{"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\/cs\/blog\/news\/terrapin-uyazvimost-v-protokole-ssh-pozvolyayushhaya-snizit-zashhitu-soedineniya","title":{"rendered":"Terrapin \u2014 zranitelnost v protokolu SSH, kter\u00e1 umo\u017e\u0148uje sn\u00ed\u017eit ochranu spojen\u00ed.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Skupina v\u011bdc\u016f z Rursk\u00e9 univerzity v Bochumi (N\u011bmecko) p\u0159edstavila novou techniku MITM \u00fatoku na SSH \u2014 Terrapin, kter\u00e1 vyu\u017e\u00edv\u00e1 zranitelnost (CVE-2023-48795) v protokolu. \u00dato\u010dn\u00edk schopn\u00fd prov\u00e9st MITM \u00fatok m\u00e1 mo\u017enost b\u011bhem sjedn\u00e1v\u00e1n\u00ed spojen\u00ed zablokovat odesl\u00e1n\u00ed zpr\u00e1vy s nastaven\u00edm roz\u0161\u00ed\u0159en\u00ed protokolu za \u00fa\u010delem sn\u00ed\u017een\u00ed \u00farovn\u011b ochrany spojen\u00ed. Prototyp n\u00e1stroje pro proveden\u00ed \u00fatoku byl zve\u0159ejn\u011bn na GitHubu. <\/p>\n

V kontextu OpenSSH zranitelnost nap\u0159\u00edklad umo\u017e\u0148uje p\u0159epnout spojen\u00ed na pou\u017eit\u00ed m\u00e9n\u011b zabezpe\u010den\u00fdch autentiza\u010dn\u00edch algoritm\u016f a vypnout ochranu proti \u00fatok\u016fm prost\u0159ednictv\u00edm vedlej\u0161\u00edch kan\u00e1l\u016f, kter\u00e9 reprodukuj\u00ed vstup pomoc\u00ed anal\u00fdzy zpo\u017ed\u011bn\u00ed mezi stisknut\u00edm kl\u00e1ves. V Python knihovn\u011b AsyncSSH v kombinaci se zranitelnost\u00ed (CVE-2023-46446) v implementaci vnit\u0159n\u00edho automatick\u00e9ho stroje (internal state machine) \u00fatok Terrapin umo\u017e\u0148uje vet\u0159\u00edt se do SSH sezen\u00ed. <\/p>\n

Zranitelnost zasahuje v\u0161echny implementace SSH, kter\u00e9 podporuj\u00ed ChaCha20-Poly1305 nebo \u0161ifry v m\u00f3du CBC ve spojen\u00ed s m\u00f3dem ETM (Encrypt-then-MAC). Nap\u0159\u00edklad tyto mo\u017enosti jsou v OpenSSH dostupn\u00e9 ji\u017e v\u00edce ne\u017e 10 let. Zranitelnost byla blokov\u00e1na v dne\u0161n\u00edm vyd\u00e1n\u00ed OpenSSH 9.6, stejn\u011b jako v aktualizac\u00edch PuTTY 0.80, libssh 0.10.6\/0.9.8 a AsyncSSH 2.14.2. V Dropbear SSH byla oprava ji\u017e p\u0159id\u00e1na do k\u00f3du, ale nov\u00e9 vyd\u00e1n\u00ed zat\u00edm nebylo sestaveno. <\/p>\n

Zranitelnost je zp\u016fsobena t\u00edm, \u017ee \u00fato\u010dn\u00edk, kter\u00fd kontroluje provoz spojen\u00ed (nap\u0159\u00edklad vlastn\u00edk \u0161kodliv\u00e9ho bezdr\u00e1tov\u00e9ho p\u0159\u00edstupov\u00e9ho bodu), m\u016f\u017ee upravit po\u0159adov\u00e1 \u010d\u00edsla paket\u016f b\u011bhem vyjedn\u00e1v\u00e1n\u00ed spojen\u00ed a dos\u00e1hnout nen\u00e1padn\u00e9ho odstran\u011bn\u00ed libovoln\u00e9ho po\u010dtu servisn\u00edch SSH zpr\u00e1v odeslan\u00fdch klientem nebo serverem<\/a>. Mimo jin\u00e9 m\u016f\u017ee \u00fato\u010dn\u00edk odstranit zpr\u00e1vy SSH_MSG_EXT_INFO, kter\u00e9 se pou\u017e\u00edvaj\u00ed k nastaven\u00ed aplikovan\u00fdch roz\u0161\u00ed\u0159en\u00ed protokolu. Aby druh\u00e1 strana neidentifikovala ztr\u00e1tu paketu kv\u016fli meze\u0159e v po\u0159adov\u00fdch \u010d\u00edslech, \u00fato\u010dn\u00edk pro posun po\u0159adov\u00e9ho \u010d\u00edsla iniciuje odesl\u00e1n\u00ed fale\u0161n\u00e9ho paketu se stejn\u00fdm po\u0159adov\u00fdm \u010d\u00edslem jako u odstran\u011bn\u00e9ho paketu. Fale\u0161n\u00fd paket obsahuje zpr\u00e1vu s flagem SSH_MSG_IGNORE, kter\u00e1 je ignorov\u00e1na p\u0159i zpracov\u00e1n\u00ed.

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

\u00datok nem\u016f\u017ee b\u00fdt proveden p\u0159i pou\u017e\u00edv\u00e1n\u00ed streamov\u00fdch \u0161ifrov\u00e1n\u00ed a CTR, proto\u017ee poru\u0161en\u00ed integrity bude odhaleno na \u00farovni aplikace. Ve skute\u010dnosti jsou ohro\u017eeny pouze \u0161ifry ChaCha20-Poly1305 (chacha20-poly1305@openssh.com), u kter\u00fdch se stav sleduje pouze podle po\u0159adov\u00fdch \u010d\u00edsel zpr\u00e1v, a spojen\u00ed re\u017eimu Encrypt-Then-MAC (*-etm@openssh.com) a \u0161ifry CBC. <\/p>\n

V OpenSSH 9.6 a dal\u0161\u00edch implementac\u00edch bylo pro blokaci \u00fatoku zaveden\u00e9 roz\u0161\u00ed\u0159en\u00ed protokolu \u201estrict KEX\u201c, kter\u00e9 se automaticky aktivuje p\u0159i podpo\u0159e ze strany serveru<\/a> klienta. Toto roz\u0161\u00ed\u0159en\u00ed ukon\u010duje spojen\u00ed p\u0159i p\u0159ijet\u00ed jak\u00fdchkoli neobvykl\u00fdch nebo nadbyte\u010dn\u00fdch zpr\u00e1v (nap\u0159\u00edklad s flagem SSH_MSG_IGNORE nebo SSH2_MSG_DEBUG), p\u0159ijat\u00fdch b\u011bhem vyjedn\u00e1v\u00e1n\u00ed spojen\u00ed, a tak\u00e9 resetuje po\u010d\u00edta\u010d MAC (Message Authentication Code) po dokon\u010den\u00ed ka\u017ed\u00e9 v\u00fdm\u011bny kl\u00ed\u010d\u016f.
\n
Zdroj: 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 \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 — Terrapin, \u044d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0438\u0440\u0443\u044e\u0449\u0443\u044e \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2023-48795) \u0432 \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b\u0435. \u0410\u0442\u0430\u043a\u0443\u044e\u0449\u0438\u0439, \u0441\u043f\u043e\u0441\u043e\u0431\u043d\u044b\u0439 \u043e\u0440\u0433\u0430\u043d\u0438\u0437\u043e\u0432\u0430\u0442\u044c MITM-\u0430\u0442\u0430\u043a\u0443, \u0438\u043c\u0435\u0435\u0442 \u0432\u043e\u0437\u043c\u043e\u0436\u043d\u043e\u0441\u0442\u044c \u0432 \u043f\u0440\u043e\u0446\u0435\u0441\u0441\u0435 \u0441\u043e\u0433\u043b\u0430\u0441\u043e\u0432\u0430\u043d\u0438\u044f \u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u044f \u0431\u043b\u043e\u043a\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u043e\u0442\u043f\u0440\u0430\u0432\u043a\u0443 \u0441\u043e\u043e\u0431\u0449\u0435\u043d\u0438\u044f \u0441 \u043d\u0430\u0441\u0442\u0440\u043e\u0439\u043a\u043e\u0439 \u0440\u0430\u0441\u0448\u0438\u0440\u0435\u043d\u0438\u0439 \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b\u0430 \u0434\u043b\u044f \u0441\u043d\u0438\u0436\u0435\u043d\u0438\u044f \u0443\u0440\u043e\u0432\u043d\u044f \u0437\u0430\u0449\u0438\u0442\u044b \u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u044f. \u041f\u0440\u043e\u0442\u043e\u0442\u0438\u043f \u0438\u043d\u0441\u0442\u0440\u0443\u043c\u0435\u043d\u0442\u0430\u0440\u0438\u044f \u0434\u043b\u044f \u0441\u043e\u0432\u0435\u0440\u0448\u0435\u043d\u0438\u044f \u0430\u0442\u0430\u043a\u0438 \u043e\u043f\u0443\u0431\u043b\u0438\u043a\u043e\u0432\u0430\u043d \u043d\u0430 GitHub. \u0412 \u043a\u043e\u043d\u0442\u0435\u043a\u0441\u0442\u0435 OpenSSH \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c, […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":112309,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-112308","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Terrapin \u2014 zranitelnost v protokolu SSH, kter\u00e1 umo\u017e\u0148uje sn\u00ed\u017eit ochranu spojen\u00ed | ProHoster","description":"Skupina v\u00fdzkumn\u00edk\u016f z R\u00farsk\u00e9 univerzity v Bochumi (N\u011bmecko) p\u0159edstavila novou techniku MITM \u00fatoku na SSH - Terrapin, kter\u00e1 vyu\u017e\u00edv\u00e1 zranitelnost (CVE-2023-48795) v protokolu.","canonical_url":"https:\/\/prohoster.info\/cs\/blog\/news\/terrapin-uyazvimost-v-protokole-ssh-pozvolyayushhaya-snizit-zashhitu-soedineniya","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"cs_CZ","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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