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diff --git a/vhosts/blog/public/posts/2022-11-19/phperkaigi-2023-unused-token-quiz-2/index.html b/vhosts/blog/public/posts/2022-11-19/phperkaigi-2023-unused-token-quiz-2/index.html new file mode 100644 index 00000000..a870f0d4 --- /dev/null +++ b/vhosts/blog/public/posts/2022-11-19/phperkaigi-2023-unused-token-quiz-2/index.html @@ -0,0 +1,225 @@ +<!DOCTYPE html> +<html lang="ja-JP"> + <head> + <meta charset="UTF-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="author" content="nsfisis"> + <meta name="copyright" content="© 2022 nsfisis"> + <meta name="description" content="来年の PHPerKaigi 2023 でデジタルサーカス株式会社から出題予定のトークン問題のうち、ボツになった問題を公開する (その 2)。"> + <meta name="keywords" content="PHP,PHPerKaigi"> + <link rel="icon" type="image/svg+xml" href="/favicon.svg"> + <title>PHPerKaigi 2023: ボツになったトークン問題 その 2 | REPL: Rest-Eat-Program Loop</title> + <link rel="stylesheet" href="/style.css?h=37fff6a2f0eef473abde58e55f28ea69"> + <link rel="stylesheet" href="/hl.css?h=340e65ffd5c17713efc9107c06304f7b"> + </head> + <body class="single"> + <header class="header"> + <nav class="nav"> + <ul> + <li> + <a href="/">REPL: Rest-Eat-Program Loop</a> + </li> + <li> + <a href="/about/">About</a> + </li> + <li> + <a href="/posts/">Posts</a> + </li> + <li> + <a href="/slides/">Slides</a> + </li> + <li> + <a href="/tags/">Tags</a> + </li> + </ul> + </nav> + </header> + <main class="main"> + <article class="post-single"> + <header class="post-header"> + <h1 class="post-title">PHPerKaigi 2023: ボツになったトークン問題 その 2</h1> + <ul class="post-tags"> + <li class="tag"> + <a href="/tags/php/">PHP</a> + </li> + <li class="tag"> + <a href="/tags/phperkaigi/">PHPerKaigi</a> + </li> + </ul> + </header> + <div class="post-content"> + <section> + <h2 id="changelog">更新履歴</h2> + <ol> + <li class="revision"> + <time datetime="2022-11-19">2022-11-19</time>: 公開 + </li> + </ol> + </section> + <section id="section--intro"> + <h2><a href="#section--intro">はじめに</a></h2> + <p> + 2023 年 3 月 23 日から 25 日にかけて開催予定 (記事執筆時点) の <a href="https://phperkaigi.jp/2023/">PHPerKaigi 2023</a> において、 昨年と同様に、弊社 <a href="https://www.dgcircus.com/">デジタルサーカス株式会社</a> からトークン問題を出題予定である。 + </p> + + <p> + 昨年のトークン問題の記事はこちら: <a href="/posts/2022-04-09/phperkaigi-2022-tokens/">PHPerKaigi 2022 トークン問題の解説</a> + </p> + + <p> + すでに 2023 年用の問題は作成済みであるが、その制作過程の中でいくつかボツ問ができた。せっかくなので、PHPerKaigi 開催を待つ間に紹介しようと思う。 + </p> + + <p> + 10 月から 2 月まで、毎月 1 記事ずつ公開していく予定 (忘れていなければ)。 + </p> + + <p> + その 1 はこちら: <a href="/posts/2022-10-23/phperkaigi-2023-unused-token-quiz-1/">PHPerKaigi 2023: ボツになったトークン問題 その 1</a> + </p> + </section> + + <section id="section--quiz"> + <h2><a href="#section--quiz">問題</a></h2> + <p> + 注意: これはボツ問なので、得られたトークンを PHPerKaigi で入力してもポイントにはならない。 + </p> + + <pre class="highlight" language="php" linenumbering="unnumbered"><code class="highlight"><span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span></code></pre> + + <p> + "And Then There Were None" (そして誰もいなくなった) と名付けた作品。変則 quine (自分自身と同じソースコードを出力するプログラム) になっている。 + </p> + </section> + + <section id="section--how-to-obtain-token"> + <h2><a href="#section--how-to-obtain-token">トークン入手方法</a></h2> + <p> + 実行してみると、次のような出力が得られる。 + </p> + + <pre class="highlight" language="php" linenumbering="unnumbered"><code class="highlight"><span class="hljs-comment">#</span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span></code></pre> + + <p> + 1 行目を除き、先ほどのコードとほぼ同じものが出てきた。もう一度実行してみる。 + </p> + + <pre class="highlight" language="php" linenumbering="unnumbered"><code class="highlight"><span class="hljs-comment">#</span> +W +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span> +<span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">""</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span></code></pre> + + <p> + 今度は 2 行目が書き換えられた。すべての行が変化するまで繰り返すと次のようになる。 + </p> + + <pre class="highlight" language="php" linenumbering="unnumbered"><code class="highlight"><span class="hljs-comment">#</span> +W +E +L +O +V +E +P +H +P</code></pre> + + <p> + トークン「#WELOVEPHP」が手に入った。 + </p> + </section> + + <section id="section--commentary"> + <h2><a href="#section--commentary">解説</a></h2> + <p> + 一見すると同じ行が 10 行並んでいるだけなのにも関わらず、なぜそれぞれの行で出力が変わるのか。ソースコードをコピーして、適当なエディタに貼り付けるとわかりやすい。 + </p> + + <p> + Vim で開くと次のようになる (1 行目を抜粋)。 + </p> + + <pre class="highlight" language="php" linenumbering="unnumbered"><code class="highlight"><span class="hljs-meta"><?php</span> <span class="hljs-title function_ invoke__">printf</span>((<span class="hljs-keyword">isset</span>(<span class="hljs-variable">$s</span>)?<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">trim</span>(<span class="hljs-variable">$s</span>,<span class="hljs-string">"<200b>"</span>):<span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>))(<span class="hljs-variable">$s</span>=<span class="hljs-string">'<200b><?php printf((isset($s)?fn($s)=>trim($s,"<200b>"):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span>).<span class="hljs-string">"\n"</span>,<span class="hljs-string">"\x27<span class="hljs-subst">$s</span>\x27"</span>);<span class="hljs-meta">?></span></code></pre> + + <p> + <code><200b></code> と表示されているのは、Unicode の U+200b で、ゼロ幅スペースである。 + </p> + + <div class="admonition"> + <div class="admonition-label"> + NOTE + </div> + <div class="admonition-content"> + <p> + エディタによっては、ゼロ幅スペースが見えないことがある。VSCode ではブラウザと同様に不可視だった。 + </p> + </div> + </div> + + <p> + 文字列リテラルの中にゼロ幅スペースを仕込むことで、見た目を変えずに情報をエンコードすることが可能となる。 + </p> + + <p> + 続いて、トークンへの変換ロジックを解析する。注目すべきはこの部分だ。以下、ゼロ幅スペースは Vim での表示に合わせて <code><200b></code> と記載する。 + </p> + + <pre class="highlight" language="php" linenumbering="unnumbered"><code class="highlight"><span class="hljs-function"><span class="hljs-keyword">fn</span>(<span class="hljs-params"><span class="hljs-variable">$s</span></span>)=></span><span class="hljs-title function_ invoke__">chr</span>(<span class="hljs-title function_ invoke__">strlen</span>(<span class="hljs-variable">$s</span>)/<span class="hljs-number">3</span>)</code></pre> + + <p> + PHP の <code>strlen()</code> は文字列のバイト数を返す。1 行目の <code>$s</code> は以下の内容となっており、 + </p> + + <pre class="highlight" language="php" linenumbering="unnumbered"><code class="highlight"><span class="hljs-variable">$s</span>=<span class="hljs-string">'<200b><?php printf((isset($s)?fn($s)=>trim($s,"<200b>"):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span></code></pre> + + <p> + このソースコードは UTF-8 で書かれているので、105 バイトになる。それを 3 で割ると 35 となり、これは <code>#</code> の ASCII コードと一致する。他の行も、同様にしてゼロ幅スペースを詰めることで文字列長を調整し、トークンをエンコードしている。 + </p> + + <p> + デコード部以外の部分は、quine のための記述である。 + </p> + </section> + + <section id="section--outro"> + <h2><a href="#section--outro">おわりに</a></h2> + <p> + <a href="https://blog.rust-lang.org/2021/11/01/cve-2021-42574.html">CVE-2021-42574</a> に着想を得た作品。この脆弱性は、Unicode の制御文字である left-to-right mark と right-to-left mark を利用し、ソースコードの実際の内容を欺く、というもの。簡単のためゼロ幅スペースを用いることとし、ついでに quine にもするとこうなった。 + </p> + + <p> + ボツになった理由は、ゼロ幅スペースを表示してくるエディタが想像以上に多かったため。「同じ行が並んでいるだけなのに出力が異なる」というアイデアの根幹を崩されてしまうので、この問題は不採用となった。 + </p> + </section> + 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