## Mais resultados

Estes são da minha [prova de conceito original](https://github.com/zhuowei/blueshrimp/tree/first-poc) antes de eu descobrir como realocar o buffer:

Após forçar um emulador Android 15 a atuar como um alto-falante Bluetooth, executar este código resulta em uma desreferência nula:```
*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
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)

Não testei isto num dispositivo físico.

## O meu entendimento do que está a acontecer

Os auscultadores Bluetooth usam o [Handsfree Profile](https://github.com/zhuowei/blueshrimp/blob/HEAD/%3Chttps:/en.wikipedia.org/wiki/List_of_Bluetooth_profiles#Hands-Free_Profile_(HFP)>).

O Handsfree Profile é especial: ao contrário da maioria dos serviços Bluetooth, onde um lado atua como cliente e o outro como servidor, tanto o auricular como o dispositivo de ligação (ex.: um telefone) precisam de executar um servidor Bluetooth.

Depois de o telefone se ligar ao serviço Handsfree do auricular (0x111e), o auricular liga-se de volta ao serviço Handsfree Audio Gateway do telefone (0x111f).

Quando um telefone abre uma conexão RFCOMM para o serviço Handsfree do auricular, no código hf_client do auricular:

- [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) aloca um handle `tBTA_HF_CLIENT_CB` a partir do 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) aloca um `tSDP_DISCOVERY_DB`, armazena-o em `client_cb->p_disc_db`, e inicia a descoberta 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) armazena o `tSDP_DISCOVERY_DB` num `p_ccb->p_db` de um `tCONN_CB`, depois liga-se ao serviço SDP do telefone
- agora o `tSDP_DISCOVERY_DB` está armazenado tanto no handle `client_cb->p_disc_db` do hf_client como no `p_ccb->p_db` da camada SDP

Quando a conexão RFCOMM do telefone é fechada:

- [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) emite um evento `BTA_HF_CLIENT_RFC_CLOSE_EVT`
- [a tabela de estados 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) chama o handler para [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 reinicia a máquina de estados para `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) vê a transição de estado e desaloca o handle `tBTA_HF_CLIENT_CB` de volta ao pool
- No entanto, antes da correção, a conexão SDP não é cancelada e ainda está à espera de uma resposta
- Neste momento, há um `tBTA_HF_CLIENT_CB` devolvido ao pool não alocado, com `client_cb->p_disc_db` ainda definido e uma descoberta SDP ainda ativa

Quando o telefone responde à descoberta SDP com um erro:

- [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) emite um `BTA_HF_CLIENT_DISC_INT_RES_EVT`
- [a tabela de estados 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) chama o handler para [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) liberta `client_cb->p_disc_db`
- então agora o `tSDP_DISCOVERY_DB` é libertado, `client_cb->p_disc_db` é nulo, e a camada SDP já não tem um `p_ccb->p_db` para a DB de descoberta.

No entanto, se o telefone abrir o RFCOMM novamente antes de a primeira descoberta SDP retornar:

- realocamos um handle (provavelmente o mesmo handle que foi desalocado para o pool anteriormente) e chamamos a descoberta novamente.
- `client_cb->p_disc_db` aponta agora para um novo `tSDP_DISCOVERY_DB`, e a camada SDP contém dois `tSDP_DISCOVERY_DB`: um `p_ccb->p_db` contém a DB antiga da primeira conexão e outro `p_ccb->p_db` contém a DB nova da segunda conexão

Agora, o telefone responde à primeira descoberta SDP com um erro:

- a camada SDP fecha o `p_ccb` da primeira conexão
- [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) liberta `client_cb->p_disc_db`, que é a DB da _segunda_ conexão
- agora o `client_cb->p_disc_db` do hf_client é libertado e definido como nulo, e o `p_ccb` da SDP para a primeira conexão desapareceu
- mas o `p_ccb` para a segunda conexão ainda está ativo, então `p_ccb->p_db` para o segundo pedido de descoberta SDP aponta para um `tSDP_DISCOVERY_DB` libertado

Finalmente, o telefone responde à segunda descoberta SDP com uma resposta real:

- a camada SDP processa os dados recebidos em [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 envia para 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) começa a ler de `p_ccb->p_db`
- como `p_db` já foi libertado por `bta_hf_client_free_db` da resposta de erro da primeira descoberta SDP, a segunda resposta SDP causa use-after-free.

O que não entendo:

- O Bionic suporta [malloc_debug](https://android.googlesource.com/platform/bionic/+/master/libc/malloc_debug/README.md): definir `"LIBC_DEBUG_MALLOC_OPTIONS=fill\ verbose"` preenche a memória com `0xef` ao libertar. Por que não vejo `0xef` no log de crash?

## Execução

Criar um emulador Android Studio com Android Automotive 14, API 34-ext9, "Android Automotive with Google APIs arm64-v8a System Image", versão 5 - este tem Headset Client ativado por predefinição.

Alternativamente, para fazer com que um emulador Android não-Automotive emule uns auscultadores Bluetooth:

Iniciar um emulador Android local para Android 15 no Android Studio. (Estou a usar Android Emulator para Android 15, "Google APIs ARM 64 v8a System Image", versão 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 o emulador for vulnerável (por exemplo, Android 15 API 35 "Google APIs ARM 64 v8a System Image" revisão 9), você obterá:```
(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 o emulador não for vulnerável (e.g. Android 16 API 36.1 "Google APIs ARM 64 v8a System Image" revision 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$