encrypted-session: Encrypt and decrypt NGINX variable values

Installation

You can install this module in any RHEL-based distribution, including, but not limited to:

• RedHat Enterprise Linux 7, 8, 9
• CentOS 7, 8, 9
• AlmaLinux 8, 9
• Rocky Linux 8, 9
• Amazon Linux 2 and Amazon Linux 2023

yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install nginx-module-encrypted-session

Enable the module by adding the following at the top of /etc/nginx/nginx.conf:

load_module modules/ngx_http_encrypted_session_module.so;

This document describes nginx-module-encrypted-session v0.9 released on Nov 18 2021.

---

encrypted-session-nginx-module - encrypt and decrypt nginx variable values

installation instructions.

Status

This module is production ready.

Synopsis

## key must be of 32 bytes long
encrypted_session_key "abcdefghijklmnopqrstuvwxyz123456";

## iv must not be longer than 16 bytes
## default: "deadbeefdeadbeef" (w/o quotes)
encrypted_session_iv "1234567812345678";

## default: 1d (1 day)
encrypted_session_expires 3600; # in sec

location /encrypt {
    set $raw 'text to encrypted'; # from the ngx_rewrite module
    set_encrypt_session $session $raw;
    set_encode_base32 $session; # from the ngx_set_misc module

    add_header Set-Cookie 'my_login=$session';  # from the ngx_headers module

    # your content handler goes here...
}

location /decrypt {
    set_decode_base32 $session $cookie_my_login; # from the ngx_set_misc module
    set_decrypt_session $raw $session;

    if ($raw = '') {
        # bad session
    }

    # your content handler goes here...
}

Description

This module provides encryption and decryption support for nginx variables based on AES-256 with Mac.

This module is usually used with the ngx_set_misc module and the standard rewrite module's directives.

This module can be used to implement simple user login and ACL.

Usually, you just decrypt data in nginx level, and pass the unencrypted data to your FastCGI/HTTP backend, as in

location /blah {
    set_decrypt_session $raw_text $encrypted;

    # this directive is from the ngx_set_misc module
    set_escape_uri $escaped_raw_text $raw_text;

    fastcgi_param QUERY_STRING "uid=$uid";
    fastcgi_pass unix:/path/to/my/php/or/python/fastcgi.sock;
}

Lua web applications running directly on ngx_lua can call this module's directives directly from within Lua code:

local raw_text = ndk.set_var.set_decrypt_session(encrypted_text)

Directives

encrypted_session_key

syntax: encrypted_session_key <key>

default: no

context: http, server, server if, location, location if

Sets the key for the cipher (must be 32 bytes long). For example,

encrypted_session_key "abcdefghijklmnopqrstuvwxyz123456";

encrypted_session_iv

syntax: encrypted_session_iv <iv>

default: encrypted_session_iv "deadbeefdeadbeef";

context: http, server, server if, location, location if

Sets the initial vector used for the cipher (must be no longer than 16 bytes).

For example,

encrypted_session_iv "12345678";

encrypted_session_expires

syntax: encrypted_session_expires <time>

default: encrypted_session_expires 1d;

context: http, server, server if, location, location if

Sets expiration time difference (in seconds by default).

For example, consider the following configuration:

encypted_session_expires 1d;

When your session is being generated, ngx_encrypted_session will plant an expiration time (1 day in the future in this example) into the encrypted session string, such that when the session is being decrypted later, the server can pull the expiration time out of the session and compare it with the server's current system time. No matter how you transfer and store your session, like using cookies, or URI query arguments, or whatever.

People may confuse this setting with the expiration date of HTTP cookies. This directive simply controls when the session gets expired; it knows nothing about HTTP cookies. Even if the end user intercepted this session from cookie by himself and uses it later manually, the server will still reject it when the expiration time gets passed.

set_encrypt_session

syntax: set_encrypt_session $target <value>

default: no

context: http, server, server if, location, location if

Encrypts the string value specified by the value argument and saves the result into the variable specified by $target.

For example,

set_encrypt_session $res $value;

will encrypts the value in the variable $value into the target variable $res.

The value argument can also be an nginx string value, for example,

set_encrypt_session $res "my value = $value";

The resulting data can later be decrypted via the set_decrypt_session directive.

set_decrypt_session

syntax: set_decrypt_session $target <value>

default: no

context: http, server, server if, location, location if

Similar to set_encrypt_session, but performs the inverse operation, that is, to decrypt things.

Report Bugs

Although a lot of effort has been put into testing and code tuning, there must be some serious bugs lurking somewhere in this module. So whenever you are bitten by any quirks, please don't hesitate to

1. send a bug report or even patches to agentzh@gmail.com,
2. or create a ticket on the issue tracking interface provided by GitHub.

Source Repository

Available on github at openresty/encrypted-session-nginx-module.

Getting involved

You'll be very welcomed to submit patches to the author or just ask for a commit bit to the source repository on GitHub.

Copyright & License

Copyright (c) 2009-2018, Yichun Zhang (agentzh) <agentzh@gmail.com>, OpenResty Inc.

This module is licensed under the terms of the BSD license.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

See Also

• NDK
• ngx_set_misc module

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-encrypted-session.