310 lines
12 KiB
Diff
310 lines
12 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
|
|
From: Rashmica Gupta <rashmica.g@gmail.com>
|
|
Date: Thu, 11 Jun 2020 11:26:23 +1000
|
|
Subject: [PATCH] Add suport for signing grub with an appended signature
|
|
|
|
Add infrastructure to allow firmware to verify the integrity of grub
|
|
by use of a Linux-kernel-module-style appended signature. We initially
|
|
target powerpc-ieee1275, but the code should be extensible to other
|
|
platforms.
|
|
|
|
Usually these signatures are appended to a file without modifying the
|
|
ELF file itself. (This is what the 'sign-file' tool does, for example.)
|
|
The verifier loads the signed file from the file system and looks at the
|
|
end of the file for the appended signature. However, on powerpc-ieee1275
|
|
platforms, the bootloader is often stored directly in the PReP partition
|
|
as raw bytes without a file-system. This makes determining the location
|
|
of an appended signature more difficult.
|
|
|
|
To address this, we add a new ELF note.
|
|
|
|
The name field of shall be the string "Appended-Signature", zero-padded
|
|
to 4 byte alignment. The type field shall be 0x41536967 (the ASCII values
|
|
for the string "ASig"). It must be the final section in the ELF binary.
|
|
|
|
The description shall contain the appended signature structure as defined
|
|
by the Linux kernel. The description will also be padded to be a multiple
|
|
of 4 bytes. The padding shall be added before the appended signature
|
|
structure (not at the end) so that the final bytes of a signed ELF file
|
|
are the appended signature magic.
|
|
|
|
A subsequent patch documents how to create a grub core.img validly signed
|
|
under this scheme.
|
|
|
|
Signed-off-by: Daniel Axtens <dja@axtens.net>
|
|
Signed-off-by: Rashmica Gupta <rashmica.g@gmail.com>
|
|
---
|
|
util/grub-install-common.c | 18 ++++++++++++++----
|
|
util/grub-mkimage.c | 15 +++++++++++++--
|
|
util/grub-mkimagexx.c | 39 ++++++++++++++++++++++++++++++++++++++-
|
|
util/mkimage.c | 13 +++++++------
|
|
include/grub/util/install.h | 8 ++++++--
|
|
include/grub/util/mkimage.h | 4 ++--
|
|
6 files changed, 80 insertions(+), 17 deletions(-)
|
|
|
|
diff --git a/util/grub-install-common.c b/util/grub-install-common.c
|
|
index 4e212e690c..a74fee16e2 100644
|
|
--- a/util/grub-install-common.c
|
|
+++ b/util/grub-install-common.c
|
|
@@ -461,10 +461,12 @@ static size_t npubkeys;
|
|
static char *sbat;
|
|
static int disable_shim_lock;
|
|
static grub_compression_t compression;
|
|
+static size_t appsig_size;
|
|
|
|
int
|
|
grub_install_parse (int key, char *arg)
|
|
{
|
|
+ const char *end;
|
|
switch (key)
|
|
{
|
|
case 'C':
|
|
@@ -562,6 +564,12 @@ grub_install_parse (int key, char *arg)
|
|
grub_util_error (_("Unrecognized compression `%s'"), arg);
|
|
case GRUB_INSTALL_OPTIONS_GRUB_MKIMAGE:
|
|
return 1;
|
|
+ case GRUB_INSTALL_OPTIONS_APPENDED_SIGNATURE_SIZE:
|
|
+ grub_errno = 0;
|
|
+ appsig_size = grub_strtol(arg, &end, 10);
|
|
+ if (grub_errno)
|
|
+ return 0;
|
|
+ return 1;
|
|
default:
|
|
return 0;
|
|
}
|
|
@@ -661,11 +669,13 @@ grub_install_make_image_wrap_file (const char *dir, const char *prefix,
|
|
" --output '%s' "
|
|
" --dtb '%s' "
|
|
"--sbat '%s' "
|
|
- "--format '%s' --compression '%s' %s %s %s\n",
|
|
+ "--format '%s' --compression '%s' "
|
|
+ "--appended-signature-size %zu %s %s %s\n",
|
|
dir, prefix,
|
|
outname, dtb ? : "", sbat ? : "", mkimage_target,
|
|
- compnames[compression], note ? "--note" : "",
|
|
- disable_shim_lock ? "--disable-shim-lock" : "", s);
|
|
+ compnames[compression], appsig_size,
|
|
+ disable_shim_lock ? "--disable-shim-lock" : "",
|
|
+ note ? "--note" : "", s);
|
|
free (s);
|
|
|
|
tgt = grub_install_get_image_target (mkimage_target);
|
|
@@ -675,7 +685,7 @@ grub_install_make_image_wrap_file (const char *dir, const char *prefix,
|
|
grub_install_generate_image (dir, prefix, fp, outname,
|
|
modules.entries, memdisk_path,
|
|
pubkeys, npubkeys, config_path, tgt,
|
|
- note, compression, dtb, sbat,
|
|
+ note, appsig_size, compression, dtb, sbat,
|
|
disable_shim_lock);
|
|
while (dc--)
|
|
grub_install_pop_module ();
|
|
diff --git a/util/grub-mkimage.c b/util/grub-mkimage.c
|
|
index c0d5599370..8a53310548 100644
|
|
--- a/util/grub-mkimage.c
|
|
+++ b/util/grub-mkimage.c
|
|
@@ -84,6 +84,7 @@ static struct argp_option options[] = {
|
|
{"sbat", 's', N_("FILE"), 0, N_("SBAT metadata"), 0},
|
|
{"disable-shim-lock", GRUB_INSTALL_OPTIONS_DISABLE_SHIM_LOCK, 0, 0, N_("disable shim_lock verifier"), 0},
|
|
{"verbose", 'v', 0, 0, N_("print verbose messages."), 0},
|
|
+ {"appended-signature-size", 'S', N_("SIZE"), 0, N_("Add a note segment reserving SIZE bytes for an appended signature"), 0},
|
|
{ 0, 0, 0, 0, 0, 0 }
|
|
};
|
|
|
|
@@ -128,6 +129,7 @@ struct arguments
|
|
char *sbat;
|
|
int note;
|
|
int disable_shim_lock;
|
|
+ size_t appsig_size;
|
|
const struct grub_install_image_target_desc *image_target;
|
|
grub_compression_t comp;
|
|
};
|
|
@@ -138,6 +140,7 @@ argp_parser (int key, char *arg, struct argp_state *state)
|
|
/* Get the input argument from argp_parse, which we
|
|
know is a pointer to our arguments structure. */
|
|
struct arguments *arguments = state->input;
|
|
+ const char* end;
|
|
|
|
switch (key)
|
|
{
|
|
@@ -170,6 +173,13 @@ argp_parser (int key, char *arg, struct argp_state *state)
|
|
arguments->note = 1;
|
|
break;
|
|
|
|
+ case 'S':
|
|
+ grub_errno = 0;
|
|
+ arguments->appsig_size = grub_strtol(arg, &end, 10);
|
|
+ if (grub_errno)
|
|
+ return 0;
|
|
+ break;
|
|
+
|
|
case 'm':
|
|
if (arguments->memdisk)
|
|
free (arguments->memdisk);
|
|
@@ -324,8 +334,9 @@ main (int argc, char *argv[])
|
|
arguments.memdisk, arguments.pubkeys,
|
|
arguments.npubkeys, arguments.config,
|
|
arguments.image_target, arguments.note,
|
|
- arguments.comp, arguments.dtb,
|
|
- arguments.sbat, arguments.disable_shim_lock);
|
|
+ arguments.appsig_size, arguments.comp,
|
|
+ arguments.dtb, arguments.sbat,
|
|
+ arguments.disable_shim_lock);
|
|
|
|
if (grub_util_file_sync (fp) < 0)
|
|
grub_util_error (_("cannot sync `%s': %s"), arguments.output ? : "stdout",
|
|
diff --git a/util/grub-mkimagexx.c b/util/grub-mkimagexx.c
|
|
index d78fa3e533..393119486d 100644
|
|
--- a/util/grub-mkimagexx.c
|
|
+++ b/util/grub-mkimagexx.c
|
|
@@ -84,6 +84,15 @@ struct grub_ieee1275_note
|
|
struct grub_ieee1275_note_desc descriptor;
|
|
};
|
|
|
|
+#define GRUB_APPENDED_SIGNATURE_NOTE_NAME "Appended-Signature"
|
|
+#define GRUB_APPENDED_SIGNATURE_NOTE_TYPE 0x41536967 /* "ASig" */
|
|
+
|
|
+struct grub_appended_signature_note
|
|
+{
|
|
+ Elf32_Nhdr header;
|
|
+ char name[ALIGN_UP(sizeof (GRUB_APPENDED_SIGNATURE_NOTE_NAME), 4)];
|
|
+};
|
|
+
|
|
#define GRUB_XEN_NOTE_NAME "Xen"
|
|
|
|
struct fixup_block_list
|
|
@@ -207,7 +216,7 @@ grub_arm_reloc_jump24 (grub_uint32_t *target, Elf32_Addr sym_addr)
|
|
|
|
void
|
|
SUFFIX (grub_mkimage_generate_elf) (const struct grub_install_image_target_desc *image_target,
|
|
- int note, char **core_img, size_t *core_size,
|
|
+ int note, size_t appsig_size, char **core_img, size_t *core_size,
|
|
Elf_Addr target_addr,
|
|
struct grub_mkimage_layout *layout)
|
|
{
|
|
@@ -221,6 +230,12 @@ SUFFIX (grub_mkimage_generate_elf) (const struct grub_install_image_target_desc
|
|
int shnum = 4;
|
|
int string_size = sizeof (".text") + sizeof ("mods") + 1;
|
|
|
|
+ if (appsig_size)
|
|
+ {
|
|
+ phnum++;
|
|
+ footer_size += ALIGN_UP(sizeof (struct grub_appended_signature_note) + appsig_size, 4);
|
|
+ }
|
|
+
|
|
if (image_target->id != IMAGE_LOONGSON_ELF)
|
|
phnum += 2;
|
|
|
|
@@ -484,6 +499,28 @@ SUFFIX (grub_mkimage_generate_elf) (const struct grub_install_image_target_desc
|
|
phdr->p_offset = grub_host_to_target32 (header_size + program_size);
|
|
}
|
|
|
|
+ if (appsig_size) {
|
|
+ int note_size = ALIGN_UP(sizeof (struct grub_appended_signature_note) + appsig_size, 4);
|
|
+ struct grub_appended_signature_note *note_ptr = (struct grub_appended_signature_note *)
|
|
+ (elf_img + program_size + header_size + (note ? sizeof (struct grub_ieee1275_note) : 0));
|
|
+
|
|
+ note_ptr->header.n_namesz = grub_host_to_target32 (sizeof (GRUB_APPENDED_SIGNATURE_NOTE_NAME));
|
|
+ /* needs to sit at the end, so we round this up and sign some zero padding */
|
|
+ note_ptr->header.n_descsz = grub_host_to_target32 (ALIGN_UP(appsig_size, 4));
|
|
+ note_ptr->header.n_type = grub_host_to_target32 (GRUB_APPENDED_SIGNATURE_NOTE_TYPE);
|
|
+ strcpy (note_ptr->name, GRUB_APPENDED_SIGNATURE_NOTE_NAME);
|
|
+
|
|
+ phdr++;
|
|
+ phdr->p_type = grub_host_to_target32 (PT_NOTE);
|
|
+ phdr->p_flags = grub_host_to_target32 (PF_R);
|
|
+ phdr->p_align = grub_host_to_target32 (image_target->voidp_sizeof);
|
|
+ phdr->p_vaddr = 0;
|
|
+ phdr->p_paddr = 0;
|
|
+ phdr->p_filesz = grub_host_to_target32 (note_size);
|
|
+ phdr->p_memsz = 0;
|
|
+ phdr->p_offset = grub_host_to_target32 (header_size + program_size + (note ? sizeof (struct grub_ieee1275_note) : 0));
|
|
+ }
|
|
+
|
|
{
|
|
char *str_start = (elf_img + sizeof (*ehdr) + phnum * sizeof (*phdr)
|
|
+ shnum * sizeof (*shdr));
|
|
diff --git a/util/mkimage.c b/util/mkimage.c
|
|
index a26cf76f72..bab1227601 100644
|
|
--- a/util/mkimage.c
|
|
+++ b/util/mkimage.c
|
|
@@ -869,8 +869,9 @@ grub_install_generate_image (const char *dir, const char *prefix,
|
|
char *memdisk_path, char **pubkey_paths,
|
|
size_t npubkeys, char *config_path,
|
|
const struct grub_install_image_target_desc *image_target,
|
|
- int note, grub_compression_t comp, const char *dtb_path,
|
|
- const char *sbat_path, int disable_shim_lock)
|
|
+ int note, size_t appsig_size, grub_compression_t comp,
|
|
+ const char *dtb_path, const char *sbat_path,
|
|
+ int disable_shim_lock)
|
|
{
|
|
char *kernel_img, *core_img;
|
|
size_t total_module_size, core_size;
|
|
@@ -1773,11 +1774,11 @@ grub_install_generate_image (const char *dir, const char *prefix,
|
|
else
|
|
target_addr = image_target->link_addr;
|
|
if (image_target->voidp_sizeof == 4)
|
|
- grub_mkimage_generate_elf32 (image_target, note, &core_img, &core_size,
|
|
- target_addr, &layout);
|
|
+ grub_mkimage_generate_elf32 (image_target, note, appsig_size, &core_img,
|
|
+ &core_size, target_addr, &layout);
|
|
else
|
|
- grub_mkimage_generate_elf64 (image_target, note, &core_img, &core_size,
|
|
- target_addr, &layout);
|
|
+ grub_mkimage_generate_elf64 (image_target, note, appsig_size, &core_img,
|
|
+ &core_size, target_addr, &layout);
|
|
}
|
|
break;
|
|
}
|
|
diff --git a/include/grub/util/install.h b/include/grub/util/install.h
|
|
index 7df3191f47..cf4531e02b 100644
|
|
--- a/include/grub/util/install.h
|
|
+++ b/include/grub/util/install.h
|
|
@@ -67,6 +67,9 @@
|
|
N_("SBAT metadata"), 0 }, \
|
|
{ "disable-shim-lock", GRUB_INSTALL_OPTIONS_DISABLE_SHIM_LOCK, 0, 0, \
|
|
N_("disable shim_lock verifier"), 0 }, \
|
|
+ { "appended-signature-size", GRUB_INSTALL_OPTIONS_APPENDED_SIGNATURE_SIZE,\
|
|
+ "SIZE", 0, N_("Add a note segment reserving SIZE bytes for an appended signature"), \
|
|
+ 1}, \
|
|
{ "verbose", 'v', 0, 0, \
|
|
N_("print verbose messages."), 1 }
|
|
|
|
@@ -128,7 +131,8 @@ enum grub_install_options {
|
|
GRUB_INSTALL_OPTIONS_INSTALL_CORE_COMPRESS,
|
|
GRUB_INSTALL_OPTIONS_DTB,
|
|
GRUB_INSTALL_OPTIONS_SBAT,
|
|
- GRUB_INSTALL_OPTIONS_DISABLE_SHIM_LOCK
|
|
+ GRUB_INSTALL_OPTIONS_DISABLE_SHIM_LOCK,
|
|
+ GRUB_INSTALL_OPTIONS_APPENDED_SIGNATURE_SIZE
|
|
};
|
|
|
|
extern char *grub_install_source_directory;
|
|
@@ -188,7 +192,7 @@ grub_install_generate_image (const char *dir, const char *prefix,
|
|
size_t npubkeys,
|
|
char *config_path,
|
|
const struct grub_install_image_target_desc *image_target,
|
|
- int note,
|
|
+ int note, size_t appsig_size,
|
|
grub_compression_t comp, const char *dtb_file,
|
|
const char *sbat_path, const int disable_shim_lock);
|
|
|
|
diff --git a/include/grub/util/mkimage.h b/include/grub/util/mkimage.h
|
|
index 3819a67441..6f1da89b9b 100644
|
|
--- a/include/grub/util/mkimage.h
|
|
+++ b/include/grub/util/mkimage.h
|
|
@@ -51,12 +51,12 @@ grub_mkimage_load_image64 (const char *kernel_path,
|
|
const struct grub_install_image_target_desc *image_target);
|
|
void
|
|
grub_mkimage_generate_elf32 (const struct grub_install_image_target_desc *image_target,
|
|
- int note, char **core_img, size_t *core_size,
|
|
+ int note, size_t appsig_size, char **core_img, size_t *core_size,
|
|
Elf32_Addr target_addr,
|
|
struct grub_mkimage_layout *layout);
|
|
void
|
|
grub_mkimage_generate_elf64 (const struct grub_install_image_target_desc *image_target,
|
|
- int note, char **core_img, size_t *core_size,
|
|
+ int note, size_t appsig_size, char **core_img, size_t *core_size,
|
|
Elf64_Addr target_addr,
|
|
struct grub_mkimage_layout *layout);
|
|
|