112 lines
3.5 KiB
Diff
112 lines
3.5 KiB
Diff
From aacf59cc01555c645e5594c0cdaa0e6735921e80 Mon Sep 17 00:00:00 2001
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From: Jason Wessel <jason.wessel@windriver.com>
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Date: Thu, 17 Oct 2019 12:35:01 -0700
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Subject: [PATCH] grub verify: Add strict_security variable
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With strict_security set to 1, it is impossible to change the value of
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check_signatures. It will also cause grub to reboot instead of
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allowing a rescue or grub shell, which could allow an end user to
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alter boot arguments or load some other binary.
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Upstream-Status: Pending
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Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
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---
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grub-core/commands/pgp.c | 16 +++++++++++++++-
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grub-core/kern/main.c | 9 +++++++++
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grub-core/normal/main.c | 7 +++++--
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3 files changed, 29 insertions(+), 3 deletions(-)
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diff --git a/grub-core/commands/pgp.c b/grub-core/commands/pgp.c
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index e60a29a..578ad18 100644
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--- a/grub-core/commands/pgp.c
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+++ b/grub-core/commands/pgp.c
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@@ -864,6 +864,7 @@ grub_cmd_verify_signature (grub_extcmd_context_t ctxt,
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}
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static int sec = 0;
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+static int strict_sec = 0;
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static grub_err_t
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grub_pubkey_init (grub_file_t io, enum grub_file_type type __attribute__ ((unused)),
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@@ -930,10 +931,21 @@ static char *
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grub_env_write_sec (struct grub_env_var *var __attribute__ ((unused)),
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const char *val)
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{
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- sec = (*val == '1') || (*val == 'e');
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+ if (!strict_sec)
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+ sec = (*val == '1') || (*val == 'e');
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return grub_strdup (sec ? "enforce" : "no");
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}
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+static char *
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+grub_env_write_strict_sec (struct grub_env_var *var __attribute__ ((unused)),
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+ const char *val)
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+{
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+ /* once it is set, it is a one way transition */
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+ if (!strict_sec)
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+ strict_sec = (*val == '1') || (*val == 'e');
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+ return grub_strdup (strict_sec ? "enforce" : "no");
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+}
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+
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static grub_ssize_t
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pseudo_read (struct grub_file *file, char *buf, grub_size_t len)
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{
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@@ -973,7 +985,9 @@ GRUB_MOD_INIT(pgp)
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sec = 0;
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grub_register_variable_hook ("check_signatures", 0, grub_env_write_sec);
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+ grub_register_variable_hook ("strict_security", 0, grub_env_write_strict_sec);
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grub_env_export ("check_signatures");
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+ grub_env_export ("strict_security");
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grub_pk_trusted = 0;
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FOR_MODULES (header)
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diff --git a/grub-core/kern/main.c b/grub-core/kern/main.c
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index 73967e2..86e7f35 100644
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--- a/grub-core/kern/main.c
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+++ b/grub-core/kern/main.c
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@@ -30,6 +30,7 @@
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#include <grub/reader.h>
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#include <grub/parser.h>
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#include <grub/verify.h>
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+#include <grub/time.h>
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#ifdef GRUB_MACHINE_PCBIOS
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#include <grub/machine/memory.h>
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@@ -312,5 +313,13 @@ grub_main (void)
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grub_boot_time ("After execution of embedded config. Attempt to go to normal mode");
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grub_load_normal_mode ();
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+ const char *val = grub_env_get ("strict_security");
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+ if (val && (val[0] == '1' || val[0] == 'e'))
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+ while (1) {
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+ grub_printf("Boot configuration error - Attempting reboot\n");
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+ grub_sleep(3);
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+ grub_dl_load ("reboot");
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+ grub_command_execute ("reboot", 0, 0);
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+ }
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grub_rescue_run ();
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}
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diff --git a/grub-core/normal/main.c b/grub-core/normal/main.c
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index c4ebe9e..2c3f4f8 100644
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--- a/grub-core/normal/main.c
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+++ b/grub-core/normal/main.c
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@@ -302,8 +302,11 @@ grub_enter_normal_mode (const char *config)
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grub_boot_time ("Entering normal mode");
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nested_level++;
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grub_normal_execute (config, 0, 0);
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- grub_boot_time ("Entering shell");
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- grub_cmdline_run (0, 1);
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+ const char *val = grub_env_get ("strict_security");
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+ if (!(val && (val[0] == '1' || val[0] == 'e'))) {
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+ grub_boot_time ("Entering shell");
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+ grub_cmdline_run (0, 1);
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+ }
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nested_level--;
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if (grub_normal_exit_level)
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grub_normal_exit_level--;
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--
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2.17.1
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