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References: <20191211015444.143341-1-alainm@chromium.org> <20191211015444.143341-2-alainm@chromium.org>
 <FD1BB2B4-57AA-4B30-BE15-CB27A6649F6A@holtmann.org>
In-Reply-To: <FD1BB2B4-57AA-4B30-BE15-CB27A6649F6A@holtmann.org>
From:   Alain Michaud <alainmichaud@google.com>
Date:   Wed, 11 Dec 2019 09:41:08 -0500
Message-ID: <CALWDO_X2M9GiP7pZa+BR-myEVjrS7i=+mNrxivSWh4Ur2pCA8w@mail.gmail.com>
Subject: Re: [PATCH v3 2/2] Implementation of MGMT_OP_SET_BLOCKED_KEYS.
To:     Marcel Holtmann <marcel@holtmann.org>
Cc:     Alain Michaud <alainm@chromium.org>,
        BlueZ <linux-bluetooth@vger.kernel.org>
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Sender: linux-bluetooth-owner@vger.kernel.org
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On Wed, Dec 11, 2019 at 5:33 AM Marcel Holtmann <marcel@holtmann.org> wrote=
:
>
> Hi Alain,
>
> > MGMT command is added to receive the list of blocked keys from
> > user-space.
> >
> > The list is used to:
> > 1) Block keys from being distributed by the device during
> >   the ke distribution phase of SMP.
> > 2) Filter out any keys that were previously saved so
> >   they are no longer used.
> >
> > Signed-off-by: Alain Michaud <alainm@chromium.org>
> > ---
> >
> > include/net/bluetooth/hci_core.h | 10 ++++
> > include/net/bluetooth/mgmt.h     | 17 +++++++
> > net/bluetooth/hci_core.c         | 85 +++++++++++++++++++++++++++++---
> > net/bluetooth/hci_debugfs.c      | 18 +++++++
> > net/bluetooth/mgmt.c             | 53 ++++++++++++++++++++
> > net/bluetooth/smp.c              | 18 +++++++
> > 6 files changed, 193 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/h=
ci_core.h
> > index b689aceb636b..9020fa3c4d30 100644
> > --- a/include/net/bluetooth/hci_core.h
> > +++ b/include/net/bluetooth/hci_core.h
> > @@ -118,6 +118,13 @@ struct bt_uuid {
> >       u8 svc_hint;
> > };
> >
> > +struct blocked_key {
> > +     struct list_head list;
> > +     struct rcu_head rcu;
> > +     u8 type;
> > +     u8 val[16];
> > +};
> > +
> > struct smp_csrk {
> >       bdaddr_t bdaddr;
> >       u8 bdaddr_type;
> > @@ -397,6 +404,7 @@ struct hci_dev {
> >       struct list_head        le_conn_params;
> >       struct list_head        pend_le_conns;
> >       struct list_head        pend_le_reports;
> > +     struct list_head        blocked_keys;
> >
> >       struct hci_dev_stats    stat;
> >
> > @@ -1121,6 +1129,8 @@ struct smp_irk *hci_find_irk_by_addr(struct hci_d=
ev *hdev, bdaddr_t *bdaddr,
> > struct smp_irk *hci_add_irk(struct hci_dev *hdev, bdaddr_t *bdaddr,
> >                           u8 addr_type, u8 val[16], bdaddr_t *rpa);
> > void hci_remove_irk(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 addr_typ=
e);
> > +bool hci_is_blocked_key(struct hci_dev *hdev, u8 type, u8 val[16]);
> > +void hci_blocked_keys_clear(struct hci_dev *hdev);
> > void hci_smp_irks_clear(struct hci_dev *hdev);
> >
> > bool hci_bdaddr_is_paired(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 ty=
pe);
> > diff --git a/include/net/bluetooth/mgmt.h b/include/net/bluetooth/mgmt.=
h
> > index 9cee7ddc6741..c9b1d39d6d6c 100644
> > --- a/include/net/bluetooth/mgmt.h
> > +++ b/include/net/bluetooth/mgmt.h
> > @@ -654,6 +654,23 @@ struct mgmt_cp_set_phy_confguration {
> > } __packed;
> > #define MGMT_SET_PHY_CONFIGURATION_SIZE       4
> >
> > +#define MGMT_OP_SET_BLOCKED_KEYS     0x0046
> > +
> > +#define HCI_BLOCKED_KEY_TYPE_LINKKEY 0x00
> > +#define HCI_BLOCKED_KEY_TYPE_LTK             0x01
> > +#define HCI_BLOCKED_KEY_TYPE_IRK             0x02
> > +
> > +struct mgmt_blocked_key_info {
> > +     __u8 type;
> > +     __u8 val[16];
> > +} __packed;
> > +
> > +struct mgmt_cp_set_blocked_keys {
> > +     __le16 key_count;
> > +     struct mgmt_blocked_key_info keys[0];
> > +} __packed;
> > +#define MGMT_OP_SET_BLOCKED_KEYS_SIZE 0
> > +
> > #define MGMT_EV_CMD_COMPLETE          0x0001
> > struct mgmt_ev_cmd_complete {
> >       __le16  opcode;
> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > index 9e19d5a3aac8..0598fa66037e 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -2311,6 +2311,33 @@ void hci_smp_irks_clear(struct hci_dev *hdev)
> >       }
> > }
> >
> > +void hci_blocked_keys_clear(struct hci_dev *hdev)
> > +{
> > +     struct blocked_key *b;
> > +
> > +     list_for_each_entry_rcu(b, &hdev->blocked_keys, list) {
> > +             list_del_rcu(&b->list);
> > +             kfree_rcu(b, rcu);
> > +     }
> > +}
> > +
> > +bool hci_is_blocked_key(struct hci_dev *hdev, u8 type, u8 val[16])
> > +{
> > +     bool blocked =3D false;
> > +     struct blocked_key *b;
> > +
> > +     rcu_read_lock();
> > +     list_for_each_entry(b, &hdev->blocked_keys, list) {
> > +             if (b->type =3D=3D type && !memcmp(b->val, val, sizeof(b-=
>val))) {
> > +                     blocked =3D true;
> > +                     break;
> > +             }
> > +     }
> > +
> > +     rcu_read_unlock();
> > +     return blocked;
> > +}
> > +
> > struct link_key *hci_find_link_key(struct hci_dev *hdev, bdaddr_t *bdad=
dr)
> > {
> >       struct link_key *k;
> > @@ -2319,6 +2346,16 @@ struct link_key *hci_find_link_key(struct hci_de=
v *hdev, bdaddr_t *bdaddr)
> >       list_for_each_entry_rcu(k, &hdev->link_keys, list) {
> >               if (bacmp(bdaddr, &k->bdaddr) =3D=3D 0) {
> >                       rcu_read_unlock();
> > +
> > +                     if (hci_is_blocked_key(hdev,
> > +                                            HCI_BLOCKED_KEY_TYPE_LINKK=
EY,
> > +                                            k->val)) {
> > +                             bt_dev_warn_ratelimited(hdev,
> > +                                                     "Link key blocked=
 for %pMR",
> > +                                                     &k->bdaddr);
> > +                             return NULL;
> > +                     }
> > +
> >                       return k;
> >               }
> >       }
> > @@ -2387,6 +2424,15 @@ struct smp_ltk *hci_find_ltk(struct hci_dev *hde=
v, bdaddr_t *bdaddr,
> >
> >               if (smp_ltk_is_sc(k) || ltk_role(k->type) =3D=3D role) {
> >                       rcu_read_unlock();
> > +
> > +                     if (hci_is_blocked_key(hdev, HCI_BLOCKED_KEY_TYPE=
_LTK,
> > +                                            k->val)) {
> > +                             bt_dev_warn_ratelimited(hdev,
> > +                                                     "LTK blocked for =
%pMR",
> > +                                                     &k->bdaddr);
> > +                             return NULL;
> > +                     }
> > +
> >                       return k;
> >               }
> >       }
> > @@ -2397,31 +2443,42 @@ struct smp_ltk *hci_find_ltk(struct hci_dev *hd=
ev, bdaddr_t *bdaddr,
> >
> > struct smp_irk *hci_find_irk_by_rpa(struct hci_dev *hdev, bdaddr_t *rpa=
)
> > {
> > +     struct smp_irk *irk_to_return =3D NULL;
> >       struct smp_irk *irk;
> >
> >       rcu_read_lock();
> >       list_for_each_entry_rcu(irk, &hdev->identity_resolving_keys, list=
) {
> >               if (!bacmp(&irk->rpa, rpa)) {
> > -                     rcu_read_unlock();
> > -                     return irk;
> > +                     irk_to_return =3D irk;
>
> tell me why you use irk_to_return variable here instead of just utilizing=
 the irk?
[alain] I used a different variable to avoid the case where "irk" (the
iterator) will point to the last entry in the list, but doesn't
correspond to a match.  However, there is clearly a bug here since
irk_to_return can be null and will be deref'd in the check.  I will
fix this.
>
> > +                     goto done;
> >               }
> >       }
> >
> >       list_for_each_entry_rcu(irk, &hdev->identity_resolving_keys, list=
) {
> >               if (smp_irk_matches(hdev, irk->val, rpa)) {
> >                       bacpy(&irk->rpa, rpa);
> > -                     rcu_read_unlock();
> > -                     return irk;
> > +                     irk_to_return =3D irk;
> > +                     goto done;
> >               }
> >       }
> > +
> > +done:
> > +     if (hci_is_blocked_key(hdev, HCI_BLOCKED_KEY_TYPE_IRK,
> > +                            irk_to_return->val)) {
> > +             bt_dev_warn_ratelimited(hdev, "Identity key blocked for %=
pMR",
> > +                                     &irk_to_return->bdaddr);
> > +             irk_to_return =3D NULL;
> > +     }
> > +
> >       rcu_read_unlock();
>
> Especially if you leave the rcu_read_unlock after checking the if the IRK=
 is blocked.
[alain] I hope the first response helps answer this question as well.

>
> >
> > -     return NULL;
> > +     return irk_to_return;
> > }
> >
> > struct smp_irk *hci_find_irk_by_addr(struct hci_dev *hdev, bdaddr_t *bd=
addr,
> >                                    u8 addr_type)
> > {
> > +     struct smp_irk *irk_to_return =3D NULL;
> >       struct smp_irk *irk;
> >
> >       /* Identity Address must be public or static random */
> > @@ -2432,13 +2489,23 @@ struct smp_irk *hci_find_irk_by_addr(struct hci=
_dev *hdev, bdaddr_t *bdaddr,
> >       list_for_each_entry_rcu(irk, &hdev->identity_resolving_keys, list=
) {
> >               if (addr_type =3D=3D irk->addr_type &&
> >                   bacmp(bdaddr, &irk->bdaddr) =3D=3D 0) {
> > -                     rcu_read_unlock();
> > -                     return irk;
> > +                     irk_to_return =3D irk;
> > +                     goto done;
> >               }
> >       }
> > +
> > +done:
> > +
> > +     if (hci_is_blocked_key(hdev, HCI_BLOCKED_KEY_TYPE_IRK,
> > +                            irk_to_return->val)) {
> > +             bt_dev_warn_ratelimited(hdev, "Identity key blocked for %=
pMR",
> > +                                     &irk_to_return->bdaddr);
> > +             irk_to_return =3D NULL;
> > +     }
> > +
> >       rcu_read_unlock();
> >
> > -     return NULL;
> > +     return irk_to_return;
> > }
> >
> > struct link_key *hci_add_link_key(struct hci_dev *hdev, struct hci_conn=
 *conn,
> > @@ -3244,6 +3311,7 @@ struct hci_dev *hci_alloc_dev(void)
> >       INIT_LIST_HEAD(&hdev->pend_le_reports);
> >       INIT_LIST_HEAD(&hdev->conn_hash.list);
> >       INIT_LIST_HEAD(&hdev->adv_instances);
> > +     INIT_LIST_HEAD(&hdev->blocked_keys);
> >
> >       INIT_WORK(&hdev->rx_work, hci_rx_work);
> >       INIT_WORK(&hdev->cmd_work, hci_cmd_work);
> > @@ -3443,6 +3511,7 @@ void hci_unregister_dev(struct hci_dev *hdev)
> >       hci_bdaddr_list_clear(&hdev->le_resolv_list);
> >       hci_conn_params_clear_all(hdev);
> >       hci_discovery_filter_clear(hdev);
> > +     hci_blocked_keys_clear(hdev);
> >       hci_dev_unlock(hdev);
> >
> >       hci_dev_put(hdev);
> > diff --git a/net/bluetooth/hci_debugfs.c b/net/bluetooth/hci_debugfs.c
> > index 402e2cc54044..f9b4df56f166 100644
> > --- a/net/bluetooth/hci_debugfs.c
> > +++ b/net/bluetooth/hci_debugfs.c
> > @@ -152,6 +152,22 @@ static int blacklist_show(struct seq_file *f, void=
 *p)
> >
> > DEFINE_SHOW_ATTRIBUTE(blacklist);
> >
> > +static int blocked_keys_show(struct seq_file *f, void *p)
> > +{
> > +     struct hci_dev *hdev =3D f->private;
> > +     struct blocked_key *key;
> > +
> > +     rcu_read_lock();
> > +     list_for_each_entry_rcu(key, &hdev->blocked_keys, list)
> > +             seq_printf(f, "%u %*phN\n", key->type, (int)sizeof(key->v=
al),
>
> Just use 16 here instead of a complicated sizeof. We have done that with =
IRK list as well.
[alain] ok.
>
> > +                        key->val);
> > +     rcu_read_unlock();
> > +
> > +     return 0;
> > +}
> > +
> > +DEFINE_SHOW_ATTRIBUTE(blocked_keys);
> > +
> > static int uuids_show(struct seq_file *f, void *p)
> > {
> >       struct hci_dev *hdev =3D f->private;
> > @@ -308,6 +324,8 @@ void hci_debugfs_create_common(struct hci_dev *hdev=
)
> >                           &device_list_fops);
> >       debugfs_create_file("blacklist", 0444, hdev->debugfs, hdev,
> >                           &blacklist_fops);
> > +     debugfs_create_file("blocked_keys", 0444, hdev->debugfs, hdev,
> > +                         &blocked_keys_fops);
> >       debugfs_create_file("uuids", 0444, hdev->debugfs, hdev, &uuids_fo=
ps);
> >       debugfs_create_file("remote_oob", 0400, hdev->debugfs, hdev,
> >                           &remote_oob_fops);
> > diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
> > index acb7c6d5643f..78864cf645e3 100644
> > --- a/net/bluetooth/mgmt.c
> > +++ b/net/bluetooth/mgmt.c
> > @@ -106,6 +106,7 @@ static const u16 mgmt_commands[] =3D {
> >       MGMT_OP_START_LIMITED_DISCOVERY,
> >       MGMT_OP_READ_EXT_INFO,
> >       MGMT_OP_SET_APPEARANCE,
> > +     MGMT_OP_SET_BLOCKED_KEYS,
> > };
> >
> > static const u16 mgmt_events[] =3D {
> > @@ -3531,6 +3532,57 @@ static int set_phy_configuration(struct sock *sk=
, struct hci_dev *hdev,
> >       return err;
> > }
> >
> > +static int set_blocked_keys(struct sock *sk, struct hci_dev *hdev, voi=
d *data,
> > +                         u16 len)
> > +{
> > +     int err =3D MGMT_STATUS_SUCCESS;
> > +     struct mgmt_cp_set_blocked_keys *keys =3D data;
> > +     const u16 max_key_count =3D ((U16_MAX - sizeof(*keys)) /
> > +                                sizeof(struct mgmt_blocked_key_info));
> > +     u16 key_count, expected_len;
> > +     int i;
> > +
> > +     BT_DBG("request for %s", hdev->name);
> > +
> > +     key_count =3D __le16_to_cpu(keys->key_count);
> > +     if (key_count > max_key_count) {
> > +             bt_dev_err(hdev, "%s: too big key_count value %u", __func=
__,
> > +                        key_count);
>
> These __func__ things belong into debugging code. Remove it please. We do=
n=E2=80=99t use them in errors.
[alain] ok.
>
> > +             return mgmt_cmd_status(sk, hdev->id, MGMT_OP_SET_BLOCKED_=
KEYS,
> > +                                    MGMT_STATUS_INVALID_PARAMS);
> > +     }
> > +
> > +     expected_len =3D struct_size(keys, keys, key_count);
> > +     if (expected_len !=3D len) {
> > +             bt_dev_err(hdev,
> > +                        "%s: expected %u bytes, got %u bytes", __func_=
_,
> > +                        expected_len, len);
> > +             return mgmt_cmd_status(sk, hdev->id, MGMT_OP_SET_BLOCKED_=
KEYS,
> > +                                    MGMT_STATUS_INVALID_PARAMS);
> > +     }
> > +
> > +     hci_dev_lock(hdev);
> > +
> > +     hci_blocked_keys_clear(hdev);
> > +
> > +     for (i =3D 0; i < keys->key_count; ++i) {
> > +             struct blocked_key *b =3D kzalloc(sizeof(*b), GFP_KERNEL)=
;
> > +
> > +             if (!b) {
> > +                     err =3D MGMT_STATUS_NO_RESOURCES;
> > +                     break;
> > +             }
> > +
> > +             b->type =3D keys->keys[i].type;
> > +             memcpy(b->val, keys->keys[i].val, sizeof(b->val));
> > +             list_add_rcu(&b->list, &hdev->blocked_keys);
> > +     }
> > +     hci_dev_unlock(hdev);
> > +
> > +     return mgmt_cmd_complete(sk, hdev->id, MGMT_OP_SET_BLOCKED_KEYS,
> > +                             err, NULL, 0);
> > +}
> > +
> > static void read_local_oob_data_complete(struct hci_dev *hdev, u8 statu=
s,
> >                                        u16 opcode, struct sk_buff *skb)
> > {
> > @@ -6914,6 +6966,7 @@ static const struct hci_mgmt_handler mgmt_handler=
s[] =3D {
> >       { set_appearance,          MGMT_SET_APPEARANCE_SIZE },
> >       { get_phy_configuration,   MGMT_GET_PHY_CONFIGURATION_SIZE },
> >       { set_phy_configuration,   MGMT_SET_PHY_CONFIGURATION_SIZE },
> > +     { set_blocked_keys,        MGMT_OP_SET_BLOCKED_KEYS_SIZE },
> > };
> >
> > void mgmt_index_added(struct hci_dev *hdev)
> > diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
> > index 6b42be4b5861..4ece170c518e 100644
> > --- a/net/bluetooth/smp.c
> > +++ b/net/bluetooth/smp.c
> > @@ -2453,6 +2453,15 @@ static int smp_cmd_encrypt_info(struct l2cap_con=
n *conn, struct sk_buff *skb)
> >       if (skb->len < sizeof(*rp))
> >               return SMP_INVALID_PARAMS;
> >
> > +     /* Pairing is aborted if any blocked keys are distributed */
> > +     if (hci_is_blocked_key(conn->hcon->hdev, HCI_BLOCKED_KEY_TYPE_LTK=
,
> > +                            rp->ltk)) {
> > +             bt_dev_warn_ratelimited(conn->hcon->hdev,
> > +                                     "LTK blocked for %pMR",
> > +                                     &conn->hcon->dst);
> > +             return SMP_INVALID_PARAMS;
> > +     }
> > +
> >       SMP_ALLOW_CMD(smp, SMP_CMD_MASTER_IDENT);
> >
> >       skb_pull(skb, sizeof(*rp));
> > @@ -2509,6 +2518,15 @@ static int smp_cmd_ident_info(struct l2cap_conn =
*conn, struct sk_buff *skb)
> >       if (skb->len < sizeof(*info))
> >               return SMP_INVALID_PARAMS;
> >
> > +     /* Pairing is aborted if any blocked keys are distributed */
> > +     if (hci_is_blocked_key(conn->hcon->hdev, HCI_BLOCKED_KEY_TYPE_IRK=
,
> > +                            info->irk)) {
> > +             bt_dev_warn_ratelimited(conn->hcon->hdev,
> > +                                     "Identity key blocked for %pMR",
> > +                                     &conn->hcon->dst);
> > +             return SMP_INVALID_PARAMS;
> > +     }
> > +
> >       SMP_ALLOW_CMD(smp, SMP_CMD_IDENT_ADDR_INFO);
> >
> >       skb_pull(skb, sizeof(*info));
>
> The rest looks fine.
>
> Regards
>
> Marcel
>