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03d18df312
As a mitigation and hardening measure enforce verification of font
files. Then only trusted font files can be load. This will reduce the
attack surface at cost of losing the ability of end-users to customize
fonts if e.g. UEFI Secure Boot is enabled. Vendors can always customize
fonts because they have ability to pack fonts into their GRUB bundles.
This goal is achieved by:
* Removing GRUB_FILE_TYPE_FONT from shim lock verifier's
skip-verification list.
* Adding GRUB_FILE_TYPE_FONT to lockdown verifier's defer-auth list,
so font files must be verified by a verifier before they can be loaded.
Suggested-by: Daniel Kiper <daniel.kiper@oracle.com>
Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2020 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include <grub/dl.h>
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#include <grub/env.h>
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#include <grub/file.h>
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#include <grub/lockdown.h>
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#include <grub/verify.h>
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static int lockdown = GRUB_LOCKDOWN_DISABLED;
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static grub_err_t
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lockdown_verifier_init (grub_file_t io __attribute__ ((unused)),
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enum grub_file_type type,
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void **context __attribute__ ((unused)),
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enum grub_verify_flags *flags)
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{
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*flags = GRUB_VERIFY_FLAGS_SKIP_VERIFICATION;
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switch (type & GRUB_FILE_TYPE_MASK)
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{
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case GRUB_FILE_TYPE_GRUB_MODULE:
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case GRUB_FILE_TYPE_LINUX_KERNEL:
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case GRUB_FILE_TYPE_MULTIBOOT_KERNEL:
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case GRUB_FILE_TYPE_XEN_HYPERVISOR:
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case GRUB_FILE_TYPE_BSD_KERNEL:
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case GRUB_FILE_TYPE_XNU_KERNEL:
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case GRUB_FILE_TYPE_PLAN9_KERNEL:
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case GRUB_FILE_TYPE_NTLDR:
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case GRUB_FILE_TYPE_TRUECRYPT:
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case GRUB_FILE_TYPE_FREEDOS:
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case GRUB_FILE_TYPE_PXECHAINLOADER:
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case GRUB_FILE_TYPE_PCCHAINLOADER:
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case GRUB_FILE_TYPE_COREBOOT_CHAINLOADER:
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case GRUB_FILE_TYPE_EFI_CHAINLOADED_IMAGE:
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case GRUB_FILE_TYPE_ACPI_TABLE:
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case GRUB_FILE_TYPE_DEVICE_TREE_IMAGE:
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case GRUB_FILE_TYPE_FONT:
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*flags = GRUB_VERIFY_FLAGS_DEFER_AUTH;
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/* Fall through. */
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default:
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return GRUB_ERR_NONE;
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}
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}
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struct grub_file_verifier lockdown_verifier =
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{
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.name = "lockdown_verifier",
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.init = lockdown_verifier_init,
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};
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void
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grub_lockdown (void)
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{
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lockdown = GRUB_LOCKDOWN_ENABLED;
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grub_verifier_register (&lockdown_verifier);
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grub_env_set ("lockdown", "y");
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grub_env_export ("lockdown");
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}
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int
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grub_is_lockdown (void)
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{
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return lockdown;
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}
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