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From:   Szymon Janc <szymon.janc@codecoup.pl>
To:     linux-bluetooth@vger.kernel.org
Cc:     Szymon Janc <szymon.janc@codecoup.pl>,
        Maarten Fonville <maarten.fonville@gmail.com>,
        stable@vger.kernel.org
Subject: [PATCH] Bluetooth: SMP: Workaround Microsoft Surface Precision Mouse bug
Date:   Wed, 19 Jun 2019 00:47:47 +0200
Message-Id: <20190618224747.446-1-szymon.janc@codecoup.pl>
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Sender: linux-bluetooth-owner@vger.kernel.org
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Microsoft Surface Precision Mouse provides bogus identity address when
pairing. It connects with Static Random address but provides Public
Address in SMP Identity Address Information PDU. Address has same
value but type is different. Workaround this by dropping IRK if ID
address discrepancy is detected.

> HCI Event: LE Meta Event (0x3e) plen 19
      LE Connection Complete (0x01)
        Status: Success (0x00)
        Handle: 75
        Role: Master (0x00)
        Peer address type: Random (0x01)
        Peer address: E0:52:33:93:3B:21 (Static)
        Connection interval: 50.00 msec (0x0028)
        Connection latency: 0 (0x0000)
        Supervision timeout: 420 msec (0x002a)
        Master clock accuracy: 0x00

....

> ACL Data RX: Handle 75 flags 0x02 dlen 12
      SMP: Identity Address Information (0x09) len 7
        Address type: Public (0x00)
        Address: E0:52:33:93:3B:21

Signed-off-by: Szymon Janc <szymon.janc@codecoup.pl>
Tested-by: Maarten Fonville <maarten.fonville@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199461
Cc: stable@vger.kernel.org
---
 net/bluetooth/smp.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index e68c715f8d37..d528d95a2c27 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -2579,6 +2579,20 @@ static int smp_cmd_ident_addr_info(struct l2cap_conn *conn,
 		goto distribute;
 	}
 
+	/*
+	 * Drop IRK if peer is using identity address during pairing but is
+	 * providing different address as identity information.
+	 *
+	 * Microsoft Surface Precision Mouse is known to have this bug.
+	 */
+	if (hci_is_identity_address(&hcon->dst, hcon->dst_type) &&
+	    (bacmp(&info->bdaddr, &hcon->dst) ||
+	     info->addr_type != hcon->dst_type)) {
+		bt_dev_err(hcon->hdev,
+			   "ignoring IRK with invalid identity address");
+		goto distribute;
+	}
+
 	bacpy(&smp->id_addr, &info->bdaddr);
 	smp->id_addr_type = info->addr_type;
 
-- 
2.21.0