Az janu\u00e1r v\u00e9g\u00e9n felfedezett s\u00e9r\u00fcl\u00e9kenys\u00e9g ut\u00e1n, amely lehet\u0151v\u00e9 tette a root felhaszn\u00e1l\u00f3hoz val\u00f3 kapcsol\u00f3d\u00e1st jelsz\u00f3 ellen\u0151rz\u00e9s n\u00e9lk\u00fcl, a GNU InetUtils csomag telnetd szerver\u00e9ben t\u00f6bb olyan m\u00f3dszert azonos\u00edtottak, amelyek lehet\u0151v\u00e9 tett\u00e9k a jogosults\u00e1gok emel\u00e9s\u00e9t, ennek k\u00f6vetkezm\u00e9nyek\u00e9nt, hogy sem a 1999-es \u00e9vben (CVE-1999-0073) a s\u00e9r\u00fcl\u00e9kenys\u00e9get nem siker\u00fclt teljesen megsz\u00fcntetni. <\/p>\n
A s\u00e9r\u00fcl\u00e9kenys\u00e9gek a telnetd azon k\u00e9pess\u00e9g\u00e9b\u0151l ad\u00f3dnak, hogy a kliens k\u00f6rnyezeti v\u00e1ltoz\u00f3kat adhat \u00e1t a szervernek az ENVIRON opci\u00f3 seg\u00edts\u00e9g\u00e9vel. Az ilyen k\u00f6rnyezeti v\u00e1ltoz\u00f3k a telnetd folyamat kontextus\u00e1ban ker\u00fclnek be\u00e1ll\u00edt\u00e1sra \u00e9s feldolgoz\u00e1sra, majd \u00e1tker\u00fclnek az \u00e1ltala ind\u00edtott gyermek folyamatokba, bele\u00e9rtve a root jogokkal ind\u00edtott \/bin\/login folyamatot. A CVE-1999-0073 s\u00e9r\u00fcl\u00e9kenys\u00e9g lehet\u0151v\u00e9 tette a telnet kliens sz\u00e1m\u00e1ra, hogy \u00e1tadja az LD_LIBRARY_PATH k\u00f6rnyezeti v\u00e1ltoz\u00f3t, amelynek be\u00e1ll\u00edt\u00e1sa a felhaszn\u00e1l\u00f3 \u00e1ltal megadott megosztott k\u00f6nyvt\u00e1r bet\u00f6lt\u00e9s\u00e9hez vezetett a login folyamat ind\u00edt\u00e1sakor. Ha a rendszer t\u00e1mogatja a f\u00e1jlok bet\u00f6lt\u00e9s\u00e9t telnet protokollon kereszt\u00fcl, a t\u00e1mad\u00f3 k\u00e9pes lett volna speci\u00e1lisan elk\u00e9sz\u00edtett k\u00f6nyvt\u00e1r bet\u00f6lt\u00e9s\u00e9re \u00e9s annak root jogokkal val\u00f3 bet\u00f6lt\u00e9s\u00e9re. <\/p>\n
A GNU InetUtils telnetd-ben egy sebezhet\u0151s\u00e9g l\u00e9pett fel, amelyet a vesz\u00e9lyes k\u00f6rnyezeti v\u00e1ltoz\u00f3k, mint az \u201eLD_\u201d, \u201eLIBPATH\u201d, \u201eENV\u201d, \u201eIFS\u201d \u00e9s \u201e_RLD_\u201d maszkol\u00e1s\u00e1val sz\u00fcntettek meg. Ugyanakkor a \u201eCREDENTIALS_DIRECTORY\u201d k\u00f6rnyezeti v\u00e1ltoz\u00f3 blokkolatlan maradt, amely az \/usr\/bin\/login ind\u00edt\u00e1sakor ker\u00fcl feldolgoz\u00e1sra. Ezzel a k\u00f6rnyezeti v\u00e1ltoz\u00f3val a felhaszn\u00e1l\u00f3 meg tudta v\u00e1ltoztatni a hiteles\u00edt\u0151 adatok be\u00e1ll\u00edt\u00e1sainak k\u00f6nyvt\u00e1r\u00e1t, \u00e9s elhelyezhetett egy login.noauth f\u00e1jlt az \u00faj k\u00f6nyvt\u00e1rban, amelynek \u00e9rt\u00e9ke \u201eyes\u201d, aktiv\u00e1lva a jelsz\u00f3 n\u00e9lk\u00fcli bejelentkez\u00e9st (ez megfelel a login folyamat sz\u00e1m\u00e1ra t\u00f6rt\u00e9n\u0151 \u201e-f\u201d z\u00e1szl\u00f3 \u00e1tad\u00e1s\u00e1nak). A be\u00e1ll\u00edt\u00e1s minden felhaszn\u00e1l\u00f3ra \u00e9rv\u00e9nyes, bele\u00e9rtve a root-ot is. <\/p>\n
A t\u00e1mad\u00e1s l\u00e9nyege, hogy egy nem privilegiz\u00e1lt felhaszn\u00e1l\u00f3 l\u00e9trehozzon egy almapp\u00e1t a saj\u00e1t otthoni k\u00f6nyvt\u00e1r\u00e1ban, felt\u00f6ltse a login.noauth f\u00e1jlt, \u00e9s megpr\u00f3b\u00e1ljon bel\u00e9pni a \u201eCREDENTIALS_DIRECTORY= l\u00e9trehozott k\u00f6nyvt\u00e1r\u201d k\u00f6rnyezeti v\u00e1ltoz\u00f3 be\u00e1ll\u00edt\u00e1s\u00e1val, valamint a \u201eUSER=root\u201d k\u00f6rnyezeti v\u00e1ltoz\u00f3 \u00e1tad\u00e1s\u00e1val (a telnet automatikus kapcsol\u00f3d\u00e1si m\u00f3dj\u00e1ban a felhaszn\u00e1l\u00f3nevet nem a parancssorb\u00f3l veszik, hanem a USER k\u00f6rnyezeti v\u00e1ltoz\u00f3n kereszt\u00fcl adj\u00e1k \u00e1t). \u00cdme egy p\u00e9lda az exploit-ra. <\/p>\n
Ezut\u00e1n egy \u00fajabb m\u00f3dot t\u00e1rtak fel a root-hozz\u00e1f\u00e9r\u00e9s megszerz\u00e9s\u00e9re a telnetd-n kereszt\u00fcl, amely a GNU gettext k\u00f6nyvt\u00e1r \u00e1ltal feldolgozott OUTPUT_CHARSET \u00e9s LANGUAGE k\u00f6rnyezeti v\u00e1ltoz\u00f3k manipul\u00e1ci\u00f3j\u00e1val, valamint a glibc-ben haszn\u00e1lt GCONV_PATH k\u00f6rnyezeti v\u00e1ltoz\u00f3val kapcsolatos. Az OUTPUT_CHARSET \u00e9s LANGUAGE k\u00f6rnyezeti v\u00e1ltoz\u00f3k be\u00e1ll\u00edt\u00e1s\u00e1val a t\u00e1mad\u00f3 aktiv\u00e1lhatja a karakterk\u00f3dol\u00e1s \u00e1talak\u00edt\u00e1si funkci\u00f3t a gettext-ben, amely megh\u00edvja az iconv_open() f\u00fcggv\u00e9nyt. Ezzel p\u00e1rhuzamosan, az iconv_open() f\u00fcggv\u00e9ny v\u00e9grehajt\u00e1sakor a gconv-modules konfigur\u00e1ci\u00f3s f\u00e1jl bet\u00f6lt\u00e9sekor az \u00fatvonal a GCONV_PATH k\u00f6rnyezeti v\u00e1ltoz\u00f3 figyelembev\u00e9tel\u00e9vel sz\u00e1m\u00edt\u00f3dik. A gconv-modules f\u00e1jl behelyettes\u00edt\u00e9s\u00e9vel lehet\u0151s\u00e9g ny\u00edlik arra, hogy a folyamat a bejelentkez\u00e9si id\u0151szak alatt saj\u00e1t megosztott k\u00f6nyvt\u00e1rat t\u00f6lts\u00f6n be a lokaliz\u00e1lt sz\u00f6veg kimenetekor. <\/p>\n
A CVE-azonos\u00edt\u00f3k jelenleg nem vannak hozz\u00e1rendelve a megjel\u00f6lt sebezhet\u0151s\u00e9gekhez. V\u00e9delmi m\u00f3dszerk\u00e9nt a megengedett \u00e9rt\u00e9kek feh\u00e9rlist\u00e1j\u00e1nak haszn\u00e1lat\u00e1t fontolj\u00e1k meg (\u201eTERM\u201d, \u201eDISPLAY\u201d, \u201eUSER\u201d, \u201eLOGNAME\u201d \u00e9s \u201ePOSIXLY_CORRECT\u201d), blokkolva minden egy\u00e9b k\u00f6rnyezeti v\u00e1ltoz\u00f3t, hasonl\u00f3an ahhoz, ahogyan az OpenSSH-ban a k\u00f6rnyezeti v\u00e1ltoz\u00f3kkal dolgoznak. A sebezhet\u0151s\u00e9gek meger\u0151s\u00edt\u00e9st nyertek a GNU InetUtils csomagban, a megval\u00f3s\u00edt\u00e1s a szerver<\/a> A telnetd, amely a Debian, Ubuntu \u00e9s a sz\u00e1rmaz\u00e9kos disztrib\u00faci\u00f3kban \u00e9rkezik, \u00e9rintett a probl\u00e9m\u00e1kban. A GNU InetUtils jav\u00edt\u00e1sai jelenleg nem \u00e9rhet\u0151k el. A Rocky Linux 9 egy m\u00f3dos\u00edtott telnetd-t tartalmaz, amely nem sebezhet\u0151, ebben a vesz\u00e9lyes k\u00f6rnyezeti v\u00e1ltoz\u00f3k sz\u0171r\u00e9se helyett feh\u00e9rlista-alap\u00fa ellen\u0151rz\u00e9st alkalmaznak. A feh\u00e9rlista-sz\u0171r\u00e9s szint\u00e9n megval\u00f3s\u00edt\u00e1sra ker\u00fclt a FreeBSD telnetd-j\u00e9ben. Az OpenBSD telnetd-t 2005-ben elt\u00e1vol\u00edtott\u00e1k a rendszerb\u0151l. \u0421\u043b\u0435\u0434\u043e\u043c \u0437\u0430 \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u043d\u043e\u0439 \u0432 \u043a\u043e\u043d\u0446\u0435 \u044f\u043d\u0432\u0430\u0440\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c\u044e, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0432\u0448\u0435\u0439 \u043f\u043e\u0434\u043a\u043b\u044e\u0447\u0438\u0442\u044c\u0441\u044f \u043f\u043e\u0434 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u043c root \u0431\u0435\u0437 \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 \u043f\u0430\u0440\u043e\u043b\u044f, \u0432 \u0441\u0435\u0440\u0432\u0435\u0440\u0435 telnetd \u0438\u0437 \u043d\u0430\u0431\u043e\u0440\u0430 GNU InetUtils \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u043e \u043d\u0435\u0441\u043a\u043e\u043b\u044c\u043a\u043e \u0441\u043f\u043e\u0441\u043e\u0431\u043e\u0432 \u043f\u043e\u0432\u044b\u0448\u0435\u043d\u0438\u044f \u0441\u0432\u043e\u0438\u0445 \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0439, \u0441\u0442\u0430\u0432\u0448\u0438\u0445 \u0441\u043b\u0435\u0434\u0441\u0442\u0432\u0438\u0435\u043c \u043d\u0435\u043f\u043e\u043b\u043d\u043e\u0433\u043e \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u0432 1999 \u0433\u043e\u0434\u0443 (CVE-1999-0073). \u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u0432\u044b\u0437\u0432\u0430\u043d\u044b \u043d\u0430\u043b\u0438\u0447\u0438\u0435\u043c \u0432 telnetd \u0432\u043e\u0437\u043c\u043e\u0436\u043d\u043e\u0441\u0442\u0438 \u043f\u0435\u0440\u0435\u0434\u0430\u0447\u0438 \u043a\u043b\u0438\u0435\u043d\u0442\u043e\u043c \u043f\u0435\u0440\u0435\u043c\u0435\u043d\u043d\u044b\u0445 \u043e\u043a\u0440\u0443\u0436\u0435\u043d\u0438\u044f \u043d\u0430 \u0441\u0435\u0440\u0432\u0435\u0440 \u043f\u0440\u0438 \u043f\u043e\u043c\u043e\u0449\u0438 \u043e\u043f\u0446\u0438\u0438 ENVIRON. \u041f\u043e\u0434\u043e\u0431\u043d\u044b\u0435 \u043f\u0435\u0440\u0435\u043c\u0435\u043d\u043d\u044b\u0435 […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":8,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-162791","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\udd47\u00daj s\u00e9r\u00fcl\u00e9kenys\u00e9gek sorozata a telnetd-ben, amelyek lehet\u0151v\u00e9 teszik a root-jogosults\u00e1gok megszerz\u00e9s\u00e9t a rendszeren | ProHoster","description":"A janu\u00e1r v\u00e9g\u00e9n felfedezett 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Forr\u00e1s: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"