NAME

certwatch — Watch X509 certificates expiration dates

SYNOPSIS

DESCRIPTION

The certwatch utility monitors X509 certificates expiration dates by processing one or more data files containing lists of hostnames with optional port numbers.

It's mainly used to check the expiration date of HTTPS certificates (which is the default target when the port number is not indicated), but the tool is protocol-agnostic and can "talk" to any SNI-aware (Server Name Information) SSL/TLS server (smtps, imaps, ldaps, etc.) without making too much assumptions on the correctness of servers certificates.

The certificates can be saved to a specified directory with the [--savedir|-s] option for further analysis with other tools (such as OpenSSL).

As it's intended to bulk process a lot of certificates, a progress bar is displayed (can be removed with the [--noprogress|-b] option) and the time allowed to get a certificate is limited to a 10 seconds timeout (can be specified otherwise with the [--timeout|-t] option, but is not supported on Windows systems).

In order to avoid doing a Denial of Service attack on servers hosting many certificates, a 1 second delay is waited between each certificate request (can be specified otherwise with the [--delay|-d] option).

The tool results are presented as text tables.

The main one is the list of certificates successfully fetched, ordered by expiration date. This list can be filtered with the [--filter|-f] option to only show certificates expired or expiring within the specified number of days. You can use the [--noaltnames|-a] option in order to stop displaying alternate names contained in certificates, or the [--ip|-i] option to include the IP addresses of servers.

The second table is the sorted list of hostnames / hostports where certificates couldn't be fetched, with our best attempts to identify the reason why.

Two additional tables can be generated with the [--new|-n] option, in order to print the common names and alternate names unmentioned in your input data files.

Finally, for user convenience, all these reports can be generated in a single multi-tabs Excel workbook specified with the [--excel|-e] option.

ENVIRONMENT

The CERTWATCH_DEBUG environment variable can be set to any value to enable debug mode.

FILES

/usr/local/share/certwatch/tests.txt - config file example using the badssl.com Web site for testing live bogus X509 certificates.

The structure of configuration files is as follows:

• Everything after a '#' character is a comment
• Blank lines are allowed
• data lines are either:
  • "hostname hostport"
  • "hostname"
• When hostport is not provided, port 443 (HTTPS) is assumed

EXIT STATUS

The COMMAND utility exits 0 on success, and >0 if an error occurs.

EXAMPLES

The following command will make certwatch process your certificates list in mycertslist.txt, save all certificates in PEM format to mycertsdir, print all possible reports and details to screen and to an Excel workbook named certwatch.out.xlsx, and select or highlight certificates expired or set to expire in the coming 30 days:

# certwatch -in -e certwatch.out.xlsx -s mycertsdir -f 30 mycertslist.txt | tee certwatch.out.txt

Saved certificates can then be viewed with the openssl command like this for a mycert.pem file:

# openssl x509 -inform PEM -in mycert.pem -noout -text | more

SEE ALSO

openssl(1)

STANDARDS

The certwatch utility is not a standard UNIX command.

It tries to follow the PEP 8 style guide for Python code.

PORTABILITY

Tested OK under Windows.

Packaged for FreeBSD as pyXX-pnu-certwatch.

HISTORY

This implementation was made for the PNU project

Both for my own needs and those of my company, I wanted an easy way to monitor thousands of certificates expiration dates.

The initial idea was to use the tool to send an email report of the certificates about to expire, but an Excel report in order to perform all kind of sorts and filtering was quickly necessary...

LICENSE

It is available under the 3-clause BSD license.

AUTHORS

Hubert Tournier

CAVEATS

Using this command through outgoing proxies is untested and we provide no option to set the proxy address. However it should work through reverse proxies on the server side.

SECURITY CONSIDERATIONS

When certificate retrieval is unsuccessful, certwatch will try to diagnose the issue in different ways, one of which involving running the system ping command. This can be an issue if someone happens to place a command with the same name higher in your PATH. But working at the IP layer level, which is needed in order to implement the ICMP protocol, requires root privileges which I see as a bigger risk...