{"id":103489,"date":"2022-03-07T21:36:38","date_gmt":"2022-03-07T19:36:38","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-yadre-linux-pozvolyayushhaya-iskazit-fajly-dostupnye-tolko-dlya-chteniya"},"modified":"2022-03-07T21:36:38","modified_gmt":"2022-03-07T19:36:38","slug":"uyazvimost-v-yadre-linux-pozvolyayushhaya-iskazit-fajly-dostupnye-tolko-dlya-chteniya","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sl\/blog\/news\/uyazvimost-v-yadre-linux-pozvolyayushhaya-iskazit-fajly-dostupnye-tolko-dlya-chteniya","title":{"rendered":"Ranjivost u Linux jezgru koja omogu\u0107ava izmena datoteka dostupnih samo za \u010ditanje","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V jedru Linux byla odhalena zranitelnost (CVE-2022-0847), kter\u00e1 umo\u017e\u0148uje p\u0159epsat obsah str\u00e1nkov\u00e9ho cache pro jak\u00e9koli soubory, v\u010detn\u011b t\u011bch, kter\u00e9 jsou otev\u0159eny v re\u017eimu pouze pro \u010dten\u00ed s p\u0159\u00edznakem O_RDONLY nebo um\u00edst\u011bn\u00e9 v souborov\u00fdch syst\u00e9mech p\u0159ipojen\u00fdch v re\u017eimu pouze pro \u010dten\u00ed. Z praktick\u00e9ho hlediska m\u016f\u017ee b\u00fdt zranitelnost vyu\u017eita k vkl\u00e1d\u00e1n\u00ed k\u00f3du do libovoln\u00fdch proces\u016f nebo k po\u0161kozen\u00ed dat v otev\u00edran\u00fdch souborech. Nap\u0159\u00edklad je mo\u017en\u00e9 zm\u011bnit obsah souboru authorized_keys pro proces sshd. Pro testov\u00e1n\u00ed je dostupn\u00fd prototyp exploit. <\/p>\n

Probl\u00e9m byl nazv\u00e1n Dirty Pipe, podle kritick\u00e9 zranitelnosti Dirty COW z roku 2016. Uv\u00e1d\u00ed se, \u017ee z hlediska nebezpe\u010dnosti je Dirty Pipe na stejn\u00e9 \u00farovni jako Dirty COW, av\u0161ak je mnohem snaz\u0161\u00ed k exploataci. Zranitelnost byla odhalena p\u0159i anal\u00fdze st\u00ed\u017enost\u00ed na ob\u010dasn\u00e9 po\u0161kozen\u00ed soubor\u016f stahovan\u00fdch p\u0159es s\u00ed\u0165 v syst\u00e9mu, kter\u00fd na\u010d\u00edtal komprimovan\u00e9 archivy z log-serveru (37 po\u0161kozen\u00ed b\u011bhem 3 m\u011bs\u00edc\u016f na p\u0159et\u00ed\u017een\u00e9m syst\u00e9mu), p\u0159i jejich\u017e p\u0159\u00edprav\u011b byla pou\u017eita operace splice() a nepojmenovan\u00e9 roury. <\/p>\n

Zranitelnost se projevuje od j\u00e1dra Linux 5.8, vydan\u00e9ho v srpnu 2020, tedy je p\u0159\u00edtomna v Debianu 11, ale net\u00fdk\u00e1 se z\u00e1kladn\u00edho j\u00e1dra v Ubuntu 20.04 LTS. J\u00e1dra RHEL 8.x a openSUSE\/SUSE 15 jsou p\u016fvodn\u011b zalo\u017eena na star\u0161\u00edch v\u011btv\u00edch, nicm\u00e9n\u011b nelze vylou\u010dit, \u017ee problematick\u00e1 zm\u011bna byla p\u0159enesena do t\u011bchto verz\u00ed (p\u0159esn\u00e9 \u00fadaje zat\u00edm nejsou k dispozici). Sledovat aktualizace bal\u00ed\u010dk\u016f v distribuc\u00edch lze na t\u011bchto str\u00e1nk\u00e1ch: Debian, SUSE, Ubuntu, RHEL, Fedora, Gentoo, Arch Linux. Oprava zranitelnosti byla navr\u017eena v verz\u00edch 5.16.11, 5.15.25 a 5.10.102. Oprava byla tak\u00e9 zahrnuta do j\u00e1dra pou\u017e\u00edvan\u00e9ho v platform\u011b Android. <\/p>\n

Ranljivost je povzro\u010dena zaradi pomanjkanja inicializacije vrednosti «buf->flags» v kodi funkcij copy_page_to_iter_pipe() in push_pipe(), kar pomeni, da se ob alokaciji strukture pomnilnik ne o\u010disti, in pri dolo\u010denih manipulacijah z neimenovanimi kanali lahko v «buf->flags» pride do vrednosti iz druge operacije. Z uporabo te lastnosti lahko neprivilegirani lokalni uporabnik dose\u017ee, da se v zastavici pojavi vrednost PIPE_BUF_FLAG_CAN_MERGE, ki omogo\u010da ponovni zapis podatkov v stran\u010dni predpomnilnik prek preproste zapisane nove vsebine v posebno pripravljena neimenovana cev (pipe). <\/p>\n

Za napad je ciljni datoteka mora biti dostopna za branje, pri \u010demer pa za zapis v cev (pipe) pravice dostopa niso preverjene, saj lahko zamenjava v predpomnilniku strani poteka tudi za datoteke v razdelkih, montiranih samo za branje (na primer datoteke z CD-ROM-a). Po zamenjavi informacij v predpomnilniku strani bo proces pri branju podatkov iz datoteke prejel ne dejanske, temve\u010d zamenjane podatke. <\/p>\n

Izvedba se zmanj\u0161a na ustvarjanje neimenovane cevi in njeno polnjenje z naklju\u010dnimi podatki, da se dose\u017ee nastavitev zastavice PIPE_BUF_FLAG_CAN_MERGE v vseh povezanih obro\u010dnih strukturah. Nato se podatki berejo iz cevi, toda zastavica ostaja nastavljena v vseh instancah strukture pipe_buffer v obro\u010dnih strukturah pipe_inode_info. Sledi klic splice() za branje podatkov iz ciljne datoteke v neimenovano cev, pri \u010demer se za\u010dne z zahtevano offsetom. Pri zapisovanju podatkov v to neimenovano cev se zaradi nastavljene zastavice PIPE_BUF_FLAG_CAN_MERGE podatki v predpomnilniku strani prepi\u0161ejo, namesto da bi ustvarili novo instanco strukture pipe_buffer.
\n
Izvor: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u044f\u0434\u0440\u0435 Linux \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2022-0847), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043f\u0435\u0440\u0435\u0437\u0430\u043f\u0438\u0441\u0430\u0442\u044c \u0441\u043e\u0434\u0435\u0440\u0436\u0438\u043c\u043e\u0435 \u0441\u0442\u0440\u0430\u043d\u0438\u0447\u043d\u043e\u0433\u043e \u043a\u044d\u0448\u0430 \u0434\u043b\u044f \u043b\u044e\u0431\u044b\u0445 \u0444\u0430\u0439\u043b\u043e\u0432, \u0432 \u0442\u043e\u043c \u0447\u0438\u0441\u043b\u0435 \u043d\u0430\u0445\u043e\u0434\u044f\u0449\u0438\u0445\u0441\u044f \u0432 \u0440\u0435\u0436\u0438\u043c\u0435 \u0442\u043e\u043b\u044c\u043a\u043e \u0434\u043b\u044f \u0447\u0442\u0435\u043d\u0438\u044f, \u043e\u0442\u043a\u0440\u044b\u0442\u044b\u0445 \u0441 \u0444\u043b\u0430\u0433\u043e\u043c O_RDONLY \u0438\u043b\u0438 \u0440\u0430\u0437\u043c\u0435\u0449\u0451\u043d\u043d\u044b\u0445 \u0432 \u0444\u0430\u0439\u043b\u043e\u0432\u044b\u0445 \u0441\u0438\u0441\u0442\u0435\u043c\u0430\u0445, \u043f\u0440\u0438\u043c\u043e\u043d\u0442\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u044b\u0445 \u0432 \u0440\u0435\u0436\u0438\u043c\u0435 \u0442\u043e\u043b\u044c\u043a\u043e \u0434\u043b\u044f \u0447\u0442\u0435\u043d\u0438\u044f. \u0421 \u043f\u0440\u0430\u043a\u0442\u0438\u0447\u0435\u0441\u043a\u043e\u0439 \u0441\u0442\u043e\u0440\u043e\u043d\u044b, \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043c\u043e\u0436\u0435\u0442 \u043f\u0440\u0438\u043c\u0435\u043d\u044f\u0442\u044c\u0441\u044f \u0434\u043b\u044f \u043f\u043e\u0434\u0441\u0442\u0430\u043d\u043e\u0432\u043a\u0438 \u043a\u043e\u0434\u0430 \u0432 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u043b\u044c\u043d\u044b\u0435 \u043f\u0440\u043e\u0446\u0435\u0441\u0441\u044b \u0438\u043b\u0438 \u0438\u0441\u043a\u0430\u0436\u0435\u043d\u0438\u044f \u0434\u0430\u043d\u043d\u044b\u0445 \u0432 \u043e\u0442\u043a\u0440\u044b\u0432\u0430\u0435\u043c\u044b\u0445 […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-103489","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Ranljivost v jedru Linuxa, ki omogo\u010da izkrivljanje datotek, dostopnih samo za branje | ProHoster","description":"V jedru Linuxa je bila odkrita ranljivost (CVE-2022-0847), ki omogo\u010da prepisovanje vsebine predpomnilnika strani za katerekoli datoteke, vklju\u010dno tiste, ki so v na\u010dinu samo za branje, odprte z zastavico O_RDONLY ali na 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