Nginx jwt auth module

This is an NGINX module to check for a valid JWT, this module intend to be as light as possible and to remain simple:

• Docker image based on the official nginx Dockerfile (alpine).
• Light image (~400KB more than the official one).

Table of Contents:

• Module configuration
• Directives
• Embedded variables
• Image
• Example configurations

Module Configuration:

Example Configuration:

# nginx.conf
load_module /usr/lib/nginx/modules/ngx_http_auth_jwt_module.so;

http {
    server {
        auth_jwt_key "0123456789abcdef" hex; # Your key as hex string
        auth_jwt     off;

        # Default auth method is "Authentication" header
        location /secured-by-auth-header/ {
            auth_jwt on;
        }

        # But you can use a cookie instead
        location /secured-by-cookie/ {
            auth_jwt $cookie_MyCookieName;
        }

        # JWT keys are inherited from the previous configuration level
        # but you can have different keys for different locations
        location /secured-by-auth-header-too/ {
            auth_jwt_key "another-secret"; # Your key as utf8 string
            auth_jwt on;
        }

        location /secured-by-rsa-key/ {
            auth_jwt_key /etc/keys/rsa-public.pem file; # Your key from a PEM file
            auth_jwt on;
        }

        location /not-secure/ {}
    }
}

Note: don't forget to load the module in the main context:

load_module /usr/lib/nginx/modules/ngx_http_auth_jwt_module.so;

Directives:

auth_jwt

Syntax:	 auth_jwt $variable | on | off;
Default: auth_jwt off;
Context: http, server, location

Enables validation of JWT.

The auth_jwt $variable value can be used to set a custom way to get the JWT, for example to get it from a cookie instead of the default Authentication header: auth_jwt $cookie_MyCookieName;

---

auth_jwt_key

Syntax:	 auth_jwt_key value [encoding];
Default: ——
Context: http, server, location

Specifies the key for validating JWT signature (must be hexadecimal).
The encoding option may be hex | utf8 | base64 | file (default is utf8).
The file option requires the value to be a valid file path (pointing to a PEM encoded key).

---

auth_jwt_alg

Syntax:	 auth_jwt_alg any | HS256 | HS384 | HS512 | RS256 | RS384 | RS512 | ES256 | ES384 | ES512;
Default: auth_jwt_alg any;
Context: http, server, location

Specifies which algorithm the server expects to receive in the JWT.

---

auth_jwt_require

Syntax:	 auth_jwt_require $value ... [error=401 | 403];
Default: ——
Context: http, server, location

Specifies additional checks for JWT validation. The authentication will succeed only if all the values are not empty and are not equal to “0”.

These directives are inherited from the previous configuration level if and only if there are no auth_jwt_require directives defined on the current level.

If any of the checks fails, the 401 error code is returned. The optional error parameter allows redefining the error code to 403.

Example:

# server.conf

map $jwt_claim_role $jwt_has_admin_role {
    \"admin\"  1;
}

map $jwt_claim_scope $jwt_has_restricted_scope {
    \"restricted\"  1;
}

server {
  # ...

  location /auth-require {
    auth_jwt_require $jwt_has_admin_role error=403;
    # ...
  }

  location /auth-compound-require {
    auth_jwt_require $jwt_has_admin_role $jwt_has_restricted_scope error=403;
    # ...
  }
}

Note that as $jwt_claim_ returns a JSON-encoded value, so we have to check \"value\" (and not value)

Embedded Variables:

The ngx_http_auth_jwt_module module supports embedded variables:

• $jwt_header_name returns the specified header value
• $jwt_claim_name returns the specified claim value
• $jwt_headers returns headers
• $jwt_payload returns payload

Note that as all returned values are JSON-encoded, so string will be surrounded by " character

Image:

Image is generated with Github Actions (see nginx-jwt-module:latest)

docker pull ghcr.io/max-lt/nginx-jwt-module:latest

Simply create your image from Github's generated one

FROM ghcr.io/max-lt/nginx-jwt-module:latest

# Copy your nginx conf
# Don't forget to include this module in your configuration
# load_module /usr/lib/nginx/modules/ngx_http_auth_jwt_module.so;
COPY my-nginx-conf /etc/nginx

EXPOSE 8000

STOPSIGNAL SIGTERM

CMD ["nginx", "-g", "daemon off;"]

Or use the provided one directly

docker run -p 80:80 \
  -v ./nginx.conf:/etc/nginx/nginx.conf \
  ghcr.io/max-lt/nginx-jwt-module

Build:

This module is built inside a docker container, from the nginx-alpine image.

make build # Will create a "jwt-nginx" image
# or
docker build -f Dockerfile -t jwt-nginx .

Test:

Default usage:

make test # Will build a test image and run the test suite

Example configurations:

In this section, we will see some examples of how to use this module.

Redirect to login page if JWT is invalid:

load_module /usr/lib/nginx/modules/ngx_http_auth_jwt_module.so;

# ...

http {
    server {
        listen 80;
        server_name _;

        auth_jwt_key "0123456789abcdef" hex; # Your key as hex string
        auth_jwt     off;

        location @login_err_redirect {
            return 302 $scheme://$host:$server_port/login?redirect=$request_uri;
        }

        location /secure/ {
            auth_jwt on;
            error_page 401 = @login_err_redirect;
        }

        location / {
            return 200 "OK";
        }
    }
}

Trying curl -i http://localhost/secure/path?param=value will return a 302 redirect to /login?redirect=/secure/path?param=value if the JWT is invalid.