{"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\/da\/blog\/news\/uyazvimost-v-ld-so-openbsd","title":{"rendered":"S\u00e5rbarhed i ld.so OpenBSD","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Dynamisk loader ld.so<\/a><\/noindex>, som er en del af OpenBSD, kan under visse forhold for SUID\/SGID<\/a><\/noindex>-applikationer efterlade milj\u00f8variablen LD_LIBRARY_PATH og dermed tillade indl\u00e6sning af tredjepartskode i konteksten af en proces, der k\u00f8rer med forh\u00f8jede privilegier. Patches, der retter s\u00e5rbarheden, er tilg\u00e6ngelige for versioner 6.5<\/a><\/noindex> og 6.6<\/a><\/noindex>. Bin\u00e6re patches (syspatch<\/a><\/noindex>) for platforme som amd64, i386 og arm64 er allerede sendt i produktion og burde v\u00e6re tilg\u00e6ngelige for download ved offentligg\u00f8relsen af denne nyhed.<\/p>\n

Problemet er, at under arbejdet henter ld.so f\u00f8rst v\u00e6rdien af variablen LD_LIBRARY_PATH fra milj\u00f8et, hvorefter den bruger funktionen _dl_split_path() til at omdanne den til et array af strenge \u2014 stier til kataloger. Hvis det senere viser sig, at den nuv\u00e6rende proces er startet af et SUID\/SGID-program, vil det dannede array og selve variablen LD_LIBRARY_PATH blive renset. Hvis _dl_split_path() under arbejdet st\u00f8der p\u00e5 utilstr\u00e6kkelig hukommelse (hvilket er sj\u00e6ldent p\u00e5 grund af den eksplicitte gr\u00e6nse for st\u00f8rrelsen af milj\u00f8variablerne p\u00e5 256 kByte, men teoretisk muligt), vil variablen _dl_libpath f\u00e5 v\u00e6rdien NULL, og den efterf\u00f8lgende kontrol af v\u00e6rdien af denne variabel vil f\u00e5 os til at springe opkaldet af _dl_unsetenv(\u00abLD_LIBRARY_PATH\u00bb) over.<\/p>\n

S\u00e5rbarheden blev opdaget af specialister fra Qualys<\/a><\/noindex>, ligesom flere tidligere kendte problemer. De sikkerhedsunders\u00f8gere, der identificerede s\u00e5rbarheden, bem\u00e6rkede hurtigheden i l\u00f8sningen: patchen blev forberedt, og opdateringer blev udgivet inden for tre timer efter at have modtaget underretning fra OpenBSD-projektet.<\/a><\/noindex> Supplement: Problemet er blevet tildelt nummeret<\/p>\n

CVE-2019-19726 . Der er lavet en<\/a><\/noindex>officiel meddelelse p\u00e5 mailinglisten oss-security, som inkluderer en prototype af en exploit, der fungerer i OpenBSD 6.6, 6.5, 6.2 og 6.1 p\u00e5 arkitekturerne<\/a><\/noindex>amd64 og i386 (exploiten kan tilpasses andre arkitekturer).
\nProblemet er udnytteligt i standardinstallationen og tillader en ikke-privilegeret lokal bruger at k\u00f8re kode som root ved at substituere et bibliotek ved opstart af suid-v\u00e6rkt\u00f8jerne chpass eller passwd. For at skabe de n\u00f8dvendige betingelser for udnyttelse af hukommelsesmangel anvendes gr\u00e6nsen RLIMIT_DATA gennem setrlimit.
\n Hvordan man vurderer niveauet af engelskkundskaber<\/p>\n

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

Kilde: 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 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