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/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);