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SPF-tools

Simple tools for keeping the SPF TXT records tidy in order to fight 10 maximum DNS look-ups.

Release notes

2019/10 - new domain spf-tools.eu.org

Domain name spf-tools.eu.org is used for testing now.

2016/11 - new records on output

spf-tools since version spf-tools/spf-tools@f4f51f7 do not output merely ip4 and ip6 records, but also keep original ptr and exists ones.

General Usage

Your original TXT record which causes more than 10 DNS look-ups should be saved as an otherwise unused subdomain TXT record (e.g. spf-orig.spf-tools.eu.org).

Create a configuration file:

cat > ~/.spf-toolsrc <<EOF
DOMAIN=spf-tools.eu.org
ORIG_SPF=spf-orig.spf-tools.eu.org
DESPF_SKIP_DOMAINS=_spf.domain1.com:spf.domain2.org
DNS_TIMEOUT=5
DNS_SERVER=
EOF

Now just call any of the scripts described below.

Tools Description

despf.sh

Usage: despf.sh [OPTION]... [DOMAIN]...
Decompose SPF records of a DOMAIN. Optionaly can
sort and unique them.
DOMAIN may be specified in an environment variable.

Available options:
  -s DOMAIN[:DOMAIN...]      skip domains, i.e. leave include
                             without decomposition
  -t N                       set DNS timeout to N seconds
  -h                         display this help and exit

despf.sh is a tool that resolves all ip4 and ip6 blocks found in any included SPF subdomain. It prints all these blocks sort(1)ed and uniq(1)ed to stdout, one per line. Other output (Getting ...) is on stderr.

Example:

./despf.sh google.com
Getting _spf.google.com
Getting _netblocks.google.com
Getting _netblocks2.google.com
Getting _netblocks3.google.com
ip4:173.194.0.0/16
ip4:74.125.0.0/16
...
ip6:2a00:1450:4000::/36
ip6:2c0f:fb50:4000::/36

The DNS_TIMEOUT configuration variable sets number of seconds for the host -W SECS command (the same as option -t, see help).

mkblocks.sh

mkblocks.sh tool is meant to parse a list of blocks produced by despf.sh and prepare content of TXT records that all fit into one UDP packet, splitting into more TXT records if needed.

One TXT record per line of standard output.

./despf.sh | ./normalize.sh | ./simplify.sh | ./mkblocks.sh

compare.sh

Current SPF records can be verified by running compare.sh. If the TXT records need an update, it will automatically run the other tools to print out or copy into pastebuffer the new TXT records in reverse order.

Best practice is to put those lines into DNS starting with the last one. That's why xsel.sh reverses the input gathered from mkblocks.sh.

The last record to update is root domain's record which just contains an include. It should be always updated as the last one and the prefix alternated between spf and _spf prefixes when changing records, so the records are all consistent until the root one is changed.

xsel.sh

In order to semi-automate the task of updating the records, pipe the output of mkblocks.sh to xsel.sh.

normalize.sh

This script takes care of correct CIDR ranges. At the moment only IPv4.

Example:

$ ./normalize.sh <<EOF
> ip4:207.68.169.173/30
> ip4:207.68.169.175/30
> ip4:65.55.238.129/26
> EOF
ip4:207.68.169.172/30
ip4:207.68.169.172/30
ip4:65.55.238.128/26

simplify.sh

This script takes out individual IPv4 addresses which are already contained in CIDR ranges.

$ ./simplify.sh <<EOF
> ip4:192.168.0.1
> ip4:192.168.0.0/24
> EOF
ip4:192.168.0.0/24

cloudflare.sh

Dependencies: jq, awk, sed, grep

Script to update pre-existing TXT SPF records for a domain according to the input in DNS zone format using CloudFlare's API.

To use this script, file .spf-toolsrc in $HOME directory should contain TOKEN variable definition which is then used to connect to CloudFlare API. The file should also contain DOMAIN and ORIG_SPF variables which stand for the target SPF domain (e.g. spf-tools.eu.org) and original SPF record with includes (e.g. spf-orig.spf-tools.eu.org) in order to use runspftools.sh without modifying the script.

The script is written against v4 of https://api.cloudflare.com/

The only needed permissions for a custom API token are:

• Zone.Zone: Read
• Zone.DNS: Edit

Usage:

./despf.sh | ./normalize.sh | ./simplify.sh | ./iprange.sh | ./cloudflare.sh

route53.sh

Dependencies: jq, aws, awk, sed, grep

 Usage: route53.sh [OPTION]... [HOSTED_ZONE_ID]
  Script to update pre-existing TXT SPF records for
  a domain according to the input in DNS zone format.

  Available options:
    -t TTL                     set Time To Live for DNS records
    -a TXT RECORD              set aditional TXT record to domain (can be used multiple times)

  Default values:
    TTL = 300

Script to update pre-existing TXT SPF records for a domain according to the input in DNS zone format.

The AWS CLI can be configured using ~/.aws/credentials or using environment variables: AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY (find more details in Configuring the AWS CLI documentation.

Example:

./despf.sh | ./simplify.sh | ./mkblocks.sh | \
  ./route53.sh -a "google-site-verification=deadbeef" DEADBEEF

iprange.sh

Extra dependencies: iprange

This script optimizes the IPv4 address block output (similar to, but more than simplify.sh because it can join multiple networks into one bigger).

Usage:

./despf.sh | ./iprange.sh

Example:

$ ./despf.sh cont.spf-tools.eu.org
ip4:13.111.0.0/24
ip4:13.111.1.0/24
ip4:13.111.2.0/24
ip4:13.111.3.0/24
$ ./despf.sh cont.spf-tools.eu.org | ./iprange.sh
ip4:13.111.0.0/22

Putting it all together

./despf.sh | ./normalize.sh | ./simplify.sh | ./iprange.sh \
  | ./mkblocks.sh | ./xsel.sh

Free Ad

As we are successfully using a free eu.org domain, we are proud to spread the word: Free domains: http://www.eu.org/

Links

• https://dmarcian.com/spf-survey/spf.spf-tools.eu.org
• https://dmarcian.com/spf-survey/spf-orig.spf-tools.eu.org
• http://www.kitterman.com/spf/validate.html
• http://serverfault.com/questions/584708
• http://www.openspf.org/SPF_Record_Syntax
• http://tools.ietf.org/html/rfc7208#section-5.5
• http://tools.ietf.org/html/rfc7208#section-14.1
• https://space.dmarcian.com/too-many-dns-lookups/
• https://nic.eu.org/

License

Copyright 2015-2019 spf-tools team (see AUTHORS)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.