content/articles/site-backend.md: populate most of the content

1 files changed, 561 insertions, 77 deletions

diff --git a/content/articles/site-backend.md b/content/articles/site-backend.md
index 6bfa592..5fb750b 100644
--- a/content/articles/site-backend.md
+++ b/content/articles/site-backend.md
@@ -3,7 +3,7 @@ slug: "site-backend"
 title: "Site Backend"
 
 # date (optional for articles)
-date: "2023-09-08T05:07:47-04:00"
+date: "2024-05-31T03:57:18-04:00"
 
 # draft articles are not visible on live site
 draft: true
@@ -13,21 +13,40 @@ show: true
 
 # uncomment to show table of contents
 toc: true
+
+pics:
+  editing:
+    css: "image"
+    tip: "Editing this article with Vim and Firefox."
+    sources:
+      - "/files/articles/site-backend/0-editing-1024.webp"
+      - src: "/files/articles/site-backend/0-editing-1024.png"
+        width: 1024
+        height: 640
+  ssl-labs-report:
+    css: "image"
+    tip: "SSL Labs SSL Test results for this site."
+    sources:
+      - "/files/articles/site-backend/1-ssl-labs-20240530-1024.webp"
+      - src: "/files/articles/site-backend/1-ssl-labs-20240530-1024.png"
+        width: 1024
+        height: 525
+  securityheaders-report:
+    css: "image"
+    tip: "Security headers report for this site from securityheaders.com"
+    sources:
+      - "/files/articles/site-backend/2-securityheaders-1024.webp"
+      - src: "/files/articles/site-backend/2-securityheaders-1024.png"
+        width: 1024
+        height: 320
 ---
 ## Overview
 
-This site is statically generated by [Hugo][] and themed with a
-stripped-down version of [Bulma][].  Both have been heavily customized;
-see the [Configuration](#configuration) section for details.
-
-The goals of this setup are:
+Site content is managed as [Markdown][] files stored in a [Git][]
+repository.  The theme is a modified version of [Bulma][].  The site is
+statically generated by [Hugo][].
 
-- Size
-- Speed
-- Security
-- Mobile Support
-- Accessibility
-- Simplicity (for me)
+[{{< pe-figure "editing" >}}][editing-this-article]
 
 ## History
 
@@ -36,72 +55,375 @@ written by me.  In 2019 I resurrected the site after a several year
 hiatus and migrated the site from the custom [PHP][] backend to
 [Jekyll][].  In 2021 I switched from [Jekyll][] to [Hugo][].
 
+## Goals
+
+The goals of this site backend are:
+
+- Small
+- Fast
+- Secure
+- Mobile-friendly
+- Accessible
+- Simple (for me)
+
+Static generation neatly addresses the first three goals:
+
+- The site is small because the [Hugo][] can be configured to
+  aggressively pack and minify content and assets.  Images are
+  also compressed and served in multiple formats (see [Hugo
+  Configuration](#hugo-configurationi "Hugo Configuration") and [Images](#images
+  "Images")).
+- The site is fast because web servers can serve static content
+  extremely quickly, and because static content can be cached.  Caching
+  and compression are enabled in [Apache][] (see [Apache
+  Configuration](#apache-configuration "Apache Configuration")).
+- The site is secure because the content is static; there is no
+  web-accessible endpoint which can upload files or modify content.
+  Additional security measures are discussed in several of the following
+  sections.
+
+Explanations of how I keep the site mobile-friendly and accessible are
+available in the [HTML](#html "HTML") and [Hugo
+Configuration](#hugo-configuration "Hugo Configuration") sections below.
+
+**TODO:** discuss simplicity
+
 ## Content
 
 ### HTML
 
-I create and edit site content with [vim][] in [Markdown][] format and
+I create and edit site content with [Vim][] in [Markdown][] format and
 preview the results locally with `hugo serve -D ...`.  Articles and blog
 posts are saved as drafts and committed to the [Git][] repository so I
 can work on them as time permits.
 
-The content and site layout is designed with accessibility and mobile in
-mind.  This means:
+The content and layout is designed to be accessible and mobile-friendly:
 
-- links, and table components have `title`, `aria-label` attributes
-- images have captions, fallback formats, `title` and `alt` attributes.
+- links and table components have `title` and `aria-label` attributes
+- images have captions, fallback formats, and `title` and `alt` attributes
 - images scale gracefully to thumbnails on mobile
-- the site honors users' [color scheme preference][] and has a manual
-  theme override
-- The page menu bar collapes to a hamburger menu on mobile.
+- the site supports [dark mode][], checks the [color scheme
+  preference][prefers-color-scheme] to determine the default theme,
+  and has a [manual theme switcher][post-theme-switcher]
+- The menu bar collapes to a hamburger menu on mobile.
 
 ### Images
 
 Images are created as follows:
 
 - Mathematical content is created using [Mathy][], saved as [SVG][],
-  and minified using [minify][].
-- Charts are created with [Matplotlib][], saved as [SVG][], and minified
-  using [minify][].
-- Lossless images (e.g. screenshots) are scaled and cropped with
-  [GraphicsMagick][] and served as a lossless [WebP][]
-  with a [PNG][] fallback.  The fallback is compressed with
-  [pngquant][].
-- Lossy images are [GraphicsMagick][] and served as a lossy [WebP][]
-  with a [JPEG][] fallback.
+  minified using [minify][], and served cached and compressed by [Apache][].
+- Charts are created with [Matplotlib][], saved as [SVG][], minified
+  with [minify][], and served cached and compressed by [Apache][]
+  Example: [This Python script][bench-chart] was used to generate the
+  bar charts in [this blog post][post-fips203ipd].
+- Lossless raster images (e.g. screenshots) are scaled and cropped with
+  [GraphicsMagick][] and served as a lossless [WebP][] with a [PNG][]
+  fallback compressed by [pngquant][].
+- Lossy raster images (e.g. pictures) are scaled and cropped with
+  [GraphicsMagick][] and served as a lossy [WebP][] with a [JPEG][]
+  fallback.
+
+Other notes:
+
+- The animated site logo is an [SVG][] generated by [this Ruby script][gen-logo.rb].
 - Menubar icons are borrowed from [Bootstrap Icons][].
-- The animated site logo is generated by [this Ruby script][logo-script].
+- I reviewed several [PNG][] compressors in [this post][post-png-compressors].
 
 ### JavaScript
 
-There is almost no [JavaScript][], by design.  The one script that is
-used is minimal, [deferred][], used for two things:
-
-1. to handle the [theme toggle][].
-2. to toggle the mobile site menu.
+This site has almost no [JavaScript][], by design.  The [JavaScript][]
+that is used is minimal, [modern][es2015], [deferred][], and only used
+for the [theme switcher][post-theme-switcher] and burger menu.
+
+Below is the unminified `script.js` for this site with some notes
+removed.  It is 777 bytes minified and 586 bytes minified and
+compressed:
+
+```js
+'use strict';
+
+//
+// script.js - script which handles:
+//
+// - set theme
+// - theme switcher and burger menu event handlers
+//
+
+const D = document,
+      C = D.body.parentElement.classList,
+      L = localStorage,
+      M = window.matchMedia,
+      on = (el, id, fn) => el.addEventListener(id, fn);
+
+// use theme if set, otherwise fall back to browser preference
+if (L && L.theme && L.theme === 'dark') {
+  C.add('dark'); // theme set to "dark"
+} else if ((!L || !L.theme) && M && M('(prefers-color-scheme: dark)').matches) {
+  C.add('dark'); // prefers dark color scheme
+}
+
+document.addEventListener('DOMContentLoaded', () => {
+  // theme toggle event handler
+  on(D.querySelector('.navbar-item[data-id="theme"]'), 'click', (e) => {
+    e.preventDefault(); // stop event
+    L.theme = C.toggle('dark') ? 'dark' : 'light'; // toggle
+  });
+
+  // iterate through burgers, bind to click events
+  D.querySelectorAll('.navbar-burger').forEach(e => on(e, 'click', () => {
+    // then toggle is-active on burger and menu
+    [e, D.getElementById(e.dataset.target)].forEach(
+      e => e.classList.toggle('is-active')
+    )
+  }));
+});
+```
+[Download][script.js]
 
 ## Deployment
 
 Once I am ready to apply any outstanding changes to the public web site,
 I push the outstanding commits to a remote [Git][] repository. This
-triggers a [`post-receive` hook][], which sends an authenticated `POST`
-request to a [web hook][] exposed on a TLS endpoint on the web server.
+triggers a [`post-receive` Git hook][post-receive], which sends an
+[HMAC][]-authenticated `POST` request to a [web hook][] endpoint on the
+web server.
 
-The [web hook][] runs a [deployment script (`deploy.rb`)][] which does
-the following:
+The [web hook][] verifies the [HMAC][] and then runs [a deployment
+script][deploy.rb] which does the following:
 
-1. Verifies the authenticated timestamp (to prevent replay attacks).
+1. Verifies the authenticated timestamp (to prevent [replay attacks][]).
 2. Clones the upstream repository.
-3. Executes [Hugo][] (`hugo --minify -d ...`) to build the site minified
-   in a unique output directory.
-4. Updates the `htdocs` symlink for the public web site to point at
-   the output directory from the previous step.
+3. Executes [Hugo][] (`hugo --minify -d ...`) to build the site in an
+   isolated output directory.
+4. Updates the `htdocs` symlink for the public-facing web site to point
+   at the output directory from the previous step.
 5. Removes any stale builds.
 
 ## Configuration
 
-This section discusses the configuration for [Hugo][], [Bulma][] and
-[Apache][].
+This section discusses the configuration for [Apache][], [Bulma][],
+[Hugo][], and [Webhook][].
+
+### Apache Configuration
+
+This section disusses the [Apache][] configuration for this site.  I
+have broken this section into three sub-sections to make them easier to
+digest.
+
+The [Apache][] configuration relies on the following modules:
+
+- [mod\_deflate][mod-deflate] (see note below)
+- [mod\_http2][mod-http2]
+- [mod\_macro][mod-macro]
+- [mod\_proxy][mod-proxy]
+- [mod\_rewrite][mod-rewrite]
+
+Note: It is safe for this site to enable [mod\_deflate][mod-deflate]
+because it does not use [cookies][] and is not vulnerable to [BREACH][].
+and does not use [cookies][].
+
+#### Virtual Host Configuration
+
+The [Apache][] virtual host configuration is modified as follows:
+
+- Unconditionally redirect from [HTTP][] to [HTTPS][]
+- Unconditionally redirect to strip the `www.` hostname prefix
+- Enable [HTTP/2][]
+- Set security headers (discussed in [Security Headers](#security-headers))
+- Enable aggressive caching of image, script, and style assets
+
+Below is the [Apache][] virtual host configuration for this site with
+extraneous comments and configuration for logging, [TLS][], and legacy
+redirects removed:
+
+```apache
+# unconditionally redirect to https://pablotron.org
+<VirtualHost *:80>
+  RewriteEngine On
+  RewriteRule ^/(.*)$ https://pablotron.org/$1 [R,L]
+</VirtualHost>
+
+<VirtualHost *:443>
+  # strip "www." prefix and enable mod_deflate
+  Use STRIP_WWW https://pablotron.org
+  Use MOD_DEFLATE
+
+  # enable http2
+  Protocols h2 http/1.1
+
+  # set restrictive content security policy
+  Header append "Content-Security-Policy" "default-src 'self'; img-src 'self' https://pmdn.org"
+
+  # set remaining security headers
+  Header append "Strict-Transport-Security" "max-age=31536000"
+  Header append "X-Frame-Options" "SAMEORIGIN"
+  Header append "X-Content-Type-Options" "nosniff"
+  Header append "Cross-Origin-Opener-Policy" "same-origin"
+  Header append "Cross-Origin-Resource-Policy" "same-origin"
+  Header append "Access-Control-Allow-Origin" "https://pablotron.org"
+  Header append "Referrer-Policy" "strict-origin-when-cross-origin"
+
+  # set permissions policy
+  Header append "Permissions-Policy" "camera=(), geolocation=(), gyroscope=(), magnetometer=(), microphone=(), midi=(), payment=(), usb=()"
+
+  # POST needed for /hooks
+  Header append "Access-Control-Allow-Methods" "POST, GET, HEAD, OPTIONS"
+
+  # cache images, stylesheets, and javascript for 1 year
+  <FilesMatch "\.(ico|jpg|jpeg|png|gif|webp|svg|js|json|css)$">
+    Header set Cache-Control "max-age=31536000, public"
+  </FilesMatch>
+
+  # expose webhook
+  <Location /hooks/>
+    ProxyPass "http://localhost:9000/"
+    ProxyPassReverse "http://localhost:9000/"
+  </Location>
+</VirtualHost>
+```
+
+[Download][apache-vhost.conf]
+
+#### Security Headers
+
+This site uses a strict [Content-Security-Policy][] header; it rejects
+links to all external assets with one exception: references to images
+hosted on <https://pmdn.org/> are allowed.
+
+The trickiest part of restricting [Content-Security-Policy][] was
+`style-src`; many content generation tools (including the [Markdown][]
+table generator in [Hugo][]) break without `style-src 'unsafe-inline'`
+(e.g., the ability to emit arbitrary `style` attributes).
+
+In order to work around the `style-src` issues I ended up [reconfiguring
+the Hugo syntax highlighter](#hugo-configuration) and writing [a custom
+Hugo table shortcode][hugo-shortcode-table] which only emits `class`
+attributes for inline styling.
+
+The journey to a strict [Content-Security-Policy][] is documented in
+this series of blog posts from October 2021:
+
+- [Hugo/Content-Security-Policy Impedance Mismatch (October 19, 2021)][post-headers-1]
+- [TLS and Header Fixes (October 21, 2021)][post-headers-2]
+- [The Nuclear Option (No More unsafe-inline) (October 25, 2021)][post-headers-3]
+
+The remaining security headers are explained in the following articles:
+
+- [Security headers quick reference][security-headers-quick-ref]
+- [Goodby Feature Policy and hello Permissions Policy!][permissions-policy]
+- [Permissions Policy Explainer][]
+- [Referrer-Policy][]
+
+The security headers on this site earn an A+ rating from
+[securityheaders.com][]:
+
+[{{< pe-figure "securityheaders-report" >}}][securityheaders-report]
+
+#### TLS Configuration
+
+The certificate for this site is issued by [Let's Encrypt][] and managed
+automatically by [certbot][] with the [certbot-dns-linode][] plugin.
+
+The [Apache][] [TLS][] configuration is based on the intermediate
+settings from the [Mozilla SSL Configuration Generator][ssl-config].  In
+particular, only [TLS 1.2][] and [TLS 1.3][] are enabled, and the
+insecure ciphers from [TLS 1.2][] have been disabled.
+
+```apache
+# explicit list of cipher suites (from ssl-config.mozilla.org)
+SSLCipherSuite ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384
+
+# use server priorities for cipher algorithm choice
+SSLHonorCipherOrder on
+
+# protocols to enable (only TLS 1.2 and TLS 1.3)
+SSLProtocol all -SSLv3 -TLSv1 -TLSv1.1
+```
+
+[Download][apache-tls.conf]
+
+This [TLS][] configuration earns an A+ result from the [SSL Labs SSL
+Test][ssl-labs-ssl-test]:
+
+[{{< pe-figure "ssl-labs-report" >}}][ssl-labs-report]
+
+### Bulma Configuration
+
+The site [CSS][] based on the [Bulma][] with the following
+modifications:
+
+1. All unused components removed
+2. monokai style for [Chroma][] added
+3. Styles for navbar icon highlighting and table captions added
+4. dark mode styles added
+
+Here is the [SASS][]:
+
+```sass
+// style.sass: based on bulma-0.9.3/sass/bulma.sass with the following
+// changes:
+//
+// 1. all unused components removed
+// 2. monokai style for chroma added
+// 3. styles for navbar icon highlighting and table captions added
+// 4. dark mode styles added
+@charset "utf-8"
+
+// import chroma style
+//
+// generated with the following command:
+//
+//   cd themes/hugo-pt2021/assets
+//   hugo gen chromaclasses --style=monokai > chroma.css
+//
+@import "chroma"
+
+@import "bulma-0.9.3/sass/utilities/_all"
+@import "bulma-0.9.3/sass/base/_all"
+
+// elements
+@import "bulma-0.9.3/sass/elements/button"
+@import "bulma-0.9.3/sass/elements/container"
+@import "bulma-0.9.3/sass/elements/content"
+@import "bulma-0.9.3/sass/elements/image"
+@import "bulma-0.9.3/sass/elements/table"
+@import "bulma-0.9.3/sass/elements/title"
+@import "bulma-0.9.3/sass/elements/other"
+
+// components
+@import "bulma-0.9.3/sass/components/media"
+@import "bulma-0.9.3/sass/components/navbar"
+
+// grid (reenabled, used for images)
+@import "bulma-0.9.3/sass/grid/_all"
+
+// helpers
+@import "bulma-0.9.3/sass/helpers/_all"
+
+// layout
+@import "bulma-0.9.3/sass/layout/section"
+@import "bulma-0.9.3/sass/layout/footer"
+
+// dim navbar icons by default
+.navbar-item .menu-icon
+  opacity: 60%
+
+// highlight icons on hover
+.navbar-item:hover .menu-icon
+  opacity: 100%
+
+// table captions below tables
+table.table
+  caption-side: bottom
+
+// dark mode (2024-05-27)
+@import "dark"
+```
+[Download][style.sass.txt]
+
+With these changes the generated [CSS][] is 137 kB minified and 16 kB
+minified and compressed.
 
 ### Hugo Configuration
 
@@ -120,37 +442,56 @@ enhancement][].
 
 The generated [HTML][] has been modified to:
 
-- add support `go-import` 
+**TODO:**
+
+- add support `go-import`
 - add a [Mastodon][] `<link rel='me' ...>` tag.
-- remove all unnecessary tags 
+- remove all unnecessary tags
 - to combine and [minify][] and [JavaScript][] and [CSS][] assets.
 - to add `integrity` attributes to `<link>` and `<script>` tags.
 
-### Bulma Configuration
-
-**TODO:**
-
-- bulma modified to remove all unnecessary components
-  - show `style.css`
-- added chroma styles
-- added dark mode
-
-### Apache Configuration
-
-**TODO:**
-
-- security headers (see next section)
-- `static/files/articles/site-backend/pablotron.org.conf.txt` (config w/ garbage removed)
-- mod deflate
-- mod rewrite for old links
-- aggressive caching
-- http2
-- letsencrypt
-- tls config (1.2 or newer, remove garbage algos)
-
-## HTTP Security Headers
+### Webhook Configuration
+
+[webhook][] configuration with [HMAC][] key removed:
+
+```json
+[{
+  "id": "deploy-pablotron-org",
+  "execute-command": "/data/www/pablotron.org/git/bin/hook/deploy.rb",
+
+  "pass-arguments-to-command": [{
+    "source": "payload",
+    "name": "time"
+  }],
+
+  "pass-environment-to-command": [{
+    "source": "string",
+    "envname": "DEPLOY_HTDOCS_PATH",
+    "name": "/data/www/pablotron.org/builds/current"
+  }, {
+    "source": "string",
+    "envname": "DEPLOY_REPO_DIR",
+    "name": "/data/www/pablotron.org/git"
+  }, {
+    "source": "string",
+    "envname": "DEPLOY_BUILDS_DIR",
+    "name": "/data/www/pablotron.org/builds"
+  }],
+
+  "trigger-rule": {
+    "match": {
+      "type": "payload-hmac-sha256",
+      "secret": "(omitted)",
+      "parameter": {
+        "source": "header",
+        "name": "X-Hub-Signature"
+      }
+    }
+  }
+}]
+```
 
-TODO
+[Download][webhook.conf]
 
 ## Validation
 
@@ -165,14 +506,157 @@ I periodically verify the following manually:
 
 ## Other
 
-- content served minified, cached, and compressed.
-(more stuff from `TODO.md`)
+**TODO:**
 
-```apache
-# TODO: include annotated files/articles/site-backend/pablotron.org.conf.txt
-```
+- wireguard
+- private ssh, private git
+- (more stuff from `TODO.md`)
 
 [hugo]: https://gohugo.io/
   "Hugo static site generator."
 [bulma]: https://bulma.io/
   "Bulma minimal CSS framework."
+[mathy]: https://mathy.pmdn.org/
+  "Online LaTeX editor."
+[svg]: https://en.wikipedia.org/wiki/SVG
+  "Scalable Vector Graphics vector image format (SVG)"
+[png]: https://en.wikipedia.org/wiki/PNG
+  "Portable Network Graphics lossless raster image format (PNG)"
+[webp]: https://en.wikipedia.org/wiki/WebP
+  "WebP raster image format"
+[vim]: https://www.vim.org/
+  "vim text editor"
+[markdown]: https://en.wikipedia.org/wiki/Markdown
+  "Markdown lightweight markup language"
+[matplotlib]: https://matplotlib.org/
+  "Python charting library"
+[pngquant]: https://pngquant.org/
+  "Command-line tool for \"lossy\" compression of PNG images"
+[graphicsmagick]: http://www.graphicsmagick.org/
+  "Command-line swiss army knife tool for image processing"
+[php]: https://www.php.net/
+  "PHP programming language"
+[bootstrap icons]: https://icons.getbootstrap.com/
+  "Free high quality open source icon library"
+[jekyll]: https://jekyllrb.com/
+  "Jekyll static site generator"
+[git]: https://git-scm.com/
+  "Free and open source distributed version control"
+[javascript]: https://en.wikipedia.org/wiki/JavaScript
+  "JavaScript scripting language"
+[minify]: https://github.com/tdewolff/minify
+  "Minifier Go library and command-line tool"
+[mastodon]: https://en.wikipedia.org/wiki/Mastodon_(social_network)
+  "Mastodon distributed social network"
+[css]: https://en.wikipedia.org/wiki/CSS
+  "Cascading Style Sheets"
+[editing-this-article]: /files/articles/site-backend/0-editing.png
+  "Editing this article with Vim and Firefox"
+[jpeg]: https://en.wikipedia.org/wiki/JPEG
+  "Joint Photographic Experts Group (JPEG) lossy raster image format"
+[es2015]: https://en.wikipedia.org/wiki/ECMAScript_version_history#6th_Edition_%E2%80%93_ECMAScript_2015
+  "Modern JavaScript"
+[post-theme-switcher]: {{< relref "posts/2024-05-27-site-updates-dark-mode-and-about-pics" >}}
+  "Blog post about dark mode and theme switcher"
+[prefers-color-scheme]: https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme
+  "prefers-color-scheme media query"
+[dark mode]: https://en.wikipedia.org/wiki/Light-on-dark_color_scheme
+  "Dark mode"
+[webhook]: https://github.com/adnanh/webhook
+  "Lightweight webhook server to run shell commands"
+[webhook.conf]: /files/articles/site-backend/webhook.conf.txt
+  "Download webhook.conf"
+[hmac]: https://en.wikipedia.org/wiki/HMAC
+  "Hash-based message authentication code (HMAC)"
+[apache]: https://apache.org/
+  "Apache web server"
+[apache-vhost.conf]: /files/articles/site-backend/pablotron.org.conf.txt
+  "Download Apache virtual host configuration"
+[apache-tls.conf]: /files/articles/site-backend/tls.conf.txt
+  "Download Apache TLS configuration"
+[web hook]: https://en.wikipedia.org/wiki/Webhook
+  "HTTP-accessible callback"
+[deferred]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#defer
+  "defer attribute of script tag"
+[replay attacks]: https://en.wikipedia.org/wiki/Replay_attack
+  "Network attack where a valid data transmission is repeated or delayed."
+[tls]: https://en.wikipedia.org/wiki/Transport_Layer_Security
+  "Transport Layer Security"
+[post-receive]: https://git-scm.com/docs/githooks#post-receive
+  "Git hook triggered on a remote repository after a push operation"
+[deploy.rb]: https://git.pablotron.org/sites/pablotron.org/plain/bin/hook/deploy.rb
+  "Deployment script invoked as a web hook."
+[gen-logo.rb]: https://git.pablotron.org/sites/pablotron.org/plain/bin/logo-0/gen-logo.rb
+  "Ruby script to generate animated SVG logo."
+[post-png-compressors]: {{< relref "posts/2023-06-02-end-of-may-miscellany" >}}
+  "Blog post with a review of several PNG compressors"
+[bench-chart]: https://github.com/pablotron/fips203ipd/tree/main/scripts/bench-chart
+  "Scripts to build and run fips203ipd bench utility with several combinations of backend and compiler, generate a summary CSV, and render a bar chart as an SVG."
+[post-fips203ipd]: {{< relref "posts/2024-05-15-c11-fips203ipd-v0.6.md" >}}
+  "Blog post about release of fips203ipd v0.6."
+[script.js]: /files/articles/site-backend/script.js.txt
+  "Unminified JavaScript for this site with some comments removed."
+[http]: https://en.wikipedia.org/wiki/HTTP
+  "Hypertext Transfer Protocol (HTTP)"
+[https]: https://en.wikipedia.org/wiki/HTTPS
+  "Hypertext Transfer Protocol Secure (HTTPS)"
+[http/2]: https://en.wikipedia.org/wiki/HTTP/2
+  "Hypertext Transfer Protocol, version 2 (HTTP/2)"
+[post-headers-1]: {{< relref "posts/2021-10-19-hugo-csp-impedance-mismatch.md" >}}
+  "Hugo/Content-Security-Policy Impedance Mismatch - October 19, 2021"
+[post-headers-2]: {{< relref "posts/2021-10-21-tls-and-header-fixes.md" >}}
+  "TLS and Header Fixes - October 21, 2021"
+[post-headers-3]: {{< relref "posts/2021-10-25-the-nuclear-option-no-more-unsafe-inline.md" >}}
+  "The Nuclear Option (No More unsafe-inline) - October 25, 2021"
+[mod-http2]: https://httpd.apache.org/docs/current/mod/mod_http2.html
+  "Apache module which provides HTTP/2 support."
+[mod-proxy]: https://httpd.apache.org/docs/current/mod/mod_proxy.html
+  "Apache module which provides proxy and reverse proxy support."
+[mod-rewrite]: https://httpd.apache.org/docs/current/mod/mod_rewrite.html
+  "Apache module which provides rules-based rewriting and redirecting engine."
+[mod-macro]: https://httpd.apache.org/docs/current/mod/mod_macro.html
+  "Apache module which provides macros within configuration files."
+[mod-deflate]: https://httpd.apache.org/docs/current/mod/mod_deflate.html
+  "Apache module which provides DEFLATE output compression."
+[ssl-config]: https://ssl-config.mozilla.org/
+  "Mozilla SSL Configuration Generator"
+[tls 1.2]: https://en.wikipedia.org/wiki/Transport_Layer_Security#TLS_1.2
+  "TLS version 1.2"
+[tls 1.3]: https://en.wikipedia.org/wiki/Transport_Layer_Security#TLS_1.3
+  "TLS version 1.3"
+[ssl-labs-report]: https://www.ssllabs.com/ssltest/analyze.html?d=pablotron.org&hideResults=on
+  "SSL Labs SSL Test results for this site."
+[ssl-labs-ssl-test]: https://www.ssllabs.com/ssltest/
+  "SSL Labs SSL Test"
+[security-headers-quick-ref]: https://web.dev/articles/security-headers
+  "Security headers quick ref"
+[permissions-policy]: https://scotthelme.co.uk/goodbye-feature-policy-and-hello-permissions-policy/
+  "Goodbye Feature Policy and hello Permissions Policy!"
+[permissions policy explainer]: https://github.com/w3c/webappsec-permissions-policy/blob/main/permissions-policy-explainer.md
+  "Permissions Policy Explainer"
+[referrer-policy]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy#strict-origin-when-cross-origin
+  "Documentation for \"Referrer-Policy: strict-origin-when-cross-origin\""
+[content-security-policy]: https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP
+  "Content-Security-Policy header"
+[hugo-shortcode-table]: https://github.com/pablotron/hugo-shortcode-table
+  "Powerful Hugo table shortcode which emits HTML using CSS classes rather than inline style attributes."
+[breach]: https://en.wikipedia.org/wiki/BREACH
+  "Browser Reconnaissance and Exfiltration via Adaptive Compression of Hypertext (BREACH)"
+[cookies]: https://en.wikipedia.org/wiki/HTTP_cookie
+  "Small blocks of data created by a web server when a user is browsing a web site."
+[let's encrypt]: https://letsencrypt.org/
+  "Free, automated, and open certificate authority (CA)"
+[certbot]: https://certbot.eff.org/
+  "Free, open source software tool for automatically using let's Encrypt certificates."
+[certbot-dns-linode]: https://certbot-dns-linode.readthedocs.io/en/stable/
+  "Certbot plugin which automates the process of completing an ACME dns-01 challenge by creating TXT records using the Linode API."
+[securityheaders-report]: https://securityheaders.com/?q=pablotron.org&hide=on&followRedirects=on
+  "Security headers report for this site from securityheaders.com"
+[securityheaders.com]: https://securityheaders.com/
+  "Free and easy to use tool to check the web site security headers."
+[sass]: https://en.wikipedia.org/wiki/Sass_(style_sheet_language)
+  "Syntactically Awesome Style Sheet (SASS)"
+[style.sass.txt]: /files/articles/site-backend/style.sass.txt
+  "Download SASS configuration"
+[html]: https://en.wikipedia.org/wiki/HTML
+  "HyperText Markup Language (HTML)"