{"id":55016,"date":"2020-01-10T00:00:00","date_gmt":"2020-01-09T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/uyazvimost-v-e2fsck-proyavlyayushhayasya-pri-obrabotke-spetsialno-oformlennyh-katalogov"},"modified":"2020-02-18T14:03:05","modified_gmt":"2020-02-18T11:03:05","slug":"uyazvimost-v-e2fsck-proyavlyayushhayasya-pri-obrabotke-spetsialno-oformlennyh-katalogov","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/uyazvimost-v-e2fsck-proyavlyayushhayasya-pri-obrabotke-spetsialno-oformlennyh-katalogov","title":{"rendered":"Zranitelnost v e2fsck, projevuj\u00edc\u00ed se p\u0159i zpracov\u00e1n\u00ed speci\u00e1ln\u011b upraven\u00fdch adres\u00e1\u0159\u016f","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V utilit\u011b e2fsck dod\u00e1van\u00e9 v r\u00e1mci bal\u00ed\u010dku e2fsprogs<\/a><\/noindex>, byla odhalena<\/a><\/noindex> zranitelnost<\/a><\/noindex> (CVE-2019-5188<\/a><\/noindex>), kter\u00e1 umo\u017e\u0148uje zneu\u017eit\u00ed k\u00f3du \u00fato\u010dn\u00edka p\u0159i kontrole souborov\u00e9ho syst\u00e9mu obsahuj\u00edc\u00edho speci\u00e1ln\u011b form\u00e1tovan\u00e9 adres\u00e1\u0159e. P\u0159\u00edtomnost zranitelnosti byla potvrzena v verz\u00edch od 1.43.3 do 1.45.4. Zranitelnost byla odstran\u011bna v aktualizaci e2fsck 1.45.5<\/a><\/noindex>. V distribuc\u00edch z\u016fst\u00e1v\u00e1 probl\u00e9m zat\u00edm neopraven\u00fd (Debian<\/a><\/noindex>, Arch Linux<\/a><\/noindex>, SUSE\/openSUSE<\/a><\/noindex>, Ubuntu<\/a><\/noindex>, RHEL<\/a><\/noindex>).<\/p>\n

Zranitelnost je zp\u016fsobena chybou ve funkci mutate_name() z souboru rehash.c, kter\u00e1 se pou\u017e\u00edv\u00e1 p\u0159i rekonstruov\u00e1n\u00ed hash tabulek spojen\u00fdch s adres\u00e1\u0159em, je\u017e zaji\u0161\u0165uj\u00ed mapov\u00e1n\u00ed v\u0161ech soubor\u016f, kter\u00e9 se v n\u011bm nach\u00e1zej\u00ed. Po\u0161kozen\u00ed struktury hash_entry spojen\u00e9 s adres\u00e1\u0159em m\u016f\u017ee v\u00e9st k z\u00e1pisu dat \u00fato\u010dn\u00edka do oblasti mimo p\u0159id\u011blen\u00fd buffer. V p\u0159\u00edpad\u011b, \u017ee je v hash tabulce vazba na adres\u00e1\u0159 s n\u011bkolika soubory se stejn\u00fdm n\u00e1zvem, utilita e2fsck p\u0159ejmenuje duplicitn\u00ed soubory p\u0159id\u00e1n\u00edm k n\u00e1zvu ~0, ~1 atd. Pro do\u010dasn\u00e9 ulo\u017een\u00ed nov\u00e9ho n\u00e1zvu p\u0159i takov\u00e9m p\u0159ejmenov\u00e1v\u00e1n\u00ed se na z\u00e1sobn\u00edku vy\u010dle\u0148uje buffer o velikosti 256 byt\u016f. <\/p>\n

Velikost kop\u00edrovan\u00fdch dat je ur\u010dena v\u00fdrazem «entry->name_len & 0xff», ale hodnota entry->name_len se na\u010d\u00edt\u00e1 ze struktury na disku, nikoliv se vypo\u010d\u00edt\u00e1v\u00e1 na z\u00e1klad\u011b skute\u010dn\u00e9 velikosti n\u00e1zvu. Pokud je velikost nulov\u00e1, pak index pole nab\u00fdv\u00e1 hodnoty -1 a vytv\u00e1\u0159\u00ed se podm\u00ednky pro celo\u010d\u00edseln\u00e9 podte\u010den\u00ed (integer underflow) a p\u0159eps\u00e1n\u00ed jin\u00fdch dat na z\u00e1sobn\u00edku hodnotou «~0». Pro 64bitov\u00e9 syst\u00e9my je zneu\u017eit\u00ed t\u00e9to zranitelnosti hodnoceno jako m\u00e1lo pravd\u011bpodobn\u00e9 a vy\u017eaduje absenci omezen\u00ed velikosti z\u00e1sobn\u00edku (ulimit -s unlimited). Pro 32bitov\u00e9 syst\u00e9my je zneu\u017eit\u00ed pova\u017eov\u00e1no za mo\u017en\u00e9, ale v\u00fdsledek siln\u011b z\u00e1vis\u00ed na tom, jak byl spustiteln\u00fd soubor sestaven kompil\u00e1torem.<\/p>\n

Pro proveden\u00ed \u00fatoku mus\u00ed \u00fato\u010dn\u00edk ur\u010dit\u00fdm zp\u016fsobem po\u0161kodit data v \u010d\u00e1sti s FS ext2, ext3 nebo ext4. Jeliko\u017e tato operace vy\u017eaduje privilegium superu\u017eivatele, zranitelnost p\u0159edstavuje hrozbu p\u0159i kontrole extern\u00edch jednotek nebo obraz\u016f FS z\u00edskan\u00fdch z vn\u011bj\u0161\u00edch zdroj\u016f utilitou e2fsck.<\/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 e2fsck, \u043f\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u043c\u043e\u0439 \u0432 \u0441\u043e\u0441\u0442\u0430\u0432\u0435 \u043f\u0430\u043a\u0435\u0442\u0430 e2fsprogs, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2019-5188), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u0434\u043e\u0431\u0438\u0442\u044c\u0441\u044f \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f \u043a\u043e\u0434\u0430 \u0437\u043b\u043e\u0443\u043c\u044b\u0448\u043b\u0435\u043d\u043d\u0438\u043a\u0430 \u043f\u0440\u0438 \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u0438 \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 \u0444\u0430\u0439\u043b\u043e\u0432\u043e\u0439 \u0441\u0438\u0441\u0442\u0435\u043c\u044b, \u0441\u043e\u0434\u0435\u0440\u0436\u0430\u0449\u0435\u0439 \u0441\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u044b\u043c \u043e\u0431\u0440\u0430\u0437\u043e\u043c \u043e\u0444\u043e\u0440\u043c\u043b\u0435\u043d\u043d\u044b\u0435 \u043a\u0430\u0442\u0430\u043b\u043e\u0433\u0438. \u041d\u0430\u043b\u0438\u0447\u0438\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u043f\u043e\u0434\u0442\u0432\u0435\u0440\u0436\u0434\u0435\u043d\u043e \u0432 \u0432\u044b\u043f\u0443\u0441\u043a\u0430\u0445 \u0441 1.43.3 \u043f\u043e 1.45.4. \u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0430 \u0432 \u043e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u0438 e2fsck 1.45.5. \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 (Debian, Arch Linux, SUSE\/openSUSE, Ubuntu, RHEL). 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