cbfstool: Add support for hashes as file metadata

They allow optimizing a verification of a whole CBFS image by only
dealing with the headers (assuming you choose to trust the hash
algorithm(s)).

The format allows for multiple hashes for a single file, and cbfstool
can handle them, but right now it can't generate such headers.

Loosely based on Sol's work in http://review.coreboot.org/#/c/10147/,
but using the compatible file attribute format. vboot is now a hard
dependency of the build process, but we import it into the tree for
quite a while now.

Change-Id: I9f14f30537d676ce209ad612e7327c6f4810b313
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/11767
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

util/cbfstool/cbfs_image.h

@@ -36,6 +36,10 @@ struct cbfs_image {
  * enum comp_algo if it's supported, or a number < 0 otherwise. */
 int cbfs_parse_comp_algo(const char *name);
 
+/* Given the string name of a hash algorithm, return the corresponding
+ * id if it's supported, or a number < 0 otherwise. */
+int cbfs_parse_hash_algo(const char *name);
+
 /* Given a pointer, serialize the header from host-native byte format
  * to cbfs format, i.e. big-endian. */
 void cbfs_put_header(void *dest, const struct cbfs_header *header);
@@ -184,4 +188,10 @@ struct cbfs_file_attribute *cbfs_file_next_attr(struct cbfs_file *file,
 struct cbfs_file_attribute *cbfs_add_file_attr(struct cbfs_file *header,
 					       uint32_t tag,
 					       uint32_t size);
+
+/* Adds an extended attribute to header, containing a hash of buffer's data of
+ * the type specified by hash_type.
+ * Returns 0 on success, -1 on error. */
+int cbfs_add_file_hash(struct cbfs_file *header, struct buffer *buffer,
+	enum vb2_hash_algorithm hash_type);
 #endif