{"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\/cs\/blog\/news\/root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os","title":{"rendered":"Root zranitelnost v sudo, ovliv\u0148uj\u00edc\u00ed Linux Mint a Elementary OS.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V n\u00e1stroji sudo<\/a><\/noindex>, pou\u017e\u00edvan\u00e9 k organizaci prov\u00e1d\u011bn\u00ed p\u0159\u00edkaz\u016f jm\u00e9nem jin\u00fdch u\u017eivatel\u016f, byla odhalena<\/a><\/noindex> zranitelnost (CVE-2019-18634<\/a><\/noindex>), kter\u00e1 umo\u017e\u0148uje zv\u00fd\u0161it sv\u00e9 privilegium v syst\u00e9mu na u\u017eivatele root. Probl\u00e9m se projevuje od verze sudo 1.7.1 pouze p\u0159i pou\u017eit\u00ed v souboru \/etc\/sudoers volby «pwfeedback», kter\u00e1 je ve v\u00fdchoz\u00edm stavu deaktivov\u00e1na, ale je aktivov\u00e1na v n\u011bkter\u00fdch distribuc\u00edch, jako jsou Linux Mint a Elementary OS. Probl\u00e9m byl odstran\u011bn v verzi sudo 1.8.31<\/a><\/noindex>, vydan\u00e9m p\u0159ed n\u011bkolika hodinami. V distribuc\u00edch z\u016fst\u00e1v\u00e1 zranitelnost zat\u00edm neopraven\u00e1.<\/p>\n

Volba «pwfeedback» zahrnuje zobrazen\u00ed symbolu «*» po ka\u017ed\u00e9m zadan\u00e9m znaku p\u0159i zad\u00e1v\u00e1n\u00ed hesla. V d\u016fsledku chyb\u011b<\/a><\/noindex> v implementaci funkce getln(), definovan\u00e9 v souboru tgetpass.c, m\u016f\u017ee b\u00fdt p\u0159edan\u00fd p\u0159es standardn\u00ed vstup (stdin) p\u0159\u00edli\u0161 dlouh\u00fd \u0159et\u011bzec hesla za ur\u010dit\u00fdch podm\u00ednek zaps\u00e1n do vyhrazen\u00e9ho bufferu a p\u0159epsat dal\u0161\u00ed data na z\u00e1sobn\u00edku. P\u0159ete\u010den\u00ed nast\u00e1v\u00e1 b\u011bhem prov\u00e1d\u011bn\u00ed k\u00f3du sudo s pr\u00e1vy root.<\/p>\n

Podstatou probl\u00e9mu je, \u017ee p\u0159i pou\u017eit\u00ed speci\u00e1ln\u00edho znaku ^U (vy\u010di\u0161t\u011bn\u00ed \u0159\u00e1dku) b\u011bhem zad\u00e1v\u00e1n\u00ed, a p\u0159i selh\u00e1n\u00ed operace z\u00e1pisu, k\u00f3d odpov\u011bdn\u00fd za vy\u010di\u0161t\u011bn\u00ed zobrazen\u00fdch znak\u016f «*» resetuje \u00fadaje o dostupn\u00e9 velikosti vyrovn\u00e1vac\u00ed pam\u011bti, ale nevr\u00e1t\u00ed do p\u016fvodn\u00edho stavu ukazatel na aktu\u00e1ln\u00ed pozici v pam\u011bti. Dal\u0161\u00edm faktorem p\u0159isp\u00edvaj\u00edc\u00edm k exploataci je nedostatek automatick\u00e9ho vypnut\u00ed re\u017eimu «pwfeedback» p\u0159i p\u0159\u00edchodu dat nikoli z termin\u00e1lu, ale prost\u0159ednictv\u00edm vstupn\u00edho proudu (tato nedostate\u010dnost umo\u017e\u0148uje vytvo\u0159it podm\u00ednky pro vznik chyby z\u00e1pisu, nap\u0159\u00edklad na syst\u00e9mech s jednosm\u011brn\u00fdmi bezjmenn\u00fdmi kan\u00e1ly<\/a><\/noindex> chyba nast\u00e1v\u00e1 p\u0159i pokusu o z\u00e1pis za konec kan\u00e1lu pro \u010dten\u00ed).<\/p>\n

Jeliko\u017e \u00fato\u010dn\u00edk m\u016f\u017ee pln\u011b \u0159\u00eddit p\u0159eps\u00e1n\u00ed dat v z\u00e1sobn\u00edku, nen\u00ed obt\u00ed\u017en\u00e9 vytvo\u0159it exploit, kter\u00fd umo\u017e\u0148uje zv\u00fd\u0161it sv\u00e9 privilegium na u\u017eivatele root. Probl\u00e9m m\u016f\u017ee b\u00fdt explotov\u00e1n jak\u00fdmkoli u\u017eivatelem, bez ohledu na pr\u00e1va na pou\u017e\u00edv\u00e1n\u00ed sudo a p\u0159\u00edtomnost specifick\u00fdch nastaven\u00ed u\u017eivatele v sudoers. Pro zablokov\u00e1n\u00ed probl\u00e9mu se doporu\u010duje zajistit, aby volba «pwfeedback» neexistovala v \/etc\/sudoers, a v p\u0159\u00edpad\u011b pot\u0159eby ji deaktivovat («Defaults !pwfeedback»). K ov\u011b\u0159en\u00ed p\u0159\u00edtomnosti probl\u00e9mu lze spustit k\u00f3d:<\/p>\n

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

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

Zdroj: 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 zranitelnost v sudo, kter\u00e1 se t\u00fdk\u00e1 Linux Mint a Elementary OS | ProHoster","description":"V utilit\u011b sudo, pou\u017e\u00edvan\u00e9 k organizaci vykon\u00e1v\u00e1n\u00ed p\u0159\u00edkaz\u016f jm\u00e9nem jin\u00fdch 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