance.wallet.fromCbor
-import com.android.identity.securearea.config.SecureAreaConfigurationSoftware
 
 /**
  * State of [RequestCredentialsFlow] RPC implementation.
  */
 @FlowState(flowInterface = RequestCredentialsFlow::class)
 @CborSerializable
 class RequestCredentialsState(
-    val clientId: String,
     val documentId: String,
     val credentialConfiguration: CredentialConfiguration,
-    val bindingKeys: MutableList<AssertionBindingKeys> = mutableListOf(),
+    val credentialRequests: MutableList<CredentialRequest> = mutableListOf(),
     var format: CredentialFormat? = null
 ) {
     companion object {}
@@ -46,25 +39,9 @@ class RequestCredentialsState(
     suspend fun sendCredentials(
         env: FlowEnvironment,
         credentialRequests: List<CredentialRequest>,
-        keysAssertion: DeviceAssertion
+        keysAssertion: DeviceAssertion?
     ): List<KeyPossessionChallenge> {
-        val storage = env.getInterface(Storage::class)!!
-        val clientRecord = ClientRecord.fromCbor(
-            storage.get("Clients", "", clientId)!!.toByteArray())
-        val assertion = if (credentialConfiguration.secureAreaConfiguration is SecureAreaConfigurationSoftware) {
-            // if explicitly asked for software secure area, don't validate
-            // (it will fail), just blindly trust.
-            keysAssertion.assertion as AssertionBindingKeys
-        } else {
-            validateDeviceAssertionBindingKeys(
-                env = env,
-                deviceAttestation = clientRecord.deviceAttestation,
-                keyAttestations = credentialRequests.map { it.secureAreaBoundKeyAttestation },
-                deviceAssertion = keysAssertion,
-                nonce = credentialConfiguration.challenge
-            )
-        }
-        bindingKeys.add(assertion)
+        this.credentialRequests.addAll(credentialRequests)
         return emptyList()
     }
 

identity-issuance/src/main/java/com/android/identity/issuance/proofing/defaultGraph.kt

@@ -238,8 +238,9 @@ fun defaultCredentialConfiguration(
     val challenge = ByteString(Random.nextBytes(16))
     if (!collectedEvidence.containsKey("devmode_sa")) {
         return CredentialConfiguration(
-            challenge,
-            SecureAreaConfigurationAndroidKeystore(
+            challenge = challenge,
+            keyAssertionRequired = false,
+            secureAreaConfiguration = SecureAreaConfigurationAndroidKeystore(
                 purposes = KeyPurpose.encodeSet(setOf(KeyPurpose.SIGN)),
                 curve = EcCurve.P256.coseCurveIdentifier,
                 useStrongBox = true,
@@ -299,8 +300,9 @@ fun defaultCredentialConfiguration(
                 else -> throw IllegalStateException()
             }
             return CredentialConfiguration(
-                challenge,
-                SecureAreaConfigurationAndroidKeystore(
+                challenge = challenge,
+                keyAssertionRequired = false,
+                secureAreaConfiguration = SecureAreaConfigurationAndroidKeystore(
                     curve = curve.coseCurveIdentifier,
                     purposes = KeyPurpose.encodeSet(purposes),
                     useStrongBox = useStrongBox,
@@ -439,8 +441,9 @@ fun defaultCredentialConfiguration(
                 builder.put("passphraseConstraints", passphraseConstraints.toDataItem())
             }
             return CredentialConfiguration(
-                challenge,
-                SecureAreaConfigurationSoftware()
+                challenge = challenge,
+                keyAssertionRequired = false,
+                secureAreaConfiguration = SecureAreaConfigurationSoftware()
             )
         }
 
@@ -459,8 +462,9 @@ fun defaultCredentialConfiguration(
             val cloudSecureAreaId = (collectedEvidence["devmode_sa_cloud_setup_csa"] as EvidenceResponseSetupCloudSecureArea)
                 .cloudSecureAreaIdentifier
             return CredentialConfiguration(
-                challenge,
-                SecureAreaConfigurationCloud(
+                challenge = challenge,
+                keyAssertionRequired = false,
+                secureAreaConfiguration = SecureAreaConfigurationCloud(
                     purposes = KeyPurpose.encodeSet(purposes),
                     curve = EcCurve.P256.coseCurveIdentifier,
                     cloudSecureAreaId = cloudSecureAreaId,

identity/src/commonMain/kotlin/com/android/identity/device/DeviceAssertionMaker.kt

@@ -1,5 +1,7 @@
 package com.android.identity.device
 
 fun interface DeviceAssertionMaker {
-    suspend fun makeDeviceAssertion(assertion: Assertion): DeviceAssertion
+    suspend fun makeDeviceAssertion(
+        assertion: (clientId: String) -> Assertion
+    ): DeviceAssertion
 }

wallet/src/main/java/com/android/identity/issuance/remote/WalletServerProvider.kt

@@ -75,12 +75,12 @@ class WalletServerProvider(
 
     private val storage = StorageImpl(context, "wallet_servers")
 
-    val assertionMaker = DeviceAssertionMaker { assertion ->
+    val assertionMaker = DeviceAssertionMaker { assertionFactory ->
         val applicationSupportConnection = applicationSupportSupplier!!.getApplicationSupport()
         DeviceCheck.generateAssertion(
             secureArea = secureArea,
             deviceAttestationId = applicationSupportConnection.deviceAttestationId,
-            assertion = assertion
+            assertion = assertionFactory(applicationSupportConnection.clientId)
         )
     }
 

wallet/src/main/java/com/android/identity_credential/wallet/DocumentModel.kt

@@ -892,20 +892,22 @@ class DocumentModel(
                     )
                 )
             }
-            val applicationSupportConnection =
-                walletServerProvider.getApplicationSupportConnection()
-            val keysAssertion = walletServerProvider.assertionMaker.makeDeviceAssertion(
-                AssertionBindingKeys(
-                    publicKeys = credentialRequests.map { request ->
-                        request.secureAreaBoundKeyAttestation.publicKey
-                    },
-                    nonce = credConfig.challenge,
-                    clientId = applicationSupportConnection.clientId,
-                    keyStorage = listOf(),
-                    userAuthentication = listOf(),
-                    issuedAt = Clock.System.now()
-                )
-            )
+            val keysAssertion = if (credConfig.keyAssertionRequired) {
+                walletServerProvider.assertionMaker.makeDeviceAssertion { clientId ->
+                    AssertionBindingKeys(
+                        publicKeys = credentialRequests.map { request ->
+                            request.secureAreaBoundKeyAttestation.publicKey
+                        },
+                        nonce = credConfig.challenge,
+                        clientId = clientId,
+                        keyStorage = listOf(),
+                        userAuthentication = listOf(),
+                        issuedAt = Clock.System.now()
+                    )
+                }
+            } else {
+                null
+            }
             val challenges = requestCredentialsFlow.sendCredentials(
                 credentialRequests = credentialRequests,
                 keysAssertion = keysAssertion

wallet/src/test/java/com/android/identity/issuance/simple/SimpleIssuingAuthorityRequestCredentialsFlow.kt

@@ -23,7 +23,7 @@ class SimpleIssuingAuthorityRequestCredentialsFlow(
 
     override suspend fun sendCredentials(
         credentialRequests: List<CredentialRequest>,
-        keysAssertion: DeviceAssertion
+        keysAssertion: DeviceAssertion?
     ): List<KeyPossessionChallenge> {
         // TODO: should check attestations
         issuingAuthority.addCpoRequests(documentId, format, credentialRequests)

wallet/src/test/java/com/android/identity_credential/wallet/TestIssuingAuthority.kt

@@ -125,8 +125,9 @@ class TestIssuingAuthority: SimpleIssuingAuthority(EphemeralStorageEngine(), {})
         collectedEvidence: MutableMap<String, EvidenceResponse>
     ): CredentialConfiguration {
         return CredentialConfiguration(
-            ByteString(byteArrayOf(1, 2, 3)),
-            SecureAreaConfigurationSoftware()
+            challenge = ByteString(byteArrayOf(1, 2, 3)),
+            keyAssertionRequired = false,
+            secureAreaConfiguration = SecureAreaConfigurationSoftware()
         )
     }
 }