Deepen AUTHENTICATE decode: P2 auth context + AUTN/AUTS decomposition

- Add a P2 spec for AUTHENTICATE (auth context bits + specific-reference-data
  flag), so P2 is displayed instead of only leaking through cmd.context.
- Fix P1 name to 'No indication' (was the misleading 'Run GSM algorithm').
- Decompose AUTN into SQN(xor)AK / AMF / MAC and AUTS into SQN(xor)AK / MAC-S
  per TS 33.102; surface 'specific reference data' key flag.

frontend/index.html

@@ -454,7 +454,7 @@ function cmd_description(m) {
 function sw_text(m) {
     const d = m.decoded;
     if (!d || !d.sw) return '';
-    return d.sw.sw1 + ' ' + d.sw.sw2;
+    return (d.sw.sw1 + ' ' + d.sw.sw2).toUpperCase();
 }
 
 function sw_class(m) {
@@ -536,7 +536,11 @@ function responseRows(resp) {
         if (resp.ck) rows.push(['CK', resp.ck]);
         if (resp.ik) rows.push(['IK', resp.ik]);
         if (resp.kc) rows.push(['Kc', resp.kc]);
-        if (resp.auts) rows.push(['AUTS', resp.auts]);
+        if (resp.auts) {
+            rows.push(['AUTS', resp.auts]);
+            if (resp.sqn_ak) rows.push(['SQN⊕AK', resp.sqn_ak + ' (concealed)']);
+            if (resp.mac_s) rows.push(['MAC-S', resp.mac_s]);
+        }
     }
 
     if (resp.code !== undefined) {
@@ -564,10 +568,15 @@ function cmdRows(cmd) {
     const rows = [];
 
     // AUTHENTICATE command body
-    if (cmd.context !== undefined) {
+    if (cmd.rand !== undefined || cmd.autn !== undefined || cmd.specific_key) {
-        rows.push(['Auth context', cmd.context]);
+        if (cmd.specific_key) rows.push(['Key', 'specific reference data']);
         if (cmd.rand) rows.push(['RAND', cmd.rand]);
-        if (cmd.autn) rows.push(['AUTN', cmd.autn]);
+        if (cmd.autn) {
+            rows.push(['AUTN', cmd.autn]);
+            if (cmd.sqn_ak) rows.push(['SQN⊕AK', cmd.sqn_ak + ' (concealed)']);
+            if (cmd.amf) rows.push(['AMF', cmd.amf]);
+            if (cmd.mac) rows.push(['MAC', cmd.mac]);
+        }
     }
 
     // ENVELOPE fields

simtrace2_pysniff/server/decode.py

@@ -552,7 +552,14 @@ APDU_SPEC = {
     },
     0x88: {
         'name': 'AUTHENTICATE',
-        'p1': {0x00: 'Run GSM algorithm', 0x80: 'Run 3G algo (resynchronisation)'},
+        'p1': {0x00: 'No indication'},
+        'p2': {'label': 'Auth context', 'bits': {
+            0x00: 'GSM context',
+            0x01: '3G/EPS/5G context',
+            0x02: 'VGCS/VBS context',
+            0x04: 'GBA context',
+            0x80: 'Specific reference data',
+        }},
         'body': {'label': 'Challenge/session key'},
     },
     0x89: {
@@ -1127,9 +1134,15 @@ def _decode_auth_3g(data):
     if tag == 0xDC:  # synchronisation failure → length byte + AUTS
         if len(data) >= 2:
             auts_len = data[1]
-            return {'type': '3G', 'status': 'sync fail',
+            auts = data[2:2 + auts_len]
-                    'auts': data[2:2 + auts_len].hex().upper()}
+        else:
-        return {'type': '3G', 'status': 'sync fail', 'auts': data[1:].hex().upper()}
+            auts = data[1:]
+        result = {'type': '3G', 'status': 'sync fail', 'auts': auts.hex().upper()}
+        # AUTS = SQN_MS⊕AK (6) || MAC-S (8)  (TS 33.102)
+        if len(auts) >= 14:
+            result['sqn_ak'] = auts[0:6].hex().upper()
+            result['mac_s'] = auts[6:14].hex().upper()
+        return result
     # tag 0xDB: success → length-prefixed RES, CK, IK, (KC)
     result = {'type': '3G', 'status': 'success'}
     i = 1
@@ -1170,18 +1183,12 @@ def _decode_response_for(ins, data):
 
 # ──────────────────── Command-body decoders ────────────────────
 
-AUTH_CONTEXTS = {
-    0: 'GSM',
-    1: '3G (UMTS)',
-    2: 'VGC/VBS',
-    4: 'GBA',
-}
-
-
 def _decode_auth_cmd(data, p2):
     """Decode an AUTHENTICATE command body (RAND / RAND+AUTN)."""
     ctx = p2 & 0x07
-    result = {'context': AUTH_CONTEXTS.get(ctx, f'unknown ({ctx})')}
+    result = {}
+    if p2 & 0x80:
+        result['specific_key'] = True
     if ctx in (0, 1) and data:
         i = 0
         if i < len(data):
@@ -1189,10 +1196,16 @@ def _decode_auth_cmd(data, p2):
             i += 1
             result['rand'] = data[i:i + rlen].hex().upper()
             i += rlen
-        if ctx == 1 and i < len(data):  # 3G → AUTN
+        if ctx == 1 and i < len(data):  # 3G/EPS/5G → AUTN
             alen = data[i]
             i += 1
-            result['autn'] = data[i:i + alen].hex().upper()
+            autn = data[i:i + alen]
+            result['autn'] = autn.hex().upper()
+            # AUTN = SQN⊕AK (6) || AMF (2) || MAC-A (8)  (TS 33.102)
+            if len(autn) >= 16:
+                result['sqn_ak'] = autn[0:6].hex().upper()
+                result['amf'] = autn[6:8].hex().upper()
+                result['mac'] = autn[8:16].hex().upper()
     return result
 
 

tests/test_decode.py

@@ -361,17 +361,39 @@ class TestAuthCommand(unittest.TestCase):
         r = decode_message(bytes.fromhex(
             '0088008122104A75BA425D438C549EF35BA5E3DD53051065E04D80E4DC8000A5C7FD842F41395E6135'))
         cmd = r['cmd']
-        self.assertEqual(cmd['context'], '3G (UMTS)')
+        self.assertNotIn('context', cmd)
+        self.assertEqual(cmd['specific_key'], True)
         self.assertEqual(cmd['rand'], '4A75BA425D438C549EF35BA5E3DD5305')
         self.assertEqual(cmd['autn'], '65E04D80E4DC8000A5C7FD842F41395E')
+        self.assertEqual(cmd['sqn_ak'], '65E04D80E4DC')
+        self.assertEqual(cmd['amf'], '8000')
+        self.assertEqual(cmd['mac'], 'A5C7FD842F41395E')
+
+    def test_auth_p2_context(self):
+        r = decode_message(bytes.fromhex(
+            '0088008122104A75BA425D438C549EF35BA5E3DD53051065E04D80E4DC8000A5C7FD842F41395E6135'))
+        p2 = r['p2']
+        self.assertEqual(p2['raw'], '81')
+        self.assertIn('3G/EPS/5G context', p2['bits'])
+        self.assertIn('Specific reference data', p2['bits'])
 
     def test_gsm_rand_only(self):
         from simtrace2_pysniff.server.decode import _decode_auth_cmd
         r = _decode_auth_cmd(bytes.fromhex('10' + '00' * 16), 0x00)
-        self.assertEqual(r['context'], 'GSM')
+        self.assertNotIn('context', r)
+        self.assertNotIn('specific_key', r)
         self.assertEqual(r['rand'], '00' * 16)
         self.assertNotIn('autn', r)
 
+    def test_sync_fail_auts(self):
+        from simtrace2_pysniff.server.decode import _decode_auth
+        auts = bytes.fromhex('010203040506' + '0a0b0c0d0e0f1011')
+        r = _decode_auth(b'\xdc' + bytes([len(auts)]) + auts)
+        self.assertEqual(r['status'], 'sync fail')
+        self.assertEqual(r['auts'], auts.hex().upper())
+        self.assertEqual(r['sqn_ak'], '010203040506')
+        self.assertEqual(r['mac_s'], '0A0B0C0D0E0F1011')
+
 
 class TestEventDownload(unittest.TestCase):
     def test_location_status(self):