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certinfo -- Examine the health status of your TLS certificates

This small tool has one purpose: To tell you when the TLS certificates of your websites will expire. If you have dozens of projects with individual certificates, you might find this helpful.

All it does is to try and open a TCP connection to a given domain, using timeout, port and protocol as defined. If successful, it will show you the number of days until certificate expiration in one line (per domain).

Installation

If missing, first install Go on your computer. On Ubuntu or Debian, for example, use:

sudo apt install golang-go

Then check out the source code:

git clone [email protected]:C3S/certinfo.git
cd certinfo
# fetch dependencies
go get .

certinfo depends on these additional modules:

  • color for colored output
  • cobra for providing commands and flags
  • viper for handling configuration files

You should now already be able to run it:

go run .

For permanent use, you should build it and run the binary:

go build
./certinfo

It's a single binary file, you can link or copy it to a directory in your PATH environment variable to be able to call it from anywhere.

Usage

There's two feedback variants: The command expires will print the expiration date, whereas bestbefore also compares that date to a given threshold, defaulting to 14 days. That is, if the certificate is still valid beyond the threshold, you'll get a green ok, if it will expire before that you'll be told please renew in orange, and if the certificate is already expired, you'll get a red alert.

This can be done in two modes: expires and bestbefore expect a single domain as additional argument, so they do one check exactly. The commands hosts_expire and hosts_bestbefore, however, fetch domain names and HTTPS ports from a YAML configuration file. This can either be a file called config.yaml in the current directory or ~/.config/certinfo/, or a file specified via the global --config flag. See the config.yaml.example file, it should explain itself. In this mode, both IPv4 and IPv6 will be tried for each domain.

Partly depending on the feedback variant, you can adjust the IP --protocol (4 or 6, the default), the TCP --port (default is 443), the number of --days used by bestbefore/hosts_bestbefore (default is 14), and the --timeout for dials in seconds (default is 5).

Connection errors are silently ignored by default. To see them, use the --errors flag.

Examples

# replace this with one of your domains
foo@bar:~$ MYDOMAIN="www.example.com"

# check the expiration date of your domain (IPv6, port 443)
foo@bar:~$ certinfo expires "${MYDOMAIN}"
expires: 02.10.2023 (IPv6)

# alternatively, see if the certificate is good for at least another 14 days
foo@bar:~$ certinfo bestbefore "${MYDOMAIN}"
will expire in 76 days (IPv6)  -- ok!

# now check for IPv4 and 7 days
foo@bar:~$ certinfo bestbefore "${MYDOMAIN}" --protocol 4 --days 7
expires in 6 days (IPv4)  -- please renew!

# flags can be shortened; since -p is already used for --port, the
# IP version was shortened to -i
foo@bar:~$ certinfo bestbefore "${MYDOMAIN}" -i 4 -d 7
expires in 6 days (IPv4)  -- please renew!

For the next examples, prepare a configuration file with some of your subdomains similar to this one:

hosts:
    - example:
        url: www.example.com
        port: 443
    - another:
        url: another.example.com
        port: 443

It can then be used with hosts_expire and hosts_bestbefore:

# if you save the config to ~/.config/certinfo/config.yaml or the current
# directory, it will be found automatically
foo@bar:~$ certinfo hosts_expire
www.example.com            expires: 02.10.2023 (IPv4)
www.example.com            expires: 02.10.2023 (IPv6)
another.example.com        expires: 02.10.2023 (IPv4)
another.example.com        expires: 19.05.2023 (IPv6)

# the same with hosts_bestbefore, but this time provide the hosts configuration
# via the command line flag
foo@bar:~$ certinfo --config ~/my_config.yaml hosts_bestbefore
www.example.com            (IPv4): expires 02.10.2023, in 76 days     -- ok!
www.example.com            (IPv6): expires 02.10.2023, in 76 days     -- ok!
another.example.com        (IPv4): expires 02.10.2023, in 76 days     -- ok!
another.example.com        (IPv6): expired 19.05.2023, -59 days ago   -- red alert!

Contributing

To ask for help, report bugs, suggest feature improvements, or discuss the global development, please use the issue tracker.

Branches

Please note that all development happens in the develop branch. Pull requests against the main branch will be rejected, as it is reserved for the current stable release.

Licence

Copyright 2023 m.eik michalke [email protected].

These scripts are free software: you can redistribute them and/or modify them 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.

These scripts are distributed in the hope that they 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 these scripts. If not, see https://www.gnu.org/licenses/.