{"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\/es\/blog\/news\/uyazvimost-v-e2fsck-proyavlyayushhayasya-pri-obrabotke-spetsialno-oformlennyh-katalogov","title":{"rendered":"Vulnerabilidad en e2fsck que se manifiesta al procesar directorios dise\u00f1ados espec\u00edficamente","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

En la utilidad e2fsck, que se ofrece con el paquete para crear sistemas de archivos:<\/a><\/noindex>, se ha detectado<\/a><\/noindex> vulnerabilidad<\/a><\/noindex> (CVE-2019-5188<\/a><\/noindex>), que permite la ejecuci\u00f3n de c\u00f3digo malicioso durante la verificaci\u00f3n del sistema de archivos que contiene directorios especialmente dise\u00f1ados. La vulnerabilidad ha sido confirmada en las versiones de 1.43.3 a 1.45.4. La vulnerabilidad se ha resuelto en la actualizaci\u00f3n e2fsck 1.45.5<\/a><\/noindex>. En las distribuciones, el problema a\u00fan permanece sin soluci\u00f3n (Debian<\/a><\/noindex>, Arch Linux<\/a><\/noindex>, SUSE\/openSUSE<\/a><\/noindex>, Ubuntu<\/a><\/noindex>, RHEL<\/a><\/noindex>).<\/p>\n

La vulnerabilidad es causada por un error en la funci\u00f3n mutate_name() del archivo rehash.c, utilizada para reconstruir las tablas hash relacionadas con el directorio que manejan la coincidencia de todos los archivos en \u00e9l. La corrupci\u00f3n de la estructura hash_entry relacionada con el directorio puede llevar a la escritura de datos del atacante en \u00e1reas fuera del b\u00fafer asignado. Si se detectan en la tabla hash varias vinculaci\u00f3n de archivos con el mismo nombre, la utilidad e2fsck renombra los archivos duplicados a\u00f1adiendo ~0, ~1, etc. Al renombrar temporalmente, se asigna un b\u00fafer de 256 bytes en la pila para almacenar el nuevo nombre. <\/p>\n

El tama\u00f1o de los datos copiados se determina por la expresi\u00f3n «entry->name_len & 0xff», pero el valor de entry->name_len se carga desde la estructura en disco, y no se calcula en funci\u00f3n del tama\u00f1o real del nombre. Si el tama\u00f1o es cero, el \u00edndice de la matriz toma el valor -1 y se crean condiciones para un desbordamiento entero a trav\u00e9s del l\u00edmite inferior del b\u00fafer (integer underflow) y sobrescribe otros datos en la pila con el valor «~0». Para sistemas de 64 bits, la explotaci\u00f3n de la vulnerabilidad se considera poco probable y requiere la ausencia de restricciones sobre el tama\u00f1o de la pila (ulimit -s unlimited). Para sistemas de 32 bits, la explotaci\u00f3n se considera posible, pero el resultado depende en gran medida de c\u00f3mo se compil\u00f3 el archivo ejecutable.<\/p>\n

Para llevar a cabo un ataque, el atacante necesita da\u00f1ar los datos en la partici\u00f3n con FS ext2, ext3 o ext4 de una manera espec\u00edfica. Dado que esta operaci\u00f3n requiere privilegios de superusuario, la vulnerabilidad representa una amenaza durante la verificaci\u00f3n de dispositivos externos o im\u00e1genes de FS obtenidas externamente con la utilidad e2fsck.<\/p>\n

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

Fuente: 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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