mirror of
https://git.proxmox.com/git/grub2
synced 2025-07-19 15:24:28 +00:00
578c95298b
When the GRUB starts on a secure boot platform, some commands can be
used to subvert the protections provided by the verification mechanism and
could lead to booting untrusted system.
To prevent that situation, allow GRUB to be locked down. That way the code
may check if GRUB has been locked down and further restrict the commands
that are registered or what subset of their functionality could be used.
The lockdown support adds the following components:
* The grub_lockdown() function which can be used to lockdown GRUB if,
e.g., UEFI Secure Boot is enabled.
* The grub_is_lockdown() function which can be used to check if the GRUB
was locked down.
* A verifier that flags OS kernels, the GRUB modules, Device Trees and ACPI
tables as GRUB_VERIFY_FLAGS_DEFER_AUTH to defer verification to other
verifiers. These files are only successfully verified if another registered
verifier returns success. Otherwise, the whole verification process fails.
For example, PE/COFF binaries verification can be done by the shim_lock
verifier which validates the signatures using the shim_lock protocol.
However, the verification is not deferred directly to the shim_lock verifier.
The shim_lock verifier is hooked into the verification process instead.
* A set of grub_{command,extcmd}_lockdown functions that can be used by
code registering command handlers, to only register unsafe commands if
the GRUB has not been locked down.
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
112 lines
2.8 KiB
C
112 lines
2.8 KiB
C
/* command.c - support basic command */
|
|
/*
|
|
* GRUB -- GRand Unified Bootloader
|
|
* Copyright (C) 2009 Free Software Foundation, Inc.
|
|
*
|
|
* GRUB is free software: you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation, either version 3 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* GRUB is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include <grub/lockdown.h>
|
|
#include <grub/mm.h>
|
|
#include <grub/command.h>
|
|
|
|
grub_command_t grub_command_list;
|
|
|
|
grub_command_t
|
|
grub_register_command_prio (const char *name,
|
|
grub_command_func_t func,
|
|
const char *summary,
|
|
const char *description,
|
|
int prio)
|
|
{
|
|
grub_command_t cmd;
|
|
int inactive = 0;
|
|
|
|
grub_command_t *p, q;
|
|
|
|
cmd = (grub_command_t) grub_zalloc (sizeof (*cmd));
|
|
if (! cmd)
|
|
return 0;
|
|
|
|
cmd->name = name;
|
|
cmd->func = func;
|
|
cmd->summary = (summary) ? summary : "";
|
|
cmd->description = description;
|
|
|
|
cmd->flags = 0;
|
|
cmd->prio = prio;
|
|
|
|
for (p = &grub_command_list, q = *p; q; p = &(q->next), q = q->next)
|
|
{
|
|
int r;
|
|
|
|
r = grub_strcmp (cmd->name, q->name);
|
|
if (r < 0)
|
|
break;
|
|
if (r > 0)
|
|
continue;
|
|
|
|
if (cmd->prio >= (q->prio & GRUB_COMMAND_PRIO_MASK))
|
|
{
|
|
q->prio &= ~GRUB_COMMAND_FLAG_ACTIVE;
|
|
break;
|
|
}
|
|
|
|
inactive = 1;
|
|
}
|
|
|
|
*p = cmd;
|
|
cmd->next = q;
|
|
if (q)
|
|
q->prev = &cmd->next;
|
|
cmd->prev = p;
|
|
|
|
if (! inactive)
|
|
cmd->prio |= GRUB_COMMAND_FLAG_ACTIVE;
|
|
|
|
return cmd;
|
|
}
|
|
|
|
static grub_err_t
|
|
grub_cmd_lockdown (grub_command_t cmd __attribute__ ((unused)),
|
|
int argc __attribute__ ((unused)),
|
|
char **argv __attribute__ ((unused)))
|
|
|
|
{
|
|
return grub_error (GRUB_ERR_ACCESS_DENIED,
|
|
N_("%s: the command is not allowed when lockdown is enforced"),
|
|
cmd->name);
|
|
}
|
|
|
|
grub_command_t
|
|
grub_register_command_lockdown (const char *name,
|
|
grub_command_func_t func,
|
|
const char *summary,
|
|
const char *description)
|
|
{
|
|
if (grub_is_lockdown () == GRUB_LOCKDOWN_ENABLED)
|
|
func = grub_cmd_lockdown;
|
|
|
|
return grub_register_command_prio (name, func, summary, description, 0);
|
|
}
|
|
|
|
void
|
|
grub_unregister_command (grub_command_t cmd)
|
|
{
|
|
if ((cmd->prio & GRUB_COMMAND_FLAG_ACTIVE) && (cmd->next))
|
|
cmd->next->prio |= GRUB_COMMAND_FLAG_ACTIVE;
|
|
grub_list_remove (GRUB_AS_LIST (cmd));
|
|
grub_free (cmd);
|
|
}
|