Bluetooth: Add key size checks for SMP

This patch implements a check in smp cmd pairing request and pairing
response to verify if encryption key maximum size is compatible in both
slave and master when SMP Pairing is requested. Keys are also masked to
the correct negotiated size.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Signed-off-by: Anderson Briglia <anderson.briglia@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 157419a..bf1c7f6 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -400,6 +400,7 @@
 	__u8		prnd[16]; /* SMP Pairing Random */
 	__u8		pcnf[16]; /* SMP Pairing Confirm */
 	__u8		tk[16]; /* SMP Temporary Key */
+	__u8		smp_key_size;
 
 	struct timer_list security_timer;
 
diff --git a/include/net/bluetooth/smp.h b/include/net/bluetooth/smp.h
index 111853a..4fb7d19 100644
--- a/include/net/bluetooth/smp.h
+++ b/include/net/bluetooth/smp.h
@@ -112,6 +112,9 @@
 #define SMP_UNSPECIFIED		0x08
 #define SMP_REPEATED_ATTEMPTS		0x09
 
+#define SMP_MIN_ENC_KEY_SIZE		7
+#define SMP_MAX_ENC_KEY_SIZE		16
+
 /* SMP Commands */
 int smp_conn_security(struct l2cap_conn *conn, __u8 sec_level);
 int smp_sig_channel(struct l2cap_conn *conn, struct sk_buff *skb);