{"id":55921,"date":"2020-02-01T00:00:00","date_gmt":"2020-01-31T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os"},"modified":"2020-02-18T14:04:05","modified_gmt":"2020-02-18T11:04:05","slug":"root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os","status":"publish","type":"post","link":"https:\/\/prohoster.info\/pt\/blog\/news\/root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os","title":{"rendered":"Vulnerabilidade root no sudo, afetando o Linux Mint e o Elementary OS","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

No utilit\u00e1rio sudo<\/a><\/noindex>, utilizado para executar comandos em nome de outros usu\u00e1rios, foi identificada<\/a><\/noindex> vulnerabilidade (CVE-2019-18634<\/a><\/noindex>), permitindo aumentar seus privil\u00e9gios no sistema para o usu\u00e1rio root. O problema se manifesta a partir da vers\u00e3o sudo 1.7.1, apenas quando a op\u00e7\u00e3o «pwfeedback» est\u00e1 ativada no arquivo \/etc\/sudoers, que est\u00e1 desativada por padr\u00e3o, mas ativada em algumas distribui\u00e7\u00f5es, como Linux Mint e Elementary OS. O problema foi resolvido na vers\u00e3o sudo 1.8.31<\/a><\/noindex>, publicada h\u00e1 algumas horas. Nas distribui\u00e7\u00f5es, a vulnerabilidade ainda permanece n\u00e3o corrigida.<\/p>\n

A op\u00e7\u00e3o «pwfeedback» ativa a exibi\u00e7\u00e3o do s\u00edmbolo «*» ap\u00f3s cada caractere digitado ao inserir a senha. Devido a um erro<\/a><\/noindex> uma falha na implementa\u00e7\u00e3o da fun\u00e7\u00e3o getln(), definida no arquivo tgetpass.c, uma string com senha muito longa passada pelo fluxo de entrada padr\u00e3o (stdin) pode n\u00e3o caber no buffer alocado e sobrescrever outros dados na pilha em determinadas condi\u00e7\u00f5es. O estouro ocorre durante a execu\u00e7\u00e3o do c\u00f3digo sudo com privil\u00e9gios de root.<\/p>\n

A ess\u00eancia do problema \u00e9 que, ao usar o caractere especial ^U (limpar linha) durante a entrada e em caso de falha na opera\u00e7\u00e3o de grava\u00e7\u00e3o, o c\u00f3digo respons\u00e1vel por limpar os caracteres exibidos «*» redefine os dados sobre o tamanho do buffer dispon\u00edvel, mas n\u00e3o retorna o ponteiro da posi\u00e7\u00e3o atual no buffer ao valor inicial. Outro fator que contribui para a explora\u00e7\u00e3o \u00e9 a aus\u00eancia de desconex\u00e3o autom\u00e1tica do modo «pwfeedback» ao receber dados que n\u00e3o v\u00eam do terminal, mas atrav\u00e9s de um fluxo de entrada (essa falha permite criar condi\u00e7\u00f5es para a ocorr\u00eancia de um erro de grava\u00e7\u00e3o, por exemplo, em sistemas com dire\u00e7\u00f5es unidirecionais n\u00e3o nomeados<\/a><\/noindex> o erro ocorre ao tentar escrever al\u00e9m do final do canal para leitura).<\/p>\n

Como o atacante pode controlar completamente a regrava\u00e7\u00e3o de dados na pilha, n\u00e3o \u00e9 dif\u00edcil criar um exploit que permita elevar seus privil\u00e9gios para o usu\u00e1rio root. O problema pode ser explorado por qualquer usu\u00e1rio, independentemente dos direitos de uso do sudo e da presen\u00e7a de configura\u00e7\u00f5es espec\u00edficas do usu\u00e1rio no sudoers. Para bloquear o problema, \u00e9 preciso garantir que a configura\u00e7\u00e3o «pwfeedback» n\u00e3o esteja presente em \/etc\/sudoers e, se necess\u00e1rio, desativ\u00e1-la («Defaults !pwfeedback»). Para verificar a exist\u00eancia do problema, \u00e9 poss\u00edvel executar o c\u00f3digo:<\/p>\n

$ perl -e ‘print((«A» x 100 . «\x{00}») x 50)’ | sudo -S id
\n Senha: Falha de segmenta\u00e7\u00e3o<\/p>\n

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

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

\u0412 \u0443\u0442\u0438\u043b\u0438\u0442\u0435 sudo, \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u0435\u043c\u043e\u0439 \u0434\u043b\u044f \u043e\u0440\u0433\u0430\u043d\u0438\u0437\u0430\u0446\u0438\u0438 \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f \u043a\u043e\u043c\u0430\u043d\u0434 \u043e\u0442 \u0438\u043c\u0435\u043d\u0438 \u0434\u0440\u0443\u0433\u0438\u0445 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2019-18634), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043f\u043e\u0432\u044b\u0441\u0438\u0442\u044c \u0441\u0432\u043e\u0438 \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0438 \u0432 \u0441\u0438\u0441\u0442\u0435\u043c\u0435 \u0434\u043e \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u044f root. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u043f\u0440\u043e\u044f\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u043d\u0430\u0447\u0438\u043d\u0430\u044f \u0441 \u0432\u044b\u043f\u0443\u0441\u043a\u0430 sudo 1.7.1 \u0442\u043e\u043b\u044c\u043a\u043e \u043f\u0440\u0438 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u0438 \u0432 \u0444\u0430\u0439\u043b\u0435 \/etc\/sudoers \u043e\u043f\u0446\u0438\u0438 «pwfeedback», \u043a\u043e\u0442\u043e\u0440\u0430\u044f \u043e\u0442\u043a\u043b\u044e\u0447\u0435\u043d\u0430 \u043f\u043e \u0443\u043c\u043e\u043b\u0447\u0430\u043d\u0438\u044e, \u043d\u043e \u0430\u043a\u0442\u0438\u0432\u0438\u0440\u043e\u0432\u0430\u043d\u0430 \u0432 \u043d\u0435\u043a\u043e\u0442\u043e\u0440\u044b\u0445 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445, \u0442\u0430\u043a\u0438\u0445 \u043a\u0430\u043a Linux Mint \u0438 Elementary OS. […]<\/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-55921","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\udd47Vulnerabilidade root no sudo, afetando Linux Mint e Elementary OS | ProHoster","description":"Na utilidade sudo, utilizada para executar comandos em nome de outros 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