{"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\/sl\/blog\/administrirovanie\/reshenie-zadaniya-s-pwnable-kr-25-otp-ogranichenie-ramera-fajla-v-linux","title":{"rendered":"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/70434b41e923b3b46bcdff1ab7e03937.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\nV tem \u010dlanku bomo re\u0161ili 25. nalogo s spletne strani <noindex><a rel=\"nofollow\" href=\"https:\/\/pwnable.kr\/index.php\">pwnable.kr<\/a><\/noindex>.<\/p>\n<p><b class=\"spoiler_title\">Organizacione informacije<\/b>Posebno za one koji \u017eele saznati ne\u0161to novo i razvijati se u bilo kojoj od oblasti informacionih i ra\u010dunarskih sigurnosti, pisat \u0107u i pri\u010dati o sljede\u0107im kategorijama:<\/p>\n<ul>\n<li>PWN;<\/li>\n<li>kriptografija (Crypto);<\/li>\n<li>mre\u017ene tehnologije (Network);<\/li>\n<li>obrnuto in\u017eenjerstvo (Reverse Engineering);<\/li>\n<li>steganografija (Stegano);<\/li>\n<li>tra\u017eenje i eksploatacija WEB-ranljivosti.<\/li>\n<\/ul>\n<p>\nPored toga, podijelit \u0107u svoje iskustvo u ra\u010dunarstvu, analizi malvara i firmware-a, napadima na be\u017ei\u010dne mre\u017ee i lokalne ra\u010dunarske mre\u017ee, provo\u0111enju pentestova i pisanju eksploita.<br \/>\n<noindex><a rel=\"nofollow\" name=\"habracut\"><\/a><\/noindex><br \/>\nKako biste mogli saznati o novim \u010dlancima, softveru i drugim informacijama, stvorio sam <noindex><a rel=\"nofollow\" href=\"https:\/\/t.me\/RalfHackerChannel\">kanal na Telegramu<\/a><\/noindex> in <noindex><a rel=\"nofollow\" href=\"https:\/\/t.me\/RalfHackerPublicChat\">grupu za raspravu o svim pitanjima<\/a><\/noindex> u oblasti IiiK. Tako\u0111e, va\u0161e li\u010dne molbe, pitanja, prijedlozi i preporuke <noindex><a rel=\"nofollow\" href=\"https:\/\/t.me\/hackerralf8\">razmotri\u0107u li\u010dno i odgovarati svima<\/a><\/noindex>.<\/p>\n<p>Sve informacije su predstavljene isklju\u010divo u obrazovne svrhe. Autor ovog dokumenta ne snosi nikakvu odgovornost za bilo kakvu \u0161tetu koja mo\u017ee nastati kao rezultat kori\u0161\u0107enja znanja i metoda ste\u010denih prou\u010davanjem ovog dokumenta.<\/p>\n<h2>Re\u0161itev naloge otp<\/h2>\n<p>\nNadaljujemo z drugim delom. Takoj bom povedal, da je te\u017eji od prvega, vendar tokrat ne nudijo izvorne kode programa. Ne pozabite na razpravo tukaj (https:\/\/t.me\/RalfHackerPublicChat) in tukaj (https:\/\/t.me\/RalfHackerChannel). Za\u010dnimo.<\/p>\n<p>Kliknemo na ikono z oznako otp. Pridobimo naslov in vrata za povezavo.<\/p>\n<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/fec98a1c755c36ba1a7117bfc5154611.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nPove\u017eemo se in si ogledamo stre\u017enik.<\/p>\n<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/71983f5701fe2b1366cebfb0d2d57f74.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nZastavo, ki je ne moremo prebrati, program in njegova izvorna koda. Oglejmo si izvorno kodo.<\/p>\n<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/63e409cd939f41db29ee5c1edfa107a0.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nRazberimo ga. Program sprejema geslo kot argument.<\/p>\n<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/5eb6bccb7ed4b82fdd01e24854c2c953.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nNato se v spremenljivko otp shrani naklju\u010dnih 16 bajtov.<\/p>\n<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/c1420a16c9721a8c87fb86277674f0f2.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nV mapi tmp se ustvari datoteka z naklju\u010dnim imenom (prvih 8 bajtov otp) in vanjo se zapi\u0161e naklju\u010dnih 8 bajtov (drugih 8 bajtov otp).<\/p>\n<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/d6fcc612f6cddbff338fff0aaf9b73a1.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nNekako se prebere vrednost te ustvarjene datoteke in se primerja z vne\u0161enim geslom.<\/p>\n<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/42302a748b7cd57a6337be00eab2c47b.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nTukaj je prisotna ranljivost. Ta je v vmesnem shranjevanju generirane \u0161tevilke v datoteko. Lahko omejimo velikost datoteke, na primer na 0, tako da bo pri zapisovanju in branju z geslom pri\u0161lo do primerjave z 0. To lahko storimo tako.<\/p>\n<pre><code class=\"bash\"># ulimit -f 0<\/code><\/pre>\n<p>\n<img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/3af83c20d1de7435b0f40a36c8187ff0.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nZdaj za\u017eenimo program.<\/p>\n<p><img decoding=\"async\" alt=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/a289bd59a22aa495fe6407c3c8ff0416.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nPrejeli smo napako. Ni\u010d hudega, saj jo lahko obdelamo s pomo\u010djo istega Pythona.<\/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=\"Re\u0161evanje naloge z pwnable.kr 25 \u2014 otp. Omejitev velikosti datoteke v Linuxu\" src=\"\/wp-content\/uploads\/2019\/10\/b8513f020879d5e5ee957e1bc137b61a.png\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nPrejeli smo zastavo in lahkih 100 to\u010dk. Nato nadaljujemo: v naslednjem \u010dlanku se bomo dotaknili Weba. Pridru\u017eite se nam v <noindex><a rel=\"nofollow\" href=\"https:\/\/t.me\/RalfHackerChannel\">Telegram<\/a><\/noindex>.<br \/>\n<br \/>Izvor: <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\/sl\/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=\"sl_SI\" \/>\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\/sl\/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\udd47Re\u0161itev naloge s pwnable.kr 25 \u2014 otp. 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