1 files changed, 90 insertions, 0 deletions
diff --git a/futility/misc.c b/futility/misc.c
new file mode 100644
index 00000000..91962cbd
--- /dev/null
+++ b/futility/misc.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright 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 <stdint.h>
+#include <string.h>
+
+#include "gbb_header.h"
+
+static int is_null_terminated(const char *s, int len)
+{
+	len--;
+	s += len;
+	while (len-- >= 0)
+		if (!*s--)
+			return 1;
+	return 0;
+}
+
+static inline uint32_t max(uint32_t a, uint32_t b)
+{
+	return a > b ? a : b;
+}
+
+int futil_looks_like_gbb(GoogleBinaryBlockHeader *gbb, uint32_t len)
+{
+	if (memcmp(gbb->signature, GBB_SIGNATURE, GBB_SIGNATURE_SIZE))
+		return 0;
+	if (gbb->major_version > GBB_MAJOR_VER)
+		return 0;
+	if (sizeof(GoogleBinaryBlockHeader) > len)
+		return 0;
+
+	/* close enough */
+	return 1;
+}
+
+int futil_valid_gbb_header(GoogleBinaryBlockHeader *gbb, uint32_t len,
+			   uint32_t *maxlen_ptr)
+{
+	if (memcmp(gbb->signature, GBB_SIGNATURE, GBB_SIGNATURE_SIZE))
+		return 0;
+	if (gbb->major_version != GBB_MAJOR_VER)
+		return 0;
+
+	/* Check limits first, to help identify problems */
+	if (maxlen_ptr) {
+		uint32_t maxlen = gbb->header_size;
+		maxlen = max(maxlen,
+			     gbb->hwid_offset + gbb->hwid_size);
+		maxlen = max(maxlen,
+			     gbb->rootkey_offset + gbb->rootkey_size);
+		maxlen = max(maxlen,
+			     gbb->bmpfv_offset + gbb->bmpfv_size);
+		maxlen = max(maxlen,
+			     gbb->recovery_key_offset + gbb->recovery_key_size);
+		*maxlen_ptr = maxlen;
+	}
+
+	if (gbb->header_size != GBB_HEADER_SIZE || gbb->header_size > len)
+		return 0;
+	if (gbb->hwid_offset < GBB_HEADER_SIZE)
+		return 0;
+	if (gbb->hwid_offset + gbb->hwid_size > len)
+		return 0;
+	if (gbb->hwid_size) {
+		const char *s = (const char *)
+			((uint8_t *)gbb + gbb->hwid_offset);
+		if (!is_null_terminated(s, gbb->hwid_size))
+			return 0;
+	}
+	if (gbb->rootkey_offset < GBB_HEADER_SIZE)
+		return 0;
+	if (gbb->rootkey_offset + gbb->rootkey_size > len)
+		return 0;
+
+	if (gbb->bmpfv_offset < GBB_HEADER_SIZE)
+		return 0;
+	if (gbb->bmpfv_offset + gbb->bmpfv_size > len)
+		return 0;
+	if (gbb->recovery_key_offset < GBB_HEADER_SIZE)
+		return 0;
+	if (gbb->recovery_key_offset + gbb->recovery_key_size > len)
+		return 0;
+
+	/* Seems legit... */
+	return 1;
+}