{"id":93917,"date":"2020-09-11T01:41:59","date_gmt":"2020-09-10T23:41:59","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-tls-dopuskayushhaya-opredelenie-klyucha-dlya-soedinenij-na-baze-shifrov-dh"},"modified":"2020-09-11T01:41:59","modified_gmt":"2020-09-10T23:41:59","slug":"uyazvimost-v-tls-dopuskayushhaya-opredelenie-klyucha-dlya-soedinenij-na-baze-shifrov-dh","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/uyazvimost-v-tls-dopuskayushhaya-opredelenie-klyucha-dlya-soedinenij-na-baze-shifrov-dh","title":{"rendered":"A vulnerability in TLS that allows the identification of keys for connections based on DH cipher.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Revealed<\/a><\/noindex> information about the new a vulnerability<\/a><\/noindex> (CVE-2020-1968) in the TLS protocol, codenamed
\nRaccoon<\/a><\/noindex> and allowing, under rare circumstances, to determine the pre-master secret, which can be used to decrypt TLS connections, including HTTPS, when intercepting transit traffic (MITM). It is noted that the attack is very complex to implement in practice and is more theoretical in nature. To carry out the attack, a specific configuration of the TLS server is required, along with the ability to measure the server's processing time for operations very precisely.<\/p>\n

The issue resides specifically in the TLS specification and affects only connections using ciphers based on the DH key exchange protocol (Diffie-Hellman, TLS_DH_*). The problem does not manifest with ECDH ciphers, which remain secure. Only TLS protocols up to and including version 1.2 are vulnerable; TLS 1.3 is not subject to this issue. The vulnerability occurs in TLS implementations that reuse the DH secret key across different TLS connections (such behavior is observed on approximately 4.4% of servers in the Alexa Top 1M ranking).<\/p>\n

In OpenSSL 1.0.2e and earlier releases, the primary DH key is reused across all server connections unless the SSL_OP_SINGLE_DH_USE option is explicitly set. Starting from OpenSSL 1.0.2f, the primary DH key is reused only when using static DH ciphers (\u2018DH-*\u2019, for example \u2018DH-RSA-AES256-SHA\u2019). In OpenSSL 1.1.1, the vulnerability does not manifest because this branch does not use the primary DH key and does not apply static DH ciphers. <\/p>\n

When using the DH key exchange method, both parties of the connection generate random private keys (hereafter referred to as key \u2018a\u2019 and key \u2018b\u2019), based on which public keys (ga mod p and gb mod p) are computed and sent. After receiving each other\u2019s public keys, both parties compute a shared primary key (gab mod p), which is applied to form session keys. The Raccoon attack allows for determining the primary key through analysis of information via side channels, based on the fact that, in TLS specifications up to version 1.2, it is prescribed to discard all leading zero bytes of the primary key before calculations involving it.<\/p>\n

This includes a truncated primary key being passed to a session key generation function based on hash functions with differing delays when processing different data. Accurate measurement of the time the server takes to perform operations with the key allows an attacker to identify hints (oracle) that indicate whether the primary key starts with zero or not. For example, an attacker could intercept the public key (ga) sent by the client, resend it to the server, and determine
\nwhether the resulting primary key starts with zero.<\/p>\n

The identification of a single byte of the key by itself is not significant, but by intercepting the value \u2018ga\u2019 transmitted during the connection negotiation by the client, an attacker can create a set of other values related to \u2018ga\u2019 and send them to the server in separate connection negotiation sessions. By forming and sending values \u2018gri*ga\u2019, the attacker can determine values leading to primary keys that start with zero through analysis of the changes in server response delays. Once identifying such values, the attacker can compile a set of equations for solutions<\/a><\/noindex> the hidden number problem<\/a><\/noindex> and compute the original primary key. <\/p>\n

\"A<\/center><\/p>\n

In OpenSSL vulnerabilities has been assigned<\/a><\/noindex> low level of danger, and the fix boiled down to moving in the release 1.0.2w the problematic ciphers «TLS_DH_*» to a disabled by default category of ciphers with insufficient protection level («weak-ssl-ciphers»). The developers at Mozilla did similarly. disabled<\/a><\/noindex> the DH and DHE cipher suites in the NSS library used in Firefox. Starting from Firefox 78, the problematic ciphers have been disabled. In Chrome, support for DH was discontinued back in 2016. The BearSSL, BoringSSL, Botan, Mbed TLS, and s2n libraries are not affected by this issue as they do not support DH ciphers or static variants of DH ciphers. <\/p>\n

Additionally, there are extra issues noted (CVE-2020-5929<\/a><\/noindex>) in the F5 BIG-IP device TLS stack that make the attack more realistic. In particular, discrepancies in device behavior with a zero byte at the beginning of the primary key have been identified, which can be used instead of measuring the exact time delay during computations.<\/p>\n

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

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

\u0420\u0430\u0441\u043a\u0440\u044b\u0442\u044b \u0441\u0432\u0435\u0434\u0435\u043d\u0438\u044f \u043e \u043d\u043e\u0432\u043e\u0439 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 (CVE-2020-1968) \u0432 \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b\u0435 TLS, \u043f\u043e\u043b\u0443\u0447\u0438\u0432\u0448\u0435\u0439 \u043a\u043e\u0434\u043e\u0432\u043e\u0435 \u0438\u043c\u044f Raccoon \u0438 \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0435\u0439 \u043f\u0440\u0438 \u0440\u0435\u0434\u043a\u043e\u043c \u0441\u0442\u0435\u0447\u0435\u043d\u0438\u0438 \u043e\u0431\u0441\u0442\u043e\u044f\u0442\u0435\u043b\u044c\u0441\u0442\u0432 \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0438\u0442\u044c \u043f\u0440\u0435\u0434\u0432\u0430\u0440\u0438\u0442\u0435\u043b\u044c\u043d\u044b\u0439 \u043f\u0435\u0440\u0432\u0438\u0447\u043d\u044b\u0439 \u043a\u043b\u044e\u0447 (pre-master), \u043a\u043e\u0442\u043e\u0440\u044b\u0439 \u043c\u043e\u0436\u043d\u043e \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u044c \u0434\u043b\u044f \u0440\u0430\u0441\u0448\u0438\u0444\u0440\u043e\u0432\u043a\u0438 TLS-\u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u0439, \u0432 \u0442\u043e\u043c \u0447\u0438\u0441\u043b\u0435 HTTPS, \u043f\u0440\u0438 \u043f\u0435\u0440\u0435\u0445\u0432\u0430\u0442\u0435 \u0442\u0440\u0430\u043d\u0437\u0438\u0442\u043d\u043e\u0433\u043e \u0442\u0440\u0430\u0444\u0438\u043a\u0430 (MITM). \u041e\u0442\u043c\u0435\u0447\u0430\u0435\u0442\u0441\u044f, \u0447\u0442\u043e \u0430\u0442\u0430\u043a\u0430 \u043e\u0447\u0435\u043d\u044c \u0441\u043b\u043e\u0436\u043d\u0430 \u0434\u043b\u044f \u043f\u0440\u0430\u043a\u0442\u0438\u0447\u0435\u0441\u043a\u043e\u0439 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u0438 \u0438 \u0431\u043e\u043b\u044c\u0448\u0435 \u043d\u043e\u0441\u0438\u0442 \u0442\u0435\u043e\u0440\u0435\u0442\u0438\u0447\u0435\u0441\u043a\u0438\u0439 \u0445\u0430\u0440\u0430\u043a\u0442\u0435\u0440. \u0414\u043b\u044f \u043f\u0440\u043e\u0432\u0435\u0434\u0435\u043d\u0438\u044f \u0430\u0442\u0430\u043a\u0438 […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":93918,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-93917","post","type-post","status-publish","format-standard","has-post-thumbnail","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\udd47 Vulnerability in TLS that allows for key determination for connections based on DH ciphers | ProHoster","description":"Information has been revealed about a new","canonical_url":"https:\/\/prohoster.info\/en\/blog\/news\/uyazvimost-v-tls-dopuskayushhaya-opredelenie-klyucha-dlya-soedinenij-na-baze-shifrov-dh","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"en_US","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 TLS, \u0434\u043e\u043f\u0443\u0441\u043a\u0430\u044e\u0449\u0430\u044f \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0435\u043d\u0438\u0435 \u043a\u043b\u044e\u0447\u0430 \u0434\u043b\u044f \u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u0439 \u043d\u0430 \u0431\u0430\u0437\u0435 \u0448\u0438\u0444\u0440\u043e\u0432 DH | ProHoster","og:description":"\u0420\u0430\u0441\u043a\u0440\u044b\u0442\u044b \u0441\u0432\u0435\u0434\u0435\u043d\u0438\u044f \u043e \u043d\u043e\u0432\u043e\u0439","og:url":"https:\/\/prohoster.info\/en\/blog\/news\/uyazvimost-v-tls-dopuskayushhaya-opredelenie-klyucha-dlya-soedinenij-na-baze-shifrov-dh","og:image":"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg","og:image:secure_url":"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg","og:image:width":350,"og:image:height":350,"article:published_time":"2020-09-10T23:41:59+00:00","article:modified_time":"2020-09-10T23:41:59+00:00","article:publisher":"https:\/\/www.facebook.com\/prohoster","article:author":"https:\/\/www.facebook.com\/prohoster"},"aioseo_meta_data":{"post_id":"93917","title":null,"description":null,"keywords":null,"keyphrases":null,"primary_term":null,"canonical_url":null,"og_title":null,"og_description":null,"og_object_type":"default","og_image_type":"default","og_image_url":null,"og_image_width":null,"og_image_height":null,"og_image_custom_url":null,"og_image_custom_fields":null,"og_video":null,"og_custom_url":null,"og_article_section":null,"og_article_tags":null,"twitter_use_og":false,"twitter_card":"default","twitter_image_type":"default","twitter_image_url":null,"twitter_image_custom_url":null,"twitter_image_custom_fields":null,"twitter_title":null,"twitter_description":null,"schema":{"blockGraphs":[],"customGraphs":[],"default":{"data":{"Article":[],"Course":[],"Dataset":[],"FAQPage":[],"Movie":[],"Person":[],"Product":[],"ProductReview":[],"Car":[],"Recipe":[],"Service":[],"SoftwareApplication":[],"WebPage":[]},"graphName":"","isEnabled":true},"graphs":[]},"schema_type":null,"schema_type_options":null,"pillar_content":false,"robots_default":true,"robots_noindex":false,"robots_noarchive":false,"robots_nosnippet":false,"robots_nofollow":false,"robots_noimageindex":false,"robots_noodp":false,"robots_notranslate":false,"robots_max_snippet":null,"robots_max_videopreview":null,"robots_max_imagepreview":"large","priority":null,"frequency":null,"local_seo":null,"seo_analyzer_scan_date":null,"breadcrumb_settings":null,"limit_modified_date":false,"reviewed_by":null,"ai":null,"created":"2021-02-28 11:37:29","updated":"2022-10-06 06:50:38","focus_keyword":null,"additional_keywords":null,"truseo_locale":null},"gt_translate_keys":[{"key":"link","format":"url"}],"_links":{"self":[{"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/posts\/93917","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/comments?post=93917"}],"version-history":[{"count":0,"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/posts\/93917\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/media\/93918"}],"wp:attachment":[{"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/media?parent=93917"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/categories?post=93917"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/prohoster.info\/en\/wp-json\/wp\/v2\/tags?post=93917"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}