{"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\/pl\/blog\/news\/uyazvimost-v-yadre-linux-zatragivayushhaya-setevoj-protokol-can-bcm","title":{"rendered":"Vulnerability in Linux kernel affecting CAN BCM network protocol","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

W j\u0105drze Linux odkryto podatno\u015b\u0107 (CVE-2021-3609), kt\u00f3ra umo\u017cliwia lokalnemu u\u017cytkownikowi zwi\u0119kszenie swoich uprawnie\u0144 w systemie. Problem jest spowodowany warunkiem wy\u015bcigu w implementacji protoko\u0142u CAN BCM i wyst\u0119puje w wydaniach j\u0105dra Linux od 2.6.25 do 5.13-rc6. W dystrybucjach problem na razie pozostaje nieza\u0142atwiony (RHEL, Fedora, Debian, Ubuntu, SUSE, Arch). <\/p>\n

Badacz, kt\u00f3ry odkry\u0142 luk\u0119, zdo\u0142a\u0142 przygotowa\u0107 exploit do uzyskania praw root na systemach z j\u0105drami Linux 5.4 i nowszymi, udowodniono r\u00f3wnie\u017c mo\u017cliwo\u015b\u0107 przeprowadzenia udanego ataku na Ubuntu 20.04.02 LTS. Nie wyklucza si\u0119 mo\u017cliwo\u015bci przerobienia exploita, aby dzia\u0142a\u0142 r\u00f3wnie\u017c na starszych j\u0105drach (w j\u0105drze 5.4 kod CAN BCM (net\/can\/bcm.c) zosta\u0142 przet\u0142umaczony z hrtimer_tasklet na HRTIMER_MODE_SOFT). <\/p>\n

Protok\u00f3\u0142 CAN BCM pozwala zarejestrowa\u0107 w\u0142asny handler wiadomo\u015bci, kt\u00f3re przychodz\u0105 przez sie\u0107 CAN (controller area network), i przypi\u0105\u0107 go do okre\u015blonego gniazda sieciowego. Po przyj\u015bciu wiadomo\u015bci wywo\u0142ywana jest funkcja bcm_rx_handler(). Atakuj\u0105cy mo\u017ce wykorzysta\u0107 stan wy\u015bcigu i wymusi\u0107 zamkni\u0119cie gniazda sieciowego w momencie, gdy wykonywana jest bcm_rx_handler(). Podczas zamykania gniazda wywo\u0142ywana jest funkcja bcm_release(), w kt\u00f3rej zwalniana jest pami\u0119\u0107 przydzielona dla struktur bcm_op i bcm_sock, kt\u00f3re s\u0105 nadal u\u017cywane w wykonuj\u0105cym si\u0119 handlerze bcm_rx_handler(). Powstaje sytuacja prowadz\u0105ca do odniesienia si\u0119 do ju\u017c zwolnionego bloku pami\u0119ci (use-after-free). <\/p>\n

Atak polega na otwarciu dw\u00f3ch gniazd CAN BCM i powi\u0105zaniu ich z interfejsem vcan. W pierwszym gnie\u017adzie wykonywane jest wywo\u0142anie sendmsg() z flag\u0105 RX_SETUP w celu skonfigurowania handlera przychodz\u0105cych wiadomo\u015bci CAN, a w drugim gnie\u017adzie nast\u0119puje wywo\u0142anie sendmsg() do wys\u0142ania wiadomo\u015bci do pierwszego gniazda. Po przyj\u015bciu wiadomo\u015bci wywo\u0142ywana jest funkcja bcm_rx_handler(), a atakuj\u0105cy wybiera odpowiedni moment i zamyka pierwsze gniazdo, co prowadzi do uruchomienia bcm_release() i zwolnienia struktur bcm_op i bcm_sock, mimo \u017ce praca bcm_rx_handler() jeszcze si\u0119 nie zako\u0144czy\u0142a. <\/p>\n

\u0427\u0435\u0440\u0435\u0437 \u043c\u0430\u043d\u0438\u043f\u0443\u043b\u044f\u0446\u0438\u0438 \u0441 \u0441\u043e\u0434\u0435\u0440\u0436\u0438\u043c\u044b\u043c bcm_sock \u0430\u0442\u0430\u043a\u0443\u044e\u0449\u0438\u0439 \u043c\u043e\u0436\u0435\u0442 \u043f\u0435\u0440\u0435\u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0438\u0442\u044c \u0443\u043a\u0430\u0437\u0430\u0442\u0435\u043b\u044c \u043d\u0430 \u0444\u0443\u043d\u043a\u0446\u0438\u044e sk->sk_data_ready(sk), \u043f\u0435\u0440\u0435\u043d\u0430\u043f\u0440\u0430\u0432\u0438\u0442\u044c \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u0435 \u0438 \u043f\u0440\u0438 \u043f\u043e\u043c\u043e\u0449\u0438 \u043f\u0440\u0438\u0451\u043c\u043e\u0432 \u0432\u043e\u0437\u0432\u0440\u0430\u0442\u043d\u043e-\u043e\u0440\u0438\u0435\u043d\u0442\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u043e\u0433\u043e \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u0438\u0440\u043e\u0432\u0430\u043d\u0438\u044f (ROP — Return-Oriented Programming) \u043e\u0440\u0433\u0430\u043d\u0438\u0437\u043e\u0432\u0430\u0442\u044c \u043f\u0435\u0440\u0435\u0437\u0430\u043f\u0438\u0441\u044c \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u0430 modprobe_path \u0438 \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\u0440\u0430\u0432\u0430\u043c\u0438 root. \u041f\u0440\u0438 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u0438 \u0442\u0435\u0445\u043d\u0438\u043a\u0438 ROP \u0430\u0442\u0430\u043a\u0443\u044e\u0449\u0438\u0439 \u043d\u0435 \u043f\u044b\u0442\u0430\u0435\u0442\u0441\u044f \u0440\u0430\u0437\u043c\u0435\u0441\u0442\u0438\u0442\u044c \u0441\u0432\u043e\u0439 \u043a\u043e\u0434 \u0432 \u043f\u0430\u043c\u044f\u0442\u0438, \u0430 \u043e\u043f\u0435\u0440\u0438\u0440\u0443\u0435\u0442 \u0443\u0436\u0435 \u0438\u043c\u0435\u044e\u0449\u0438\u043c\u0438\u0441\u044f \u0432 \u0437\u0430\u0433\u0440\u0443\u0436\u0435\u043d\u043d\u044b\u0445 \u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a\u0430\u0445 \u043a\u0443\u0441\u043a\u0430\u043c\u0438 \u043c\u0430\u0448\u0438\u043d\u043d\u044b\u0445 \u0438\u043d\u0441\u0442\u0440\u0443\u043a\u0446\u0438\u0439, \u0437\u0430\u0432\u0435\u0440\u0448\u0430\u044e\u0449\u0438\u0445\u0441\u044f \u0438\u043d\u0441\u0442\u0440\u0443\u043a\u0446\u0438\u0435\u0439 \u0432\u043e\u0437\u0432\u0440\u0430\u0442\u0430 \u0443\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0438\u044f (\u043a\u0430\u043a \u043f\u0440\u0430\u0432\u0438\u043b\u043e, \u044d\u0442\u043e \u043e\u043a\u043e\u043d\u0447\u0430\u043d\u0438\u044f \u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u0447\u043d\u044b\u0445 \u0444\u0443\u043d\u043a\u0446\u0438\u0439). \u0420\u0430\u0431\u043e\u0442\u0430 \u044d\u043a\u0441\u043f\u043b\u043e\u0438\u0442\u0430 \u0441\u0432\u043e\u0434\u0438\u0442\u0441\u044f \u043a \u043f\u043e\u0441\u0442\u0440\u043e\u0435\u043d\u0438\u044e \u0446\u0435\u043f\u043e\u0447\u043a\u0438 \u0432\u044b\u0437\u043e\u0432\u043e\u0432 \u043f\u043e\u0434\u043e\u0431\u043d\u044b\u0445 \u0431\u043b\u043e\u043a\u043e\u0432 («\u0433\u0430\u0434\u0436\u0435\u0442\u043e\u0432») \u0434\u043b\u044f \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u0438\u044f \u043d\u0443\u0436\u043d\u043e\u0439 \u0444\u0443\u043d\u043a\u0446\u0438\u043e\u043d\u0430\u043b\u044c\u043d\u043e\u0441\u0442\u0438.

\"Vulnerability<\/center> <\/p>\n

Do przeprowadzenia ataku wymagany jest dost\u0119p do tworzenia gniazd CAN oraz skonfigurowany interfejs sieciowy vcan. Niezb\u0119dne uprawnienia do wykonania ataku mog\u0105 by\u0107 uzyskane przez nieuprzywilejowanego u\u017cytkownika w kontenerach, tworzonych w systemach z w\u0142\u0105czon\u0105 obs\u0142ug\u0105 przestrzeni nazw identyfikator\u00f3w u\u017cytkownik\u00f3w (user namespaces). Na przyk\u0142ad, user namespaces jest domy\u015blnie w\u0142\u0105czony w Ubuntu i Fedory, ale nieaktywny w Debianie i RHEL.
\n
\u0179r\u00f3d\u0142o: 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 \u044f\u0434\u0440\u0430 Linux \u0441 2.6.25 \u043f\u043e 5.13-rc6. \u0412 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445 \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u043f\u043e\u043a\u0430 \u043e\u0441\u0442\u0430\u0451\u0442\u0441\u044f \u043d\u0435\u0438\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u043d\u043e\u0439 (RHEL, Fedora, Debian, Ubuntu, SUSE, Arch). \u0412\u044b\u044f\u0432\u0438\u0432\u0448\u0438\u0439 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0438\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u044c \u0441\u043c\u043e\u0433 \u043f\u043e\u0434\u0433\u043e\u0442\u043e\u0432\u0438\u0442\u044c \u044d\u043a\u0441\u043f\u043b\u043e\u0438\u0442 \u0434\u043b\u044f \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u0438\u044f \u043f\u0440\u0430\u0432 root […]<\/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\udd47Luka w j\u0105drze Linux, dotycz\u0105ca protoko\u0142u sieciowego CAN BCM | ProHoster","description":"W j\u0105drze Linux zidentyfikowano luk\u0119 (CVE-2021-3609), kt\u00f3ra pozwala lokalnemu u\u017cytkownikowi podnie\u015b\u0107 swoje uprawnienia w 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