{"id":100548,"date":"2021-06-20T10:22:54","date_gmt":"2021-06-20T08:22:55","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-yadre-linux-zatragivayushhaya-setevoj-protokol-can-bcm"},"modified":"2021-06-20T10:22:54","modified_gmt":"2021-06-20T08:22:55","slug":"uyazvimost-v-yadre-linux-zatragivayushhaya-setevoj-protokol-can-bcm","status":"publish","type":"post","link":"https:\/\/prohoster.info\/it\/blog\/news\/uyazvimost-v-yadre-linux-zatragivayushhaya-setevoj-protokol-can-bcm","title":{"rendered":"Vulnerabilit\u00e0 nel kernel Linux che colpisce il protocollo di rete CAN BCM","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\u00c8 stata identificata una vulnerabilit\u00e0 nel kernel Linux (CVE-2021-3609) che consente a un utente locale di elevare i propri privilegi nel sistema. Il problema \u00e8 causato da una condizione di competizione nell'implementazione del protocollo CAN BCM e si manifesta in versioni del kernel Linux dalla 2.6.25 alla 5.13-rc6. Nei vari distribuzioni, il problema rimane irrisolto (RHEL, Fedora, Debian, Ubuntu, SUSE, Arch). <\/p>\n

Il ricercatore che ha scoperto la vulnerabilit\u00e0 \u00e8 riuscito a preparare un exploit per ottenere diritti di root su sistemi con kernel Linux 5.4 e versioni successive; \u00e8 stata dimostrata la possibilit\u00e0 di eseguire un attacco con successo su Ubuntu 20.04.02 LTS. Non si esclude la possibilit\u00e0 di adattare l'exploit per funzionare con kernel pi\u00f9 vecchi (nel kernel 5.4 il codice CAN BCM (net\/can\/bcm.c) \u00e8 stato convertito da hrtimer_tasklet a HRTIMER_MODE_SOFT). <\/p>\n

Il protocollo CAN BCM consente di registrare un proprio gestore di messaggi in arrivo tramite il bus CAN (controller area network) e di associarlo a un determinato socket di rete. Quando arriva un messaggio in ingresso, viene chiamata la funzione bcm_rx_handler(). L'attaccante pu\u00f2 sfruttare la condizione di competizione e ottenere la chiusura del socket di rete contemporaneamente all'esecuzione di bcm_rx_handler(). Alla chiusura del socket, viene chiamata la funzione bcm_release(), che libera la memoria allocata per le strutture bcm_op e bcm_sock, che continuano ad essere utilizzate in un gestore bcm_rx_handler() ancora in esecuzione. Si verifica cos\u00ec una situazione che porta all'accesso a un blocco di memoria gi\u00e0 liberato (use-after-free). <\/p>\n

L'attacco consiste nell'aprire due socket CAN BCM e associarli all'interfaccia vcan. Nel primo socket viene effettuata una chiamata sendmsg() con il flag RX_SETUP per configurare il gestore dei messaggi CAN in arrivo, mentre nel secondo socket viene effettuata una chiamata sendmsg() per inviare un messaggio al primo socket. Dopo che il messaggio \u00e8 stato ricevuto, viene attivata la chiamata bcm_rx_handler(), e l'attaccante sceglie il momento giusto per chiudere il primo socket, il che porta all'esecuzione di bcm_release() e al rilascio delle strutture bcm_op e bcm_sock, sebbene l'esecuzione di bcm_rx_handler() non sia ancora terminata. <\/p>\n

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\"Vulnerabilit\u00e0<\/center> <\/p>\n

Per l'attacco \u00e8 necessaria l'accessibilit\u00e0 per creare socket CAN e un'interfaccia di rete vcan configurata. I privilegi necessari per eseguire l'attacco possono essere ottenuti da un utente non privilegiato all'interno di container creati in sistemi con supporto attivato per gli spazi dei nomi degli identificatori utente (user namespaces). Ad esempio, i nomi di utenti sono abilitati di default su Ubuntu e Fedora, ma non attivati su Debian e RHEL.
\n
Fonte: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u044f\u0434\u0440\u0435 Linux \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2021-3609), \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 \u043f\u043e\u0434\u043d\u044f\u0442\u044c \u0441\u0432\u043e\u0438 \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0438 \u0432 \u0441\u0438\u0441\u0442\u0435\u043c\u0435. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u0432\u044b\u0437\u0432\u0430\u043d\u0430 \u0441\u043e\u0441\u0442\u043e\u044f\u043d\u0438\u0435\u043c \u0433\u043e\u043d\u043a\u0438 \u0432 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u0438 \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b\u0430 CAN BCM \u0438 \u043f\u0440\u043e\u044f\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u0432 \u0432\u044b\u043f\u0443\u0441\u043a\u0430\u0445 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[…]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":100549,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-100548","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\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\n","aioseo_head_json":{"title":"\ud83e\udd47Vulnerabilit\u00e0 nel kernel di Linux che coinvolge il protocollo di rete CAN BCM | ProHoster","description":"\u00c8 stata rilevata una vulnerabilit\u00e0 nel kernel di Linux (CVE-2021-3609) che consente a un utente locale di elevare i propri privilegi nel 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