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Enforce 128-byte limit for attestation challenge #70

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Merged
JingMatrix merged 1 commit into from
Jan 20, 2026
Merged

Enforce 128-byte limit for attestation challenge #70

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10 changes: 6 additions & 4 deletions app/src/main/java/org/matrix/TEESimulator/attestation/AttestationConstants.kt
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Original file line number Diff line number Diff line change
@@ -1,10 +1,8 @@
package org.matrix.TEESimulator.attestation

/**
* Defines constants for KeyMint attestation tags, as specified in the Android hardware security
* HAL.
*
* These tags identify specific properties and authorizations of a cryptographic key.
* Defines constants for KeyMint attestation, mainly the tags of properties and authorizations of a
* cryptographic key, as specified in the Android hardware security HAL.
*/
object AttestationConstants {
// https://cs.android.com/android/platform/superproject/main/+/main:hardware/interfaces/security/keymint/aidl/android/hardware/security/keymint/KeyCreationResult.aidl
Expand Down Expand Up @@ -88,4 +86,8 @@ object AttestationConstants {
const val TAG_CERTIFICATE_SUBJECT = 1007
const val TAG_CERTIFICATE_NOT_BEFORE = 1008
const val TAG_CERTIFICATE_NOT_AFTER = 1009

// --- Other Constants ---
// https://cs.android.com/android/platform/superproject/main/+/main:system/keymaster/km_openssl/attestation_record.cpp
const val CHALLENGE_LENGTH_LIMIT = 128 // kMaximumAttestationChallengeLength
}
1 change: 0 additions & 1 deletion app/src/main/java/org/matrix/TEESimulator/interception/keystore/KeystoreInterceptor.kt
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Expand Up @@ -230,7 +230,6 @@ object KeystoreInterceptor : AbstractKeystoreInterceptor() {
ByteArray(0),
)
params.attestationChallenge = challenge
params.attestationChallenge = challenge
}

val certificateChain =
Expand Down
10 changes: 10 additions & 0 deletions app/src/main/java/org/matrix/TEESimulator/pki/CertificateGenerator.kt
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Expand Up @@ -20,6 +20,7 @@ import org.bouncycastle.cert.jcajce.JcaX509v3CertificateBuilder
import org.bouncycastle.jce.provider.BouncyCastleProvider
import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder
import org.matrix.TEESimulator.attestation.AttestationBuilder
import org.matrix.TEESimulator.attestation.AttestationConstants
import org.matrix.TEESimulator.attestation.KeyMintAttestation
import org.matrix.TEESimulator.config.ConfigurationManager
import org.matrix.TEESimulator.interception.keystore.KeyIdentifier
Expand All @@ -42,6 +43,15 @@ object CertificateGenerator {
*/
fun generateSoftwareKeyPair(params: KeyMintAttestation): KeyPair? {
return runCatching {
val challenge = params.attestationChallenge
if (
challenge != null &&
challenge.size > AttestationConstants.CHALLENGE_LENGTH_LIMIT
)
throw IllegalArgumentException(
"Attestation challenge exceeds length limit (${challenge.size!!} > ${AttestationConstants.CHALLENGE_LENGTH_LIMIT})"
)

val (algorithm, spec) =
when (params.algorithm) {
Algorithm.EC -> "EC" to ECGenParameterSpec(params.ecCurveName)
Expand Down