{"id":40697,"date":"2020-02-03T14:36:04","date_gmt":"2020-02-03T11:36:04","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/obnovlenie-openwrt-19-07-1-s-ustraneniem-uyazvimosti-dopuskayushhej-podmenu-paketov"},"modified":"2020-02-03T14:36:04","modified_gmt":"2020-02-03T11:36:04","slug":"obnovlenie-openwrt-19-07-1-s-ustraneniem-uyazvimosti-dopuskayushhej-podmenu-paketov","status":"publish","type":"post","link":"https:\/\/prohoster.info\/pt\/blog\/obnovlenie-openwrt-19-07-1-s-ustraneniem-uyazvimosti-dopuskayushhej-podmenu-paketov","title":{"rendered":"Atualiza\u00e7\u00e3o do OpenWrt 19.07.1 corrigindo uma vulnerabilidade que permite a substitui\u00e7\u00e3o de pacotes","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Lan\u00e7adas vers\u00f5es corrigidas da distribui\u00e7\u00e3o OpenWrt 18.06.7<\/a><\/noindex> e 19.07.1<\/a><\/noindex>, nas quais foi corrigida uma vulnerabilidade cr\u00edtica<\/a><\/noindex> (CVE-2020-7982) no gerenciador de pacotes opkg<\/a><\/noindex>, permitindo a realiza\u00e7\u00e3o de um ataque MITM e a substitui\u00e7\u00e3o do conte\u00fado do pacote baixado do reposit\u00f3rio. Devido a um erro na verifica\u00e7\u00e3o das somas de verifica\u00e7\u00e3o, o atacante pode criar condi\u00e7\u00f5es nas quais as somas SHA-256 presentes no \u00edndice de pacotes assinado digitalmente ser\u00e3o ignoradas, permitindo contornar os mecanismos de verifica\u00e7\u00e3o da integridade dos recursos ipk baixados.<\/p>\n

O problema se manifesta desde fevereiro de 2017, ap\u00f3s a adi\u00e7\u00e3o<\/a><\/noindex> de um c\u00f3digo para ignorar os espa\u00e7os iniciais que precedem a soma de verifica\u00e7\u00e3o. Devido a um erro ao ignorar os espa\u00e7os, o ponteiro na posi\u00e7\u00e3o da string n\u00e3o se deslocava, e o ciclo de decodifica\u00e7\u00e3o da sequ\u00eancia hexadecimal SHA-256 retornava imediatamente e fornecia uma soma de verifica\u00e7\u00e3o de comprimento zero. <\/p>\n

Como o gerenciador de pacotes opkg no OpenWrt \u00e9 executado com privil\u00e9gios de root, em caso de ataque MITM, um invasor pode sutilmente alterar o pacote ipk baixado do reposit\u00f3rio durante a execu\u00e7\u00e3o do comando «opkg install» pelo usu\u00e1rio, e fazer com que seu c\u00f3digo seja executado com privil\u00e9gios de root ao adicionar scripts manipuladores ao pacote, que s\u00e3o chamados durante a instala\u00e7\u00e3o. Para explorar a vulnerabilidade, o atacante tamb\u00e9m deve substituir o \u00edndice de pacotes correto e assinado (por exemplo, aquele fornecido por downloads.openwrt.org). O tamanho do pacote alterado deve corresponder ao tamanho original, conforme definido no \u00edndice.<\/p>\n

Em situa\u00e7\u00f5es onde \u00e9 necess\u00e1rio evitar a atualiza\u00e7\u00e3o completa do firmware, \u00e9 poss\u00edvel atualizar apenas o gerenciador de pacotes opkg, executando os seguintes comandos:<\/p>\n

cd \/tmp
\n opkg update
\n opkg download opkg
\n zcat .\\\/opkg-lists\\\/openwrt_base | grep -A10 «Package: opkg» | grep SHA256sum
\n sha256sum .\/opkg_2020-01-25-c09fe209-1_*.ipk<\/p>\n

Em seguida, deve-se comparar as somas de verifica\u00e7\u00e3o apresentadas e, se coincidirem, executar:<\/p>\n

opkg install .\/opkg_2020-01-25-c09fe209-1_*.ipk<\/p>\n

Nas novas vers\u00f5es, tamb\u00e9m foi corrigida mais uma uma vulnerabilidade<\/a><\/noindex> na biblioteca libubox<\/a><\/noindex>, que pode levar a uma sobrecarga de buffer ao processar na fun\u00e7\u00e3o blobmsg_format_json<\/a><\/noindex> dados bin\u00e1rios serializados especificamente formatados ou dados no formato JSON. A biblioteca \u00e9 utilizada em componentes da distribui\u00e7\u00e3o, como netifd, procd, ubus, rpcd e uhttpd, assim como no pacote auc<\/a><\/noindex> (Atualiza\u00e7\u00e3o de sistema asistida via CLI). O estouro de buffer ocorre ao transferir grandes atributos num\u00e9ricos do tipo «double» em blocos blob. Para verificar se o sistema \u00e9 vulner\u00e1vel, execute o comando:<\/p>\n

$ ubus call luci getFeatures \
\n ‘{ «banik»: 00192200197600198000198100200400.1922 }’<\/p>\n

Al\u00e9m de eliminar vulnerabilidades e corrigir erros acumulados na vers\u00e3o OpenWrt 19.07.1, a vers\u00e3o do n\u00facleo Linux foi atualizada (de 4.14.162 para 4.14.167), problemas de desempenho ao usar frequ\u00eancias de 5GHz foram resolvidos, e a compatibilidade com dispositivos Ubiquiti Rocket M Titanium, Netgear WN2500RP v1,
\n Zyxel NSA325, Netgear WNR3500 V2, Archer C6 v2, Ubiquiti EdgeRouter-X, Archer C20 v4, Archer C50 v4, Archer MR200, TL-WA801ND v5, HiWiFi HC5962, Xiaomi Mi Router 3 Pro e Netgear R6350.<\/p>\n

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

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

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