{"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\/no\/blog\/news\/root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os","title":{"rendered":"Root-s\u00e5rbarhet i sudo som p\u00e5virker Linux Mint og Elementary OS","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

I verkt\u00f8yet sudo<\/a><\/noindex>, som brukes til \u00e5 organisere utf\u00f8relse av kommandoer p\u00e5 vegne av andre brukere, oppdaget<\/a><\/noindex> s\u00e5rbarhet (CVE-2019-18634<\/a><\/noindex>), som lar deg heve privilegiene dine i systemet til root-bruker. Problemet viser seg fra utgaven av sudo 1.7.1, kun n\u00e5r alternativet \u00abpwfeedback\u00bb brukes i filen \/etc\/sudoers, noe som er deaktivert som standard, men aktivert i noen distribusjoner som Linux Mint og Elementary OS. Problemet er utbedret i utgaven sudo 1.8.31<\/a><\/noindex>, som ble publisert for noen timer siden. I distribusjoner er s\u00e5rbarheten fortsatt uopprettet.<\/p>\n

Alternativet \u00abpwfeedback\u00bb aktiverer visning av symbolet \u00ab*\u00bb etter hvert inntastet tegn n\u00e5r du skriver inn passord. P\u00e5 grunn av feilen<\/a><\/noindex> implementeringen i funksjonen getln(), definert i filen tgetpass.c, kan en for stor streng med passord sendt via standard inndata (stdin) under visse forhold ikke passe inn i den tildelte bufferen og overskrive andre data p\u00e5 stakken. Overl\u00f8pet skjer under utf\u00f8relsen av sudo-kode med root-rettigheter.<\/p>\n

Essensen av problemet ligger i at ved bruk av spesialtegnet ^U (rens av linjen) under inntasting, og ved et skriveoperasjonsfeil, tilbakestiller koden som er ansvarlig for \u00e5 rengj\u00f8re de utskrevne tegnene \u00ab*\u00bb tilgjengelig bufferst\u00f8rrelse, men returnerer ikke pekeren til den gjeldende posisjonen i bufferen til sin opprinnelige verdi. En annen faktor som bidrar til utnytting er frav\u00e6ret av automatisk deaktivering av \u00abpwfeedback\u00bb-modus n\u00e5r dataene mottas ikke fra terminalen, men via inngangsstr\u00f8m (denne mangelen skaper forhold for en skrivefeil, for eksempel p\u00e5 systemer med ensrettede uidentifiserte kanaler<\/a><\/noindex> feilen oppst\u00e5r n\u00e5r det fors\u00f8kes \u00e5 skrive utover slutten av kanalen for lesing).<\/p>\n

Siden angriperen kan kontrollere gjenopprettingen av data i stakken fullstendig, er det ikke vanskelig \u00e5 lage et exploit som lar dem heve privilegiene til root-bruker. Problemet kan utnyttes av enhver bruker, uavhengig av rettigheter til \u00e5 bruke sudo og spesifikke brukerinnstillinger i sudoers. For \u00e5 blokkere problemet m\u00e5 du s\u00f8rge for at det ikke finnes noen innstillinger for \u00abpwfeedback\u00bb i \/etc\/sudoers, og om n\u00f8dvendig deaktivere den (\u00abDefaults !pwfeedback\u00bb). For \u00e5 sjekke om det er et problem, kan du kj\u00f8re koden:<\/p>\n

$ perl -e 'print((\u00abA\u00bb x 100 . \u00ab\u00bb) x 50)' | sudo -S id
\n Passord: Segmenteringsfeil<\/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-svakhet i sudo som p\u00e5verkar Linux Mint og Elementary OS | ProHoster","description":"I verkt\u00f8yet sudo, brukt for \u00e5 organisere utf\u00f8relsen av kommandoer p\u00e5 vegne av andre 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