1  #!/usr/bin/env python3
       2  
       3  """Unpack a MIME message into a directory of files."""
       4  
       5  import os
       6  import email
       7  import mimetypes
       8  
       9  from email.policy import default
      10  
      11  from argparse import ArgumentParser
      12  
      13  
      14  def main():
      15      parser = ArgumentParser(description="""\
      16  Unpack a MIME message into a directory of files.
      17  """)
      18      parser.add_argument('-d', '--directory', required=True,
      19                          help="""Unpack the MIME message into the named
      20                          directory, which will be created if it doesn't already
      21                          exist.""")
      22      parser.add_argument('msgfile')
      23      args = parser.parse_args()
      24  
      25      with open(args.msgfile, 'rb') as fp:
      26          msg = email.message_from_binary_file(fp, policy=default)
      27  
      28      try:
      29          os.mkdir(args.directory)
      30      except FileExistsError:
      31          pass
      32  
      33      counter = 1
      34      for part in msg.walk():
      35          # multipart/* are just containers
      36          if part.get_content_maintype() == 'multipart':
      37              continue
      38          # Applications should really sanitize the given filename so that an
      39          # email message can't be used to overwrite important files
      40          filename = part.get_filename()
      41          if not filename:
      42              ext = mimetypes.guess_extension(part.get_content_type())
      43              if not ext:
      44                  # Use a generic bag-of-bits extension
      45                  ext = '.bin'
      46              filename = f'part-{counter:03d}{ext}'
      47          counter += 1
      48          with open(os.path.join(args.directory, filename), 'wb') as fp:
      49              fp.write(part.get_payload(decode=True))
      50  
      51  
      52  if __name__ == '__main__':
      53      main()