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diff --git a/public/posts/2022-11-19/phperkaigi-2023-unused-token-quiz-2/index.html b/public/posts/2022-11-19/phperkaigi-2023-unused-token-quiz-2/index.html index a40a5e6..e785f4f 100644 --- a/public/posts/2022-11-19/phperkaigi-2023-unused-token-quiz-2/index.html +++ b/public/posts/2022-11-19/phperkaigi-2023-unused-token-quiz-2/index.html @@ -4,18 +4,14 @@ <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta name="author" content="nsfisis"> - <meta name="copyright" content="© 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="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="/hl.css?208c52e3b7c9db1cad782c5d30b4698f"> - - <link rel="stylesheet" href="/style.css?779b1a3debcaeba619f6fe500e93d525"> - - <link rel="stylesheet" href="/custom.css?a649ea3528d4b626fb636505d94c1144"> - + <link rel="stylesheet" href="/hl.css?h=208c52e3b7c9db1cad782c5d30b4698f"> + <link rel="stylesheet" href="/style.css?h=779b1a3debcaeba619f6fe500e93d525"> + <link rel="stylesheet" href="/custom.css?h=a649ea3528d4b626fb636505d94c1144"> </head> <body class="single"> <header class="header"> @@ -29,225 +25,198 @@ <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> - + <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> - + <li class="revision"> + <time datetime="2022-11-19">2022-11-19</time>: 公開 + </li> </ol> </section> - <section class="section-1"> - <h2 id="" class="section-header"> - - はじめに - - </h2> - <div class="section-body"> - <div class="paragraph"> -<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> -</div> -<div class="paragraph"> -<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> -</div> -<div class="paragraph"> -<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> -</div> -<div class="paragraph"> -<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> -</div> -<div class="paragraph"> -<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> -</div> - </div> -</section> -<section class="section-1"> - <h2 id="" class="section-header"> - - 問題 - - </h2> - <div class="section-body"> - <div class="paragraph"> -<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> -</div> -<div id="source." class="listingblock"> -<div class="content"> -<pre class="rouge highlight"><code data-lang="php"><span class="o"><?</span><span class="n">php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span></code></pre> -</div> -</div> -<div class="paragraph"> -<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> -</div> - </div> -</section> -<section class="section-1"> - <h2 id="" class="section-header"> - - トークン入手方法 - - </h2> - <div class="section-body"> - <div class="paragraph"> -<p>実行してみると、次のような出力が得られる。</p> -</div> -<div id="source." class="listingblock"> -<div class="content"> -<pre class="rouge highlight"><code data-lang="php"><span class="c1">#</span> -<span class="o"><?</span><span class="n">php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span></code></pre> -</div> -</div> -<div class="paragraph"> -<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> -</div> -<div id="source." class="listingblock"> -<div class="content"> -<pre class="rouge highlight"><code data-lang="php"><span class="c1">#</span> -<span class="nc">W</span> -<span class="o"><?</span><span class="n">php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span> -<span class="cp"><?php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">""</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span></code></pre> -</div> -</div> -<div class="paragraph"> -<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> -</div> -<div id="source." class="listingblock"> -<div class="content"> -<pre class="rouge highlight"><code data-lang="php"><span class="c1">#</span> -<span class="nc">W</span> -<span class="nc">E</span> -<span class="nc">L</span> -<span class="nc">O</span> -<span class="nc">V</span> -<span class="nc">E</span> -<span class="nc">P</span> -<span class="nc">H</span> -<span class="nc">P</span></code></pre> -</div> -</div> -<div class="paragraph"> -<p>トークン「#WELOVEPHP」が手に入った。</p> -</div> - </div> -</section> -<section class="section-1"> - <h2 id="" class="section-header"> - - 解説 - - </h2> - <div class="section-body"> - <div class="paragraph"> -<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> -</div> -<div class="paragraph"> -<p>Vim で開くと次のようになる (1 行目を抜粋)。</p> -</div> -<div id="source." class="listingblock"> -<div class="content"> -<pre class="rouge highlight"><code data-lang="php"><span class="o"><?</span><span class="n">php</span> <span class="nb">printf</span><span class="p">((</span><span class="k">isset</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">?</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="s2">"<200b>"</span><span class="p">)</span><span class="o">:</span><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">))(</span><span class="nv">$s</span><span class="o">=</span><span class="s1">'<200b><?php printf((isset($s)?fn($s)=>trim($s,"<200b>"):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span><span class="p">)</span><span class="mf">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span><span class="s2">"</span><span class="se">\x27</span><span class="nv">$s</span><span class="se">\x27</span><span class="s2">"</span><span class="p">);</span><span class="cp">?></span></code></pre> -</div> -</div> -<div class="paragraph"> -<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> -<div class="admonitionblock note"> -<table> -<tr> -<td class="icon"> -<div class="title">Note</div> -</td> -<td class="content"> -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。 -</td> -</tr> -</table> -</div> -<div class="paragraph"> -<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> -</div> -<div class="paragraph"> -<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> -</div> -<div id="source." class="listingblock"> -<div class="content"> -<pre class="rouge highlight"><code data-lang="php"><span class="k">fn</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">=></span><span class="nb">chr</span><span class="p">(</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">/</span><span class="mi">3</span><span class="p">)</span></code></pre> -</div> -</div> -<div class="paragraph"> -<p>PHP の <code>strlen()</code> は文字列のバイト数を返す。1 行目の <code>$s</code> は以下の内容となっており、</p> -</div> -<div id="source." class="listingblock"> -<div class="content"> -<pre class="rouge highlight"><code data-lang="php"><span class="nv">$s</span><span class="o">=</span><span class="s1">'<200b><?php printf((isset($s)?fn($s)=>trim($s,"<200b>"):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</span></code></pre> -</div> -</div> -<div class="paragraph"> -<p>このソースコードは UTF-8 で書かれているので、105 バイトになる。それを 3 で割ると 35 となり、これは <code>#</code> の ASCII コードと一致する。他の行も、同様にしてゼロ幅スペースを詰めることで文字列長を調整し、トークンをエンコードしている。</p> -</div> -<div class="paragraph"> -<p>デコード部以外の部分は、quine のための記述である。</p> -</div> - </div> -</section> -<section class="section-1"> - <h2 id="" class="section-header"> - - おわりに - - </h2> - <div class="section-body"> - <div class="paragraph"> -<p><a href="https://blog.rust-lang.org/2021/11/01/cve-2021-42574.html">CVE-2021-42574</a> に着想を得た作品。この脆弱性は、Unicode の制御文字である left-to-right mark と right-to-left mark を利用し、ソースコードの実際の内容を欺く、というもの。簡単のためゼロ幅スペースを用いることとし、ついでに quine にもするとこうなった。</p> -</div> -<div class="paragraph"> -<p>ボツになった理由は、ゼロ幅スペースを表示してくるエディタが想像以上に多かったため。「同じ行が並んでいるだけなのに出力が異なる」というアイデアの根幹を崩されてしまうので、この問題は不採用となった。</p> -</div> - </div> -</section> + <section id="section--_はじめに"> + <h2><a href="#section--_はじめに">はじめに</a></h2> + <p> + 2023 年 3 月 23 日から 25 日にかけて開催予定 (記事執筆時点) の<a xl:href="https://phperkaigi.jp/2023/">PHPerKaigi 2023</a>において、 昨年と同様に、弊社<a xl:href="https://www.dgcircus.com/">デジタルサーカス株式会社</a>からトークン問題を出題予定である。 + </p> + + <p> + 昨年のトークン問題の記事はこちら:<a xl:href="/posts/2022-04-09/phperkaigi-2022-tokens/">PHPerKaigi 2022 トークン問題の解説</a> + </p> + + <p> + すでに 2023 年用の問題は作成済みであるが、その制作過程の中でいくつかボツ問ができた。せっかくなので、PHPerKaigi 開催を待つ間に紹介しようと思う。 + </p> + + <p> + 10 月から 2 月まで、毎月 1 記事ずつ公開していく予定 (忘れていなければ)。 + </p> + + <p> + その 1 はこちら:<a xl:href="/posts/2022-10-23/phperkaigi-2023-unused-token-quiz-1/">PHPerKaigi 2023: ボツになったトークン問題 その 1</a> + </p> + </section> + + <section id="section--_問題"> + <h2><a href="#section--_問題">問題</a></h2> + <p> + 注意: これはボツ問なので、得られたトークンを PHPerKaigi で入力してもポイントにはならない。 + </p> + + <pre language="php" linenumbering="unnumbered"> + <code><?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?></code> + </pre> + + <p> + "And Then There Were None" (そして誰もいなくなった) と名付けた作品。変則 quine (自分自身と同じソースコードを出力するプログラム) になっている。 + </p> + </section> + + <section id="section--_トークン入手方法"> + <h2><a href="#section--_トークン入手方法">トークン入手方法</a></h2> + <p> + 実行してみると、次のような出力が得られる。 + </p> + + <pre language="php" linenumbering="unnumbered"> + <code># + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> + <?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?></code> + </pre> + + <p> + 1 行目を除き、先ほどのコードとほぼ同じものが出てきた。もう一度実行してみる。 + </p> + + <pre language="php" linenumbering="unnumbered"> + <code># +W +<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> +<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> +<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> +<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> +<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> +<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> +<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?> +<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s='<?php printf((isset($s)?fn($s)=>trim($s,""):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?></code> + </pre> + + <p> + 今度は 2 行目が書き換えられた。すべての行が変化するまで繰り返すと次のようになる。 + </p> + + <pre language="php" linenumbering="unnumbered"> + <code># +W +E +L +O +V +E +P +H +P</code> + </pre> + + <p> + トークン「#WELOVEPHP」が手に入った。 + </p> + </section> + + <section id="section--_解説"> + <h2><a href="#section--_解説">解説</a></h2> + <p> + 一見すると同じ行が 10 行並んでいるだけなのにも関わらず、なぜそれぞれの行で出力が変わるのか。ソースコードをコピーして、適当なエディタに貼り付けるとわかりやすい。 + </p> + + <p> + Vim で開くと次のようになる (1 行目を抜粋)。 + </p> + + <pre language="php" linenumbering="unnumbered"> + <code><?php printf((isset($s)?fn($s)=>trim($s,"<200b>"):fn($s)=>chr(strlen($s)/3))($s='<200b><?php printf((isset($s)?fn($s)=>trim($s,"<200b>"):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>')."\n","\x27$s\x27");?></code> + </pre> + + <p> + <code><200b></code>と表示されているのは、Unicode の U+200b で、ゼロ幅スペースである。 + </p> + + <div> + <div> + Note + </div> + <div> + <p> + エディタによっては、ゼロ幅スペースが見えないことがある。VSCode ではブラウザと同様に不可視だった。 + </p> + </div> + </div> + + <p> + 文字列リテラルの中にゼロ幅スペースを仕込むことで、見た目を変えずに情報をエンコードすることが可能となる。 + </p> + + <p> + 続いて、トークンへの変換ロジックを解析する。注目すべきはこの部分だ。以下、ゼロ幅スペースは Vim での表示に合わせて<code><200b></code>と記載する。 + </p> + + <pre language="php" linenumbering="unnumbered"> + <code>fn($s)=>chr(strlen($s)/3)</code> + </pre> + + <p> + PHP の<code>strlen()</code>は文字列のバイト数を返す。1 行目の<code>$s</code>は以下の内容となっており、 + </p> + + <pre language="php" linenumbering="unnumbered"> + <code>$s='<200b><?php printf((isset($s)?fn($s)=>trim($s,"<200b>"):fn($s)=>chr(strlen($s)/3))($s=%s)."\n","\x27$s\x27");?>'</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--_おわりに"> + <h2><a href="#section--_おわりに">おわりに</a></h2> + <p> + <a xl: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> </div> - </article> </main> <footer class="footer"> |