{"id":117814,"date":"2024-07-18T15:43:01","date_gmt":"2024-07-18T13:43:04","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/ataka-port-shadow-pozvolyayushhaya-perenapravlyat-soedineniya-drugih-polzovatelej-vpn-i-wi-fi"},"modified":"2024-07-18T15:43:01","modified_gmt":"2024-07-18T13:43:04","slug":"ataka-port-shadow-pozvolyayushhaya-perenapravlyat-soedineniya-drugih-polzovatelej-vpn-i-wi-fi","status":"publish","type":"post","link":"https:\/\/prohoster.info\/pt\/blog\/news\/ataka-port-shadow-pozvolyayushhaya-perenapravlyat-soedineniya-drugih-polzovatelej-vpn-i-wi-fi","title":{"rendered":"Ataque Port Shadow, permitindo redirecionar conex\u00f5es de outros usu\u00e1rios de VPN e Wi-Fi","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Um grupo de pesquisadores de universidades canadenses e americanas desenvolveu uma t\u00e9cnica de ataque chamada Port Shadow, que permite, atrav\u00e9s da manipula\u00e7\u00e3o das tabelas de tradu\u00e7\u00e3o de endere\u00e7os no lado do servidor VPN, direcionar a resposta a um pedido para outro usu\u00e1rio conectado ao mesmo servidor VPN. Esse m\u00e9todo pode ser utilizado para interceptar ou redirecionar tr\u00e1fego criptografado, realizar varreduras de portas e desanonimizar usu\u00e1rios de VPN. Um exemplo ilustra como o m\u00e9todo pode ser usado para redirecionar as consultas DNS do usu\u00e1rio, que est\u00e1 operando atrav\u00e9s de um servidor VPN, para um host atacante, ao qual o atacante pode se conectar como cliente. <\/p>\n

Para realizar o ataque, o invasor deve ter a capacidade de se conectar a um VPN<\/a>-servidor com a v\u00edtima, o que \u00e9 poss\u00edvel, por exemplo, ao usar operadores VPN comuns e servi\u00e7os VPN p\u00fablicos que oferecem acesso a todos. A vulnerabilidade afeta servidores VPN que usam tradu\u00e7\u00e3o de endere\u00e7os (NAT) para organizar o acesso dos clientes a recursos externos, dado que para a recep\u00e7\u00e3o do tr\u00e1fego dos clientes e o envio de solicita\u00e7\u00f5es a sites externos, um servidor<\/a> mesmo IP deve ser utilizado. <\/p>\n

O ataque baseia-se na ideia de que, atrav\u00e9s do envio de solicita\u00e7\u00f5es especialmente formatadas, um invasor conectado ao mesmo servidor VPN e utilizando o mesmo NAT pode causar uma distor\u00e7\u00e3o no conte\u00fado das tabelas de tradu\u00e7\u00e3o de endere\u00e7os, o que resultar\u00e1 em pacotes endere\u00e7ados a um usu\u00e1rio sendo enviados para outro usu\u00e1rio. Nas tabelas de tradu\u00e7\u00e3o de endere\u00e7os, a informa\u00e7\u00e3o sobre qual endere\u00e7o IP interno est\u00e1 associado \u00e0 solicita\u00e7\u00e3o enviada \u00e9 determinada com base no n\u00famero da porta de rede de origem utilizada ao enviar a solicita\u00e7\u00e3o. O invasor, ao enviar pacotes SYN e ACK espec\u00edficos e realizar manipula\u00e7\u00f5es simult\u00e2neas do lado da conex\u00e3o do cliente ao servidor VPN e do lado do servidor externo controlado, pode provocar uma colis\u00e3o na tabela NAT e adicionar uma entrada com o mesmo n\u00famero da porta de origem, mas associada ao seu endere\u00e7o local, o que resultar\u00e1 nas respostas a uma solicita\u00e7\u00e3o de outra pessoa sendo devolvidas ao endere\u00e7o do invasor.

\"Ataque<\/center> <\/p>\n

No decorrer da pesquisa, foram testados sistemas de tradu\u00e7\u00e3o de endere\u00e7os Linux e FreeBSD em combina\u00e7\u00e3o com VPNs OpenVPN, OpenConnect e WireGuard. A plataforma FreeBSD demonstrou resist\u00eancia a m\u00e9todos de ataque de redirecionamento de solicita\u00e7\u00f5es realizados por outros usu\u00e1rios conectados \u00e0 mesma VPN. A substitui\u00e7\u00e3o em tabelas NAT s\u00f3 p\u00f4de ser realizada durante o ataque ATIP (Adjacent-to-In-Path), onde o atacante consegue se infiltrar no tr\u00e1fego entre o usu\u00e1rio e o servidor VPN (por exemplo, quando o usu\u00e1rio se conecta a uma rede Wi-Fi controlada pelo atacante) ou entre o servidor VPN e o site alvo. Al\u00e9m disso, o NAT FreeBSD tamb\u00e9m foi afetado por um ataque que permite determinar a conex\u00e3o do usu\u00e1rio a um site espec\u00edfico (Connection Inference). <\/p>\n

Quanto ao Linux, a subsistema Netfilter foi vulner\u00e1vel a ataques de substitui\u00e7\u00e3o de entradas na tabela de tradu\u00e7\u00e3o de endere\u00e7os, permitindo redirecionar pacotes de entrada para outro usu\u00e1rio, for\u00e7ar o envio de pacotes fora do canal VPN criptografado (Decapsulation) ou determinar portas de rede abertas do lado do cliente.

\"Ataque<\/center> <\/p>\n

Como medidas para bloquear o ataque, recomenda-se que provedores de VPN utilizem m\u00e9todos adequados de randomiza\u00e7\u00e3o dos n\u00fameros de portas de origem no NAT, limitando o n\u00famero de conex\u00f5es simult\u00e2neas permitidas ao servidor VPN de um \u00fanico usu\u00e1rio, bem como bloqueando a possibilidade de o cliente escolher a porta de rede que aceita solicita\u00e7\u00f5es do lado do servidor VPN. <\/p>\n

Segundo um representante da empresa Proton AG, o ataque n\u00e3o afeta os servi\u00e7os VPN que utilizam IPs separados para solicita\u00e7\u00f5es de entrada e sa\u00edda. Al\u00e9m disso, h\u00e1 d\u00favidas sobre a possibilidade de aplicar o ataque a servi\u00e7os VPN reais, uma vez que um ataque bem-sucedido foi demonstrado apenas em testes de laborat\u00f3rio e requer o cumprimento de certas condi\u00e7\u00f5es do lado do servidor VPN e do cliente atacado. Al\u00e9m disso, o ataque pode ser \u00fatil apenas para manipular solicita\u00e7\u00f5es n\u00e3o criptografadas, como consultas DNS, enquanto o uso de TLS e HTTPS em n\u00edvel de aplica\u00e7\u00e3o torna o redirecionamento de tr\u00e1fego in\u00fatil. <\/p>\n

As tabelas de tradu\u00e7\u00e3o de endere\u00e7os podem ser manipuladas n\u00e3o apenas em VPNs, mas tamb\u00e9m em redes sem fio, onde o NAT \u00e9 utilizado para conectar usu\u00e1rios a recursos externos em um ponto de acesso. No m\u00eas passado, foram publicados os resultados de uma pesquisa que analisou a possibilidade de realizar um ataque semelhante para interceptar conex\u00f5es TCP de outros usu\u00e1rios em uma rede sem fio. O m\u00e9todo de ataque foi aplic\u00e1vel a 24 das 33 pontos de acesso sem fio testados.

\"Ataque<\/center> <\/p>\n

O ataque proposto para Wi-Fi mostrou-se significativamente mais simples do que o m\u00e9todo mencionado para VPN, pois, devido a otimiza\u00e7\u00f5es, muitos pontos de acesso n\u00e3o verificam a corre\u00e7\u00e3o dos n\u00fameros de sequ\u00eancia nos pacotes TCP. Como resultado, para realizar o ataque, bastou enviar um pacote RST falso para limpar a entrada na tabela de tradu\u00e7\u00e3o de endere\u00e7os e, em seguida, direcionar a resposta para o host do atacante a fim de determinar os n\u00fameros de sequ\u00eancia (SEQ) e de acknowledgment (ACK) necess\u00e1rios para interceptar a conex\u00e3o TCP.

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

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