{"id":103483,"date":"2022-03-06T15:36:45","date_gmt":"2022-03-06T13:36:47","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-cgroups-v1-pozvolyayushhaya-vyjti-iz-izolirovannogo-kontejnera"},"modified":"2022-03-06T15:36:45","modified_gmt":"2022-03-06T13:36:47","slug":"uyazvimost-v-cgroups-v1-pozvolyayushhaya-vyjti-iz-izolirovannogo-kontejnera","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/uyazvimost-v-cgroups-v1-pozvolyayushhaya-vyjti-iz-izolirovannogo-kontejnera","title":{"rendered":"Zranitelnost v cgroups v1, kter\u00e1 umo\u017e\u0148uje uniknout z izolovan\u00e9ho kontejneru","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Byly odhaleny detaily zranitelnosti (CVE-2022-0492) v implementaci mechanismu omezen\u00ed zdroj\u016f cgroups v1 v j\u00e1d\u0159e Linux, kterou by bylo mo\u017en\u00e9 vyu\u017e\u00edt k \u00faniku z izolovan\u00fdch kontejner\u016f. Probl\u00e9m se projevuje od j\u00e1dra Linux 2.6.24 a byl vy\u0159e\u0161en ve verz\u00edch jader 5.16.12, 5.15.26, 5.10.97, 5.4.177, 4.19.229, 4.14.266 a 4.9.301. Sledovat vyd\u00e1n\u00ed aktualizac\u00ed bal\u00ed\u010dk\u016f ve distribuc\u00edch lze na t\u011bchto str\u00e1nk\u00e1ch: Debian, SUSE, Ubuntu, RHEL, Fedora, Gentoo, Arch Linux. <\/p>\n

Zranitelnost je zp\u016fsobena logickou chybou v zpracov\u00e1n\u00ed soubor\u016f release_agent, kv\u016fli kter\u00e9 se p\u0159i spu\u0161t\u011bn\u00ed zpracovatele s pln\u00fdm souborem pr\u00e1v neprov\u00e1d\u011bly n\u00e1le\u017eit\u00e9 kontroly. Soubor release_agent se pou\u017e\u00edv\u00e1 k ur\u010den\u00ed programu, kter\u00fd j\u00e1dro spou\u0161t\u00ed p\u0159i ukon\u010den\u00ed procesu v cgroup. Tento program se spou\u0161t\u00ed s pr\u00e1vy root a se v\u0161emi \u201ecapabilities\u201c v ko\u0159enov\u00e9m prostoru n\u00e1zv\u016f. P\u0159edpokl\u00e1dalo se, \u017ee p\u0159\u00edstup k nastaven\u00ed release_agent m\u00e1 pouze administr\u00e1tor, ale ve skute\u010dnosti kontroly spo\u010d\u00edvaly pouze v poskytnut\u00ed p\u0159\u00edstupu u\u017eivateli root, co\u017e nevylu\u010dovalo zm\u011bnu nastaven\u00ed zevnit\u0159 kontejneru nebo u\u017eivatelem root bez pr\u00e1v administr\u00e1tora (CAP_SYS_ADMIN). <\/p>\n

D\u0159\u00edve by takov\u00e1 vlastnost nebyla pova\u017eov\u00e1na za zranitelnost, ale situace se zm\u011bnila s p\u0159\u00edchodem jmenn\u00fdch prostor\u016f identifik\u00e1tor\u016f u\u017eivatel\u016f (user namespaces), kter\u00e9 umo\u017e\u0148uj\u00ed vytv\u00e1\u0159et v kontejnerech odd\u011blen\u00e9 u\u017eivatele root, kte\u0159\u00ed se nep\u0159ekr\u00fdvaj\u00ed s u\u017eivatelsk\u00fdm \u00fa\u010dtem root hlavn\u00edho prost\u0159ed\u00ed. Odpov\u00eddaj\u00edc\u00ed k \u00fatoku sta\u010d\u00ed v kontejneru, kter\u00fd m\u00e1 sv\u00e9ho u\u017eivatele root v odd\u011blen\u00e9m jmenn\u00e9m prostoru identifik\u00e1tor\u016f u\u017eivatel\u016f, p\u0159ipojit sv\u016fj obslu\u017en\u00fd program release_agent, kter\u00fd po dokon\u010den\u00ed procesu bude vykon\u00e1n s pln\u00fdmi pr\u00e1vy hlavn\u00edho prost\u0159ed\u00ed. <\/p>\n

P\u0159ednastaven\u011b je cgroupfs v kontejneru montov\u00e1no v re\u017eimu pouze pro \u010dten\u00ed, ale nen\u00ed probl\u00e9m tento pseudofilesyst\u00e9m p\u0159imontovat v re\u017eimu z\u00e1pisu, pokud existuj\u00ed opr\u00e1vn\u011bn\u00ed CAP_SYS_ADMIN, nebo pomoc\u00ed vytvo\u0159en\u00ed prost\u0159ednictv\u00edm syst\u00e9mov\u00e9ho vol\u00e1n\u00ed unshare vno\u0159en\u00e9ho kontejneru s odd\u011blen\u00fdm jmenn\u00fdm prostorem u\u017eivatel\u016f, ve kter\u00e9m jsou pro vytvo\u0159en\u00fd kontejner dostupn\u00e1 pr\u00e1va CAP_SYS_ADMIN.

\"Zranitelnost<\/center> <\/p>\n

\u00datok m\u016f\u017ee b\u00fdt proveden, pokud m\u00e1 \u00fato\u010dn\u00edk root opr\u00e1vn\u011bn\u00ed v izolovan\u00e9m kontejneru nebo pokud je kontejner spu\u0161t\u011bn bez p\u0159\u00edznaku no_new_privs, kter\u00fd zakazuje z\u00edsk\u00e1n\u00ed dodate\u010dn\u00fdch opr\u00e1vn\u011bn\u00ed. V syst\u00e9mu mus\u00ed b\u00fdt povolena podpora user namespaces (ve v\u00fdchoz\u00edm nastaven\u00ed je povolena v Ubuntu a Fedo\u0159e, ale nen\u00ed aktivov\u00e1na v Debianu a RHEL) a mus\u00ed b\u00fdt k dispozici p\u0159\u00edstup k root cgroup v1 (nap\u0159\u00edklad Docker spou\u0161t\u00ed kontejnery v root RDMA cgroup). \u00datok je tak\u00e9 mo\u017en\u00fd p\u0159i p\u0159\u00edtomnosti opr\u00e1vn\u011bn\u00ed CAP_SYS_ADMIN, v takov\u00e9m p\u0159\u00edpad\u011b podpora user namespaces a p\u0159\u00edstup k root hierarchii cgroup v1 nejsou vy\u017eadov\u00e1ny. <\/p>\n

Krom\u011b \u00faniku z izolovan\u00e9ho kontejneru umo\u017e\u0148uje zranitelnost tak\u00e9 proces\u016fm spu\u0161t\u011bn\u00fdm u\u017eivatelem root bez \u201ecapabilities\u201c nebo kter\u00e9mukoli u\u017eivateli s pr\u00e1vy CAP_DAC_OVERRIDE (pro \u00fatok je vy\u017eadov\u00e1n p\u0159\u00edstup k souboru \/sys\/fs\/cgroup\/*\/release_agent, kter\u00fd pat\u0159\u00ed root), z\u00edskat p\u0159\u00edstup ke v\u0161em syst\u00e9mov\u00fdm \u201ecapabilities\u201c. <\/p>\n

Je t\u0159eba poznamenat, \u017ee zranitelnost nelze vyu\u017e\u00edt, pokud jsou pou\u017eity ochrann\u00e9 mechanismy Seccomp, AppArmor nebo SELinux pro dodate\u010dnou izolaci kontejner\u016f, proto\u017ee Seccomp blokuje p\u0159\u00edstup k syst\u00e9mov\u00e9mu vol\u00e1n\u00ed unshare(), a AppArmor a SELinux neumo\u017e\u0148uj\u00ed p\u0159ipojit cgroupfs v re\u017eimu z\u00e1pisu.
\n
Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0420\u0430\u0441\u043a\u0440\u044b\u0442\u044b \u0434\u0435\u0442\u0430\u043b\u0438 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 (CVE-2022-0492) \u0432 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u0438 \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 \u043e\u0433\u0440\u0430\u043d\u0438\u0447\u0435\u043d\u0438\u044f \u0440\u0435\u0441\u0443\u0440\u0441\u043e\u0432 cgroups v1 \u0432 \u044f\u0434\u0440\u0435 Linux, \u043a\u043e\u0442\u043e\u0440\u0430\u044f \u043c\u043e\u0436\u0435\u0442 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u044c\u0441\u044f \u0434\u043b\u044f \u0432\u044b\u0445\u043e\u0434\u0430 \u0438\u0437 \u0438\u0437\u043e\u043b\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u044b\u0445 \u043a\u043e\u043d\u0442\u0435\u0439\u043d\u0435\u0440\u043e\u0432. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u043f\u0440\u043e\u044f\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u043d\u0430\u0447\u0438\u043d\u0430\u044f \u0441 \u044f\u0434\u0440\u0430 Linux 2.6.24 \u0438 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0430 \u0432 \u0432\u044b\u043f\u0443\u0441\u043a\u0430\u0445 \u044f\u0434\u0440\u0430 5.16.12, 5.15.26, 5.10.97, 5.4.177, 4.19.229, 4.14.266 \u0438 4.9.301. \u041f\u0440\u043e\u0441\u043b\u0435\u0434\u0438\u0442\u044c \u0437\u0430 \u043f\u0443\u0431\u043b\u0438\u043a\u0430\u0446\u0438\u0439 \u043e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u044f \u043f\u0430\u043a\u0435\u0442\u043e\u0432 \u0432 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445 \u043c\u043e\u0436\u043d\u043e \u043d\u0430 \u0434\u0430\u043d\u043d\u044b\u0445 \u0441\u0442\u0440\u0430\u043d\u0438\u0446\u0430\u0445: Debian, SUSE, 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