fix(nimble): Out of order messages during SMP causing DOS vulerability

nimble/host/src/ble_sm.c

@@ -755,8 +755,13 @@ static void
 ble_sm_rx_noop(uint16_t conn_handle, struct os_mbuf **om,
                struct ble_sm_result *res)
 {
+    /**
+     * Unsupported PDU received
+     * Recommended action: Ignore
+     */
     res->app_status = BLE_HS_SM_US_ERR(BLE_SM_ERR_CMD_NOT_SUPP);
     res->sm_err = BLE_SM_ERR_CMD_NOT_SUPP;
+    res->out_of_order = 1;
 }
 
 static uint8_t
@@ -952,6 +957,17 @@ ble_sm_process_result(uint16_t conn_handle, struct ble_sm_result *res,
 
     rm = 0;
 
+    if (res && res->out_of_order) {
+        /**
+         * An unexpected SM PDU received.
+         * Spec recommends ignore the PDU.
+         */
+        memset(res, 0, sizeof *res);
+        res->sm_err = BLE_SM_ERR_UNSPECIFIED;
+        res->app_status = BLE_HS_SM_US_ERR(BLE_SM_ERR_UNSPECIFIED);
+        return;
+    }
+
     while (1) {
         ble_hs_lock();
         proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_NONE, -1,
@@ -1544,7 +1560,12 @@ ble_sm_random_rx(uint16_t conn_handle, struct os_mbuf **om,
     ble_hs_lock();
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_RANDOM, -1, NULL);
     if (proc == NULL) {
+        /**
+         * Unexpectedly received pairing random value.
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
+        res->out_of_order = 1;
     } else {
         memcpy(ble_sm_peer_pair_rand(proc), cmd->value, 16);
 
@@ -1592,7 +1613,12 @@ ble_sm_confirm_rx(uint16_t conn_handle, struct os_mbuf **om,
     ble_hs_lock();
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_CONFIRM, -1, NULL);
     if (proc == NULL) {
+        /**
+         * Unexpectedly received pairing confirm value.
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
+        res->out_of_order = 1;
     } else {
         memcpy(proc->confirm_peer, cmd->value, 16);
 
@@ -1849,12 +1875,13 @@ ble_sm_pair_req_rx(uint16_t conn_handle, struct os_mbuf **om,
      */
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_NONE, -1, &prev);
     if (proc != NULL) {
-        /* Fail if procedure is in progress unless we sent a slave security
+        /* Ignore if procedure is in progress unless we sent a slave security
          * request to peer.
          */
         if (proc->state != BLE_SM_PROC_STATE_SEC_REQ) {
             res->sm_err = BLE_SM_ERR_UNSPECIFIED;
             res->app_status = BLE_HS_SM_US_ERR(BLE_SM_ERR_UNSPECIFIED);
+            res->out_of_order = 1;
             ble_hs_unlock();
             return;
         }
@@ -2006,6 +2033,14 @@ ble_sm_pair_rsp_rx(uint16_t conn_handle, struct os_mbuf **om,
                 }
             }
         }
+    } else {
+        /**
+         * Unexpectedly received pairing response.
+         * Recommended action: Ignore
+         */
+        res->sm_err = BLE_SM_ERR_UNSPECIFIED;
+        res->app_status = BLE_HS_SM_US_ERR(BLE_SM_ERR_UNSPECIFIED);
+        res->out_of_order = 1;
     }
 
     ble_hs_unlock();
@@ -2046,6 +2081,7 @@ ble_sm_sec_req_rx(uint16_t conn_handle, struct os_mbuf **om,
     struct ble_hs_conn_addrs addrs;
     struct ble_sm_sec_req *cmd;
     struct ble_hs_conn *conn;
+    struct ble_sm_proc *proc;
     int authreq_mitm;
 
     res->app_status = ble_hs_mbuf_pullup_base(om, sizeof(*cmd));
@@ -2096,6 +2132,16 @@ ble_sm_sec_req_rx(uint16_t conn_handle, struct os_mbuf **om,
             }
         }
 
+        /** Make sure a procedure isn't already in progress for this connection. */
+        ble_hs_lock();
+        proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_NONE, -1, NULL);
+        ble_hs_unlock();
+        if (proc != NULL) {
+            res->out_of_order = 1;
+            proc = NULL;
+            return;
+        }
+
         if (res->app_status == 0) {
             res->app_status = ble_sm_enc_initiate(conn_handle,
                                                   value_sec.key_size,
@@ -2391,8 +2437,13 @@ ble_sm_enc_info_rx(uint16_t conn_handle, struct os_mbuf **om,
 
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_KEY_EXCH, -1, NULL);
     if (proc == NULL) {
+        /**
+         * Unexpected encryption info received
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
         res->sm_err = BLE_SM_ERR_UNSPECIFIED;
+        res->out_of_order = 1;
     } else {
         proc->rx_key_flags &= ~BLE_SM_KE_F_ENC_INFO;
         proc->peer_keys.ltk_valid = 1;
@@ -2425,8 +2476,13 @@ ble_sm_master_id_rx(uint16_t conn_handle, struct os_mbuf **om,
 
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_KEY_EXCH, -1, NULL);
     if (proc == NULL) {
+        /**
+         * Unexpected central indentification info recieved
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
         res->sm_err = BLE_SM_ERR_UNSPECIFIED;
+        res->out_of_order = 1;
     } else {
         proc->rx_key_flags &= ~BLE_SM_KE_F_MASTER_ID;
         proc->peer_keys.ediv_rand_valid = 1;
@@ -2460,8 +2516,13 @@ ble_sm_id_info_rx(uint16_t conn_handle, struct os_mbuf **om,
 
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_KEY_EXCH, -1, NULL);
     if (proc == NULL) {
+        /**
+         * Unexpected ID info received
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
         res->sm_err = BLE_SM_ERR_UNSPECIFIED;
+        res->out_of_order = 1;
     } else {
         proc->rx_key_flags &= ~BLE_SM_KE_F_ID_INFO;
 
@@ -2494,8 +2555,13 @@ ble_sm_id_addr_info_rx(uint16_t conn_handle, struct os_mbuf **om,
 
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_KEY_EXCH, -1, NULL);
     if (proc == NULL) {
+        /**
+         * Unexpected identity address info received
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
         res->sm_err = BLE_SM_ERR_UNSPECIFIED;
+        res->out_of_order = 1;
     } else {
         proc->rx_key_flags &= ~BLE_SM_KE_F_ADDR_INFO;
         proc->peer_keys.addr_valid = 1;
@@ -2528,8 +2594,13 @@ ble_sm_sign_info_rx(uint16_t conn_handle, struct os_mbuf **om,
 
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_KEY_EXCH, -1, NULL);
     if (proc == NULL) {
+        /**
+         * Unexpected signing info received
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
         res->sm_err = BLE_SM_ERR_UNSPECIFIED;
+        res->out_of_order = 1;
     } else {
         proc->rx_key_flags &= ~BLE_SM_KE_F_SIGN_INFO;
 

nimble/host/src/ble_sm_priv.h

@@ -287,6 +287,7 @@ struct ble_sm_result {
     unsigned enc_cb : 1;
     unsigned bonded : 1;
     unsigned restore : 1;
+    unsigned out_of_order : 1;
 };
 
 #if MYNEWT_VAL(BLE_HS_DEBUG)

nimble/host/src/ble_sm_sc.c

@@ -624,8 +624,13 @@ ble_sm_sc_public_key_rx(uint16_t conn_handle, struct os_mbuf **om,
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_PUBLIC_KEY, -1,
                             NULL);
     if (proc == NULL) {
+        /**
+         * Unexpected public key information received
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
         res->sm_err = BLE_SM_ERR_UNSPECIFIED;
+        res->out_of_order = 1;
     } else {
         memcpy(&proc->pub_key_peer, cmd, sizeof(*cmd));
         rc = ble_sm_alg_gen_dhkey(proc->pub_key_peer.x,
@@ -850,7 +855,12 @@ ble_sm_sc_dhkey_check_rx(uint16_t conn_handle, struct os_mbuf **om,
     proc = ble_sm_proc_find(conn_handle, BLE_SM_PROC_STATE_DHKEY_CHECK, -1,
                             NULL);
     if (proc == NULL) {
+        /**
+         * Unexpected DHKey check values received
+         * Recommended action: Ignore
+         */
         res->app_status = BLE_HS_ENOENT;
+        res->out_of_order = 1;
     } else {
         ble_sm_dhkey_check_process(proc, cmd, res);
     }