cmd/anubis: drastically optimize proof of work (#19)

* cmd/anubis: drastically optimize proof of work

Closes #12
Closes #17

This drastically optimizes the proof of work check by removing the
stringify call at every iteration. Additionally, this optimizes the
checks by running them in parallel for as many threads as the browser
has available (according to navigator.hardwareConcurrency).

This also changes the redirect lag to 250 milliseconds instead of 2000
milliseconds in order to be perceptually faster. This is below the
reaction time threshold of many people, so this will make the post-check
success phase perceptually instant.

Testing on an iPhone 7 Plus has shown that this can clear a difficulty 4
check in 3.4 seconds.

This actually optimizes the check so much it may be a logistical concern
for operators.

* cmd/anubis/js: fix happy cachebuster logic

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

---------

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

cmd/anubis/static/js/main.mjs

@@ -1,2 +1,2 @@
-(()=>{function l(n,s=5){return new Promise((i,e)=>{let o=URL.createObjectURL(new Blob(["(",w(),")()"],{type:"application/javascript"})),t=new Worker(o);t.onmessage=r=>{t.terminate(),i(r.data)},t.onerror=r=>{t.terminate(),e()},t.postMessage({data:n,difficulty:s}),URL.revokeObjectURL(o)})}function w(){return function(){let n=s=>{let i=new TextEncoder().encode(s);return crypto.subtle.digest("SHA-256",i.buffer).then(e=>Array.from(new Uint8Array(e)).map(o=>o.toString(16).padStart(2,"0")).join(""))};addEventListener("message",async s=>{let i=s.data.data,e=s.data.difficulty,o,t=0;do o=await n(i+t++);while(o.substring(0,e)!==Array(e+1).join("0"));t-=1,postMessage({hash:o,data:i,difficulty:e,nonce:t})})}.toString()}var h=(n="",s={})=>{let i=new URL(n,window.location.href);return Object.entries(s).forEach(e=>{let[o,t]=e;i.searchParams.set(o,t)}),i.toString()},m=n=>`/.within.website/x/cmd/anubis/static/img/${n}.webp`;(async()=>{let n=document.getElementById("status"),s=document.getElementById("image"),i=document.getElementById("title"),e=document.getElementById("spinner");n.innerHTML="Calculating...";let{challenge:o,difficulty:t}=await fetch("/.within.website/x/cmd/anubis/api/make-challenge",{method:"POST"}).then(a=>{if(!a.ok)throw new Error("Failed to fetch config");return a.json()}).catch(a=>{throw i.innerHTML="Oh no!",n.innerHTML=`Failed to fetch config: ${a.message}`,s.src=m("sad"),e.innerHTML="",e.style.display="none",a});n.innerHTML=`Calculating...<br/>Difficulty: ${t}`;let r=Date.now(),{hash:u,nonce:c}=await l(o,t),d=Date.now();i.innerHTML="Success!",n.innerHTML=`Done! Took ${d-r}ms, ${c} iterations`,s.src=m("happy"),e.innerHTML="",e.style.display="none",setTimeout(()=>{let a=window.location.href;window.location.href=h("/.within.website/x/cmd/anubis/api/pass-challenge",{response:u,nonce:c,redir:a,elapsedTime:d-r})},2e3)})();})();
+(()=>{function m(n,i=5,e=navigator.hardwareConcurrency){return new Promise((t,d)=>{let s=URL.createObjectURL(new Blob(["(",p(),")()"],{type:"application/javascript"})),a=[];for(let u=0;u<e;u++){let o=new Worker(s);o.onmessage=r=>{a.forEach(c=>c.terminate()),o.terminate(),t(r.data)},o.onerror=r=>{o.terminate(),d()},o.postMessage({data:n,difficulty:i,nonce:1e6*u}),a.push(o)}URL.revokeObjectURL(s)})}function p(){return function(){let n=e=>{let t=new TextEncoder().encode(e);return crypto.subtle.digest("SHA-256",t.buffer)};function i(e){return Array.from(e).map(t=>t.toString(16).padStart(2,"0")).join("")}addEventListener("message",async e=>{let t=e.data.data,d=e.data.difficulty,s,a=e.data.nonce||0;for(;;){let u=await n(t+a++),o=new Uint8Array(u),r=!0;for(let c=0;c<d;c++){let l=Math.floor(c/2),f=c%2;if((o[l]>>(f===0?4:0)&15)!==0){r=!1;break}}if(r){s=i(o),console.log(s);break}}a-=1,postMessage({hash:s,data:t,difficulty:d,nonce:a})})}.toString()}var w=(n="",i={})=>{let e=new URL(n,window.location.href);return Object.entries(i).forEach(t=>{let[d,s]=t;e.searchParams.set(d,s)}),e.toString()},h=(n,i)=>w(`/.within.website/x/cmd/anubis/static/img/${n}.webp`,{cacheBuster:i});(async()=>{let n=document.getElementById("status"),i=document.getElementById("image"),e=document.getElementById("title"),t=document.getElementById("spinner"),d=JSON.parse(document.getElementById("anubis_version").textContent);n.innerHTML="Calculating...";let{challenge:s,difficulty:a}=await fetch("/.within.website/x/cmd/anubis/api/make-challenge",{method:"POST"}).then(l=>{if(!l.ok)throw new Error("Failed to fetch config");return l.json()}).catch(l=>{throw e.innerHTML="Oh no!",n.innerHTML=`Failed to fetch config: ${l.message}`,i.src=h("sad"),t.innerHTML="",t.style.display="none",l});n.innerHTML=`Calculating...<br/>Difficulty: ${a}`;let u=Date.now(),{hash:o,nonce:r}=await m(s,a),c=Date.now();console.log({hash:o,nonce:r}),e.innerHTML="Success!",n.innerHTML=`Done! Took ${c-u}ms, ${r} iterations`,i.src=h("happy",d),t.innerHTML="",t.style.display="none",setTimeout(()=>{let l=window.location.href;window.location.href=w("/.within.website/x/cmd/anubis/api/pass-challenge",{response:o,nonce:r,redir:l,elapsedTime:c-u})},250)})();})();
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