Commit 8c1b2355 authored by Marcel Holtmann's avatar Marcel Holtmann
Browse files

Bluetooth: Add enhanced security model for Simple Pairing 



The current security model is based around the flags AUTH, ENCRYPT and
SECURE. Starting with support for the Bluetooth 2.1 specification this is
no longer sufficient. The different security levels are now defined as
SDP, LOW, MEDIUM and SECURE.

Previously it was possible to set each security independently, but this
actually doesn't make a lot of sense. For Bluetooth the encryption depends
on a previous successful authentication. Also you can only update your
existing link key if you successfully created at least one before. And of
course the update of link keys without having proper encryption in place
is a security issue.

The new security levels from the Bluetooth 2.1 specification are now
used internally. All old settings are mapped to the new values and this
way it ensures that old applications still work. The only limitation
is that it is no longer possible to set authentication without also
enabling encryption. No application should have done this anyway since
this is actually a security issue. Without encryption the integrity of
the authentication can't be guaranteed.

As default for a new L2CAP or RFCOMM connection, the LOW security level
is used. The only exception here are the service discovery sessions on
PSM 1 where SDP level is used. To have similar security strength as with
a Bluetooth 2.0 and before combination key, the MEDIUM level should be
used. This is according to the Bluetooth specification. The MEDIUM level
will not require any kind of man-in-the-middle (MITM) protection. Only
the HIGH security level will require this.

Signed-off-by: default avatarMarcel Holtmann <marcel@holtmann.org>
parent c89b6e6b

include/net/bluetooth/bluetooth.h

+9 −0
Original line number Diff line number Diff line
@@ -53,6 +53,15 @@ 
#define SOL_SCO		17

#define SOL_RFCOMM	18



#define BT_SECURITY	4

struct bt_security {

	__u8 level;

};

#define BT_SECURITY_SDP		0

#define BT_SECURITY_LOW		1

#define BT_SECURITY_MEDIUM	2

#define BT_SECURITY_HIGH	3



#define BT_DEFER_SETUP	7



#define BT_INFO(fmt, arg...) printk(KERN_INFO "Bluetooth: " fmt "\n" , ## arg)

include/net/bluetooth/hci_core.h

+33 −23
Original line number Diff line number Diff line
@@ -169,6 +169,7 @@ struct hci_conn { 
	__u16            link_policy;

	__u32		 link_mode;

	__u8             auth_type;

	__u8             sec_level;

	__u8             power_save;

	unsigned long	 pend;
@@ -325,12 +326,11 @@ int hci_conn_del(struct hci_conn *conn); 
void hci_conn_hash_flush(struct hci_dev *hdev);

void hci_conn_check_pending(struct hci_dev *hdev);



struct hci_conn *hci_connect(struct hci_dev *hdev, int type, bdaddr_t *dst, __u8 auth_type);

struct hci_conn *hci_connect(struct hci_dev *hdev, int type, bdaddr_t *dst, __u8 sec_level, __u8 auth_type);

int hci_conn_check_link_mode(struct hci_conn *conn);

int hci_conn_auth(struct hci_conn *conn);

int hci_conn_encrypt(struct hci_conn *conn);

int hci_conn_security(struct hci_conn *conn, __u8 sec_level);

int hci_conn_change_link_key(struct hci_conn *conn);

int hci_conn_switch_role(struct hci_conn *conn, uint8_t role);

int hci_conn_switch_role(struct hci_conn *conn, __u8 role);



void hci_conn_enter_active_mode(struct hci_conn *conn);

void hci_conn_enter_sniff_mode(struct hci_conn *conn);
@@ -481,8 +481,7 @@ struct hci_proto { 
	int (*disconn_ind)	(struct hci_conn *conn, __u8 reason);

	int (*recv_acldata)	(struct hci_conn *conn, struct sk_buff *skb, __u16 flags);

	int (*recv_scodata)	(struct hci_conn *conn, struct sk_buff *skb);

	int (*auth_cfm)		(struct hci_conn *conn, __u8 status);

	int (*encrypt_cfm)	(struct hci_conn *conn, __u8 status, __u8 encrypt);

	int (*security_cfm)	(struct hci_conn *conn, __u8 status, __u8 encrypt);

};



static inline int hci_proto_connect_ind(struct hci_dev *hdev, bdaddr_t *bdaddr, __u8 type)
@@ -530,14 +529,20 @@ static inline void hci_proto_disconn_ind(struct hci_conn *conn, __u8 reason) 
static inline void hci_proto_auth_cfm(struct hci_conn *conn, __u8 status)

{

	register struct hci_proto *hp;

	__u8 encrypt;



	if (test_bit(HCI_CONN_ENCRYPT_PEND, &conn->pend))

		return;



	encrypt = (conn->link_mode & HCI_LM_ENCRYPT) ? 0x01 : 0x00;



	hp = hci_proto[HCI_PROTO_L2CAP];

	if (hp && hp->auth_cfm)

		hp->auth_cfm(conn, status);

	if (hp && hp->security_cfm)

		hp->security_cfm(conn, status, encrypt);



	hp = hci_proto[HCI_PROTO_SCO];

	if (hp && hp->auth_cfm)

		hp->auth_cfm(conn, status);

	if (hp && hp->security_cfm)

		hp->security_cfm(conn, status, encrypt);

}



static inline void hci_proto_encrypt_cfm(struct hci_conn *conn, __u8 status, __u8 encrypt)
@@ -545,12 +550,12 @@ static inline void hci_proto_encrypt_cfm(struct hci_conn *conn, __u8 status, __u 
	register struct hci_proto *hp;



	hp = hci_proto[HCI_PROTO_L2CAP];

	if (hp && hp->encrypt_cfm)

		hp->encrypt_cfm(conn, status, encrypt);

	if (hp && hp->security_cfm)

		hp->security_cfm(conn, status, encrypt);



	hp = hci_proto[HCI_PROTO_SCO];

	if (hp && hp->encrypt_cfm)

		hp->encrypt_cfm(conn, status, encrypt);

	if (hp && hp->security_cfm)

		hp->security_cfm(conn, status, encrypt);

}



int hci_register_proto(struct hci_proto *hproto);
@@ -562,8 +567,7 @@ struct hci_cb { 


	char *name;



	void (*auth_cfm)	(struct hci_conn *conn, __u8 status);

	void (*encrypt_cfm)	(struct hci_conn *conn, __u8 status, __u8 encrypt);

	void (*security_cfm)	(struct hci_conn *conn, __u8 status, __u8 encrypt);

	void (*key_change_cfm)	(struct hci_conn *conn, __u8 status);

	void (*role_switch_cfm)	(struct hci_conn *conn, __u8 status, __u8 role);

};
@@ -571,14 +575,20 @@ struct hci_cb { 
static inline void hci_auth_cfm(struct hci_conn *conn, __u8 status)

{

	struct list_head *p;

	__u8 encrypt;



	hci_proto_auth_cfm(conn, status);



	if (test_bit(HCI_CONN_ENCRYPT_PEND, &conn->pend))

		return;



	encrypt = (conn->link_mode & HCI_LM_ENCRYPT) ? 0x01 : 0x00;



	read_lock_bh(&hci_cb_list_lock);

	list_for_each(p, &hci_cb_list) {

		struct hci_cb *cb = list_entry(p, struct hci_cb, list);

		if (cb->auth_cfm)

			cb->auth_cfm(conn, status);

		if (cb->security_cfm)

			cb->security_cfm(conn, status, encrypt);

	}

	read_unlock_bh(&hci_cb_list_lock);

}
@@ -592,8 +602,8 @@ static inline void hci_encrypt_cfm(struct hci_conn *conn, __u8 status, __u8 encr 
	read_lock_bh(&hci_cb_list_lock);

	list_for_each(p, &hci_cb_list) {

		struct hci_cb *cb = list_entry(p, struct hci_cb, list);

		if (cb->encrypt_cfm)

			cb->encrypt_cfm(conn, status, encrypt);

		if (cb->security_cfm)

			cb->security_cfm(conn, status, encrypt);

	}

	read_unlock_bh(&hci_cb_list_lock);

}

net/bluetooth/hci_conn.c

+30 −15
Original line number Diff line number Diff line
@@ -325,7 +325,7 @@ EXPORT_SYMBOL(hci_get_route); 


/* Create SCO or ACL connection.

 * Device _must_ be locked */

struct hci_conn *hci_connect(struct hci_dev *hdev, int type, bdaddr_t *dst, __u8 auth_type)

struct hci_conn *hci_connect(struct hci_dev *hdev, int type, bdaddr_t *dst, __u8 sec_level, __u8 auth_type)

{

	struct hci_conn *acl;

	struct hci_conn *sco;
@@ -340,6 +340,7 @@ struct hci_conn *hci_connect(struct hci_dev *hdev, int type, bdaddr_t *dst, __u8 
	hci_conn_hold(acl);



	if (acl->state == BT_OPEN || acl->state == BT_CLOSED) {

		acl->sec_level = sec_level;

		acl->auth_type = auth_type;

		hci_acl_connect(acl);

	}
@@ -385,16 +386,17 @@ int hci_conn_check_link_mode(struct hci_conn *conn) 
EXPORT_SYMBOL(hci_conn_check_link_mode);



/* Authenticate remote device */

int hci_conn_auth(struct hci_conn *conn)

static int hci_conn_auth(struct hci_conn *conn, __u8 sec_level)

{

	BT_DBG("conn %p", conn);



	if (conn->ssp_mode > 0 && conn->hdev->ssp_mode > 0) {

		if (!(conn->auth_type & 0x01)) {

			conn->auth_type |= 0x01;

	if (sec_level > conn->sec_level)

		conn->link_mode &= ~HCI_LM_AUTH;

		}

	}



	conn->sec_level = sec_level;



	if (sec_level == BT_SECURITY_HIGH)

		conn->auth_type |= 0x01;



	if (conn->link_mode & HCI_LM_AUTH)

		return 1;
@@ -405,31 +407,42 @@ int hci_conn_auth(struct hci_conn *conn) 
		hci_send_cmd(conn->hdev, HCI_OP_AUTH_REQUESTED,

							sizeof(cp), &cp);

	}



	return 0;

}

EXPORT_SYMBOL(hci_conn_auth);



/* Enable encryption */

int hci_conn_encrypt(struct hci_conn *conn)

/* Enable security */

int hci_conn_security(struct hci_conn *conn, __u8 sec_level)

{

	BT_DBG("conn %p", conn);



	if (sec_level == BT_SECURITY_SDP)

		return 1;



	if (sec_level == BT_SECURITY_LOW) {

		if (conn->ssp_mode > 0 && conn->hdev->ssp_mode > 0)

			return hci_conn_auth(conn, sec_level);

		else

			return 1;

	}



	if (conn->link_mode & HCI_LM_ENCRYPT)

		return hci_conn_auth(conn);

		return hci_conn_auth(conn, sec_level);



	if (test_and_set_bit(HCI_CONN_ENCRYPT_PEND, &conn->pend))

		return 0;



	if (hci_conn_auth(conn)) {

	if (hci_conn_auth(conn, sec_level)) {

		struct hci_cp_set_conn_encrypt cp;

		cp.handle  = cpu_to_le16(conn->handle);

		cp.encrypt = 1;

		hci_send_cmd(conn->hdev, HCI_OP_SET_CONN_ENCRYPT,

							sizeof(cp), &cp);

	}



	return 0;

}

EXPORT_SYMBOL(hci_conn_encrypt);

EXPORT_SYMBOL(hci_conn_security);



/* Change link key */

int hci_conn_change_link_key(struct hci_conn *conn)
@@ -442,12 +455,13 @@ int hci_conn_change_link_key(struct hci_conn *conn) 
		hci_send_cmd(conn->hdev, HCI_OP_CHANGE_CONN_LINK_KEY,

							sizeof(cp), &cp);

	}



	return 0;

}

EXPORT_SYMBOL(hci_conn_change_link_key);



/* Switch role */

int hci_conn_switch_role(struct hci_conn *conn, uint8_t role)

int hci_conn_switch_role(struct hci_conn *conn, __u8 role)

{

	BT_DBG("conn %p", conn);
@@ -460,6 +474,7 @@ int hci_conn_switch_role(struct hci_conn *conn, uint8_t role) 
		cp.role = role;

		hci_send_cmd(conn->hdev, HCI_OP_SWITCH_ROLE, sizeof(cp), &cp);

	}



	return 0;

}

EXPORT_SYMBOL(hci_conn_switch_role);

net/bluetooth/hci_event.c

+2 −1
Original line number Diff line number Diff line
@@ -1601,7 +1601,8 @@ static inline void hci_remote_ext_features_evt(struct hci_dev *hdev, struct sk_b 


		if (conn->state == BT_CONFIG) {

			if (!ev->status && hdev->ssp_mode > 0 &&

					conn->ssp_mode > 0 && conn->out) {

					conn->ssp_mode > 0 && conn->out &&

					conn->sec_level != BT_SECURITY_SDP) {

				struct hci_cp_auth_requested cp;

				cp.handle = ev->handle;

				hci_send_cmd(hdev, HCI_OP_AUTH_REQUESTED,

net/bluetooth/l2cap.c

+40 −94
Original line number Diff line number Diff line
@@ -263,12 +263,17 @@ static inline int l2cap_check_link_mode(struct sock *sk) 
{

	struct l2cap_conn *conn = l2cap_pi(sk)->conn;



	if ((l2cap_pi(sk)->link_mode & L2CAP_LM_ENCRYPT) ||

				(l2cap_pi(sk)->link_mode & L2CAP_LM_SECURE))

		return hci_conn_encrypt(conn->hcon);

	if (l2cap_pi(sk)->link_mode & L2CAP_LM_SECURE)

		return hci_conn_security(conn->hcon, BT_SECURITY_HIGH);



	if (l2cap_pi(sk)->link_mode & L2CAP_LM_ENCRYPT)

		return hci_conn_security(conn->hcon, BT_SECURITY_MEDIUM);



	if (l2cap_pi(sk)->link_mode & L2CAP_LM_AUTH)

		return hci_conn_auth(conn->hcon);

		return hci_conn_security(conn->hcon, BT_SECURITY_LOW);



	if (l2cap_pi(sk)->psm == cpu_to_le16(0x0001))

		return hci_conn_security(conn->hcon, BT_SECURITY_SDP);



	return 1;

}
@@ -803,6 +808,7 @@ static int l2cap_do_connect(struct sock *sk) 
	struct l2cap_conn *conn;

	struct hci_conn *hcon;

	struct hci_dev *hdev;

	__u8 sec_level;

	__u8 auth_type;

	int err = 0;
@@ -815,21 +821,37 @@ static int l2cap_do_connect(struct sock *sk) 


	err = -ENOMEM;



	if (l2cap_pi(sk)->link_mode & L2CAP_LM_AUTH ||

			l2cap_pi(sk)->link_mode & L2CAP_LM_ENCRYPT ||

				l2cap_pi(sk)->link_mode & L2CAP_LM_SECURE) {

		if (l2cap_pi(sk)->psm == cpu_to_le16(0x0001))

			auth_type = HCI_AT_NO_BONDING_MITM;

	if (l2cap_pi(sk)->link_mode & L2CAP_LM_SECURE)

		sec_level = BT_SECURITY_HIGH;

	else if (l2cap_pi(sk)->psm == cpu_to_le16(0x0001))

		sec_level = BT_SECURITY_SDP;

	else if (l2cap_pi(sk)->link_mode & L2CAP_LM_ENCRYPT)

		sec_level = BT_SECURITY_MEDIUM;

	else

		sec_level = BT_SECURITY_LOW;



	if (sk->sk_type == SOCK_RAW) {

		if (l2cap_pi(sk)->link_mode & L2CAP_LM_SECURE)

			auth_type = HCI_AT_DEDICATED_BONDING_MITM;

		else if (l2cap_pi(sk)->link_mode & L2CAP_LM_ENCRYPT)

			auth_type = HCI_AT_DEDICATED_BONDING;

		else

			auth_type = HCI_AT_GENERAL_BONDING_MITM;

	} else {

		if (l2cap_pi(sk)->psm == cpu_to_le16(0x0001))

			auth_type = HCI_AT_NO_BONDING;

	} else if (l2cap_pi(sk)->psm == cpu_to_le16(0x0001)) {

		if (l2cap_pi(sk)->link_mode & L2CAP_LM_SECURE)

			auth_type = HCI_AT_NO_BONDING_MITM;

		else

			auth_type = HCI_AT_NO_BONDING;

	} else {

		if (l2cap_pi(sk)->link_mode & L2CAP_LM_SECURE)

			auth_type = HCI_AT_GENERAL_BONDING_MITM;

		else if (l2cap_pi(sk)->link_mode & L2CAP_LM_ENCRYPT)

			auth_type = HCI_AT_GENERAL_BONDING;

		else

			auth_type = HCI_AT_NO_BONDING;

	}



	hcon = hci_connect(hdev, ACL_LINK, dst, auth_type);

	hcon = hci_connect(hdev, ACL_LINK, dst, sec_level, auth_type);

	if (!hcon)

		goto done;
@@ -1402,11 +1424,6 @@ static void l2cap_chan_ready(struct sock *sk) 
		 */

		parent->sk_data_ready(parent, 0);

	}



	if (l2cap_pi(sk)->link_mode & L2CAP_LM_SECURE) {

		struct l2cap_conn *conn = l2cap_pi(sk)->conn;

		hci_conn_change_link_key(conn->hcon);

	}

}



/* Copy frame to all raw sockets on that connection */
@@ -2323,77 +2340,7 @@ static int l2cap_disconn_ind(struct hci_conn *hcon, u8 reason) 
	return 0;

}



static int l2cap_auth_cfm(struct hci_conn *hcon, u8 status)

{

	struct l2cap_chan_list *l;

	struct l2cap_conn *conn = hcon->l2cap_data;

	struct sock *sk;



	if (!conn)

		return 0;



	l = &conn->chan_list;



	BT_DBG("conn %p", conn);



	read_lock(&l->lock);



	for (sk = l->head; sk; sk = l2cap_pi(sk)->next_c) {

		struct l2cap_pinfo *pi = l2cap_pi(sk);



		bh_lock_sock(sk);



		if ((pi->link_mode & (L2CAP_LM_ENCRYPT | L2CAP_LM_SECURE)) &&

					!(hcon->link_mode & HCI_LM_ENCRYPT) &&

								!status) {

			bh_unlock_sock(sk);

			continue;

		}



		if (sk->sk_state == BT_CONNECT) {

			if (!status) {

				struct l2cap_conn_req req;

				req.scid = cpu_to_le16(l2cap_pi(sk)->scid);

				req.psm  = l2cap_pi(sk)->psm;



				l2cap_pi(sk)->ident = l2cap_get_ident(conn);



				l2cap_send_cmd(conn, l2cap_pi(sk)->ident,

					L2CAP_CONN_REQ, sizeof(req), &req);

			} else {

				l2cap_sock_clear_timer(sk);

				l2cap_sock_set_timer(sk, HZ / 10);

			}

		} else if (sk->sk_state == BT_CONNECT2) {

			struct l2cap_conn_rsp rsp;

			__u16 result;



			if (!status) {

				sk->sk_state = BT_CONFIG;

				result = L2CAP_CR_SUCCESS;

			} else {

				sk->sk_state = BT_DISCONN;

				l2cap_sock_set_timer(sk, HZ / 10);

				result = L2CAP_CR_SEC_BLOCK;

			}



			rsp.scid   = cpu_to_le16(l2cap_pi(sk)->dcid);

			rsp.dcid   = cpu_to_le16(l2cap_pi(sk)->scid);

			rsp.result = cpu_to_le16(result);

			rsp.status = cpu_to_le16(L2CAP_CS_NO_INFO);

			l2cap_send_cmd(conn, l2cap_pi(sk)->ident,

					L2CAP_CONN_RSP, sizeof(rsp), &rsp);

		}



		bh_unlock_sock(sk);

	}



	read_unlock(&l->lock);



	return 0;

}



static int l2cap_encrypt_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)

static int l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)

{

	struct l2cap_chan_list *l;

	struct l2cap_conn *conn = hcon->l2cap_data;
@@ -2413,10 +2360,10 @@ static int l2cap_encrypt_cfm(struct hci_conn *hcon, u8 status, u8 encrypt) 


		bh_lock_sock(sk);



		if ((pi->link_mode & (L2CAP_LM_ENCRYPT | L2CAP_LM_SECURE)) &&

		if (!status && encrypt == 0x00 &&

				(pi->link_mode & L2CAP_LM_SECURE) &&

					(sk->sk_state == BT_CONNECTED ||

						sk->sk_state == BT_CONFIG) &&

						!status && encrypt == 0x00) {

						sk->sk_state == BT_CONFIG)) {

			__l2cap_sock_close(sk, ECONNREFUSED);

			bh_unlock_sock(sk);

			continue;
@@ -2608,8 +2555,7 @@ static struct hci_proto l2cap_hci_proto = { 
	.connect_ind	= l2cap_connect_ind,

	.connect_cfm	= l2cap_connect_cfm,

	.disconn_ind	= l2cap_disconn_ind,

	.auth_cfm	= l2cap_auth_cfm,

	.encrypt_cfm	= l2cap_encrypt_cfm,

	.security_cfm	= l2cap_security_cfm,

	.recv_acldata	= l2cap_recv_acldata

};

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