{"id":55016,"date":"2020-01-10T00:00:00","date_gmt":"2020-01-09T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/uyazvimost-v-e2fsck-proyavlyayushhayasya-pri-obrabotke-spetsialno-oformlennyh-katalogov"},"modified":"2020-02-18T14:03:05","modified_gmt":"2020-02-18T11:03:05","slug":"uyazvimost-v-e2fsck-proyavlyayushhayasya-pri-obrabotke-spetsialno-oformlennyh-katalogov","status":"publish","type":"post","link":"https:\/\/prohoster.info\/da\/blog\/news\/uyazvimost-v-e2fsck-proyavlyayushhayasya-pri-obrabotke-spetsialno-oformlennyh-katalogov","title":{"rendered":"S\u00e5rbarhed i e2fsck, der viser sig ved behandling af specielt udformede kataloger","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

I v\u00e6rkt\u00f8jet e2fsck, der leveres som en del af pakken e2fsprogs<\/a><\/noindex>, opdaget<\/a><\/noindex> ASLR i programmer med setuid-flaget og bestemme adressefordelingen i de indl\u00e6ste biblioteker gennem manipulation af milj\u00f8variablen LD_PREFER_MAP_32BIT_EXEC.<\/a><\/noindex> (CVE-2019-5188<\/a><\/noindex>), der giver mulighed for at udf\u00f8re ondsindet kode under tjek af filsystemer, der indeholder specielt formaterede kataloger. S\u00e5rbarheden er bekr\u00e6ftet i versioner fra 1.43.3 til 1.45.4. S\u00e5rbarheden er blevet rettet i opdateringen e2fsck 1.45.5<\/a><\/noindex>. I distributionerne forbliver problemet endnu ikke l\u00f8st (Debian<\/a><\/noindex>, Arch Linux<\/a><\/noindex>, SUSE\/openSUSE<\/a><\/noindex>, Ubuntu<\/a><\/noindex>, RHEL<\/a><\/noindex>).<\/p>\n

S\u00e5rbarheden skyldes en fejl i funktionen mutate_name() fra filen rehash.c, der anvendes ved rekonstruktion af hash-tabeller relateret til kataloger, som sikrer matchning med kataloget af alle filer i det. Skade p\u00e5 den relaterede hash_entry-struktur kan f\u00f8re til, at angriberen skriver data uden for den tildelte buffer. I tilf\u00e6lde af at en hash-tabel forbundet med kataloget indeholder flere filer med samme navn, omd\u00f8ber v\u00e6rkt\u00f8jet e2fsck de gentagne filer ved at tilf\u00f8je ~0, ~1 osv. til navnet. For midlertidig opbevaring af det nye navn under en s\u00e5dan omd\u00f8bning tildeles en buffer p\u00e5 256 bytes i stakken. <\/p>\n

St\u00f8rrelsen af de kopierede data bestemmes af udtrykket «entry->name_len & 0xff», men v\u00e6rdien entry->name_len indl\u00e6ses fra strukturen p\u00e5 disken og beregnes ikke ud fra den faktiske st\u00f8rrelse af navnet. Hvis st\u00f8rrelsen er nul, vil indekset i arrayet f\u00e5 v\u00e6rdien -1, hvilket skaber betingelser for heltalsunderl\u00f8b (integer underflow) og overskrivning af andre data i stakken med v\u00e6rdien «~0». For 64-bit systemer vurderes udnyttelse af s\u00e5rbarheden som usandsynlig og kr\u00e6ver, at der ikke er begr\u00e6nsninger p\u00e5 stakens st\u00f8rrelse (ulimit -s unlimited). For 32-bit systemer betragtes udnyttelse som mulig, men resultatet afh\u00e6nger i h\u00f8j grad af, hvordan den eksekverbare fil blev bygget af kompileren.<\/p>\n

For at udf\u00f8re et angreb skal angriberen p\u00e5 en bestemt m\u00e5de beskadige data i partitionen med FS ext2, ext3 eller ext4. Da denne operation kr\u00e6ver superbrugerrettigheder, udg\u00f8r s\u00e5rbarheden en trussel, n\u00e5r e2fsck-v\u00e6rkt\u00f8jet tjekker eksterne lagringsenheder eller modtagne billeder af FS.<\/p>\n

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

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

\u0412 \u0443\u0442\u0438\u043b\u0438\u0442\u0435 e2fsck, \u043f\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u043c\u043e\u0439 \u0432 \u0441\u043e\u0441\u0442\u0430\u0432\u0435 \u043f\u0430\u043a\u0435\u0442\u0430 e2fsprogs, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2019-5188), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u0434\u043e\u0431\u0438\u0442\u044c\u0441\u044f \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f \u043a\u043e\u0434\u0430 \u0437\u043b\u043e\u0443\u043c\u044b\u0448\u043b\u0435\u043d\u043d\u0438\u043a\u0430 \u043f\u0440\u0438 \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u0438 \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 \u0444\u0430\u0439\u043b\u043e\u0432\u043e\u0439 \u0441\u0438\u0441\u0442\u0435\u043c\u044b, \u0441\u043e\u0434\u0435\u0440\u0436\u0430\u0449\u0435\u0439 \u0441\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u044b\u043c \u043e\u0431\u0440\u0430\u0437\u043e\u043c \u043e\u0444\u043e\u0440\u043c\u043b\u0435\u043d\u043d\u044b\u0435 \u043a\u0430\u0442\u0430\u043b\u043e\u0433\u0438. \u041d\u0430\u043b\u0438\u0447\u0438\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u043f\u043e\u0434\u0442\u0432\u0435\u0440\u0436\u0434\u0435\u043d\u043e \u0432 \u0432\u044b\u043f\u0443\u0441\u043a\u0430\u0445 \u0441 1.43.3 \u043f\u043e 1.45.4. \u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0430 \u0432 \u043e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u0438 e2fsck 1.45.5. \u0412 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445 \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u043f\u043e\u043a\u0430 \u043e\u0441\u0442\u0430\u0451\u0442\u0441\u044f \u043d\u0435\u0438\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u043d\u043e\u0439 (Debian, Arch Linux, SUSE\/openSUSE, Ubuntu, RHEL). 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