{"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\/pl\/blog\/news\/uyazvimost-v-ssh-klientah-openssh-i-putty","title":{"rendered":"Vulnerabilno\u015b\u0107 w klientach SSH OpenSSH i PuTTY","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

W klientach SSH OpenSSH i PuTTY wykryto<\/a><\/noindex> luka<\/a><\/noindex> (CVE-2020-14002<\/a><\/noindex> w PuTTY i CVE-2020-14145<\/a><\/noindex> w OpenSSH), co prowadzi do wycieku informacji w algorytmie negocjacji po\u0142\u0105czenia. Ta podatno\u015b\u0107 umo\u017cliwia atakuj\u0105cemu, kt\u00f3ry jest w stanie przechwyci\u0107 ruch klienta (na przyk\u0142ad podczas \u0142\u0105czenia u\u017cytkownika przez kontrolowany przez atakuj\u0105cego punkt dost\u0119pu Wi-Fi), zidentyfikowanie pr\u00f3by pocz\u0105tkowego po\u0142\u0105czenia klienta z hostem, gdy klucz hosta nie zosta\u0142 jeszcze zapisany w pami\u0119ci podr\u0119cznej klienta. <\/p>\n

Wiedz\u0105c, \u017ce klient pr\u00f3buje po\u0142\u0105czy\u0107 si\u0119 po raz pierwszy i \u017ce nie ma jeszcze klucza hosta po swojej stronie, atakuj\u0105cy mo\u017ce przes\u0142a\u0107 po\u0142\u0105czenie przez siebie (MITM) i przedstawi\u0107 klientowi sw\u00f3j klucz hosta, kt\u00f3ry klient SSH uzna za klucz docelowego hosta, je\u015bli nie przeprowadzi weryfikacji odcisku klucza. W ten spos\u00f3b atakuj\u0105cy mo\u017ce zaaran\u017cowa\u0107 MITM, nie wzbudzaj\u0105c podejrze\u0144 u u\u017cytkownika i ignoruj\u0105c sesje, w kt\u00f3rych po stronie klienta znajduj\u0105 si\u0119 ju\u017c zapisane klucze host\u00f3w, pr\u00f3ba oszustwa w tych przypadkach doprowadzi do wy\u015bwietlenia ostrze\u017cenia o zmianie klucza hosta. Atak bazuje na naiwno\u015bci u\u017cytkownik\u00f3w, kt\u00f3rzy nie przeprowadzaj\u0105 r\u0119cznej weryfikacji odcisku klucza hosta przy pierwszym po\u0142\u0105czeniu. Ci, kt\u00f3rzy sprawdzaj\u0105 odciski kluczy, s\u0105 chronieni przed tego rodzaju atakami.<\/p>\n

W ramach oznaczenia s\u0142u\u017c\u0105cego do okre\u015blenia pierwszej pr\u00f3by po\u0142\u0105czenia u\u017cywana jest zmiana kolejno\u015bci wymieniania wspieranych algorytm\u00f3w kluczy hosta. W przypadku gdy nast\u0119puje pierwsze po\u0142\u0105czenie, klient przesy\u0142a domy\u015bln\u0105 list\u0119 algorytm\u00f3w, a je\u017celi klucz hosta jest ju\u017c w pami\u0119ci podr\u0119cznej, to zwi\u0105zany z nim algorytm jest umieszczany na pierwszym miejscu (algorytmy s\u0105 sortowane wed\u0142ug preferencji). <\/p>\n

Problem wyst\u0119puje w wersjach OpenSSH od 5.7 do 8.3 oraz w PuTTY od 0.68 do 0.73. Problem naprawiono<\/a><\/noindex> w wersji PuTTY 0.74<\/a><\/noindex> przez dodanie opcji do wy\u0142\u0105czenia dynamicznego budowania listy algorytm\u00f3w przetwarzania kluczy host\u00f3w na rzecz sta\u0142ej kolejno\u015bci algorytm\u00f3w.<\/p>\n

Projekt OpenSSH nie planuje zmienia\u0107 zachowania klienta SSH, poniewa\u017c je\u015bli nie okre\u015blisz algorytmu istniej\u0105cego klucza na pierwszym miejscu, podejmowana b\u0119dzie pr\u00f3ba zastosowania algorytmu niezgodnego z zapisanym w pami\u0119ci kluczem, co skutkuje ostrze\u017ceniem o nieznanym kluczu. Tzn. pojawia si\u0119 wyb\u00f3r \u2014 albo wyciek informacji (OpenSSH i PuTTY), albo wy\u015bwietlanie ostrze\u017ce\u0144 o zmianie klucza (Dropbear SSH) w przypadku, gdy zapisany klucz nie odpowiada pierwszemu algorytmowi na li\u015bcie domy\u015blnej.<\/p>\n

Aby zapewni\u0107 bezpiecze\u0144stwo w OpenSSH, zaleca si\u0119 u\u017cycie alternatywnych metod weryfikacji klucza hosta za pomoc\u0105 rekord\u00f3w SSHFP w DNSSEC oraz certyfikat\u00f3w hosta (PKI). Mo\u017cna r\u00f3wnie\u017c wy\u0142\u0105czy\u0107 adaptacyjny wyb\u00f3r algorytm\u00f3w kluczy host\u00f3w za pomoc\u0105 opcji HostKeyAlgorithms i skorzysta\u0107 z opcji UpdateHostKeys, aby klient m\u00f3g\u0142 uzyska\u0107 dodatkowe klucze hosta po uwierzytelnieniu.<\/p>\n

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

\u0179r\u00f3d\u0142o: 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\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\udd47Vulnerability in OpenSSH and PuTTY SSH Clients | ProHoster","description":"W klientach SSH OpenSSH i 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