From 1c5a8aae2462e8ab71402b6fa7de9010bc3628bd Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Fri, 9 Aug 2013 18:36:30 -0400 Subject: [PATCH] Add option to automatically set securelevel when in Secure Boot mode UEFI Secure Boot provides a mechanism for ensuring that the firmware will only load signed bootloaders and kernels. Certain use cases may also require that the kernel prevent userspace from inserting untrusted kernel code at runtime. Add a configuration option that enforces this automatically when enabled. Signed-off-by: Matthew Garrett Gbp-Pq: Topic features/all/securelevel Gbp-Pq: Name add-option-to-automatically-set-securelevel-when-in-.patch --- Documentation/x86/zero-page.txt | 2 ++ arch/x86/Kconfig | 13 ++++++++++ arch/x86/boot/compressed/eboot.c | 36 +++++++++++++++++++++++++++ arch/x86/include/uapi/asm/bootparam.h | 3 ++- arch/x86/kernel/setup.c | 7 ++++++ 5 files changed, 60 insertions(+), 1 deletion(-) 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/Kconfig b/arch/x86/Kconfig index 447542388dd0..6545bc987c43 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1800,6 +1800,19 @@ config EFI_MIXED If unsure, say N. +config EFI_SECURE_BOOT_SECURELEVEL + def_bool n + depends on SECURITY_SECURELEVEL + depends on EFI + prompt "Automatically set securelevel when UEFI Secure Boot is enabled" + ---help--- + UEFI Secure Boot provides a mechanism for ensuring that the + firmware will only load signed bootloaders and kernels. Certain + use cases may also require that the kernel restrict any userspace + mechanism that could insert untrusted code into the kernel. + Say Y here to automatically enable securelevel enforcement + when a system boots with UEFI Secure Boot enabled. + config SECCOMP def_bool y prompt "Enable seccomp to safely compute untrusted bytecode" diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c index cc69e37548db..4a7d64ef7268 100644 --- a/arch/x86/boot/compressed/eboot.c +++ b/arch/x86/boot/compressed/eboot.c @@ -12,6 +12,7 @@ #include #include #include +#include #include "../string.h" #include "eboot.h" @@ -710,6 +711,37 @@ void setup_graphics(struct boot_params *boot_params) } } +static int get_secure_boot(void) +{ + u8 sb, setup; + unsigned long datasize = sizeof(sb); + efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID; + efi_status_t status; + + status = efi_early->call((unsigned long)sys_table->runtime->get_variable, + L"SecureBoot", &var_guid, NULL, &datasize, &sb); + + if (status != EFI_SUCCESS) + return 0; + + if (sb == 0) + return 0; + + + status = efi_early->call((unsigned long)sys_table->runtime->get_variable, + L"SetupMode", &var_guid, NULL, &datasize, + &setup); + + if (status != EFI_SUCCESS) + return 0; + + if (setup == 1) + return 0; + + return 1; +} + + /* * Because the x86 boot code expects to be passed a boot_params we * need to create one ourselves (usually the bootloader would create @@ -1094,6 +1126,10 @@ struct boot_params *efi_main(struct efi_config *c, else setup_boot_services32(efi_early); + sanitize_boot_params(boot_params); + + boot_params->secure_boot = get_secure_boot(); + 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 c18ce67495fa..2b3e5427097b 100644 --- a/arch/x86/include/uapi/asm/bootparam.h +++ b/arch/x86/include/uapi/asm/bootparam.h @@ -134,7 +134,8 @@ 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/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 6b55012d02a3..ecaa01d77b21 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -50,6 +50,7 @@ #include #include #include +#include #include #include @@ -1174,6 +1175,12 @@ void __init setup_arch(char **cmdline_p) io_delay_init(); +#ifdef CONFIG_EFI_SECURE_BOOT_SECURELEVEL + if (boot_params.secure_boot) { + set_securelevel(1); + } +#endif + /* * Parse the ACPI tables for possible boot-time SMP configuration. */ -- 2.30.2