drop check for OEM unlocking until extended API

Android 15 QPR2 no longer permits checking this system property as an
unprivileged app. GrapheneOS will be reimplementing it as part of the
extended API for Auditor information.

Author: thestinger

app/src/main/java/app/attestation/auditor/AttestationProtocol.java

@@ -151,6 +151,7 @@ class AttestationProtocol {
     // short autoRebootMinutes (-1 for unknown)
     // byte portSecurityMode (-1 for unknown)
     // byte userCount (-1 for unknown)
+    // byte oemUnlockAllowed (-1 for unknown)
     // }
     // byte[] signature (rest of message)
     //
@@ -159,6 +160,7 @@ class AttestationProtocol {
     // 6: autoRebootMinutes added
     // 6: portSecurityMode added
     // 6: userCount added
+    // 6: oemUnlockAllowed added
     //
     // n/a
     //
@@ -214,7 +216,7 @@ class AttestationProtocol {
     private static final int OS_ENFORCED_FLAGS_ENROLLED_BIOMETRICS = 1 << 5;
     private static final int OS_ENFORCED_FLAGS_DENY_NEW_USB = 1 << 6; // obsolete since version 86
     private static final int OS_ENFORCED_FLAGS_DEVICE_ADMIN_NON_SYSTEM = 1 << 7;
-    private static final int OS_ENFORCED_FLAGS_OEM_UNLOCK_ALLOWED = 1 << 8;
+    private static final int OS_ENFORCED_FLAGS_OEM_UNLOCK_ALLOWED = 1 << 8; // obsolete since version 89
     private static final int OS_ENFORCED_FLAGS_SYSTEM_USER = 1 << 9;
     private static final int OS_ENFORCED_FLAGS_ALL =
             OS_ENFORCED_FLAGS_USER_PROFILE_SECURE |
@@ -961,7 +963,7 @@ private static VerificationResult verify(final Context context, final byte[] fin
             final boolean accessibility, final boolean deviceAdmin,
             final boolean deviceAdminNonSystem, final boolean adbEnabled,
             final boolean addUsersWhenLocked, final boolean enrolledBiometrics,
-            final boolean oemUnlockAllowed, final boolean systemUser)
+            final boolean systemUser)
             throws GeneralSecurityException {
         final String fingerprintHex = BaseEncoding.base16().encode(fingerprint);
         final byte[] currentFingerprint = getFingerprint(attestationCertificates[0]);
@@ -1132,8 +1134,6 @@ private static VerificationResult verify(final Context context, final byte[] fin
                 toYesNoString(context, adbEnabled)));
         osEnforced.append(context.getString(R.string.add_users_when_locked,
                 toYesNoString(context, addUsersWhenLocked)));
-        osEnforced.append(context.getString(R.string.oem_unlock_allowed,
-                toYesNoString(context, oemUnlockAllowed)));
         osEnforced.append(context.getString(R.string.system_user,
                 toYesNoString(context, systemUser)));
 
@@ -1227,7 +1227,6 @@ static VerificationResult verifySerialized(final Context context, final byte[] a
         final boolean adbEnabled = (osEnforcedFlags & OS_ENFORCED_FLAGS_ADB_ENABLED) != 0;
         final boolean addUsersWhenLocked = (osEnforcedFlags & OS_ENFORCED_FLAGS_ADD_USERS_WHEN_LOCKED) != 0;
         final boolean enrolledBiometrics = (osEnforcedFlags & OS_ENFORCED_FLAGS_ENROLLED_BIOMETRICS) != 0;
-        final boolean oemUnlockAllowed = (osEnforcedFlags & OS_ENFORCED_FLAGS_OEM_UNLOCK_ALLOWED) != 0;
         final boolean systemUser = (osEnforcedFlags & OS_ENFORCED_FLAGS_SYSTEM_USER) != 0;
 
         if (deviceAdminNonSystem && !deviceAdmin) {
@@ -1238,6 +1237,7 @@ static VerificationResult verifySerialized(final Context context, final byte[] a
             final short autoRebootMinutes = deserializer.getShort();
             final byte portSecurityMode = deserializer.get();
             final byte userCount = deserializer.get();
+            final byte oemUnlockAllowed = deserializer.get();
         }
 
         final int signatureLength = deserializer.remaining();
@@ -1250,7 +1250,7 @@ static VerificationResult verifySerialized(final Context context, final byte[] a
         final byte[] challenge = Arrays.copyOfRange(challengeMessage, 1 + RANDOM_TOKEN_LENGTH, 1 + RANDOM_TOKEN_LENGTH * 2);
         return verify(context, fingerprint, challenge, deserializer.asReadOnlyBuffer(), signature,
                 certificates, userProfileSecure, accessibility, deviceAdmin, deviceAdminNonSystem,
-                adbEnabled, addUsersWhenLocked, enrolledBiometrics, oemUnlockAllowed, systemUser);
+                adbEnabled, addUsersWhenLocked, enrolledBiometrics, systemUser);
     }
 
     record AttestationResult(boolean pairing, byte[] serialized) {}
@@ -1430,9 +1430,6 @@ static AttestationResult generateSerialized(final Context context, final byte[]
             final boolean addUsersWhenLocked = Settings.Global.getInt(context.getContentResolver(),
                     ADD_USERS_WHEN_LOCKED, 0) != 0;
 
-            final String oemUnlockAllowedValue = SystemProperties.get("sys.oem_unlock_allowed", "0");
-            final boolean oemUnlockAllowed = oemUnlockAllowedValue.equals("1");
-
             final UserManager userManager = context.getSystemService(UserManager.class);
             final boolean systemUser = userManager.isSystemUser();
 
@@ -1480,9 +1477,6 @@ static AttestationResult generateSerialized(final Context context, final byte[]
             if (enrolledBiometrics) {
                 osEnforcedFlags |= OS_ENFORCED_FLAGS_ENROLLED_BIOMETRICS;
             }
-            if (oemUnlockAllowed) {
-                osEnforcedFlags |= OS_ENFORCED_FLAGS_OEM_UNLOCK_ALLOWED;
-            }
             if (systemUser) {
                 osEnforcedFlags |= OS_ENFORCED_FLAGS_SYSTEM_USER;
             }
@@ -1497,6 +1491,9 @@ static AttestationResult generateSerialized(final Context context, final byte[]
 
                 final byte userCount = 0;
                 serializer.put(userCount);
+
+                final byte oemUnlockAllowed = 0;
+                serializer.put(oemUnlockAllowed);
             }
 
             final ByteBuffer message = serializer.duplicate();