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vboot2: Scramble the GBB magic number

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Compiling in the GBB magic number as is causes any tools that search for the
number to fail. This patch allows firmware to embed XOR'ed signature.

TEST=Booted Nyan in normal mode. FAFT:firmware_DevMode passes.
BUG=none
BRANCH=none
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>

Change-Id: Id18905a9969af3db24151e7c51332d0e94405108
Reviewed-on: https://chromium-review.googlesource.com/205416
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Queue: Daisuke Nojiri <dnojiri@chromium.org>
Tested-by: Daisuke Nojiri <dnojiri@chromium.org>
This commit is contained in:
Daisuke Nojiri
2014-06-24 12:26:39 -07:00
committed by chrome-internal-fetch
parent 25c95d0774
commit fc17308c39
3 changed files with 28 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
firmware/2lib/2misc.c
View File

@@ -14,6 +14,17 @@
#include "2sha.h" #include "2sha.h"
#include "2rsa.h" #include "2rsa.h"
int vb2_validate_gbb_signature(uint8_t *sig) {
const static uint8_t sig_xor[VB2_GBB_SIGNATURE_SIZE] =
VB2_GBB_XOR_SIGNATURE;
int i;
for (i = 0; i < VB2_GBB_SIGNATURE_SIZE; i++) {
if (sig[i] != (sig_xor[i] ^ VB2_GBB_XOR_CHARS[i]))
return VB2_ERROR_GBB_MAGIC;
}
return VB2_SUCCESS;
}
void vb2_workbuf_from_ctx(struct vb2_context *ctx, struct vb2_workbuf *wb) void vb2_workbuf_from_ctx(struct vb2_context *ctx, struct vb2_workbuf *wb)
{ {
vb2_workbuf_init(wb, ctx->workbuf + ctx->workbuf_used, vb2_workbuf_init(wb, ctx->workbuf + ctx->workbuf_used,
@@ -22,8 +33,6 @@ void vb2_workbuf_from_ctx(struct vb2_context *ctx, struct vb2_workbuf *wb)
int vb2_read_gbb_header(struct vb2_context *ctx, struct vb2_gbb_header *gbb) int vb2_read_gbb_header(struct vb2_context *ctx, struct vb2_gbb_header *gbb)
{ {
static const uint8_t expect_sig[VB2_GBB_SIGNATURE_SIZE] =
VB2_GBB_SIGNATURE;
int rv; int rv;
/* Read the entire header */ /* Read the entire header */
@@ -32,8 +41,9 @@ int vb2_read_gbb_header(struct vb2_context *ctx, struct vb2_gbb_header *gbb)
return rv; return rv;
/* Make sure it's really a GBB */ /* Make sure it's really a GBB */
if (memcmp(gbb->signature, expect_sig, sizeof(expect_sig))) rv = vb2_validate_gbb_signature(gbb->signature);
return VB2_ERROR_GBB_MAGIC; if (rv)
return rv;
/* Check for compatible version */ /* Check for compatible version */
if (gbb->major_version != VB2_GBB_MAJOR_VER) if (gbb->major_version != VB2_GBB_MAJOR_VER)

8
firmware/2lib/include/2misc.h
View File

@@ -22,6 +22,14 @@ static __inline struct vb2_shared_data *vb2_get_sd(struct vb2_context *ctx) {
return (struct vb2_shared_data *)ctx->workbuf; return (struct vb2_shared_data *)ctx->workbuf;
} }
/**
* Validate gbb signature (the magic number)
*
* @param sig pointer to the signature bytes to validate
* @return VB2_SUCCESS if valid or VB2_ERROR_GBB_MAGIC otherwise.
*/
int vb2_validate_gbb_signature(uint8_t *sig);
/** /**
* Initialize a work buffer from the vboot context. * Initialize a work buffer from the vboot context.
* *

7
firmware/2lib/include/2struct.h
View File

@@ -301,9 +301,14 @@ struct vb2_shared_data {
/****************************************************************************/ /****************************************************************************/
/* Signature at start of the GBB */ /* Signature at start of the GBB
* Note that if you compile in the signature as is, you are likely to break any
* tools that search for the signature. */
#define VB2_GBB_SIGNATURE "$GBB" #define VB2_GBB_SIGNATURE "$GBB"
#define VB2_GBB_SIGNATURE_SIZE 4 #define VB2_GBB_SIGNATURE_SIZE 4
#define VB2_GBB_XOR_CHARS "****"
/* TODO: can we write a macro to produce this at compile time? */
#define VB2_GBB_XOR_SIGNATURE { 0x0e, 0x6d, 0x68, 0x68 }
/* VB2 GBB struct version */ /* VB2 GBB struct version */
#define VB2_GBB_MAJOR_VER 1 #define VB2_GBB_MAJOR_VER 1