# spf -- expand and report on a given domain's SPF policy The syntax for the Sender Policy Framework (SPF) definition via a DNS TXT record is complex and expansion and inspection of the final ruleset requires possibly multiple DNS lookups. The `spf` utility can be used to easily expand a domain's policy and report on its definition from the command-line. For a longer discussion of SPF, please see this blog post: https://www.netmeister.org/blog/spf.html Sample output of the tool (trimmed for brevity): ``` $ spf github.com github.com: policy: ip4:192.30.252.0/22 include:_netblocks.google.com include:_netblocks2.google.com include:_netblocks3.google.com include:spf.protection.outlook.com include:mail.zendesk.com include:_spf.salesforce.com include:servers.mcsv.net ip4:166.78.69.169 ip4:166.78.69.170 ip4:166.78.71.131 ip4:167.89.101.2 ip4:167.89.101.192/28 ip4:192.254.112.60 ip4:192.254.112.98/31 ip4:192.254.113.10 ip4:192.254.113.101 ip4:192.254.114.176 ip4:62.253.227.114 ~all valid pass: include (7 domains): _netblocks.google.com _netblocks2.google.com _netblocks3.google.com _spf.salesforce.com mail.zendesk.com [...] ip4 (12 CIDRs / 1051 IPs): 166.78.69.169/32 166.78.69.170/32 166.78.71.131/32 [...] _netblocks.google.com: policy: ip4:35.190.247.0/24 ip4:64.233.160.0/19 ip4:66.102.0.0/20 ip4:66.249.80.0/20 ip4:72.14.192.0/18 ip4:74.125.0.0/16 ip4:108.177.8.0/21 ip4:173.194.0.0/16 ip4:209.85.128.0/17 ip4:216.58.192.0/19 ip4:216.239.32.0/19 ~all valid pass: ip4 (11 CIDRs / 215296 IPs): 108.177.8.0/21 173.194.0.0/16 [...] SPF record for domain 'github.com': valid Total counts: Total # of DNS lookups : 8 pass: Total # of 'exists' directives : 1 Total # of 'include' directives : 7 Total # of ip4 directives : 45 Total # of ip4 addresses : 870171 Total # of ip6 directives : 11 Total # of ip6 addresses : 29712752120897178112958136320 All others: softfail ``` Requirements ============ `spf(1)` is written in Perl, and you will need the following modules installed: * Net::DNS * Net::Netmask * Math::BigInt Optional modules: * Data::Dumper * JSON You may be able to install these dependencies via: * NetBSD and other systems using [pkgsrc](https://pkgsrc.org): `sudo pkg_add p5-JSON p5-Net-DNS p5-Net-Netmask p5-Math-BigInt` or `sudo pkgin install p5-JSON p5-Net-DNS p5-Net-Netmask p5-Math-BigInt` * Debian, Ubuntu, and related systems: `sudo apt install libjson-perl libnet-dns-perl libnet-netmask-perl libmath-bigint-perl` * FreeBSD: `sudo pkg install p5-JSON p5-Net-DNS p5-Net-Netmask p5-Math-BigInt` You can also find a [Dockerfile](https://github.com/jschauma/spf/blob/main/misc/Dockerfile) in the 'misc' directory, if that's your jam. Installation ============ To install the command and manual page somewhere convenient, run `make install`; the Makefile defaults to '/usr/local' but you can change the PREFIX: ``` $ make PREFIX=~ install ``` Documentation ============= Please see the manual page for all details: ``` NAME spf - report on the given domain's use of SPF SYNOPSIS spf [-Vhv] [-f format] [-p policy] [-r address] domain DESCRIPTION The spf tool allows you to inspect the Sender Policy Framework DNS records for the given domain. OPTIONS The following options are supported by spf: -V Print version information and exit. -f format output format (json, perl, text). -h Display help and exit. -p policy Expand and report on the given policy. Note: policy needs to be quoted; see EXAMPLES. -r address Explicitly query this resolver. -v Be verbose. Can be specified multiple times. DETAILS The Sender Policy Framework (SPF) defined in RFC7208 specifies the format for the SPF DNS entries a domain may choose to apply. These entries can range from the straight forward to the complex, harboring certain surprises or unintenionally obscuring important information, such as when one domain includes the SPF records of another domain. spf can be used to report on the comprehensive ruleset derived from the DNS record. It does that by counting CIDRs, resolving e.g., MX records, and recursively looking up SPF records of any included domains. EXAMPLES The following examples illustrate common usage of this tool. To report on the SPF records for the domain netmeister.org: spf netmeister.org To query Quad9's public resolver for the same SPF records and report the results in json format: spf -r 2620:fe::fe -j netmeister.org To expand an arbitrary policy from the command-line: spf -p "v=spf1 a:example.com include:example.net -all" EXIT STATUS The spf utility exits 0 on success, and >0 if an error occurs. SEE ALSO dig(1) HISTORY spf was originally written by Jan Schaumann in July 2022, with contributions by Royce Williams, Patrick Proniewski, and Randolf Richardson . BUGS Please file bugs and feature requests by emailing the author. ```