fix(worker): constrain nonce value to be a whole integer (#1045)

* fix(worker): constrain nonce value to be a whole integer

Closes #1043

Sometimes the worker could get into a strange state where it has a
decimal nonce, but the server assumes that the nonce can only be a whole
number. This patch constrains the nonce to be a whole number on the
worker end by detecting if the nonce is a decimal number and then
truncating away the decimal portion.

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix(algorithms/fast): truncate decimal place on number of threads

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>

.github/actions/spelling/expect.txt

@@ -304,6 +304,7 @@ Tik
 Timpibot
 TLog
 traefik
+trunc
 uberspace
 Unbreak
 unbreakdocker

docs/docs/CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 <!-- This changes the project to: -->
+
 - Added a missing link to the Caddy installation environment in the installation documentation.
 - Downstream consumers can change the default [log/slog#Logger](https://pkg.go.dev/log/slog#Logger) instance that Anubis uses by setting `opts.Logger` to your slog instance of choice ([#864](https://github.com/TecharoHQ/anubis/issues/864)).
 - The [Thoth client](https://anubis.techaro.lol/docs/admin/thoth) is now public in the repo instead of being an internal package.
@@ -30,6 +31,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - The hard dependency on WebCrypto has been removed, allowing a proof of work challenge to work over plain (unencrypted) HTTP.
 - Firefox for Android support has been fixed by embedding the challenge ID into the pass-challenge route. This also fixes some inconsistent issues with other mobile browsers.
 - The Anubis version number is put in the footer of every page.
+- Prevent the proof of work nonce from being a decimal value by using Math.trunc to coerce it back to an integer if it happens ([#1043](https://github.com/TecharoHQ/anubis/issues/1043)).
 - The legacy JSON based policy file example has been removed and all documentation for how to write a policy file in JSON has been deleted. JSON based policy files will still work, but YAML is the superior option for Anubis configuration.
 - A standard library HTTP server log message about HTTP pipelining not working has been filtered out of Anubis' logs. There is no action that can be taken about it.
 - The default `favicon` pattern in `data/common/keep-internet-working.yaml` has been updated to permit requests for png/gif/jpg/svg files as well as ico.

web/js/algorithms/fast.mjs

@@ -4,7 +4,7 @@ export default function process(
   difficulty = 5,
   signal = null,
   progressCallback = null,
-  threads = Math.max(navigator.hardwareConcurrency / 2, 1),
+  threads = Math.trunc(Math.max(navigator.hardwareConcurrency / 2, 1)),
 ) {
   console.debug("fast algo");
 

web/js/worker/sha256-purejs.mjs

@@ -53,6 +53,18 @@ addEventListener('message', async ({ data: eventData }) => {
     nonce += threads;
     iterations++;
 
+    /* Truncate the decimal portion of the nonce. This is a bit of an evil bit
+     * hack, but it works reliably enough. The core of why this works is:
+     * 
+     * > 13.4 % 1 !== 0
+     * true
+     * > 13 % 1 !== 0
+     * false
+     */
+    if (nonce % 1 !== 0) {
+      nonce = Math.trunc(nonce);
+    }
+
     // Send a progress update from the main thread every 1024 iterations.
     if (isMainThread && (iterations & 1023) === 0) {
       postMessage(nonce);

web/js/worker/sha256-webcrypto.mjs

@@ -49,6 +49,18 @@ addEventListener("message", async ({ data: eventData }) => {
     nonce += threads;
     iterations++;
 
+    /* Truncate the decimal portion of the nonce. This is a bit of an evil bit
+     * hack, but it works reliably enough. The core of why this works is:
+     * 
+     * > 13.4 % 1 !== 0
+     * true
+     * > 13 % 1 !== 0
+     * false
+     */
+    if (nonce % 1 !== 0) {
+      nonce = Math.trunc(nonce);
+    }
+
     // Send a progress update from the main thread every 1024 iterations.
     if (isMainThread && (iterations & 1023) === 0) {
       postMessage(nonce);