rework key attestation key comparison

CHANGELOG.md

@@ -1,3 +1,10 @@
+## 2.1.1
+- Rely on [Signum](https://github.com/a-sit-plus/signum) to transcode public keys
+- Add working `hashCode` and `equals` to `AttestationResult` and `KeyAttestation`
+- Rework key attestation key comparison
+  - Try all encodings for public keys
+  - Throw exception with *very* detailed message when key attestation runs into a logical error
+
 ## 2.1.0
 - Rebrand to _WARDEN_
 - Dependency Updates

gradle.properties

@@ -1,3 +1,3 @@
 jdk.version=17
-artifactVersion=2.1.0
+artifactVersion=2.1.1
 androidAttestationVersion=1.6.0

warden/build.gradle.kts

@@ -24,10 +24,10 @@ sourceSets.test {
 dependencies {
     api("at.asitplus:warden-roboto:$androidAttestationVersion")
     api(datetime())
+    implementation("at.asitplus.signum:indispensable:3.6.0")
     implementation("ch.veehait.devicecheck:devicecheck-appattest:0.9.6")
     implementation("com.fasterxml.jackson.dataformat:jackson-dataformat-cbor:2.14.2")
     implementation("net.swiftzer.semver:semver:1.2.0")
-    implementation(bouncycastle("bcpkix", "jdk18on"))
     implementation("org.slf4j:slf4j-api:1.7.36")
     implementation("com.fasterxml.jackson.module:jackson-module-kotlin:2.14.2")
 

warden/src/main/kotlin/AttestationService.kt

@@ -4,6 +4,8 @@ import at.asitplus.attestation.AttestationException
 import at.asitplus.attestation.IOSAttestationConfiguration.AppData
 import at.asitplus.attestation.android.*
 import at.asitplus.attestation.android.exceptions.AttestationValueException
+import at.asitplus.signum.indispensable.CryptoPublicKey
+import at.asitplus.signum.indispensable.fromJcaPublicKey
 import ch.veehait.devicecheck.appattest.assertion.Assertion
 import ch.veehait.devicecheck.appattest.attestation.ValidatedAttestation
 import com.google.android.attestation.AttestationApplicationId
@@ -12,7 +14,6 @@ import net.swiftzer.semver.SemVer
 import org.slf4j.LoggerFactory
 import java.security.PublicKey
 import java.security.cert.X509Certificate
-import java.security.interfaces.ECPublicKey
 import java.util.*
 import kotlin.jvm.optionals.getOrNull
 import at.asitplus.attestation.AttestationException as AttException
@@ -256,46 +257,69 @@ abstract class AttestationService {
         attestationProof: List<ByteArray>,
         expectedChallenge: ByteArray,
         keyToBeAttested: T
-    ): KeyAttestation<T> =
-        when (val firstTry = verifyAttestation(attestationProof, expectedChallenge, keyToBeAttested.encoded)) {
-            is AttestationResult.Android -> {
-                if (keyToBeAttested.encoded contentEquals firstTry.attestationCertificate.publicKey.encoded) KeyAttestation(
-                    keyToBeAttested,
-                    firstTry
-                )
-                else {
-                    ("Android attestation failed: keyToBeAttested (${keyToBeAttested.encoded.encodeBase64()}) does not match " +
-                            "key from attestation certificate: ${firstTry.attestationCertificate.publicKey.encoded.encodeBase64()}").let {
-                        KeyAttestation(
-                            null,
-                            AttestationResult.Error(
-                                explanation = it,
-                                cause = AttException.Content.Android(
-                                    it,
-                                    AttestationValueException(
-                                        it,
-                                        cause = null,
-                                        reason = AttestationValueException.Reason.APP_UNEXPECTED
-                                    )
-                                )
-                            )
-                        )
+    ): KeyAttestation<T> {
+        when (val firstTry = verifyAttestation(
+            attestationProof,
+            expectedChallenge,
+            keyToBeAttested.encoded
+        )) {
+            is AttestationResult.Android -> return processAndroidAttestationResult(keyToBeAttested, firstTry)
+
+            is AttestationResult.Error -> {
+
+                // try all different key encodings
+                // not the most efficient way, but doing it like this won't involve any guesswork at all
+                keyToBeAttested.transcodeToAllFormats().forEach {
+                    when (val secondTry =
+                        kotlin.runCatching { verifyAttestation(attestationProof, expectedChallenge, it) }
+                            .getOrElse { return KeyAttestation(null, firstTry) }) {
+
+                        is AttestationResult.Android ->
+                            throw logicalError(keyToBeAttested, attestationProof, expectedChallenge)
+
+                        is AttestationResult.Error -> {} //try again, IOS could have encoded it differently
+
+                        //if this works, perfect!
+                        is AttestationResult.IOS -> return KeyAttestation(keyToBeAttested, secondTry)
                     }
                 }
+                //if no encoding works, then it should just fail
+                return KeyAttestation(null, firstTry)
             }
 
-            is AttestationResult.Error -> when (val secondTry =
-                kotlin.runCatching {
-                    verifyAttestation(attestationProof, expectedChallenge, (keyToBeAttested as ECPublicKey).toAnsi())
-                }.getOrElse { return KeyAttestation(null, firstTry) }) {
-                is AttestationResult.Android -> throw RuntimeException("WTF?")
-                is AttestationResult.Error -> KeyAttestation(null, firstTry)
-                is AttestationResult.IOS -> KeyAttestation(keyToBeAttested, secondTry)
-            }
+            is AttestationResult.IOS -> return KeyAttestation(keyToBeAttested, firstTry)
+        }
+    }
 
-            is AttestationResult.IOS -> KeyAttestation(keyToBeAttested, firstTry)
+    private fun <T : PublicKey> processAndroidAttestationResult(
+        keyToBeAttested: T,
+        firstTry: AttestationResult.Android
+    ): KeyAttestation<T> =
+        if (CryptoPublicKey.fromJcaPublicKey(keyToBeAttested) == CryptoPublicKey.fromJcaPublicKey(
+                firstTry.attestationCertificate.publicKey
+            )
+        ) KeyAttestation(keyToBeAttested, firstTry)
+        else {
+            ("Android attestation failed: keyToBeAttested (${keyToBeAttested.encoded.encodeBase64()}) does not match " +
+                    "key from attestation certificate: ${firstTry.attestationCertificate.publicKey.encoded.encodeBase64()}").let {
+                KeyAttestation(
+                    null,
+                    AttestationResult.Error(
+                        explanation = it,
+                        cause = AttException.Content.Android(
+                            it,
+                            AttestationValueException(
+                                it,
+                                cause = null,
+                                reason = AttestationValueException.Reason.APP_UNEXPECTED
+                            )
+                        )
+                    )
+                )
+            }
         }
 
+
     /** Same as [verifyKeyAttestation], but taking an encoded (either ANSI X9.63 or DER) publix key as a byte array
      * @see verifyKeyAttestation
      */
@@ -435,6 +459,22 @@ sealed class AttestationResult {
                         }"
                     }
         }
+
+        override fun equals(other: Any?): Boolean {
+            if (this === other) return true
+            if (other !is Android) return false
+
+            if (attestationCertificateChain.map { it.encoded.encodeBase64() } != other.attestationCertificateChain.map { it.encoded.encodeBase64() }) return false
+            if (androidDetails != other.androidDetails) return false
+
+            return true
+        }
+
+        override fun hashCode(): Int {
+            var result = attestationCertificateChain.map { it.encoded.contentHashCode() }.hashCode()
+            result = 31 * result + androidDetails.hashCode()
+            return result
+        }
     }
 
 
@@ -466,6 +506,25 @@ sealed class AttestationResult {
             override val iosDetails = "NOOP"
         }
 
+        override fun equals(other: Any?): Boolean {
+            if (this === other) return true
+            if (other !is IOS) return false
+
+            if (clientData != null) {
+                if (other.clientData == null) return false
+                if (!clientData.contentEquals(other.clientData)) return false
+            } else if (other.clientData != null) return false
+            if (iosDetails != other.iosDetails) return false
+
+            return true
+        }
+
+        override fun hashCode(): Int {
+            var result = clientData?.contentHashCode() ?: 0
+            result = 31 * result + iosDetails.hashCode()
+            return result
+        }
+
         /**
          * Represents an attestation verification failure. Always contains an  [explanation] about what went wrong.
          */
@@ -499,6 +558,24 @@ data class KeyAttestation<T : PublicKey> internal constructor(
         else {
             onError(details as AttestationResult.Error)
         }
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is KeyAttestation<*>) return false
+
+        if (!attestedPublicKey?.encoded.contentEquals(other.attestedPublicKey?.encoded)) return false
+        if (details != other.details) return false
+
+        return true
+    }
+
+    override fun hashCode(): Int {
+        var result = attestedPublicKey?.encoded?.contentHashCode() ?: 0
+        result = 31 * result + details.hashCode()
+        return result
+    }
+
+
 }
 
 /**

warden/src/main/kotlin/Extensions.kt

@@ -1,5 +1,8 @@
 package at.asitplus.attestation
 
+import at.asitplus.signum.indispensable.CryptoPublicKey
+import at.asitplus.signum.indispensable.fromJcaPublicKey
+import at.asitplus.signum.indispensable.getJcaPublicKey
 import kotlinx.datetime.Clock
 import kotlinx.datetime.toJavaInstant
 import kotlinx.datetime.toKotlinInstant
@@ -39,6 +42,17 @@ data class AttestationObject(
     )
 }
 
+internal fun PublicKey.transcodeToAllFormats() = CryptoPublicKey.fromJcaPublicKey(this).getOrThrow().let {
+    listOf(
+        it.iosEncoded,
+        (it as CryptoPublicKey.EC).copy(
+            it.publicPoint,
+            preferCompressedRepresentation = !it.preferCompressedRepresentation
+        ).iosEncoded,
+        it.encodeToDer()
+    )
+}
+
 internal fun String.decodeBase64ToArray() = Base64.decode(this)
 
 internal fun ByteArray.encodeBase64() = Base64.toBase64String(this)
@@ -58,25 +72,11 @@ internal fun Clock.toJavaClock(): java.time.Clock =
 
 internal fun kotlinx.datetime.Instant.toJavaDate() = Date.from(toJavaInstant())
 
-fun ECPublicKey.toAnsi() = let {
-    val xFromBc = it.w.affineX.toByteArray().ensureSize(32)
-    val yFromBc = it.w.affineY.toByteArray().ensureSize(32)
-    byteArrayOf(0x04) + xFromBc + yFromBc
-}
-
 fun ByteArray.parseToPublicKey(): PublicKey =
     try {
-        (if (size < 1024) ecKeyFactory else rsaKeyFactory).generatePublic(X509EncodedKeySpec(this))
+       CryptoPublicKey.decodeFromDer(this).getJcaPublicKey().getOrThrow()
     } catch (e: Throwable) {
-        if (first() != 0x04.toByte()) throw InvalidKeySpecException("Encoded public key does not start with 0x04")
-
-        val parameterSpec = ECNamedCurveTable.getParameterSpec("P-256")
-        val ecPoint = parameterSpec.curve.createPoint(
-            BigInteger(1, sliceArray(1..<33)),
-            BigInteger(1, takeLast(32).toByteArray())
-        )
-        val ecPublicKeySpec = org.bouncycastle.jce.spec.ECPublicKeySpec(ecPoint, parameterSpec)
-        JCEECPublicKey("EC", ecPublicKeySpec)
+       CryptoPublicKey.fromIosEncoded(this).getJcaPublicKey().getOrThrow()
     }
 
 /**

warden/src/main/kotlin/Throwables.kt

@@ -4,6 +4,8 @@ import at.asitplus.attestation.AttestationException.Certificate
 import at.asitplus.attestation.AttestationException.Content
 import at.asitplus.attestation.android.exceptions.AndroidAttestationException
 import at.asitplus.attestation.android.exceptions.AttestationValueException
+import kotlinx.datetime.Clock
+import java.security.PublicKey
 
 
 /**
@@ -174,6 +176,15 @@ class IosAttestationException(msg: String? = null, cause: Throwable? = null, val
          */
         APP_UNEXPECTED,
 
-
     }
-}
+}
+
+internal fun <T : PublicKey> logicalError(
+    keyToBeAttested: T,
+    attestationProof: List<ByteArray>,
+    expectedChallenge: ByteArray
+) = RuntimeException("Logical Error attesting key ${
+    keyToBeAttested.encoded.encodeBase64()
+} for attestation proof ${
+    attestationProof.joinToString { it.encodeBase64() }
+} with challenge ${expectedChallenge.encodeBase64()} at ${Clock.System.now()}")

warden/src/test/kotlin/KeyConversionTests.kt

@@ -1,6 +1,7 @@
 import at.asitplus.attestation.decodeBase64ToArray
 import at.asitplus.attestation.parseToPublicKey
-import at.asitplus.attestation.toAnsi
+import at.asitplus.signum.indispensable.CryptoPublicKey
+import at.asitplus.signum.indispensable.fromJcaPublicKey
 import io.kotest.core.spec.style.FreeSpec
 import io.kotest.matchers.shouldBe
 import java.security.interfaces.ECPublicKey
@@ -12,9 +13,9 @@ class KeyConversionTests : FreeSpec({
         "it should be parsable" - {
             val parsedKey = x509Key.parseToPublicKey()
             "and encodable to ANSI X9.62" - {
-                val ansBytes = (parsedKey as ECPublicKey).toAnsi()
+                val ansiBytes = CryptoPublicKey.EC.fromJcaPublicKey(parsedKey as ECPublicKey).getOrThrow().iosEncoded
                 "and decodable" - {
-                    val decoded = ansBytes.parseToPublicKey()
+                    val decoded = ansiBytes.parseToPublicKey()
                     "to match the original X5095-encoded key" {
                         decoded.encoded shouldBe x509Key
                     }

warden/src/test/kotlin/DefaultAttestationServiceTest.kt → warden/src/test/kotlin/WardenTests.kt

@@ -124,10 +124,13 @@ class WardenTest : FreeSpec() {
                         sandbox = true
                     )
                 ), FixedTimeClock(2023u, 9u, 11u)
-            ).verifyKeyAttestation(
-                iosIDA.attestationProof, iosIDA.challenge, iosIDA.publicKey!!
             ).apply {
-                isSuccess.shouldBeTrue()
+                verifyKeyAttestation(
+                    iosIDA.attestationProof, iosIDA.challenge, iosIDA.publicKey!!
+                ).apply {
+                    isSuccess.shouldBeTrue()
+                    verifyKeyAttestation( iosIDA.attestationProof, iosIDA.challenge, iosIDA.pubKeyB64!!.decodeBase64ToArray()) shouldBe this
+                }
             }
         }
 
@@ -157,15 +160,20 @@ class WardenTest : FreeSpec() {
                                     }
                                 }
                                 "Key Attestation" {
-                                    verifyKeyAttestation(
+                                    (verifyKeyAttestation(
                                         recordedAttestation.attestationProof,
                                         recordedAttestation.challenge,
                                         recordedAttestation.publicKey!!
-                                    ).apply {
-                                        also { println(it) }
-                                        isSuccess.shouldBeTrue()
-                                        attestedPublicKey.shouldNotBeNull()
-                                        attestedPublicKey!!.encoded shouldBe recordedAttestation.publicKey?.encoded
+                                    ) to verifyKeyAttestation(
+                                        recordedAttestation.attestationProof,
+                                        recordedAttestation.challenge,
+                                        recordedAttestation.pubKeyB64!!.decodeBase64ToArray()
+                                    )).apply {
+                                        also { println(it.first) }
+                                        first.isSuccess.shouldBeTrue()
+                                        first.attestedPublicKey.shouldNotBeNull()
+                                        first.attestedPublicKey!!.encoded shouldBe recordedAttestation.publicKey?.encoded
+                                        first shouldBe second
                                     }
                                 }
                             }