| Message ID | 147990565051.7576.9673287945782426886.stgit@warthog.procyon.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 2016-11-23 at 12:54 +0000, David Howells wrote: > Get the firmware's secure-boot status in the kernel boot wrapper and > stash it somewhere that the main kernel image can find. > > The efi_get_secureboot() function is extracted from the arm stub and > (a) generalised so that it can be called from x86 and (b) made to use > efi_call_runtime() so that it can be run in mixed-mode. > > Suggested-by: Lukas Wunner <lukas@wunner.de> > Signed-off-by: David Howells <dhowells@redhat.com> Since you seem to be using this to mean "is the platform locked down?", this looks to be no longer complete in the UEFI 2.6 world. If DeployedMode == 0, even if SecureBoot == 1 and SetupMode == 0, you can remove the platform key by writing 1 to AuditMode and gain control of the secure variables. The lock down state becomes DeployedMode == 1, SecureBoot == 1 and SetupMode == 0 See the diagram on page 1817 http://www.uefi.org/sites/default/files/resources/UEFI%20Spec%202_6.pdf James -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
James Bottomley <James.Bottomley@HansenPartnership.com> wrote: > Since you seem to be using this to mean "is the platform locked down?", > this looks to be no longer complete in the UEFI 2.6 world. If > DeployedMode == 0, even if SecureBoot == 1 and SetupMode == 0, you can > remove the platform key by writing 1 to AuditMode and gain control of > the secure variables. The lock down state becomes DeployedMode == 1, > SecureBoot == 1 and SetupMode == 0 > > See the diagram on page 1817 > > http://www.uefi.org/sites/default/files/resources/UEFI%20Spec%202_6.pdf How many pages?! Does the DeployedMode variable not exist in older versions of the UEFI spec? David -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 25 November 2016 at 09:30, David Howells <dhowells@redhat.com> wrote: > James Bottomley <James.Bottomley@HansenPartnership.com> wrote: > >> Since you seem to be using this to mean "is the platform locked down?", >> this looks to be no longer complete in the UEFI 2.6 world. If >> DeployedMode == 0, even if SecureBoot == 1 and SetupMode == 0, you can >> remove the platform key by writing 1 to AuditMode and gain control of >> the secure variables. The lock down state becomes DeployedMode == 1, >> SecureBoot == 1 and SetupMode == 0 >> >> See the diagram on page 1817 >> >> http://www.uefi.org/sites/default/files/resources/UEFI%20Spec%202_6.pdf > > How many pages?! > > Does the DeployedMode variable not exist in older versions of the UEFI spec? > No, it was added in 2.6 -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/x86/zero-page.txt b/Documentation/x86/zero-page.txt index 95a4d34af3fd..b8527c6b7646 100644 --- a/Documentation/x86/zero-page.txt +++ b/Documentation/x86/zero-page.txt @@ -31,6 +31,8 @@ Offset Proto Name Meaning 1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below) 1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer (below) +1EB/001 ALL kbd_status Numlock is enabled +1EC/001 ALL secure_boot Secure boot is enabled in the firmware 1EF/001 ALL sentinel Used to detect broken bootloaders 290/040 ALL edd_mbr_sig_buffer EDD MBR signatures 2D0/A00 ALL e820_map E820 memory map table diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c index c8c32ebcdfdb..6023b0e6f2af 100644 --- a/arch/x86/boot/compressed/eboot.c +++ b/arch/x86/boot/compressed/eboot.c @@ -1158,6 +1158,8 @@ struct boot_params *efi_main(struct efi_config *c, else setup_boot_services32(efi_early); + boot_params->secure_boot = (efi_get_secureboot(sys_table) == 1); + setup_graphics(boot_params); setup_efi_pci(boot_params); diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h index b10bf319ed20..5138dacf8bb8 100644 --- a/arch/x86/include/uapi/asm/bootparam.h +++ b/arch/x86/include/uapi/asm/bootparam.h @@ -135,7 +135,8 @@ struct boot_params { __u8 eddbuf_entries; /* 0x1e9 */ __u8 edd_mbr_sig_buf_entries; /* 0x1ea */ __u8 kbd_status; /* 0x1eb */ - __u8 _pad5[3]; /* 0x1ec */ + __u8 secure_boot; /* 0x1ec */ + __u8 _pad5[2]; /* 0x1ed */ /* * The sentinel is set to a nonzero value (0xff) in header.S. * diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 6621b13c370f..9af966863612 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -28,7 +28,7 @@ OBJECT_FILES_NON_STANDARD := y # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. KCOV_INSTRUMENT := n -lib-y := efi-stub-helper.o gop.o +lib-y := efi-stub-helper.o gop.o secureboot.o # include the stub's generic dependencies from lib/ when building for ARM/arm64 arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c index b4f7d78f9e8b..552ee61ddbed 100644 --- a/drivers/firmware/efi/libstub/arm-stub.c +++ b/drivers/firmware/efi/libstub/arm-stub.c @@ -20,52 +20,6 @@ bool __nokaslr; -static int efi_get_secureboot(efi_system_table_t *sys_table_arg) -{ - 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; - u8 val; - unsigned long size = sizeof(val); - efi_status_t status; - - 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_NOT_FOUND: - return 0; - case EFI_DEVICE_ERROR: - return -EIO; - case EFI_SECURITY_VIOLATION: - return -EACCES; - default: - return -EINVAL; - } -} - efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg, void *__image, void **__fh) { diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c new file mode 100644 index 000000000000..466fe24f5866 --- /dev/null +++ b/drivers/firmware/efi/libstub/secureboot.c @@ -0,0 +1,71 @@ +/* + * Secure boot handling. + * + * Copyright (C) 2013,2014 Linaro Limited + * Roy Franz <roy.franz@linaro.org + * Copyright (C) 2013 Red Hat, Inc. + * Mark Salter <msalter@redhat.com> + * + * This file is part of the Linux kernel, and is made available under the + * terms of the GNU General Public License version 2. + * + */ + +#include <linux/efi.h> +#include <asm/efi.h> + +/* BIOS variables */ +static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID; +static const efi_char16_t const efi_SecureBoot_name[] = { + 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 +}; +static const efi_char16_t const efi_SetupMode_name[] = { + 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 +}; + +#define get_efi_var(name, vendor, ...) \ + efi_call_runtime(get_variable, \ + (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ + __VA_ARGS__); + +/* + * Determine whether we're in secure boot mode. + */ +int efi_get_secureboot(efi_system_table_t *sys_table_arg) +{ + u8 val; + unsigned long size = sizeof(val); + efi_status_t status; + + status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid, + NULL, &size, &val); + + if (status != EFI_SUCCESS) + goto out_efi_err; + + if (val == 0) + return 0; + + status = get_efi_var(efi_SetupMode_name, &efi_variable_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_NOT_FOUND: + return 0; + case EFI_DEVICE_ERROR: + return -EIO; + case EFI_SECURITY_VIOLATION: + return -EACCES; + default: + return -EINVAL; + } +} diff --git a/include/linux/efi.h b/include/linux/efi.h index c7904556d7a8..5d6c60a9caf8 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1477,6 +1477,8 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg, bool efi_runtime_disabled(void); extern void efi_call_virt_check_flags(unsigned long flags, const char *call); +int efi_get_secureboot(efi_system_table_t *sys_table_arg); + /* * Arch code can implement the following three template macros, avoiding * reptition for the void/non-void return cases of {__,}efi_call_virt():
Get the firmware's secure-boot status in the kernel boot wrapper and stash it somewhere that the main kernel image can find. The efi_get_secureboot() function is extracted from the arm stub and (a) generalised so that it can be called from x86 and (b) made to use efi_call_runtime() so that it can be run in mixed-mode. Suggested-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: David Howells <dhowells@redhat.com> --- Documentation/x86/zero-page.txt | 2 + arch/x86/boot/compressed/eboot.c | 2 + arch/x86/include/uapi/asm/bootparam.h | 3 + drivers/firmware/efi/libstub/Makefile | 2 - drivers/firmware/efi/libstub/arm-stub.c | 46 ------------------- drivers/firmware/efi/libstub/secureboot.c | 71 +++++++++++++++++++++++++++++ include/linux/efi.h | 2 + 7 files changed, 80 insertions(+), 48 deletions(-) create mode 100644 drivers/firmware/efi/libstub/secureboot.c -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html