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Don't verify kernels twice
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
This commit is contained in:
Robbie Harwood
parent
e31fc7ca96
commit
90dacf59d0
6 changed files with 302 additions and 1 deletions
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@ -0,0 +1,73 @@
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
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Date: Thu, 3 Mar 2022 13:10:56 +0100
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Subject: [PATCH] grub-core/loader/i386/efi/linux.c: do not validate kernels
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twice
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On codebases that have shim-lock-verifier built into the grub core
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(like 2.06 upstream), shim-lock-verifier is in enforcing mode when
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booted with secureboot. It means that grub_cmd_linux() command
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attempts to perform shim validate upon opening linux kernel image,
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including kernel measurement. And the verifier correctly returns file
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open error when shim validate protocol is not present or shim fails to
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validate the kernel.
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This makes the call to grub_linuxefi_secure_validate() redundant, but
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also harmful. As validating the kernel image twice, extends the PCRs
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with the same measurement twice. Which breaks existing sealing
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policies when upgrading from grub2.04+rhboot+sb+linuxefi to
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grub2.06+rhboot+sb+linuxefi builds. It is also incorrect to measure
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the kernel twice.
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This patch must not be ported to older editions of grub code bases
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that do not have verifiers framework, or it is not builtin, or
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shim-lock-verifier is an optional module.
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This patch is tested to ensure that unsigned kernels are not possible
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to boot in secureboot mode when shim rejects kernel, or shim protocol
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is missing, and that the measurements become stable once again. The
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above also ensures that CVE-2020-15705 is not reintroduced.
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Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
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---
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grub-core/loader/i386/efi/linux.c | 13 -------------
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1 file changed, 13 deletions(-)
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diff --git a/grub-core/loader/i386/efi/linux.c b/grub-core/loader/i386/efi/linux.c
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index 3cf0f9b330b..941df6400b9 100644
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--- a/grub-core/loader/i386/efi/linux.c
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+++ b/grub-core/loader/i386/efi/linux.c
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@@ -30,7 +30,6 @@
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#include <grub/cpu/efi/memory.h>
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#include <grub/tpm.h>
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#include <grub/safemath.h>
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-#include <grub/efi/sb.h>
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GRUB_MOD_LICENSE ("GPLv3+");
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@@ -278,7 +277,6 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
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grub_ssize_t start, filelen;
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void *kernel = NULL;
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int setup_header_end_offset;
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- int rc;
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grub_dl_ref (my_mod);
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@@ -308,17 +306,6 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
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goto fail;
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}
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- if (grub_efi_get_secureboot () == GRUB_EFI_SECUREBOOT_MODE_ENABLED)
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- {
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- rc = grub_linuxefi_secure_validate (kernel, filelen);
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- if (rc <= 0)
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- {
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- grub_error (GRUB_ERR_INVALID_COMMAND,
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- N_("%s has invalid signature"), argv[0]);
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- goto fail;
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- }
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- }
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-
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lh = (struct linux_i386_kernel_header *)kernel;
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grub_dprintf ("linux", "original lh is at %p\n", kernel);
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@ -0,0 +1,58 @@
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
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Date: Fri, 4 Mar 2022 11:29:31 +0100
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Subject: [PATCH] grub-core/loader/arm64/linux.c: do not validate kernel twice
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Call to grub_file_open(, GRUB_FILE_TYPE_LINUX_KERNEL) already passes
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the kernel file through shim-lock verifier when secureboot is on. Thus
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there is no need to validate the kernel image again. And when doing so
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again, duplicate PCR measurement is performed, breaking measurements
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compatibility with 2.04+linuxefi.
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This patch must not be ported to older editions of grub code bases
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that do not have verifiers framework, or it is not builtin, or
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shim-lock-verifier is an optional module.
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Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
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---
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grub-core/loader/arm64/linux.c | 13 -------------
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1 file changed, 13 deletions(-)
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diff --git a/grub-core/loader/arm64/linux.c b/grub-core/loader/arm64/linux.c
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index f18d90bd749..d2af47c2c0a 100644
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--- a/grub-core/loader/arm64/linux.c
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+++ b/grub-core/loader/arm64/linux.c
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@@ -34,7 +34,6 @@
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#include <grub/i18n.h>
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#include <grub/lib/cmdline.h>
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#include <grub/verify.h>
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-#include <grub/efi/sb.h>
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GRUB_MOD_LICENSE ("GPLv3+");
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@@ -341,7 +340,6 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
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grub_off_t filelen;
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grub_uint32_t align;
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void *kernel = NULL;
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- int rc;
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grub_dl_ref (my_mod);
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@@ -370,17 +368,6 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
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goto fail;
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}
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- if (grub_efi_get_secureboot () == GRUB_EFI_SECUREBOOT_MODE_ENABLED)
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- {
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- rc = grub_linuxefi_secure_validate (kernel, filelen);
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- if (rc <= 0)
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- {
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- grub_error (GRUB_ERR_INVALID_COMMAND,
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- N_("%s has invalid signature"), argv[0]);
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- goto fail;
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- }
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- }
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-
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if (grub_arch_efi_linux_check_image (kernel) != GRUB_ERR_NONE)
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goto fail;
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if (parse_pe_header (kernel, &kernel_size, &handover_offset, &align) != GRUB_ERR_NONE)
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@ -0,0 +1,80 @@
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
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Date: Fri, 4 Mar 2022 09:31:43 +0100
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Subject: [PATCH] grub-core/loader/efi/chainloader.c: do not validate
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chainloader twice
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On secureboot systems, with shimlock verifier, call to
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grub_file_open(, GRUB_FILE_TYPE_EFI_CHAINLOADED_IMAGE) will already
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pass the chainloader target through shim-lock protocol verify
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call. And create a TPM measurement. If verification fails,
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grub_cmd_chainloader will fail at file open time.
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This makes previous code paths for negative, and zero return codes
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from grub_linuxefi_secure_validate unreachable under secureboot. But
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also breaking measurements compatibility with 2.04+linuxefi codebases,
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as the chainloader file is passed through shim_lock->verify() twice
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(via verifier & direct call to grub_linuxefi_secure_validate)
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extending the PCRs twice.
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This reduces grub_loader options to perform
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grub_secureboot_chainloader when secureboot is on, and otherwise
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attempt grub_chainloader_boot.
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It means that booting with secureboot off, yet still with shim (which
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always verifies things successfully), will stop choosing
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grub_secureboot_chainloader, and opting for a more regular
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loadimage/startimage codepath. If we want to use the
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grub_secureboot_chainloader codepath in such scenarios we should adapt
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the code to simply check for shim_lock protocol presence /
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shim_lock->context() success?! But I am not sure if that is necessary.
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This patch must not be ported to older editions of grub code bases
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that do not have verifiers framework, or it is not builtin, or
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shim-lock-verifier is an optional module.
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Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
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---
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grub-core/loader/efi/chainloader.c | 8 ++------
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1 file changed, 2 insertions(+), 6 deletions(-)
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diff --git a/grub-core/loader/efi/chainloader.c b/grub-core/loader/efi/chainloader.c
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index 3af6b122926..644cd2e56fe 100644
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--- a/grub-core/loader/efi/chainloader.c
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+++ b/grub-core/loader/efi/chainloader.c
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@@ -906,7 +906,6 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
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grub_efi_device_path_t *dp = 0;
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char *filename;
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void *boot_image = 0;
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- int rc;
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if (argc == 0)
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return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));
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@@ -1082,9 +1081,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
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orig_dev = 0;
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}
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- rc = grub_linuxefi_secure_validate((void *)(unsigned long)address, fsize);
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- grub_dprintf ("chain", "linuxefi_secure_validate: %d\n", rc);
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- if (rc > 0)
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+ if (grub_efi_get_secureboot () == GRUB_EFI_SECUREBOOT_MODE_ENABLED)
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{
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grub_file_close (file);
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grub_device_close (dev);
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@@ -1092,7 +1089,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
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grub_secureboot_chainloader_unload, 0);
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return 0;
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}
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- else if (rc == 0)
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+ else
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{
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grub_load_and_start_image(boot_image);
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grub_file_close (file);
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@@ -1101,7 +1098,6 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
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return 0;
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}
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- // -1 fall-through to fail
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fail:
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if (orig_dev)
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@ -0,0 +1,83 @@
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
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Date: Fri, 4 Mar 2022 11:36:09 +0100
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Subject: [PATCH] grub-core/loader/efi/linux.c: drop now unused
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grub_linuxefi_secure_validate
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Drop the now unused grub_linuxefi_secure_validate() as all prior users
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of this API now rely on the shim-lock-verifier codepath instead.
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This patch must not be ported to older editions of grub code bases
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that do not have verifiers framework, or it is not builtin, or
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shim-lock-verifier is an optional module.
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Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
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---
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grub-core/loader/efi/linux.c | 40 ----------------------------------------
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include/grub/efi/linux.h | 2 --
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2 files changed, 42 deletions(-)
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diff --git a/grub-core/loader/efi/linux.c b/grub-core/loader/efi/linux.c
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index 9260731c107..9265cf4200a 100644
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--- a/grub-core/loader/efi/linux.c
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+++ b/grub-core/loader/efi/linux.c
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@@ -24,46 +24,6 @@
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#include <grub/efi/pe32.h>
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#include <grub/efi/linux.h>
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-#define SHIM_LOCK_GUID \
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- { 0x605dab50, 0xe046, 0x4300, {0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23} }
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-
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-struct grub_efi_shim_lock
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-{
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- grub_efi_status_t (*verify) (void *buffer, grub_uint32_t size);
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-};
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-typedef struct grub_efi_shim_lock grub_efi_shim_lock_t;
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-
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-// Returns 1 on success, -1 on error, 0 when not available
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-int
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-grub_linuxefi_secure_validate (void *data, grub_uint32_t size)
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-{
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- grub_efi_guid_t guid = SHIM_LOCK_GUID;
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- grub_efi_shim_lock_t *shim_lock;
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- grub_efi_status_t status;
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-
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- shim_lock = grub_efi_locate_protocol(&guid, NULL);
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- grub_dprintf ("secureboot", "shim_lock: %p\n", shim_lock);
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- if (!shim_lock)
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- {
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- grub_dprintf ("secureboot", "shim not available\n");
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- return 0;
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- }
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-
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- grub_dprintf ("secureboot", "Asking shim to verify kernel signature\n");
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- status = shim_lock->verify (data, size);
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- grub_dprintf ("secureboot", "shim_lock->verify(): %ld\n", (long int)status);
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- if (status == GRUB_EFI_SUCCESS)
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- {
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- grub_dprintf ("secureboot", "Kernel signature verification passed\n");
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- return 1;
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- }
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-
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- grub_dprintf ("secureboot", "Kernel signature verification failed (0x%lx)\n",
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- (unsigned long) status);
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-
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- return -1;
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-}
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-
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wcast-align"
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diff --git a/include/grub/efi/linux.h b/include/grub/efi/linux.h
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index 0033d9305a9..887b02fd9f3 100644
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--- a/include/grub/efi/linux.h
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+++ b/include/grub/efi/linux.h
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@@ -22,8 +22,6 @@
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#include <grub/err.h>
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#include <grub/symbol.h>
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-int
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-EXPORT_FUNC(grub_linuxefi_secure_validate) (void *data, grub_uint32_t size);
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grub_err_t
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EXPORT_FUNC(grub_efi_linux_boot) (void *kernel_address, grub_off_t offset,
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void *kernel_param);
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@ -210,3 +210,7 @@ Patch0209: 0209-Update-gnulib-version-and-drop-most-gnulib-patches.patch
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Patch0210: 0210-commands-search-Fix-bug-stopping-iteration-when-no-f.patch
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Patch0211: 0211-search-new-efidisk-only-option-on-EFI-systems.patch
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Patch0212: 0212-efi-new-connectefi-command.patch
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Patch0213: 0213-grub-core-loader-i386-efi-linux.c-do-not-validate-ke.patch
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Patch0214: 0214-grub-core-loader-arm64-linux.c-do-not-validate-kerne.patch
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Patch0215: 0215-grub-core-loader-efi-chainloader.c-do-not-validate-c.patch
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Patch0216: 0216-grub-core-loader-efi-linux.c-drop-now-unused-grub_li.patch
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@ -17,7 +17,7 @@
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Name: grub2
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Epoch: 1
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Version: 2.06
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Release: 22%{?dist}
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Release: 23%{?dist}
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Summary: Bootloader with support for Linux, Multiboot and more
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License: GPLv3+
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URL: http://www.gnu.org/software/grub/
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@ -526,6 +526,9 @@ mv ${EFI_HOME}/grub.cfg.stb ${EFI_HOME}/grub.cfg
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%endif
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%changelog
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* Fri Mar 18 2022 Robbie Harwood <rharwood@redhat.com> - 2.06-23
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- Don't verify kernels twice
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* Thu Mar 10 2022 Robbie Harwood <rharwood@redhat.com> - 2.06-22
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- Skip updating BLS on ostree installations
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- Resolves: #2059776
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