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  • Case ID: 116528
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Peer manager LESC 'Just works' Pairing bug

Keton

Problem description:

When using 'Just works' pairing with LESC key exchange peer_manager doesn't allocate buffer for peer public key and doesn't pass own public key to sd_ble_gap_sec_params_reply on BLE_GAP_EVT_SEC_PARAMS_REQUEST. This results in softdevice throwing error code 10 which escalates to PM_EVT_ERROR_UNEXPECTED resulting in assert.

Steps to reproduce:

Compile ble_app_multirole_lesc example with following main.c. Connect to the board and try to pair.

Mitigation:

Apply following patch:

index 524a976..986d18b 100644
--- a/nRF5x_SDK12/components/ble/peer_manager/security_dispatcher.c
+++ b/nRF5x_SDK12/components/ble/peer_manager/security_dispatcher.c
@@ -596,7 +596,13 @@ ret_code_t smd_params_reply(uint16_t                 conn_handle,
     }
     else
     {
-        // Pairing only, no action needed.
+        //Pairing
+                               if(p_sec_params->lesc) //LESC 'Just works' pairing
+                               {
+                                       // Add own public key and buffer for peer public key to parameters passed to softdevice
+                                       sec_keyset.keys_own.p_pk       = p_public_key;
+                                       sec_keyset.keys_peer.p_pk      = &m_peer_pk;
+                               }
     }

     if (err_code == NRF_SUCCESS)

This allows successful pairing and bonding in 'just works' mode with ECDH based key exchange.

I'd be grateful if someone with more knowledge of how peer_manager works internally looked at my modifications and made sure that it didn't broke anything.

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