149 lines
4.5 KiB
Diff
149 lines
4.5 KiB
Diff
From: Matthew Garrett <mjg59@srcf.ucam.org>
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Date: Fri, 9 Aug 2013 18:36:30 -0400
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Subject: [12/18] Add option to automatically set securelevel when in Secure
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Boot mode
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Origin: https://github.com/mjg59/linux/commit/e324de2d053295670f3ba8ef67289835d663aae5
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UEFI Secure Boot provides a mechanism for ensuring that the firmware will
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only load signed bootloaders and kernels. Certain use cases may also
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require that the kernel prevent userspace from inserting untrusted kernel
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code at runtime. Add a configuration option that enforces this automatically
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when enabled.
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Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
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---
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Documentation/x86/zero-page.txt | 2 ++
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arch/x86/Kconfig | 13 +++++++++++++
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arch/x86/boot/compressed/eboot.c | 36 +++++++++++++++++++++++++++++++++++
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arch/x86/include/uapi/asm/bootparam.h | 3 ++-
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arch/x86/kernel/setup.c | 7 +++++++
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5 files changed, 60 insertions(+), 1 deletion(-)
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--- a/Documentation/x86/zero-page.txt
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+++ b/Documentation/x86/zero-page.txt
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@@ -31,6 +31,8 @@ Offset Proto Name Meaning
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1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below)
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1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
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(below)
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+1EB/001 ALL kbd_status Numlock is enabled
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+1EC/001 ALL secure_boot Secure boot is enabled in the firmware
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1EF/001 ALL sentinel Used to detect broken bootloaders
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290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
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2D0/A00 ALL e820_map E820 memory map table
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--- a/arch/x86/Kconfig
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+++ b/arch/x86/Kconfig
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@@ -1754,6 +1754,19 @@ config EFI_MIXED
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If unsure, say N.
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+config EFI_SECURE_BOOT_SECURELEVEL
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+ def_bool n
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+ depends on SECURITY_SECURELEVEL
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+ depends on EFI
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+ prompt "Automatically set securelevel when UEFI Secure Boot is enabled"
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+ ---help---
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+ UEFI Secure Boot provides a mechanism for ensuring that the
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+ firmware will only load signed bootloaders and kernels. Certain
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+ use cases may also require that the kernel restrict any userspace
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+ mechanism that could insert untrusted code into the kernel.
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+ Say Y here to automatically enable securelevel enforcement
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+ when a system boots with UEFI Secure Boot enabled.
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+
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config SECCOMP
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def_bool y
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prompt "Enable seccomp to safely compute untrusted bytecode"
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--- a/arch/x86/boot/compressed/eboot.c
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+++ b/arch/x86/boot/compressed/eboot.c
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@@ -12,6 +12,7 @@
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#include <asm/efi.h>
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#include <asm/setup.h>
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#include <asm/desc.h>
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+#include <asm/bootparam_utils.h>
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#include "../string.h"
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#include "eboot.h"
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@@ -1050,6 +1051,37 @@ void setup_graphics(struct boot_params *
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}
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}
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+static int get_secure_boot(void)
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+{
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+ u8 sb, setup;
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+ unsigned long datasize = sizeof(sb);
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+ efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
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+ efi_status_t status;
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+
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+ status = efi_early->call((unsigned long)sys_table->runtime->get_variable,
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+ L"SecureBoot", &var_guid, NULL, &datasize, &sb);
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+
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+ if (status != EFI_SUCCESS)
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+ return 0;
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+
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+ if (sb == 0)
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+ return 0;
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+
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+
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+ status = efi_early->call((unsigned long)sys_table->runtime->get_variable,
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+ L"SetupMode", &var_guid, NULL, &datasize,
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+ &setup);
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+
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+ if (status != EFI_SUCCESS)
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+ return 0;
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+
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+ if (setup == 1)
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+ return 0;
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+
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+ return 1;
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+}
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+
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+
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/*
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* Because the x86 boot code expects to be passed a boot_params we
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* need to create one ourselves (usually the bootloader would create
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@@ -1432,6 +1464,10 @@ struct boot_params *efi_main(struct efi_
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else
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setup_boot_services32(efi_early);
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+ sanitize_boot_params(boot_params);
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+
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+ boot_params->secure_boot = get_secure_boot();
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+
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setup_graphics(boot_params);
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setup_efi_pci(boot_params);
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--- a/arch/x86/include/uapi/asm/bootparam.h
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+++ b/arch/x86/include/uapi/asm/bootparam.h
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@@ -134,7 +134,8 @@ struct boot_params {
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__u8 eddbuf_entries; /* 0x1e9 */
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__u8 edd_mbr_sig_buf_entries; /* 0x1ea */
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__u8 kbd_status; /* 0x1eb */
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- __u8 _pad5[3]; /* 0x1ec */
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+ __u8 secure_boot; /* 0x1ec */
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+ __u8 _pad5[2]; /* 0x1ed */
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/*
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* The sentinel is set to a nonzero value (0xff) in header.S.
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*
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--- a/arch/x86/kernel/setup.c
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+++ b/arch/x86/kernel/setup.c
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@@ -50,6 +50,7 @@
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#include <linux/init_ohci1394_dma.h>
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#include <linux/kvm_para.h>
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#include <linux/dma-contiguous.h>
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+#include <linux/security.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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@@ -1145,6 +1146,12 @@ void __init setup_arch(char **cmdline_p)
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io_delay_init();
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+#ifdef CONFIG_EFI_SECURE_BOOT_SECURELEVEL
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+ if (boot_params.secure_boot) {
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+ set_securelevel(1);
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+ }
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+#endif
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+
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/*
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* Parse the ACPI tables for possible boot-time SMP configuration.
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*/
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