FT: Make aes_unwrap() calls easier to analyze

Using aes_unwrap() to initialize a data structure seemed to be too much
for some static analyzers to understand. Make it obvious that the target
is initialized and that the target is not just the single struct member.
In addition, clean up the design to avoid removal of const with a
typecast. (CID 68112, CID 68134, CID 68135, CID 68136)

Signed-off-by: Jouni Malinen <j@w1.fi>

src/ap/wpa_auth_ft.c

@@ -10,6 +10,7 @@
 
 #include "utils/common.h"
 #include "utils/eloop.h"
+#include "utils/list.h"
 #include "common/ieee802_11_defs.h"
 #include "common/ieee802_11_common.h"
 #include "crypto/aes_wrap.h"
@@ -1310,7 +1311,9 @@ static int wpa_ft_rrb_rx_pull(struct wpa_authenticator *wpa_auth,
 			      const u8 *src_addr,
 			      const u8 *data, size_t data_len)
 {
-	struct ft_r0kh_r1kh_pull_frame *frame, f;
+	struct ft_r0kh_r1kh_pull_frame f;
+	const u8 *crypt;
+	u8 *plain;
 	struct ft_remote_r1kh *r1kh;
 	struct ft_r0kh_r1kh_resp_frame resp, r;
 	u8 pmk_r0[PMK_LEN];
@@ -1318,7 +1321,7 @@ static int wpa_ft_rrb_rx_pull(struct wpa_authenticator *wpa_auth,
 
 	wpa_printf(MSG_DEBUG, "FT: Received PMK-R1 pull");
 
-	if (data_len < sizeof(*frame))
+	if (data_len < sizeof(f))
 		return -1;
 
 	r1kh = wpa_auth->conf.r1kh_list;
@@ -1334,12 +1337,14 @@ static int wpa_ft_rrb_rx_pull(struct wpa_authenticator *wpa_auth,
 		return -1;
 	}
 
-	frame = (struct ft_r0kh_r1kh_pull_frame *) data;
+	crypt = data + offsetof(struct ft_r0kh_r1kh_pull_frame, nonce);
+	os_memset(&f, 0, sizeof(f));
+	plain = ((u8 *) &f) + offsetof(struct ft_r0kh_r1kh_pull_frame, nonce);
 	/* aes_unwrap() does not support inplace decryption, so use a temporary
 	 * buffer for the data. */
 	if (aes_unwrap(r1kh->key, sizeof(r1kh->key),
 		       (FT_R0KH_R1KH_PULL_DATA_LEN + 7) / 8,
-		       frame->nonce, f.nonce) < 0) {
+		       crypt, plain) < 0) {
 		wpa_printf(MSG_DEBUG, "FT: Failed to decrypt PMK-R1 pull "
 			   "request from " MACSTR, MAC2STR(src_addr));
 		return -1;
@@ -1442,13 +1447,15 @@ static int wpa_ft_rrb_rx_resp(struct wpa_authenticator *wpa_auth,
 			      const u8 *src_addr,
 			      const u8 *data, size_t data_len)
 {
-	struct ft_r0kh_r1kh_resp_frame *frame, f;
+	struct ft_r0kh_r1kh_resp_frame f;
+	const u8 *crypt;
+	u8 *plain;
 	struct ft_remote_r0kh *r0kh;
 	int pairwise, res;
 
 	wpa_printf(MSG_DEBUG, "FT: Received PMK-R1 pull response");
 
-	if (data_len < sizeof(*frame))
+	if (data_len < sizeof(f))
 		return -1;
 
 	r0kh = wpa_auth->conf.r0kh_list;
@@ -1464,12 +1471,14 @@ static int wpa_ft_rrb_rx_resp(struct wpa_authenticator *wpa_auth,
 		return -1;
 	}
 
-	frame = (struct ft_r0kh_r1kh_resp_frame *) data;
+	crypt = data + offsetof(struct ft_r0kh_r1kh_resp_frame, nonce);
+	os_memset(&f, 0, sizeof(f));
+	plain = ((u8 *) &f) + offsetof(struct ft_r0kh_r1kh_resp_frame, nonce);
 	/* aes_unwrap() does not support inplace decryption, so use a temporary
 	 * buffer for the data. */
 	if (aes_unwrap(r0kh->key, sizeof(r0kh->key),
 		       (FT_R0KH_R1KH_RESP_DATA_LEN + 7) / 8,
-		       frame->nonce, f.nonce) < 0) {
+		       crypt, plain) < 0) {
 		wpa_printf(MSG_DEBUG, "FT: Failed to decrypt PMK-R1 pull "
 			   "response from " MACSTR, MAC2STR(src_addr));
 		return -1;
@@ -1507,7 +1516,9 @@ static int wpa_ft_rrb_rx_push(struct wpa_authenticator *wpa_auth,
 			      const u8 *src_addr,
 			      const u8 *data, size_t data_len)
 {
-	struct ft_r0kh_r1kh_push_frame *frame, f;
+	struct ft_r0kh_r1kh_push_frame f;
+	const u8 *crypt;
+	u8 *plain;
 	struct ft_remote_r0kh *r0kh;
 	struct os_time now;
 	os_time_t tsend;
@@ -1515,7 +1526,7 @@ static int wpa_ft_rrb_rx_push(struct wpa_authenticator *wpa_auth,
 
 	wpa_printf(MSG_DEBUG, "FT: Received PMK-R1 push");
 
-	if (data_len < sizeof(*frame))
+	if (data_len < sizeof(f))
 		return -1;
 
 	r0kh = wpa_auth->conf.r0kh_list;
@@ -1531,12 +1542,15 @@ static int wpa_ft_rrb_rx_push(struct wpa_authenticator *wpa_auth,
 		return -1;
 	}
 
-	frame = (struct ft_r0kh_r1kh_push_frame *) data;
+	crypt = data + offsetof(struct ft_r0kh_r1kh_push_frame, timestamp);
+	os_memset(&f, 0, sizeof(f));
+	plain = ((u8 *) &f) + offsetof(struct ft_r0kh_r1kh_push_frame,
+				       timestamp);
 	/* aes_unwrap() does not support inplace decryption, so use a temporary
 	 * buffer for the data. */
 	if (aes_unwrap(r0kh->key, sizeof(r0kh->key),
 		       (FT_R0KH_R1KH_PUSH_DATA_LEN + 7) / 8,
-		       frame->timestamp, f.timestamp) < 0) {
+		       crypt, plain) < 0) {
 		wpa_printf(MSG_DEBUG, "FT: Failed to decrypt PMK-R1 push from "
 			   MACSTR, MAC2STR(src_addr));
 		return -1;