{"id":74201,"date":"2020-03-15T08:42:28","date_gmt":"2020-03-15T05:42:28","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/chipy-pamyati-ddr4-ostayutsya-uyazvimy-dlya-atak-rowhammer-nesmotrya-na-dobavlennuyu-zashhitu"},"modified":"2020-03-15T08:42:28","modified_gmt":"2020-03-15T05:42:28","slug":"chipy-pamyati-ddr4-ostayutsya-uyazvimy-dlya-atak-rowhammer-nesmotrya-na-dobavlennuyu-zashhitu","status":"publish","type":"post","link":"https:\/\/prohoster.info\/pt\/blog\/news\/chipy-pamyati-ddr4-ostayutsya-uyazvimy-dlya-atak-rowhammer-nesmotrya-na-dobavlennuyu-zashhitu","title":{"rendered":"Os chips de mem\u00f3ria DDR4 continuam vulner\u00e1veis a ataques RowHammer, apesar da prote\u00e7\u00e3o adicional.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Um grupo de pesquisadores da Universidade Livre de Amsterd\u00e3, da ETH Zurich e da Qualcomm realizaram<\/a><\/noindex> estudou a efic\u00e1cia da prote\u00e7\u00e3o contra ataques de RowHammer<\/a><\/noindex>, que permitem alterar o conte\u00fado de bits individuais da mem\u00f3ria din\u00e2mica (DRAM). Os resultados foram desanimadores e os chips DDR4 dos principais fabricantes ainda permanecem erros cr\u00edticos que bloqueiam o lan\u00e7amento (h\u00e1 10 dias eram 146, um m\u00eas e meio atr\u00e1s eram 316, dois meses atr\u00e1s eram 577, no momento da congelamento no Debian 9 eram 275, no Debian 8 eram 350, no Debian 7 eram 650). O lan\u00e7amento final do Debian 10 \u00e9 esperado para o ver\u00e3o.<\/a><\/noindex> vulner\u00e1veis (CVE-2020-10255<\/a><\/noindex>). <\/p>\n

A vulnerabilidade RowHammer permite distorcer o conte\u00fado de bits individuais na mem\u00f3ria por meio da leitura c\u00edclica de dados de c\u00e9lulas de mem\u00f3ria adjacentes. Como a mem\u00f3ria DRAM \u00e9 um array bidimensional de c\u00e9lulas, cada uma composta por um capacitor e um transistor, a leitura cont\u00ednua de uma mesma \u00e1rea da mem\u00f3ria leva a flutua\u00e7\u00f5es de tens\u00e3o e anomalias que causam uma pequena perda de carga em c\u00e9lulas vizinhas. Se a intensidade da leitura for alta o suficiente, a c\u00e9lula pode perder uma quantidade consider\u00e1vel de carga e o pr\u00f3ximo ciclo de regenera\u00e7\u00e3o pode n\u00e3o restaurar seu estado original, resultando na altera\u00e7\u00e3o dos dados armazenados na c\u00e9lula. <\/p>\n

Para bloquear esse efeito, os chips DDR4 modernos utilizam a tecnologia TRR (Target Row Refresh), projetada para evitar a distor\u00e7\u00e3o das c\u00e9lulas durante um ataque RowHammer. O problema \u00e9 que n\u00e3o existe uma abordagem \u00fanica para a implementa\u00e7\u00e3o do TRR, e cada fabricante de CPU e mem\u00f3ria interpreta o TRR de maneira diferente, aplicando suas pr\u00f3prias variantes de prote\u00e7\u00e3o e n\u00e3o revelando os detalhes da implementa\u00e7\u00e3o.
\nO estudo dos m\u00e9todos de bloqueio do RowHammer utilizados pelos fabricantes permitiu encontrar facilmente maneiras de contornar a prote\u00e7\u00e3o. Durante a verifica\u00e7\u00e3o, ficou evidente que o princ\u00edpio seguido pelos fabricantes «seguran\u00e7a pela obscuridade<\/a><\/noindex> (security by obscurity) na implementa\u00e7\u00e3o do TRR ajuda apenas na prote\u00e7\u00e3o em casos espec\u00edficos, abrangendo ataques t\u00edpicos que manipulam a altera\u00e7\u00e3o da carga de c\u00e9lulas em uma ou duas linhas adjacentes. <\/p>\n

A ferramenta desenvolvida pelos pesquisadores permite verificar a suscetibilidade dos chips a variantes multifacetadas do ataque RowHammer, em que a tentativa de influ\u00eancia na carga \u00e9 feita simultaneamente em v\u00e1rias linhas de c\u00e9lulas de mem\u00f3ria. Esses ataques conseguem contornar a prote\u00e7\u00e3o TRR implementada por alguns fabricantes e levam \u00e0 corrup\u00e7\u00e3o de bits de mem\u00f3ria, mesmo em novos equipamentos com mem\u00f3ria DDR4.
\nDos 42 m\u00f3dulos DIMM estudados, 13 mostraram-se vulner\u00e1veis a variantes n\u00e3o padronizadas do ataque RowHammer, apesar da prote\u00e7\u00e3o declarada. Os m\u00f3dulos problem\u00e1ticos foram fabricados por SK Hynix, Micron e Samsung, cujos produtos cobrem<\/a><\/noindex> 95% do mercado de DRAM.<\/p>\n

Al\u00e9m da DDR4, foram analisados tamb\u00e9m os chips LPDDR4 utilizados em dispositivos m\u00f3veis, que tamb\u00e9m se mostraram sens\u00edveis a variantes avan\u00e7adas do ataque RowHammer. Em particular, a mem\u00f3ria usada em smartphones como Google Pixel, Google Pixel 3, LG G7, OnePlus 7 e Samsung Galaxy S10 foi comprometida.<\/p>\n

Os pesquisadores conseguiram reproduzir em chips DDR4 problem\u00e1ticos v\u00e1rias t\u00e9cnicas de explora\u00e7\u00e3o. Por exemplo, a aplica\u00e7\u00e3o do exploit RowHammer para PTE (Entradas de Tabela de P\u00e1ginas) exigiu, para obter privil\u00e9gios de kernel, a realiza\u00e7\u00e3o do ataque por um per\u00edodo variando de 2,3 segundos a tr\u00eas horas e quinze segundos, dependendo dos chips testados.exploit<\/a><\/noindex> A explora\u00e7\u00e3o por danos na chave p\u00fablica RSA-2048 armazenada na mem\u00f3ria levou de 74,6 segundos a 39 minutos e 28 segundos. Ataque<\/a><\/noindex> O ataque para contornar a verifica\u00e7\u00e3o de privil\u00e9gios atrav\u00e9s da modifica\u00e7\u00e3o da mem\u00f3ria do processo sudo levou 54 minutos e 16 segundos. Ataque<\/a><\/noindex> Para testar os chips de mem\u00f3ria DDR4 utilizados pelos usu\u00e1rios, foi publicada a ferramenta<\/p>\n

TRRespass . Para realizar o ataque com sucesso, \u00e9 necess\u00e1rio ter informa\u00e7\u00f5es sobre o layout f\u00edsico de endere\u00e7os no controlador de mem\u00f3ria, relacionado a bancos e linhas de c\u00e9lulas de mem\u00f3ria. Para determinar esse layout, foi desenvolvida outra ferramenta<\/a><\/noindex>drama , que deve ser executada com privil\u00e9gios de root. Em breve, ser\u00e1 tamb\u00e9m<\/a><\/noindex>publicado um aplicativo para testar a mem\u00f3ria de smartphones. est\u00e3o programados<\/a><\/noindex> publicar um aplicativo para testar a mem\u00f3ria dos smartphones.<\/p>\n

\u00c0 empresa Intel<\/a><\/noindex> e AMD<\/a><\/noindex> Foi recomendado usar mem\u00f3ria com corre\u00e7\u00e3o de erros (ECC), controladores de mem\u00f3ria que suportam Maximum Activate Count (MAC) e aplicar uma frequ\u00eancia de regenera\u00e7\u00e3o elevada para prote\u00e7\u00e3o. No entanto, os pesquisadores acreditam que n\u00e3o h\u00e1 uma solu\u00e7\u00e3o garantida para proteger os chips j\u00e1 lan\u00e7ados contra Rowhammer, e que a aplica\u00e7\u00e3o de ECC e o aumento da frequ\u00eancia de regenera\u00e7\u00e3o da mem\u00f3ria se mostraram ineficazes. Por exemplo, j\u00e1 foi sugerido anteriormente um m\u00e9todo<\/a><\/noindex> de ataque \u00e0 mem\u00f3ria DRAM que contorna a prote\u00e7\u00e3o ECC, al\u00e9m de demonstrar a possibilidade de realizar um ataque \u00e0 DRAM atrav\u00e9s rede local<\/a><\/noindex>, a partir de um sistema host<\/a><\/noindex> e com<\/a><\/noindex> executando JavaScript no navegador.<\/p>\n

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

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

\u0413\u0440\u0443\u043f\u043f\u0430 \u0438\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439 \u0438\u0437 \u0410\u043c\u0441\u0442\u0435\u0440\u0434\u0430\u043c\u0441\u043a\u043e\u0433\u043e \u0441\u0432\u043e\u0431\u043e\u0434\u043d\u043e\u0433\u043e \u0443\u043d\u0438\u0432\u0435\u0440\u0441\u0438\u0442\u0435\u0442\u0430, \u0428\u0432\u0435\u0439\u0446\u0430\u0440\u0441\u043a\u043e\u0439 \u0432\u044b\u0441\u0448\u0435\u0439 \u0442\u0435\u0445\u043d\u0438\u0447\u0435\u0441\u043a\u043e\u0439 \u0448\u043a\u043e\u043b\u044b \u0426\u044e\u0440\u0438\u0445\u0430 \u0438 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0438 Qualcomm \u043f\u0440\u043e\u0432\u0435\u043b\u0438 \u0438\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u043d\u0438\u0435 \u044d\u0444\u0444\u0435\u043a\u0442\u0438\u0432\u043d\u043e\u0441\u0442\u0438 \u043f\u0440\u0438\u043c\u0435\u043d\u044f\u0435\u043c\u043e\u0439 \u0432 \u0441\u043e\u0432\u0440\u0435\u043c\u0435\u043d\u043d\u044b\u0445 \u0447\u0438\u043f\u0430\u0445 \u043f\u0430\u043c\u044f\u0442\u0438 DDR4 \u0437\u0430\u0449\u0438\u0442\u044b \u043e\u0442 \u0430\u0442\u0430\u043a \u043a\u043b\u0430\u0441\u0441\u0430 RowHammer, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0438\u0445 \u0438\u0437\u043c\u0435\u043d\u0438\u0442\u044c \u0441\u043e\u0434\u0435\u0440\u0436\u0438\u043c\u043e\u0435 \u043e\u0442\u0434\u0435\u043b\u044c\u043d\u044b\u0445 \u0431\u0438\u0442\u043e\u0432 \u0434\u0438\u043d\u0430\u043c\u0438\u0447\u0435\u0441\u043a\u043e\u0439 \u043e\u043f\u0435\u0440\u0430\u0442\u0438\u0432\u043d\u043e\u0439 \u043f\u0430\u043c\u044f\u0442\u0438 (DRAM). \u0420\u0435\u0437\u0443\u043b\u044c\u0442\u0430\u0442\u044b \u043e\u043a\u0430\u0437\u0430\u043b\u0438\u0441\u044c \u043d\u0435\u0443\u0442\u0435\u0448\u0438\u0442\u0435\u043b\u044c\u043d\u044b\u043c\u0438 \u0438 \u0447\u0438\u043f\u044b DDR4 \u043e\u0441\u043d\u043e\u0432\u043d\u044b\u0445 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u0435\u0439 \u043f\u043e-\u043f\u0440\u0435\u0436\u043d\u0435\u043c\u0443 \u043e\u0441\u0442\u0430\u044e\u0442\u0441\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u044b (CVE-2020-10255). \u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c RowHammer \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0435\u0442 \u0438\u0441\u043a\u0430\u0437\u0438\u0442\u044c \u0441\u043e\u0434\u0435\u0440\u0436\u0438\u043c\u043e\u0435 \u043e\u0442\u0434\u0435\u043b\u044c\u043d\u044b\u0445 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