Add sm_sec_req_auto_pair: configurable auto-pairing on Security Request

src/NimBLEDevice.cpp

@@ -1221,6 +1221,18 @@ void NimBLEDevice::setSecurityAuth(uint8_t auth_req) {
  * * 0x03 BLE_HS_IO_NO_INPUT_OUTPUT      NoInputNoOutput IO capability
  * * 0x04 BLE_HS_IO_KEYBOARD_DISPLAY     KeyboardDisplay Only IO capability
  */
+/**
+ * @brief Set whether a Security Request from a peer we have no keys for
+ *        automatically sends a Pairing Request.
+ * @param [in] enable true (default): pair immediately. false: ignore the
+ *        request; the application pairs via NimBLEClient::secureConnection().
+ * @details Some peripherals never answer a Pairing Request sent in the same
+ *        instant as their own Security Request.
+ */
+void NimBLEDevice::setSecurityAutoPairOnSecReq(bool enable) {
+    ble_hs_cfg.sm_sec_req_auto_pair = enable;
+} // setSecurityAutoPairOnSecReq
+
 void NimBLEDevice::setSecurityIOCap(uint8_t iocap) {
     ble_hs_cfg.sm_io_cap = iocap;
 } // setSecurityIOCap

src/NimBLEDevice.h

@@ -141,6 +141,7 @@ class NimBLEDevice {
     static void          setSecurityAuth(bool bonding, bool mitm, bool sc);
     static void          setSecurityAuth(uint8_t auth);
     static void          setSecurityIOCap(uint8_t iocap);
+    static void          setSecurityAutoPairOnSecReq(bool enable);
     static void          setSecurityInitKey(uint8_t initKey);
     static void          setSecurityRespKey(uint8_t respKey);
     static void          setSecurityPasskey(uint32_t passKey);

src/nimble/nimble/host/include/host/ble_hs.h

@@ -319,6 +319,16 @@ struct ble_hs_cfg {
      */
     unsigned sm_keypress:1;
 
+    /** @brief Security Manager - auto-pair on Security Request
+     *
+     * If set (default), a Security Request from a peer we have no keys for
+     * immediately triggers a Pairing Request. If clear, it is ignored and the
+     * application initiates pairing (ble_gap_security_initiate). Some
+     * peripherals never answer a Pairing Request sent in the same instant as
+     * their Security Request. Peers we have keys for are unaffected.
+     */
+    unsigned sm_sec_req_auto_pair:1;
+
     /** @brief Security Manager Local Key Distribution Mask */
     uint8_t sm_our_key_dist;
 

src/nimble/nimble/host/src/ble_hs_cfg.c

@@ -28,6 +28,7 @@ struct ble_hs_cfg ble_hs_cfg = {
     .sm_mitm = MYNEWT_VAL(BLE_SM_MITM),
     .sm_sc = MYNEWT_VAL(BLE_SM_SC),
     .sm_keypress = MYNEWT_VAL(BLE_SM_KEYPRESS),
+    .sm_sec_req_auto_pair = MYNEWT_VAL(BLE_SM_SEC_REQ_AUTO_PAIR),
     .sm_our_key_dist = MYNEWT_VAL(BLE_SM_OUR_KEY_DIST),
     .sm_their_key_dist = MYNEWT_VAL(BLE_SM_THEIR_KEY_DIST),
 };

src/nimble/nimble/host/src/ble_sm.c

@@ -2090,7 +2090,16 @@ ble_sm_sec_req_rx(uint16_t conn_handle, struct os_mbuf **om,
             }
         }
     } else {
-        /* no keys present, start pairing */
+        /* no keys present: start pairing, unless the application wants to
+         * initiate pairing itself. In that case only a clean "no keys"
+         * result is ignored; store errors are propagated.
+         */
+        if (!ble_hs_cfg.sm_sec_req_auto_pair) {
+            if (res->app_status == BLE_HS_ENOENT) {
+                res->app_status = 0;
+            }
+            return;
+        }
         start_pairing = true;
     }
 

src/syscfg/syscfg.h

@@ -835,6 +835,10 @@
 #define MYNEWT_VAL_BLE_SM_SC_DEBUG_KEYS (0)
 #endif
 
+#ifndef MYNEWT_VAL_BLE_SM_SEC_REQ_AUTO_PAIR
+#define MYNEWT_VAL_BLE_SM_SEC_REQ_AUTO_PAIR (1)
+#endif
+
 #ifndef MYNEWT_VAL_BLE_SM_SC_ONLY
 #define MYNEWT_VAL_BLE_SM_SC_ONLY (0)
 #endif