{"id":87197,"date":"2020-07-05T07:42:02","date_gmt":"2020-07-05T05:42:02","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-ssh-klientah-openssh-i-putty"},"modified":"2020-07-05T07:42:02","modified_gmt":"2020-07-05T05:42:02","slug":"uyazvimost-v-ssh-klientah-openssh-i-putty","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/uyazvimost-v-ssh-klientah-openssh-i-putty","title":{"rendered":"Zranitelnost v SSH klientech OpenSSH a PuTTY","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V SSH klientech OpenSSH a PuTTY byla odhalena<\/a><\/noindex> zranitelnost<\/a><\/noindex> (CVE-2020-14002<\/a><\/noindex> v PuTTY a CVE-2020-14145<\/a><\/noindex> v OpenSSH), co\u017e vede k \u00faniku informac\u00ed p\u0159i vyjedn\u00e1v\u00e1n\u00ed spojen\u00ed. Zranitelnost umo\u017e\u0148uje \u00fato\u010dn\u00edkovi, kter\u00fd dok\u00e1\u017ee odchyt\u00e1vat provoz klienta (nap\u0159\u00edklad p\u0159i p\u0159ipojen\u00ed u\u017eivatele p\u0159es \u00fato\u010dn\u00edkem ovl\u00e1dan\u00fd bezdr\u00e1tov\u00fd hotspot), zjistit pokus o prvotn\u00ed p\u0159ipojen\u00ed klienta k hostiteli, kdy\u017e klient je\u0161t\u011b nem\u00e1 v cache kl\u00ed\u010d hostitele. <\/p>\n

Pokud \u00fato\u010dn\u00edk v\u00ed, \u017ee se klient sna\u017e\u00ed p\u0159ipojit poprv\u00e9 a je\u0161t\u011b nem\u00e1 kl\u00ed\u010d hostitele na sv\u00e9 stran\u011b, m\u016f\u017ee v\u00e9st p\u0159ipojen\u00ed p\u0159es sebe (MITM) a p\u0159edlo\u017eit klientovi sv\u016fj hostitelsk\u00fd kl\u00ed\u010d, kter\u00fd SSH klient pova\u017euje za kl\u00ed\u010d c\u00edlov\u00e9ho hostitele, pokud nedojde k ov\u011b\u0159en\u00ed otisku kl\u00ed\u010de. T\u00edmto zp\u016fsobem m\u016f\u017ee \u00fato\u010dn\u00edk uspo\u0159\u00e1dat MITM, ani\u017e by vyvolal podez\u0159en\u00ed u u\u017eivatele, a ignorovat sezen\u00ed, u nich\u017e m\u00e1 klient ji\u017e ulo\u017een\u00e9 kl\u00ed\u010de hostitel\u016f, jejich\u017e pokus o n\u00e1hradu by vedl k v\u00fdstraze o zm\u011bn\u011b hostitelsk\u00e9ho kl\u00ed\u010de. \u00datok se spol\u00e9h\u00e1 na nedbalost u\u017eivatel\u016f, kte\u0159\u00ed manu\u00e1ln\u011b nekontroluj\u00ed otisk kl\u00ed\u010de hostitele p\u0159i prvn\u00edm p\u0159ipojen\u00ed. Ti, kte\u0159\u00ed otisky kl\u00ed\u010de kontroluj\u00ed, jsou od t\u011bchto \u00fatok\u016f chr\u00e1n\u011bni.<\/p>\n

Jako znak pro ur\u010den\u00ed prvn\u00edho pokusu o p\u0159ipojen\u00ed se pou\u017e\u00edv\u00e1 zm\u011bna po\u0159ad\u00ed v\u00fd\u010dtu podporovan\u00fdch algoritm\u016f hostitelsk\u00fdch kl\u00ed\u010d\u016f. V p\u0159\u00edpad\u011b, \u017ee dojde k prvotn\u00edmu p\u0159ipojen\u00ed, klient p\u0159ed\u00e1v\u00e1 seznam algoritm\u016f podle defaultn\u00edch hodnot, a pokud u\u017e kl\u00ed\u010d hostitele je v cache, je s n\u00edm spojen\u00fd algoritmus um\u00edst\u011bn na prvn\u00ed m\u00edsto (algoritmy jsou \u0159azeny podle preference). <\/p>\n

Probl\u00e9m se projevuje ve verz\u00edch OpenSSH od 5.7 do 8.3 a v PuTTY od 0.68 do 0.73. Probl\u00e9m odstran\u011bna<\/a><\/noindex> v vyd\u00e1n\u00ed PuTTY 0.74<\/a><\/noindex> p\u0159id\u00e1n\u00edm mo\u017enosti pro vypnut\u00ed dynamick\u00e9ho sestavov\u00e1n\u00ed seznamu algoritm\u016f zpracov\u00e1n\u00ed hostitelsk\u00fdch kl\u00ed\u010d\u016f ve prosp\u011bch v\u00fd\u010dtu algoritm\u016f v pevn\u00e9m po\u0159ad\u00ed.<\/p>\n

Projekt OpenSSH nepl\u00e1nuje m\u011bnit chov\u00e1n\u00ed SSH klienta, proto\u017ee pokud nen\u00ed algoritmus existuj\u00edc\u00edho kl\u00ed\u010de uveden na prvn\u00edm m\u00edst\u011b, pokus\u00ed se aplikovat neodpov\u00eddaj\u00edc\u00ed algoritmus na mezipam\u011btovan\u00fd kl\u00ed\u010d s v\u00fdstupem varov\u00e1n\u00ed o nezn\u00e1m\u00e9m kl\u00ed\u010di. Tedy vznik\u00e1 volba \u2014 bu\u010f \u00fanik informac\u00ed (OpenSSH a PuTTY), nebo v\u00fdstup varov\u00e1n\u00ed o zm\u011bn\u011b kl\u00ed\u010de (Dropbear SSH), pokud ulo\u017een\u00fd kl\u00ed\u010d neodpov\u00edd\u00e1 prvn\u00edmu algoritmu v seznamu podle v\u00fdchoz\u00edho nastaven\u00ed.<\/p>\n

Pro zaji\u0161t\u011bn\u00ed ochrany v OpenSSH se doporu\u010duje pou\u017e\u00edt alternativn\u00ed metody ov\u011b\u0159ov\u00e1n\u00ed hostitelsk\u00e9ho kl\u00ed\u010de pomoc\u00ed z\u00e1znam\u016f SSHFP v DNSSEC a certifik\u00e1t\u016f hostitele (PKI). Tak\u00e9 je mo\u017en\u00e9 vypnout adaptivn\u00ed v\u00fdb\u011br algoritm\u016f hostitelsk\u00fdch kl\u00ed\u010d\u016f pomoc\u00ed volby HostKeyAlgorithms a pou\u017e\u00edt volbu UpdateHostKeys pro z\u00edsk\u00e1n\u00ed dal\u0161\u00edch hostitelsk\u00fdch kl\u00ed\u010d\u016f klientem po ov\u011b\u0159ov\u00e1n\u00ed.<\/p>\n

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

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

\u0412 SSH-\u043a\u043b\u0438\u0435\u043d\u0442\u0430\u0445 OpenSSH \u0438 PuTTY \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2020-14002 \u0432 PuTTY \u0438 CVE-2020-14145 \u0432 OpenSSH), \u043f\u0440\u0438\u0432\u043e\u0434\u044f\u0449\u0430\u044f \u043a \u0443\u0442\u0435\u0447\u043a\u0435 \u0441\u0432\u0435\u0434\u0435\u043d\u0438\u0439 \u0432 \u0430\u043b\u0433\u043e\u0440\u0438\u0442\u043c\u0435 \u0441\u043e\u0433\u043b\u0430\u0441\u043e\u0432\u0430\u043d\u0438\u044f \u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u044f. \u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0435\u0442 \u0430\u0442\u0430\u043a\u0443\u044e\u0449\u0435\u043c\u0443, \u0441\u043f\u043e\u0441\u043e\u0431\u043d\u043e\u043c\u0443 \u043f\u0435\u0440\u0435\u0445\u0432\u0430\u0442\u0438\u0442\u044c \u0442\u0440\u0430\u0444\u0438\u043a \u043a\u043b\u0438\u0435\u043d\u0442\u0430 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\u043f\u0440\u043e\u043a\u044d\u0448\u0438\u0440\u043e\u0432\u0430\u043d \u043a\u043b\u044e\u0447 \u0445\u043e\u0441\u0442\u0430. \u0417\u043d\u0430\u044f, \u0447\u0442\u043e […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-87197","post","type-post","status-publish","format-standard","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\udd47Zranitelnost v SSH klientech OpenSSH a PuTTY | ProHoster","description":"V SSH klientech OpenSSH a 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