114 lines
3.4 KiB
Diff
114 lines
3.4 KiB
Diff
From 8a2a8d6021d926f00c5f85dab2d66f4ed8be86a2 Mon Sep 17 00:00:00 2001
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From: Colin Watson <cjwatson@ubuntu.com>
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Date: Tue, 23 Oct 2012 10:40:49 -0400
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Subject: [PATCH] Don't allow insmod when secure boot is enabled.
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Hi,
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Fedora's patch to forbid insmod in UEFI Secure Boot environments is fine
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as far as it goes. However, the insmod command is not the only way that
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modules can be loaded. In particular, the 'normal' command, which
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implements the usual GRUB menu and the fully-featured command prompt,
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will implicitly load commands not currently loaded into memory. This
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permits trivial Secure Boot violations by writing commands implementing
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whatever you want to do and pointing $prefix at the malicious code.
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I'm currently test-building this patch (replacing your current
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grub-2.00-no-insmod-on-sb.patch), but this should be more correct. It
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moves the check into grub_dl_load_file.
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---
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grub-core/kern/dl.c | 17 +++++++++++++++++
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grub-core/kern/efi/efi.c | 28 ++++++++++++++++++++++++++++
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include/grub/efi/efi.h | 1 +
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3 files changed, 46 insertions(+)
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diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c
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index a498682..2578fce 100644
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--- a/grub-core/kern/dl.c
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+++ b/grub-core/kern/dl.c
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@@ -43,6 +43,10 @@
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#include <sys/mman.h>
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#endif
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+#ifdef GRUB_MACHINE_EFI
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+#include <grub/efi/efi.h>
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+#endif
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+
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#pragma GCC diagnostic ignored "-Wcast-align"
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@@ -721,6 +725,19 @@ grub_dl_load_file (const char *filename)
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void *core = 0;
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grub_dl_t mod = 0;
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+#ifdef GRUB_MACHINE_EFI
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+ if (grub_efi_secure_boot ())
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+ {
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+#if 0
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+ /* This is an error, but grub2-mkconfig still generates a pile of
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+ * insmod commands, so emitting it would be mostly just obnoxious. */
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+ grub_error (GRUB_ERR_ACCESS_DENIED,
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+ "Secure Boot forbids loading module from %s", filename);
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+#endif
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+ return 0;
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+ }
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+#endif
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+
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file = grub_file_open (filename);
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if (! file)
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return 0;
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diff --git a/grub-core/kern/efi/efi.c b/grub-core/kern/efi/efi.c
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index 820968f..ad7aa8d 100644
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--- a/grub-core/kern/efi/efi.c
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+++ b/grub-core/kern/efi/efi.c
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@@ -259,6 +259,34 @@ grub_efi_set_variable(const char *var, const grub_efi_guid_t *guid,
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return grub_error (GRUB_ERR_IO, "could not set EFI variable `%s'", var);
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}
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+grub_efi_boolean_t
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+grub_efi_secure_boot (void)
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+{
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+ grub_efi_guid_t efi_var_guid = GRUB_EFI_GLOBAL_VARIABLE_GUID;
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+ grub_size_t datasize;
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+ char *secure_boot = NULL;
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+ char *setup_mode = NULL;
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+ grub_efi_boolean_t ret = 0;
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+
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+ secure_boot = grub_efi_get_variable("SecureBoot", &efi_var_guid, &datasize);
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+
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+ if (datasize != 1 || !secure_boot)
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+ goto out;
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+
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+ setup_mode = grub_efi_get_variable("SetupMode", &efi_var_guid, &datasize);
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+
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+ if (datasize != 1 || !setup_mode)
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+ goto out;
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+
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+ if (*secure_boot && !*setup_mode)
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+ ret = 1;
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+
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+ out:
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+ grub_free (secure_boot);
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+ grub_free (setup_mode);
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+ return ret;
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+}
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+
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#pragma GCC diagnostic ignored "-Wcast-align"
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/* Search the mods section from the PE32/PE32+ image. This code uses
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diff --git a/include/grub/efi/efi.h b/include/grub/efi/efi.h
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index 9370fd5..a000c38 100644
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--- a/include/grub/efi/efi.h
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+++ b/include/grub/efi/efi.h
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@@ -72,6 +72,7 @@ EXPORT_FUNC (grub_efi_set_variable) (const char *var,
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const grub_efi_guid_t *guid,
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void *data,
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grub_size_t datasize);
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+grub_efi_boolean_t EXPORT_FUNC (grub_efi_secure_boot) (void);
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int
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EXPORT_FUNC (grub_efi_compare_device_paths) (const grub_efi_device_path_t *dp1,
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const grub_efi_device_path_t *dp2);
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--
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1.7.12.1
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