Add hwid digest field to GBB header

This adds a field in the GBB header to store the sha256 digest of
the HWID string, and updates gbb_utility so that it stores the
digest when it modifies the HWID. Because this is a new field,
the GBB_MINOR_VER is incremented.

BUG=chromium:415227
BRANCH=ToT
TEST=make runtests, VBOOT2=1 make runtests

Since the GBB is in the RO firmware, there should be no side
effects for existing devices (but even without that, they should
handle a minor version change without complaint).

Change-Id: Icdb2a0b564677b0b65e58df897d2ec5af3964998
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/221360

Makefile

@@ -175,7 +175,7 @@ endif
 
 # And a few more default utilities
 LD = ${CC}
-CXX ?= g++ # HEY: really?
+CXX ?= g++
 PKG_CONFIG ?= pkg-config
 
 # Determine QEMU architecture needed, if any

firmware/2lib/include/2struct.h

@@ -315,7 +315,8 @@ struct vb2_shared_data {
 
 /* VB2 GBB struct version */
 #define VB2_GBB_MAJOR_VER      1
-#define VB2_GBB_MINOR_VER      1
+#define VB2_GBB_MINOR_VER      2
+/* v1.2 - added fields for sha256 digest of the HWID */
 
 /* Flags for vb2_gbb_header.flags */
 enum vb2_gbb_flag {
@@ -388,7 +389,13 @@ struct vb2_gbb_header {
 	uint32_t recovery_key_offset;	/* Recovery key */
 	uint32_t recovery_key_size;
 
-	uint8_t  pad[80]; /* To match GBB_HEADER_SIZE.  Initialize to 0. */
+	/* Added in version 1.2 */
+	uint8_t  hwid_digest[32];	/* sha256 */
+
+	uint8_t  pad[48]; /* To match EXPECTED_GBB_HEADER_SIZE. Init to 0. */
 } __attribute__((packed));
 
+/* The GBB is used outside of vboot_reference, so this size is important. */
+#define EXPECTED_GBB_HEADER_SIZE 128
+
 #endif  /* VBOOT_REFERENCE_VBOOT_2STRUCT_H_ */

firmware/include/gbb_header.h

@@ -26,7 +26,8 @@
  * return default values for those fields.
  */
 #define GBB_MAJOR_VER      1
-#define GBB_MINOR_VER      1
+#define GBB_MINOR_VER      2
+/* v1.2 - added field to hold sha256 digest of the HWID */
 
 /* Maximum length of a HWID in bytes, counting terminating null. */
 #define GBB_HWID_MAX_SIZE  256
@@ -86,8 +87,10 @@ typedef struct GoogleBinaryBlockHeader
 	uint32_t bmpfv_size;
 	uint32_t recovery_key_offset;	/* Recovery key */
 	uint32_t recovery_key_size;
+	/* Added in version 1.2 */
+	uint8_t  hwid_digest[32];	/* sha256 */
 
-	uint8_t  pad[80]; /* To match GBB_HEADER_SIZE.  Initialize to 0. */
+	uint8_t  pad[48]; /* To match GBB_HEADER_SIZE.  Initialize to 0. */
 } __attribute__((packed)) GoogleBinaryBlockHeader;
 
 #ifdef __cplusplus

futility/cmd_gbb_utility.c

@@ -29,6 +29,7 @@ static void print_help(const char *prog)
 		"with following options:\n"
 		"     --hwid          \tReport hardware id (default).\n"
 		"     --flags         \tReport header flags.\n"
+		"     --digest        \tReport digest of hwid (>= v1.2)\n"
 		" -k, --rootkey=FILE  \tFile name to export Root Key.\n"
 		" -b, --bmpfv=FILE    \tFile name to export Bitmap FV.\n"
 		" -r  --recoverykey=FILE\tFile name to export Recovery Key.\n"
@@ -55,6 +56,10 @@ static void print_help(const char *prog)
 		prog, prog, prog, prog);
 }
 
+enum {
+	OPT_DIGEST = 1000,
+};
+
 /* Command line options */
 static const struct option long_opts[] = {
 	/* name    hasarg *flag val */
@@ -67,6 +72,7 @@ static const struct option long_opts[] = {
 	{"recoverykey", 1, NULL, 'R'},
 	{"hwid", 2, NULL, 'i'},
 	{"flags", 2, NULL, 'L'},
+	{"digest", 0, NULL, OPT_DIGEST},
 	{NULL, 0, NULL, 0},
 };
 
@@ -340,6 +346,7 @@ static int do_gbb_utility(int argc, char *argv[])
 	char *opt_hwid = NULL;
 	char *opt_flags = NULL;
 	int sel_hwid = 0;
+	int sel_digest = 0;
 	int sel_flags = 0;
 	uint8_t *inbuf = NULL;
 	off_t filesize;
@@ -386,6 +393,9 @@ static int do_gbb_utility(int argc, char *argv[])
 			opt_flags = optarg;
 			sel_flags = 1;
 			break;
+		case OPT_DIGEST:
+			sel_digest = 1;
+			break;
 		case '?':
 			errorcnt++;
 			if (optopt)
@@ -437,7 +447,7 @@ static int do_gbb_utility(int argc, char *argv[])
 
 		/* With no args, show the HWID */
 		if (!opt_rootkey && !opt_bmpfv && !opt_recoverykey
-		    && !sel_flags)
+		    && !sel_flags && !sel_digest)
 			sel_hwid = 1;
 
 		inbuf = read_entire_file(infile, &filesize);
@@ -457,6 +467,9 @@ static int do_gbb_utility(int argc, char *argv[])
 			       gbb->hwid_size ? (char *)(gbb_base +
 							 gbb->
 							 hwid_offset) : "");
+		if (sel_digest)
+			print_hwid_digest(gbb, "digest: ", "\n");
+
 		if (sel_flags)
 			printf("flags: 0x%08x\n", gbb->flags);
 		if (opt_rootkey)
@@ -540,6 +553,7 @@ static int do_gbb_utility(int argc, char *argv[])
 				       gbb->hwid_size);
 				strcpy((char *)(gbb_base + gbb->hwid_offset),
 				       opt_hwid);
+				update_hwid_digest(gbb);
 			}
 		}
 

futility/cmd_show.c

@@ -141,8 +141,8 @@ int futil_cb_show_gbb(struct futil_traverse_state_s *state)
 	}
 
 	printf("GBB content:\n");
-	printf("  HWID:                  %s\n",
+	printf("  HWID:                  %s\n", buf + gbb->hwid_offset);
-	       (const char *)(buf + gbb->hwid_offset));
+	print_hwid_digest(gbb, "     digest:             ", "\n");
 
 	pubkey = (VbPublicKey *)(buf + gbb->rootkey_offset);
 	if (PublicKeyLooksOkay(pubkey, gbb->rootkey_size)) {

futility/futility.c

@@ -129,7 +129,7 @@ static void log_args(int argc, char *argv[])
 	log_open();
 
 	/* delimiter */
-	log_str(NULL, "##### HEY #####");
+	log_str(NULL, "##### LOG #####");
 
 	/* Can we tell who called us? */
 	parent = getppid();

futility/futility.h

@@ -71,6 +71,14 @@ int futil_looks_like_gbb(GoogleBinaryBlockHeader *gbb, uint32_t len);
 int futil_valid_gbb_header(GoogleBinaryBlockHeader *gbb, uint32_t len,
 			   uint32_t *maxlen);
 
+/* For GBB v1.2 and later, update the hwid_digest */
+void update_hwid_digest(GoogleBinaryBlockHeader *gbb);
+
+/* For GBB v1.2 and later, print the stored digest of the HWID (and whether
+ * it's correct). Return true if it is correct. */
+int print_hwid_digest(GoogleBinaryBlockHeader *gbb,
+		      const char *banner, const char *footer);
+
 /* Copies a file or dies with an error message */
 void futil_copy_file_or_die(const char *infile, const char *outfile);
 

futility/misc.c

@@ -114,6 +114,57 @@ int futil_valid_gbb_header(GoogleBinaryBlockHeader *gbb, uint32_t len,
 	return 1;
 }
 
+/* For GBB v1.2 and later, print the stored digest of the HWID (and whether
+ * it's correct). Return true if it is correct. */
+int print_hwid_digest(GoogleBinaryBlockHeader *gbb,
+		      const char *banner, const char *footer)
+{
+	printf("%s", banner);
+
+	/* There isn't one for v1.1 and earlier, so assume it's good. */
+	if (gbb->minor_version < 2) {
+		printf("<none>%s", footer);
+		return 1;
+	}
+
+	uint8_t *buf = (uint8_t *)gbb;
+	char *hwid_str = (char *)(buf + gbb->hwid_offset);
+	int is_valid = 0;
+	uint8_t* digest = DigestBuf(buf + gbb->hwid_offset,
+				    strlen(hwid_str),
+				    SHA256_DIGEST_ALGORITHM);
+	if (digest) {
+		int i;
+		is_valid = 1;
+		/* print it, comparing as we go */
+		for (i = 0; i < SHA256_DIGEST_SIZE; i++) {
+			printf("%02x", gbb->hwid_digest[i]);
+			if (gbb->hwid_digest[i] != digest[i])
+				is_valid = 0;
+		}
+		free(digest);
+	}
+
+	printf("   %s", is_valid ? "valid" : "<invalid>");
+	printf("%s", footer);
+	return is_valid;
+}
+
+/* For GBB v1.2 and later, update the hwid_digest field. */
+void update_hwid_digest(GoogleBinaryBlockHeader *gbb)
+{
+	/* There isn't one for v1.1 and earlier */
+	if (gbb->minor_version < 2)
+		return;
+
+	uint8_t *buf = (uint8_t *)gbb;
+	char *hwid_str = (char *)(buf + gbb->hwid_offset);
+	uint8_t* digest = DigestBuf(buf + gbb->hwid_offset,
+				    strlen(hwid_str),
+				    SHA256_DIGEST_ALGORITHM);
+	memcpy(gbb->hwid_digest, digest, SHA256_DIGEST_SIZE);
+	free(digest);
+}
 
 /*
  * TODO: All sorts of race conditions likely here, and everywhere this is used.

tests/futility/test_gbb_utility.sh

@@ -201,6 +201,33 @@ cat ${TMP}.blob | ${REPLACE} 0x2c 0x00 > ${TMP}.blob.bad
 ${FUTILITY} gbb_utility -g --recoverykey ${TMP}.read2 ${TMP}.blob.bad
 if ${FUTILITY} gbb_utility -s --recoverykey ${TMP}.data2 ${TMP}.blob.bad; then false; fi
 
+
+# GBB v1.2 adds a sha256 digest field in what was previously padding:
+#
+# hwid_digest:          0x0030  xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx
+#                       0x0040  xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx
+# pad:                  0x0050  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+#                       0x0060  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+#                       0x0070  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+# (HWID)                0x0080  30 31 32 33 34 35 36 37 38 39 41 42 43 44 45 00
+
+# See that the digest is updated properly.
+hwid="123456789ABCDEF"
+${FUTILITY} gbb_utility -s -i ${hwid} ${TMP}.blob
+expect=$(echo -n "$hwid" | sha256sum | cut -d ' ' -f 1)
+[ $(echo -n ${expect} | wc -c) == "64" ]
+${FUTILITY} gbb_utility -g --digest ${TMP}.blob | grep ${expect}
+
+# Garble the digest, see that it's noticed.
+# (assuming these zeros aren't present)
+cat ${TMP}.blob | ${REPLACE} 0x33 0x00 0x00 0x00 0x00 0x00 > ${TMP}.blob.bad
+${FUTILITY} gbb_utility -g --digest ${TMP}.blob.bad | grep '0000000000'
+${FUTILITY} gbb_utility -g --digest ${TMP}.blob.bad | grep 'invalid'
+
+# Garble the HWID. The digest is unchanged, but now invalid.
+cat ${TMP}.blob | ${REPLACE} 0x84 0x70 0x71 0x72 > ${TMP}.blob.bad
+${FUTILITY} gbb_utility -g --digest ${TMP}.blob.bad | grep 'invalid'
+
 # cleanup
 rm -f ${TMP}*
 exit 0

tests/futility/test_not_really.c

@@ -1,15 +1,19 @@
 /*
- * Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
+ * Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include <stdio.h>
+#include "gbb_header.h"
 #include "test_common.h"
 
 int main(int argc, char *argv[])
 {
+	TEST_EQ(sizeof(GoogleBinaryBlockHeader),
+		GBB_HEADER_SIZE,
+		"sizeof(GoogleBinaryBlockHeader)");
+
 	TEST_EQ(0, 0, "Not Really A");
 
 	return !gTestSuccess;
 }
-

tests/vb2_misc_tests.c

@@ -134,6 +134,10 @@ static void gbb_tests(void)
 
 	struct vb2_gbb_header gbbdest;
 
+	TEST_EQ(sizeof(struct vb2_gbb_header),
+		EXPECTED_GBB_HEADER_SIZE,
+		"sizeof(struct vb2_gbb_header)");
+
 	reset_common_data();
 
 	/* Good contents */

utility/bmpblk_utility.cc

@@ -499,7 +499,7 @@ namespace vboot_reference {
     config_.header.minor_version = minor_version_;
     config_.header.number_of_localizations = config_.localizations.size();
     config_.header.number_of_screenlayouts = config_.localizations[0].size();
-    // HEY: this is part of the yaml consistency check
+    // NOTE: this is part of the yaml consistency check
     for (unsigned int i = 1; i < config_.localizations.size(); ++i) {
       assert(config_.header.number_of_screenlayouts ==
              config_.localizations[i].size());