Received-SPF: pass (google.com: domain of linux-bluetooth-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Received-SPF: Fail (protection.outlook.com: domain of arri.de does not
 designate 217.111.95.7 as permitted sender) receiver=protection.outlook.com;
 client-ip=217.111.95.7; helo=mta.arri.de;
From:   Christian Eggers <ceggers@arri.de>
To:     <linux-bluetooth@vger.kernel.org>
CC:     Matias Karhumaa <matias.karhumaa@gmail.com>,
        Ari Timonen <ari.timonen@synopsys.com>
Subject: Just-Works re-pairing doesn't work
Date:   Fri, 16 Jun 2023 15:57:16 +0200
Message-ID: <8240386.T7Z3S40VBb@n95hx1g2>
Organization: Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jun 2023 13:57:18.4475
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 4bd68ea4-af9d-4c17-c558-08db6e719948
X-MS-Exchange-CrossTenant-Id: e6a73a5a-614d-4c51-b3e3-53b660a9433a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=e6a73a5a-614d-4c51-b3e3-53b660a9433a;Ip=[217.111.95.7];Helo=[mta.arri.de]
X-MS-Exchange-CrossTenant-AuthSource: DB5EUR02FT042.eop-EUR02.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB9PR07MB9127
X-Spam-Status: No, score=-0.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,FORGED_SPF_HELO,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,
        SPF_HELO_PASS,T_SCC_BODY_TEXT_LINE,T_SPF_TEMPERROR,URIBL_BLOCKED
        autolearn=no autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-bluetooth.vger.kernel.org>
X-Mailing-List: linux-bluetooth@vger.kernel.org

Kernel: 5.15.113
Bluez: 5.65
Peer: iPad with i.OS 15.7
Application: 
- Embedded L2CAP application with own agent. 
- Agent has been registered with "NoInputNoOutput".
- BT_SECURITY for L2CAP socket has been set to 2.

Problem:
Re-pairing (pairing again after "removing"/"ignoring" the Linux device in the system
settings of the iOS device) doesn't work. In order to successfully pair
again, I first have also to "remove" the iOS device on the Linux system using
bluetoothctl.

See also (looks equal to my problem):
https://stackoverflow.com/questions/75362887/linuxbluezbluetooth-failed-to-re-connect-after-forgetting-while-using-noin

I tried the following patch:
https://patches.linaro.org/project/linux-bluetooth/patch/20210208220531.3471-2-matias.karhumaa@gmail.com/

After applying this patch, re-pairing works fine on my system.

I don't have the oversight to tell whether the patch above is correct.
Additionally I am unsure whether the "JustWorksRepairing" setting has
any meaning on my system (as I have implemented an own agent within my application).


regards,
Christian


/etc/bluetooth/main.conf:
------------------------8<------------------------
AlwaysPairable = true
JustWorksRepairing = always
------------------------>8------------------------


Log:
> ACL Data RX: Handle 25 flags 0x02 dlen 11                                                                                                                              #16 [hci0] 2.807328
      SMP: Pairing Request (0x01) len 6
        IO capability: KeyboardDisplay (0x04)
        OOB data: Authentication data not present (0x00)
        Authentication requirement: Bonding, MITM, SC, No Keypresses, CT2 (0x2d)
        Max encryption key size: 16
        Initiator key distribution: EncKey IdKey LinkKey (0x0b)
        Responder key distribution: EncKey IdKey LinkKey (0x0b)
> ACL Data RX: Handle 25 flags 0x02 dlen 11                                                                                                                              #17 [hci0] 2.807436
      ATT: Read By Group Type Request (0x10) len 6
        Handle range: 0x0001-0xffff
        Attribute group type: Primary Service (0x2800)
< ACL Data TX: Handle 25 flags 0x00 dlen 11                                                                                                                              #18 [hci0] 2.807514
      SMP: Pairing Response (0x02) len 6
        IO capability: NoInputNoOutput (0x03)
        OOB data: Authentication data not present (0x00)
        Authentication requirement: Bonding, MITM, SC, No Keypresses, CT2 (0x2d)
        Max encryption key size: 16
        Initiator key distribution: EncKey IdKey (0x03)
        Responder key distribution: EncKey (0x01)
...

> ACL Data RX: Handle 25 flags 0x02 dlen 69                                                                                                                              #46 [hci0] 8.507352
      SMP: Pairing Public Key (0x0c) len 64
        X: 8b6f72774ab48d0246be000d4555e2f99f9799518be4bccc3e3e509a31b2ae03
        Y: bf3f03e9f08c67b1e843be1ca7a0522686216828becefa40f6622e3322e4db5e
< ACL Data TX: Handle 25 flags 0x00 dlen 69                                                                                                                              #47 [hci0] 8.545335
      SMP: Pairing Public Key (0x0c) len 64
        X: 1975cc04c4ef4444a202898c0ad006e01d1ff5fb64b6648fdb585004987c6c28
        Y: fbe9d105bd2d0c134618e87ad850443021d3c30d03e452c9be3a67bc071b548e
< ACL Data TX: Handle 25 flags 0x00 dlen 21                                                                                                                              #48 [hci0] 8.545395
      SMP: Pairing Confirm (0x03) len 16
        Confim value: 89353a66cb49c378698c73bbb91ed203
> HCI Event: Number of Completed Packets (0x13) plen 5                                                                                                                   #49 [hci0] 8.568106
        Num handles: 1
        Handle: 25 Address: 7F:C0:E4:47:71:5A (Resolvable)
        Count: 1
> ACL Data RX: Handle 25 flags 0x02 dlen 21                                                                                                                              #50 [hci0] 8.597228
      SMP: Pairing Random (0x04) len 16
        Random value: e31d5e3904a034178b59ee6215691095
@ MGMT Event: User Confirmation Request (0x000f) plen 12                                                                                                            {0x0001} [hci0] 8.597365
        LE Address: 54:62:E2:37:6A:A9 (OUI 54-62-E2)
        Confirm hint: 0x01
        Value: 0x00000000
< ACL Data TX: Handle 25 flags 0x00 dlen 21                                                                                                                              #51 [hci0] 8.597400
      SMP: Pairing Random (0x04) len 16
        Random value: 484ff14d26537f86dfbefd924fbd8eb9
@ MGMT Command: User Confirmation Reply (0x001c) plen 7                                                                                                             {0x0001} [hci0] 8.597845
        LE Address: 54:62:E2:37:6A:A9 (OUI 54-62-E2)
@ MGMT Event: Command Complete (0x0001) plen 10                                                                                                                     {0x0001} [hci0] 8.597876
      User Confirmation Reply (0x001c) plen 7
        Status: Success (0x00)
        LE Address: 54:62:E2:37:6A:A9 (OUI 54-62-E2)
> HCI Event: Number of Completed Packets (0x13) plen 5                                                                                                                   #52 [hci0] 8.598099
        Num handles: 1
        Handle: 25 Address: 7F:C0:E4:47:71:5A (Resolvable)
        Count: 1
> ACL Data RX: Handle 25 flags 0x02 dlen 21                                                                                                                              #53 [hci0] 8.657238
      SMP: Pairing DHKey Check (0x0d) len 16
        E: 1ffb663bb5033f7127b4fb43fb0e5c00
@ MGMT Event: Authentication Failed (0x0011) plen 8                                                                                                                 {0x0001} [hci0] 8.657418
        LE Address: 54:62:E2:37:6A:A9 (OUI 54-62-E2)
        Status: Authentication Failed (0x05)
< ACL Data TX: Handle 25 flags 0x00 dlen 6                                                                                                                               #54 [hci0] 8.657466
      SMP: Pairing Failed (0x05) len 1
        Reason: DHKey check failed (0x0b)