From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg59@coreos.com>
Date: Sun, 9 Aug 2015 15:48:51 -0700
Subject: [PATCH] Add BIOS boot measurement
Measure the on-disk grub core on BIOS systems - unlike UEFI, the firmware
can't do this stage for us.
---
grub-core/boot/i386/pc/boot.S | 30 +++++++++++++++++++++++++-
grub-core/boot/i386/pc/diskboot.S | 44 +++++++++++++++++++++++++++++++++++++++
2 files changed, 73 insertions(+), 1 deletion(-)
diff --git a/grub-core/boot/i386/pc/boot.S b/grub-core/boot/i386/pc/boot.S
index ea167fe12..c1df86dec 100644
--- a/grub-core/boot/i386/pc/boot.S
+++ b/grub-core/boot/i386/pc/boot.S
@@ -24,11 +24,14 @@
* defines for the code go here
*/
+#define TPM 1
+
/* Print message string */
#define MSG(x) movw $x, %si; call LOCAL(message)
#define ERR(x) movw $x, %si; jmp LOCAL(error_message)
.macro floppy
+#ifndef TPM
part_start:
LOCAL(probe_values):
@@ -85,6 +88,7 @@ fd_probe_error_string: .asciz "Floppy"
movb MACRO_DOLLAR(79), %ch
jmp LOCAL(final_init)
+#endif
.endm
.macro scratch
@@ -252,6 +256,7 @@ real_start:
/* set %si to the disk address packet */
movw $disk_address_packet, %si
+#ifndef TPM
/* check if LBA is supported */
movb $0x41, %ah
movw $0x55aa, %bx
@@ -271,6 +276,7 @@ real_start:
andw $1, %cx
jz LOCAL(chs_mode)
+#endif
LOCAL(lba_mode):
xorw %ax, %ax
@@ -314,6 +320,9 @@ LOCAL(lba_mode):
jmp LOCAL(copy_buffer)
LOCAL(chs_mode):
+#ifdef TPM
+ jmp LOCAL(general_error)
+#else
/*
* Determine the hard disk geometry from the BIOS!
* We do this first, so that LS-120 IDE floppies work correctly.
@@ -425,7 +434,7 @@ setup_sectors:
jc LOCAL(read_error)
movw %es, %bx
-
+#endif /* TPM */
LOCAL(copy_buffer):
/*
* We need to save %cx and %si because the startup code in
@@ -448,6 +457,25 @@ LOCAL(copy_buffer):
popw %ds
popa
+#ifdef TPM
+ pusha
+
+ movw $0xBB00, %ax /* TCG_StatusCheck */
+ int $0x1A
+ test %eax, %eax
+ jnz boot /* No TPM or TPM deactivated */
+
+ movw $0xBB07, %ax /* TCG_CompactHashLogExtendEvent */
+ movw $GRUB_BOOT_MACHINE_KERNEL_ADDR, %di
+ xorl %esi, %esi
+ movl $0x41504354, %ebx /* TCPA */
+ movl $0x200, %ecx /* Measure 512 bytes */
+ movl $0x8, %edx /* PCR 8 */
+ int $0x1A
+
+ popa
+#endif
+boot:
/* boot kernel */
jmp *(LOCAL(kernel_address))
diff --git a/grub-core/boot/i386/pc/diskboot.S b/grub-core/boot/i386/pc/diskboot.S
index 68d31de0c..f4744ec6f 100644
--- a/grub-core/boot/i386/pc/diskboot.S
+++ b/grub-core/boot/i386/pc/diskboot.S
@@ -19,6 +19,8 @@
#include <grub/symbol.h>
#include <grub/machine/boot.h>
+#define TPM 1
+
/*
* defines for the code go here
*/
@@ -53,6 +55,21 @@ _start:
/* this sets up for the first run through "bootloop" */
movw $LOCAL(firstlist), %di
+#ifdef TPM
+ /* clear EAX to remove potential garbage */
+ xorl %eax, %eax
+ /* 8(%di) = number of sectors to read */
+ movw 8(%di), %ax
+
+ /* Multiply number of sectors to read with 512 bytes. EAX is 32bit
+ * which is large enough to hold values of up to 4GB. I doubt there
+ * will ever be a core.img larger than that. ;-) */
+ shll $9, %eax
+
+ /* write result to bytes_to_measure var */
+ movl %eax, bytes_to_measure
+#endif
+
/* save the sector number of the second sector in %ebp */
movl (%di), %ebp
@@ -290,6 +307,29 @@ LOCAL(copy_buffer):
/* END OF MAIN LOOP */
LOCAL(bootit):
+#ifdef TPM
+ pusha
+ movw $0xBB07, %ax /* TCG_CompactHashLogExtendEvent */
+
+ movw $0x0, %bx
+ movw %bx, %es
+
+ /* We've already measured the first 512 bytes, now measure the rest */
+ xorl %edi, %edi
+ movw $(GRUB_BOOT_MACHINE_KERNEL_ADDR + 0x200), %di
+
+ movl $0x41504354, %ebx /* EBX = "TCPA" */
+
+ /* %ecx = The length, in bytes, of the buffer to measure */
+ movl $bytes_to_measure, %esi
+ movl (%esi), %ecx
+ xorl %esi, %esi
+ movl $0x9, %edx /* PCR 9 */
+
+ int $0x1A
+
+ popa
+#endif
/* print a newline */
MSG(notification_done)
popw %dx /* this makes sure %dl is our "boot" drive */
@@ -324,6 +364,10 @@ geometry_error_string: .asciz "Geom"
read_error_string: .asciz "Read"
general_error_string: .asciz " Error"
+#ifdef TPM
+bytes_to_measure: .long 0
+#endif
+
/*
* message: write the string pointed to by %si
*