Ve Netfilteru, subsyst\u00e9mu j\u00e1dra Linux, kter\u00fd se pou\u017e\u00edv\u00e1 k filtrov\u00e1n\u00ed a modifikaci s\u00ed\u0165ov\u00fdch paket\u016f, byla zji\u0161t\u011bna zranitelnost (CVE-2021-22555), kter\u00e1 umo\u017e\u0148uje m\u00edstn\u00edmu u\u017eivateli z\u00edskat opr\u00e1vn\u011bn\u00ed roota v syst\u00e9mu, a to i v izolovan\u00e9m kontejneru. Byla p\u0159ipravena funk\u010dn\u00ed prototyp exploitu pro testov\u00e1n\u00ed, kter\u00fd obch\u00e1z\u00ed ochrann\u00e9 mechanismy KASLR, SMAP a SMEP. V\u00fdzkumn\u00edk, jen\u017e zranitelnost odhalil, obdr\u017eel od spole\u010dnosti Google odm\u011bnu ve v\u00fd\u0161i 20 000 dolar\u016f za zji\u0161t\u011bn\u00ed metody obch\u00e1zen\u00ed izolace kontejner\u016f Kubernetes v clusteru kCTF. <\/p>\n
Probl\u00e9m se projevuje od j\u00e1dra 2.6.19, vydan\u00e9ho p\u0159ed 15 lety, a je zp\u016fsoben chybou v obslu\u017en\u00fdch rutin\u00e1ch IPT_SO_SET_REPLACE a IP6T_SO_SET_REPLACE, co\u017e vede k p\u0159ete\u010den\u00ed z\u00e1sobn\u00edku p\u0159i odes\u00edl\u00e1n\u00ed speci\u00e1ln\u011b form\u00e1tovan\u00fdch parametr\u016f prost\u0159ednictv\u00edm syst\u00e9mu setsockopt v re\u017eimu compat. Za norm\u00e1ln\u00edch okolnost\u00ed m\u016f\u017ee vol\u00e1n\u00ed compat_setsockopt() prov\u00e9st pouze u\u017eivatel root, ale pot\u0159ebn\u00e1 opr\u00e1vn\u011bn\u00ed pro proveden\u00ed \u00fatoku mohou b\u00fdt tak\u00e9 z\u00edsk\u00e1na neprivilegovan\u00fdm u\u017eivatelem v syst\u00e9mech s povolenou podporou prostor\u016f identit u\u017eivatel\u016f (user namespaces). <\/p>\n
U\u017eivatel m\u016f\u017ee vytvo\u0159it kontejner s odd\u011blen\u00fdm u\u017eivatelem root a z n\u011bj vyu\u017e\u00edt zranitelnost. Nap\u0159\u00edklad, \u201eu\u017eivatelsk\u00e9 prostory\u201c jsou ve v\u00fdchoz\u00edm nastaven\u00ed aktivov\u00e1ny v Ubuntu a Fedo\u0159e, ale nejsou povoleny v Debi\u00e1nu a RHEL. Z\u00e1plata opravuj\u00edc\u00ed zranitelnost byla p\u0159ijata do j\u00e1dra Linuxu 13. dubna. Aktualizace bal\u00ed\u010dk\u016f ji\u017e byla p\u0159ipravena projekty Debian, Arch Linux a Fedora. V Ubuntu, RHEL a SUSE jsou aktualizace ve f\u00e1zi p\u0159\u00edpravy. <\/p>\n
Probl\u00e9m nast\u00e1v\u00e1 ve funkci xt_compat_target_from_user() kv\u016fli nespr\u00e1vn\u00e9mu v\u00fdpo\u010dtu velikosti pam\u011bti p\u0159i ukl\u00e1d\u00e1n\u00ed struktur j\u00e1dra po p\u0159evodu z 32- na 64bitov\u00e9 zobrazen\u00ed. Chyba umo\u017e\u0148uje zapsat \u010dty\u0159i nulov\u00e9 bajty na jak\u00e9koli m\u00edsto mimo vyhrazen\u00fd buffer, omezen\u00e9 posunem 0x4C. T\u00e9to mo\u017enosti bylo dost k tomu, aby se vytvo\u0159il exploit, kter\u00fd umo\u017enil z\u00edskat pr\u00e1va root \u2013 prost\u0159ednictv\u00edm vy\u010di\u0161t\u011bn\u00ed ukazatele m_list->next ve struktu\u0159e msg_msg se vytvo\u0159ily podm\u00ednky pro p\u0159\u00edstup k dat\u016fm po jejich uvoln\u011bn\u00ed (use-after-free), co\u017e bylo pot\u00e9 pou\u017eito k z\u00edsk\u00e1n\u00ed informac\u00ed o adres\u00e1ch a zm\u011bn\u011b dal\u0161\u00edch struktur pomoc\u00ed manipulace se syst\u00e9mov\u00fdm vol\u00e1n\u00edm msgsnd(). \u0412 Netfilter, \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u0435 \u044f\u0434\u0440\u0430 Linux, \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u0435\u043c\u043e\u0439 \u0434\u043b\u044f \u0444\u0438\u043b\u044c\u0442\u0440\u0430\u0446\u0438\u0438 \u0438 \u043c\u043e\u0434\u0438\u0444\u0438\u043a\u0430\u0446\u0438\u0438 \u0441\u0435\u0442\u0435\u0432\u044b\u0445 \u043f\u0430\u043a\u0435\u0442\u043e\u0432, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2021-22555), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043b\u043e\u043a\u0430\u043b\u044c\u043d\u043e\u043c\u0443 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u044e \u043f\u043e\u043b\u0443\u0447\u0438\u0442\u044c \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0438 root \u0432 \u0441\u0438\u0441\u0442\u0435\u043c\u0435, \u0432 \u0442\u043e\u043c \u0447\u0438\u0441\u043b\u0435 \u043d\u0430\u0445\u043e\u0434\u044f\u0441\u044c \u0432 \u0438\u0437\u043e\u043b\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u043e\u043c \u043a\u043e\u043d\u0442\u0435\u0439\u043d\u0435\u0440\u0435. \u0414\u043b\u044f \u0442\u0435\u0441\u0442\u0438\u0440\u043e\u0432\u0430\u043d\u0438\u044f \u043f\u043e\u0434\u0433\u043e\u0442\u043e\u0432\u043b\u0435\u043d \u0440\u0430\u0431\u043e\u0447\u0438\u0439 \u043f\u0440\u043e\u0442\u043e\u0442\u0438\u043f \u044d\u043a\u0441\u043f\u043b\u043e\u0438\u0442\u0430, \u043e\u0431\u0445\u043e\u0434\u044f\u0449\u0438\u0439 \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u044b \u0437\u0430\u0449\u0438\u0442\u044b KASLR, SMAP \u0438 SMEP. \u0418\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u044c, \u0432\u044b\u044f\u0432\u0438\u0432\u0448\u0438\u0439 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c, \u043f\u043e\u043b\u0443\u0447\u0438\u043b \u043e\u0442 Google \u0432\u043e\u0437\u043d\u0430\u0433\u0440\u0430\u0436\u0434\u0435\u043d\u0438\u0435, \u0440\u0430\u0437\u043c\u0435\u0440\u043e\u043c 20 \u0442\u044b\u0441\u044f\u0447 \u0434\u043e\u043b\u043b\u0430\u0440\u043e\u0432, \u0437\u0430 […]<\/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-100767","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 subsyst\u00e9mu j\u00e1dra Linux Netfilter | ProHoster","description":"V Netfilter, subsyst\u00e9mu j\u00e1dra Linux pou\u017e\u00edvan\u00e9mu k filtrov\u00e1n\u00ed a modifikaci s\u00ed\u0165ov\u00fdch paket\u016f, byla zji\u0161t\u011bna zranitelnost (CVE-2021-22555), kter\u00e1 umo\u017e\u0148uje lok\u00e1ln\u00edmu u\u017eivateli z\u00edskat pr\u00e1va root v syst\u00e9mu, 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Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"