On Sat, 22 Jul 2023 at 03:41, Shyam Saini shyamsaini@linux.microsoft.com wrote:
From: Alex Bennée alex.bennee@linaro.org
[This is patch 1 from [1] Alex's submission and this RPMB layer was originally proposed by [2]Thomas Winkler ]
A number of storage technologies support a specialised hardware partition designed to be resistant to replay attacks. The underlying HW protocols differ but the operations are common. The RPMB partition cannot be accessed via standard block layer, but by a set of specific commands: WRITE, READ, GET_WRITE_COUNTER, and PROGRAM_KEY. Such a partition provides authenticated and replay protected access, hence suitable as a secure storage.
The initial aim of this patch is to provide a simple RPMB Driver which can be accessed by Linux's optee driver to facilitate fast-path for RPMB access to optee OS(secure OS) during the boot time. [1] Currently, Optee OS relies on user-tee supplicant to access eMMC RPMB partition.
A TEE device driver can claim the RPMB interface, for example, via class_interface_register(). The RPMB driver provides a series of operations for interacting with the device.
I don't quite follow this. More exactly, how will the TEE driver know what RPMB device it should use?
- program_key - a one time operation for setting up a new device
- get_capacity - introspect the device capacity
- get_write_counter - check the write counter
- write_blocks - write a series of blocks to the RPMB device
- read_blocks - read a series of blocks from the RPMB device
The detailed operation of implementing the access is left to the TEE device driver itself.
The framing details and HW specific bits (JDEC vs NVME frames) are left to the lower level TEE driver to worry about.
Without kernel fast path to RPMB access doesn't work when IMA try to extend ftpm's PCR registers.
This fast-path would require additional work in linux optee driver and as well as in MMC driver.
[1] https://lore.kernel.org/lkml/20220405093759.1126835-2-alex.bennee@linaro.org... [2] https://lore.kernel.org/linux-mmc/1478548394-8184-2-git-send-email-tomas.win... [3] https://optee.readthedocs.io/en/latest/architecture/secure_storage.html
Signed-off-by: Alex Bennée alex.bennee@linaro.org Signed-off-by: Tomas Winkler tomas.winkler@intel.com Signed-off-by: Shyam Saini shyamsaini@linux.microsoft.com
[...]
+/**
- rpmb_dev_find_device() - return first matching rpmb device
- @data: data for the match function
- @match: the matching function
- Return: matching rpmb device or NULL on failure
- */
+static +struct rpmb_dev *rpmb_dev_find_device(const void *data,
int (*match)(struct device *dev,const void *data))+{
struct device *dev;dev = class_find_device(&rpmb_class, NULL, data, match);return dev ? to_rpmb_dev(dev) : NULL;+}
+struct device_with_target {
const struct device *dev;u8 target;+};
+static int match_by_parent(struct device *dev, const void *data) +{
const struct device_with_target *d = data;struct rpmb_dev *rdev = to_rpmb_dev(dev);return (d->dev && dev->parent == d->dev && rdev->target == d->target);+}
+/**
- rpmb_dev_find_by_device() - retrieve rpmb device from the parent device
- @parent: parent device of the rpmb device
- @target: RPMB target/region within the physical device
- Return: NULL if there is no rpmb device associated with the parent device
- */
+struct rpmb_dev *rpmb_dev_find_by_device(struct device *parent, u8 target) +{
struct device_with_target t;if (!parent)return NULL;t.dev = parent;t.target = target;return rpmb_dev_find_device(&t, match_by_parent);+} +EXPORT_SYMBOL_GPL(rpmb_dev_find_by_device);
Is this what the TEE driver would be calling to find the rpmb device/partition?
+/**
- rpmb_dev_unregister() - unregister RPMB partition from the RPMB subsystem
- @rdev: the rpmb device to unregister
- Return:
0 on success
-EINVAL on wrong parameters- */
+int rpmb_dev_unregister(struct rpmb_dev *rdev) +{
if (!rdev)return -EINVAL;mutex_lock(&rdev->lock);rpmb_cdev_del(rdev);
I can't find the function above. I guess it should be included as a part of the patch too?
device_del(&rdev->dev);mutex_unlock(&rdev->lock);rpmb_dev_put(rdev);return 0;+} +EXPORT_SYMBOL_GPL(rpmb_dev_unregister);
[...]
+/**
- rpmb_dev_register - register RPMB partition with the RPMB subsystem
- @dev: storage device of the rpmb device
- @target: RPMB target/region within the physical device
- @ops: device specific operations
- Return: a pointer to rpmb device
- */
+struct rpmb_dev *rpmb_dev_register(struct device *dev, u8 target,
const struct rpmb_ops *ops)+{
struct rpmb_dev *rdev;int id;int ret;if (!dev || !ops)return ERR_PTR(-EINVAL);if (!ops->program_key)return ERR_PTR(-EINVAL);if (!ops->get_capacity)return ERR_PTR(-EINVAL);if (!ops->get_write_counter)return ERR_PTR(-EINVAL);if (!ops->write_blocks)return ERR_PTR(-EINVAL);if (!ops->read_blocks)return ERR_PTR(-EINVAL);rdev = kzalloc(sizeof(*rdev), GFP_KERNEL);if (!rdev)return ERR_PTR(-ENOMEM);id = ida_simple_get(&rpmb_ida, 0, 0, GFP_KERNEL);if (id < 0) {ret = id;goto exit;}mutex_init(&rdev->lock);rdev->ops = ops;rdev->id = id;rdev->target = target;dev_set_name(&rdev->dev, "rpmb%d", id);rdev->dev.class = &rpmb_class;rdev->dev.parent = dev;rpmb_cdev_prepare(rdev);
Ditto.
ret = device_register(&rdev->dev);if (ret)goto exit;rpmb_cdev_add(rdev);
Ditto.
dev_dbg(&rdev->dev, "registered device\n");return rdev;+exit:
if (id >= 0)ida_simple_remove(&rpmb_ida, id);kfree(rdev);return ERR_PTR(ret);+} +EXPORT_SYMBOL_GPL(rpmb_dev_register);
[...]
Kind regards Uffe