V knihovn\u011b libssh (nem\u00fdlit s libssh2), kter\u00e1 je ur\u010dena pro p\u0159id\u00e1n\u00ed klientsk\u00e9 a serverov\u00e9 podpory protokolu SSHv2 do program\u016f napsan\u00fdch v jazyce C, byla odhalena zranitelnost (CVE-2021-3634), kter\u00e1 m\u016f\u017ee v\u00e9st k p\u0159ete\u010den\u00ed bufferu p\u0159i iniciaci procesu zm\u011bny kl\u00ed\u010de (rekey) s pou\u017eit\u00edm mechanismu v\u00fdm\u011bny kl\u00ed\u010d\u016f, kter\u00fd pou\u017e\u00edv\u00e1 jin\u00fd hashovac\u00ed algoritmus. Probl\u00e9m byl opraven ve verzi 0.9.6. <\/p>\n
Podstatou probl\u00e9mu je, \u017ee operace v\u00fdm\u011bny kl\u00ed\u010de umo\u017e\u0148uje pou\u017eit\u00ed kryptografick\u00fdch hash\u016f s velikost\u00ed otisku, kter\u00e1 se li\u0161\u00ed od p\u016fvodn\u011b pou\u017eit\u00e9ho algoritmu. P\u0159itom pam\u011b\u0165 pro hash v libssh byla alokov\u00e1na na z\u00e1klad\u011b p\u016fvodn\u00ed velikosti hash a pou\u017eit\u00ed hash s v\u011bt\u0161\u00ed velikost\u00ed vede k p\u0159eps\u00e1n\u00ed dat za hranic\u00ed p\u0159id\u011blen\u00e9ho bufferu. Jako z\u00e1lo\u017en\u00ed metoda ochrany m\u016f\u017eeme omezit seznam podporovan\u00fdch metod v\u00fdm\u011bny kl\u00ed\u010d\u016f pouze na algoritmy se stejnou velikost\u00ed hashe. Nap\u0159\u00edklad pro vazbu na SHA256 lze do k\u00f3du p\u0159idat: rc = ssh_options_set(s->ssh.session, SSH_OPTIONS_KEY_EXCHANGE, \"diffie-hellman-group14-sha256,curve25519-sha256,ecdh-sha2-nistp256\"); \u0412 \u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a\u0435 libssh (\u043d\u0435 \u043f\u0443\u0442\u0430\u0442\u044c \u0441 libssh2), \u043f\u0440\u0435\u0434\u043d\u0430\u0437\u043d\u0430\u0447\u0435\u043d\u043d\u043e\u0439 \u0434\u043b\u044f \u0434\u043e\u0431\u0430\u0432\u043b\u0435\u043d\u0438\u044f \u043a\u043b\u0438\u0435\u043d\u0442\u0441\u043a\u043e\u0439 \u0438 \u0441\u0435\u0440\u0432\u0435\u0440\u043d\u043e\u0439 \u043f\u043e\u0434\u0434\u0435\u0440\u0436\u043a\u0438 \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b\u0430 SSHv2 \u0432 \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u044b \u043d\u0430 \u044f\u0437\u044b\u043a\u0435 \u0421\u0438, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2021-3634), \u043f\u0440\u0438\u0432\u043e\u0434\u044f\u0449\u0430\u044f \u043a \u043f\u0435\u0440\u0435\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044e \u0431\u0443\u0444\u0435\u0440\u0430 \u043f\u0440\u0438 \u0438\u043d\u0438\u0446\u0438\u0438\u0440\u043e\u0432\u0430\u043d\u0438\u0438 \u043f\u0440\u043e\u0446\u0435\u0441\u0441\u0430 \u0441\u043c\u0435\u043d\u044b \u043a\u043b\u044e\u0447\u0430 (rekey) \u0441 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u0435\u043c \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 \u043e\u0431\u043c\u0435\u043d\u0430 \u043a\u043b\u044e\u0447\u0430\u043c\u0438, \u043f\u0440\u0438\u043c\u0435\u043d\u044f\u044e\u0449\u0435\u0433\u043e \u0434\u0440\u0443\u0433\u043e\u0439 \u0430\u043b\u0433\u043e\u0440\u0438\u0442\u043c \u0445\u044d\u0448\u0438\u0440\u043e\u0432\u0430\u043d\u0438\u044f. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0430 \u0432 \u0432\u044b\u043f\u0443\u0441\u043a\u0435 0.9.6. \u0421\u0443\u0442\u044c \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0432 \u0442\u043e\u043c, \u0447\u0442\u043e \u043e\u043f\u0435\u0440\u0430\u0446\u0438\u044f \u0441\u043c\u0435\u043d\u044b […]<\/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-101115","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 libssh, kter\u00e1 vede k p\u0159ete\u010den\u00ed bufferu | ProHoster","description":"V knihovn\u011b libssh (nem\u00fdlit s libssh2), kter\u00e1 je ur\u010dena pro p\u0159id\u00e1n\u00ed klientsk\u00e9 a serverov\u00e9 podpory protokolu SSHv2 do program\u016f napsan\u00fdch v jazyce C, byla odhalena zranitelnost (CVE-2021-3634), kter\u00e1 m\u016f\u017ee v\u00e9st k p\u0159ete\u010den\u00ed.","canonical_url":"https:\/\/prohoster.info\/cs\/blog\/news\/uyazvimost-v-libssh-privodyashhaya-k-perepolneniyu-bufera","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\udd47\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0432 libssh, \u043f\u0440\u0438\u0432\u043e\u0434\u044f\u0449\u0430\u044f \u043a 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Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"