{"id":112308,"date":"2023-12-19T03:10:22","date_gmt":"2023-12-19T01:10:22","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/terrapin-uyazvimost-v-protokole-ssh-pozvolyayushhaya-snizit-zashhitu-soedineniya"},"modified":"2023-12-19T03:10:22","modified_gmt":"2023-12-19T01:10:22","slug":"terrapin-uyazvimost-v-protokole-ssh-pozvolyayushhaya-snizit-zashhitu-soedineniya","status":"publish","type":"post","link":"https:\/\/prohoster.info\/pt\/blog\/news\/terrapin-uyazvimost-v-protokole-ssh-pozvolyayushhaya-snizit-zashhitu-soedineniya","title":{"rendered":"Terrapin \u2014 vulnerabilidade no protocolo SSH que permite reduzir a seguran\u00e7a da conex\u00e3o","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Um grupo de pesquisadores da Universidade de Ruhr em Bochum (Alemanha) apresentou uma nova t\u00e9cnica de ataque MITM ao SSH \u2014 Terrapin, que explora a vulnerabilidade (CVE-2023-48795) no protocolo. O invasor, que pode organizar um ataque MITM, tem a capacidade de bloquear o envio de mensagens com a configura\u00e7\u00e3o de extens\u00f5es do protocolo durante o processo de negocia\u00e7\u00e3o da conex\u00e3o para reduzir o n\u00edvel de prote\u00e7\u00e3o. Um prot\u00f3tipo da ferramenta para realizar o ataque foi publicado no GitHub. <\/p>\n

No contexto do OpenSSH, a vulnerabilidade, por exemplo, permite reverter a conex\u00e3o para o uso de algoritmos de autentica\u00e7\u00e3o menos seguros e desabilitar a prote\u00e7\u00e3o contra ataques de canal lateral, que recriam a entrada atrav\u00e9s da an\u00e1lise do tempo entre as press\u00f5es de teclas no teclado. Na biblioteca Python AsyncSSH, em combina\u00e7\u00e3o com a vulnerabilidade (CVE-2023-46446) na implementa\u00e7\u00e3o da m\u00e1quina de estado interna, o ataque Terrapin permite se infiltrar na sess\u00e3o SSH. <\/p>\n

A vulnerabilidade afeta todas as implementa\u00e7\u00f5es do SSH que suportam ChaCha20-Poly1305 ou cifras em modo CBC em combina\u00e7\u00e3o com o modo ETM (Encrypt-then-MAC). Por exemplo, tais capacidades est\u00e3o dispon\u00edveis no OpenSSH h\u00e1 mais de 10 anos. A vulnerabilidade foi corrigida na vers\u00e3o atual do OpenSSH 9.6, bem como nas atualiza\u00e7\u00f5es do PuTTY 0.80, libssh 0.10.6\/0.9.8 e AsyncSSH 2.14.2. No Dropbear SSH, a corre\u00e7\u00e3o j\u00e1 foi adicionada ao c\u00f3digo, mas a nova vers\u00e3o ainda n\u00e3o foi lan\u00e7ada. <\/p>\n

A vulnerabilidade \u00e9 causada pelo fato de que um atacante que controla o tr\u00e1fego da conex\u00e3o (por exemplo, o propriet\u00e1rio de um ponto de acesso sem fio malicioso) pode ajustar os n\u00fameros de sequ\u00eancia dos pacotes durante a negocia\u00e7\u00e3o da conex\u00e3o e conseguir a remo\u00e7\u00e3o discreta de um n\u00famero arbitr\u00e1rio de mensagens SSH de controle enviadas pelo cliente ou servidor<\/a>. Entre outras coisas, o atacante pode remover mensagens SSH_MSG_EXT_INFO, que s\u00e3o utilizadas para configurar as extens\u00f5es do protocolo aplic\u00e1veis. Para que a outra parte n\u00e3o detecte a perda do pacote devido a uma quebra nos n\u00fameros de sequ\u00eancia, o atacante inicia o envio de um pacote falso com o mesmo n\u00famero de sequ\u00eancia que o pacote removido. O pacote falso cont\u00e9m uma mensagem com a flag SSH_MSG_IGNORE, que \u00e9 ignorada durante o processamento.

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

Um ataque n\u00e3o pode ser realizado ao usar cifras de fluxo e CTR, pois a viola\u00e7\u00e3o da integridade seria detectada ao n\u00edvel da aplica\u00e7\u00e3o. Na pr\u00e1tica, apenas a cifra ChaCha20-Poly1305 (chacha20-poly1305@openssh.com) \u00e9 suscet\u00edvel ao ataque, onde o estado \u00e9 rastreado apenas pelos n\u00fameros de sequ\u00eancia das mensagens, e a combina\u00e7\u00e3o do modo Encrypt-Then-MAC (*-etm@openssh.com) e cifras CBC. <\/p>\n

No OpenSSH 9.6 e em outras implementa\u00e7\u00f5es, uma extens\u00e3o do protocolo chamada 'strict KEX' foi implementada para bloquear o ataque e \u00e9 ativada automaticamente quando h\u00e1 suporte do lado servidor<\/a> A extens\u00e3o encerra a conex\u00e3o ao receber quaisquer mensagens fora do padr\u00e3o ou excessivas (por exemplo, com a flag SSH_MSG_IGNORE ou SSH2_MSG_DEBUG), recebidas durante a negocia\u00e7\u00e3o da conex\u00e3o, al\u00e9m de reiniciar o contador MAC (C\u00f3digo de Autentica\u00e7\u00e3o de Mensagem) ap\u00f3s a conclus\u00e3o de cada troca de chaves.
\n
Fonte: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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Terrapin, que explora uma vulnerabilidade (CVE-2023-48795) no protocolo.","canonical_url":"https:\/\/prohoster.info\/pt\/blog\/news\/terrapin-uyazvimost-v-protokole-ssh-pozvolyayushhaya-snizit-zashhitu-soedineniya","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"pt_PT","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47Terrapin \u2014 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0432 \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b\u0435 SSH, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u0441\u043d\u0438\u0437\u0438\u0442\u044c \u0437\u0430\u0449\u0438\u0442\u0443 \u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u044f | ProHoster","og:description":"\u0413\u0440\u0443\u043f\u043f\u0430 \u0438\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439 \u0438\u0437 \u0420\u0443\u0440\u0441\u043a\u043e\u0433\u043e \u0443\u043d\u0438\u0432\u0435\u0440\u0441\u0438\u0442\u0435\u0442\u0430 \u0432 \u0411\u043e\u0445\u0443\u043c\u0435 (\u0413\u0435\u0440\u043c\u0430\u043d\u0438\u044f) \u043f\u0440\u0435\u0434\u0441\u0442\u0430\u0432\u0438\u043b\u0430 \u043d\u043e\u0432\u0443\u044e \u0442\u0435\u0445\u043d\u0438\u043a\u0443 MITM-\u0430\u0442\u0430\u043a\u0438 \u043d\u0430 SSH - 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