Commit 2ae9e277 authored by Joakim Andersson's avatar Joakim Andersson Committed by Anas Nashif
Browse files

Bluetooth: SMP: Re-pairing cannot lower the security level of the bond 

Make sure that a new pairing procedure with an existing bond does not
result in a security with weaker security properties.

Signed-off-by: default avatarJoakim Andersson <joakim.andersson@nordicsemi.no>
parent abe47b70

subsys/bluetooth/host/smp.c

+67 −12
Changes for subsys/bluetooth/host/smp.c: 67 added lines, 12 removed lines.
Original line number Diff line number Diff line
@@ -294,10 +294,20 @@ no_callbacks: 
	}

}



#if !defined(CONFIG_BT_SMP_SC_PAIR_ONLY)

static u8_t legacy_get_pair_method(struct bt_smp *smp, u8_t remote_io);

#endif



static u8_t get_pair_method(struct bt_smp *smp, u8_t remote_io)

{

	struct bt_smp_pairing *req, *rsp;



#if !defined(CONFIG_BT_SMP_SC_PAIR_ONLY)

	if (!atomic_test_bit(smp->flags, SMP_FLAG_SC)) {

		return legacy_get_pair_method(smp, remote_io);

	}

#endif



	if (remote_io > BT_SMP_IO_KEYBOARD_DISPLAY)

		return JUST_WORKS;
@@ -541,6 +551,39 @@ static u8_t get_encryption_key_size(struct bt_smp *smp) 
	return MIN(req->max_key_size, rsp->max_key_size);

}



/* Check that if a new pairing procedure with an existing bond will not lower

 * the established security level of the bond.

 */

bool update_keys_check(struct bt_smp *smp)

{

	struct bt_conn *conn = smp->chan.chan.conn;



	if (!conn->le.keys) {

		conn->le.keys = bt_keys_get_addr(conn->id, &conn->le.dst);

	}



	if (!conn->le.keys ||

	    !(conn->le.keys->keys & (BT_KEYS_LTK_P256 | BT_KEYS_LTK))) {

		return true;

	}



	if (conn->le.keys->enc_size > get_encryption_key_size(smp)) {

		return false;

	}



	if ((conn->le.keys->keys & BT_KEYS_LTK_P256) &&

	    !atomic_test_bit(smp->flags, SMP_FLAG_SC)) {

		return false;

	}



	if ((conn->le.keys->flags & BT_KEYS_AUTHENTICATED) &&

	     smp->method == JUST_WORKS) {

		return false;

	}



	return true;

}



#if defined(CONFIG_BT_PRIVACY) || defined(CONFIG_BT_SIGNING) || \

	!defined(CONFIG_BT_SMP_SC_PAIR_ONLY)

/* For TX callbacks */
@@ -2001,14 +2044,12 @@ static u8_t legacy_send_pairing_confirm(struct bt_smp *smp) 
}



#if defined(CONFIG_BT_PERIPHERAL)

static u8_t legacy_pairing_req(struct bt_smp *smp, u8_t remote_io)

static u8_t legacy_pairing_req(struct bt_smp *smp)

{

	u8_t ret;



	BT_DBG("");



	smp->method = legacy_get_pair_method(smp, remote_io);



	/* ask for consent if pairing is not due to sending SecReq*/

	if ((DISPLAY_FIXED(smp) || smp->method == JUST_WORKS) &&

	    !atomic_test_bit(smp->flags, SMP_FLAG_SEC_REQ) &&
@@ -2207,14 +2248,12 @@ static u8_t smp_master_ident(struct bt_smp *smp, struct net_buf *buf) 
}



#if defined(CONFIG_BT_CENTRAL)

static u8_t legacy_pairing_rsp(struct bt_smp *smp, u8_t remote_io)

static u8_t legacy_pairing_rsp(struct bt_smp *smp)

{

	u8_t ret;



	BT_DBG("");



	smp->method = legacy_get_pair_method(smp, remote_io);



	/* ask for consent if this is due to received SecReq */

	if ((DISPLAY_FIXED(smp) || smp->method == JUST_WORKS) &&

	    atomic_test_bit(smp->flags, SMP_FLAG_SEC_REQ) &&
@@ -2442,16 +2481,20 @@ static u8_t smp_pairing_req(struct bt_smp *smp, struct net_buf *buf) 


	atomic_set_bit(smp->flags, SMP_FLAG_PAIRING);



	smp->method = get_pair_method(smp, req->io_capability);



	if (!update_keys_check(smp)) {

		return BT_SMP_ERR_AUTH_REQUIREMENTS;

	}



	if (!atomic_test_bit(smp->flags, SMP_FLAG_SC)) {

#if defined(CONFIG_BT_SMP_SC_PAIR_ONLY)

		return BT_SMP_ERR_AUTH_REQUIREMENTS;

#else

		return legacy_pairing_req(smp, req->io_capability);

		return legacy_pairing_req(smp);

#endif /* CONFIG_BT_SMP_SC_PAIR_ONLY */

	}



	smp->method = get_pair_method(smp, req->io_capability);



	if ((IS_ENABLED(CONFIG_BT_SMP_SC_ONLY) ||

	     conn->required_sec_level == BT_SECURITY_FIPS) &&

		smp->method == JUST_WORKS) {
@@ -2604,16 +2647,20 @@ static u8_t smp_pairing_rsp(struct bt_smp *smp, struct net_buf *buf) 
		atomic_set_bit(smp->flags, SMP_FLAG_BOND);

	}



	smp->method = get_pair_method(smp, rsp->io_capability);



	if (!update_keys_check(smp)) {

		return BT_SMP_ERR_AUTH_REQUIREMENTS;

	}



	if (!atomic_test_bit(smp->flags, SMP_FLAG_SC)) {

#if defined(CONFIG_BT_SMP_SC_PAIR_ONLY)

		return BT_SMP_ERR_AUTH_REQUIREMENTS;

#else

		return legacy_pairing_rsp(smp, rsp->io_capability);

		return legacy_pairing_rsp(smp);

#endif /* CONFIG_BT_SMP_SC_PAIR_ONLY */

	}



	smp->method = get_pair_method(smp, rsp->io_capability);



	if ((IS_ENABLED(CONFIG_BT_SMP_SC_ONLY) ||

	     conn->required_sec_level == BT_SECURITY_FIPS) &&

	     smp->method == JUST_WORKS) {
@@ -3368,6 +3415,14 @@ static u8_t smp_public_key(struct bt_smp *smp, struct net_buf *buf) 
	if (memcmp(smp->pkey, sc_debug_public_key, 64) == 0) {

		BT_INFO("Remote is using Debug Public key");

		atomic_set_bit(smp->flags, SMP_FLAG_SC_DEBUG_KEY);



		/* Don't allow a bond established without debug key to be

		 * updated using LTK generated from debug key.

		 */

		if (smp->chan.chan.conn->le.keys &&

		    !(smp->chan.chan.conn->le.keys->flags & BT_KEYS_DEBUG)) {

			return BT_SMP_ERR_AUTH_REQUIREMENTS;

		}

	}



	if (IS_ENABLED(CONFIG_BT_CENTRAL) &&

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