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SubjectRe: [PATCH 2/2] powerpc: expose secure variables via sysfs
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On Thu, 2019-06-13 at 16:50 -0400, Nayna Jain wrote:
> As part of PowerNV secure boot support, OS verification keys are stored
> and controlled by OPAL as secure variables. These need to be exposed to
> the userspace so that sysadmins can perform key management tasks.
>
> This patch adds the support to expose secure variables via a sysfs
> interface It reuses the the existing efi defined hooks and backend in
> order to maintain the compatibility with the userspace tools.
>
> Though it reuses a great deal of efi, POWER platforms do not use EFI.
> A new config, POWER_SECVAR_SYSFS, is defined to enable this new sysfs
> interface.

I spent all day staring at the skiboot bits of this, so I figured I
should see what the kernel bits looked like too...

On the last version of this patch set (posted by Claudio) Matthew
Garret was pretty explicit about the interface here not conforming to
the expectations of efivars[1], so what's changed in this patch set to
fix that?

As far as I can tell it's has the same basic problems as before, just
with a slightly different OPAL interface.

[1] https://www.spinics.net/lists/linux-efi/msg15897.html

>
> Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> ---
> arch/powerpc/Kconfig | 2 +
> drivers/firmware/Makefile | 1 +
> drivers/firmware/efi/efivars.c | 2 +-
> drivers/firmware/powerpc/Kconfig | 12 +
> drivers/firmware/powerpc/Makefile | 3 +
> drivers/firmware/powerpc/efi_error.c | 46 ++++
> drivers/firmware/powerpc/secvar.c | 326 +++++++++++++++++++++++++++
> 7 files changed, 391 insertions(+), 1 deletion(-)
> create mode 100644 drivers/firmware/powerpc/Kconfig
> create mode 100644 drivers/firmware/powerpc/Makefile
> create mode 100644 drivers/firmware/powerpc/efi_error.c
> create mode 100644 drivers/firmware/powerpc/secvar.c
>

> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 9de77bb14f54..1548dd8cf1a0 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -916,6 +916,8 @@ config PPC_SECURE_BOOT
> allows user to enable OS Secure Boot on PowerPC systems that
> have firmware secure boot support.
>
> +source "drivers/firmware/powerpc/Kconfig"
> +
> endmenu

All of this is *very* powernv specific, so why is it here and not in
arch/powerpc/platforms/powernv/ with the rest of the powernv platform
code? Also, nothing about this is generic to powerpc as a whole so the
Kconfig symbol should probably be change the Kconfig symbol to
POWERNV_SECURE_BOOT or OPAL_SECURE_BOOT

> config ISA_DMA_API
> diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
> index 3fa0b34eb72f..8cfaf7e6769d 100644
> --- a/drivers/firmware/Makefile
> +++ b/drivers/firmware/Makefile
> @@ -33,3 +33,4 @@ obj-$(CONFIG_UEFI_CPER) += efi/
> obj-y += imx/
> obj-y += tegra/
> obj-y += xilinx/
> +obj-$(CONFIG_POWER_SECVAR_SYSFS) += powerpc/
> diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c
> index 7576450c8254..30ef53003c24 100644
> --- a/drivers/firmware/efi/efivars.c
> +++ b/drivers/firmware/efi/efivars.c
> @@ -664,7 +664,7 @@ int efivars_sysfs_init(void)
> struct kobject *parent_kobj = efivars_kobject();
> int error = 0;
>
> - if (!efi_enabled(EFI_RUNTIME_SERVICES))
> + if (IS_ENABLED(CONFIG_EFI) && !efi_enabled(EFI_RUNTIME_SERVICES))
> return -ENODEV;
>
> /* No efivars has been registered yet */

Seems a bit sketch.

> diff --git a/drivers/firmware/powerpc/Kconfig b/drivers/firmware/powerpc/Kconfig
> new file mode 100644
> index 000000000000..e0303fc517d5
> --- /dev/null
> +++ b/drivers/firmware/powerpc/Kconfig
> @@ -0,0 +1,12 @@
> +config POWER_SECVAR_SYSFS
> + tristate "Enable sysfs interface for POWER secure variables"
> + default n
> + depends on PPC_SECURE_BOOT
> + select UCS2_STRING
> + help
> + POWER secure variables are managed and controlled by OPAL.
> + These variables are exposed to userspace via sysfs to allow
> + user to read/write these variables. Say Y if you have secure
> + boot enabled and want to expose variables to userspace.
> +
> +source "drivers/firmware/efi/Kconfig"

Again, this is all powernv specific and not generic to all powerpc
platforms.

> diff --git a/drivers/firmware/powerpc/Makefile b/drivers/firmware/powerpc/Makefile
> new file mode 100644
> index 000000000000..d5fa3b007315
> --- /dev/null
> +++ b/drivers/firmware/powerpc/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +obj-$(CONFIG_POWER_SECVAR_SYSFS) += ../efi/efivars.o efi_error.o ../efi/vars.o secvar.o

Uh... That is going to need an Ack from someone in EFI land.

> diff --git a/drivers/firmware/powerpc/efi_error.c b/drivers/firmware/powerpc/efi_error.c
> new file mode 100644
> index 000000000000..b5cabd52e6b4
> --- /dev/null
> +++ b/drivers/firmware/powerpc/efi_error.c
> @@ -0,0 +1,46 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain <nayna@linux.ibm.com>
> + *
> + * efi_error.c
> + * - Error codes as understood by efi based tools
> + * Taken from drivers/firmware/efi/efi.c
> + */
> +#include<linux/efi.h>
> +
> +int efi_status_to_err(efi_status_t status)
> +{
> + int err;
> +
> + switch (status) {
> + case EFI_SUCCESS:
> + err = 0;
> + break;
> + case EFI_INVALID_PARAMETER:
> + err = -EINVAL;
> + break;
> + case EFI_OUT_OF_RESOURCES:
> + err = -ENOSPC;
> + break;
> + case EFI_DEVICE_ERROR:
> + err = -EIO;
> + break;
> + case EFI_WRITE_PROTECTED:
> + err = -EROFS;
> + break;
> + case EFI_SECURITY_VIOLATION:
> + err = -EACCES;
> + break;
> + case EFI_NOT_FOUND:
> + err = -ENOENT;
> + break;
> + case EFI_ABORTED:
> + err = -EINTR;
> + break;
> + default:
> + err = -EINVAL;
> + }
> +
> + return err;
> +}

what calls this?

> diff --git a/drivers/firmware/powerpc/secvar.c b/drivers/firmware/powerpc/secvar.c
> new file mode 100644
> index 000000000000..f1f134a0bb7c
> --- /dev/null
> +++ b/drivers/firmware/powerpc/secvar.c
> @@ -0,0 +1,326 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain <nayna@linux.ibm.com>
> + *
> + * secvar.c
> + * - wrappers to expose secure variables to userspace
> + */
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/types.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/spinlock.h>
> +#include <linux/fs.h>
> +#include <linux/slab.h>
> +#include <linux/ioctl.h>
> +#include <linux/uaccess.h>
> +#include <linux/kdebug.h>
> +#include <linux/efi.h>
> +#include <linux/module.h>
> +#include <linux/ucs2_string.h>
> +#include <asm/opal-secvar.h>
> +#include <asm/opal.h>
> +
> +static struct efivars efivars;
> +struct kobject *powerpc_kobj;
> +
> +efi_status_t opal_to_efi_status_log(int rc, const char *func_name)
> +{
> + efi_status_t status;
> +
> + switch (rc) {
> + case OPAL_EMPTY:
> + status = EFI_NOT_FOUND;
> + break;
> + case OPAL_HARDWARE:
> + status = EFI_DEVICE_ERROR;
> + break;
> + case OPAL_NO_MEM:
> + pr_err("%s: No space in the volatile storage\n", func_name);
> + status = EFI_OUT_OF_RESOURCES;
> + break;
> + case OPAL_PARAMETER:
> + status = EFI_INVALID_PARAMETER;
> + break;
> + case OPAL_PARTIAL:
> + status = EFI_BUFFER_TOO_SMALL;
> + break;
> + case OPAL_PERMISSION:
> + status = EFI_WRITE_PROTECTED;
> + break;
> + case OPAL_RESOURCE:
> + pr_err("%s: No space in the non-volatile storage\n", func_name);
> + status = EFI_OUT_OF_RESOURCES;
> + break;
> + case OPAL_SUCCESS:
> + status = EFI_SUCCESS;
> + break;
> + default:
> + pr_err("%s: Unknown OPAL error %d\n", func_name, rc);
> + status = EFI_DEVICE_ERROR;
> + break;
> + }
> +
> + return status;
> +}
> +
> +#define opal_to_efi_status(rc) opal_to_efi_status_log(rc, __func__)
> +
> +static void createkey(efi_char16_t *name, u8 **key, unsigned long *keylen)
> +{
> + *keylen = ucs2_utf8size(name) + 1;
> +
> + *key = kzalloc(*keylen, GFP_KERNEL);
> + if (!*key) {
> + *keylen = 0;
> + *key = NULL;
> + return;
> + }
> +
> + ucs2_as_utf8(*key, name, *keylen);
> +}
>
> +static void createmetadata(efi_char16_t *name, efi_guid_t *vendor, u32 *attr,
> + u8 **mdata, unsigned long *mdsize)
> +{
> + int size = 0;
> +
> + *mdsize = ucs2_strsize(name, 1024) + sizeof(efi_guid_t) + sizeof(u32);
> + *mdata = kzalloc(*mdsize, GFP_KERNEL);
> +
> + memcpy(*mdata, name, ucs2_strsize(name, 1024));
> + size = ucs2_strsize(name, 1024);
> +
> + memcpy(*mdata + size, vendor, sizeof(efi_guid_t));
> + size += sizeof(efi_guid_t);
> +
> + if (attr != NULL)
> + memcpy(*mdata + size, attr, sizeof(u32));
> + else
> + memset(*mdata + size, 0, sizeof(u32));
> +}

> +static int convert_buffer_to_efi_guid(u8 *buffer, efi_guid_t *guid)
> +{
> + u32 *a1;
> + u16 *a2;
> + u16 *a3;
> +
> + a1 = kzalloc(4, GFP_KERNEL);
> + memcpy(a1, buffer, 4);
> + *a1 = be32_to_cpu(*a1);
> +
> + a2 = kzalloc(2, GFP_KERNEL);
> + memcpy(a2, buffer+4, 2);
> + *a2 = be16_to_cpu(*a2);
> +
> + a3 = kzalloc(2, GFP_KERNEL);
> + memcpy(a3, buffer+6, 2);
> + *a3 = be16_to_cpu(*a3);
> +
> + *guid = EFI_GUID(*a1, *a2, *a3, *(buffer + 8),
> + *(buffer + 9),
> + *(buffer + 10),
> + *(buffer + 11),
> + *(buffer + 12),
> + *(buffer + 13),
> + *(buffer + 14),
> + *(buffer + 15));
> +
> + kfree(a1);
> + kfree(a2);
> + kfree(a3);

These should be on the stack, They're small and you free them almost
immediately after allocating them.

> + return 0;
> +}

> +static efi_status_t powerpc_get_variable(efi_char16_t *name, efi_guid_t *vendor,
> + u32 *attr, unsigned long *data_size,
> + void *data)
> +{
> + int rc;
> + u8 *key;
> + unsigned long keylen;
> + u8 *metadata;
> + unsigned long mdsize;
> + unsigned long dsize;
> + unsigned long namesize;
> +
> + if (!name)
> + return EFI_INVALID_PARAMETER;
> +
> + if (!vendor)
> + return EFI_INVALID_PARAMETER;
> +
> + if (*data_size == 0) {
> + /* If *data_size is zero, it implies data size is being asked */
> + createkey(name, &key, &keylen);
> + rc = opal_get_variable_size(key, keylen, &mdsize, &dsize);
> + *data_size = dsize;
> + kfree(key);
> + return opal_to_efi_status(rc);
> + }
> +
> + createkey(name, &key, &keylen);
> + createmetadata(name, vendor, attr, &metadata, &mdsize);
> +
> + rc = opal_get_variable(key, keylen, metadata, &mdsize, data, data_size);
> +
> + if (rc)
> + return opal_to_efi_status(rc);
> +
> + if (mdsize > 0) {
> + namesize = mdsize - sizeof(efi_guid_t) - sizeof(u32);
> + if (!attr)
> + return opal_to_efi_status(rc);
> + memset(attr, 0, sizeof(u32));
> + memcpy(attr, metadata + namesize + sizeof(efi_guid_t),
> + sizeof(u32));
> + *attr = be32_to_cpu(*attr);
> + }
> +
> + kfree(key);
> + kfree(metadata);
> +
> + return opal_to_efi_status(rc);
> +}
> +
> +
> +static efi_status_t powerpc_get_next_variable(unsigned long *name_size,
> + efi_char16_t *name,
> + efi_guid_t *vendor)
> +{
> + int rc;
> + u8 *key;
> + int namesize;
> + unsigned long keylen;
> + unsigned long keysize = 1024;
> + unsigned long *mdsize;
> + u8 *mdata = NULL;
> + efi_guid_t guid;
> +
> + if (ucs2_strnlen(name, 1024) > 0) {
> + createkey(name, &key, &keylen);
> + } else {
> + keylen = 0;
> + key = kzalloc(1024, GFP_KERNEL);
> + }
> +
> + pr_info("%s: powerpc get next variable, key is %s\n", __func__, key);
> +
> + rc = opal_get_next_variable(key, &keylen, keysize);

As far as I can tell the UEFI spec says the key namespace is really
made up of (vendor, key) tuples. This seems broken to me since it's
ignoring the vendor GUID part and treating it purely as an output, so
if we had two vendors (OS vendors maybe?) writing using the same key
name it'll cause problems.

You could fix that by concatenating the vendor GUID and the ucs-2 name
string, then passing that to OPAL as the key. Based on what the gsmi
driver does I don't think we really need to store the attributes either
so the metadata channel can be ditched entirely.

> + if (rc) {
> + kfree(key);
> + return opal_to_efi_status(rc);
> + }
> +
> + mdsize = kzalloc(sizeof(unsigned long), GFP_KERNEL);
> + rc = opal_get_variable_size(key, keylen, mdsize, NULL);
> + if (rc)
> + goto out;
> +
> + if (*mdsize <= 0)
> + goto out;
> +
> + mdata = kzalloc(*mdsize, GFP_KERNEL);
> +
> + rc = opal_get_variable(key, keylen, mdata, mdsize, NULL, NULL);
> + if (rc)
> + goto out;
> +
> + if (*mdsize > 0) {
> + namesize = *mdsize - sizeof(efi_guid_t) - sizeof(u32);
> + if (namesize > 0) {
> + memset(&guid, 0, sizeof(efi_guid_t));
> + convert_buffer_to_efi_guid(mdata + namesize, &guid);
> + memcpy(vendor, &guid, sizeof(efi_guid_t));
> + memset(name, 0, namesize + 2);
> + memcpy(name, mdata, namesize);
> + *name_size = namesize + 2;
> + name[namesize++] = 0;
> + name[namesize] = 0;
> + }
> + }
> +
> +out:
> + kfree(mdsize);
> + kfree(mdata);
> +
> + return opal_to_efi_status(rc);
> +}
> +
> +static efi_status_t powerpc_set_variable(efi_char16_t *name, efi_guid_t *vendor,
> + u32 attr, unsigned long data_size,
> + void *data)
> +{
> + int rc;
> + u8 *key;
> + unsigned long keylen;
> + u8 *metadata;
> + unsigned long mdsize;
> +
> + if (!name)
> + return EFI_INVALID_PARAMETER;
> +
> + if (!vendor)
> + return EFI_INVALID_PARAMETER;
> +
> + createkey(name, &key, &keylen);
> + pr_info("%s: nayna key is %s\n", __func__, key);
> +
> + createmetadata(name, vendor, &attr, &metadata, &mdsize);
> + rc = opal_set_variable(key, keylen, metadata, mdsize, data, data_size);
> +
> + return opal_to_efi_status(rc);
> +}
> +
> +
> +static const struct efivar_operations efivar_ops = {
> + .get_variable = powerpc_get_variable,
> + .set_variable = powerpc_set_variable,
> + .get_next_variable = powerpc_get_next_variable,
> +};
> +
> +
> +static __init int power_secvar_init(void)
> +{
> + int rc = 0;
> + unsigned long ver = 0;
> +
> + rc = opal_variable_version(&ver);
> + if (ver != BACKEND_TC_COMPAT_V1) {
> + pr_info("Compatible backend unsupported\n");
> + return -1;
> + }
> +
> + powerpc_kobj = kobject_create_and_add("secvar", firmware_kobj);
> + if (!powerpc_kobj) {
> + pr_info("secvar: Failed to create firmware kobj\n");
> + goto out_err;
> + }
> +
> + rc = efivars_register(&efivars, &efivar_ops, powerpc_kobj);
> + if (rc) {
> + pr_info("powerpc: Failed to register efivars\n");
> + return rc;
> + }
> +
> + return 0;
> +out_err:
> + kobject_put(powerpc_kobj);
> + pr_info("powerpc: failed to load: %d\n", rc);
> + return rc;
> +}
> +arch_initcall(power_secvar_init);
> +
> +static void __exit power_secvar_exit(void)
> +{
> + efivars_unregister(&efivars);
> + kobject_put(powerpc_kobj);
> +}
> +module_exit(power_secvar_exit);
> +
> +MODULE_AUTHOR("Nayna Jain");
> +MODULE_LICENSE("GPL");

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