{"id":35011,"date":"2019-10-31T22:01:50","date_gmt":"2019-10-31T19:01:50","guid":{"rendered":"https:\/\/prohoster.info\/blog\/kriticheskaya-uyazvimost-v-exim-pozvolyayushhaya-vypolnit-kod-na-servere-s-pravami-root\/"},"modified":"2019-10-31T22:01:50","modified_gmt":"2019-10-31T19:01:50","slug":"kriticheskaya-uyazvimost-v-exim-pozvolyayushhaya-vypolnit-kod-na-servere-s-pravami-root","status":"publish","type":"post","link":"https:\/\/prohoster.info\/hu\/blog\/news\/kriticheskaya-uyazvimost-v-exim-pozvolyayushhaya-vypolnit-kod-na-servere-s-pravami-root","title":{"rendered":"Kritikus sebezhet\u0151s\u00e9g az Eximban, amely lehet\u0151v\u00e9 teszi k\u00f3d v\u00e9grehajt\u00e1s\u00e1t a szerveren root jogosults\u00e1gokkal","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Az Exim levelez\u0151szerver identified<\/a><\/noindex> critical vulnerability<\/a><\/noindex> (CVE-2019-10149<\/a><\/noindex>), amely t\u00e1voli k\u00f3dv\u00e9grehajt\u00e1shoz vezethet a rendszergazda jogk\u00f6r\u00e9vel a kifejezetten form\u00e1zott k\u00e9r\u00e9s feldolgoz\u00e1sa sor\u00e1n. A probl\u00e9ma kihaszn\u00e1l\u00e1s\u00e1nak lehet\u0151s\u00e9ge a 4.87-t\u0151l 4.91-ig terjed\u0151 verzi\u00f3kban, illetve az EXPERIMENTAL_EVENT opci\u00f3val rendelkez\u0151 \u00f6ssze\u00e1ll\u00edt\u00e1sokban figyelhet\u0151 meg.<\/p>\n

Alap\u00e9rtelmezett konfigur\u00e1ci\u00f3ban a t\u00e1mad\u00e1st a helyi felhaszn\u00e1l\u00f3 egyszer\u0171en v\u00e9grehajthatja, mivel az ACL \u201everify = recipient\u201d alkalmaz\u00e1sra ker\u00fcl, amely tov\u00e1bbi ellen\u0151rz\u00e9seket v\u00e9gez a k\u00fcls\u0151 c\u00edmekre. T\u00e1voli t\u00e1mad\u00e1s v\u00e9grehajt\u00e1s\u00e1ra lehet\u0151s\u00e9g van a be\u00e1ll\u00edt\u00e1sok m\u00f3dos\u00edt\u00e1s\u00e1val, p\u00e9ld\u00e1ul, ha egy m\u00e1sik domain m\u00e1sodlagos MX-jak\u00e9nt m\u0171k\u00f6dik, az ACL \u201everify = recipient\u201d elt\u00e1vol\u00edt\u00e1s\u00e1val, vagy bizonyos v\u00e1ltoztat\u00e1sokkal a local_part_suffix-ben. A t\u00e1voli t\u00e1mad\u00e1s akkor is lehets\u00e9ges, ha a t\u00e1mad\u00f3 k\u00e9pes a kapcsolatot 7 napig nyitva tartani (p\u00e9ld\u00e1ul \u00fagy, hogy percenk\u00e9nt egy b\u00e1jtot k\u00fcld, hogy megker\u00fclje a timeout le\u00e1ll\u00edt\u00e1s\u00e1t). Ugyanakkor nem z\u00e1rhat\u00f3 ki, hogy a probl\u00e9ma t\u00e1voli kihaszn\u00e1l\u00e1s\u00e1nak egyszer\u0171bb t\u00e1mad\u00e1si vektorai is l\u00e9teznek.<\/p>\n

A sebezhet\u0151s\u00e9g a recipient c\u00edm\u00e9nek hib\u00e1s ellen\u0151rz\u00e9s\u00e9b\u0151l ad\u00f3dik a deliver_message() f\u00fcggv\u00e9nyben, amely a \\\/src\\\/deliver.c f\u00e1jlban tal\u00e1lhat\u00f3. A c\u00edm form\u00e1z\u00e1s\u00e1nak manipul\u00e1l\u00e1s\u00e1val a t\u00e1mad\u00f3 el\u00e9rheti, hogy a saj\u00e1t adatai beilleszt\u0151djenek a parancsok argumentumaiba, amelyeket az execv() f\u00fcggv\u00e9ny h\u00edv\u00e1s\u00e1val ind\u00edtanak a rendszergazda jogk\u00f6r\u00e9vel. Az kihaszn\u00e1l\u00e1shoz nincsenek sz\u00fcks\u00e9g olyan \u00f6sszetett technik\u00e1kra, mint a puffert\u00falcsordul\u00e1s vagy a mem\u00f3ria s\u00e9r\u00fcl\u00e9se, elegend\u0151 csup\u00e1n karakterek beilleszt\u00e9se. <\/p>\n

A probl\u00e9ma az c\u00edmek \u00e1talak\u00edt\u00e1s\u00e1hoz haszn\u00e1lt konstrukci\u00f3val f\u00fcgg \u00f6ssze:<\/p>\n

deliver_localpart = expand_string(
\n string_sprintf(\"${local_part:%s}\", new->address));
\n deliver_domain = expand_string(
\n string_sprintf(\"${domain:%s}\", new->address));<\/p>\n

Az expand_string() f\u00fcggv\u00e9ny egy t\u00falbonyol\u00edtott komb\u00e1jn, amely bele\u00e9rtve fel tudja ismerni a '${run{parancs argumentumok}' parancsot, amely k\u00fcls\u0151 feldolgoz\u00f3t ind\u00edt el. \u00cdgy a t\u00e1mad\u00e1shoz a SMTP munkamenet keretein bel\u00fcl a helyi felhaszn\u00e1l\u00f3knak elegend\u0151 \u00e1tadni egy olyan parancsot, mint p\u00e9ld\u00e1ul 'RCPT TO '${username}+${run{\u2026}}@localhost', ahol localhost a local_domains lista egyik hosztja, \u00e9s a username egy l\u00e9tez\u0151 helyi felhaszn\u00e1l\u00f3 neve. <\/p>\n

Ha a szerver mail relayk\u00e9nt m\u0171k\u00f6dik, elegend\u0151 t\u00e1volr\u00f3l elk\u00fcldeni a 'RCPT TO '${run{\u2026}}@relaydomain.com' parancsot, ahol a relaydomain.com egy olyan hoszt, amely a relay_to_domains be\u00e1ll\u00edt\u00e1si szekci\u00f3ban szerepel. Mivel alap\u00e9rtelmezetten az exim nem alkalmazza a jogok vissza\u00e1ll\u00edt\u00e1s\u00e1nak m\u00f3dj\u00e1t (deliver_drop_privilege = false), a '${run{\u2026}}' parancsokon kereszt\u00fcl \u00e1tadott parancsokat root jogokkal fogj\u00e1k v\u00e9grehajtani.<\/p>\n

Figyelemre m\u00e9lt\u00f3, hogy a sebezhet\u0151s\u00e9g eliminates<\/a><\/noindex> a febru\u00e1rban megjelent 4.92-es kiad\u00e1sban tal\u00e1lhat\u00f3, an\u00e9lk\u00fcl, hogy hangs\u00falyozt\u00e1k volna, hogy a jav\u00edt\u00e1s biztons\u00e1gi probl\u00e9m\u00e1khoz vezethet. Nincs alapunk azt felt\u00e9telezni, hogy a Exim fejleszt\u0151i tudatosan eltitkolt\u00e1k a sebezhet\u0151s\u00e9get, mivel a probl\u00e9ma a jav\u00edt\u00e1sok<\/a><\/noindex> hib\u00e1t k\u00f6vet\u0151en mer\u00fclt fel, amely a hib\u00e1s c\u00edmek \u00e1tad\u00e1sakor jelentkezett, \u00e9s a sebezhet\u0151s\u00e9get a Qualys fedezte fel az Exim v\u00e1ltoz\u00e1sainak audit\u00e1l\u00e1sa sor\u00e1n. <\/p>\n

A r\u00e9gebbi verzi\u00f3k jav\u00edt\u00e1sa, amelyek tov\u00e1bbra is el\u00e9rhet\u0151k a disztrib\u00faci\u00f3kban, jelenleg csak patch form\u00e1j\u00e1ban<\/a><\/noindex>form\u00e1j\u00e1ban el\u00e9rhet\u0151. A probl\u00e9ma megold\u00e1s\u00e1ra vonatkoz\u00f3 jav\u00edt\u00f3kiad\u00e1sok a m\u00faltbeli \u00e1gakhoz j\u00fanius 11-\u00e9n vannak tervezve. A csomagfriss\u00edt\u00e9sek el\u0151k\u00e9sz\u00edtve vannak a Debian<\/a><\/noindex>, Ubuntu<\/a><\/noindex>, openSUSE<\/a><\/noindex>. Arch Linux<\/a><\/noindex> \u00e9s Fedora<\/a><\/noindex> szolg\u00e1ltat\u00f3k a 4.92-es verzi\u00f3t biztos\u00edtj\u00e1k, amelyben a probl\u00e9ma nem jelentkezik. A RHEL \u00e9s a CentOS vonatkoz\u00e1s\u00e1ban mivel az Exim nem szerepel a hivatalos csomagrep\u00f3j\u00e1ban (sz\u00fcks\u00e9g eset\u00e9n az<\/a><\/noindex>, mivel az Exim nem r\u00e9sze az alap\u00e9rtelmezett csomag-repozit\u00f3riumuknak.<\/p>\n

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

Forr\u00e1s: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u043f\u043e\u0447\u0442\u043e\u0432\u043e\u043c \u0441\u0435\u0440\u0432\u0435\u0440\u0435 Exim \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u043a\u0440\u0438\u0442\u0438\u0447\u0435\u0441\u043a\u0430\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2019-10149), \u043a\u043e\u0442\u043e\u0440\u0430\u044f \u043c\u043e\u0436\u0435\u0442 \u043f\u0440\u0438\u0432\u0435\u0441\u0442\u0438 \u043a \u0443\u0434\u0430\u043b\u0451\u043d\u043d\u043e\u043c\u0443 \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044e \u043a\u043e\u0434\u0430 \u043d\u0430 \u0441\u0435\u0440\u0432\u0435\u0440\u0435 \u0441 \u043f\u0440\u0430\u0432\u0430\u043c\u0438 root \u043f\u0440\u0438 \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u043a\u0435 \u0441\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u043e \u043e\u0444\u043e\u0440\u043c\u043b\u0435\u043d\u043d\u043e\u0433\u043e \u0437\u0430\u043f\u0440\u043e\u0441\u0430. \u0412\u043e\u0437\u043c\u043e\u0436\u043d\u043e\u0441\u0442\u044c \u044d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0430\u0446\u0438\u0438 \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u043e\u0442\u043c\u0435\u0447\u0435\u043d\u0430 \u0432 \u0432\u0435\u0440\u0441\u0438\u044f\u0445 \u0441 4.87 \u043f\u043e 4.91 \u0432\u043a\u043b\u044e\u0447\u0438\u0442\u0435\u043b\u044c\u043d\u043e \u0438\u043b\u0438 \u043f\u0440\u0438 \u0441\u0431\u043e\u0440\u043a\u0435 \u0441 \u043e\u043f\u0446\u0438\u0435\u0439 EXPERIMENTAL_EVENT. \u0412 \u043a\u043e\u043d\u0444\u0438\u0433\u0443\u0440\u0430\u0446\u0438\u0438 \u043f\u043e \u0443\u043c\u043e\u043b\u0447\u0430\u043d\u0438\u044e \u0430\u0442\u0430\u043a\u0430 \u043c\u043e\u0436\u0435\u0442 \u0431\u044b\u0442\u044c \u0441\u043e\u0432\u0435\u0440\u0448\u0435\u043d\u0430 \u0431\u0435\u0437 \u043b\u0438\u0448\u043d\u0438\u0445 \u0443\u0441\u043b\u043e\u0436\u043d\u0435\u043d\u0438\u0439 \u043b\u043e\u043a\u0430\u043b\u044c\u043d\u044b\u043c \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u043c, […]<\/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-35011","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\udd47Kritikus sebezhet\u0151s\u00e9g az Exim-ban, amely lehet\u0151v\u00e9 teszi a k\u00f3d futtat\u00e1s\u00e1t a szerveren root jogosults\u00e1ggal | ProHoster","description":"A levelez\u0151szerverben, az Exim-ban 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