Re: [PATCH v1 05/12] fpga: enable secure updates

Tom Rix
2020-09-05T22:04:58Z

On 9/4/20 4:52 PM, Russ Weight wrote:
> Extend the FPGA Intel Security Manager class driver to
> include an update/filename sysfs node that can be used
> to initiate a security update. The filename of a secure
> update file (BMC image, FPGA image, Root Entry Hash image,
> or Code Signing Key cancellation image) can be written to
> this sysfs entry to cause a secure update to occur.
>
> The write of the filename will return immediately, and the
> update will begin in the context of a kernel worker thread.
> This tool utilizes the request_firmware framework, which
> requires that the image file reside under /lib/firmware.
>
> Signed-off-by: Russ Weight <russell.h.weight@intel.com>
> ---
> .../ABI/testing/sysfs-class-ifpga-sec-mgr | 13 ++
> drivers/fpga/ifpga-sec-mgr.c | 155 ++++++++++++++++++
> include/linux/fpga/ifpga-sec-mgr.h | 49 ++++++
> 3 files changed, 217 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-ifpga-sec-mgr b/Documentation/ABI/testing/sysfs-class-ifpga-sec-mgr
> index 86f8992559bf..a476504b7ae9 100644
> --- a/Documentation/ABI/testing/sysfs-class-ifpga-sec-mgr
> +++ b/Documentation/ABI/testing/sysfs-class-ifpga-sec-mgr
> @@ -73,3 +73,16 @@ Contact: Russ Weight <russell.h.weight@intel.com>
> Description: Read only. Returns number of times the BMC image has been
> flashed.
> Format: "%d".
> +
> +What: /sys/class/ifpga_sec_mgr/ifpga_secX/update/filename
> +Date: Sep 2020
> +KernelVersion: 5.10
> +Contact: Russ Weight <russell.h.weight@intel.com>
> +Description: Write only. Write the filename of an Intel image
> + file to this sysfs file to initiate a secure
> + update. The file must have an appropriate header
> + which, among other things, identifies the target
> + for the update. This mechanism is used to update
> + BMC images, BMC firmware, Static Region images,
> + and Root Entry Hashes, and to cancel Code Signing
> + Keys (CSK).
> diff --git a/drivers/fpga/ifpga-sec-mgr.c b/drivers/fpga/ifpga-sec-mgr.c
> index 97bf80277ed2..73173badbe96 100644
> --- a/drivers/fpga/ifpga-sec-mgr.c
> +++ b/drivers/fpga/ifpga-sec-mgr.c
> @@ -5,8 +5,11 @@
> * Copyright (C) 2019-2020 Intel Corporation, Inc.
> */
>
> +#include <linux/delay.h>
> +#include <linux/firmware.h>
> #include <linux/fpga/ifpga-sec-mgr.h>
> #include <linux/idr.h>
> +#include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/slab.h>
> #include <linux/vmalloc.h>
> @@ -14,6 +17,8 @@
> static DEFINE_IDA(ifpga_sec_mgr_ida);
> static struct class *ifpga_sec_mgr_class;
>
> +#define WRITE_BLOCK_SIZE 0x4000
> +
> static ssize_t show_canceled_csk(struct ifpga_sec_mgr *imgr,
> sysfs_csk_hndlr_t get_csk,
> sysfs_csk_nbits_t get_csk_nbits,
> @@ -134,6 +139,91 @@ static struct attribute *sec_mgr_security_attrs[] = {
> NULL,
> };
>
> +static void ifpga_sec_dev_error(struct ifpga_sec_mgr *imgr,
> + enum ifpga_sec_err err_code)
> +{
> + imgr->err_code = err_code;
> + imgr->iops->cancel(imgr);
> +}
> +
> +static void progress_complete(struct ifpga_sec_mgr *imgr)
> +{
> + mutex_lock(&imgr->lock);
> + imgr->progress = IFPGA_SEC_PROG_IDLE;
> + complete_all(&imgr->update_done);
> + mutex_unlock(&imgr->lock);
> +}
> +
> +static void ifpga_sec_mgr_update(struct work_struct *work)
> +{
> + u32 size, blk_size, offset = 0;
> + struct ifpga_sec_mgr *imgr;
> + const struct firmware *fw;
> + enum ifpga_sec_err ret;
> +
> + imgr = container_of(work, struct ifpga_sec_mgr, work);

Why not lock here ? It seems like filename and other

state could be changed out from under the work func.

> +
> + get_device(&imgr->dev);
> + if (request_firmware(&fw, imgr->filename, &imgr->dev)) {
> + imgr->err_code = IFPGA_SEC_ERR_FILE_READ;
> + goto idle_exit;
> + }
> +
> + imgr->data = fw->data;
> + imgr->remaining_size = fw->size;
> +
> + if (!try_module_get(imgr->dev.parent->driver->owner)) {
> + imgr->err_code = IFPGA_SEC_ERR_BUSY;
> + goto release_fw_exit;
> + }
> +
> + imgr->progress = IFPGA_SEC_PROG_PREPARING;
> + ret = imgr->iops->prepare(imgr);
> + if (ret) {
> + ifpga_sec_dev_error(imgr, ret);
> + goto modput_exit;
> + }
> +
> + imgr->progress = IFPGA_SEC_PROG_WRITING;
> + size = imgr->remaining_size;
> + while (size) {
> + blk_size = min_t(u32, size, WRITE_BLOCK_SIZE);
> + size -= blk_size;
> + ret = imgr->iops->write_blk(imgr, offset, blk_size);

Check for function pointer later, good.

Could writing a short block be handled like libc's write()

by passing back the bytes written ?

> + if (ret) {
> + ifpga_sec_dev_error(imgr, ret);
> + goto done;
> + }
> +
> + imgr->remaining_size = size;
> + offset += blk_size;
> + }
> +
> + imgr->progress = IFPGA_SEC_PROG_PROGRAMMING;
> + ret = imgr->iops->poll_complete(imgr);
> + if (ret) {
> + ifpga_sec_dev_error(imgr, ret);
> + goto done;
> + }
Add a paranoid crc check the flash is what was written ?
> +
> +done:
> + if (imgr->iops->cleanup)
> + imgr->iops->cleanup(imgr);
> +
> +modput_exit:
> + module_put(imgr->dev.parent->driver->owner);
> +
> +release_fw_exit:
> + imgr->data = NULL;
clear remaining_size ?
> + release_firmware(fw);
> +
> +idle_exit:
> + kfree(imgr->filename);
> + imgr->filename = NULL;
> + put_device(&imgr->dev);
> + progress_complete(imgr);
> +}
> +
> #define check_attr(attribute, _name) \
> ((attribute) == &dev_attr_##_name.attr && imgr->iops->_name)
>
> @@ -161,6 +251,51 @@ static struct attribute_group sec_mgr_security_attr_group = {
> .is_visible = sec_mgr_visible,
> };
>
> +static ssize_t filename_store(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct ifpga_sec_mgr *imgr = to_sec_mgr(dev);
> + int ret = 0;
> +
> + if (count == 0 || count >= PATH_MAX)
> + return -EINVAL;
> +
> + mutex_lock(&imgr->lock);
> + if (imgr->driver_unload || imgr->progress != IFPGA_SEC_PROG_IDLE) {
> + ret = -EBUSY;
> + goto unlock_exit;
> + }
> +
> + imgr->filename = kstrndup(buf, PATH_MAX - 1, GFP_KERNEL);
shouldn't this be 'count - 1' ?
> + if (!imgr->filename) {
> + ret = -ENOMEM;
> + goto unlock_exit;
> + }
> +
> + if (imgr->filename[strlen(imgr->filename) - 1] == '\n')
> + imgr->filename[strlen(imgr->filename) - 1] = '\0';

If you are catching the '\n' is a more general striping of

whitespace needed ?

Could a file exists check be done before kicking off the worker?

> +
> + imgr->err_code = IFPGA_SEC_ERR_NONE;
> + imgr->progress = IFPGA_SEC_PROG_READ_FILE;
> + reinit_completion(&imgr->update_done);
> + schedule_work(&imgr->work);

Skip the if-check at the end

ret = count.

> +
> +unlock_exit:
> + mutex_unlock(&imgr->lock);
> + return ret ? : count;
> +}
> +static DEVICE_ATTR_WO(filename);
> +
> +static struct attribute *sec_mgr_update_attrs[] = {
> + &dev_attr_filename.attr,
> + NULL,
> +};
> +
> +static struct attribute_group sec_mgr_update_attr_group = {
> + .name = "update",
> + .attrs = sec_mgr_update_attrs,
> +};
> +
> static ssize_t name_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> @@ -182,6 +317,7 @@ static struct attribute_group sec_mgr_attr_group = {
> static const struct attribute_group *ifpga_sec_mgr_attr_groups[] = {
> &sec_mgr_attr_group,
> &sec_mgr_security_attr_group,
> + &sec_mgr_update_attr_group,
> NULL,
> };
>
> @@ -233,6 +369,12 @@ ifpga_sec_mgr_register(struct device *dev, const char *name,
> struct ifpga_sec_mgr *imgr;
> int id, ret;
>
> + if (!iops || !iops->cancel || !iops->prepare ||
> + !iops->write_blk || !iops->poll_complete) {
Comments in ifpga-sec-mgr.h say 'Required: ' good.
> + dev_err(dev, "Attempt to register without ifpga_sec_mgr_ops\n");
without required ifpga_sec_mgr_ops
> + return NULL;
> + }
> +
> if (!check_reh_handler(dev, iops, bmc) ||
> !check_reh_handler(dev, iops, sr) ||
> !check_reh_handler(dev, iops, pr) ||
> @@ -254,6 +396,8 @@ ifpga_sec_mgr_register(struct device *dev, const char *name,
> imgr->name = name;
> imgr->priv = priv;
> imgr->iops = iops;
> + init_completion(&imgr->update_done);
> + INIT_WORK(&imgr->work, ifpga_sec_mgr_update);
> mutex_init(&imgr->lock);
>
> id = ida_simple_get(&ifpga_sec_mgr_ida, 0, 0, GFP_KERNEL);
> @@ -299,6 +443,17 @@ void ifpga_sec_mgr_unregister(struct ifpga_sec_mgr *imgr)
> {
> dev_info(&imgr->dev, "%s %s\n", __func__, imgr->name);
>
> + mutex_lock(&imgr->lock);
> + imgr->driver_unload = true;
> + if (imgr->progress == IFPGA_SEC_PROG_IDLE) {
> + mutex_unlock(&imgr->lock);
> + goto unregister;
> + }
> +
> + mutex_unlock(&imgr->lock);
> + wait_for_completion(&imgr->update_done);
> +
> +unregister:
> device_unregister(&imgr->dev);
> }
> EXPORT_SYMBOL_GPL(ifpga_sec_mgr_unregister);
> diff --git a/include/linux/fpga/ifpga-sec-mgr.h b/include/linux/fpga/ifpga-sec-mgr.h
> index e391b0c8f448..4da2864e251c 100644
> --- a/include/linux/fpga/ifpga-sec-mgr.h
> +++ b/include/linux/fpga/ifpga-sec-mgr.h
> @@ -7,6 +7,7 @@
> #ifndef _LINUX_IFPGA_SEC_MGR_H
> #define _LINUX_IFPGA_SEC_MGR_H
>
> +#include <linux/completion.h>
> #include <linux/device.h>
> #include <linux/mutex.h>
> #include <linux/types.h>
> @@ -86,6 +87,19 @@ typedef int (*sysfs_csk_nbits_t)(struct ifpga_sec_mgr *imgr);
> typedef int (*sysfs_csk_hndlr_t)(struct ifpga_sec_mgr *imgr,
> unsigned long *csk_map, unsigned int nbits);
>
> +enum ifpga_sec_err {
> + IFPGA_SEC_ERR_NONE = 0x0,
> + IFPGA_SEC_ERR_HW_ERROR = 0x1,
> + IFPGA_SEC_ERR_TIMEOUT = 0x2,
> + IFPGA_SEC_ERR_CANCELED = 0x3,
> + IFPGA_SEC_ERR_BUSY = 0x4,
> + IFPGA_SEC_ERR_INVALID_SIZE = 0x5,
> + IFPGA_SEC_ERR_RW_ERROR = 0x6,
> + IFPGA_SEC_ERR_WEAROUT = 0x7,
> + IFPGA_SEC_ERR_FILE_READ = 0x8,
> + IFPGA_SEC_ERR_MAX = 0x9
The initializers are redundant.
> +};
> +
> /**
> * struct ifpga_sec_mgr_ops - device specific operations
> * @user_flash_count: Optional: Return sysfs string output for FPGA
> @@ -110,6 +124,17 @@ typedef int (*sysfs_csk_hndlr_t)(struct ifpga_sec_mgr *imgr,
> * @bmc_reh_size: Optional: Return byte size for BMC root entry hash
> * @sr_reh_size: Optional: Return byte size for SR root entry hash
> * @pr_reh_size: Optional: Return byte size for PR root entry hash
> + * @prepare: Required: Prepare secure update
> + * @write_blk: Required: Write a block of data
> + * @poll_complete: Required: Check for the completion of the
> + * HW authentication/programming process. This
> + * function should check for imgr->driver_unload
> + * and abort with IFPGA_SEC_ERR_CANCELED when true.
> + * @cancel: Required: Signal HW to cancel update
> + * @cleanup: Optional: Complements the prepare()
> + * function and is called at the completion
> + * of the update, whether success or failure,
> + * if the prepare function succeeded.
> */
> struct ifpga_sec_mgr_ops {
> sysfs_cnt_hndlr_t user_flash_count;
> @@ -127,6 +152,22 @@ struct ifpga_sec_mgr_ops {
> sysfs_csk_nbits_t bmc_canceled_csk_nbits;
> sysfs_csk_nbits_t sr_canceled_csk_nbits;
> sysfs_csk_nbits_t pr_canceled_csk_nbits;
> + enum ifpga_sec_err (*prepare)(struct ifpga_sec_mgr *imgr);
> + enum ifpga_sec_err (*write_blk)(struct ifpga_sec_mgr *imgr,
> + u32 offset, u32 size);
> + enum ifpga_sec_err (*poll_complete)(struct ifpga_sec_mgr *imgr);
> + void (*cleanup)(struct ifpga_sec_mgr *imgr);
> + enum ifpga_sec_err (*cancel)(struct ifpga_sec_mgr *imgr);
> +};
> +
> +/* Update progress codes */
> +enum ifpga_sec_prog {
> + IFPGA_SEC_PROG_IDLE = 0x0,
> + IFPGA_SEC_PROG_READ_FILE = 0x1,
> + IFPGA_SEC_PROG_PREPARING = 0x2,
> + IFPGA_SEC_PROG_WRITING = 0x3,
> + IFPGA_SEC_PROG_PROGRAMMING = 0x4,
> + IFPGA_SEC_PROG_MAX = 0x5

ditto

Tom

> };
>
> struct ifpga_sec_mgr {
> @@ -134,6 +175,14 @@ struct ifpga_sec_mgr {
> struct device dev;
> const struct ifpga_sec_mgr_ops *iops;
> struct mutex lock; /* protect data structure contents */
> + struct work_struct work;
> + struct completion update_done;
> + char *filename;
> + const u8 *data; /* pointer to update data */
> + u32 remaining_size; /* size remaining to transfer */
> + enum ifpga_sec_prog progress;
> + enum ifpga_sec_err err_code; /* security manager error code */
> + bool driver_unload;
> void *priv;
> };
>