{"id":103636,"date":"2022-03-27T15:36:39","date_gmt":"2022-03-27T13:36:39","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-zlib-proyavlyayushhayasya-pri-szhatii-speczialno-oformlennyh-dannyh"},"modified":"2022-03-27T15:36:39","modified_gmt":"2022-03-27T13:36:39","slug":"uyazvimost-v-zlib-proyavlyayushhayasya-pri-szhatii-speczialno-oformlennyh-dannyh","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/uyazvimost-v-zlib-proyavlyayushhayasya-pri-szhatii-speczialno-oformlennyh-dannyh","title":{"rendered":"Zranitelnost v zlib, projevuj\u00edc\u00ed se p\u0159i kompresi speci\u00e1ln\u011b upraven\u00fdch dat","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V knihovn\u011b zlib byla zji\u0161t\u011bna zranitelnost (CVE-2018-25032), kter\u00e1 vede k p\u0159ete\u010den\u00ed bufferu p\u0159i pokusu o kompresi speci\u00e1ln\u011b p\u0159ipraven\u00e9 sekvence znak\u016f ve vstupn\u00edch datech. V sou\u010dasn\u00e9 podob\u011b byla v\u00fdzkumn\u00edky prok\u00e1z\u00e1na mo\u017enost zp\u016fsoben\u00ed hav\u00e1rie procesu. Zda probl\u00e9m m\u016f\u017ee m\u00edt z\u00e1va\u017en\u011bj\u0161\u00ed d\u016fsledky, zat\u00edm nebylo zkoum\u00e1no. <\/p>\n

Zranitelnost se projevuje od verze zlib 1.2.2.2 a t\u00fdk\u00e1 se mimo jin\u00e9 i aktu\u00e1ln\u00edho vyd\u00e1n\u00ed zlib 1.2.11. Zaj\u00edmav\u00e9 je, \u017ee oprava zranitelnosti byla navr\u017eena ji\u017e v roce 2018, ale v\u00fdvoj\u00e1\u0159i ji ignorovali a nevydali opravnou verzi (knihovna zlib byla naposledy aktualizov\u00e1na v roce 2017). Oprava tak\u00e9 dosud nebyla zahrnuta do bal\u00ed\u010dk\u016f poskytovan\u00fdch distribucemi. Sledovat publikaci oprav distribucemi lze na t\u011bchto str\u00e1nk\u00e1ch: Debian, RHEL, Fedora, SUSE, Ubuntu, Arch Linux, OpenBSD, FreeBSD, NetBSD. Knihovna zlib-ng nen\u00ed t\u00e9to probl\u00e9mem ohro\u017eena. <\/p>\n

Zranitelnost se projevuje, pokud ve vstupn\u00edm proudu nastane velk\u00e9 mno\u017estv\u00ed shodn\u00fdch vzor\u016f, kter\u00e9 maj\u00ed b\u00fdt zabalov\u00e1ny, a na n\u011b\u017e se aplikuje komprese na z\u00e1klad\u011b pevn\u00fdch k\u00f3d\u016f Huffmana. P\u0159i ur\u010dit\u00fdch okolnostech m\u016f\u017ee obsah mezipam\u011bti, do kter\u00e9 se ukl\u00e1d\u00e1 zkomprimovan\u00fd v\u00fdsledek, kolidovat s pam\u011bt\u00ed, ve kter\u00e9 je ulo\u017eena tabulka frekvenc\u00ed znak\u016f. V d\u016fsledku toho se pozoruje vytv\u00e1\u0159en\u00ed nespr\u00e1vn\u00fdch zkomprimovan\u00fdch dat a selh\u00e1n\u00ed kv\u016fli z\u00e1pisu mimo hranice bufferu. <\/p>\n

Zranitelnost m\u016f\u017ee b\u00fdt zneu\u017eita pouze p\u0159i pou\u017eit\u00ed kompresn\u00ed strategie na z\u00e1klad\u011b pevn\u00fdch k\u00f3d\u016f Huffmana. Takov\u00e1 strategie je vybr\u00e1na p\u0159i explicitn\u00edm zapnut\u00ed mo\u017enosti Z_FIXED v k\u00f3du (p\u0159\u00edklad sekvence, kter\u00e1 vede k hav\u00e1rii p\u0159i pou\u017eit\u00ed mo\u017enosti Z_FIXED). Podle k\u00f3du m\u016f\u017ee b\u00fdt strategie Z_FIXED tak\u00e9 vybr\u00e1na automaticky, pokud maj\u00ed optim\u00e1ln\u00ed a statick\u00e9 stromy vy\u010d\u00edslen\u00e9 pro data stejnou velikost. <\/p>\n

Nen\u00ed jasn\u00e9, zda lze p\u0159izp\u016fsobit podm\u00ednky pro zneu\u017eit\u00ed zranitelnosti p\u0159i pou\u017eit\u00ed kompresn\u00ed strategie Z_DEFAULT_STRATEGY, kter\u00e1 se pou\u017e\u00edv\u00e1 jako v\u00fdchoz\u00ed. Pokud ne, zranitelnost bude omezena na jednotliv\u00e9 specifick\u00e9 syst\u00e9my, ve kter\u00fdch je explicitn\u011b nastavena volba Z_FIXED. Pokud ano, mohou b\u00fdt \u0161kody zp\u016fsoben\u00e9 zranitelnost\u00ed velmi v\u00fdznamn\u00e9, nebo\u0165 knihovna zlib je de facto standardem a pou\u017e\u00edv\u00e1 se v mnoha popul\u00e1rn\u00edch projektech, v\u010detn\u011b j\u00e1dra Linux, OpenSSH, OpenSSL, apache httpd, libpng, FFmpeg, rsync, dpkg, rpm, Git, PostgreSQL, MySQL atd.
\n
Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a\u0435 zlib \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2018-25032), \u043f\u0440\u0438\u0432\u043e\u0434\u044f\u0449\u0430\u044f \u043a \u043f\u0435\u0440\u0435\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044e \u0431\u0443\u0444\u0435\u0440\u0430 \u043f\u0440\u0438 \u043f\u043e\u043f\u044b\u0442\u043a\u0435 \u0441\u0436\u0430\u0442\u0438\u044f \u0441\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u043e \u043f\u043e\u0434\u0433\u043e\u0442\u043e\u0432\u043b\u0435\u043d\u043d\u043e\u0439 \u043f\u043e\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u044c\u043d\u043e\u0441\u0442\u0438 \u0441\u0438\u043c\u0432\u043e\u043b\u043e\u0432 \u0432\u043e \u0432\u0445\u043e\u0434\u044f\u0449\u0438\u0445 \u0434\u0430\u043d\u043d\u044b\u0445. \u0412 \u0442\u0435\u043a\u0443\u0449\u0435\u043c \u0432\u0438\u0434\u0435 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\u0441 \u0432\u0435\u0440\u0441\u0438\u0438 zlib 1.2.2.2 \u0438 \u0437\u0430\u0442\u0440\u0430\u0433\u0438\u0432\u0430\u0435\u0442 \u0432 \u0442\u043e\u043c \u0447\u0438\u0441\u043b\u0435 \u0430\u043a\u0442\u0443\u0430\u043b\u044c\u043d\u044b\u0439 \u0432\u044b\u043f\u0443\u0441\u043a zlib […]<\/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-103636","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\udd47Zranitelnost v zlib, projevuj\u00edc\u00ed se p\u0159i kompresi speci\u00e1ln\u011b upraven\u00fdch dat | ProHoster","description":"V 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