{"id":34748,"date":"2019-10-31T22:00:11","date_gmt":"2019-10-31T19:00:11","guid":{"rendered":"https:\/\/prohoster.info\/blog\/uyazvimost-v-docker-pozvolyayushhaya-vybratsya-iz-kontejnera\/"},"modified":"2019-10-31T22:00:11","modified_gmt":"2019-10-31T19:00:11","slug":"uyazvimost-v-docker-pozvolyayushhaya-vybratsya-iz-kontejnera","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/uyazvimost-v-docker-pozvolyayushhaya-vybratsya-iz-kontejnera","title":{"rendered":"Zranitelnost v Dockeru, kter\u00e1 umo\u017e\u0148uje uniknout z kontejneru","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

N\u00e1stroje pro spr\u00e1vu izolovan\u00fdch Linuxov\u00fdch kontejner\u016f Docker byla odhalena<\/a><\/noindex> zranitelnost (CVE-2018-15664<\/a><\/noindex>), kter\u00e1 za ur\u010dit\u00fdch okolnost\u00ed umo\u017e\u0148uje p\u0159\u00edstup k hostitelsk\u00e9mu prost\u0159ed\u00ed z kontejneru za p\u0159edpokladu, \u017ee je mo\u017en\u00e9 spou\u0161t\u011bt vlastn\u00ed obrazy v syst\u00e9mu nebo p\u0159i p\u0159\u00edstupu k b\u011b\u017e\u00edc\u00edmu kontejneru. Probl\u00e9m se projevuje ve v\u0161ech verz\u00edch Dockeru a z\u016fst\u00e1v\u00e1 neopraviteln\u00fd (n\u00e1vrh byl p\u0159edlo\u017een, ale zat\u00edm nebyl schv\u00e1len, patch<\/a><\/noindex>, implementuj\u00edc\u00ed pozastaven\u00ed b\u011bhu kontejneru b\u011bhem prov\u00e1d\u011bn\u00ed operac\u00ed se souborov\u00fdm syst\u00e9mem).<\/p>\n

Zranitelnost umo\u017e\u0148uje extrakci soubor\u016f z kontejneru do libovoln\u00e9 \u010d\u00e1sti souborov\u00e9ho syst\u00e9mu hostitelsk\u00e9 syst\u00e9m p\u0159i proveden\u00ed p\u0159\u00edkazu «docker cp». Extrakce soubor\u016f se prov\u00e1d\u00ed s opr\u00e1vn\u011bn\u00edmi root, co\u017e umo\u017e\u0148uje \u010d\u00edst nebo zapisovat jak\u00e9koli soubory v hostitelsk\u00e9m prost\u0159ed\u00ed, co\u017e je dostate\u010dn\u00e9 k z\u00edsk\u00e1n\u00ed kontroly nad hostitelsk\u00fdm syst\u00e9mem (nap\u0159\u00edklad lze p\u0159epsat \/etc\/shadow). <\/p>\n

\u00datok m\u016f\u017ee b\u00fdt proveden pouze v moment\u011b, kdy administr\u00e1tor prov\u00e1d\u00ed p\u0159\u00edkaz «docker cp» pro kop\u00edrov\u00e1n\u00ed soubor\u016f do kontejneru nebo z n\u011bj. T\u00edmto zp\u016fsobem se \u00fato\u010dn\u00edk mus\u00ed n\u011bjak\u00fdm zp\u016fsobem p\u0159esv\u011bd\u010dit administr\u00e1tora Docker o nutnosti proveden\u00ed t\u00e9to operace a p\u0159edpov\u011bd\u011bt pou\u017eitou cestu pro kop\u00edrov\u00e1n\u00ed. Na druhou stranu m\u016f\u017ee b\u00fdt \u00fatok proveden nap\u0159\u00edklad p\u0159i poskytov\u00e1n\u00ed cloudov\u00fdmi slu\u017ebami prost\u0159edk\u016f pro kop\u00edrov\u00e1n\u00ed konfigura\u010dn\u00edch soubor\u016f do kontejneru, vytvo\u0159en\u00fdch s vyu\u017eit\u00edm p\u0159\u00edkazu «docker cp».<\/p>\n

Probl\u00e9m je zp\u016fsoben nedostatkem v aplikaci funkce FollowSymlinkInScope<\/a><\/noindex>, vy\u017eaduj\u00edc\u00ed absolutn\u00ed cestu v hlavn\u00edm souborov\u00e9m syst\u00e9mu na z\u00e1klad\u011b relativn\u00ed cesty, berouc\u00ed v \u00favahu um\u00edst\u011bn\u00ed kontejneru. B\u011bhem prov\u00e1d\u011bn\u00ed p\u0159\u00edkazu «docker cp» nast\u00e1v\u00e1 kr\u00e1tkodob\u00e9 souborov\u00fd z\u00e1vod<\/a><\/noindex>, kdy byla cesta ji\u017e ov\u011b\u0159ena, ale operace je\u0161t\u011b nebyla provedena. Proto\u017ee kop\u00edrov\u00e1n\u00ed prob\u00edh\u00e1 v kontextu hlavn\u00edho souborov\u00e9ho syst\u00e9mu hostitelsk\u00e9, v uveden\u00e9m \u010dasov\u00e9m rozmez\u00ed je mo\u017en\u00e9 vym\u011bnit odkaz na jinou cestu a iniciovat kop\u00edrov\u00e1n\u00ed dat do libovoln\u00e9ho m\u00edsta souborov\u00e9ho syst\u00e9mu mimo kontejner.<\/p>\n

Jeliko\u017e je doba projevu z\u00e1vodn\u00edho stavu siln\u011b omezena v p\u0159ipraven\u00e9m prototypu exploit<\/a><\/noindex> p\u0159i prov\u00e1d\u011bn\u00ed operac\u00ed kop\u00edrov\u00e1n\u00ed z kontejneru se poda\u0159ilo dos\u00e1hnout \u00fasp\u011b\u0161n\u00e9ho \u00fatoku m\u00e9n\u011b ne\u017e v 1 % p\u0159\u00edpad\u016f p\u0159i cyklick\u00e9 v\u00fdm\u011bn\u011b symbolick\u00e9 vazby v cest\u011b, pou\u017e\u00edvan\u00e9 v operaci kop\u00edrov\u00e1n\u00ed (\u00fasp\u011b\u0161n\u00fd \u00fatok byl proveden po zhruba 10 sekund\u00e1ch pokus\u016f neust\u00e1le v cyklu zkop\u00edrovat soubor pomoc\u00ed p\u0159\u00edkazu «docker cp»).<\/p>\n

P\u0159i prov\u00e1d\u011bn\u00ed operace kop\u00edrov\u00e1n\u00ed do kontejneru lze dos\u00e1hnout opakovateln\u00e9ho \u00fatoku na p\u0159eps\u00e1n\u00ed souboru v hostitelsk\u00e9m syst\u00e9mu b\u011bhem n\u011bkolika iterac\u00ed. Mo\u017enost \u00fatoku souvis\u00ed s t\u00edm, \u017ee p\u0159i kop\u00edrov\u00e1n\u00ed do kontejneru se pou\u017e\u00edv\u00e1 koncept «chrootarchive», podle n\u011bho\u017e proces archive.go extrahuje archiv ne do chroot ko\u0159ene kontejneru, ale do chroot rodi\u010dovsk\u00e9ho adres\u00e1\u0159e c\u00edlov\u00e9 cesty, pod kontrolou \u00fato\u010dn\u00edka a nezastavuje p\u0159i tom prov\u00e1d\u011bn\u00ed kontejneru (chroot se pou\u017e\u00edv\u00e1 jako znak pro zneu\u017eit\u00ed z\u00e1vodn\u00edho stavu).<\/p>\n

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

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

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