[v3] sed-opal: allow using IOC_OPAL_SAVE for locking too

Commit Message

Luca Boccassi Dec. 6, 2022, 12:03 a.m. UTC

From: Luca Boccassi <[e-mail]>

Usually when closing a crypto device (eg: dm-crypt with LUKS) the
volume key is not required, as it requires root privileges anyway, and
root can deny access to a disk in many ways regardless. Requiring the
volume key to lock the device is a peculiarity of the OPAL
specification.

Given we might already have saved the key if the user requested it via
the 'IOC_OPAL_SAVE' ioctl, we can use that key to lock the device if no
key was provided here and the locking range matches, and the user sets
the appropriate flag with 'IOC_OPAL_SAVE'. This allows integrating OPAL
with tools and libraries that are used to the common behaviour and do
not ask for the volume key when closing a device.

Callers can always pass a non-zero key and it will be used regardless,
as before.

Suggested-by: Štěpán Horáček <[e-mail]>
Signed-off-by: Luca Boccassi <[e-mail]>
---
v3: split out static helper, switch from bitfield to flags field (leaving
    two bytes for future use, u16 should be enough for flags for this ioctl)

 block/sed-opal.c              | 39 +++++++++++++++++++++++++++++++++++
 include/uapi/linux/sed-opal.h |  8 ++++++-
 2 files changed, 46 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig Dec. 6, 2022, 8:30 a.m. UTC | #1

Looks good:

Reviewed-by: Christoph Hellwig <[e-mail]>

Christian Brauner Dec. 6, 2022, 9:23 a.m. UTC | #2

On Tue, Dec 06, 2022 at 12:03:46AM +0000, [e-mail] wrote:
> From: Luca Boccassi <[e-mail]>
> 
> Usually when closing a crypto device (eg: dm-crypt with LUKS) the
> volume key is not required, as it requires root privileges anyway, and
> root can deny access to a disk in many ways regardless. Requiring the
> volume key to lock the device is a peculiarity of the OPAL
> specification.
> 
> Given we might already have saved the key if the user requested it via
> the 'IOC_OPAL_SAVE' ioctl, we can use that key to lock the device if no
> key was provided here and the locking range matches, and the user sets
> the appropriate flag with 'IOC_OPAL_SAVE'. This allows integrating OPAL
> with tools and libraries that are used to the common behaviour and do
> not ask for the volume key when closing a device.
> 
> Callers can always pass a non-zero key and it will be used regardless,
> as before.
> 
> Suggested-by: Štěpán Horáček <[e-mail]>
> Signed-off-by: Luca Boccassi <[e-mail]>
> ---

Looks good to me,
Reviewed-by: Christian Brauner <[e-mail]>

Patch

diff --git a/block/sed-opal.c b/block/sed-opal.c
index 9bdb833e5817..463873f61e01 100644
--- a/block/sed-opal.c
+++ b/block/sed-opal.c
@@ -2461,6 +2461,44 @@  static int __opal_set_mbr_done(struct opal_dev *dev, struct opal_key *key)
 	return execute_steps(dev, mbrdone_step, ARRAY_SIZE(mbrdone_step));
 }
 
+static void opal_lock_check_for_saved_key(struct opal_dev *dev,
+			    struct opal_lock_unlock *lk_unlk)
+{
+	struct opal_suspend_data *iter;
+
+	if (lk_unlk->l_state != OPAL_LK ||
+			lk_unlk->session.opal_key.key_len > 0)
+		return;
+
+	/*
+	 * Usually when closing a crypto device (eg: dm-crypt with LUKS) the
+	 * volume key is not required, as it requires root privileges anyway,
+	 * and root can deny access to a disk in many ways regardless.
+	 * Requiring the volume key to lock the device is a peculiarity of the
+	 * OPAL specification. Given we might already have saved the key if
+	 * the user requested it via the 'IOC_OPAL_SAVE' ioctl, we can use
+	 * that key to lock the device if no key was provided here, the
+	 * locking range matches and the appropriate flag was passed with
+	 * 'IOC_OPAL_SAVE'.
+	 * This allows integrating OPAL with tools and libraries that are used
+	 * to the common behaviour and do not ask for the volume key when
+	 * closing a device.
+	 */
+	setup_opal_dev(dev);
+	list_for_each_entry(iter, &dev->unlk_lst, node) {
+		if ((iter->unlk.flags & OPAL_SAVE_FOR_LOCK) &&
+				iter->lr == lk_unlk->session.opal_key.lr &&
+				iter->unlk.session.opal_key.key_len > 0) {
+			lk_unlk->session.opal_key.key_len =
+				iter->unlk.session.opal_key.key_len;
+			memcpy(lk_unlk->session.opal_key.key,
+				iter->unlk.session.opal_key.key,
+				iter->unlk.session.opal_key.key_len);
+			break;
+		}
+	}
+}
+
 static int opal_lock_unlock(struct opal_dev *dev,
 			    struct opal_lock_unlock *lk_unlk)
 {
@@ -2470,6 +2508,7 @@  static int opal_lock_unlock(struct opal_dev *dev,
 		return -EINVAL;
 
 	mutex_lock(&dev->dev_lock);
+	opal_lock_check_for_saved_key(dev, lk_unlk);
 	ret = __opal_lock_unlock(dev, lk_unlk);
 	mutex_unlock(&dev->dev_lock);
 
diff --git a/include/uapi/linux/sed-opal.h b/include/uapi/linux/sed-opal.h
index 2573772e2fb3..1fed3c9294fc 100644
--- a/include/uapi/linux/sed-opal.h
+++ b/include/uapi/linux/sed-opal.h
@@ -44,6 +44,11 @@  enum opal_lock_state {
 	OPAL_LK = 0x04, /* 0100 */
 };
 
+enum opal_lock_flags {
+	/* IOC_OPAL_SAVE will also store the provided key for locking */
+	OPAL_SAVE_FOR_LOCK = 0x01,
+};
+
 struct opal_key {
 	__u8 lr;
 	__u8 key_len;
@@ -76,7 +81,8 @@  struct opal_user_lr_setup {
 struct opal_lock_unlock {
 	struct opal_session_info session;
 	__u32 l_state;
-	__u8 __align[4];
+	__u16 flags;
+	__u8 __align[2];
 };
 
 struct opal_new_pw {