{"id":34721,"date":"2019-10-31T22:00:00","date_gmt":"2019-10-31T19:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/plany-po-usileniyu-mehanizma-zashhity-w-x-v-openbsd\/"},"modified":"2019-10-31T22:00:00","modified_gmt":"2019-10-31T19:00:00","slug":"plany-po-usileniyu-mehanizma-zashhity-w-x-v-openbsd","status":"publish","type":"post","link":"https:\/\/prohoster.info\/it\/blog\/news\/plany-po-usileniyu-mehanizma-zashhity-w-x-v-openbsd","title":{"rendered":"Piani per rafforzare il meccanismo di protezione W^X in OpenBSD","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p>Teo De Raad <noindex><a rel=\"nofollow\" href=\"https:\/\/marc.info\/?l=openbsd-tech&#038;m=155899373514678&#038;w=2\">condiviso<\/a><\/noindex> piani per rafforzare il meccanismo di protezione della memoria W^X (Write XOR Execute). Il senso del meccanismo \u00e8 che le pagine di memoria del processo non possono essere accessibili sia in scrittura che in esecuzione contemporaneamente. In questo modo, il codice pu\u00f2 essere eseguito solo dopo che la scrittura \u00e8 stata vietata, e la scrittura in una pagina di memoria \u00e8 possibile solo dopo che l'esecuzione \u00e8 stata vietata. Il meccanismo W^X aiuta a proteggere le applicazioni nello spazio utente da attacchi tipici, eseguiti attraverso il buffer overflow, inclusi gli overflow dello stack ed \u00e8 attivo in OpenBSD. <noindex><a rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=44506\">predefinito<\/a><\/noindex>.<\/p>\n<p>Sin dall'inizio dei lavori su W^X era chiaro che sarebbe stata una strada lunga, poich\u00e9 esiste un numero significativo di applicazioni che utilizzano JIT. Le implementazioni JIT possono essere suddivise in tre categorie:<\/p>\n<ul>\n<li class=\"l\"> Switching memory between W and X states, accepting the \"cost\" of the system call <noindex><a rel=\"nofollow\" href=\"https:\/\/man.openbsd.org\/mprotect.2\">mprotect<\/a><\/noindex>.\n<li class=\"l\"> Che creano alias tra una coppia di mappature W e X della stessa memoria.\n<li class=\"l\"> The most \"dirty\" option \u2014 requiring W|X memory models that allow simultaneous writing and execution.\n<\/ul>\n<p>Currently, there are significantly fewer programs using the third option and more using the first and second. However, as it was necessary to run programs with W|X JIT (mainly Chromium and Iridum), the wxallowed filesystem mounting option was added, which allowed memory to be used for both writing and execution simultaneously, provided the executable ELF file was marked with the \"wxneeded\" marker, and the applications themselves were additionally protected using mechanisms. <noindex><a rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=43295\">pledge<\/a><\/noindex> e <noindex><a rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=49042\">unveil<\/a><\/noindex> per limitare l'elenco delle chiamate di sistema utilizzate e le parti del file system accessibili per l'applicazione di conseguenza.<\/p>\n<p>Per complicare ulteriormente l'esploiting delle vulnerabilit\u00e0 in tali applicazioni, \u00e8 stata proposta un'aggiunta al meccanismo <noindex><a rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=48243\">MAP_STACK<\/a><\/noindex>, che controlla se la chiamata di sistema viene eseguita da una pagina di memoria accessibile in scrittura. Se la pagina \u00e8 accessibile in scrittura, il processo viene terminato forzatamente. Cos\u00ec, l'attaccante non potr\u00e0 utilizzare le chiamate di sistema e sar\u00e0 costretto a cercare i gadget necessari nell'implementazione JIT o addirittura a svolgere un lavoro pi\u00f9 difficile per scoprire i ganci delle chiamate di sistema direttamente all'interno <noindex><a rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=44320\">di libc accidentalmente collegato.<\/a><\/noindex>. <\/p>\n<p>I processi di Chrome\/Iridium sono gi\u00e0 abbastanza protetti grazie a pledge e unveil, ma impedire l'uso di, ad esempio, una chiamata di sistema write(2) offre chiaramente alcuni vantaggi, poich\u00e9 crea ulteriori difficolt\u00e0 per l'attaccante. Tuttavia, difficolt\u00e0 possono sorgere anche se l'implementazione JIT utilizza chiamate di sistema native da memoria W|X. Tuttavia, ci sono motivi per sperare che non ci si debba confrontare con ci\u00f2, poich\u00e9 l'ABI \u00e8 cambiato pi\u00f9 volte, ma nessuno ha mai segnalato problemi.<\/p>\n<p>Le modifiche sono gi\u00e0 disponibili negli snapshot regolari del ramo OpenBSD-CURRENT, tutti gli interessati sono invitati a testarle.<\/p>\n<p>Una particolare menzione da parte di Theo \u00e8 andata alle notizie correlate sull'introduzione in Chrome\/Iridium della modalit\u00e0 <noindex><a rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=50559\">JITless<\/a><\/noindex>From his perspective, this is acceptable for some use cases, but probably not for all, as this mode clearly increases the load on the processor. Currently, Chrome mainly works if \"wxallowed\" is disabled for \/usr\/local, although problems with some extensions are likely (ghostery is mentioned as an example). Either way, Theo hopes that full operation in JITless mode will be brought to a fully operational state soon.<\/p>\n<p><noindex><a rel=\"nofollow\" name=\"link\"><\/a><\/noindex><\/p>\n<p>Fonte: <a \ncontent=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=50763\">opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u0422\u0435\u043e \u0414\u0435 \u0420\u0430\u0430\u0434\u0442 \u043f\u043e\u0434\u0435\u043b\u0438\u043b\u0441\u044f \u043f\u043b\u0430\u043d\u0430\u043c\u0438 \u043f\u043e \u0443\u0441\u0438\u043b\u0435\u043d\u0438\u044e \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 \u0437\u0430\u0449\u0438\u0442\u044b \u043f\u0430\u043c\u044f\u0442\u0438 W^X (Write XOR Execute). \u0421\u0443\u0442\u044c \u043c\u0435\u0445\u043d\u0438\u0437\u043c\u0430 \u0432 \u0442\u043e\u043c, \u0447\u0442\u043e \u0441\u0442\u0440\u0430\u043d\u0438\u0446\u044b \u043f\u0430\u043c\u044f\u0442\u0438 \u043f\u0440\u043e\u0446\u0435\u0441\u0441\u0430 \u043d\u0435 \u043c\u043e\u0433\u0443\u0442 \u0431\u044b\u0442\u044c \u043e\u0434\u043d\u043e\u0432\u0440\u0435\u043c\u0435\u043d\u043d\u043e \u0434\u043e\u0441\u0442\u0443\u043f\u043d\u044b \u043d\u0430 \u0437\u0430\u043f\u0438\u0441\u044c \u0438 \u0438\u0441\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u0435. \u0422\u0430\u043a\u0438\u043c \u043e\u0431\u0440\u0430\u0437\u043e\u043c, \u043a\u043e\u0434 \u043c\u043e\u0436\u0435\u0442 \u0431\u044b\u0442\u044c \u0438\u0441\u043f\u043e\u043b\u043d\u0435\u043d \u0442\u043e\u043b\u044c\u043a\u043e \u043f\u043e\u0441\u043b\u0435 \u0437\u0430\u043f\u0440\u0435\u0449\u0435\u043d\u0438\u044f \u0437\u0430\u043f\u0438\u0441\u0438, \u0430 \u0437\u0430\u043f\u0438\u0441\u044c \u0432 \u0441\u0442\u0440\u0430\u043d\u0438\u0446\u0443 \u043f\u0430\u043c\u044f\u0442\u0438 \u0432\u043e\u0437\u043c\u043e\u0436\u043d\u0430 \u0442\u043e\u043b\u044c\u043a\u043e \u043f\u043e\u0441\u043b\u0435 \u0437\u0430\u043f\u0440\u0435\u0442\u0430 \u0438\u0441\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f. \u041c\u0435\u0445\u0430\u043d\u0438\u0437\u043c W^X \u043f\u043e\u043c\u043e\u0433\u0430\u0435\u0442 \u0437\u0430\u0449\u0438\u0442\u0438\u0442\u044c [&hellip;]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-34721","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 5.0.1.1 - aioseo.com -->\n\t<meta name=\"description\" content=\"\u0422\u0435\u043e \u0414\u0435 \u0420\u0430\u0430\u0434\u0442 \u043f\u043e\u0434\u0435\u043b\u0438\u043b\u0441\u044f \u043f\u043b\u0430\u043d\u0430\u043c\u0438 \u043f\u043e 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