{"id":99693,"date":"2021-04-09T16:22:51","date_gmt":"2021-04-09T14:22:51","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimosti-v-podsisteme-ebpf-yadra-linux"},"modified":"2021-04-09T16:22:51","modified_gmt":"2021-04-09T14:22:51","slug":"uyazvimosti-v-podsisteme-ebpf-yadra-linux","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/uyazvimosti-v-podsisteme-ebpf-yadra-linux","title":{"rendered":"Zranitelnosti v subsyst\u00e9mu eBPF j\u00e1dra Linuxu","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V subsyst\u00e9mu eBPF, kter\u00fd umo\u017e\u0148uje spou\u0161t\u011bt zpracovatele pro sledov\u00e1n\u00ed, anal\u00fdzu fungov\u00e1n\u00ed subsyst\u00e9m\u016f a \u0159\u00edzen\u00ed provozu, prov\u00e1d\u011bn\u00e9 uvnit\u0159 j\u00e1dra Linux v speci\u00e1ln\u00edm virtu\u00e1ln\u00edm stroji s JIT, byla odhalena zranitelnost (CVE-2021-29154), kter\u00e1 umo\u017e\u0148uje lok\u00e1ln\u00edmu u\u017eivateli prov\u00e9st sv\u016fj k\u00f3d na \u00farovni j\u00e1dra. Probl\u00e9m se projevuje a\u017e do vyd\u00e1n\u00ed 5.11.12 (v\u010detn\u011b) a je\u0161t\u011b nebyl opraven v distribuc\u00edch (Debian, Ubuntu, RHEL, Fedora, SUSE, Arch). Oprava je k dispozici ve form\u011b patch. <\/p>\n

Podle tvrzen\u00ed v\u00fdzkumn\u00edk\u016f, kte\u0159\u00ed zranitelnost odhalili, se jim poda\u0159ilo vyvinout funk\u010dn\u00ed prototyp exploitu pro 32- a 64bitov\u00e9 syst\u00e9my x86, kter\u00fd m\u016f\u017ee b\u00fdt pou\u017eit neprivilegovan\u00fdm u\u017eivatelem. Spole\u010dnost Red Hat z\u00e1rove\u0148 uv\u00e1d\u00ed, \u017ee nebezpe\u010dnost probl\u00e9mu z\u00e1vis\u00ed na dostupnosti syst\u00e9mov\u00e9ho vol\u00e1n\u00ed eBPF pro u\u017eivatele. Nap\u0159\u00edklad v RHEL a v\u011bt\u0161in\u011b dal\u0161\u00edch distribuc\u00ed Linux ve v\u00fdchoz\u00ed konfiguraci lze zranitelnost vyu\u017e\u00edt p\u0159i zapnut\u00ed BPF JIT a pokud m\u00e1 u\u017eivatel opr\u00e1vn\u011bn\u00ed CAP_SYS_ADMIN. Jako obranou proti \u00fatoku se doporu\u010duje vypnout BPF JIT pomoc\u00ed p\u0159\u00edkazu: echo 0 > \/proc\/sys\/net\/core\/bpf_jit_enable <\/p>\n

Probl\u00e9m je zp\u016fsoben chybou ve v\u00fdpo\u010dtu offsetu pro v\u011btven\u00ed p\u0159i generov\u00e1n\u00ed strojov\u00e9ho k\u00f3du JIT kompil\u00e1torem. Konkr\u00e9tn\u011b p\u0159i generov\u00e1n\u00ed v\u011btv\u00edc\u00edch instrukc\u00ed se nebere v \u00favahu, \u017ee offset se m\u016f\u017ee zm\u011bnit po f\u00e1zi optimalizace. Tato nedokonalost m\u016f\u017ee b\u00fdt vyu\u017eita k vytvo\u0159en\u00ed abnorm\u00e1ln\u00edho strojov\u00e9ho k\u00f3du a jeho proveden\u00ed na \u00farovni j\u00e1dra. <\/p>\n

Pozoruhodn\u00e9 je, \u017ee toto nen\u00ed jedin\u00e1 zranitelnost v subsyst\u00e9mu eBPF v posledn\u00ed dob\u011b. Na konci b\u0159ezna byly v j\u00e1d\u0159e nalezeny dal\u0161\u00ed dv\u011b zranitelnosti (CVE-2020-27170, CVE-2020-27171), kter\u00e9 umo\u017e\u0148uj\u00ed vyu\u017e\u00edt eBPF k obran\u011b proti zranitelnostem t\u0159\u00eddy Spectre, je\u017e umo\u017e\u0148uj\u00ed zjistit obsah j\u00e1dra pam\u011bti n\u00e1sledkem vytvo\u0159en\u00ed podm\u00ednek pro spekulativn\u00ed prov\u00e1d\u011bn\u00ed ur\u010dit\u00fdch operac\u00ed. Pro \u00fatok Spectre je pot\u0159eba, aby v privilegovan\u00e9m k\u00f3du byla ur\u010dit\u00e9 sekvence p\u0159\u00edkaz\u016f, kter\u00e9 vedou k spekulativn\u00edmu prov\u00e1d\u011bn\u00ed instrukc\u00ed. V eBPF bylo nalezeno n\u011bkolik zp\u016fsob\u016f, jak generovat podobn\u00e9 instrukce prost\u0159ednictv\u00edm manipulace s p\u0159ed\u00e1van\u00fdmi BPF programy. <\/p>\n

Zranitelnost CVE-2020-27170 je zp\u016fsobena manipulac\u00ed se ukazateli ve verifik\u00e1toru BPF, kter\u00e1 vyvol\u00e1v\u00e1 spekulativn\u00ed operace p\u0159\u00edstupu k oblastem mimo hranice bufferu. Zranitelnost CVE-2020-27171 souvis\u00ed s chybou celkov\u00e9ho po\u010dtu (integer underflow) p\u0159i pr\u00e1ci s ukazateli, co\u017e vede k spekulativn\u00edmu p\u0159\u00edstupu k dat\u016fm mimo buffer. Zm\u00edn\u011bn\u00e9 probl\u00e9my byly ji\u017e odstran\u011bny ve verz\u00edch j\u00e1dra 5.11.8, 5.10.25, 5.4.107, 4.19.182 a 4.14.227 a byly zahrnuty do aktualizac\u00ed j\u00e1dra v\u011bt\u0161iny distribuc\u00ed Linux. V\u00fdzkumn\u00edci p\u0159ipravili prototyp exploit, kter\u00fd umo\u017e\u0148uje nep\u0159ihl\u00e1\u0161en\u00e9mu u\u017eivateli extrahovat data z pam\u011bti j\u00e1dra.
\n
Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u0435 eBPF, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0435\u0439 \u0437\u0430\u043f\u0443\u0441\u043a\u0430\u0442\u044c \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u0438 \u0434\u043b\u044f \u0442\u0440\u0430\u0441\u0441\u0438\u0440\u043e\u0432\u043a\u0438, \u0430\u043d\u0430\u043b\u0438\u0437\u0430 \u0440\u0430\u0431\u043e\u0442\u044b \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c \u0438 \u0443\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0438\u044f \u0442\u0440\u0430\u0444\u0438\u043a\u043e\u043c, \u0432\u044b\u043f\u043e\u043b\u043d\u044f\u0435\u043c\u044b\u0435 \u0432\u043d\u0443\u0442\u0440\u0438 \u044f\u0434\u0440\u0430 Linux \u0432 \u0441\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u043e\u0439 \u0432\u0438\u0440\u0442\u0443\u0430\u043b\u044c\u043d\u043e\u0439 \u043c\u0430\u0448\u0438\u043d\u0435 \u0441 JIT, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2021-29154), \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 \u0434\u043e\u0431\u0438\u0442\u044c\u0441\u044f \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f \u0441\u0432\u043e\u0433\u043e \u043a\u043e\u0434\u0430 \u043d\u0430 \u0443\u0440\u043e\u0432\u043d\u0435 \u044f\u0434\u0440\u0430. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u043f\u0440\u043e\u044f\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u0432\u043f\u043b\u043e\u0442\u044c \u0434\u043e \u0432\u044b\u043f\u0443\u0441\u043a\u0430 5.11.12 (\u0432\u043a\u043b\u044e\u0447\u0438\u0442\u0435\u043b\u044c\u043d\u043e) \u0438 \u0435\u0449\u0451 \u043d\u0435 \u0438\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0430 \u0432 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445 (Debian, Ubuntu, RHEL, Fedora, SUSE, […]<\/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-99693","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\udd47Zranitelnosti v subsyst\u00e9mu eBPF j\u00e1dra Linux | ProHoster","description":"V subsyst\u00e9mu eBPF, kter\u00fd umo\u017e\u0148uje spou\u0161t\u011bn\u00ed zpracovatel\u016f pro sledov\u00e1n\u00ed, anal\u00fdzu v\u00fdkonu subsyst\u00e9m\u016f a \u0159\u00edzen\u00ed provozu prov\u00e1d\u011bn\u00e9ho uvnit\u0159 j\u00e1dra Linux ve speci\u00e1ln\u00ed virtu\u00e1ln\u00ed ma\u0161in\u011b s JIT, byla zji\u0161t\u011bna zranitelnost.","canonical_url":"https:\/\/prohoster.info\/cs\/blog\/news\/uyazvimosti-v-podsisteme-ebpf-yadra-linux","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"cs_CZ","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u0432 \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u0435 eBPF \u044f\u0434\u0440\u0430 Linux | ProHoster","og:description":"\u0412 \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u0435 eBPF, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0435\u0439 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