Dans la biblioth\u00e8que libssh (\u00e0 ne pas confondre avec libssh2), con\u00e7ue pour ajouter un support client et serveur du protocole SSHv2 aux programmes en langage C, une vuln\u00e9rabilit\u00e9 (CVE-2021-3634) a \u00e9t\u00e9 identifi\u00e9e, entra\u00eenant un d\u00e9passement de tampon lors de l'initialisation du processus de changement de cl\u00e9 (rekey) en utilisant un m\u00e9canisme d'\u00e9change de cl\u00e9s qui applique un autre algorithme de hachage. Le probl\u00e8me a \u00e9t\u00e9 corrig\u00e9 dans la version 0.9.6. <\/p>\n
Le probl\u00e8me r\u00e9side dans le fait que l'op\u00e9ration de changement de cl\u00e9 permet d'utiliser des hachages cryptographiques dont la taille du hachage diff\u00e8re de celle de l'algorithme initialement utilis\u00e9. Ainsi, la m\u00e9moire pour le hachage dans libssh \u00e9tait allou\u00e9e en fonction de la taille initiale du hachage et l'utilisation d'un hachage de taille sup\u00e9rieure entra\u00eene l'\u00e9criture de donn\u00e9es au-del\u00e0 de la m\u00e9moire allou\u00e9e. Comme m\u00e9thode de protection compl\u00e9mentaire, on peut restreindre la liste des m\u00e9thodes de l'\u00e9change de cl\u00e9s uniquement aux algorithmes ayant la m\u00eame taille de hachage. Par exemple, pour se lier \u00e0 SHA256, on peut ajouter dans le code : 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\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\udd47Vuln\u00e9rabilit\u00e9 dans libssh entra\u00eenant un d\u00e9passement de tampon | ProHoster","description":"Dans la biblioth\u00e8que libssh (\u00e0 ne pas confondre avec 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Source : opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"