This series modifies the function that queries the status of UEFI Secure Boot
in the EFI stub to match the UEFI specification, and allow the caller to
determine if it is enabled, disabled, or in an unknown state due to an
unexpected error from GetVariable().
v2:
- Add return values for unexpected errors
- Split changes into two patches
v3:
- Add more verbosity with additional prints
Linn Crosetto (2):
arm64/efi: report unexpected errors when determining Secure Boot status
arm64/efi: check SetupMode when determining Secure Boot status
drivers/firmware/efi/libstub/arm-stub.c | 54 ++++++++++++++++++++++++++-------
1 file changed, 43 insertions(+), 11 deletions(-)
--
2.1.4
Certain code in the boot path may require the ability to determine whether
UEFI Secure Boot is definitely enabled, for example printing status to the
console. Other code may need to know when UEFI Secure Boot is definitely
disabled, for example restricting use of kernel parameters.
If an unexpected error is returned from GetVariable() when querying the
status of UEFI Secure Boot, return an error to the caller. This allows the
caller to determine the definite state, and to take appropriate action if
an expected error is returned.
Signed-off-by: Linn Crosetto <[email protected]>
---
v2:
- Maintain existing behavior to allow 'dtb=' parameter only when UEFI
Secure Boot is disabled and not in an unknown state. (Mark Rutland)
v3:
- Add prints to inform the user in the following two cases: failure to
determine Secure Boot status, ignoring "dtb=" kernel parameter (Ard
Biesheuvel)
drivers/firmware/efi/libstub/arm-stub.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 3397902..1e98fb7 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -18,7 +18,7 @@
#include "efistub.h"
-static int efi_secureboot_enabled(efi_system_table_t *sys_table_arg)
+static int efi_get_secureboot(efi_system_table_t *sys_table_arg)
{
static efi_guid_t const var_guid = EFI_GLOBAL_VARIABLE_GUID;
static efi_char16_t const var_name[] = {
@@ -37,8 +37,12 @@ static int efi_secureboot_enabled(efi_system_table_t *sys_table_arg)
return val;
case EFI_NOT_FOUND:
return 0;
+ case EFI_DEVICE_ERROR:
+ return -EIO;
+ case EFI_SECURITY_VIOLATION:
+ return -EACCES;
default:
- return 1;
+ return -EINVAL;
}
}
@@ -183,6 +187,7 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID;
unsigned long reserve_addr = 0;
unsigned long reserve_size = 0;
+ int secure_boot = 0;
/* Check if we were booted by the EFI firmware */
if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
@@ -231,12 +236,21 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
if (status != EFI_SUCCESS)
pr_efi_err(sys_table, "Failed to parse EFI cmdline options\n");
+ secure_boot = efi_get_secureboot(sys_table);
+ if (secure_boot > 0)
+ pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
+
+ if (secure_boot < 0) {
+ pr_efi_err(sys_table,
+ "could not determine UEFI Secure Boot status.\n");
+ }
+
/*
* Unauthenticated device tree data is a security hazard, so
* ignore 'dtb=' unless UEFI Secure Boot is disabled.
*/
- if (efi_secureboot_enabled(sys_table)) {
- pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
+ if (secure_boot != 0 && strstr(cmdline_ptr, "dtb=")) {
+ pr_efi(sys_table, "Ignoring DTB from command line.\n");
} else {
status = handle_cmdline_files(sys_table, image, cmdline_ptr,
"dtb=",
--
2.1.4
According to the UEFI specification (version 2.5 Errata A, page 87):
The platform firmware is operating in secure boot mode if the value of
the SetupMode variable is 0 and the SecureBoot variable is set to 1. A
platform cannot operate in secure boot mode if the SetupMode variable
is set to 1.
Check the value of the SetupMode variable when determining the state of
Secure Boot. Minor cleanup, change sizeof to match kernel style guidelines.
Signed-off-by: Linn Crosetto <[email protected]>
---
v2:
- Reformat quote from UEFI specification and note cleanup (Mark Rutland)
- Restructure code on top of changes in patch 1/2
drivers/firmware/efi/libstub/arm-stub.c | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 1e98fb7..c049d41 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -20,21 +20,39 @@
static int efi_get_secureboot(efi_system_table_t *sys_table_arg)
{
- static efi_guid_t const var_guid = EFI_GLOBAL_VARIABLE_GUID;
- static efi_char16_t const var_name[] = {
+ static efi_char16_t const sb_var_name[] = {
'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 };
+ static efi_char16_t const sm_var_name[] = {
+ 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 };
+ efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
efi_get_variable_t *f_getvar = sys_table_arg->runtime->get_variable;
- unsigned long size = sizeof(u8);
- efi_status_t status;
u8 val;
+ unsigned long size = sizeof(val);
+ efi_status_t status;
- status = f_getvar((efi_char16_t *)var_name, (efi_guid_t *)&var_guid,
+ status = f_getvar((efi_char16_t *)sb_var_name, (efi_guid_t *)&var_guid,
NULL, &size, &val);
+ if (status != EFI_SUCCESS)
+ goto out_efi_err;
+
+ if (val == 0)
+ return 0;
+
+ status = f_getvar((efi_char16_t *)sm_var_name, (efi_guid_t *)&var_guid,
+ NULL, &size, &val);
+
+ if (status != EFI_SUCCESS)
+ goto out_efi_err;
+
+ if (val == 1)
+ return 0;
+
+ return 1;
+
+out_efi_err:
switch (status) {
- case EFI_SUCCESS:
- return val;
case EFI_NOT_FOUND:
return 0;
case EFI_DEVICE_ERROR:
--
2.1.4
On 3 March 2016 at 22:45, Linn Crosetto <[email protected]> wrote:
> Certain code in the boot path may require the ability to determine whether
> UEFI Secure Boot is definitely enabled, for example printing status to the
> console. Other code may need to know when UEFI Secure Boot is definitely
> disabled, for example restricting use of kernel parameters.
>
> If an unexpected error is returned from GetVariable() when querying the
> status of UEFI Secure Boot, return an error to the caller. This allows the
> caller to determine the definite state, and to take appropriate action if
> an expected error is returned.
>
> Signed-off-by: Linn Crosetto <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
> ---
> v2:
> - Maintain existing behavior to allow 'dtb=' parameter only when UEFI
> Secure Boot is disabled and not in an unknown state. (Mark Rutland)
>
> v3:
> - Add prints to inform the user in the following two cases: failure to
> determine Secure Boot status, ignoring "dtb=" kernel parameter (Ard
> Biesheuvel)
>
> drivers/firmware/efi/libstub/arm-stub.c | 22 ++++++++++++++++++----
> 1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
> index 3397902..1e98fb7 100644
> --- a/drivers/firmware/efi/libstub/arm-stub.c
> +++ b/drivers/firmware/efi/libstub/arm-stub.c
> @@ -18,7 +18,7 @@
>
> #include "efistub.h"
>
> -static int efi_secureboot_enabled(efi_system_table_t *sys_table_arg)
> +static int efi_get_secureboot(efi_system_table_t *sys_table_arg)
> {
> static efi_guid_t const var_guid = EFI_GLOBAL_VARIABLE_GUID;
> static efi_char16_t const var_name[] = {
> @@ -37,8 +37,12 @@ static int efi_secureboot_enabled(efi_system_table_t *sys_table_arg)
> return val;
> case EFI_NOT_FOUND:
> return 0;
> + case EFI_DEVICE_ERROR:
> + return -EIO;
> + case EFI_SECURITY_VIOLATION:
> + return -EACCES;
> default:
> - return 1;
> + return -EINVAL;
> }
> }
>
> @@ -183,6 +187,7 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
> efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID;
> unsigned long reserve_addr = 0;
> unsigned long reserve_size = 0;
> + int secure_boot = 0;
>
> /* Check if we were booted by the EFI firmware */
> if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
> @@ -231,12 +236,21 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
> if (status != EFI_SUCCESS)
> pr_efi_err(sys_table, "Failed to parse EFI cmdline options\n");
>
> + secure_boot = efi_get_secureboot(sys_table);
> + if (secure_boot > 0)
> + pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
> +
> + if (secure_boot < 0) {
> + pr_efi_err(sys_table,
> + "could not determine UEFI Secure Boot status.\n");
> + }
> +
> /*
> * Unauthenticated device tree data is a security hazard, so
> * ignore 'dtb=' unless UEFI Secure Boot is disabled.
> */
> - if (efi_secureboot_enabled(sys_table)) {
> - pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
> + if (secure_boot != 0 && strstr(cmdline_ptr, "dtb=")) {
> + pr_efi(sys_table, "Ignoring DTB from command line.\n");
> } else {
> status = handle_cmdline_files(sys_table, image, cmdline_ptr,
> "dtb=",
> --
> 2.1.4
>
On 3 March 2016 at 22:45, Linn Crosetto <[email protected]> wrote:
> According to the UEFI specification (version 2.5 Errata A, page 87):
>
> The platform firmware is operating in secure boot mode if the value of
> the SetupMode variable is 0 and the SecureBoot variable is set to 1. A
> platform cannot operate in secure boot mode if the SetupMode variable
> is set to 1.
>
> Check the value of the SetupMode variable when determining the state of
> Secure Boot. Minor cleanup, change sizeof to match kernel style guidelines.
>
> Signed-off-by: Linn Crosetto <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
> ---
> v2:
> - Reformat quote from UEFI specification and note cleanup (Mark Rutland)
> - Restructure code on top of changes in patch 1/2
>
> drivers/firmware/efi/libstub/arm-stub.c | 32 +++++++++++++++++++++++++-------
> 1 file changed, 25 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
> index 1e98fb7..c049d41 100644
> --- a/drivers/firmware/efi/libstub/arm-stub.c
> +++ b/drivers/firmware/efi/libstub/arm-stub.c
> @@ -20,21 +20,39 @@
>
> static int efi_get_secureboot(efi_system_table_t *sys_table_arg)
> {
> - static efi_guid_t const var_guid = EFI_GLOBAL_VARIABLE_GUID;
> - static efi_char16_t const var_name[] = {
> + static efi_char16_t const sb_var_name[] = {
> 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 };
> + static efi_char16_t const sm_var_name[] = {
> + 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 };
>
> + efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
> efi_get_variable_t *f_getvar = sys_table_arg->runtime->get_variable;
> - unsigned long size = sizeof(u8);
> - efi_status_t status;
> u8 val;
> + unsigned long size = sizeof(val);
> + efi_status_t status;
>
> - status = f_getvar((efi_char16_t *)var_name, (efi_guid_t *)&var_guid,
> + status = f_getvar((efi_char16_t *)sb_var_name, (efi_guid_t *)&var_guid,
> NULL, &size, &val);
>
> + if (status != EFI_SUCCESS)
> + goto out_efi_err;
> +
> + if (val == 0)
> + return 0;
> +
> + status = f_getvar((efi_char16_t *)sm_var_name, (efi_guid_t *)&var_guid,
> + NULL, &size, &val);
> +
> + if (status != EFI_SUCCESS)
> + goto out_efi_err;
> +
> + if (val == 1)
> + return 0;
> +
> + return 1;
> +
> +out_efi_err:
> switch (status) {
> - case EFI_SUCCESS:
> - return val;
> case EFI_NOT_FOUND:
> return 0;
> case EFI_DEVICE_ERROR:
> --
> 2.1.4
>
On Thu, Mar 03, 2016 at 02:45:48PM -0700, Linn Crosetto wrote:
> This series modifies the function that queries the status of UEFI Secure Boot
> in the EFI stub to match the UEFI specification, and allow the caller to
> determine if it is enabled, disabled, or in an unknown state due to an
> unexpected error from GetVariable().
>
> v2:
> - Add return values for unexpected errors
> - Split changes into two patches
>
> v3:
> - Add more verbosity with additional prints
>
> Linn Crosetto (2):
> arm64/efi: report unexpected errors when determining Secure Boot status
> arm64/efi: check SetupMode when determining Secure Boot status
>
> drivers/firmware/efi/libstub/arm-stub.c | 54 ++++++++++++++++++++++++++-------
> 1 file changed, 43 insertions(+), 11 deletions(-)
For the series:
Acked-by: Mark Rutland <[email protected]>
Mark
On Thu, 03 Mar, at 02:45:48PM, Linn Crosetto wrote:
> This series modifies the function that queries the status of UEFI Secure Boot
> in the EFI stub to match the UEFI specification, and allow the caller to
> determine if it is enabled, disabled, or in an unknown state due to an
> unexpected error from GetVariable().
>
> v2:
> - Add return values for unexpected errors
> - Split changes into two patches
>
> v3:
> - Add more verbosity with additional prints
>
> Linn Crosetto (2):
> arm64/efi: report unexpected errors when determining Secure Boot status
> arm64/efi: check SetupMode when determining Secure Boot status
>
> drivers/firmware/efi/libstub/arm-stub.c | 54 ++++++++++++++++++++++++++-------
> 1 file changed, 43 insertions(+), 11 deletions(-)
>
Thanks Linn, I've picked these two patches up with Ard's and Mark's
tags.