{"id":100784,"date":"2021-07-17T22:22:35","date_gmt":"2021-07-17T20:22:35","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare"},"modified":"2021-07-17T22:22:35","modified_gmt":"2021-07-17T20:22:35","slug":"uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare","status":"publish","type":"post","link":"https:\/\/prohoster.info\/hr\/blog\/news\/uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare","title":{"rendered":"Ranljivost u cdnjs koja omogu\u0107ava izvr\u0161avanje koda na Cloudflare serverima","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

U mre\u017ei za isporuku sadr\u017eaja cdnjs koju pru\u017ea tvrtka Cloudflare, namijenjenoj ubrzavanju isporuke JavaScript biblioteka, otkrivena je kriti\u010dna ranjivost koja omogu\u0107uje izvr\u0161avanje proizvoljnog koda na CDN serverima. Opasnost ovog problema je dodatno poja\u010dana jer otprilike 12,7% svih web stranica koristi ovu uslugu za u\u010ditavanje JavaScript biblioteka, a kompromitacija infrastrukture omogu\u0107uje zamjenu biblioteka koje se dostavljaju sa bilo koje od tih stranica. <\/p>\n

Servis cdnjs omogu\u0107uje preuzimanje paketa iz Gita ili NPM repozitorija, nakon \u010dega svakom webu pru\u017ea besplatan pristup mre\u017ei za isporuku sadr\u017eaja Cloudflare za ubrzanje u\u010ditavanja JavaScript biblioteka. Istra\u017euju\u0107i kod komponenti cdnjs objavljenih na GitHubu, otkriveno je da se za raspakivanje NPM paketa u tgz arhivama koristi standardni modul archive\/tar na jeziku Go, koji isporu\u010duje popis datoteka kakve jesu, bez normalizacije putanja. U slu\u010daju kada skript raspakira sadr\u017eaj na temelju dostavljenog popisa, prisutnost datoteka u arhivu poput \"..\\..\\..\\..\\..\\..\\..\\tmp\\test\" mo\u017ee dovesti do prepisivanja proizvoljnih datoteka u sustavu, ovisno o pravima pristupa. <\/p>\n

Pretpostavljeno je da bi napada\u010d mogao podnijeti zahtjev za dodavanje svoje biblioteke u cdnjs i u\u010ditati u NPM repozitorij posebno pripremljenu arhivu koja sadr\u017ei datoteke s simbolima \"..\\\" u putu. Na serverima cdnjs povremeno se izvr\u0161ava operacija \"autoupdate\", tijekom koje obrada preuzima nove verzije predlo\u017eene biblioteke i raspakira sadr\u017eaj. Pomo\u0107u datoteka s putanjama \"..\\\" napada\u010d mo\u017ee posti\u0107i prepisivanje datoteka sa skriptama servisa i izvr\u0161avanje vlastitog koda na serveru<\/a> na kojem je izvr\u0161avano raspakiravanje. <\/p>\n

U slu\u010daju u\u010ditavanja a\u017euriranja iz Git-a utvr\u0111eno je da obrada koja preuzima a\u017euriranja nije uzimala u obzir simboli\u010dne veze prilikom kopiranja datoteka iz Git-a. Ova osobina omogu\u0107ila je \u010ditanje bilo kojih datoteka s poslu\u017eitelja<\/a> dodavanjem simboli\u010dnih veza u Git. <\/p>\n

Eksperimenti s demonstracijom hakiranja cdnjs za osvajanje nagrade na HackerOne odlu\u010deno je zapo\u010deti provjerom hipoteze o \u010ditanju datoteka. U Git repozitorij umre\u017eenih putem CDN-a JavaScript biblioteke dodana je simboli\u010dka veza test.js koja upu\u0107uje na datoteku \/proc\/self\/maps. Nakon objave nove verzije biblioteke, obrada a\u017euriranja obradila je ovaj repozitorij i objavila navedenu datoteku na cdnjs (test.js je stvoren kao simboli\u010dka veza i prilikom zahtjeva za ovom datotekom vra\u0107ao je sadr\u017eaj \/proc\/self\/maps). <\/p>\n

Zamjenom simboli\u010dke veze s datotekom \/proc\/self\/environ autor istra\u017eivanja primijetio je da unutar predanih podataka postoje vrijednosti varijabli okru\u017eenja GITHUB_REPO_API_KEY i WORKERS_KV_API_TOKEN. U prvoj varijabli pohranjen je klju\u010d za API za pristup s pravima pisanja u repozitorij robocdnjs na GitHubu. U drugoj varijabli pohranjen je token za KV skladi\u0161te u cdnjs. Iskoristiv\u0161i dobivene informacije, napada\u010d je mogao izvr\u0161iti promjene u cdnjs i potpuno kompromitirati infrastrukturu.
\n
Izvor: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u043f\u0440\u0435\u0434\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u043c\u043e\u0439 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0435\u0439 Cloudflare \u0441\u0435\u0442\u0438 \u0434\u043e\u0441\u0442\u0430\u0432\u043a\u0438 \u043a\u043e\u043d\u0442\u0435\u043d\u0442\u0430 cdnjs, \u043f\u0440\u0435\u0434\u043d\u0430\u0437\u043d\u0430\u0447\u0435\u043d\u043d\u043e\u0439 \u0434\u043b\u044f \u0443\u0441\u043a\u043e\u0440\u0435\u043d\u0438\u044f \u0434\u043e\u0441\u0442\u0430\u0432\u043a\u0438 JavaScript-\u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u043a\u0440\u0438\u0442\u0438\u0447\u0435\u0441\u043a\u0430\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u0432\u044b\u043f\u043e\u043b\u043d\u0438\u0442\u044c \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u043b\u044c\u043d\u044b\u0439 \u043a\u043e\u0434 \u043d\u0430 \u0441\u0435\u0440\u0432\u0435\u0440\u0430\u0445 CDN. \u041e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u044c \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0443\u0441\u0443\u0433\u0443\u0431\u043b\u044f\u0435\u0442\u0441\u044f \u0442\u0435\u043c, \u0447\u0442\u043e \u0434\u043b\u044f \u0437\u0430\u0433\u0440\u0443\u0437\u043a\u0438 JavaScript-\u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a \u0441\u0435\u0440\u0432\u0438\u0441\u043e\u043c \u043f\u043e\u043b\u044c\u0437\u0443\u0435\u0442\u0441\u044f \u043e\u043a\u043e\u043b\u043e 12.7% \u0432\u0441\u0435\u0445 \u0441\u0430\u0439\u0442\u043e\u0432 \u0432 \u0438\u043d\u0442\u0435\u0440\u043d\u0435\u0442\u0435 \u0438 \u043a\u043e\u043c\u043f\u0440\u043e\u043c\u0435\u0442\u0430\u0446\u0438\u044f \u0438\u043d\u0444\u0440\u0430\u0441\u0442\u0440\u0443\u043a\u0442\u0443\u0440\u044b \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0435\u0442 \u043f\u043e\u0434\u043c\u0435\u043d\u0438\u0442\u044c \u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a\u0438, \u043e\u0442\u0434\u0430\u0432\u0430\u0435\u043c\u044b\u0435 \u043b\u044e\u0431\u044b\u043c \u0438\u0437 \u044d\u0442\u0438\u0445 \u0441\u0430\u0439\u0442\u043e\u0432. \u0421\u0435\u0440\u0432\u0438\u0441 cdnjs \u043e\u0441\u0443\u0449\u0435\u0441\u0442\u0432\u043b\u044f\u0435\u0442 \u0437\u0430\u0433\u0440\u0443\u0437\u043a\u0443 \u043f\u0430\u043a\u0435\u0442\u043e\u0432 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