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cisagov/pshtt

Scan domains and return data based on HTTPS best practices

cisa-directiveshstshttpsus-federal-government

Pushing HTTPS 🔒

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pshtt ("pushed") is a tool to scan domains for HTTPS best
practices. It saves its results to a CSV (or JSON) file.

pshtt was developed to push organizations — especially large ones
like the US Federal Government 🇺🇸 — to adopt HTTPS across the
enterprise. Federal agencies must comply with
M-15-13, a 2015 memorandum from the White
House Office of Management and Budget, and BOD
18-01, a 2017 directive from the
Department of Homeland Security, which require federal agencies to
enforce HTTPS on their public web services. Much has been done, but
there's more yet to
do.

pshtt is a collaboration between the Cyber and Infrastructure
Security Agency's National Cybersecurity Assessments and Technical
Services (NCATS) team and the General
Service Administration's 18F team, with
contributions from NASA, Lawrence Livermore National Laboratory, and
various non-governmental
organizations.

Getting started

pshtt can be installed as a module, or run directly from the
repository.

Installed as a module

pshtt can be installed directly via pip:

pip install pshtt

It can then be run directly:

pshtt example.com [options]

Running directly

To run the tool locally from the repository, without installing, first
install the requirements:

pip install -r requirements.txt

Then run it as a module via python -m:

python -m pshtt.cli example.com [options]

Usage and examples

pshtt [options] DOMAIN...
pshtt [options] INPUT

pshtt dhs.gov
pshtt --output=homeland.csv --debug dhs.gov us-cert.gov usss.gov
pshtt --sorted current-federal.csv

Note: if INPUT ends with .csv, domains will be read from the first
column of the CSV. CSV output will always be written to disk (unless
--json is specified), defaulting to results.csv.

Options

  -h --help                     Show this message.
  -s --sorted                   Sort output by domain, A-Z.
  -o --output=OUTFILE           Name output file. (Defaults to "results".)
  -j --json                     Get results in JSON. (Defaults to CSV.)
  -m --markdown                 Get results in Markdown. (Defaults to CSV.)
  -d --debug                    Print debug output.
  -u --user-agent=AGENT         Override user agent.
  -t --timeout=TIMEOUT          Override timeout (in seconds).
  -c --cache-third-parties=DIR  Cache third party data, and what directory to cache it in.
  -f --ca-file=PATH             Specify custom CA bundle (PEM format)
Using your own CA bundle

By default, pshtt relies on the root CAs that are trusted in the
Mozilla root
store.
If you work behind a corporate proxy or have your own certificates that
aren't publicly trusted, you can specify your own CA bundle:

pshtt --ca-file=/etc/ssl/ca.pem server.internal-location.gov

What's checked?

A domain is checked on its four endpoints:

  • http://
  • http://www
  • https://
  • https://www

Domain and redirect info

The following values are returned in results.csv:

  • Domain - The domain you're scanning!
  • Base Domain - The base domain of Domain. For example, for a
    Domain of sub.example.com, the Base Domain will be
    example.com. Usually this is the second-level domain, but pshtt
    will download and factor in the Public Suffix
    List     when calculating the base
    domain. (To cache the Public Suffix List, use --suffix-cache as
    documented above.)
  • Canonical URL - One of the four endpoints described above; a
    judgment call based on the observed redirect logic of the domain.
  • Live - The domain is "live" if any endpoint is live.
  • HTTPS Live - The domain is "HTTPS live" if any HTTPS endpoint is
    live.
  • HTTPS Full Connection - The domain is "fully connected" if any
    HTTPS endpoint is fully connected. A "fully connected" HTTPS
    endpoint is one with which pshtt could make a full TLS connection.
  • HTTPS Client Auth Required - A domain requires client
    authentication if any HTTPS endpoint requires it for a full TLS
    connection.
  • Redirect - The domain is a "redirect domain" if at least one
    endpoint is a redirect, and all endpoints are either redirects or
    down.
  • Redirect to - If a domain is a "redirect domain", where does it
    redirect to?

Landing on HTTPS

  • Valid HTTPS - A domain has "valid HTTPS" if it responds on port
    443 at the hostname in its Canonical URL with an unexpired valid
    certificate for the hostname. This can be true even if the Canonical
    URL uses HTTP.
  • HTTPS Publicly Trusted - A domain is "publicly trusted" if its
    canonical endpoint has a publicly trusted certificate.
  • HTTPS Custom Truststore Trusted - A domain is "custom truststore
    trusted" if its canonical endpoint has a certificate that is trusted
    by the custom truststore.
  • Defaults to HTTPS - A domain "defaults to HTTPS" if its canonical
    endpoint uses HTTPS.
  • Downgrades HTTPS - A domain "downgrades HTTPS" if HTTPS is
    supported in some way, but its canonical HTTPS endpoint immediately
    redirects internally to HTTP.
  • Strictly Forces HTTPS - This is different than whether a domain
    "defaults" to HTTPS. A domain "Strictly Forces HTTPS" if one of the
    HTTPS endpoints is "live", and if both HTTP endpoints are either
    down or redirect immediately to any HTTPS URI. An HTTP redirect can
    go to HTTPS on another domain, as long as it's immediate. (A domain
    with an invalid cert can still be enforcing HTTPS.)

Common errors

  • HTTPS Bad Chain - A domain has a bad chain if either HTTPS
    endpoint contains a bad chain.
  • HTTPS Bad Hostname - A domain has a bad hostname if either HTTPS
    endpoint fails hostname validation.
  • HTTPS Expired Cert - A domain has an expired certificate if either
    HTTPS endpoint has an expired certificate.
  • HTTPS Self-Signed Cert - A domain has a self-signed certificate if
    either HTTPS endpoint has a self-signed certificate.
  • HTTPS Probably Missing Intermediate Cert - A domain is "probably
    missing intermediate certificate" if the canonical HTTPS endpoint is
    probably missing an intermediate certificate.

HSTS

  • HSTS - A domain has HTTP Strict Transport Security enabled if its
    canonical HTTPS endpoint has HSTS enabled.
  • HSTS Header - This field provides a domain's HSTS header at its
    canonical endpoint.
  • HSTS Max Age - A domain's HSTS max-age is its canonical endpoint's
    max-age.
  • HSTS Entire Domain - A domain has HSTS enabled for the entire
    domain if its root HTTPS endpoint (not the canonical HTTPS
    endpoint    ) has HSTS enabled and uses the HSTS includeSubDomains
    flag.
  • HSTS Preload Ready - A domain is HSTS "preload ready" if its
    root HTTPS endpoint (not the canonical HTTPS endpoint) has
    HSTS enabled, has a max-age of at least 18 weeks, and uses the
    includeSubDomains and preload flag.
  • HSTS Preload Pending - A domain is "preload pending" when it
    appears in the Chrome preload pending
    list     with the
    include_subdomains flag equal to true. The intent of pshtt is
    to make sure that the user is fully protected, so it only counts
    domains as HSTS preloaded if they are fully HSTS preloaded
    (meaning that all subdomains are included as well).
  • HSTS Preloaded - A domain is HSTS preloaded if its domain name
    appears in the Chrome preload
    list
    with the include_subdomains flag equal to true, regardless of
    what header is present on any endpoint. The intent of pshtt is to
    make sure that the user is fully protected, so it only counts
    domains as HSTS preloaded if they are fully HSTS preloaded
    (meaning that all subdomains are included as well).
  • Base Domain HSTS Preloaded - A domain's base domain is HSTS
    preloaded if its base domain appears in the Chrome preload
    list
    with the include_subdomains flag equal to true. This is subtly
    different from HSTS Entire Domain, which inspects headers on the
    base domain to see if HSTS is set correctly to encompass the entire
    zone.

Scoring

These three fields use the previous results to come to high-level
conclusions about a domain's behavior.

  • Domain Supports HTTPS - A domain 'Supports HTTPS' when it doesn't
    downgrade and has valid HTTPS, or when it doesn't downgrade and has
    a bad chain but not a bad hostname (a bad hostname makes it clear
    the domain isn't actively attempting to support HTTPS, whereas an
    incomplete chain is just a mistake.). Domains with a bad chain
    "support" HTTPS but user-side errors can be expected.
  • Domain Enforces HTTPS - A domain that 'Enforces HTTPS' must
    'Support HTTPS' and default to HTTPS. For websites (where Redirect
    is false) they are allowed to eventually redirect to an
    https:// URI. For "redirect domains" (domains where the Redirect
    value is true) they must immediately redirect clients to an
    https:// URI (even if that URI is on another domain) in order to
    be said to enforce HTTPS.
  • Domain Uses Strong HSTS - A domain 'Uses Strong HSTS' when the
    max-age ≥ 31536000.

General information

  • IP - The IP for the domain.
  • Server Header - The server header from the response for the
    domain.
  • Server Version - The server version, as extracted from the server
    header.
  • HTTPS Cert Chain Length - The certificate chain length for the
    canonical HTTPS endpoint.
  • Notes - A field where free-form notes about the domain can be
    stored.

Uncommon errors

  • Unknown Error - A Boolean value indicating whether or not an
    unexpected exception was encountered when testing the domain. The
    purpose of this field is to flag any odd websites for further
    debugging.

Troubleshooting

DNS blackhole / DNS assist

One issue which can occur when running pshtt, particularly for
home/residential networks, with standard ISPs is the use of "DNS
Assist" features, a.k.a. "DNS Blackholes".

In these environments, you may see inconsistent results from pshtt
owing to the fact that your ISP is attempting to detect a request for
an unknown site without a DNS record and is redirecting you to a
search page for that site. This means that an endpoint which should
resolve as "not-alive", will instead resolve as "live", owing to the
detection of the live search result page.

If you would like to disable this "feature", several ISPs offer the
ability to opt out of this service, and maintain their own
instructions for doing so:

Who uses pshtt?

Acknowledgements

This code was modeled after Ben
Balter's
site-inspector, with
significant guidance from Eric Mill.

Contributing

We welcome contributions! Please see CONTRIBUTING.md for
details.

License

This project is in the worldwide public domain.

This project is in the public domain within the United States, and
copyright and related rights in the work worldwide are waived through
the CC0 1.0 Universal public domain
dedication.

All contributions to this project will be released under the CC0
dedication. By submitting a pull request, you are agreeing to comply
with this waiver of copyright interest.

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Created July 5, 2016
Updated March 9, 2026
cisagov/pshtt | GitHunt