Re: [PATCH V3 11/11] Add option to automatically enforce modulesignatures when in Secure Boot mode
From: joeyli
Date: Wed Sep 04 2013 - 23:12:32 EST
æ äï2013-09-03 æ 19:50 -0400ïMatthew Garrett æåï
> 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 all kernel modules also be signed. Add a configuration option
> that enforces this automatically when enabled.
>
> Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
Tested-by: Lee, Chun-Yi <jlee@xxxxxxxx>
Thanks
Joey Lee
> ---
> Documentation/x86/zero-page.txt | 2 ++
> arch/x86/Kconfig | 10 ++++++++++
> arch/x86/boot/compressed/eboot.c | 36 +++++++++++++++++++++++++++++++++++
> arch/x86/include/uapi/asm/bootparam.h | 3 ++-
> arch/x86/kernel/setup.c | 6 ++++++
> include/linux/module.h | 6 ++++++
> kernel/module.c | 7 +++++++
> 7 files changed, 69 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/x86/zero-page.txt b/Documentation/x86/zero-page.txt
> index 199f453..ec38acf 100644
> --- a/Documentation/x86/zero-page.txt
> +++ b/Documentation/x86/zero-page.txt
> @@ -30,6 +30,8 @@ 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 b32ebf9..6a6c19b 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1581,6 +1581,16 @@ config EFI_STUB
>
> See Documentation/x86/efi-stub.txt for more information.
>
> +config EFI_SECURE_BOOT_SIG_ENFORCE
> + def_bool n
> + prompt "Force module signing 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 all kernel modules also be signed.
> + Say Y here to automatically enable module signature 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 b7388a4..53bfe4f 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -12,6 +12,7 @@
> #include <asm/efi.h>
> #include <asm/setup.h>
> #include <asm/desc.h>
> +#include <asm/bootparam_utils.h>
>
> #undef memcpy /* Use memcpy from misc.c */
>
> @@ -861,6 +862,37 @@ fail:
> return status;
> }
>
> +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_call_phys5(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_call_phys5(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
> @@ -1169,6 +1201,10 @@ struct boot_params *efi_main(void *handle, efi_system_table_t *_table,
> if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
> goto fail;
>
> + 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 c15ddaf..85d7685 100644
> --- a/arch/x86/include/uapi/asm/bootparam.h
> +++ b/arch/x86/include/uapi/asm/bootparam.h
> @@ -131,7 +131,8 @@ 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 f8ec578..deeb7bc 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1129,6 +1129,12 @@ void __init setup_arch(char **cmdline_p)
>
> io_delay_init();
>
> +#ifdef CONFIG_EFI_SECURE_BOOT_SIG_ENFORCE
> + if (boot_params.secure_boot) {
> + enforce_signed_modules();
> + }
> +#endif
> +
> /*
> * Parse the ACPI tables for possible boot-time SMP configuration.
> */
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 0c266b2..5a6374a 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -184,6 +184,12 @@ const struct exception_table_entry *search_exception_tables(unsigned long add);
>
> struct notifier_block;
>
> +#ifdef CONFIG_MODULE_SIG
> +extern void enforce_signed_modules(void);
> +#else
> +static inline void enforce_signed_modules(void) {};
> +#endif
> +
> #ifdef CONFIG_MODULES
>
> extern int modules_disabled; /* for sysctl */
> diff --git a/kernel/module.c b/kernel/module.c
> index 0e94acf..974139b 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3853,6 +3853,13 @@ void module_layout(struct module *mod,
> EXPORT_SYMBOL(module_layout);
> #endif
>
> +#ifdef CONFIG_MODULE_SIG
> +void enforce_signed_modules(void)
> +{
> + sig_enforce = true;
> +}
> +#endif
> +
> bool secure_modules(void)
> {
> #ifdef CONFIG_MODULE_SIG
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/