enhance bonding process

- auto remove obsolete key on central and re-try with a fresh session.

Author: hathach

libraries/Bluefruit52Lib/src/BLEGap.cpp

@@ -171,15 +171,19 @@ bool BLEGap::requestPairing(uint16_t conn_hdl)
   // skip if already paired
   if ( peer->paired ) return true;
 
-  // Check to see if we did bonded with current prph
+  uint16_t cntr_ediv = 0xFFFF;
+
   if ( peer->role == BLE_GAP_ROLE_CENTRAL )
   {
+    // Check to see if we did bonded with current prph previously
     bond_data_t bdata;
 
     if ( bond_find_cntr(&peer->addr, &bdata) )
     {
-      LOG_LV2("BOND", "Load Keys from file " BOND_FNAME_CNTR, bdata.peer_enc.master_id.ediv);
+      cntr_ediv = bdata.peer_enc.master_id.ediv;
+      LOG_LV2("BOND", "Load Keys from file " BOND_FNAME_CNTR, cntr_ediv);
       VERIFY_STATUS( sd_ble_gap_encrypt(conn_hdl, &bdata.peer_enc.master_id, &bdata.peer_enc.enc_info), false);
+
     }else
     {
       VERIFY_STATUS( sd_ble_gap_authenticate(conn_hdl, &_sec_param ), false);
@@ -194,6 +198,18 @@ bool BLEGap::requestPairing(uint16_t conn_hdl)
 
   xSemaphoreTake(peer->pair_sem, portMAX_DELAY);
 
+  // Failed to pair using centra stored keys, this happens when
+  // Prph delete bonds while we did not --> let's remove the obsolete keyfile and move on
+  if ( !peer->paired && (cntr_ediv != 0xffff) )
+  {
+    bond_remove_key(BLE_GAP_ROLE_CENTRAL, cntr_ediv);
+
+    // Re-try with a fresh session
+    VERIFY_STATUS( sd_ble_gap_authenticate(conn_hdl, &_sec_param ), false);
+
+    xSemaphoreTake(peer->pair_sem, portMAX_DELAY);
+  }
+
   vSemaphoreDelete(peer->pair_sem);
   peer->pair_sem = NULL;
 

libraries/Bluefruit52Lib/src/utility/bonding.cpp

@@ -47,6 +47,11 @@
 #define printBondDir(role)
 #endif
 
+static void get_fname(char* fname, uint8_t role, uint16_t ediv)
+{
+  sprintf(fname, ( role == BLE_GAP_ROLE_PERIPH ) ? BOND_FNAME_PRPH : BOND_FNAME_CNTR, ediv);
+}
+
 /*------------------------------------------------------------------*/
 /* Saving Bond Data to Nffs in following layout
  * - _bond_data 80 bytes
@@ -69,13 +74,7 @@ void bond_init(void)
 static void bond_save_keys_dfr(uint8_t role, uint16_t conn_hdl, bond_data_t* bdata)
 {
   char filename[BOND_FNAME_LEN];
-  if ( role == BLE_GAP_ROLE_PERIPH )
-  {
-    sprintf(filename, BOND_FNAME_PRPH, bdata->own_enc.master_id.ediv);
-  }else
-  {
-    sprintf(filename, BOND_FNAME_CNTR, bdata->peer_enc.master_id.ediv);
-  }
+  get_fname(filename, role, role == BLE_GAP_ROLE_PERIPH ? bdata->own_enc.master_id.ediv : bdata->peer_enc.master_id.ediv);
 
   char devname[CFG_MAX_DEVNAME_LEN] = { 0 };
   Bluefruit.Gap.getPeerName(conn_hdl, devname, CFG_MAX_DEVNAME_LEN);
@@ -100,13 +99,8 @@ static void bond_save_keys_dfr(uint8_t role, uint16_t conn_hdl, bond_data_t* bda
   }
 
   file.write((uint8_t*) devname, CFG_MAX_DEVNAME_LEN);
-
   file.close();
 
-  PRINT_HEX(bdata->own_enc.master_id.ediv);
-  PRINT_HEX(bdata->peer_enc.master_id.ediv);
-
-
   if (result)
   {
     LOG_LV2("BOND", "Keys for \"%s\" is saved to file %s", devname, filename);
@@ -132,13 +126,7 @@ void bond_save_keys(uint8_t role, uint16_t conn_hdl, bond_data_t* bdata)
 bool bond_load_keys(uint8_t role, uint16_t ediv, bond_data_t* bdata)
 {
   char filename[BOND_FNAME_LEN];
-  if ( role == BLE_GAP_ROLE_PERIPH )
-  {
-    sprintf(filename, BOND_FNAME_PRPH, ediv);
-  }else
-  {
-    sprintf(filename, BOND_FNAME_CNTR, ediv);
-  }
+  get_fname(filename, role, ediv);
 
   bool result = (Nffs.readFile(filename, bdata, sizeof(bond_data_t)) > 0);
 
@@ -169,13 +157,7 @@ static void bond_save_cccd_dfr (uint8_t role, uint16_t conn_hdl, uint16_t ediv)
   {
     // save to file
     char filename[BOND_FNAME_LEN];
-    if ( role == BLE_GAP_ROLE_PERIPH )
-    {
-      sprintf(filename, BOND_FNAME_PRPH, ediv);
-    }else
-    {
-      sprintf(filename, BOND_FNAME_CNTR, ediv);
-    }
+    get_fname(filename, role, ediv);
 
     if ( Nffs.writeFile(filename, sys_attr, len, BOND_FILE_CCCD_OFFSET) )
     {
@@ -205,13 +187,7 @@ bool bond_load_cccd(uint8_t role, uint16_t cond_hdl, uint16_t ediv)
   bool loaded = false;
 
   char filename[BOND_FNAME_LEN];
-  if ( role == BLE_GAP_ROLE_PERIPH )
-  {
-    sprintf(filename, BOND_FNAME_PRPH, ediv);
-  }else
-  {
-    sprintf(filename, BOND_FNAME_CNTR, ediv);
-  }
+  get_fname(filename, role, ediv);
 
   NffsFile file(filename, FS_ACCESS_READ);
 
@@ -353,3 +329,11 @@ void bond_clear_all(void)
   (void) Nffs.mkdir_p(BOND_DIR_PRPH);
   (void) Nffs.mkdir_p(BOND_DIR_CNTR);
 }
+
+void bond_remove_key(uint8_t role, uint16_t ediv)
+{
+  char filename[BOND_FNAME_LEN];
+  get_fname(filename, role, ediv);
+
+  Nffs.remove(filename);
+}

libraries/Bluefruit52Lib/src/utility/bonding.h

@@ -61,18 +61,20 @@ enum
   BOND_FILE_CCCD_OFFSET    = BOND_FILE_DEVNAME_OFFSET + CFG_MAX_DEVNAME_LEN
 };
 
-void     bond_init(void);
-void     bond_clear_prph(void);
-void     bond_clear_cntr(void);
-void     bond_clear_all(void);
+void bond_init(void);
+void bond_clear_prph(void);
+void bond_clear_cntr(void);
+void bond_clear_all(void);
 
-void     bond_save_keys(uint8_t role, uint16_t conn_hdl, bond_data_t* bdata);
-bool     bond_load_keys(uint8_t role, uint16_t ediv, bond_data_t* bdata);
+void bond_remove_key(uint8_t role, uint16_t ediv);
 
-void     bond_save_cccd(uint8_t role, uint16_t cond_hdl, uint16_t ediv);
-bool     bond_load_cccd(uint8_t role, uint16_t cond_hdl, uint16_t ediv);
+void bond_save_keys(uint8_t role, uint16_t conn_hdl, bond_data_t* bdata);
+bool bond_load_keys(uint8_t role, uint16_t ediv, bond_data_t* bdata);
 
-void     bond_print_list(uint8_t role);
+void bond_save_cccd(uint8_t role, uint16_t cond_hdl, uint16_t ediv);
+bool bond_load_cccd(uint8_t role, uint16_t cond_hdl, uint16_t ediv);
+
+void bond_print_list(uint8_t role);
 
 bool bond_find_cntr(ble_gap_addr_t* addr, bond_data_t* bdata);