Foi lan\u00e7ado o OpenSSH 8.8, uma implementa\u00e7\u00e3o aberta do cliente e servidor para trabalhar com os protocolos SSH 2.0 e SFTP. Esta vers\u00e3o \u00e9 not\u00e1vel por desabilitar, por padr\u00e3o, a utiliza\u00e7\u00e3o de assinaturas digitais baseadas em chaves RSA com hash SHA-1 («ssh-rsa»). <\/p>\n
A interrup\u00e7\u00e3o do suporte para assinaturas «ssh-rsa» \u00e9 devida ao aumento da efic\u00e1cia de ataques de colis\u00e3o com prefixo definido (o custo para encontrar uma colis\u00e3o \u00e9 estimado em cerca de 50 mil d\u00f3lares). Para verificar a aplica\u00e7\u00e3o do ssh-rsa em seus sistemas, voc\u00ea pode tentar se conectar via ssh com a op\u00e7\u00e3o «-oHostKeyAlgorithms=-ssh-rsa». O suporte para assinaturas RSA com hashes SHA-256 e SHA-512 (rsa-sha2-256\/512), que s\u00e3o suportadas desde o OpenSSH 7.2, permanece inalterado. <\/p>\n
Na maioria dos casos, a interrup\u00e7\u00e3o do suporte «ssh-rsa» n\u00e3o exigir\u00e1 a\u00e7\u00f5es manuais por parte dos usu\u00e1rios, uma vez que o OpenSSH j\u00e1 tinha ativado por padr\u00e3o a configura\u00e7\u00e3o UpdateHostKeys, que realiza a transi\u00e7\u00e3o autom\u00e1tica dos clientes para algoritmos mais seguros. Para migra\u00e7\u00e3o, \u00e9 utilizado a extens\u00e3o do protocolo «hostkeys@openssh.com», que permite servidor<\/a> informar ao cliente sobre todas as chaves de host dispon\u00edveis ap\u00f3s a autentica\u00e7\u00e3o. No caso de conex\u00f5es com hosts que utilizam vers\u00f5es muito antigas do OpenSSH do lado do cliente, pode-se optar por restaurar a possibilidade de usar assinaturas «ssh-rsa», adicionando ao ~\/.ssh\/config: Host nome_do_host_antigo HostkeyAlgorithms +ssh-rsa \tPubkeyAcceptedAlgorithms +ssh-rsa <\/p>\n A nova vers\u00e3o tamb\u00e9m corrige um problema de seguran\u00e7a causado pelo fato de que no sshd, a partir da vers\u00e3o OpenSSH 6.2, a inicializa\u00e7\u00e3o do grupo de usu\u00e1rios ao executar comandos especificados nas diretivas AuthorizedKeysCommand e AuthorizedPrincipalsCommand estava incorreta. Essas diretivas deveriam garantir a execu\u00e7\u00e3o de comandos sob outro usu\u00e1rio, mas na pr\u00e1tica, herdavam a lista de grupos utilizada ao iniciar o sshd. Potencialmente, esse comportamento, em certas configura\u00e7\u00f5es de sistema, permitia que o manipulador em execu\u00e7\u00e3o obtivesse privil\u00e9gios adicionais no sistema. <\/p>\n Nas notas da nova vers\u00e3o, tamb\u00e9m foi publicado um aviso sobre a inten\u00e7\u00e3o de mudar o utilit\u00e1rio scp para usar SFTP como padr\u00e3o, em vez do obsoleto protocolo SCP\/RCP. O SFTP utiliza m\u00e9todos de manuseio de nomes mais previs\u00edveis e n\u00e3o utiliza processamento de padr\u00f5es globais em nomes de arquivos atrav\u00e9s do shell no lado do outro host, o que causa problemas de seguran\u00e7a. Em particular, ao usar SCP e RCP servidor<\/a> decidir quais arquivos e diret\u00f3rios enviar ao cliente, enquanto o cliente apenas verifica a validade dos nomes dos objetos retornados, o que, na aus\u00eancia de verifica\u00e7\u00f5es adequadas do lado do cliente, permite que o servidor envie outros nomes de arquivos diferentes dos solicitados. O protocolo SFTP n\u00e3o possui esses problemas, mas n\u00e3o suporta a revela\u00e7\u00e3o de caminhos especiais, como «~\\\/». Para eliminar essa discrep\u00e2ncia, na vers\u00e3o anterior do OpenSSH, foi proposta uma nova extens\u00e3o do protocolo SFTP para revelar os caminhos ~\\\/ e ~user\\\/. \u041e\u043f\u0443\u0431\u043b\u0438\u043a\u043e\u0432\u0430\u043d \u0440\u0435\u043b\u0438\u0437 OpenSSH 8.8, \u043e\u0442\u043a\u0440\u044b\u0442\u043e\u0439 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u0438 \u043a\u043b\u0438\u0435\u043d\u0442\u0430 \u0438 \u0441\u0435\u0440\u0432\u0435\u0440\u0430 \u0434\u043b\u044f \u0440\u0430\u0431\u043e\u0442\u044b \u043f\u043e \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b\u0430\u043c SSH 2.0 \u0438 SFTP. \u0412\u044b\u043f\u0443\u0441\u043a \u043f\u0440\u0438\u043c\u0435\u0447\u0430\u0442\u0435\u043b\u0435\u043d \u043e\u0442\u043a\u043b\u044e\u0447\u0435\u043d\u0438\u0435\u043c \u043f\u043e \u0443\u043c\u043e\u043b\u0447\u0430\u043d\u0438\u044e \u0432\u043e\u0437\u043c\u043e\u0436\u043d\u043e\u0441\u0442\u0438 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u044f \u0446\u0438\u0444\u0440\u043e\u0432\u044b\u0445 \u043f\u043e\u0434\u043f\u0438\u0441\u0435\u0439 \u043d\u0430 \u0431\u0430\u0437\u0435 RSA-\u043a\u043b\u044e\u0447\u0435\u0439 \u0441 \u0445\u044d\u0448\u0435\u043c SHA-1 («ssh-rsa»). \u041f\u0440\u0435\u043a\u0440\u0430\u0449\u0435\u043d\u0438\u0435 \u043f\u043e\u0434\u0434\u0435\u0440\u0436\u043a\u0438 \u043f\u043e\u0434\u043f\u0438\u0441\u0435\u0439 «ssh-rsa» \u043e\u0431\u0443\u0441\u043b\u043e\u0432\u043b\u0435\u043d\u043e \u043f\u043e\u0432\u044b\u0448\u0435\u043d\u0438\u0435\u043c \u044d\u0444\u0444\u0435\u043a\u0442\u0438\u0432\u043d\u043e\u0441\u0442\u0438 \u043a\u043e\u043b\u043b\u0438\u0437\u0438\u043e\u043d\u043d\u044b\u0445 \u0430\u0442\u0430\u043a \u0441 \u0437\u0430\u0434\u0430\u043d\u043d\u044b\u043c \u043f\u0440\u0435\u0444\u0438\u043a\u0441\u043e\u043c (\u0441\u0442\u043e\u0438\u043c\u043e\u0441\u0442\u044c \u043f\u043e\u0434\u0431\u043e\u0440\u0430 \u043a\u043e\u043b\u043b\u0438\u0437\u0438\u0438 \u043e\u0446\u0435\u043d\u0438\u0432\u0430\u0435\u0442\u0441\u044f \u043f\u0440\u0438\u043c\u0435\u0440\u043d\u043e \u0432 50 \u0442\u044b\u0441\u044f\u0447 \u0434\u043e\u043b\u043b\u0430\u0440\u043e\u0432). \u0414\u043b\u044f […]<\/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-101430","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\udd47Lan\u00e7amento do OpenSSH 8.8 com desativa\u00e7\u00e3o do suporte a assinaturas digitais rsa-sha | 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Fonte: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"