{"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\/fr\/blog\/uyazvimost-v-systemd-potenczialno-pozvolyayushhaya-povysit-svoi-privilegii","title":{"rendered":"Vuln\u00e9rabilit\u00e9 dans systemd, permettant potentiellement d'\u00e9lever ses privil\u00e8ges","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Dans le gestionnaire de syst\u00e8me systemd une vuln\u00e9rabilit\u00e9 a \u00e9t\u00e9 identifi\u00e9e<\/a><\/noindex> une vuln\u00e9rabilit\u00e9 (CVE-2020-1712<\/a><\/noindex>), qui permet potentiellement d'ex\u00e9cuter son propre code avec des privil\u00e8ges \u00e9lev\u00e9s en envoyant une requ\u00eate sp\u00e9cialement format\u00e9e via le bus DBus. Le probl\u00e8me a \u00e9t\u00e9 corrig\u00e9 dans la version de test systemd 245-rc1<\/a><\/noindex> (correctifs r\u00e9solvant le probl\u00e8me : 1<\/a><\/noindex>, 2<\/a><\/noindex>, 3<\/a><\/noindex>). La vuln\u00e9rabilit\u00e9 a \u00e9t\u00e9 corrig\u00e9e dans les distributions Ubuntu<\/a><\/noindex>, Fedora<\/a><\/noindex>, RHEL<\/a><\/noindex> (appara\u00eet dans RHEL 8, mais n'affecte pas RHEL 7), CentOS<\/a><\/noindex>, SUSE\/openSUSE<\/a><\/noindex> et ROSA<\/a><\/noindex>, mais au moment de la r\u00e9daction de la nouvelle, elle reste non corrig\u00e9e dans Debian<\/a><\/noindex> et Arch Linux<\/a><\/noindex>. <\/p>\n

La vuln\u00e9rabilit\u00e9 est due \u00e0 un acc\u00e8s \u00e0 une zone de m\u00e9moire d\u00e9j\u00e0 lib\u00e9r\u00e9e (use-after-free), qui se produit lors de l'ex\u00e9cution asynchrone des requ\u00eates \u00e0 Polkit pendant le traitement des messages DBus. Certaines interfaces DBus utilisent un cache pour stocker des objets pendant une courte p\u00e9riode et nettoient les \u00e9l\u00e9ments du cache d\u00e8s que le bus DBus est libre pour traiter d'autres requ\u00eates. Si le gestionnaire de m\u00e9thode DBus utilise bus_verify_polkit_async(), il peut avoir besoin d'attendre l'ach\u00e8vement de l'action dans Polkit. Une fois que Polkit est pr\u00eat, le gestionnaire est appel\u00e9 \u00e0 nouveau et acc\u00e8de aux donn\u00e9es pr\u00e9c\u00e9demment allou\u00e9es en m\u00e9moire. Si la requ\u00eate \u00e0 Polkit prend trop de temps, les \u00e9l\u00e9ments du cache peuvent \u00eatre nettoy\u00e9s avant que le gestionnaire de m\u00e9thode DBus ne soit appel\u00e9 une deuxi\u00e8me fois. <\/p>\n

Parmi les services permettant d'exploiter la vuln\u00e9rabilit\u00e9, on note systemd-machined, qui fournit l'API DBus org.freedesktop.machine1.Image.Clone, ce qui entra\u00eene un stockage temporaire de donn\u00e9es dans le cache et un acc\u00e8s asynchrone \u00e0 Polkit. L'interface
\norg.freedesktop.machine1.Image.Clone est accessible \u00e0 tous les utilisateurs non privil\u00e9gi\u00e9s du syst\u00e8me, qui peuvent provoquer des crashs de services systemd ou potentiellement ex\u00e9cuter du code avec des droits root (le prototype de l'exploit n'a pas encore \u00e9t\u00e9 d\u00e9montr\u00e9). Le code permettant d'exploiter la vuln\u00e9rabilit\u00e9 a \u00e9t\u00e9 ajout\u00e9<\/a><\/noindex> dans systemd-machined en 2015 dans la version systemd 220<\/a><\/noindex> (systemd 219 est utilis\u00e9 dans RHEL 7.x). <\/p>\n

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

Source : 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 \u043f\u043e \u0448\u0438\u043d\u0435 DBus. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u0438\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0430 \u0432 \u0442\u0435\u0441\u0442\u043e\u0432\u043e\u043c \u0432\u044b\u043f\u0443\u0441\u043a\u0435 systemd 245-rc1 (\u0440\u0435\u0448\u0430\u044e\u0449\u0438\u0435 \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u0443 \u043f\u0430\u0442\u0447\u0438: 1, 2, 3). \u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0430 \u0432 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445 Ubuntu, Fedora, RHEL (\u043f\u0440\u043e\u044f\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u0432 RHEL 8, \u043d\u043e \u043d\u0435 \u0437\u0430\u0442\u0440\u0430\u0433\u0438\u0432\u0430\u0435\u0442 RHEL 7), CentOS, 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