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