{"id":38822,"date":"2019-10-31T22:26:11","date_gmt":"2019-10-31T19:26:11","guid":{"rendered":"https:\/\/prohoster.info\/blog\/reshenie-zadaniya-s-pwnable-kr-25-otp-ogranichenie-ramera-fajla-v-linux\/"},"modified":"2019-10-31T22:26:11","modified_gmt":"2019-10-31T19:26:11","slug":"reshenie-zadaniya-s-pwnable-kr-25-otp-ogranichenie-ramera-fajla-v-linux","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sv\/blog\/administrirovanie\/reshenie-zadaniya-s-pwnable-kr-25-otp-ogranichenie-ramera-fajla-v-linux","title":{"rendered":"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/70434b41e923b3b46bcdff1ab7e03937.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\nI denna artikel l\u00f6ser vi uppgift 25 fr\u00e5n webbplatsen <noindex><a rel=\"nofollow\" href=\"https:\/\/pwnable.kr\/index.php\">pwnable.kr<\/a><\/noindex>.<\/p>\n<p><b class=\"spoiler_title\">Organisationsinformation<\/b>Speciellt f\u00f6r dem som vill l\u00e4ra sig n\u00e5got nytt och utvecklas inom olika omr\u00e5den av informations- och dators\u00e4kerhet, kommer jag att skriva och ber\u00e4tta om f\u00f6ljande kategorier:<\/p>\n<ul>\n<li>PWN;<\/li>\n<li>kryptografi (Crypto);<\/li>\n<li>n\u00e4tverksteknologier (Network);<\/li>\n<li>reverse engineering (Reverse Engineering);<\/li>\n<li>steganografi (Stegano);<\/li>\n<li>s\u00f6kning och utnyttjande av WEB-s\u00e5rbarheter.<\/li>\n<\/ul>\n<p>\nUt\u00f6ver detta kommer jag att dela med mig av min erfarenhet inom datorforensik, analys av skadlig programvara och firmware, attacker p\u00e5 tr\u00e5dl\u00f6sa n\u00e4tverk och lokala datan\u00e4tverk, genomf\u00f6rande av penetrationstester och skrivande av exploits.<br \/>\n<noindex><a rel=\"nofollow\" name=\"habracut\"><\/a><\/noindex><br \/>\nF\u00f6r att du ska kunna h\u00e5lla dig informerad om nya artiklar, programvara och annan information har jag skapat <noindex><a rel=\"nofollow\" href=\"https:\/\/t.me\/RalfHackerChannel\">en kanal p\u00e5 Telegram<\/a><\/noindex> och <noindex><a rel=\"nofollow\" href=\"https:\/\/t.me\/RalfHackerPublicChat\">en grupp f\u00f6r att diskutera alla fr\u00e5gor<\/a><\/noindex> inom omr\u00e5det cybers\u00e4kerhet. \u00c4ven dina personliga f\u00f6rfr\u00e5gningar, fr\u00e5gor, f\u00f6rslag och rekommendationer <noindex><a rel=\"nofollow\" href=\"https:\/\/t.me\/hackerralf8\">kommer jag att ta upp personligen och svara alla<\/a><\/noindex>.<\/p>\n<p>All information presenteras uteslutande i utbildningssyfte. F\u00f6rfattaren av detta dokument tar inget ansvar f\u00f6r eventuell skada som orsakas n\u00e5gon genom anv\u00e4ndning av kunskaper och metoder som erh\u00e5llits genom att studera detta dokument.<\/p>\n<h2>L\u00f6sning av uppgift otp<\/h2>\n<p>\nVi forts\u00e4tter med den andra delen. Jag s\u00e4ger med en g\u00e5ng att den \u00e4r sv\u00e5rare \u00e4n den f\u00f6rsta, men denna g\u00e5ng f\u00e5r vi inte programkoden. Gl\u00f6m inte diskussionen h\u00e4r(https:\/\/t.me\/RalfHackerPublicChat) och h\u00e4r (https:\/\/t.me\/RalfHackerChannel). Vi b\u00f6rjar.<\/p>\n<p>Vi klickar p\u00e5 ikonen med namnet otp. Vi f\u00e5r en adress och port f\u00f6r att ansluta.<\/p>\n<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/fec98a1c755c36ba1a7117bfc5154611.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nVi ansluter och ser oss omkring p\u00e5 servern.<\/p>\n<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/71983f5701fe2b1366cebfb0d2d57f74.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nFlaggan som vi inte kan l\u00e4sa, programmet och dess k\u00e4llkod. L\u00e5t oss titta p\u00e5 k\u00e4llkoden.<\/p>\n<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/63e409cd939f41db29ee5c1edfa107a0.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nVi g\u00e5r igenom den. Programmet tar ett l\u00f6senord som argument.<\/p>\n<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/5eb6bccb7ed4b82fdd01e24854c2c953.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nD\u00e4refter sparas 16 slumpm\u00e4ssiga byte i variabeln otp.<\/p>\n<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/c1420a16c9721a8c87fb86277674f0f2.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nI mappen tmp skapas en fil med ett slumpm\u00e4ssigt namn (de f\u00f6rsta 8 byte av otp) och 8 slumpm\u00e4ssiga byte (de andra 8 byte av otp) skrivs in i den.<\/p>\n<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/d6fcc612f6cddbff338fff0aaf9b73a1.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nAv n\u00e5gon anledning l\u00e4ses v\u00e4rdet fr\u00e5n den skapade filen och j\u00e4mf\u00f6rs med det angivna l\u00f6senordet.<\/p>\n<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/42302a748b7cd57a6337be00eab2c47b.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nH\u00e4r f\u00f6rekommer s\u00e5rbarheten. Den ligger i mellanlagringen av det genererade talet i filen. Vi kan begr\u00e4nsa filstorleken, till exempel till 0, s\u00e5 att vid skrivning och l\u00e4sning med l\u00f6senordet j\u00e4mf\u00f6rs 0. Detta kan g\u00f6ras s\u00e5 h\u00e4r.<\/p>\n<pre><code class=\"bash\"># ulimit -f 0<\/code><\/pre>\n<p>\n<img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/3af83c20d1de7435b0f40a36c8187ff0.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nNu ska vi k\u00f6ra programmet.<\/p>\n<p><img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/a289bd59a22aa495fe6407c3c8ff0416.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nVi f\u00e5r ett fel. Ingen fara, det kan hanteras med hj\u00e4lp av Python.<\/p>\n<pre><code class=\"python\">python -c \"import os, signal; signal.signal(signal.SIGXFSZ, signal.SIG_IGN); os.system('.\/otp 0')\" <\/code><\/pre>\n<p>\n<img decoding=\"async\" alt=\"L\u00f6sning av uppgiften fr\u00e5n pwnable.kr 25 \u2014 otp. Filstorleksbegr\u00e4nsning i Linux\" src=\"\/wp-content\/uploads\/2019\/10\/b8513f020879d5e5ee957e1bc137b61a.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nVi f\u00e5r flaggan och l\u00e4tta 100 po\u00e4ng. Och vi forts\u00e4tter: i n\u00e4sta artikel kommer vi att ber\u00f6ra Web. Du kan g\u00e5 med oss i <noindex><a rel=\"nofollow\" href=\"https:\/\/t.me\/RalfHackerChannel\">Telegram<\/a><\/noindex>.<br \/>\n<br \/>K\u00e4lla: <a content=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/post\/471042\/\">habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u0412 \u0434\u0430\u043d\u043d\u043e\u0439 \u0441\u0442\u0430\u0442\u044c\u0435 \u0440\u0435\u0448\u0438\u043c 25-\u0435 \u0437\u0430\u0434\u0430\u043d\u0438\u0435 \u0441 \u0441\u0430\u0439\u0442\u0430 pwnable.kr. \u041e\u0440\u0433\u0430\u043d\u0438\u0437\u0430\u0446\u0438\u043e\u043d\u043d\u0430\u044f \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044f\u0421\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u043e \u0434\u043b\u044f \u0442\u0435\u0445, \u043a\u0442\u043e \u0445\u043e\u0447\u0435\u0442 \u0443\u0437\u043d\u0430\u0432\u0430\u0442\u044c \u0447\u0442\u043e-\u0442\u043e \u043d\u043e\u0432\u043e\u0435 \u0438 \u0440\u0430\u0437\u0432\u0438\u0432\u0430\u0442\u044c\u0441\u044f \u0432 \u043b\u044e\u0431\u043e\u0439 \u0438\u0437 \u0441\u0444\u0435\u0440 \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u043e\u043d\u043d\u043e\u0439 \u0438 \u043a\u043e\u043c\u043f\u044c\u044e\u0442\u0435\u0440\u043d\u043e\u0439 \u0431\u0435\u0437\u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438, \u044f \u0431\u0443\u0434\u0443 \u043f\u0438\u0441\u0430\u0442\u044c \u0438 \u0440\u0430\u0441\u0441\u043a\u0430\u0437\u044b\u0432\u0430\u0442\u044c \u043e \u0441\u043b\u0435\u0434\u0443\u044e\u0449\u0438\u0445 \u043a\u0430\u0442\u0435\u0433\u043e\u0440\u0438\u044f\u0445: PWN; \u043a\u0440\u0438\u043f\u0442\u043e\u0433\u0440\u0430\u0444\u0438\u044f (Crypto); c\u0435\u0442\u0435\u0432\u044b\u0435 \u0442\u0435\u0445\u043d\u043e\u043b\u043e\u0433\u0438\u0438 (Network); \u0440\u0435\u0432\u0435\u0440\u0441 (Reverse Engineering); \u0441\u0442\u0435\u0433\u0430\u043d\u043e\u0433\u0440\u0430\u0444\u0438\u044f (Stegano); \u043f\u043e\u0438\u0441\u043a \u0438 \u044d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0430\u0446\u0438\u044f WEB-\u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439. \u0412\u0434\u043e\u0431\u0430\u0432\u043e\u043a \u043a \u044d\u0442\u043e\u043c\u0443 \u044f [&hellip;]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":29120,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[688],"tags":[],"class_list":["post-38822","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-administrirovanie"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 5.0.4 - aioseo.com -->\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<meta name=\"author\" content=\"Yuri Gagarin\"\/>\n\t<link rel=\"canonical\" href=\"https:\/\/prohoster.info\/sv\/blog\/administrirovanie\/reshenie-zadaniya-s-pwnable-kr-25-otp-ogranichenie-ramera-fajla-v-linux\" \/>\n\t\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 5.0.4\" \/>\n\t\t<meta property=\"og:locale\" content=\"sv_SE\" \/>\n\t\t<meta property=\"og:site_name\" content=\"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"\ud83e\udd47\u0420\u0435\u0448\u0435\u043d\u0438\u0435 \u0437\u0430\u0434\u0430\u043d\u0438\u044f \u0441 pwnable.kr 25 \u2014 otp. \u041e\u0433\u0440\u0430\u043d\u0438\u0447\u0435\u043d\u0438\u0435 \u0440\u0430\u043c\u0435\u0440\u0430 \u0444\u0430\u0439\u043b\u0430 \u0432 Linux | ProHoster\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/prohoster.info\/sv\/blog\/administrirovanie\/reshenie-zadaniya-s-pwnable-kr-25-otp-ogranichenie-ramera-fajla-v-linux\" \/>\n\t\t<meta property=\"og:image\" content=\"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg\" \/>\n\t\t<meta property=\"og:image:secure_url\" content=\"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg\" \/>\n\t\t<meta property=\"og:image:width\" content=\"350\" \/>\n\t\t<meta property=\"og:image:height\" content=\"350\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2019-10-31T19:26:11+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2019-10-31T19:26:11+00:00\" \/>\n\t\t<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/prohoster\" \/>\n\t\t<meta property=\"article:author\" content=\"https:\/\/www.facebook.com\/prohoster\" \/>\n\t\t<!-- All in One SEO -->\n\n","aioseo_head_json":{"title":"\ud83e\udd47L\u00f6sning av uppgift med pwnable.kr 25 - otp. 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