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* [Bluez PATCH v1] bluetooth: secure bluetooth stack from bluedump attack
@ 2020-01-06 10:14 howardchung
       [not found] ` <CAMCGoNzCvOgcg0hAhDO-wcFLgX75JL-G6q1KuGFEjrEz+oPTxA@mail.gmail.com>
  2020-01-08 21:02 ` Marcel Holtmann
  0 siblings, 2 replies; 6+ messages in thread
From: howardchung @ 2020-01-06 10:14 UTC (permalink / raw)
  To: linux-bluetooth, marcel
  Cc: chromeos-bluetooth-upstreaming, howardchung, David S. Miller,
	Johan Hedberg, netdev, linux-kernel

From: howardchung <howardchung@google.com>

Attack scenario:
1. A Chromebook (let's call this device A) is paired to a legitimate
   Bluetooth classic device (e.g. a speaker) (let's call this device
   B).
2. A malicious device (let's call this device C) pretends to be the
   Bluetooth speaker by using the same BT address.
3. If device A is not currently connected to device B, device A will
   be ready to accept connection from device B in the background
   (technically, doing Page Scan).
4. Therefore, device C can initiate connection to device A
   (because device A is doing Page Scan) and device A will accept the
   connection because device A trusts device C's address which is the
   same as device B's address.
5. Device C won't be able to communicate at any high level Bluetooth
   profile with device A because device A enforces that device C is
   encrypted with their common Link Key, which device C doesn't have.
   But device C can initiate pairing with device A with just-works
   model without requiring user interaction (there is only pairing
   notification). After pairing, device A now trusts device C with a
   new different link key, common between device A and C.
6. From now on, device A trusts device C, so device C can at anytime
   connect to device A to do any kind of high-level hijacking, e.g.
   speaker hijack or mouse/keyboard hijack.

To fix this, reject the pairing if all the conditions below are met.
- the pairing is initialized by peer
- the authorization method is just-work
- host already had the link key to the peer

Also create a debugfs option to permit the pairing even the
conditions above are met.

Signed-off-by: howardchung <howardchung@google.com>
---

 include/net/bluetooth/hci.h |  1 +
 net/bluetooth/hci_core.c    | 47 +++++++++++++++++++++++++++++++++++++
 net/bluetooth/hci_event.c   | 12 ++++++++++
 3 files changed, 60 insertions(+)

diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 07b6ecedc6ce..4918b79baa41 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -283,6 +283,7 @@ enum {
 	HCI_FORCE_STATIC_ADDR,
 	HCI_LL_RPA_RESOLUTION,
 	HCI_CMD_PENDING,
+	HCI_PERMIT_JUST_WORK_REPAIR,
 
 	__HCI_NUM_FLAGS,
 };
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 9e19d5a3aac8..9014aa567e7b 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -172,10 +172,57 @@ static const struct file_operations vendor_diag_fops = {
 	.llseek		= default_llseek,
 };
 
+static ssize_t permit_just_work_repair_read(struct file *file,
+					    char __user *user_buf,
+					    size_t count, loff_t *ppos)
+{
+	struct hci_dev *hdev = file->private_data;
+	char buf[3];
+
+	buf[0] = hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) ? 'Y'
+								      : 'N';
+	buf[1] = '\n';
+	buf[2] = '\0';
+	return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
+}
+
+static ssize_t permit_just_work_repair_write(struct file *file,
+					     const char __user *user_buf,
+					     size_t count, loff_t *ppos)
+{
+	struct hci_dev *hdev = file->private_data;
+	char buf[32];
+	size_t buf_size = min(count, (sizeof(buf) - 1));
+	bool enable;
+
+	if (copy_from_user(buf, user_buf, buf_size))
+		return -EFAULT;
+
+	buf[buf_size] = '\0';
+	if (strtobool(buf, &enable))
+		return -EINVAL;
+
+	if (enable)
+		hci_dev_set_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
+	else
+		hci_dev_clear_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
+
+	return count;
+}
+
+static const struct file_operations permit_just_work_repair_fops = {
+	.open		= simple_open,
+	.read		= permit_just_work_repair_read,
+	.write		= permit_just_work_repair_write,
+	.llseek		= default_llseek,
+};
+
 static void hci_debugfs_create_basic(struct hci_dev *hdev)
 {
 	debugfs_create_file("dut_mode", 0644, hdev->debugfs, hdev,
 			    &dut_mode_fops);
+	debugfs_create_file("permit_just_work_repair", 0644, hdev->debugfs,
+			    hdev, &permit_just_work_repair_fops);
 
 	if (hdev->set_diag)
 		debugfs_create_file("vendor_diag", 0644, hdev->debugfs, hdev,
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 6ddc4a74a5e4..898e347e19e0 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4539,6 +4539,18 @@ static void hci_user_confirm_request_evt(struct hci_dev *hdev,
 		goto unlock;
 	}
 
+	/* If there already exists link key in local host, terminate the
+	 * connection by default since the remote device could be malicious.
+	 * Permit the connection if permit_just_work_repair is enabled.
+	 */
+	if (!hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) &&
+	    hci_find_link_key(hdev, &ev->bdaddr)) {
+		BT_DBG("Rejecting request: local host already have link key");
+		hci_send_cmd(hdev, HCI_OP_USER_CONFIRM_NEG_REPLY,
+			     sizeof(ev->bdaddr), &ev->bdaddr);
+		goto unlock;
+	}
+
 	/* If no side requires MITM protection; auto-accept */
 	if ((!loc_mitm || conn->remote_cap == HCI_IO_NO_INPUT_OUTPUT) &&
 	    (!rem_mitm || conn->io_capability == HCI_IO_NO_INPUT_OUTPUT)) {
-- 
2.24.1.735.g03f4e72817-goog


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Fwd: [Bluez PATCH v1] bluetooth: secure bluetooth stack from bluedump attack
       [not found] ` <CAMCGoNzCvOgcg0hAhDO-wcFLgX75JL-G6q1KuGFEjrEz+oPTxA@mail.gmail.com>
@ 2020-01-06 11:44   ` " Matias Karhumaa
  2020-01-07  3:30     ` Yun-hao Chung
  0 siblings, 1 reply; 6+ messages in thread
From: Matias Karhumaa @ 2020-01-06 11:44 UTC (permalink / raw)
  To: howardchung
  Cc: chromeos-bluetooth-upstreaming, David S. Miller, Johan Hedberg,
	linux-bluetooth, linux-kernel, Marcel Holtmann, netdev

Hi Howard,

Re-sending as plain text.

This same attack scenario works also against Ubuntu 18.04 at least.

ma 6. tammik. 2020 klo 12.17 howardchung@google.com
(howardchung@google.com) kirjoitti:
>
> From: howardchung <howardchung@google.com>
>
> Attack scenario:
> 1. A Chromebook (let's call this device A) is paired to a legitimate
>    Bluetooth classic device (e.g. a speaker) (let's call this device
>    B).
> 2. A malicious device (let's call this device C) pretends to be the
>    Bluetooth speaker by using the same BT address.
> 3. If device A is not currently connected to device B, device A will
>    be ready to accept connection from device B in the background
>    (technically, doing Page Scan).
> 4. Therefore, device C can initiate connection to device A
>    (because device A is doing Page Scan) and device A will accept the
>    connection because device A trusts device C's address which is the
>    same as device B's address.
> 5. Device C won't be able to communicate at any high level Bluetooth
>    profile with device A because device A enforces that device C is
>    encrypted with their common Link Key, which device C doesn't have.
>    But device C can initiate pairing with device A with just-works
>    model without requiring user interaction (there is only pairing
>    notification). After pairing, device A now trusts device C with a
>    new different link key, common between device A and C.
> 6. From now on, device A trusts device C, so device C can at anytime
>    connect to device A to do any kind of high-level hijacking, e.g.
>    speaker hijack or mouse/keyboard hijack.
>
> To fix this, reject the pairing if all the conditions below are met.
> - the pairing is initialized by peer
> - the authorization method is just-work
> - host already had the link key to the peer
>
> Also create a debugfs option to permit the pairing even the
> conditions above are met.
>
> Signed-off-by: howardchung <howardchung@google.com>
> ---
>
>  include/net/bluetooth/hci.h |  1 +
>  net/bluetooth/hci_core.c    | 47 +++++++++++++++++++++++++++++++++++++
>  net/bluetooth/hci_event.c   | 12 ++++++++++
>  3 files changed, 60 insertions(+)
>
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index 07b6ecedc6ce..4918b79baa41 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -283,6 +283,7 @@ enum {
>         HCI_FORCE_STATIC_ADDR,
>         HCI_LL_RPA_RESOLUTION,
>         HCI_CMD_PENDING,
> +       HCI_PERMIT_JUST_WORK_REPAIR,
>
>         __HCI_NUM_FLAGS,
>  };
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 9e19d5a3aac8..9014aa567e7b 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -172,10 +172,57 @@ static const struct file_operations vendor_diag_fops = {
>         .llseek         = default_llseek,
>  };
>
> +static ssize_t permit_just_work_repair_read(struct file *file,
> +                                           char __user *user_buf,
> +                                           size_t count, loff_t *ppos)
> +{
> +       struct hci_dev *hdev = file->private_data;
> +       char buf[3];
> +
> +       buf[0] = hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) ? 'Y'
> +                                                                     : 'N';
> +       buf[1] = '\n';
> +       buf[2] = '\0';
> +       return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
> +}
> +
> +static ssize_t permit_just_work_repair_write(struct file *file,
> +                                            const char __user *user_buf,
> +                                            size_t count, loff_t *ppos)
> +{
> +       struct hci_dev *hdev = file->private_data;
> +       char buf[32];
> +       size_t buf_size = min(count, (sizeof(buf) - 1));
> +       bool enable;
> +
> +       if (copy_from_user(buf, user_buf, buf_size))
> +               return -EFAULT;
> +
> +       buf[buf_size] = '\0';
> +       if (strtobool(buf, &enable))
> +               return -EINVAL;
> +
> +       if (enable)
> +               hci_dev_set_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
> +       else
> +               hci_dev_clear_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
> +
> +       return count;
> +}
> +
> +static const struct file_operations permit_just_work_repair_fops = {
> +       .open           = simple_open,
> +       .read           = permit_just_work_repair_read,
> +       .write          = permit_just_work_repair_write,
> +       .llseek         = default_llseek,
> +};
> +
>  static void hci_debugfs_create_basic(struct hci_dev *hdev)
>  {
>         debugfs_create_file("dut_mode", 0644, hdev->debugfs, hdev,
>                             &dut_mode_fops);
> +       debugfs_create_file("permit_just_work_repair", 0644, hdev->debugfs,
> +                           hdev, &permit_just_work_repair_fops);
>
>         if (hdev->set_diag)
>                 debugfs_create_file("vendor_diag", 0644, hdev->debugfs, hdev,
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 6ddc4a74a5e4..898e347e19e0 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -4539,6 +4539,18 @@ static void hci_user_confirm_request_evt(struct hci_dev *hdev,
>                 goto unlock;
>         }
>
> +       /* If there already exists link key in local host, terminate the
> +        * connection by default since the remote device could be malicious.
> +        * Permit the connection if permit_just_work_repair is enabled.
> +        */
> +       if (!hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) &&
> +           hci_find_link_key(hdev, &ev->bdaddr)) {
> +               BT_DBG("Rejecting request: local host already have link key");
> +               hci_send_cmd(hdev, HCI_OP_USER_CONFIRM_NEG_REPLY,

Why wouldn't we just request authorization from userspace in case we
already have link key? I think that is how it works on other
platforms.
>
> +                            sizeof(ev->bdaddr), &ev->bdaddr);
> +               goto unlock;
> +       }
> +
>         /* If no side requires MITM protection; auto-accept */
>         if ((!loc_mitm || conn->remote_cap == HCI_IO_NO_INPUT_OUTPUT) &&
>             (!rem_mitm || conn->io_capability == HCI_IO_NO_INPUT_OUTPUT)) {
> --
> 2.24.1.735.g03f4e72817-goog


Best regard,
Matias Karhumaa

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [Bluez PATCH v1] bluetooth: secure bluetooth stack from bluedump attack
  2020-01-06 11:44   ` Fwd: " Matias Karhumaa
@ 2020-01-07  3:30     ` Yun-hao Chung
  0 siblings, 0 replies; 6+ messages in thread
From: Yun-hao Chung @ 2020-01-07  3:30 UTC (permalink / raw)
  To: Matias Karhumaa
  Cc: chromeos-bluetooth-upstreaming, David S. Miller, Johan Hedberg,
	linux-bluetooth, linux-kernel, Marcel Holtmann, netdev

Hi Matias,

Thanks for the comment.
I think in the just-work case, if we ask user for confirmation, they
will likely just accept it.
Rejecting the pairing immediately is more secure.

Thanks,
Howard

On Mon, Jan 6, 2020 at 7:44 PM Matias Karhumaa
<matias.karhumaa@gmail.com> wrote:
>
> Hi Howard,
>
> Re-sending as plain text.
>
> This same attack scenario works also against Ubuntu 18.04 at least.
>
> ma 6. tammik. 2020 klo 12.17 howardchung@google.com
> (howardchung@google.com) kirjoitti:
> >
> > From: howardchung <howardchung@google.com>
> >
> > Attack scenario:
> > 1. A Chromebook (let's call this device A) is paired to a legitimate
> >    Bluetooth classic device (e.g. a speaker) (let's call this device
> >    B).
> > 2. A malicious device (let's call this device C) pretends to be the
> >    Bluetooth speaker by using the same BT address.
> > 3. If device A is not currently connected to device B, device A will
> >    be ready to accept connection from device B in the background
> >    (technically, doing Page Scan).
> > 4. Therefore, device C can initiate connection to device A
> >    (because device A is doing Page Scan) and device A will accept the
> >    connection because device A trusts device C's address which is the
> >    same as device B's address.
> > 5. Device C won't be able to communicate at any high level Bluetooth
> >    profile with device A because device A enforces that device C is
> >    encrypted with their common Link Key, which device C doesn't have.
> >    But device C can initiate pairing with device A with just-works
> >    model without requiring user interaction (there is only pairing
> >    notification). After pairing, device A now trusts device C with a
> >    new different link key, common between device A and C.
> > 6. From now on, device A trusts device C, so device C can at anytime
> >    connect to device A to do any kind of high-level hijacking, e.g.
> >    speaker hijack or mouse/keyboard hijack.
> >
> > To fix this, reject the pairing if all the conditions below are met.
> > - the pairing is initialized by peer
> > - the authorization method is just-work
> > - host already had the link key to the peer
> >
> > Also create a debugfs option to permit the pairing even the
> > conditions above are met.
> >
> > Signed-off-by: howardchung <howardchung@google.com>
> > ---
> >
> >  include/net/bluetooth/hci.h |  1 +
> >  net/bluetooth/hci_core.c    | 47 +++++++++++++++++++++++++++++++++++++
> >  net/bluetooth/hci_event.c   | 12 ++++++++++
> >  3 files changed, 60 insertions(+)
> >
> > diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> > index 07b6ecedc6ce..4918b79baa41 100644
> > --- a/include/net/bluetooth/hci.h
> > +++ b/include/net/bluetooth/hci.h
> > @@ -283,6 +283,7 @@ enum {
> >         HCI_FORCE_STATIC_ADDR,
> >         HCI_LL_RPA_RESOLUTION,
> >         HCI_CMD_PENDING,
> > +       HCI_PERMIT_JUST_WORK_REPAIR,
> >
> >         __HCI_NUM_FLAGS,
> >  };
> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > index 9e19d5a3aac8..9014aa567e7b 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -172,10 +172,57 @@ static const struct file_operations vendor_diag_fops = {
> >         .llseek         = default_llseek,
> >  };
> >
> > +static ssize_t permit_just_work_repair_read(struct file *file,
> > +                                           char __user *user_buf,
> > +                                           size_t count, loff_t *ppos)
> > +{
> > +       struct hci_dev *hdev = file->private_data;
> > +       char buf[3];
> > +
> > +       buf[0] = hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) ? 'Y'
> > +                                                                     : 'N';
> > +       buf[1] = '\n';
> > +       buf[2] = '\0';
> > +       return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
> > +}
> > +
> > +static ssize_t permit_just_work_repair_write(struct file *file,
> > +                                            const char __user *user_buf,
> > +                                            size_t count, loff_t *ppos)
> > +{
> > +       struct hci_dev *hdev = file->private_data;
> > +       char buf[32];
> > +       size_t buf_size = min(count, (sizeof(buf) - 1));
> > +       bool enable;
> > +
> > +       if (copy_from_user(buf, user_buf, buf_size))
> > +               return -EFAULT;
> > +
> > +       buf[buf_size] = '\0';
> > +       if (strtobool(buf, &enable))
> > +               return -EINVAL;
> > +
> > +       if (enable)
> > +               hci_dev_set_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
> > +       else
> > +               hci_dev_clear_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
> > +
> > +       return count;
> > +}
> > +
> > +static const struct file_operations permit_just_work_repair_fops = {
> > +       .open           = simple_open,
> > +       .read           = permit_just_work_repair_read,
> > +       .write          = permit_just_work_repair_write,
> > +       .llseek         = default_llseek,
> > +};
> > +
> >  static void hci_debugfs_create_basic(struct hci_dev *hdev)
> >  {
> >         debugfs_create_file("dut_mode", 0644, hdev->debugfs, hdev,
> >                             &dut_mode_fops);
> > +       debugfs_create_file("permit_just_work_repair", 0644, hdev->debugfs,
> > +                           hdev, &permit_just_work_repair_fops);
> >
> >         if (hdev->set_diag)
> >                 debugfs_create_file("vendor_diag", 0644, hdev->debugfs, hdev,
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index 6ddc4a74a5e4..898e347e19e0 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -4539,6 +4539,18 @@ static void hci_user_confirm_request_evt(struct hci_dev *hdev,
> >                 goto unlock;
> >         }
> >
> > +       /* If there already exists link key in local host, terminate the
> > +        * connection by default since the remote device could be malicious.
> > +        * Permit the connection if permit_just_work_repair is enabled.
> > +        */
> > +       if (!hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) &&
> > +           hci_find_link_key(hdev, &ev->bdaddr)) {
> > +               BT_DBG("Rejecting request: local host already have link key");
> > +               hci_send_cmd(hdev, HCI_OP_USER_CONFIRM_NEG_REPLY,
>
> Why wouldn't we just request authorization from userspace in case we
> already have link key? I think that is how it works on other
> platforms.
> >
> > +                            sizeof(ev->bdaddr), &ev->bdaddr);
> > +               goto unlock;
> > +       }
> > +
> >         /* If no side requires MITM protection; auto-accept */
> >         if ((!loc_mitm || conn->remote_cap == HCI_IO_NO_INPUT_OUTPUT) &&
> >             (!rem_mitm || conn->io_capability == HCI_IO_NO_INPUT_OUTPUT)) {
> > --
> > 2.24.1.735.g03f4e72817-goog
>
>
> Best regard,
> Matias Karhumaa

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [Bluez PATCH v1] bluetooth: secure bluetooth stack from bluedump attack
  2020-01-06 10:14 [Bluez PATCH v1] bluetooth: secure bluetooth stack from bluedump attack howardchung
       [not found] ` <CAMCGoNzCvOgcg0hAhDO-wcFLgX75JL-G6q1KuGFEjrEz+oPTxA@mail.gmail.com>
@ 2020-01-08 21:02 ` Marcel Holtmann
  2020-01-22 17:52   ` Alain Michaud
  1 sibling, 1 reply; 6+ messages in thread
From: Marcel Holtmann @ 2020-01-08 21:02 UTC (permalink / raw)
  To: howardchung
  Cc: BlueZ devel list, chromeos-bluetooth-upstreaming,
	David S. Miller, Johan Hedberg, netdev, linux-kernel

Hi Howard,

> Attack scenario:
> 1. A Chromebook (let's call this device A) is paired to a legitimate
>   Bluetooth classic device (e.g. a speaker) (let's call this device
>   B).
> 2. A malicious device (let's call this device C) pretends to be the
>   Bluetooth speaker by using the same BT address.
> 3. If device A is not currently connected to device B, device A will
>   be ready to accept connection from device B in the background
>   (technically, doing Page Scan).
> 4. Therefore, device C can initiate connection to device A
>   (because device A is doing Page Scan) and device A will accept the
>   connection because device A trusts device C's address which is the
>   same as device B's address.
> 5. Device C won't be able to communicate at any high level Bluetooth
>   profile with device A because device A enforces that device C is
>   encrypted with their common Link Key, which device C doesn't have.
>   But device C can initiate pairing with device A with just-works
>   model without requiring user interaction (there is only pairing
>   notification). After pairing, device A now trusts device C with a
>   new different link key, common between device A and C.
> 6. From now on, device A trusts device C, so device C can at anytime
>   connect to device A to do any kind of high-level hijacking, e.g.
>   speaker hijack or mouse/keyboard hijack.
> 
> To fix this, reject the pairing if all the conditions below are met.
> - the pairing is initialized by peer
> - the authorization method is just-work
> - host already had the link key to the peer
> 
> Also create a debugfs option to permit the pairing even the
> conditions above are met.
> 
> Signed-off-by: howardchung <howardchung@google.com>

we prefer full name signed-off-by signatures.

> ---
> 
> include/net/bluetooth/hci.h |  1 +
> net/bluetooth/hci_core.c    | 47 +++++++++++++++++++++++++++++++++++++
> net/bluetooth/hci_event.c   | 12 ++++++++++
> 3 files changed, 60 insertions(+)
> 
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index 07b6ecedc6ce..4918b79baa41 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -283,6 +283,7 @@ enum {
> 	HCI_FORCE_STATIC_ADDR,
> 	HCI_LL_RPA_RESOLUTION,
> 	HCI_CMD_PENDING,
> +	HCI_PERMIT_JUST_WORK_REPAIR,
> 
> 	__HCI_NUM_FLAGS,
> };
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 9e19d5a3aac8..9014aa567e7b 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -172,10 +172,57 @@ static const struct file_operations vendor_diag_fops = {
> 	.llseek		= default_llseek,
> };
> 
> +static ssize_t permit_just_work_repair_read(struct file *file,
> +					    char __user *user_buf,
> +					    size_t count, loff_t *ppos)
> +{
> +	struct hci_dev *hdev = file->private_data;
> +	char buf[3];
> +
> +	buf[0] = hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) ? 'Y'
> +								      : 'N';
> +	buf[1] = '\n';
> +	buf[2] = '\0';
> +	return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
> +}
> +
> +static ssize_t permit_just_work_repair_write(struct file *file,
> +					     const char __user *user_buf,
> +					     size_t count, loff_t *ppos)
> +{
> +	struct hci_dev *hdev = file->private_data;
> +	char buf[32];
> +	size_t buf_size = min(count, (sizeof(buf) - 1));
> +	bool enable;
> +
> +	if (copy_from_user(buf, user_buf, buf_size))
> +		return -EFAULT;
> +
> +	buf[buf_size] = '\0';
> +	if (strtobool(buf, &enable))
> +		return -EINVAL;
> +
> +	if (enable)
> +		hci_dev_set_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
> +	else
> +		hci_dev_clear_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
> +
> +	return count;
> +}
> +
> +static const struct file_operations permit_just_work_repair_fops = {
> +	.open		= simple_open,
> +	.read		= permit_just_work_repair_read,
> +	.write		= permit_just_work_repair_write,
> +	.llseek		= default_llseek,
> +};
> +
> static void hci_debugfs_create_basic(struct hci_dev *hdev)
> {
> 	debugfs_create_file("dut_mode", 0644, hdev->debugfs, hdev,
> 			    &dut_mode_fops);
> +	debugfs_create_file("permit_just_work_repair", 0644, hdev->debugfs,
> +			    hdev, &permit_just_work_repair_fops);
> 
> 	if (hdev->set_diag)
> 		debugfs_create_file("vendor_diag", 0644, hdev->debugfs, hdev,
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 6ddc4a74a5e4..898e347e19e0 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -4539,6 +4539,18 @@ static void hci_user_confirm_request_evt(struct hci_dev *hdev,
> 		goto unlock;
> 	}
> 
> +	/* If there already exists link key in local host, terminate the
> +	 * connection by default since the remote device could be malicious.
> +	 * Permit the connection if permit_just_work_repair is enabled.
> +	 */
> +	if (!hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) &&
> +	    hci_find_link_key(hdev, &ev->bdaddr)) {
> +		BT_DBG("Rejecting request: local host already have link key");

Can we use bt_dev_warn() here.

> +		hci_send_cmd(hdev, HCI_OP_USER_CONFIRM_NEG_REPLY,
> +			     sizeof(ev->bdaddr), &ev->bdaddr);
> +		goto unlock;
> +	}
> +
> 	/* If no side requires MITM protection; auto-accept */
> 	if ((!loc_mitm || conn->remote_cap == HCI_IO_NO_INPUT_OUTPUT) &&
> 	    (!rem_mitm || conn->io_capability == HCI_IO_NO_INPUT_OUTPUT)) {

What about the LE cases?

In addition, I like to get a pair of second eyes from Johan and Luiz on this one.

Regards

Marcel


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [Bluez PATCH v1] bluetooth: secure bluetooth stack from bluedump attack
  2020-01-08 21:02 ` Marcel Holtmann
@ 2020-01-22 17:52   ` Alain Michaud
  2020-01-23 17:46     ` Marcel Holtmann
  0 siblings, 1 reply; 6+ messages in thread
From: Alain Michaud @ 2020-01-22 17:52 UTC (permalink / raw)
  To: Marcel Holtmann, Luiz Augusto von Dentz, Johan Hedberg
  Cc: Yun-hao Chung, BlueZ devel list, chromeos-bluetooth-upstreaming,
	David S. Miller, netdev, LKML

Hi Johan, Luiz,

Did you have additional feedback on this before we can send a new
version to address Marcel's comments?

Marcel, you are right, LE likely will need a similar fix.  Given we
currently have SC disabled on chromium, we can probably submit this as
a separate patch unless someone else would like to contribute it
sooner.

Thanks,
Alain

On Wed, Jan 8, 2020 at 4:02 PM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Howard,
>
> > Attack scenario:
> > 1. A Chromebook (let's call this device A) is paired to a legitimate
> >   Bluetooth classic device (e.g. a speaker) (let's call this device
> >   B).
> > 2. A malicious device (let's call this device C) pretends to be the
> >   Bluetooth speaker by using the same BT address.
> > 3. If device A is not currently connected to device B, device A will
> >   be ready to accept connection from device B in the background
> >   (technically, doing Page Scan).
> > 4. Therefore, device C can initiate connection to device A
> >   (because device A is doing Page Scan) and device A will accept the
> >   connection because device A trusts device C's address which is the
> >   same as device B's address.
> > 5. Device C won't be able to communicate at any high level Bluetooth
> >   profile with device A because device A enforces that device C is
> >   encrypted with their common Link Key, which device C doesn't have.
> >   But device C can initiate pairing with device A with just-works
> >   model without requiring user interaction (there is only pairing
> >   notification). After pairing, device A now trusts device C with a
> >   new different link key, common between device A and C.
> > 6. From now on, device A trusts device C, so device C can at anytime
> >   connect to device A to do any kind of high-level hijacking, e.g.
> >   speaker hijack or mouse/keyboard hijack.
> >
> > To fix this, reject the pairing if all the conditions below are met.
> > - the pairing is initialized by peer
> > - the authorization method is just-work
> > - host already had the link key to the peer
> >
> > Also create a debugfs option to permit the pairing even the
> > conditions above are met.
> >
> > Signed-off-by: howardchung <howardchung@google.com>
>
> we prefer full name signed-off-by signatures.
>
> > ---
> >
> > include/net/bluetooth/hci.h |  1 +
> > net/bluetooth/hci_core.c    | 47 +++++++++++++++++++++++++++++++++++++
> > net/bluetooth/hci_event.c   | 12 ++++++++++
> > 3 files changed, 60 insertions(+)
> >
> > diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> > index 07b6ecedc6ce..4918b79baa41 100644
> > --- a/include/net/bluetooth/hci.h
> > +++ b/include/net/bluetooth/hci.h
> > @@ -283,6 +283,7 @@ enum {
> >       HCI_FORCE_STATIC_ADDR,
> >       HCI_LL_RPA_RESOLUTION,
> >       HCI_CMD_PENDING,
> > +     HCI_PERMIT_JUST_WORK_REPAIR,
> >
> >       __HCI_NUM_FLAGS,
> > };
> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > index 9e19d5a3aac8..9014aa567e7b 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -172,10 +172,57 @@ static const struct file_operations vendor_diag_fops = {
> >       .llseek         = default_llseek,
> > };
> >
> > +static ssize_t permit_just_work_repair_read(struct file *file,
> > +                                         char __user *user_buf,
> > +                                         size_t count, loff_t *ppos)
> > +{
> > +     struct hci_dev *hdev = file->private_data;
> > +     char buf[3];
> > +
> > +     buf[0] = hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) ? 'Y'
> > +                                                                   : 'N';
> > +     buf[1] = '\n';
> > +     buf[2] = '\0';
> > +     return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
> > +}
> > +
> > +static ssize_t permit_just_work_repair_write(struct file *file,
> > +                                          const char __user *user_buf,
> > +                                          size_t count, loff_t *ppos)
> > +{
> > +     struct hci_dev *hdev = file->private_data;
> > +     char buf[32];
> > +     size_t buf_size = min(count, (sizeof(buf) - 1));
> > +     bool enable;
> > +
> > +     if (copy_from_user(buf, user_buf, buf_size))
> > +             return -EFAULT;
> > +
> > +     buf[buf_size] = '\0';
> > +     if (strtobool(buf, &enable))
> > +             return -EINVAL;
> > +
> > +     if (enable)
> > +             hci_dev_set_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
> > +     else
> > +             hci_dev_clear_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR);
> > +
> > +     return count;
> > +}
> > +
> > +static const struct file_operations permit_just_work_repair_fops = {
> > +     .open           = simple_open,
> > +     .read           = permit_just_work_repair_read,
> > +     .write          = permit_just_work_repair_write,
> > +     .llseek         = default_llseek,
> > +};
> > +
> > static void hci_debugfs_create_basic(struct hci_dev *hdev)
> > {
> >       debugfs_create_file("dut_mode", 0644, hdev->debugfs, hdev,
> >                           &dut_mode_fops);
> > +     debugfs_create_file("permit_just_work_repair", 0644, hdev->debugfs,
> > +                         hdev, &permit_just_work_repair_fops);
> >
> >       if (hdev->set_diag)
> >               debugfs_create_file("vendor_diag", 0644, hdev->debugfs, hdev,
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index 6ddc4a74a5e4..898e347e19e0 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -4539,6 +4539,18 @@ static void hci_user_confirm_request_evt(struct hci_dev *hdev,
> >               goto unlock;
> >       }
> >
> > +     /* If there already exists link key in local host, terminate the
> > +      * connection by default since the remote device could be malicious.
> > +      * Permit the connection if permit_just_work_repair is enabled.
> > +      */
> > +     if (!hci_dev_test_flag(hdev, HCI_PERMIT_JUST_WORK_REPAIR) &&
> > +         hci_find_link_key(hdev, &ev->bdaddr)) {
> > +             BT_DBG("Rejecting request: local host already have link key");
>
> Can we use bt_dev_warn() here.
>
> > +             hci_send_cmd(hdev, HCI_OP_USER_CONFIRM_NEG_REPLY,
> > +                          sizeof(ev->bdaddr), &ev->bdaddr);
> > +             goto unlock;
> > +     }
> > +
> >       /* If no side requires MITM protection; auto-accept */
> >       if ((!loc_mitm || conn->remote_cap == HCI_IO_NO_INPUT_OUTPUT) &&
> >           (!rem_mitm || conn->io_capability == HCI_IO_NO_INPUT_OUTPUT)) {
>
> What about the LE cases?
>
> In addition, I like to get a pair of second eyes from Johan and Luiz on this one.
>
> Regards
>
> Marcel
>
> --
> You received this message because you are subscribed to the Google Groups "ChromeOS Bluetooth Upstreaming" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to chromeos-bluetooth-upstreaming+unsubscribe@chromium.org.
> To post to this group, send email to chromeos-bluetooth-upstreaming@chromium.org.
> To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/chromeos-bluetooth-upstreaming/CD07E771-6F40-4158-A0F9-03FC128CDCD3%40holtmann.org.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [Bluez PATCH v1] bluetooth: secure bluetooth stack from bluedump attack
  2020-01-22 17:52   ` Alain Michaud
@ 2020-01-23 17:46     ` Marcel Holtmann
  0 siblings, 0 replies; 6+ messages in thread
From: Marcel Holtmann @ 2020-01-23 17:46 UTC (permalink / raw)
  To: Alain Michaud
  Cc: Luiz Augusto von Dentz, Johan Hedberg, Yun-hao Chung,
	BlueZ devel list, chromeos-bluetooth-upstreaming,
	David S. Miller, netdev, LKML

Hi Alain,

> Did you have additional feedback on this before we can send a new
> version to address Marcel's comments?
> 
> Marcel, you are right, LE likely will need a similar fix.  Given we
> currently have SC disabled on chromium, we can probably submit this as
> a separate patch unless someone else would like to contribute it
> sooner.

I would prefer if we get BR/EDR and LE fixed in the same kernel release.

Regards

Marcel


^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, back to index

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-01-06 10:14 [Bluez PATCH v1] bluetooth: secure bluetooth stack from bluedump attack howardchung
     [not found] ` <CAMCGoNzCvOgcg0hAhDO-wcFLgX75JL-G6q1KuGFEjrEz+oPTxA@mail.gmail.com>
2020-01-06 11:44   ` Fwd: " Matias Karhumaa
2020-01-07  3:30     ` Yun-hao Chung
2020-01-08 21:02 ` Marcel Holtmann
2020-01-22 17:52   ` Alain Michaud
2020-01-23 17:46     ` Marcel Holtmann

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