{"id":35693,"date":"2019-10-31T22:05:48","date_gmt":"2019-10-31T19:05:48","guid":{"rendered":"https:\/\/prohoster.info\/blog\/uyazvimost-v-amd-sev-pozvolyayushhaya-opredelit-klyuchi-shifrovaniya\/"},"modified":"2019-10-31T22:05:48","modified_gmt":"2019-10-31T19:05:48","slug":"uyazvimost-v-amd-sev-pozvolyayushhaya-opredelit-klyuchi-shifrovaniya","status":"publish","type":"post","link":"https:\/\/prohoster.info\/da\/blog\/news\/uyazvimost-v-amd-sev-pozvolyayushhaya-opredelit-klyuchi-shifrovaniya","title":{"rendered":"S\u00e5rbarhed i AMD SEV, der g\u00f8r det muligt at afsl\u00f8re krypteringsn\u00f8gler","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Udviklerne fra Google Cloud-teamet har identificeret<\/a><\/noindex> s\u00e5rbarhed (CVE-2019-9836) i implementeringen af AMD SEV (Secure Encrypted Virtualization), som muligg\u00f8r kompromittering af data beskyttet ved hj\u00e6lp af denne teknologi. AMD SEV sikrer p\u00e5 hardware-niveau transparent kryptering af hukommelsen i virtuelle maskiner, hvoradgangen til de dekrypterede data kun har det nuv\u00e6rende g\u00e6steoperativsystem, mens andre virtuelle maskiner og hypervisoren ved fors\u00f8g p\u00e5 at f\u00e5 adgang til denne hukommelse kun modtager et krypteret datas\u00e6t.<\/p>\n

Den identificerede problematik tillader fuldst\u00e6ndig gendannelse af indholdet af den lukkede PDH-n\u00f8gle, som behandles p\u00e5 niveauet af den enkelte beskyttede processor PSP (AMD Security Processor), der ikke er tilg\u00e6ngelig for det prim\u00e6re OS.
\nMed PDH-n\u00f8glen kan angriberen derefter gendanne sessionsn\u00f8glen og den hemmelige sekvens, der blev fastsat ved oprettelsen af den virtuelle maskine, og f\u00e5 adgang til de krypterede data. <\/p>\n

S\u00e5rbarheden er for\u00e5rsaget af mangler i implementeringen af elliptiske kurver (ECC), der anvendes til kryptering, som muligg\u00f8r angreb<\/a><\/noindex> for at genskabe kurveparametre. Under udf\u00f8relse af kommandoen for at starte den beskyttede virtuelle maskine kan angriberen sende kurveparametre, der ikke svarer til de anbefalede parametre fra NIST, hvilket vil resultere i brugen af v\u00e6rdier fra punkter med lav orden i multiplikationsoperationer med data om den lukkede n\u00f8gle. <\/p>\n

Sikkerheden i ECDH-protokollen afh\u00e6nger direkte af<\/a><\/noindex> fra orden<\/a><\/noindex> af den genererede startpunkt for kurven, hvis diskrete logaritmerepr\u00e6sentation er en meget kompleks opgave. P\u00e5 et af initialiseringstrin for milj\u00f8et AMD SEV anvendes parametre, der er modtaget fra brugeren, i beregninger med den lukkede n\u00f8gle. I princippet udf\u00f8res der en multiplikation af to punkter, hvor det ene svarer til den lukkede n\u00f8gle. Hvis det andet punkt er relateret til primtal af lav orden, kan angriberen bestemme parametrene for det f\u00f8rste punkt (modulbiterne brugt i exponentiel modulooperation) ved at pr\u00f8ve alle mulige v\u00e6rdier. For at bestemme den lukkede n\u00f8gle kan de udvalgte fragmenter af primtal derefter samles ved hj\u00e6lp af Kinesisk restteorem<\/a><\/noindex>.<\/p>\n

Problemstillingen rammer AMD EPYC-serverplatforme, der bruger SEV-firmware op til version 0.17 build 11. AMD har allerede offentliggjorde<\/noindex> Opdatering af firmware, der tilf\u00f8jer en blokering mod brug af punkter, der ikke svarer til NIST-kurven. Tidligere genererede certifikater til PDH-n\u00f8gler forbliver gyldige, hvilket g\u00f8r det muligt for en angriber at udf\u00f8re et angreb ved at migrere virtuelle maskiner fra milj\u00f8er, der er beskyttet mod s\u00e5rbarheden, til milj\u00f8er, der er udsat for problemet. Der n\u00e6vnes ogs\u00e5 muligheden for at udf\u00f8re et angreb ved at rulle firmwareversionen tilbage til en \u00e6ldre s\u00e5rbar udgave, men denne mulighed er endnu ikke bekr\u00e6ftet.<\/p>\n

<\/a><\/noindex><\/p>\n

Kilde: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0420\u0430\u0437\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u0438 \u0438\u0437 \u043a\u043e\u043c\u0430\u043d\u0434\u044b Google Cloud \u0432\u044b\u044f\u0432\u0438\u043b\u0438 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2019-9836) \u0432 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u0438 \u0442\u0435\u0445\u043d\u043e\u043b\u043e\u0433\u0438\u0438 AMD SEV (Secure Encrypted Virtualization), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0443\u044e \u0441\u043a\u043e\u043c\u043f\u0440\u043e\u043c\u0435\u0442\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u0437\u0430\u0449\u0438\u0449\u0451\u043d\u043d\u044b\u0435 \u043f\u0440\u0438 \u043f\u043e\u043c\u043e\u0449\u0438 \u0434\u0430\u043d\u043d\u043e\u0439 \u0442\u0435\u0445\u043d\u043e\u043b\u043e\u0433\u0438\u0438 \u0434\u0430\u043d\u043d\u044b\u0435. 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