{"id":53889,"date":"2019-12-12T00:00:00","date_gmt":"2019-12-11T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/uyazvimost-v-ld-so-openbsd"},"modified":"2020-02-18T14:01:50","modified_gmt":"2020-02-18T11:01:50","slug":"uyazvimost-v-ld-so-openbsd","status":"publish","type":"post","link":"https:\/\/prohoster.info\/pl\/blog\/news\/uyazvimost-v-ld-so-openbsd","title":{"rendered":"Podatno\u015b\u0107 w ld.so OpenBSD","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Dynamiczny loader ld.so<\/a><\/noindex>, kt\u00f3ry jest cz\u0119\u015bci\u0105 OpenBSD, w okre\u015blonych warunkach mo\u017ce SUID\/SGID<\/a><\/noindex>-aplikacji pozostawi\u0107 zmienn\u0105 \u015brodowiskow\u0105 LD_LIBRARY_PATH, co z kolei pozwala na za\u0142adowanie zewn\u0119trznego kodu w kontek\u015bcie procesu dzia\u0142aj\u0105cego z podwy\u017cszonymi uprawnieniami. \u0141atki naprawiaj\u0105ce t\u0119 luk\u0119 s\u0105 dost\u0119pne dla wyda\u0144 6.5<\/a><\/noindex> i 6.6<\/a><\/noindex>. \u0141atki binarne (syspatch<\/a><\/noindex>) dla platform amd64, i386 i arm64 ju\u017c zosta\u0142y wprowadzone do produkcji i powinny by\u0107 dost\u0119pne do pobrania w momencie publikacji tej wiadomo\u015bci.<\/p>\n

Istota problemu: podczas pracy ld.so najpierw wydobywa z otoczenia warto\u015b\u0107 zmiennej LD_LIBRARY_PATH, a nast\u0119pnie za pomoc\u0105 funkcji _dl_split_path() przekszta\u0142ca j\u0105 w tablic\u0119 \u0142a\u0144cuch\u00f3w \u2014 \u015bcie\u017cek do katalog\u00f3w. Je\u015bli p\u00f3\u017aniej oka\u017ce si\u0119, \u017ce bie\u017c\u0105cy proces zosta\u0142 uruchomiony jako aplikacja SUID\/SGID, to utworzona tablica oraz sama zmienna LD_LIBRARY_PATH zostan\u0105 wyczyszczone. W tym przypadku, je\u015bli podczas dzia\u0142ania _dl_split_path() napotka brak pami\u0119ci (co jest ma\u0142o prawdopodobne z powodu wyra\u017anego ograniczenia rozmiaru zmiennych \u015brodowiskowych do 256 KB, ale teoretycznie mo\u017cliwe), zmienna _dl_libpath otrzyma warto\u015b\u0107 NULL, a kolejna kontrola tej zmiennej spowoduje pomini\u0119cie wywo\u0142ania _dl_unsetenv(\"LD_LIBRARY_PATH\").<\/p>\n

Luka zosta\u0142a odkryta przez specjalist\u00f3w Qualys<\/a><\/noindex>, tak jak i kilka wcze\u015bniej ujawnionych<\/a><\/noindex> problem\u00f3w. Przeprowadzaj\u0105cy badanie specjali\u015bci ds. bezpiecze\u0144stwa zauwa\u017cyli szybko\u015b\u0107 rozwi\u0105zania problemu: \u0142atka zosta\u0142a przygotowana, a aktualizacje wydane w ci\u0105gu trzech godzin po powiadomieniu projektu OpenBSD.<\/p>\n

Uzupe\u0142nienie: Problemowi nadano numer CVE-2019-19726<\/a><\/noindex>. Na li\u015bcie dyskusyjnej oss-security og\u0142oszono oficjalny komunikat<\/a><\/noindex>, zawieraj\u0105cy prototyp exploita, dzia\u0142aj\u0105cego w OpenBSD 6.6, 6.5, 6.2 i 6.1 na architekturach
\namd64 i i386 (exploit mo\u017ce by\u0107 zaadaptowany r\u00f3wnie\u017c dla innych architektur).
\n Problem jest u\u017cyteczny w domy\u015blnej instalacji i pozwala nieuprzywilejowanemu lokalnemu u\u017cytkownikowi na uruchomienie kodu z prawami roota poprzez podstawienie biblioteki przy uruchamianiu narz\u0119dzi suid chpass lub passwd. Aby stworzy\u0107 warunki niezb\u0119dne do wykorzystania, u\u017cywa si\u0119 ograniczenia pami\u0119ci RLIMIT_DATA przez setrlimit.<\/p>\n

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

\u0179r\u00f3d\u0142o: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0414\u0438\u043d\u0430\u043c\u0438\u0447\u0435\u0441\u043a\u0438\u0439 \u0437\u0430\u0433\u0440\u0443\u0437\u0447\u0438\u043a ld.so, \u0432\u0445\u043e\u0434\u044f\u0449\u0438\u0439 \u0432 \u0441\u043e\u0441\u0442\u0430\u0432 OpenBSD, \u043f\u0440\u0438 \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0451\u043d\u043d\u044b\u0445 \u0443\u0441\u043b\u043e\u0432\u0438\u044f\u0445 \u043c\u043e\u0436\u0435\u0442 \u0434\u043b\u044f SUID\/SGID-\u043f\u0440\u0438\u043b\u043e\u0436\u0435\u043d\u0438\u044f \u043e\u0441\u0442\u0430\u0432\u0438\u0442\u044c \u043f\u0435\u0440\u0435\u043c\u0435\u043d\u043d\u0443\u044e \u043e\u043a\u0440\u0443\u0436\u0435\u043d\u0438\u044f LD_LIBRARY_PATH \u0438 \u0442\u0430\u043a\u0438\u043c \u043e\u0431\u0440\u0430\u0437\u043e\u043c \u043f\u043e\u0437\u0432\u043e\u043b\u0438\u0442\u044c \u0437\u0430\u0433\u0440\u0443\u0437\u0438\u0442\u044c \u0441\u0442\u043e\u0440\u043e\u043d\u043d\u0438\u0439 \u043a\u043e\u0434 \u0432 \u043a\u043e\u043d\u0442\u0435\u043a\u0441\u0442\u0435 \u043f\u0440\u043e\u0446\u0435\u0441\u0441\u0430, \u0432\u044b\u043f\u043e\u043b\u043d\u044f\u0435\u043c\u043e\u0433\u043e \u0441 \u043f\u043e\u0432\u044b\u0448\u0435\u043d\u043d\u044b\u043c\u0438 \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u044f\u043c\u0438. \u041f\u0430\u0442\u0447\u0438 \u0441 \u0438\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0438\u0435\u043c \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u0434\u043e\u0441\u0442\u0443\u043f\u043d\u044b \u0434\u043b\u044f \u0440\u0435\u043b\u0438\u0437\u043e\u0432 6.5 \u0438 6.6. \u0411\u0438\u043d\u0430\u0440\u043d\u044b\u0435 \u043f\u0430\u0442\u0447\u0438 (syspatch) \u0434\u043b\u044f \u043f\u043b\u0430\u0442\u0444\u043e\u0440\u043c amd64, i386 \u0438 arm64 \u0443\u0436\u0435 \u0437\u0430\u043f\u0443\u0449\u0435\u043d\u044b \u0432 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0441\u0442\u0432\u043e \u0438 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