V j\u00e1d\u0159e 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 flagem O_RDONLY nebo um\u00edst\u011bn\u00fdch na souborov\u00fdch syst\u00e9mech p\u0159ipojen\u00fdch v re\u017eimu pouze pro \u010dten\u00ed. Z praktick\u00e9ho hlediska lze zranitelnost vyu\u017e\u00edt pro vkl\u00e1d\u00e1n\u00ed k\u00f3du do libovoln\u00fdch proces\u016f nebo 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 k dispozici prototyp exploit\u016f. <\/p>\n
Probl\u00e9m byl ozna\u010den k\u00f3dov\u00fdm n\u00e1zvem Dirty Pipe, obdobn\u011b jako kritick\u00e1 zranitelnost Dirty COW, kter\u00e1 byla odhalena v roce 2016. Je zd\u016frazn\u011bno, \u017ee z hlediska nebezpe\u010dnosti je Dirty Pipe na stejn\u00e9 \u00farovni jako Dirty COW, ale je mnohem jednodu\u0161\u0161\u00ed pro exploataci. Zranitelnost byla odhalena p\u0159i zkoum\u00e1n\u00ed st\u00ed\u017enost\u00ed na ob\u010dasn\u00e9 po\u0161kozen\u00ed soubor\u016f stahovan\u00fdch po s\u00edti v syst\u00e9mu stahuj\u00edc\u00edm komprimovan\u00e9 archivy z log-serveru (37 po\u0161kozen\u00ed za 3 m\u011bs\u00edce v zat\u00ed\u017een\u00e9m syst\u00e9mu), p\u0159i jejich\u017e p\u0159\u00edprav\u011b byla pou\u017eita operace splice() a anonymn\u00ed kan\u00e1ly. <\/p>\n
Zranitelnost se projevuje od j\u00e1dra Linux 5.8, vydan\u00e9ho v srpnu 2020, co\u017e znamen\u00e1, \u017ee 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\u00fdch v\u011btv\u00edch, ale nen\u00ed vylou\u010deno, \u017ee probl\u00e9m zp\u016fsobuj\u00edc\u00ed zm\u011bna byla do nich zp\u011btn\u011b integrov\u00e1na (p\u0159esn\u00e9 \u00fadaje zat\u00edm nejsou). Sledovat publikaci aktualizac\u00ed 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 je tak\u00e9 zahrnuta v j\u00e1d\u0159e pou\u017e\u00edvan\u00e9m na platform\u011b Android. <\/p>\n
Zranitelnost je zp\u016fsobena absenc\u00ed inicializace hodnoty \u00abbuf->flags\u00bb v k\u00f3du funkc\u00ed copy_page_to_iter_pipe() a push_pipe(), p\u0159i\u010dem\u017e pam\u011b\u0165 p\u0159i p\u0159id\u011blov\u00e1n\u00ed struktury nen\u00ed vymaz\u00e1na, a p\u0159i ur\u010dit\u00fdch manipulac\u00edch s anonymn\u00edmi kan\u00e1ly m\u016f\u017ee v \u00abbuf->flags\u00bb skon\u010dit hodnota z jin\u00e9 operace. Vyu\u017eit\u00edm t\u00e9to vlastnosti m\u016f\u017ee neprivilegovan\u00fd lok\u00e1ln\u00ed u\u017eivatel dos\u00e1hnout toho, \u017ee se ve flagu objev\u00ed hodnota PIPE_BUF_FLAG_CAN_MERGE, kter\u00e1 umo\u017e\u0148uje organizaci p\u0159eps\u00e1n\u00ed dat ve str\u00e1nkov\u00e9m cache jednoduch\u00fdm z\u00e1pisem nov\u00fdch dat do speci\u00e1ln\u011b p\u0159ipraven\u00e9ho anonymn\u00edho kan\u00e1lu (pipe). <\/p>\n
Pro \u00fatok mus\u00ed b\u00fdt c\u00edlov\u00fd soubor p\u0159\u00edstupn\u00fd pro \u010dten\u00ed, p\u0159i\u010dem\u017e, proto\u017ee p\u0159i z\u00e1pisu do pipe nejsou kontrolov\u00e1na opr\u00e1vn\u011bn\u00ed, m\u016f\u017ee b\u00fdt v\u00fdm\u011bna ve str\u00e1nkov\u00e9m cache provedena tak\u00e9 pro soubory nach\u00e1zej\u00edc\u00ed se v odd\u00edlech, kter\u00e9 jsou p\u0159ipojeny pouze pro \u010dten\u00ed (nap\u0159\u00edklad pro soubory na CD-ROM). Po v\u00fdm\u011bn\u011b informac\u00ed ve str\u00e1nkov\u00e9m cache proces p\u0159i \u010dten\u00ed dat ze souboru obdr\u017e\u00ed ne skute\u010dn\u00e1, ale podvr\u017een\u00e1 data. <\/p>\n
Exploatace spo\u010d\u00edv\u00e1 ve vytvo\u0159en\u00ed anonymn\u00edho kan\u00e1lu a jeho napln\u011bn\u00ed libovoln\u00fdmi daty s c\u00edlem dos\u00e1hnout nastaven\u00ed p\u0159\u00edznaku PIPE_BUF_FLAG_CAN_MERGE ve v\u0161ech souvisej\u00edc\u00edch kruhov\u00fdch struktur\u00e1ch. Pot\u00e9 jsou data \u010dtena z kan\u00e1lu, ale p\u0159\u00edznak z\u016fst\u00e1v\u00e1 nastaven ve v\u0161ech instancech struktury pipe_buffer v kruhov\u00fdch struktur\u00e1ch pipe_inode_info. N\u00e1sledn\u011b se provede vol\u00e1n\u00ed splice() pro \u010dten\u00ed dat z c\u00edlov\u00e9ho souboru do anonymn\u00edho kan\u00e1lu, po\u010d\u00ednaje po\u017eadovan\u00fdm posunem. P\u0159i z\u00e1pisu dat do tohoto anonymn\u00edho kan\u00e1lu budou kv\u016fli nastaven\u00e9mu p\u0159\u00edznaku PIPE_BUF_FLAG_CAN_MERGE data ve str\u00e1nkov\u00e9m cache p\u0159eps\u00e1na, m\u00edsto aby byl vytvo\u0159en nov\u00fd instance struktury pipe_buffer. \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\udd47Zranitelnost v j\u00e1dru Linux, kter\u00e1 umo\u017e\u0148uje zmanipulovat soubory 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Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"