spftrace

The spftrace utility is a tool for executing, analysing, and displaying SPF queries. SPF is specified in RFC 7208.

This utility executes an SPF query with IP address and domain and shows the result graphically as an evaluation tree.

This utility uses the viaspf library to execute SPF queries. The viaspf library can trace a query as it executes and makes the trace available as structured data in its API. spftrace then analyses this data and displays it.

Thanks to the underlying execution engine being a real, RFC-conformant SPF implementation, spftrace handles all SPF policies correctly. Less well-known features of SPF such as macros, dual CIDR prefix lengths, exp modifiers, or the void lookup limit are all evaluated according to spec. Internationalised email domains are equally supported.

Installation

The spftrace utility is a Rust program; install it with Cargo as usual. For example, use the following command to install the latest version published on crates.io:

cargo install --locked spftrace

The minimum supported Rust version is 1.65.0.

Usage

Pass a sender identity (an email address or a domain name) and an IP address to spftrace.

Use the unspecified IP address 0.0.0.0 (IPv4) or :: (IPv6) to display the full evaluation tree of some SPF-enabled domain.

spftrace example.com 0.0.0.0

example.com
│   "v=spf1 mx include:spf.example.com ~all"
├── mx → example.com (lookups: 1/10, nested: 2/10)
│   ├── mx1.example.com
│   │   ├── 216.58.192.0
│   │   ├── 65.55.52.224
│   │   └── 207.46.116.128
│   └── mx2.example.com
│       └── 65.55.238.129
│   not-match
├── include:spf.example.com → spf.example.com (lookups: 2/10)
│   spf.example.com
│   │   "v=spf1 ip4:207.46.4.128/25 ip4:65.55.174.0/24 ip6:2c0f:fb50:4000::/36
│   │    ip6:2001:4860:4000::/36 ~all"
│   ├── ip4:207.46.4.128/25 not-match
│   ├── ip4:65.55.174.0/24 not-match
│   ├── ip6:2c0f:fb50:4000::/36 not-match
│   ├── ip6:2001:4860:4000::/36 not-match
│   └── all match result=softfail
│   not-match
└── all match result=softfail
softfail

The command shown above can be abbreviated to spftrace example.com: When no IP address is specified, 0.0.0.0 is assumed.

For details, refer to the included manual page spftrace(1). (You can view the manual page without installing by passing the file path to man: man ./spftrace.1)

Development

Unit tests are in separate module tests. Specify a test name and pass the --test-threads 1 test binary option to run and visually check some test (Cargo is unable to capture stdout, so limiting the number of threads at least avoids interleaved output).

For example:

cargo test ptr -- --test-threads 1

Licence

Copyright © 2022–2023 David Bürgin

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.