def process_loadable_segments()

in scripts/process_fips_module.py [0:0]

• 28 lines of code
• 15 McCabe index (conditional complexity)

def process_loadable_segments(elf_file):
    """
    Finds all loadable segments in the module and ensures that the assumptions made by our runtime
    integrity verification code are valid. Returns the list of loadable segments. If an assumption
    is found to be invalid, an exception will be thrown.
    """

    # Find all loadable segments and calculate their sizes and offsets
    loadable_segments = []
    writeable_segment = None
    for segment in elf_file.iter_segments():
        if segment["p_type"] == "PT_LOAD":

            logging.debug("PT_LOAD: Offset {} VAddr {} PAddr {} FileSz {} MemSz {} Align {}".format(
                hex(segment["p_offset"]),
                hex(segment["p_vaddr"]),
                hex(segment["p_paddr"]),
                hex(segment["p_filesz"]),
                hex(segment["p_memsz"]),
                hex(segment["p_align"])
            ))

            loadable_segments.append(segment)

            if writeable_segment is not None:
                # There must be exactly one writeable segment, and it must be the last of the
                # PT_LOAD segments
                logging.error("Found more than one loadable, writeable segment!")
                raise RuntimeError

            if segment["p_flags"] & PF_W != 0:                
                writeable_segment = segment

    writeable_segment_sections = []
    for section in elf_file.iter_sections():
        if writeable_segment.section_in_segment(section):
            writeable_segment_sections.append(section)

    # We set our FIPS module boundary based on where the .data section starts (since it and the
    # .bss section cannot be included in the HMAC). Therefore, .data and .bss must be the second
    # last and last sections of that segment, respectively.
    if writeable_segment_sections[-2].name != ".data" or \
        writeable_segment_sections[-1].name != ".bss":
        logging.error("Unexpected section order in writeable segment!")
        raise RuntimeError

    return loadable_segments