UICC carrier privileges

Android 5.1 introduced a mechanism to grant special privileges for APIs relevant to the owners of universal integrated circuit card (UICC) apps. The Android platform loads certificates stored on a UICC and grants permission to apps signed by these certificates to make calls to a handful of special APIs.

Android 7.0 extended this feature to support other storage sources for UICC carrier privilege rules, dramatically increasing the number of carriers that can use the APIs. For an API reference, see CarrierConfigManager; for instructions, see Carrier Configuration.

Carriers have full control of the UICC, so this mechanism provides a secure and flexible way to manage apps from the mobile network operator (MNO) hosted on generic app distribution channels (such as Google Play) while retaining special privileges on devices and without the need to sign apps with the per-device platform certificate or preinstall as a system app.

Rules on UICC

Storage on the UICC is compatible with the GlobalPlatform Secure Element Access Control specification. The app identifier (AID) on the card is A00000015141434C00, and the standard GET DATA command is used to fetch rules stored on the card. You can update these rules through card over-the-air (OTA) updates.

Data hierarchy

UICC rules use the following data hierarchy (the two-character letter and number combination in parentheses is the object tag). Each rule is REF-AR-DO (E2) and consists of a concatenation of REF-DO and AR-DO:

REF-DO (E1) contains DeviceAppID-REF-DO or a concatenation of DeviceAppID-REF-DO and PKG-REF-DO.
- DeviceAppID-REF-DO (C1) stores the SHA-1 (20 bytes) or SHA-256 (32 bytes) signature of the certificate.
- PKG-REF-DO (CA) is the full package name string defined in the manifest, ASCII encoded, max length 127 bytes.
AR-DO (E3) is extended to include PERM-AR-DO (DB), which is an 8-byte bit mask representing 64 separate permissions.

If PKG-REF-DO isn't present, any app signed by the certificate is granted access; otherwise both the certificate and the package name need to match.

Rule example

The app name is com.google.android.apps.myapp and the SHA-1 certificate in hex string is:

AB:CD:92:CB:B1:56:B2:80:FA:4E:14:29:A6:EC:EE:B6:E5:C1:BF:E4

The rule on UICC in hex string is:

E243 <= 43 is value length in hex
  E135
    C114 ABCD92CBB156B280FA4E1429A6ECEEB6E5C1BFE4
    CA1D 636F6D2E676F6F676C652E616E64726F69642E617070732E6D79617070
  E30A
    DB08 0000000000000001

Access rule file support

Android 7.0 adds support for reading carrier privilege rules from the access rule file (ARF).

The Android platform first attempts to select the access rule application (ARA) AID A00000015141434C00. If it doesn't find the AID on the UICC, it falls back to ARF by selecting PKCS15 AID A000000063504B43532D3135. Android then reads the access control rules file (ACRF) at 0x4300 and looks for entries with AID FFFFFFFFFFFF. Entries with different AIDs are ignored, so rules for other use cases can coexist.

Example ACRF content in hex string:

30 10 A0 08 04 06 FF FF FF FF FF FF 30 04 04 02 43 10

Example access control conditions file (ACCF) content:

30 16 04 14 61 ED 37 7E 85 D3 86 A8 DF EE 6B 86 4B D8 5B 0B FA A5 AF 81

In the example above, 0x4310 is the address for ACCF, which contains the certificate hash 61:ED:37:7E:85:D3:86:A8:DF:EE:6B:86:4B:D8:5B:0B:FA:A5:AF:81. Apps signed by this certificate are granted carrier privileges.

Enabled APIs

Android supports the following APIs.

TelephonyManager

Method to let the carrier app to ask UICC for a challenge/response: getIccAuthentication.
Method to check whether the calling app has been granted carrier privileges: hasCarrierPrivileges.
Methods to override brand and number:
- setOperatorBrandOverride
- setLine1NumberForDisplay
- setVoiceMailNumber
Methods for direct UICC communication:
- iccOpenLogicalChannel
- iccCloseLogicalChannel
- iccExchangeSimIO
- iccTransmitApduLogicalChannel
- iccTransmitApduBasicChannel
- sendEnvelopeWithStatus
Method to set device mode to global: setPreferredNetworkTypeToGlobal.
Methods to get the device or network identities:
- International Mobile Equipment Identity (IMEI): getImei
- Mobile Equipment Identifier (MEID): getMeid
- Network Access Identifier (NAI): getNai
- SIM serial number: getSimSerialNumber
Method to get the carrier configuration: getCarrierConfig
Method to get the network type for data transmission: getDataNetworkType
Method to get the network type for voice service: getVoiceNetworkType
Methods to get the information about the UICC SIM (USIM) app:
- SIM serial number: getSimSerialNumber
- Card information: getUiccCardsInfo
- GID1 (group ID level1): getGroupIdLevel1
- Phone number string for line 1: getLine1Number
- Forbidden public land mobile network (PLMN): getForbiddenPlmns
- Equivalent home PLMN: getEquivalentHomePlmns
Methods to get or set voicemail number:
- getVoiceMailNumber
- setVoiceMailNumber
Method to send special dialer code: sendDialerSpecialCode
Method to reset the radio modem: rebootModem
Methods to get or set network selection modes:
- getNetworkSelectionMode
- setNetworkSelectionModeAutomatic
- setNetworkSelectionModeManual
- isManualNetworkSelectionAllowed
Method to request a network scan: requestNetworkScan
Methods to get or set the allowed/preferred network types:
- setAllowedNetworkTypesForReason
- getAllowedNetworkTypesForReason
- setPreferredNetworkTypeToGlobal
Methods to check if the mobile data or roaming is enabled per user settings:
- isDataEnabled
- isDataRoamingEnabled
Methods to check or set data connection with reason:
- setDataEnabledForReason
- isDataEnabledForReason
Method to get the emergency number list: getEmergencyNumberList
Methods to control the opportunistic networks:
- setPreferredOpportunisticDataSubscription
- getPreferredOpportunisticDataSubscription
- updateAvailableNetworks
Methods to set or clear cellular signal strength update request:
- setSignalStrengthUpdateRequest
- clearSignalStrengthUpdateRequest

TelephonyCallback

TelephonyCallback has interfaces with a callback method to notify the calling app when the registered states change:

The message waiting indicator changed: onMessageWaitingIndicatorChanged
The call forwarding indicator changed: onCallForwardingIndicatorChanged
The IP multimedia system (IMS) call disconnection cause changed: onImsCallDisconnectCauseChanged
The precise data connection state changed: onPreciseDataConnectionStateChanged
The current emergency number list changed: onEmergencyNumberListChanged
The active data subscription ID changed: onActiveDataSubscriptionIdChanged
The carrier network changed: onCarrierNetworkChange
The network registration or a location/routing/tracking area update failed: onRegistrationFailed
The barring information change: onBarringInfoChanged
The current physical channel configuration changed: onPhysicalChannelConfigChanged

SubscriptionManager

Methods to get various subscription information:
Method to get the number of active subscriptions: getActiveSubscriptionInfoCount
Methods to manage subscription groups:
Methods to get or set the description of the billing relationship plan between a carrier and a specific subscriber:
- getSubscriptionPlans
- setSubscriptionPlans
Method to temporarily override the billing relationship plan between a carrier and a specific subscriber to be considered unmetered: setSubscriptionOverrideUnmetered
Method to temporarily override the billing relationship plan between a carrier and a specific subscriber to be considered congested: setSubscriptionOverrideCongested
Method to check whether the app with the given context is authorized to manage the given subscription according to its metadata: canManageSubscription

SmsManager

Method to let the caller create new incoming SMS messages: injectSmsPdu.
Method to send a text based SMS message without writing into the SMS provider: sendTextMessageWithoutPersisting

CarrierConfigManager

Method to notify configuration changed: notifyConfigChangedForSubId.
Method to get carrier configuration for the default subscription: getConfig
Method to get carrier configuration for the specified subscription: getConfigForSubId

For instructions, see Carrier Configuration.

BugreportManager

Method to start a connectivity bug report, which is a specialized version of the bug report that includes only information for debugging connectivity related issues: startConnectivityBugreport

NetworkStatsManager

Method to query network usage summary: querySummary
Method to query network usage history: queryDetails
Methods to register or unregister network usage callback:
- registerUsageCallback
- unregisterUsageCallback

ImsMmTelManager

Methods to register or unregister IMS MmTel registration callback:
- registerImsRegistrationCallback
- unregisterImsRegistrationCallback

ImsRcsManager

Methods to register or unregister IMS RCS registration callback:
- registerImsRegistrationCallback
- unregisterImsRegistrationCallback
Methods to get IMS registration state or transport type:
- getRegistrationState
- getRegistrationTransportType

ProvisioningManager

Methods to register and unregister IMS feature provisioning updates callback:
- registerFeatureProvisioningChangedCallback
- unregisterFeatureProvisioningChangedCallback
Methods related to the provisioning status for IMS MmTel or RCS capability:

EuiccManager

Method to switch to (enable) the given subscription: switchToSubscription

CarrierMessagingService

Service that receives calls from the system when new SMS and MMS are sent or received. To extend this class, declare the service in your manifest file with the android.Manifest.permission#BIND_CARRIER_MESSAGING_SERVICE permission and include an intent filter with the #SERVICE_INTERFACE action. Methods include:

Method to filter inbound SMS messages: onFilterSms
Method to intercept text SMS messages sent from the device: onSendTextSms
Method to intercept binary SMS messages sent from the device: onSendDataSms
Method to intercept long SMS messages sent from the device: onSendMultipartTextSms
Method to intercept MMS messages sent from the device: onSendMms
Method to download MMS messages received: onDownloadMms

CarrierService

Service that exposes carrier-specific functionalities to the system. To extend this class, declare the service in the app manifest file with the android.Manifest.permission#BIND_CARRIER_SERVICES permission and include an intent filter with the CARRIER_SERVICE_INTERFACE action. If the service has a long-lived binding, set android.service.carrier.LONG_LIVED_BINDING to true in the metadata of the service.

The platform binds CarrierService with special flags to let the carrier service process run in a special app standby bucket. This exempts the carrier service app from app idle restriction and makes it more likely to stay alive when device memory is low. However, if the carrier service app crashes for any reason, it loses all above privileges until the app restarts and the binding is reestablished. So it's critical to keep the carrier service app stable.

Methods in CarrierService include:

To override and set the carrier specific configurations: onLoadConfig
To inform the system of an intentional upcoming carrier network change by the carrier app: notifyCarrierNetworkChange

Telephony provider

Content provider APIs to allow modifications (insert, delete, update, query) to the telephony database. Values fields are defined at Telephony.Carriers; for more details, refer to the Telephony class reference

WifiNetworkSuggestion

When building a WifiNetworkSuggestion object, use the following methods to set a subscription ID or a subscription group:

Method to set a subscription ID: setSubscriptionId
Metohd to set a subscription group: setSubscriptionGroup

Android platform

On a detected UICC, the platform constructs internal UICC objects that include carrier privilege rules as part of the UICC. UiccCarrierPrivilegeRules.java loads rules, parses them from the UICC card, and caches them in memory. When a privilege check is needed, UiccCarrierPrivilegeRules compares the caller certificate with its own rules one by one. If the UICC is removed, the rules are destroyed along with the UICC object.

Validation

To validate the implementation through Compatibility Test Suite (CTS) using CtsCarrierApiTestCases.apk, you must have a developer UICC with the correct UICC rules or ARF support. Ask the SIM card vendor of your choice to prepare a developer UICC with the right ARF as described in this section and use that UICC to run the tests. The UICC doesn't require active cellular service to pass CTS tests.

Prepare the UICC

For Android 11 and lower, CtsCarrierApiTestCases.apk is signed by aosp-testkey, with hash value 61:ED:37:7E:85:D3:86:A8:DF:EE:6B:86:4B:D8:5B:0B:FA:A5:AF:81.

Starting in Android 12, CtsCarrierApiTestCases.apk is signed by cts-uicc-2021-testkey, hash value CE:7B:2B:47:AE:2B:75:52:C8:F9:2C:C2:91:24:27:98:83:04:1F:B6:23:A5:F1:94:A8:2C:9B:F1:5D:49:2A:A0.

To run CTS carrier API tests in Android 12, the device needs to use a SIM with CTS carrier privileges meeting the requirements specified in the latest version of the third-party GSMA TS.48 Test Profile specification.

The same SIM can also be used for versions prior to Android 12.

Modify the CTS SIM profile

Add: CTS carrier privileges in access rule app master (ARA-M) or ARF. Both signatures must be encoded in the carrier privilege rules:
1. Hash1(SHA1): 61:ED:37:7E:85:D3:86:A8:DF:EE:6B:86:4B:D8:5B:0B:FA:A5:AF:81
2. Hash2(SHA256): CE:7B:2B:47:AE:2B:75:52:C8:F9:2C:C2:91:24:27:98:83:04:1F:B6:23:A5:F1:94:A8:2C:9B:F1:5D:49:2A:A0
Note: If using ARF, the ACRF with AID: FFFFFFFFFFFF must point to a single ACCF that encodes both Hash1 and Hash2.
Create: ADF USIM elementary files (EFs) not present in TS.48 and needed for CTS:
1. EF_MBDN (6FC7), record size: 28, record number: 4
  - Content
    1. Rec1: 566F696365204D61696CFFFFFFFF06915155555555FF…FF
    2. Rec2-n: FF…FF
2. EF_EXT6 (6FC8), record size:13, record number: 1
  - Content: 00FF…FF
    1. EF_MBI (6FC9), record size: 4, record number: 1
  - Content: Rec1: 01010101
    1. EF_MWIS (6FCA), record size: 5, record number: 1
  - Content: 0000000000
Modify: USIM service table: Enable services n°47, n°48
1. EF_UST (6F38)
  - Content: 9EFFBF1DFFFE0083410310010400406E01
Modify: DF-5GS and DF-SAIP files
1. DF-5GS - EF_5GS3GPPLOCI (USIM/5FC0/4F01)
  - Content: FFFFFFFFFFFFFFFFFFFFFFFFFF42F618FFFFFE01
2. DF-5GS - EF_5GSN3GPPLOCI (USIM/5FC0/4F02)
  - Content: FFFFFFFFFFFFFFFFFFFFFFFFFF42F618FFFFFE01
3. DF-5GS - EF SUCI_Calc_Info (USIM/5FC0/4F07)
  - Content: A0020000FF…FF
4. DF-SAIP - EF SUCI_Calc_Info_USIM (USIM/5FD0/4F01)
  - Content: A0020000FF…FF
Modify: Use the carrier name string Android CTS in respective EFs containing this designation:
1. EF_SPN (USIM/6F46)
  - Content: 01416E64726F696420435453FF..FF
2. EF_PNN (USIM/6FC5)
  - Content: Rec1 430B83413759FE4E934143EA14FF..FF

Match the test profile structure

Download and match the latest version of the following generic test profile structures. These profiles won't have the CTS Carrier Privilege rule personalized or other modifications listed above.

Run tests

For convenience, CTS supports a device token that restricts tests to run only on devices configured with the same token. Carrier API CTS tests support the device token sim-card-with-certs. For example, the following device token restricts carrier API tests to run only on device abcd1234:

cts-tradefed run cts  --device-token abcd1234:sim-card-with-certs

When running a test without using a device token, the test runs on all devices.

FAQ

How can certificates be updated on the UICC?

A: Use the existing card OTA update mechanism.

Can UICC coexist with other rules?

A: It's fine to have other security rules on the UICC under the same AID; the platform filters them out automatically.

What happens when the UICC is removed for an app that relies on the certificates on it?

A: The app loses its privileges because the rules associated with the UICC are destroyed on UICC removal.

Is there a limit on the number of certificates on the UICC?

A: The platform doesn't limit the number of certificates; but because the check is linear, too many rules may incur a latency for check.

Is there a limit to the number of APIs that we can support with this method?

A: No, but we limit the scope to carrier-related APIs.

Are there some APIs prohibited from using this method? If so, how do you enforce them? (that is, do you have tests to validate which APIs are supported with this method?)

A: See the API Behavioral Compatibility section of the Android Compatibility Definition Document (CDD). We have some CTS tests to make sure that the permission model of the APIs isn't changed.

How does this work with the multi-SIM feature?

A: The default SIM specified by the user is used.

Does this in any way interact or overlap with other SE access technologies, for example, SEEK?

A: As an example, SEEK uses the same AID as on the UICC. So the rules coexist and are filtered by either SEEK or UiccCarrierPrivileges.

When is it a good time to check carrier privileges?

A: After the SIM state loaded broadcast.

Can OEMs disable part of carrier APIs?

A: No. We believe that the current APIs are the minimal set, and we plan to use the bit mask for finer granularity control in the future.

Does setOperatorBrandOverride override ALL other forms of operator name strings? For example, SE13, UICC SPN, or network-based NITZ?

Yes, the operator brand override has the highest priority. When it's set, it overrides ALL other forms of operator name strings.

What does the injectSmsPdu method call do?

A: This method facilitates SMS backup/restore in the cloud. The injectSmsPdu call enables the restore function.

For SMS filtering, is the onFilterSms call based on SMS UDH port filtering? Or do carrier apps have access to ALL incoming SMS?

A: Carriers have access to all SMS data.

The extension of DeviceAppID-REF-DO to support 32 bytes appears to be incompatible with the current GP spec (which allows 0 or 20 bytes only), so why are you introducing this change? Isn't SHA-1 sufficient to avoid collisions? Have you proposed this change to GP already, as this could be backward incompatible with existing ARA-M/ARF?

A: For providing future-proof security, this extension introduces SHA-256 for DeviceAppID-REF-DO in addition to SHA-1, which is currently the only option in the GP SEAC standard. We highly recommend using SHA-256.

If DeviceAppID is 0 (empty), do you apply the rule to all device apps not covered by a specific rule?

A: Carrier APIs require DeviceAppID-REF-DO be populated. Being empty is intended for test purposes and isn't recommended for operational deployments.

According to your spec, PKG-REF-DO used just by itself, without DeviceAppID-REF-DO, shouldn't be accepted. But it's still described in Table 6-4 of the specification as extending the definition of REF-DO. Is this on purpose? How does the code behave when only PKG-REF-DO is used in REF-DO?

A: The option of having PKG-REF-DO as a single value item in REF-DO was removed in the latest version. PKG-REF-DO should occur only in combination with DeviceAppID-REF-DO.

We assume that we can grant access to all carrier-based permissions or have finer-grained control. If so, what defines the mapping between the bit mask and the actual permissions? One permission per class? One permission per method? Are 64 separate permissions enough in the long run?

A: This is reserved for the future, and we welcome suggestions.

Can you further define DeviceAppID for Android specifically? This is the SHA-1 (20 bytes) hash value of the Publisher certificate used to sign the given app, so shouldn't the name reflect that purpose? (The name could be confusing to many readers as the rule is then applicable to all apps signed with that same Publisher certificate.)

A: The DeviceAppID storing certificates is supported by the existing spec. We tried to minimize spec changes to lower the barrier for adoption. For details, see Rules on UICC.