{"id":99421,"date":"2021-03-13T22:22:39","date_gmt":"2021-03-13T20:22:40","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-podsisteme-iscsi-yadra-linux-pozvolyayushhaya-podnyat-svoi-privilegii"},"modified":"2021-03-13T22:22:39","modified_gmt":"2021-03-13T20:22:40","slug":"uyazvimost-v-podsisteme-iscsi-yadra-linux-pozvolyayushhaya-podnyat-svoi-privilegii","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sk\/blog\/news\/uyazvimost-v-podsisteme-iscsi-yadra-linux-pozvolyayushhaya-podnyat-svoi-privilegii","title":{"rendered":"Zranite\u013enos\u0165 v subsyst\u00e9me iSCSI jadra Linux, ktor\u00e1 umo\u017e\u0148uje zv\u00fd\u0161i\u0165 svoje opr\u00e1vnenia.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V k\u00f3de subsyst\u00e9mu iSCSI v r\u00e1mci jadra Linux bola zisten\u00e1 zranite\u013enos\u0165 (CVE-2021-27365), ktor\u00e1 umo\u017e\u0148uje neopr\u00e1vnen\u00e9mu lok\u00e1lnemu pou\u017e\u00edvate\u013eovi vykon\u00e1va\u0165 k\u00f3d na \u00farovni jadra a z\u00edska\u0165 root-privil\u00e9gi\u00e1 v syst\u00e9me. Pre testovanie je dostupn\u00fd funk\u010dn\u00fd prototyp exploit-u. Zranite\u013enos\u0165 bola odstr\u00e1nen\u00e1 v aktualiz\u00e1ci\u00e1ch jadra Linux 5.11.4, 5.10.21, 5.4.103, 4.19.179, 4.14.224, 4.9.260 a 4.4.260. Aktualiz\u00e1cie bal\u00edkov s jadrom s\u00fa dostupn\u00e9 v distrib\u00faci\u00e1ch Debian, Ubuntu, SUSE\/openSUSE, Arch Linux a Fedora. Pre RHEL opravy zatia\u013e neboli vydan\u00e9. <\/p>\n

Probl\u00e9m je sp\u00f4soben\u00fd chybou vo funkcii iscsi_host_get_param() v module libiscsi, ktor\u00e1 bola zaveden\u00e1 u\u017e v roku 2006 po\u010das v\u00fdvoja subsyst\u00e9mu iSCSI. Vzh\u013eadom na nedostatok riadnych kontrol ve\u013ekosti m\u00f4\u017eu niektor\u00e9 atrib\u00faty re\u0165azca iSCSI, ako hostname alebo username, prekro\u010di\u0165 hodnotu PAGE_SIZE (4 kB). Zranite\u013enos\u0165 m\u00f4\u017ee by\u0165 zneu\u017eit\u00e1 prostredn\u00edctvom zasielania Netlink spr\u00e1v neopr\u00e1vnen\u00fdm pou\u017e\u00edvate\u013eom, ktor\u00e9 nastavuj\u00fa atrib\u00faty iSCSI na hodnoty prekra\u010duj\u00face PAGE_SIZE. Pri \u010d\u00edtan\u00ed \u00fadajov t\u00fdchto atrib\u00fatov cez sysfs alebo seqfs sa sp\u00fa\u0161\u0165a k\u00f3d, ktor\u00fd pren\u00e1\u0161a atrib\u00faty do funkcie sprintf na kop\u00edrovanie do buffer-u, ktor\u00e9ho ve\u013ekos\u0165 je rovn\u00e1 PAGE_SIZE. <\/p>\n

Vyu\u017eitie zranite\u013enosti v distrib\u00faci\u00e1ch z\u00e1vis\u00ed od podpory automatick\u00e9ho na\u010d\u00edtania modulu jadra scsi_transport_iscsi pri pokuse o vytvorenie z\u00e1suvky NETLINK_ISCSI. V distrib\u00faci\u00e1ch, kde sa tento modul automaticky na\u010d\u00edtava, m\u00f4\u017ee by\u0165 \u00fatok vykonan\u00fd nez\u00e1visle od pou\u017e\u00edvania funk\u010dnosti iSCSI. Na \u00faspe\u0161n\u00e9 vykonanie exploit-u je z\u00e1rove\u0148 potrebn\u00e9 zaregistrova\u0165 minim\u00e1lne jeden transport iSCSI. Na registr\u00e1ciu transportu je mo\u017en\u00e9 vyu\u017ei\u0165 modul jadra ib_iser, ktor\u00fd sa automaticky na\u010d\u00edta pri pokuse o vytvorenie z\u00e1suvky NETLINK_RDMA neopr\u00e1vnen\u00fdm pou\u017e\u00edvate\u013eom. <\/p>\n

Automatick\u00e9 na\u010d\u00edtanie potrebn\u00fdch modulov pre vyu\u017eitie exploitov je podporovan\u00e9 v CentOS 8, RHEL 8 a Fedora pri in\u0161tal\u00e1cii bal\u00edka rdma-core, ktor\u00fd je z\u00e1vislos\u0165ou pre niektor\u00e9 popul\u00e1rne bal\u00edky a predvolene sa in\u0161taluje v konfigur\u00e1ci\u00e1ch pre pracovn\u00e9 stanice, serverov\u00e9 syst\u00e9my s GUI a hos\u0165ovsk\u00e9 prostredia virtualiz\u00e1cie. Pri tom sa rdma-core neinstaluje pri pou\u017eit\u00ed serverovej zostavy, ktor\u00e1 funguje iba v konzolovom re\u017eime, a pri in\u0161tal\u00e1cii minim\u00e1lneho in\u0161tala\u010dn\u00e9ho obrazu. Napr\u00edklad bal\u00edk je s\u00fa\u010das\u0165ou z\u00e1kladnej dod\u00e1vky Fedora 31 Workstation, ale nie je zahrnut\u00fd v Fedora 31 Server. Debian a Ubuntu s\u00fa menej n\u00e1chyln\u00e9 na probl\u00e9m, preto\u017ee bal\u00edk rdma-core na\u010d\u00edta potrebn\u00e9 moduly jadra pre \u00fatok iba pri pr\u00edtomnosti RDMA hardv\u00e9ru.

\"Zranite\u013enos\u0165<\/center> <\/p>\n

Ako obch\u00e1dzkov\u00e9 rie\u0161enie ochrany je mo\u017en\u00e9 zak\u00e1za\u0165 automatick\u00e9 na\u010d\u00edtanie modulu libiscsi: echo \"install libiscsi \/bin\/true\" >> \/etc\/modprobe.d\/disable-libiscsi.conf <\/p>\n

Okrem toho boli v subsyst\u00e9me iSCSI odstr\u00e1nen\u00e9 \u010fal\u0161ie dve menej nebezpe\u010dn\u00e9 zranite\u013enosti, ktor\u00e9 m\u00f4\u017eu vies\u0165 k \u00faniku \u00fadajov z jadra: CVE-2021-27363 (\u00fanik \u00fadajov o popise prenosu iSCSI cez sysfs) a CVE-2021-27364 (\u010d\u00edta\u0165 z oblasti mimo hran\u00edc vyrovn\u00e1vacej pam\u00e4te). Uveden\u00e9 zranite\u013enosti m\u00f4\u017eu by\u0165 pou\u017eit\u00e9 na interakciu cez netlink-socket so subsyst\u00e9mom iSCSI bez potrebn\u00fdch privil\u00e9gi\u00ed. Napr\u00edklad neprivilegovan\u00fd pou\u017e\u00edvate\u013e sa m\u00f4\u017ee pripoji\u0165 k iSCSI a odosla\u0165 pr\u00edkaz \"end a session\" na ukon\u010denie rel\u00e1cie.
\n
Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u043a\u043e\u0434\u0435 \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u044b iSCSI \u0438\u0437 \u0441\u043e\u0441\u0442\u0430\u0432\u0430 \u044f\u0434\u0440\u0430 Linux \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2021-27365), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043d\u0435\u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u043e\u043c\u0443 \u043b\u043e\u043a\u0430\u043b\u044c\u043d\u043e\u043c\u0443 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u044e \u0432\u044b\u043f\u043e\u043b\u043d\u0438\u0442\u044c \u043a\u043e\u0434 \u043d\u0430 \u0443\u0440\u043e\u0432\u043d\u0435 \u044f\u0434\u0440\u0430 \u0438 \u043f\u043e\u043b\u0443\u0447\u0438\u0442\u044c root-\u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0438 \u0432 \u0441\u0438\u0441\u0442\u0435\u043c\u0435. \u0414\u043b\u044f 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[…]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":99422,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-99421","post","type-post","status-publish","format-standard","has-post-thumbnail","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\udd47Zranite\u013enos\u0165 v subsyst\u00e9me iSCSI jadra Linux, ktor\u00e1 umo\u017e\u0148uje zv\u00fd\u0161i\u0165 svoje privilegiencie | ProHoster","description":"V k\u00f3de subsyst\u00e9mu iSCSI v r\u00e1mci jadra Linux bola odhalen\u00e1 zranite\u013enos\u0165 (CVE-2021-27365), ktor\u00e1 umo\u017e\u0148uje nepriviligovan\u00e9mu lok\u00e1lnemu u\u017e\u00edvate\u013eovi vykon\u00e1va\u0165 k\u00f3d 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