Bezpe\u010dnostn\u00ed v\u00fdzkumn\u00edci z Googlu zve\u0159ejnili informace o zranitelnosti (CVE-2024-56161) v procesorech AMD, kter\u00e1 se t\u00fdk\u00e1 zav\u00e1d\u011b\u010di mikrok\u00f3du a umo\u017e\u0148uje obej\u00edt mechanismus ov\u011b\u0159ov\u00e1n\u00ed digit\u00e1ln\u00edho podpisu p\u0159i aktualizac\u00edch mikrok\u00f3du. Na\u010dten\u00ed modifikovan\u00e9ho mikrok\u00f3du umo\u017e\u0148uje kompromitaci mechanismu AMD SEV (Secure Encrypted Virtualization), kter\u00fd se pou\u017e\u00edv\u00e1 v virtualiza\u010dn\u00edch syst\u00e9mech k ochran\u011b virtu\u00e1ln\u00edch stroj\u016f p\u0159ed z\u00e1sahem hypervizora nebo administr\u00e1tora hostitelsk\u00e9 soustavy. <\/p>\n
Zranitelnost je zp\u016fsobena pou\u017eit\u00edm nezabezpe\u010den\u00e9 hashovac\u00ed funkce v k\u00f3du, kter\u00fd prov\u00e1d\u00ed ov\u011b\u0159ov\u00e1n\u00ed digit\u00e1ln\u00edho podpisu po na\u010dten\u00ed mikrok\u00f3du do CPU. K proveden\u00ed \u00fatoku jsou pot\u0159ebn\u00e1 administr\u00e1torsk\u00e1 pr\u00e1va v m\u00edstn\u00edm syst\u00e9mu (mo\u017enost vykon\u00e1vat k\u00f3d v re\u017eimu s nulov\u00fdm ochrann\u00fdm kolem (ring0), ani\u017e byste byli ve virtu\u00e1ln\u00edm stroji). <\/p>\n
B\u011bhem \u00fatoku lze zasahovat do provozu hostitelsk\u00fdch syst\u00e9m\u016f, kter\u00e9 jsou chr\u00e1n\u011bny pomoc\u00ed roz\u0161\u00ed\u0159en\u00ed AMD SEV (Secure Encrypted Virtualization) a SEV-SNP (Secure Nested Paging), kter\u00e1 poskytuj\u00ed z\u00e1ruky integrity pam\u011bti, virtu\u00e1ln\u00edch stroj\u016f<\/a>, izoluj\u00ed procesorov\u00e9 registry a zaji\u0161\u0165uj\u00ed bezpe\u010dn\u00fd provoz s vlo\u017een\u00fdmi tabulkami str\u00e1nek pam\u011bti. Mechanismus AMD SEV byl vytvo\u0159en tak, aby zam\u011bstnanci datov\u00fdch center a cloudov\u00fdch provider\u016f nemohli m\u011bnit nebo analyzovat obsah pam\u011bti chr\u00e1n\u011bn\u00fdch hostitelsk\u00fdch syst\u00e9m\u016f, ani zkreslovat v\u00fdpo\u010dty. <\/p>\n V\u00fdzkumn\u00edci p\u0159ipravili prototyp exploitu, kter\u00fd umo\u017e\u0148uje na\u010d\u00edst libovoln\u00fd mikrok\u00f3d do CPU, kter\u00fd nen\u00ed ov\u011b\u0159en digit\u00e1ln\u00edm podpisem. Pro demonstration nebezpe\u010dnosti zranitelnosti bylo navr\u017eeno aktualizace mikrok\u00f3du, kter\u00e1 m\u011bn\u00ed logiku pr\u00e1ce instrukce RDRAND, kter\u00e1 se pou\u017e\u00edv\u00e1 jako jeden ze zdroj\u016f entropie v gener\u00e1torech pseudon\u00e1hodn\u00fdch \u010d\u00edsel pou\u017e\u00edvan\u00fdch p\u0159i vytv\u00e1\u0159en\u00ed kl\u00ed\u010d\u016f, p\u0159i prov\u00e1d\u011bn\u00ed kryptografick\u00fdch operac\u00ed a k generov\u00e1n\u00ed n\u00e1hodn\u00fdch identifik\u00e1tor\u016f. <\/p>\n Zm\u011bna vede k vracen\u00ed instrukce RDRAND pouze \u010d\u00edsla 4 nam\u00edsto n\u00e1hodn\u00e9 sekvence. Aby se p\u0159ede\u0161lo re\u00e1ln\u00fdm \u00fatok\u016fm na syst\u00e9my d\u016fv\u011brn\u00e9ho v\u00fdpo\u010dtu, upraven\u00fd mikrok\u00f3d nulov\u00e1v\u00e1 flag CF (carry flag), tj. ozna\u010duje vydanou hodnotu za chybnou. Dal\u0161\u00ed podrobnosti a n\u00e1stroje pro generaci upraven\u00e9ho mikrok\u00f3du pl\u00e1nuj\u00ed zve\u0159ejnit 5. b\u0159ezna, aby u\u017eivatel\u00e9 m\u011bli \u010das na instalaci opravy na sv\u00fdch syst\u00e9mech. \u00dasp\u011b\u0161n\u00fd p\u0159\u00edklad \u00fatoku byl demonstrov\u00e1n na servery<\/a> procesorech AMD EPYC 7B13 (Milan) a AMD Ryzen 9 7940HS (Phoenix). <\/p>\n Ve zpr\u00e1v\u011b spole\u010dnosti AMD je uvedeno, \u017ee zranitelnost se projevuje v procesorech AMD zalo\u017een\u00fdch na 1-4 generac\u00edch mikroarchitektury Zen. Aktualizace mikrok\u00f3du, kter\u00e1 odstranila zranitelnost, byla vyd\u00e1na 13. prosince 2024 pro procesory \u0159ady AMD EPYC 7001, 7002 a 7003 (Naples, Rome, Milan a Milan-X), a 16. prosince pro procesory \u0159ady AMD EPYC 9004 (Genoa, Genoa-X a Bergamo\/Siena). Pro odstran\u011bn\u00ed zranitelnosti je nav\u00edc pot\u0159eba aktualizace firmwaru AMD SEV (zahrnuj\u00edc\u00ed se s aktualizacemi BIOS od v\u00fdrobc\u016f za\u0159\u00edzen\u00ed). <\/p>\n D\u00e1le byla hl\u00e1\u0161ena dal\u0161\u00ed zranitelnost v procesorech AMD, kter\u00e1 umo\u017e\u0148uje prov\u00e1d\u011bt \u00fatoky pomoc\u00ed bo\u010dn\u00edch kan\u00e1l\u016f k extrakci informac\u00ed o v\u00fdpo\u010dtech v chr\u00e1n\u011bn\u00fdch syst\u00e9mov\u00fdch prost\u0159ed\u00edch vyu\u017e\u00edvaj\u00edc\u00edch mechanismus AMD SEV. Probl\u00e9m se t\u00fdk\u00e1 procesor\u016f AMD EPYC 1-4 generace a souvis\u00ed s mo\u017enost\u00ed extrakce dat z procesorov\u00e9 cache, kter\u00e9 se usazuj\u00ed b\u011bhem provozu chr\u00e1n\u011bn\u00fdch syst\u00e9m\u016f. K anal\u00fdze obsahu cache lze pou\u017e\u00edt metodu Prime+Probe, kter\u00e1 zahrnuje napln\u011bn\u00ed cache referen\u010dn\u00edm souborem hodnot a ur\u010den\u00ed zm\u011bn prost\u0159ednictv\u00edm m\u011b\u0159en\u00ed \u010dasu p\u0159\u00edstupu k nim p\u0159i op\u011btovn\u00e9m napln\u011bn\u00ed. Je uvedeno, \u017ee pro blokov\u00e1n\u00ed \u00fatoku jsou vhodn\u00e9 metody d\u0159\u00edve navr\u017een\u00e9 na ochranu proti \u00fatok\u016fm t\u0159\u00eddy Spectre. \u0418\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u0438 \u0431\u0435\u0437\u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 \u0438\u0437 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0438 Google \u043e\u043f\u0443\u0431\u043b\u0438\u043a\u043e\u0432\u0430\u043b\u0438 \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044e \u043e\u0431 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 (CVE-2024-56161) \u0432 \u043f\u0440\u043e\u0446\u0435\u0441\u0441\u043e\u0440\u0430\u0445 AMD, \u0437\u0430\u0442\u0440\u0430\u0433\u0438\u0432\u0430\u044e\u0449\u0435\u0439 \u0437\u0430\u0433\u0440\u0443\u0437\u0447\u0438\u043a \u043c\u0438\u043a\u0440\u043e\u043a\u043e\u0434\u0430 \u0438 \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0435\u0439 \u043e\u0431\u043e\u0439\u0442\u0438 \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 \u0446\u0438\u0444\u0440\u043e\u0432\u043e\u0439 \u043f\u043e\u0434\u043f\u0438\u0441\u0438 \u043f\u0440\u0438 \u043e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u0439 \u043c\u0438\u043a\u0440\u043e\u043a\u043e\u0434\u0430. \u0417\u0430\u0433\u0440\u0443\u0437\u043a\u0430 \u043c\u043e\u0434\u0438\u0444\u0438\u0446\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u043e\u0433\u043e \u043c\u0438\u043a\u0440\u043e\u043a\u043e\u0434\u0430 \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0435\u0442 \u0441\u043a\u043e\u043c\u043f\u0440\u043e\u043c\u0435\u0442\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c AMD SEV (Secure Encrypted Virtualization), \u043f\u0440\u0438\u043c\u0435\u043d\u044f\u0435\u043c\u044b\u0439 \u0432 \u0441\u0438\u0441\u0442\u0435\u043c\u0430\u0445 \u0432\u0438\u0440\u0442\u0443\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u0438 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[…]<\/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-121698","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 na\u010d\u00edta\u010di mikrok\u00f3du v CPU AMD, kter\u00e1 umo\u017e\u0148uje obej\u00edt izolaci SEV-SNP | ProHoster","description":"Bezpe\u010dnostn\u00ed v\u00fdzkumn\u00edci ze spole\u010dnosti Google zve\u0159ejnili informace o zranitelnosti (CVE-2024-56161) v procesorech AMD, kter\u00e1 se dot\u00fdk\u00e1 na\u010d\u00edta\u010de mikrok\u00f3du a umo\u017e\u0148uje obej\u00edt mechanismus 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Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"