diff mbox series

[1/1] Bluetooth: Fix Just-Works re-pairing

Message ID 20210206141423.13593-2-matias.karhumaa@gmail.com (mailing list archive)
State New, archived
Headers show
Series Bluetooth: Fix Just-Works re-pairing | expand

Commit Message

Matias Karhumaa Feb. 6, 2021, 2:14 p.m. UTC 
Fix Just-Works pairing responder role in case where LTK already exists.
Currently when trying to initiate re-pairing from another device
against Linux using Just-Works, pairing fails due to DHKey check failure
on Linux side. This happens because mackey calculation is skipped
totally if LTK already exists due to logic flaw in
smp_cmd_pairing_random() function.

With this fix mackey is calculated right before requesting confirmation
for Just-Works pairing from userspace which in turn fixes the DHKey
calculation.

Fixes: eed467b517e8 ("Bluetooth: fix passkey uninitialized when used")
Signed-off-by: Matias Karhumaa <matias.karhumaa@gmail.com>
---
 net/bluetooth/smp.c | 37 +++++++++----------------------------
 1 file changed, 9 insertions(+), 28 deletions(-)

Comments

bluez.test.bot@gmail.com Feb. 6, 2021, 3:10 p.m. UTC | #1 
This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=429269

---Test result---

##############################
    Test: CheckPatch - FAIL
    Bluetooth: Fix Just-Works re-pairing
WARNING: Unknown commit id 'eed467b517e8', maybe rebased or not pulled?
#17: 
Fixes: eed467b517e8 ("Bluetooth: fix passkey uninitialized when used")

total: 0 errors, 1 warnings, 0 checks, 57 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

"[PATCH] Bluetooth: Fix Just-Works re-pairing" has style problems, please review.

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.


    ##############################
    Test: CheckGitLint - PASS
    

    ##############################
    Test: CheckBuildK - PASS
    

    ##############################
    Test: CheckTestRunner: Setup - PASS
    

    ##############################
    Test: CheckTestRunner: l2cap-tester - PASS
    Total: 40, Passed: 34 (85.0%), Failed: 0, Not Run: 6

    ##############################
    Test: CheckTestRunner: bnep-tester - PASS
    Total: 1, Passed: 1 (100.0%), Failed: 0, Not Run: 0

    ##############################
    Test: CheckTestRunner: mgmt-tester - PASS
    Total: 416, Passed: 402 (96.6%), Failed: 0, Not Run: 14

    ##############################
    Test: CheckTestRunner: rfcomm-tester - PASS
    Total: 9, Passed: 9 (100.0%), Failed: 0, Not Run: 0

    ##############################
    Test: CheckTestRunner: sco-tester - PASS
    Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0

    ##############################
    Test: CheckTestRunner: smp-tester - PASS
    Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0

    ##############################
    Test: CheckTestRunner: userchan-tester - PASS
    Total: 3, Passed: 3 (100.0%), Failed: 0, Not Run: 0

    

---
Regards,
Linux Bluetooth
Marcel Holtmann Feb. 8, 2021, 1:50 p.m. UTC | #2 
Hi Matias,

> Fix Just-Works pairing responder role in case where LTK already exists.
> Currently when trying to initiate re-pairing from another device
> against Linux using Just-Works, pairing fails due to DHKey check failure
> on Linux side. This happens because mackey calculation is skipped
> totally if LTK already exists due to logic flaw in
> smp_cmd_pairing_random() function.
> 
> With this fix mackey is calculated right before requesting confirmation
> for Just-Works pairing from userspace which in turn fixes the DHKey
> calculation.
> 
> Fixes: eed467b517e8 ("Bluetooth: fix passkey uninitialized when used")
> Signed-off-by: Matias Karhumaa <matias.karhumaa@gmail.com>
> ---
> net/bluetooth/smp.c | 37 +++++++++----------------------------
> 1 file changed, 9 insertions(+), 28 deletions(-)
> 
> diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
> index b0c1ee110eff..c3ea50fcac6d 100644
> --- a/net/bluetooth/smp.c
> +++ b/net/bluetooth/smp.c
> @@ -2122,7 +2122,7 @@ static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
> 	struct smp_chan *smp = chan->data;
> 	struct hci_conn *hcon = conn->hcon;
> 	u8 *pkax, *pkbx, *na, *nb, confirm_hint;
> -	u32 passkey;
> +	u32 passkey = 0;
> 	int err;
> 
> 	BT_DBG("conn %p", conn);
> @@ -2174,24 +2174,6 @@ static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
> 		smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(smp->prnd),
> 			     smp->prnd);
> 		SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
> -
> -		/* Only Just-Works pairing requires extra checks */
> -		if (smp->method != JUST_WORKS)
> -			goto mackey_and_ltk;
> -
> -		/* If there already exists long term key in local host, leave
> -		 * the decision to user space since the remote device could
> -		 * be legitimate or malicious.
> -		 */
> -		if (hci_find_ltk(hcon->hdev, &hcon->dst, hcon->dst_type,
> -				 hcon->role)) {
> -			/* Set passkey to 0. The value can be any number since
> -			 * it'll be ignored anyway.
> -			 */
> -			passkey = 0;
> -			confirm_hint = 1;
> -			goto confirm;
> -		}
> 	}

I have a concern if we just remove such a comment. I think the commit message needs a bit more explanatory and this needs a few more reviews.

Regards

Marcel
Matias Karhumaa Feb. 8, 2021, 10:08 p.m. UTC | #3 
Hi Marcel,

> I have a concern if we just remove such a comment. I think the commit message needs a bit more explanatory and this needs a few more reviews.

Thanks for taking time to look into this. I have just sent v2
addressing your comments.

Best regards,
Matias Karhumaa
diff mbox series

Patch

diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index b0c1ee110eff..c3ea50fcac6d 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -2122,7 +2122,7 @@  static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
 	struct smp_chan *smp = chan->data;
 	struct hci_conn *hcon = conn->hcon;
 	u8 *pkax, *pkbx, *na, *nb, confirm_hint;
-	u32 passkey;
+	u32 passkey = 0;
 	int err;
 
 	BT_DBG("conn %p", conn);
@@ -2174,24 +2174,6 @@  static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
 		smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(smp->prnd),
 			     smp->prnd);
 		SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
-
-		/* Only Just-Works pairing requires extra checks */
-		if (smp->method != JUST_WORKS)
-			goto mackey_and_ltk;
-
-		/* If there already exists long term key in local host, leave
-		 * the decision to user space since the remote device could
-		 * be legitimate or malicious.
-		 */
-		if (hci_find_ltk(hcon->hdev, &hcon->dst, hcon->dst_type,
-				 hcon->role)) {
-			/* Set passkey to 0. The value can be any number since
-			 * it'll be ignored anyway.
-			 */
-			passkey = 0;
-			confirm_hint = 1;
-			goto confirm;
-		}
 	}
 
 mackey_and_ltk:
@@ -2206,17 +2188,16 @@  static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
 			SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
 		}
 		return 0;
-	}
-
-	err = smp_g2(smp->tfm_cmac, pkax, pkbx, na, nb, &passkey);
-	if (err)
-		return SMP_UNSPECIFIED;
-
-	confirm_hint = 0;
+	} else if (smp->method != JUST_WORKS) {
+		err = smp_g2(smp->tfm_cmac, pkax, pkbx, na, nb, &passkey);
+		if (err)
+			return SMP_UNSPECIFIED;
 
-confirm:
-	if (smp->method == JUST_WORKS)
+		confirm_hint = 0;
+	} else {
+		/* Just-Works needs hint for userspace */
 		confirm_hint = 1;
+	}
 
 	err = mgmt_user_confirm_request(hcon->hdev, &hcon->dst, hcon->type,
 					hcon->dst_type, passkey, confirm_hint);