Fix decode functionality

Fix error when cannot decode EFI_SECTION_USER_INTERFACE
Fix error in File size logic within NextFwFile functionality

Signed-off-by: BrentHoltsclaw <brent.holtsclaw@intel.com>

chipsec/hal/spi_uefi.py

@@ -263,7 +263,10 @@ def build_efi_modules_tree( _uefi, fwtype, data, Size, offset, polarity ):
                 sec.calc_hashes( sec.HeaderSize )
             elif sec.Type == EFI_SECTION_USER_INTERFACE:
                 # "leaf" UI section: update section's UI name
-                sec.ui_string = sec.Image[sec.HeaderSize:-2].decode("utf-16")
+                try:
+                    sec.ui_string = sec.Image[sec.HeaderSize:-2].decode("utf-16")
+                except UnicodeDecodeError:
+                    pass
             elif sec.Type == EFI_SECTION_GUID_DEFINED:
                 if len(sec.Image) < sec.HeaderSize+EFI_GUID_DEFINED_SECTION_size:
                     logger().warn("EFI Section seems to be malformed")

chipsec/hal/uefi_common.py

@@ -682,7 +682,7 @@ def NextFwFile(FvImage, FvLength, fof, polarity):
             next_offset = fof + 8
             return (cur_offset, next_offset, None, None, None, None, None, None, None, None, update_or_deleted, None)
         #Get File size
-        if Attributes & FFS_ATTRIB_LARGE_FILE:
+        if Attributes & FFS_ATTRIB_LARGE_FILE and len(FvImage) > fof + struct.calcsize(EFI_FFS_FILE_HEADER2):
             fsize = struct.unpack("Q",FvImage[fof+file_header_size:fof+file_header_size+struct.calcsize("Q")])[0]
             fsize &= 0xFFFFFFFF
             if fsize == 0 or fsize > FvLength-fof: