{"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\/da\/blog\/news\/terrapin-uyazvimost-v-protokole-ssh-pozvolyayushhaya-snizit-zashhitu-soedineniya","title":{"rendered":"Terrapin \u2014 en s\u00e5rbarhed i SSH-protokollen, der muligg\u00f8r en reduktion af beskyttelsen af forbindelsen","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

En gruppe forskere fra Ruhr Universitetet i Bochum (Tyskland) har pr\u00e6senteret en ny MITM-angrebsteknik p\u00e5 SSH \u2014 Terrapin, som udnytter en s\u00e5rbarhed (CVE-2023-48795) i protokollen. En angriber, der kan udf\u00f8re en MITM-angreb, har mulighed for at blokere afsendelsen af meddelelser til indstillingen af protokolets udvidelser under forbindelse etablering for at s\u00e6nke sikkerhedsniveauet for forbindelsen. En prototype af v\u00e6rkt\u00f8jet til at udf\u00f8re angrebet er offentliggjort p\u00e5 GitHub. <\/p>\n

I konteksten af OpenSSH muligg\u00f8r s\u00e5rbarheden for eksempel tilbagevenden til brug af mindre sikre autentifikationsalgoritmer og deaktivering af beskyttelse mod angreb via sidekanaler, der genskaber input ved at analysere forsinkelser mellem tasteangreb p\u00e5 tastaturet. I Python-biblioteket AsyncSSH i kombination med s\u00e5rbarheden (CVE-2023-46446) i implementeringen af den interne tilstandsmaskine tillader angrebet Terrapin indtr\u00e6ngen i et SSH-session. <\/p>\n

S\u00e5rbarheden p\u00e5virker alle SSH-implementeringer, der underst\u00f8tter ChaCha20-Poly1305 eller cipher i CBC-tilstand kombineret med ETM-tilstand (Encrypt-then-MAC). For eksempel har s\u00e5danne muligheder v\u00e6ret tilg\u00e6ngelige i OpenSSH i over 10 \u00e5r. S\u00e5rbarheden er rettet i den nuv\u00e6rende udgave af OpenSSH 9.6 samt i opdateringer af PuTTY 0.80, libssh 0.10.6\/0.9.8 og AsyncSSH 2.14.2. I Dropbear SSH er rettelsen allerede tilf\u00f8jet til koden, men der er endnu ikke udgivet en ny version. <\/p>\n

S\u00e5rbarheden skyldes, at en angriber, der kontrollerer forbindelsestrafikken (for eksempel ejeren af et ondsindet tr\u00e5dl\u00f8st hotspot), kan justere sekvensnumrene p\u00e5 pakkerne under forbindelsebehandlingen og opn\u00e5 usynlig fjernelse af et vilk\u00e5rligt antal service SSH-meddelelser, der sendes af klienten eller serveren<\/a>. Blandt andet kan angriberen fjerne SSH_MSG_EXT_INFO-meddelelserne, der bruges til at konfigurere de anvendte protokoludvidelser. For at forhindre, at den anden part opdager tabet af en pakke som f\u00f8lge af brud i sekvensnumrene, initierer angriberen sending af en falsk pakke med det samme sekvensnummer som den fjernede pakke. Den falske pakke indeholder en meddelelse med flaget SSH_MSG_IGNORE, som ignoreres ved behandling.

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

Angrebet kan ikke udf\u00f8res ved brug af stream cipher og CTR, da en integritetsbrud vil blive afsl\u00f8ret p\u00e5 applikationsniveau. I praksis er kun ChaCha20-Poly1305 cipher (chacha20-poly1305@openssh.com) s\u00e5rbar, hvor tilstanden kun spores via sekvensnumre, og kombinationen af Encrypt-Then-MAC (*-etm@openssh.com) og CBC-cipher. <\/p>\n

I OpenSSH 9.6 og andre implementeringer er der udviklet en protokoludvidelse kaldet \"strict KEX\", som automatisk aktiveres, hvis der er underst\u00f8ttelse fra siden. server<\/a> Udvidelsen afslutter forbindelsen ved modtagelse af nogen us\u00e6dvanlige eller overfl\u00f8dige meddelelser (f.eks. med flaget SSH_MSG_IGNORE eller SSH2_MSG_DEBUG), der modtages under forhandlingen af forbindelsen, samt nulstiller MAC (Message Authentication Code) t\u00e6lleren efter hver n\u00f8gleudveksling.
\n
Kilde: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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Terrapin, der udnytter s\u00e5rbarheden (CVE-2023-48795) i protokollen.","canonical_url":"https:\/\/prohoster.info\/da\/blog\/news\/terrapin-uyazvimost-v-protokole-ssh-pozvolyayushhaya-snizit-zashhitu-soedineniya","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"da_DK","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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