{"id":55921,"date":"2020-02-01T00:00:00","date_gmt":"2020-01-31T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os"},"modified":"2020-02-18T14:04:05","modified_gmt":"2020-02-18T11:04:05","slug":"root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os","status":"publish","type":"post","link":"https:\/\/prohoster.info\/da\/blog\/news\/root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os","title":{"rendered":"Root-s\u00e5rbarhed i sudo, der p\u00e5virker Linux Mint og Elementary OS","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

I v\u00e6rkt\u00f8jet sudo<\/a><\/noindex>, der anvendes til at organisere udf\u00f8relse af kommandoer p\u00e5 vegne af andre brugere, opdaget<\/a><\/noindex> s\u00e5rbarhed (CVE-2019-18634<\/a><\/noindex>), som giver mulighed for at h\u00e6ve sine privilegier i systemet til root-bruger. Problemet optr\u00e6der fra udgivelsen af sudo 1.7.1, men kun n\u00e5r indstillingen «pwfeedback» anvendes i filen \/etc\/sudoers, som er deaktiveret som standard, men aktiveret i nogle distributioner som Linux Mint og Elementary OS. Problemet er blevet l\u00f8st i udgivelsen sudo 1.8.31<\/a><\/noindex>, offentliggjort for f\u00e5 timer siden. I distributionerne er s\u00e5rbarheden stadig ubehandlet.<\/p>\n

Indstillingen «pwfeedback» aktiverer visningen af symbolet «*» efter hvert indtastet tegn, n\u00e5r der indtastes en adgangskode. P\u00e5 grund af fejlen<\/a><\/noindex> implementeringen af funktionen getln(), defineret i filen tgetpass.c, kan en for stor streng med adgangskoden, der sendes via standard input (stdin), under visse betingelser ikke passe ind i den tildelte buffer og overskrive andre data p\u00e5 stakken. Overskrivningen opst\u00e5r under udf\u00f8relsen af sudo-kode med root-rettigheder.<\/p>\n

Kernen i problemet er, at n\u00e5r specialtegnet ^U (rydder linjen) bruges under indtastning, og der opst\u00e5r en fejl i skriveoperationen, s\u00e5 nulstiller koden, der h\u00e5ndterer rydningen af de viste «*» tegn, oplysningerne om den tilg\u00e6ngelige st\u00f8rrelsesbuffer, men bringer ikke pekeren p\u00e5 den aktuelle position i bufferen tilbage til dens oprindelige v\u00e6rdi. En anden faktor, der muligg\u00f8r udnyttelse, er manglen p\u00e5 automatisk deaktivering af «pwfeedback» ved modtagelse af data, der ikke kommer fra terminalen, men gennem en inputstr\u00f8m (denne manglende funktionalitet muligg\u00f8r, at der kan opst\u00e5 en skrivefejl, for eksempel p\u00e5 systemer med envejs anonyme r\u00f8r<\/a><\/noindex> fejlen opst\u00e5r ved fors\u00f8g p\u00e5 at skrive forbi enden af r\u00f8ret til l\u00e6sning).<\/p>\n

Da angriberen kan kontrollere overskrivningen af data i stakken fuldt ud, er det ikke vanskeligt at skabe et exploit, der muligg\u00f8r at h\u00e6ve sine privilegier til root-bruger. Problemet kan udnyttes af enhver bruger, uanset rettighederne til at bruge sudo og de specifikke indstillinger i sudoers. For at blokere problemet b\u00f8r man sikre sig, at indstillingen «pwfeedback» ikke er til stede i \/etc\/sudoers og deaktivere den om n\u00f8dvendigt («Defaults !pwfeedback»). For at kontrollere forekomsten af problemet kan koden udf\u00f8res:<\/p>\n

$ perl -e ‘print((«A» x 100 . «\x{00}») x 50)’ | sudo -S id
\n Adgangskode: Segmenteringsfejl<\/p>\n

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

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

\u0412 \u0443\u0442\u0438\u043b\u0438\u0442\u0435 sudo, \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u0435\u043c\u043e\u0439 \u0434\u043b\u044f \u043e\u0440\u0433\u0430\u043d\u0438\u0437\u0430\u0446\u0438\u0438 \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f \u043a\u043e\u043c\u0430\u043d\u0434 \u043e\u0442 \u0438\u043c\u0435\u043d\u0438 \u0434\u0440\u0443\u0433\u0438\u0445 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2019-18634), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043f\u043e\u0432\u044b\u0441\u0438\u0442\u044c \u0441\u0432\u043e\u0438 \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0438 \u0432 \u0441\u0438\u0441\u0442\u0435\u043c\u0435 \u0434\u043e \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u044f root. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u043f\u0440\u043e\u044f\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u043d\u0430\u0447\u0438\u043d\u0430\u044f \u0441 \u0432\u044b\u043f\u0443\u0441\u043a\u0430 sudo 1.7.1 \u0442\u043e\u043b\u044c\u043a\u043e \u043f\u0440\u0438 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u0438 \u0432 \u0444\u0430\u0439\u043b\u0435 \/etc\/sudoers \u043e\u043f\u0446\u0438\u0438 «pwfeedback», \u043a\u043e\u0442\u043e\u0440\u0430\u044f \u043e\u0442\u043a\u043b\u044e\u0447\u0435\u043d\u0430 \u043f\u043e \u0443\u043c\u043e\u043b\u0447\u0430\u043d\u0438\u044e, \u043d\u043e \u0430\u043a\u0442\u0438\u0432\u0438\u0440\u043e\u0432\u0430\u043d\u0430 \u0432 \u043d\u0435\u043a\u043e\u0442\u043e\u0440\u044b\u0445 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445, \u0442\u0430\u043a\u0438\u0445 \u043a\u0430\u043a Linux Mint \u0438 Elementary OS. […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-55921","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\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\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Root-s\u00e5rbarhed i sudo, der p\u00e5virker Linux Mint og Elementary OS | ProHoster","description":"I sudo-v\u00e6rkt\u00f8jet, der bruges til at udf\u00f8re kommandoer p\u00e5 vegne af andre 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