{"id":41582,"date":"2020-02-12T16:19:30","date_gmt":"2020-02-12T13:19:30","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/uyazvimost-v-systemd-potenczialno-pozvolyayushhaya-povysit-svoi-privilegii"},"modified":"2020-02-12T16:19:30","modified_gmt":"2020-02-12T13:19:30","slug":"uyazvimost-v-systemd-potenczialno-pozvolyayushhaya-povysit-svoi-privilegii","status":"publish","type":"post","link":"https:\/\/prohoster.info\/da\/blog\/uyazvimost-v-systemd-potenczialno-pozvolyayushhaya-povysit-svoi-privilegii","title":{"rendered":"En s\u00e5rbarhed i systemd, der potentielt kan give mulighed for at h\u00e6ve privilegier","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

I systemmanager systemd opdaget<\/a><\/noindex> s\u00e5rbarhed (CVE-2020-1712<\/a><\/noindex>), som potentielt tillader eksekvering af brugerens kode med forh\u00f8jede privilegier gennem afsendelse af en specielt formateret anmodning via DBus-bussen. Problemet er blevet rettet i testudgaven systemd 245-rc1<\/a><\/noindex> (rettende patches: 1<\/a><\/noindex>, 2<\/a><\/noindex>, 3<\/a><\/noindex>). S\u00e5rbarheden er blevet elimineret i distributionerne Ubuntu<\/a><\/noindex>, Fedora<\/a><\/noindex>, RHEL<\/a><\/noindex> (forekommer i RHEL 8, men p\u00e5virker ikke RHEL 7), CentOS<\/a><\/noindex>, SUSE\/openSUSE<\/a><\/noindex> og ROSA<\/a><\/noindex>, men p\u00e5 tidspunktet for nyhedens skrivefase er den stadig udbedret i Debian<\/a><\/noindex> og Arch Linux<\/a><\/noindex>. <\/p>\n

S\u00e5rbarheden skyldes adgang til et allerede frigivet hukommelsesomr\u00e5de (use-after-free), som opst\u00e5r under asynkron udf\u00f8relse af anmodninger til Polkit under behandling af DBus-beskeder. Nogle DBus-gr\u00e6nseflader bruger cache til kortvarig opbevaring af objekter og rydder cache-elementer, s\u00e5 snart DBus-bussen er frigivet til behandling af andre anmodninger. Hvis en DBus-metodehandler bruger bus_verify_polkit_async(), skal den muligvis vente p\u00e5, at handlingen i Polkit er f\u00e6rdig. N\u00e5r Polkit er klar, bliver handleren kaldt igen og fors\u00f8ger at tilg\u00e5 tidligere tildelte hukommelsesdata. Hvis anmodningen til Polkit tager for lang tid, kan cache-elementer blive ryddet, f\u00f8r DBus-metodehandleren kaldes anden gang. <\/p>\n

Blandt de services, der muligg\u00f8r udnyttelse af s\u00e5rbarheden, bem\u00e6rkes systemd-machined, som tilbyder DBus API org.freedesktop.machine1.Image.Clone, hvilket f\u00f8rer til midlertidig lagring af data i cachen og asynkron adgang til Polkit. Gr\u00e6nsefladen
\norg.freedesktop.machine1.Image.Clone er tilg\u00e6ngelig for alle ikke-privilegerede brugere af systemet, som kan initiere nedbrud af systemd-services eller potentielt opn\u00e5 k\u00f8rsel af kode med root-rettigheder (prototype af exploit er endnu ikke demonstreret). Koden til at udnytte s\u00e5rbarheden blev tilf\u00f8jet<\/a><\/noindex> i systemd-machined i 2015 i version systemd 220<\/a><\/noindex> (i RHEL 7.x bruges systemd 219). <\/p>\n

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

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

\u0412 \u0441\u0438\u0441\u0442\u0435\u043c\u043d\u043e\u043c \u043c\u0435\u043d\u0435\u0434\u0436\u0435\u0440\u0435 systemd \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2020-1712), \u043a\u043e\u0442\u043e\u0440\u0430\u044f \u043f\u043e\u0442\u0435\u043d\u0446\u0438\u0430\u043b\u044c\u043d\u043e \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0435\u0442 \u0434\u043e\u0431\u0438\u0442\u044c\u0441\u044f \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f \u0441\u0432\u043e\u0435\u0433\u043e \u043a\u043e\u0434\u0430 \u0441 \u043f\u043e\u0432\u044b\u0448\u0435\u043d\u043d\u044b\u043c\u0438 \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u044f\u043c\u0438 \u0447\u0435\u0440\u0435\u0437 \u043e\u0442\u043f\u0440\u0430\u0432\u043a\u0443 \u0441\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u043e \u043e\u0444\u043e\u0440\u043c\u043b\u0435\u043d\u043d\u043e\u0433\u043e \u0437\u0430\u043f\u0440\u043e\u0441\u0430 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