{"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\/cs\/blog\/news\/uyazvimost-v-ld-so-openbsd","title":{"rendered":"Zranitelnost v ld.so OpenBSD","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Dynamick\u00fd na\u010d\u00edta\u010d ld.so<\/a><\/noindex>, sou\u010d\u00e1st OpenBSD, m\u016f\u017ee za ur\u010dit\u00fdch okolnost\u00ed pro SUID\/SGID<\/a><\/noindex>-aplikace nechat prom\u011bnnou prost\u0159ed\u00ed LD_LIBRARY_PATH a t\u00edm umo\u017enit na\u010d\u00edst ciz\u00ed k\u00f3d v kontextu procesu vykon\u00e1van\u00e9ho se zv\u00fd\u0161en\u00fdmi privilegii. Opravy s \u0159e\u0161en\u00edm zranitelnosti jsou k dispozici pro verze 6.5<\/a><\/noindex> a 6.6<\/a><\/noindex>. Bin\u00e1rn\u00ed opravy (syspatch<\/a><\/noindex>) pro platformy amd64, i386 a arm64 ji\u017e byly uvedeny do v\u00fdroby a m\u011bly by b\u00fdt k dispozici ke sta\u017een\u00ed v okam\u017eiku zve\u0159ejn\u011bn\u00ed t\u00e9to zpr\u00e1vy.<\/p>\n

Podstata probl\u00e9mu: b\u011bhem pr\u00e1ce ld.so nejprve z\u00edsk\u00e1 z prost\u0159ed\u00ed hodnotu prom\u011bnn\u00e9 LD_LIBRARY_PATH, pomoc\u00ed funkce _dl_split_path() ji p\u0159evede na pole \u0159et\u011bzc\u016f \u2014 cest k adres\u00e1\u0159\u016fm. Pokud se pozd\u011bji zjist\u00ed, \u017ee aktu\u00e1ln\u00ed proces je spu\u0161t\u011bn jako SUID\/SGID aplikace, vytvo\u0159en\u00e9 pole a samotn\u00e1 prom\u011bnn\u00e1 LD_LIBRARY_PATH se vy\u010dist\u00ed. Pokud b\u011bhem pr\u00e1ce _dl_split_path() naraz\u00ed na nedostatek pam\u011bti (co\u017e je obt\u00ed\u017en\u00e9 kv\u016fli explicitn\u00edmu omezen\u00ed velikosti prom\u011bnn\u00fdch prost\u0159ed\u00ed na 256 kB, ale teoreticky mo\u017en\u00e9), prom\u011bnn\u00e1 _dl_libpath dostane hodnotu NULL a n\u00e1sleduj\u00edc\u00ed kontrola t\u00e9to prom\u011bnn\u00e9 zp\u016fsob\u00ed, \u017ee se vynech\u00e1 vol\u00e1n\u00ed _dl_unsetenv(\u201eLD_LIBRARY_PATH\u201c).<\/p>\n

Zranitelnost byla nalezena odborn\u00edky Qualys<\/a><\/noindex>, stejn\u011b jako n\u011bkolik p\u0159edt\u00edm odhalen\u00fdch<\/a><\/noindex> probl\u00e9m\u016f. V\u00fdzkumn\u00edci bezpe\u010dnosti, kte\u0159\u00ed zranitelnost odhalili, zd\u016fraznili rychlost \u0159e\u0161en\u00ed probl\u00e9mu: oprava byla p\u0159ipravena a aktualizace byla vyd\u00e1na b\u011bhem t\u0159\u00ed hodin po obdr\u017een\u00ed ozn\u00e1men\u00ed projektem OpenBSD.<\/p>\n

Dopl\u0148uj\u00edc\u00ed informace: probl\u00e9mu byl p\u0159i\u0159azen \u010d\u00edslo CVE-2019-19726<\/a><\/noindex>. Na mailing listu oss-security bylo u\u010din\u011bno ofici\u00e1ln\u00ed ozn\u00e1men\u00ed<\/a><\/noindex>, zahrnuj\u00edc\u00ed prototyp exploit, kter\u00fd funguje ve OpenBSD 6.6, 6.5, 6.2 a 6.1 na architektur\u00e1ch
\namd64 a i386 (exploit m\u016f\u017ee b\u00fdt p\u0159izp\u016fsoben i pro jin\u00e9 architektury).
\n Probl\u00e9m je zneu\u017eiteln\u00fd v v\u00fdchoz\u00ed instalaci a umo\u017e\u0148uje neprivilegovan\u00e9mu m\u00edstn\u00edmu u\u017eivateli spustit k\u00f3d s pr\u00e1vy root prost\u0159ednictv\u00edm substituce knihovny p\u0159i spu\u0161t\u011bn\u00ed suid-n\u00e1stroj\u016f chpass nebo passwd. K vytvo\u0159en\u00ed nezbytn\u00fdch podm\u00ednek pro zneu\u017eit\u00ed se pou\u017e\u00edv\u00e1 nastaven\u00ed omezen\u00ed RLIMIT_DATA prost\u0159ednictv\u00edm setrlimit.<\/p>\n

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

Zdroj: 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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