binder/binder/helpers.py

# Binder Helpers

# Standard Imports
import logging
import re
import socket

# 3rd Party
import dns.query
import dns.rcode
import dns.reversename
import dns.tsig
import dns.tsigkeyring
import dns.update

# App Imports
from binder import models
from binder.exceptions import KeyringException, RecordException


def add_record(dns_server, zone_name, record_name, record_type, record_data,
               ttl, key_name, create_reverse=False):
    """Parse passed elements and determine which records to create.

    Args:
      String dns_server
      String zone_name
      String record_name (just record name, not FQDN)
      String record_type (A, AAAA, etc)
      String record_data (IP address)
      Int ttl
      String key_name (from Key model)
      Boolean create_reverse (Whether to create a PTR record, default False)

    Return:
      Dict containing {description, output} from record creation
    """
    response = []
    response.append({"description": "Forward Record Creation: %s.%s" %
                     (record_name, zone_name),
                     "output": create_update(dns_server,
                                             zone_name,
                                             record_name,
                                             record_type,
                                             record_data,
                                             ttl,
                                             key_name)})

    """If requested, create a reverse PTR record.

    Given the forward record created, resolve its underlying IP.
    Use that to create the reverse record.
    reverse_ip_fqdn ex: 5.0.20.10.in-addr.arpa.
    reverse_ip: 5
    reverse_domain: 0.20.10.in-addr.arpa.
    """
    if create_reverse:
        reverse_ip_fqdn = str(dns.reversename.from_address(record_data))
        # There must be a cleaner way to figure out the ip/domain
        # for this reverse DNS record parsing.
        reverse_ip = re.search(r"([0-9]+).(.*)$", reverse_ip_fqdn).group(1)
        reverse_domain = re.search(r"([0-9]+).(.*)$", reverse_ip_fqdn).group(2)
        response.append({"description": "Reverse Record Creation: %s" % record_data,
                         "output": create_update(dns_server,
                                                 reverse_domain,
                                                 reverse_ip,
                                                 "PTR",
                                                 "%s.%s." % (record_name, zone_name),
                                                 ttl,
                                                 key_name)})

    return response


def add_cname_record(dns_server, zone_name, cname, originating_record, ttl,
                     key_name):
    """Add a CNAME record."""
    output = create_update(dns_server,
                           zone_name,
                           cname,
                           "CNAME",
                           originating_record + ".",
                           ttl,
                           key_name)

    return [{"description": "CNAME %s.%s points to %s" %
             (cname, zone_name, originating_record),
             "output": output}]


def delete_record(dns_server, rr_list, key_name):
    """Delete a list of DNS records passed as strings in rr_items."""
    server = models.BindServer.objects.get(hostname=dns_server)

    logger = logging.getLogger('binder.helpers')
    try:
        transfer_key = models.Key.objects.get(name=key_name)
    except models.Key.DoesNotExist as exc:
        logger.error(exc)
        raise KeyringException("The specified TSIG key %s does not exist in "
                               "binders configuration." % key_name)
    else:
        keyring = transfer_key.create_keyring()
        algorithm = transfer_key.algorithm

    delete_response = []
    for current_rr in rr_list:
        record_list = current_rr.split(".", 1)
        record = record_list[0]
        domain = record_list[1]
        dns_update = dns.update.Update(domain,
                                       keyring=keyring,
                                       keyalgorithm=algorithm)
        dns_update.delete(record)
        try:
            output = send_dns_update(dns_update,
                                    dns_server,
                                    server.dns_port,
                                    key_name)
        except (KeyringException, RecordException) as exc:
            delete_response.append({"description": exc,
                                    "record": current_rr,
                                    "success": False})
        else:
            delete_response.append({"description": output,
                                    "record": current_rr,
                                    "success": True})

    return delete_response


def create_update(dns_server, zone_name, record_name, record_type, record_data,
                  ttl, key_name):
    """Update/Create DNS record of name and type with passed data and ttl."""
    server = models.BindServer.objects.get(hostname=dns_server)

    logger = logging.getLogger('binder.helpers')
    try:
        transfer_key = models.Key.objects.get(name=key_name)
    except models.Key.DoesNotExist as exc:
        logger.error(exc)
        raise KeyringException("The specified TSIG key %s does not exist in "
                               "binders configuration." % key_name)
    else:
        keyring = transfer_key.create_keyring()
        algorithm = transfer_key.algorithm

    dns_update = dns.update.Update(zone_name,
                                   keyring=keyring,
                                   keyalgorithm=algorithm)
    dns_update.replace(record_name, ttl, record_type, record_data)
    output = send_dns_update(dns_update, dns_server, server.dns_port, key_name)

    return output


def ip_info(host_name):
    """Create a dictionary mapping address types to their IP's.

    If an error is encountered, key to error is "Error".
    """
    info = []
    ipv4_count = 0
    ipv6_count = 0
    try:
        for s_family, s_type, s_proto, s_cannoname, s_sockaddr in socket.getaddrinfo(host_name, None):
            if s_family == 2 and s_type == 1:
                ipv4_count += 1
                info.append(["IPv4 (%d)" % ipv4_count, s_sockaddr[0]])
            if s_family == 10 and s_type == 1:
                ipv6_count += 1
                info.append(["IPv6 (%d)" % ipv6_count, s_sockaddr[0]])
    except socket.gaierror, err:
        info.append(["Error", "Unable to resolve %s: %s" % (host_name, err)])

    return info


def send_dns_update(dns_message, dns_server, port, key_name):
    """Send DNS message to server and return response.

    Args:
        Update dns_update
        String dns_server
        String key_name

    Returns:
        String output
    """
    logger = logging.getLogger('binder.helpers')
    try:
        output = dns.query.tcp(dns_message, dns_server, port=port)
    except dns.tsig.PeerBadKey as exc:
        logger.error(exc)
        raise KeyringException("DNS server %s is not configured for TSIG key: %s." %
                               (dns_server, key_name))
    except dns.tsig.PeerBadSignature as exc:
        logger.error(exc)
        raise KeyringException("DNS server %s didn't like the TSIG signature "
                               "we sent. Check key %s for correctness." %
                               (dns_server, key_name))
    logger.debug(output)
    return_code = output.rcode()
    if return_code != dns.rcode.NOERROR:
        raise RecordException('Error when requesting DNS server %s: %s' %
                                (dns_server, dns.rcode.to_text(return_code)))
    return output