From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Chris Coulson <chris.coulson@canonical.com>
Date: Fri, 19 Feb 2021 13:53:45 +0100
Subject: [PATCH] kern/efi: Add initial stack protector implementation
It works only on UEFI platforms but can be quite easily extended to
others architectures and platforms if needed.
Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Marco A Benatto <mbenatto@redhat.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
---
configure.ac | 44 ++++++++++++++++++++++++++++++----
grub-core/kern/efi/init.c | 54 ++++++++++++++++++++++++++++++++++++++++++
include/grub/efi/api.h | 19 +++++++++++++++
include/grub/stack_protector.h | 30 +++++++++++++++++++++++
acinclude.m4 | 38 +++++++++++++++++++++++++++--
grub-core/Makefile.am | 1 +
6 files changed, 179 insertions(+), 7 deletions(-)
create mode 100644 include/grub/stack_protector.h
diff --git a/configure.ac b/configure.ac
index 0059b938a..f59a7b86c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1330,12 +1330,41 @@ fi]
CFLAGS="$TARGET_CFLAGS"
-# Smashing stack protector.
+# Stack smashing protector.
grub_CHECK_STACK_PROTECTOR
-# Need that, because some distributions ship compilers that include
-# `-fstack-protector' in the default specs.
-if test "x$ssp_possible" = xyes; then
- TARGET_CFLAGS="$TARGET_CFLAGS -fno-stack-protector"
+AC_ARG_ENABLE([stack-protector],
+ AS_HELP_STRING([--enable-stack-protector],
+ [enable the stack protector]),
+ [],
+ [enable_stack_protector=no])
+if test "x$enable_stack_protector" = xno; then
+ if test "x$ssp_possible" = xyes; then
+ # Need that, because some distributions ship compilers that include
+ # `-fstack-protector' in the default specs.
+ TARGET_CFLAGS="$TARGET_CFLAGS -fno-stack-protector"
+ fi
+elif test "x$platform" != xefi; then
+ AC_MSG_ERROR([--enable-stack-protector is only supported on EFI platforms])
+elif test "x$ssp_global_possible" != xyes; then
+ AC_MSG_ERROR([--enable-stack-protector is not supported (compiler doesn't support -mstack-protector-guard=global)])
+else
+ TARGET_CFLAGS="$TARGET_CFLAGS -mstack-protector-guard=global"
+ if test "x$enable_stack_protector" = xyes; then
+ if test "x$ssp_possible" != xyes; then
+ AC_MSG_ERROR([--enable-stack-protector is not supported (compiler doesn't support -fstack-protector)])
+ fi
+ TARGET_CFLAGS="$TARGET_CFLAGS -fstack-protector"
+ elif test "x$enable_stack_protector" = xstrong; then
+ if test "x$ssp_strong_possible" != xyes; then
+ AC_MSG_ERROR([--enable-stack-protector=strong is not supported (compiler doesn't support -fstack-protector-strong)])
+ fi
+ TARGET_CFLAGS="$TARGET_CFLAGS -fstack-protector-strong"
+ else
+ # Note, -fstack-protector-all requires that the protector is disabled for
+ # functions that appear in the call stack when the canary is initialized.
+ AC_MSG_ERROR([invalid value $enable_stack_protector for --enable-stack-protector])
+ fi
+ TARGET_CPPFLAGS="$TARGET_CPPFLAGS -DGRUB_STACK_PROTECTOR=1"
fi
CFLAGS="$TARGET_CFLAGS"
@@ -2247,5 +2276,10 @@ echo "Without liblzma (no support for XZ-compressed mips images) ($liblzma_excus
else
echo "With liblzma from $LIBLZMA (support for XZ-compressed mips images)"
fi
+if test "x$enable_stack_protector" != xno; then
+echo "With stack smashing protector: Yes"
+else
+echo "With stack smashing protector: No"
+fi
echo "*******************************************************"
]
diff --git a/grub-core/kern/efi/init.c b/grub-core/kern/efi/init.c
index 97bf36906..501608f74 100644
--- a/grub-core/kern/efi/init.c
+++ b/grub-core/kern/efi/init.c
@@ -28,6 +28,58 @@
#include <grub/mm.h>
#include <grub/kernel.h>
#include <grub/lib/envblk.h>
+#include <grub/stack_protector.h>
+
+#ifdef GRUB_STACK_PROTECTOR
+
+static grub_efi_guid_t rng_protocol_guid = GRUB_EFI_RNG_PROTOCOL_GUID;
+
+/*
+ * Don't put this on grub_efi_init()'s local stack to avoid it
+ * getting a stack check.
+ */
+static grub_efi_uint8_t stack_chk_guard_buf[32];
+
+grub_addr_t __stack_chk_guard;
+
+void __attribute__ ((noreturn))
+__stack_chk_fail (void)
+{
+ /*
+ * Assume it's not safe to call into EFI Boot Services. Sorry, that
+ * means no console message here.
+ */
+ do
+ {
+ /* Do not optimize out the loop. */
+ asm volatile ("");
+ }
+ while (1);
+}
+
+static void
+stack_protector_init (void)
+{
+ grub_efi_rng_protocol_t *rng;
+
+ /* Set up the stack canary. Make errors here non-fatal for now. */
+ rng = grub_efi_locate_protocol (&rng_protocol_guid, NULL);
+ if (rng != NULL)
+ {
+ grub_efi_status_t status;
+
+ status = efi_call_4 (rng->get_rng, rng, NULL, sizeof (stack_chk_guard_buf),
+ stack_chk_guard_buf);
+ if (status == GRUB_EFI_SUCCESS)
+ grub_memcpy (&__stack_chk_guard, stack_chk_guard_buf, sizeof (__stack_chk_guard));
+ }
+}
+#else
+static void
+stack_protector_init (void)
+{
+}
+#endif
grub_addr_t grub_modbase;
@@ -92,6 +144,8 @@ grub_efi_init (void)
messages. */
grub_console_init ();
+ stack_protector_init ();
+
/* Initialize the memory management system. */
grub_efi_mm_init ();
diff --git a/include/grub/efi/api.h b/include/grub/efi/api.h
index a092fddb6..37e7b1628 100644
--- a/include/grub/efi/api.h
+++ b/include/grub/efi/api.h
@@ -344,6 +344,11 @@
{ 0x89, 0x29, 0x48, 0xbc, 0xd9, 0x0a, 0xd3, 0x1a } \
}
+#define GRUB_EFI_RNG_PROTOCOL_GUID \
+ { 0x3152bca5, 0xeade, 0x433d, \
+ { 0x86, 0x2e, 0xc0, 0x1c, 0xdc, 0x29, 0x1f, 0x44 } \
+ }
+
struct grub_efi_sal_system_table
{
grub_uint32_t signature;
@@ -2067,6 +2072,20 @@ struct grub_efi_ip6_config_manual_address {
};
typedef struct grub_efi_ip6_config_manual_address grub_efi_ip6_config_manual_address_t;
+typedef grub_efi_guid_t grub_efi_rng_algorithm_t;
+
+struct grub_efi_rng_protocol
+{
+ grub_efi_status_t (*get_info) (struct grub_efi_rng_protocol *this,
+ grub_efi_uintn_t *rng_algorithm_list_size,
+ grub_efi_rng_algorithm_t *rng_algorithm_list);
+ grub_efi_status_t (*get_rng) (struct grub_efi_rng_protocol *this,
+ grub_efi_rng_algorithm_t *rng_algorithm,
+ grub_efi_uintn_t rng_value_length,
+ grub_efi_uint8_t *rng_value);
+};
+typedef struct grub_efi_rng_protocol grub_efi_rng_protocol_t;
+
#if (GRUB_TARGET_SIZEOF_VOID_P == 4) || defined (__ia64__) \
|| defined (__aarch64__) || defined (__MINGW64__) || defined (__CYGWIN__)
diff --git a/include/grub/stack_protector.h b/include/grub/stack_protector.h
new file mode 100644
index 000000000..c88dc00b5
--- /dev/null
+++ b/include/grub/stack_protector.h
@@ -0,0 +1,30 @@
+/*
+ * GRUB -- GRand Unified Bootloader
+ * Copyright (C) 2021 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/>.
+ */
+
+#ifndef GRUB_STACK_PROTECTOR_H
+#define GRUB_STACK_PROTECTOR_H 1
+
+#include <grub/symbol.h>
+#include <grub/types.h>
+
+#ifdef GRUB_STACK_PROTECTOR
+extern grub_addr_t EXPORT_VAR (__stack_chk_guard);
+extern void __attribute__ ((noreturn)) EXPORT_FUNC (__stack_chk_fail) (void);
+#endif
+
+#endif /* GRUB_STACK_PROTECTOR_H */
diff --git a/acinclude.m4 b/acinclude.m4
index 242e829ff..21238fcfd 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -324,9 +324,9 @@ fi
])
-dnl Check if the C compiler supports `-fstack-protector'.
+dnl Check if the C compiler supports the stack protector
AC_DEFUN([grub_CHECK_STACK_PROTECTOR],[
-[# Smashing stack protector.
+[# Stack smashing protector.
ssp_possible=yes]
AC_MSG_CHECKING([whether `$CC' accepts `-fstack-protector'])
# Is this a reliable test case?
@@ -343,6 +343,40 @@ else
ssp_possible=no]
AC_MSG_RESULT([no])
[fi]
+[# Strong stack smashing protector.
+ssp_strong_possible=yes]
+AC_MSG_CHECKING([whether `$CC' accepts `-fstack-protector-strong'])
+# Is this a reliable test case?
+AC_LANG_CONFTEST([AC_LANG_SOURCE([[
+void foo (void) { volatile char a[8]; a[3]; }
+]])])
+[# `$CC -c -o ...' might not be portable. But, oh, well... Is calling
+# `ac_compile' like this correct, after all?
+if eval "$ac_compile -S -fstack-protector-strong -o conftest.s" 2> /dev/null; then]
+ AC_MSG_RESULT([yes])
+ [# Should we clear up other files as well, having called `AC_LANG_CONFTEST'?
+ rm -f conftest.s
+else
+ ssp_strong_possible=no]
+ AC_MSG_RESULT([no])
+[fi]
+[# Global stack smashing protector.
+ssp_global_possible=yes]
+AC_MSG_CHECKING([whether `$CC' accepts `-mstack-protector-guard=global'])
+# Is this a reliable test case?
+AC_LANG_CONFTEST([AC_LANG_SOURCE([[
+void foo (void) { volatile char a[8]; a[3]; }
+]])])
+[# `$CC -c -o ...' might not be portable. But, oh, well... Is calling
+# `ac_compile' like this correct, after all?
+if eval "$ac_compile -S -fstack-protector -mstack-protector-guard=global -o conftest.s" 2> /dev/null; then]
+ AC_MSG_RESULT([yes])
+ [# Should we clear up other files as well, having called `AC_LANG_CONFTEST'?
+ rm -f conftest.s
+else
+ ssp_global_possible=no]
+ AC_MSG_RESULT([no])
+[fi]
])
dnl Check if the C compiler supports `-mstack-arg-probe' (Cygwin).
diff --git a/grub-core/Makefile.am b/grub-core/Makefile.am
index a6f1b0dcd..308ad8850 100644
--- a/grub-core/Makefile.am
+++ b/grub-core/Makefile.am
@@ -92,6 +92,7 @@ endif
KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/mm.h
KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/parser.h
KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/partition.h
+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/stack_protector.h
KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/term.h
KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/time.h
KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/mm_private.h