hostapd: Avoid key reinstallation in FT handshake

Do not reinstall TK to the driver during Reassociation Response frame
processing if the first attempt of setting the TK succeeded. This avoids
issues related to clearing the TX/RX PN that could result in reusing
same PN values for transmitted frames (e.g., due to CCM nonce reuse and
also hitting replay protection on the receiver) and accepting replayed
frames on RX side.

This issue was introduced by the commit
0e84c25434e6a1f283c7b4e62e483729085b78d2 ('FT: Fix PTK configuration in
authenticator') which allowed wpa_ft_install_ptk() to be called multiple
times with the same PTK. While the second configuration attempt is
needed with some drivers, it must be done only if the first attempt
failed.

Change-Id: I45909184ad3dc8f3f608ce99ee853f3551323458
Signed-off-by: Mathy Vanhoef <Mathy.Vanhoef@cs.kuleuven.be>

4 files changed, 20 insertions, 0 deletions

diff --git a/src/ap/wpa_auth.c b/src/ap/wpa_auth.c
index f9c7d4c5..89b3bb2d 100644
--- a/src/ap/wpa_auth.c
+++ b/src/ap/wpa_auth.c
@@ -3197,6 +3197,14 @@ int wpa_auth_sta_wpa_version(struct wpa_state_machine *sm)
 }
 
 
+int wpa_auth_sta_ft_tk_already_set(struct wpa_state_machine *sm)
+{
+	if (!sm || !wpa_key_mgmt_ft(sm->wpa_key_mgmt))
+		return 0;
+	return sm->tk_already_set;
+}
+
+
 int wpa_auth_sta_clear_pmksa(struct wpa_state_machine *sm,
 			     struct rsn_pmksa_cache_entry *entry)
 {
diff --git a/src/ap/wpa_auth.h b/src/ap/wpa_auth.h
index e7478064..42a88b99 100644
--- a/src/ap/wpa_auth.h
+++ b/src/ap/wpa_auth.h
@@ -267,6 +267,7 @@ int wpa_auth_pairwise_set(struct wpa_state_machine *sm);
 int wpa_auth_get_pairwise(struct wpa_state_machine *sm);
 int wpa_auth_sta_key_mgmt(struct wpa_state_machine *sm);
 int wpa_auth_sta_wpa_version(struct wpa_state_machine *sm);
+int wpa_auth_sta_ft_tk_already_set(struct wpa_state_machine *sm);
 int wpa_auth_sta_clear_pmksa(struct wpa_state_machine *sm,
 			     struct rsn_pmksa_cache_entry *entry);
 struct rsn_pmksa_cache_entry *
diff --git a/src/ap/wpa_auth_ft.c b/src/ap/wpa_auth_ft.c
index eeaffbf6..f8f5dbe3 100644
--- a/src/ap/wpa_auth_ft.c
+++ b/src/ap/wpa_auth_ft.c
@@ -780,6 +780,14 @@ void wpa_ft_install_ptk(struct wpa_state_machine *sm)
 		return;
 	}
 
+	if (sm->tk_already_set) {
+		/* Must avoid TK reconfiguration to prevent clearing of TX/RX
+		 * PN in the driver */
+		wpa_printf(MSG_DEBUG,
+			   "FT: Do not re-install same PTK to the driver");
+		return;
+	}
+
 	/* FIX: add STA entry to kernel/driver here? The set_key will fail
 	 * most likely without this.. At the moment, STA entry is added only
 	 * after association has been completed. This function will be called
@@ -792,6 +800,7 @@ void wpa_ft_install_ptk(struct wpa_state_machine *sm)
 
 	/* FIX: MLME-SetProtection.Request(TA, Tx_Rx) */
 	sm->pairwise_set = TRUE;
+	sm->tk_already_set = TRUE;
 }
 
 
@@ -898,6 +907,7 @@ static int wpa_ft_process_auth_req(struct wpa_state_machine *sm,
 
 	sm->pairwise = pairwise;
 	sm->PTK_valid = TRUE;
+	sm->tk_already_set = FALSE;
 	wpa_ft_install_ptk(sm);
 
 	buflen = 2 + sizeof(struct rsn_mdie) + 2 + sizeof(struct rsn_ftie) +
diff --git a/src/ap/wpa_auth_i.h b/src/ap/wpa_auth_i.h
index 57b098f2..234d84c8 100644
--- a/src/ap/wpa_auth_i.h
+++ b/src/ap/wpa_auth_i.h
@@ -64,6 +64,7 @@ struct wpa_state_machine {
 	struct wpa_ptk PTK;
 	Boolean PTK_valid;
 	Boolean pairwise_set;
+	Boolean tk_already_set;
 	int keycount;
 	Boolean Pair;
 	struct wpa_key_replay_counter {