secure_link_md5
The `secure_link_md5` directive generates and validates MD5 hashes for secure linking to files.
Description
The secure_link_md5 directive is used to implement a method of secure access control to files in NGINX. This is primarily used to protect resources from unauthorized access by generating an MD5 hash based on a predefined secret key, a specific request URI, and a timestamp. When a request is made for a resource, the directive checks the generated hash against the submitted hash in the request to verify the legitimacy and validity of the link. If the hashes match and the timestamp is within an acceptable range, access is granted; otherwise, it is denied.
The parameter for secure_link_md5 is a string that should contain the shared secret, the URI, and an expiration time. The expiration time determines how long the generated link remains valid, enhancing security by limiting the duration a link can be used. This is particularly useful in scenarios where access to sensitive resources is needed but should not be broadly accessible, such as file downloads or premium content.
To enable this directive effectively, it is imperative to ensure that the same hashing algorithm and parameters are used on both the server and the client-side to maintain consistency and security between the generated and the submitted MD5 hashes. This directive is configurable within multiple contexts, including http, server, and location, allowing for flexible implementations based on the structure of the application.
Config Example
location /private {
secure_link_md5 "$arg_md5$uri$time$remote_addr";
secure_link "";
if ($secure_link = 0) {
return 403;
}
# Protected resource access would follow
}Ensure that the hashing algorithm is consistent across both server and client implementations.
Be mindful of time synchronization between server and client to avoid premature expiry of links.
Always use secure (https) connections to prevent interception of the link data.