Add a fix for the Varnish PoW bot blocker.HEADmagister

2 files changed, 46 insertions, 0 deletions

diff --git a/GNUmakefile b/GNUmakefile
index c0198e9..071c7a1 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -38,6 +38,7 @@ CONTENT_SCRIPTS = $(addprefix content/, \
 	the-chosen-videos.js \
 	vatican-news-main-page.js \
 	vatican-news-site.js \
+	varnish-pow-bot-blocker.js \
 )
 
 manifest.json: manifest.json.in get-code-block.awk $(CONTENT_SCRIPTS)
diff --git a/content/varnish-pow-bot-blocker.js b/content/varnish-pow-bot-blocker.js
new file mode 100644
index 0000000..a4c129f
--- /dev/null
+++ b/content/varnish-pow-bot-blocker.js
@@ -0,0 +1,45 @@
+/**
+ * SPDX-License-Identifier: CC0-1.0
+ *
+ * Copyright (C) 2026 Woj. Kosior <koszko@koszko.org>
+ */
+
+/*
+  #+begin_src manifest-jq
+  .matches = ["<all_urls>"]
+  #+end_src
+*/
+
+if (false) { /* #+begin_src background-js */
+    blockJsOnCookie(/^pow_challenge=[0-9]{12}[.]/);
+} /* #+end_src */
+
+/*
+ * Solve "Varnish PoW" challenges.  These are used in some places under
+ * *.debian.org and are derived from haphash PoW challenges.  We utilize
+ * `pow-solver.js' for computing the hashes and
+ * `appended-number-counting-schemes.js' for the counting scheme.
+ */
+
+(() => {
+
+const target = new URLSearchParams(window.location.search).get('original');
+const match = /(?:^|;)\s*pow_challenge=(\S*)/.exec(document.cookie);
+if (target && match && !window.location.href.startsWith("file://")) {
+    document.documentElement.innerHTML = `\
+<p style="margin: 1em auto; max-width: 600px; text-align: center;">
+    Simple extension is trying to solve a Varnish PoW challenge on this page…
+</p>
+`;
+
+    const challenge = match[1];
+    /* A fixed length of 8 zero bits is required by this challenge. */
+    genericSolvePow(challenge + ';', 8, appendedNumberCountingSchemes)
+        .then(({suffixArray}) => {
+            const nonce = new TextDecoder().decode(suffixArray);
+            document.cookie = `pow_nonce=${nonce}; Path=/`;
+            window.location.href = target;
+        });
+}
+
+})();