Re: [PATCH-v5 5/6] Bluetooth: Add MITM mechanism to LE-SMP

To achive Man-In-The-Middle (MITM) level security with Low Energy,
we have to enable User Passkey Comparison.  This commit modifies the
hard-coded JUST-WORKS pairing mechanism to support query via the MGMT
interface of Passkey comparison and User Confirmation.

Signed-off-by: Brian Gix <redacted>
---
 include/net/bluetooth/hci_core.h |    1 +
 include/net/bluetooth/smp.h      |    3 +
 net/bluetooth/smp.c              |  228 ++++++++++++++++++++++++++++++++++----
 3 files changed, 210 insertions(+), 22 deletions(-)

diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index e7b2e25..4aa417c 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h

@@ -312,6 +312,7 @@ struct hci_conn {
 	struct hci_dev	*hdev;
 	void		*l2cap_data;
 	void		*sco_data;
+	void		*smp_conn;
 
 	struct hci_conn	*link;
 

diff --git a/include/net/bluetooth/smp.h b/include/net/bluetooth/smp.h
index 15b97d5..43b6c49 100644
--- a/include/net/bluetooth/smp.h
+++ b/include/net/bluetooth/smp.h

@@ -124,6 +124,8 @@ struct smp_chan {
 	u8		pcnf[16]; /* SMP Pairing Confirm */
 	u8		tk[16]; /* SMP Temporary Key */
 	u8		smp_key_size;
+	u8		smp_tk_valid;
+	u8		smp_cfm_pending;

 	struct crypto_blkcipher	*tfm;
 	struct work_struct confirm;
 	struct work_struct random;

@@ -134,6 +136,7 @@ struct smp_chan {
 int smp_conn_security(struct l2cap_conn *conn, __u8 sec_level);
 int smp_sig_channel(struct l2cap_conn *conn, struct sk_buff *skb);
 int smp_distribute_keys(struct l2cap_conn *conn, __u8 force);
+int smp_user_confirm_reply(struct hci_conn *conn, u16 mgmt_op, __le32 passkey);
 
 void smp_chan_destroy(struct l2cap_conn *conn);
 

diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 0b96737..e1df0a2 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c

@@ -23,6 +23,7 @@
 #include <net/bluetooth/bluetooth.h>
 #include <net/bluetooth/hci_core.h>
 #include <net/bluetooth/l2cap.h>
+#include <net/bluetooth/mgmt.h>
 #include <net/bluetooth/smp.h>
 #include <linux/crypto.h>
 #include <linux/scatterlist.h>

@@ -188,24 +189,46 @@ static void smp_send_cmd(struct l2cap_conn *conn, u8 code, u16 len, void *data)
 					msecs_to_jiffies(SMP_TIMEOUT));
 }
 
+static __u8 authreq_to_seclevel(__u8 authreq)
+{
+	if (authreq & SMP_AUTH_MITM)
+		return BT_SECURITY_HIGH;
+	else
+		return BT_SECURITY_MEDIUM;
+}
+
+static __u8 seclevel_to_authreq(__u8 sec_level)
+{
+	switch (sec_level) {
+	case BT_SECURITY_HIGH:
+		return SMP_AUTH_MITM | SMP_AUTH_BONDING;
+	case BT_SECURITY_MEDIUM:
+		return SMP_AUTH_BONDING;
+	default:
+		return SMP_AUTH_NONE;
+	}
+}
+
 static void build_pairing_cmd(struct l2cap_conn *conn,
 				struct smp_cmd_pairing *req,
 				struct smp_cmd_pairing *rsp,
 				__u8 authreq)
 {
-	u8 dist_keys;
+	u8 all_keys = 0;
+	u8 dist_keys = 0;
 
-	dist_keys = 0;
 	if (test_bit(HCI_PAIRABLE, &conn->hcon->hdev->flags)) {
 		dist_keys = SMP_DIST_ENC_KEY;
 		authreq |= SMP_AUTH_BONDING;
+	} else {
+		authreq &= ~SMP_AUTH_BONDING;
 	}
 
 	if (rsp == NULL) {
 		req->io_capability = conn->hcon->io_capability;
 		req->oob_flag = SMP_OOB_NOT_PRESENT;
 		req->max_key_size = SMP_MAX_ENC_KEY_SIZE;
-		req->init_key_dist = dist_keys;
+		req->init_key_dist = all_keys;
 		req->resp_key_dist = dist_keys;
 		req->auth_req = authreq;
 		return;

@@ -214,7 +237,7 @@ static void build_pairing_cmd(struct l2cap_conn *conn,
 	rsp->io_capability = conn->hcon->io_capability;
 	rsp->oob_flag = SMP_OOB_NOT_PRESENT;
 	rsp->max_key_size = SMP_MAX_ENC_KEY_SIZE;
-	rsp->init_key_dist = req->init_key_dist & dist_keys;
+	rsp->init_key_dist = req->init_key_dist & all_keys;