{"id":109263,"date":"2023-07-05T21:10:21","date_gmt":"2023-07-05T19:10:24","guid":{"rendered":"https:\/\/prohoster.info\/?p=109263"},"modified":"2023-07-06T09:41:50","modified_gmt":"2023-07-06T07:41:50","slug":"uyazvimost-konfiguraczij-nginx-s-nekorrektnymi-nastrojkami-bloka-alias","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/uyazvimost-konfiguraczij-nginx-s-nekorrektnymi-nastrojkami-bloka-alias","title":{"rendered":"Vulnerability in Nginx configurations with incorrect alias block settings","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Some servers with nginx remain vulnerable to the Nginx Alias Traversal technique, which was proposed at the Blackhat conference back in 2018 and allows access to files and directories located outside the root directory specified in the 'alias' directive. The issue only manifests in configurations with the 'alias' directive placed inside a 'location' block, where the parameter does not end with the '\/' character, while the 'alias' does end with '\/'.

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

The essence of the problem is that files for blocks with the alias directive are delivered by appending the requested path after matching it with the location directive's pattern and stripping the specified part of the path. For the vulnerable configuration illustrated above, an attacker can request the file '\/img..\/test.txt', and this request will fall under the specified location mask '\/img', after which the remaining tail '..\/test.txt' will be appended to the path from the alias directive '\/var\/images\/'. Ultimately, the file '\/var\/images\/..\/test.txt' will be requested. Thus, attackers may gain access to any files in the '\/var' directory, not just the files in '\/var\/images\/', for example, to download the nginx log, one could send a request '\/img..\/log\/nginx\/access.log'. <\/p>\n

In configurations where the value of the alias directive does not end with the '\/' character (for example, 'alias \/var\/images;'), an attacker cannot ascend to the parent directory but can request another directory in \/var that begins with the name specified in the configuration. For example, by requesting '\/img.old\/test.txt', it is possible to access the directory 'var\/images.old\/test.txt'. <\/p>\n

An analysis of repositories on GitHub has shown that the errors in nginx configuration leading to this issue are still present in real projects. For instance, the problem was identified in the server side of the Bitwarden password manager and could be used to access all files in the \/etc\/bitwarden directory (requests to \/attachments were served from \/etc\/bitwarden\/attachments\/), including the stored database with passwords 'vault.db', certificates, and logs, which could be retrieved just by sending requests to '\/attachments..\/vault.db', '\/attachments..\/identity.pfx', '\/attachments..\/logs\/api.log', etc.

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

The method also worked with the Google HPC Toolkit, where requests for \/static were redirected to the directory \"..\/hpc-toolkit\/community\/front-end\/website\/static\/\". To obtain the database with the secret key and credentials, the attacker could send requests for \"..\/static..\/\/.secret_key\" and \"..\/static..\/\/db.sqlite3\".

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

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[…]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":109264,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-109263","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 of Nginx configurations with incorrect alias block settings | ProHoster","description":"Some servers with nginx remain vulnerable to the Nginx Alias Traversal technique, which was introduced at the Blackhat conference back in 2018 and allows access to files and directories located 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