get_trust_anchor.py 文件源码

def extract_trust_anchors_from_xml(trust_anchor_xml):
    """Takes a bytestring with the XML from IANA; returns a list of trust anchors."""
    # Turn the bytes from trust_anchor_xml into a string
    trust_anchor_xml_string = bytes_to_string(trust_anchor_xml)
    # Sanity check: make sure there is enough text in the returned stuff
    if len(trust_anchor_xml_string) < 100:
        die("The XML was too short: {} chars.".format(len(trust_anchor_xml_string)))
    # ElementTree requries a file so use StringIO to turn the string into a file
    try:
        trust_anchor_as_file = StringIO(trust_anchor_xml_string)  # This works for Python 3
    except:
        trust_anchor_as_file = StringIO(unicode(trust_anchor_xml_string))  # Needed for Python 2
    # Get the tree
    trust_anchor_tree = xml.etree.ElementTree.ElementTree(file=trust_anchor_as_file)
    # Get all the KeyDigest elements
    digest_elements = trust_anchor_tree.findall(".//KeyDigest")
    print("There were {} KeyDigest elements in the trust anchor file.".format(\
        len(digest_elements)))
    trust_anchors = []  # Global list of dicts that is taken from the XML file
    # Collect the values for the KeyDigest subelements and attributes
    for (count, this_digest_element) in enumerate(digest_elements):
        digest_value_dict = {}
        for this_subelement in ["KeyTag", "Algorithm", "DigestType", "Digest"]:
            try:
                this_key_tag_text = (this_digest_element.find(this_subelement)).text
            except:
                die("Did not find {} element in a KeyDigest in a trust anchor.".format(\
                    this_subelement))
            digest_value_dict[this_subelement] = this_key_tag_text
        for this_attribute in ["validFrom", "validUntil"]:
            if this_attribute in this_digest_element.keys():
                digest_value_dict[this_attribute] = this_digest_element.attrib[this_attribute]
            else:
                digest_value_dict[this_attribute] = ""  # Missing attributes get empty values
        # Save this to the global trust_anchors list
        print("Added the trust anchor {} to the list:\n{}".format(count, pprint.pformat(\
            digest_value_dict)))
        trust_anchors.append(digest_value_dict)
    if len(trust_anchors) == 0:
        die("There were no trust anchors found in the XML file.")
    return trust_anchors