OWASP Coraza

NGINX

Coraza NGINX Connector

The coraza-nginx connector is the connection point between nginx and libcoraza. The module simply serves as a layer of communication between nginx and Coraza.

Compilation

If you have any doubts, please read the GitHub build Action for additional information.

Before compiling this software make sure that you have libcoraza installed. You can download it from the libcoraza git repository. For information pertaining to the compilation and installation of libcoraza please consult the documentation provided along with it.

To build libcoraza from source (requires Go 1.21+):

cd /path/to/libcoraza
./build.sh
./configure
make
sudo make install
sudo ldconfig

With libcoraza installed, you can proceed with the installation of the coraza-nginx connector, which follows the nginx third-party module installation procedure. From the nginx source directory:

./configure --add-module=/path/to/coraza-nginx

Or, to build a dynamic module:

./configure --add-dynamic-module=/path/to/coraza-nginx --with-compat

Note that when building a dynamic module, your nginx source version needs to match the version of nginx you’re compiling this for.

Further information about nginx third-party add-ons support are available here: http://wiki.nginx.org/3rdPartyModules

Platform support

The connector supports Linux, macOS and Windows. The platform-specific shared library extension (.so on Linux, .dylib on macOS, .dll on Windows) is detected automatically at compile time.

Runtime library loading

libcoraza is loaded at runtime via dlopen() (or LoadLibrary() on Windows) in each nginx worker process after fork, rather than being linked at build time. This design is required because libcoraza is a Go shared library: when nginx forks worker processes, Go’s runtime threads are lost and the workers would deadlock. By loading libcoraza in init_process (after fork), Go’s runtime initializes fresh in each worker.

As a result, libcoraza.so (or the platform equivalent) must be available in the dynamic linker search path at runtime (e.g. /usr/local/lib), but you do not need to pass -lcoraza to the nginx build. The config script already sets -ldl for you on Linux/macOS.

Usage

coraza for nginx extends your nginx configuration directives. It adds four new directives:

coraza

syntax: coraza on | off

context: http, server, location

default: off

Turns on or off Coraza functionality. Note that this configuration directive is no longer related to the SecRule state. Instead, it now serves solely as an nginx flag to enable or disable the module.

coraza_rules_file

syntax: coraza_rules_file <path to rules file>

context: http, server, location

default: no

Specifies the location of the coraza configuration file, e.g.:

server {
    coraza on;
    location / {
        root /var/www/html;
        coraza_rules_file /etc/my_coraza_rules.conf;
    }
}

coraza_rules

syntax: coraza_rules <coraza rule>

context: http, server, location

default: no

Allows for the direct inclusion of a coraza rule into the nginx configuration. The following example is loading rules from a file and injecting specific configurations per directory/alias:

server {
    coraza on;
    location / {
        root /var/www/html;
        coraza_rules_file /etc/my_coraza_rules.conf;
    }
    location /ops {
        root /var/www/html/opts;
        coraza_rules '
          SecRuleEngine On
          SecDebugLog /tmp/coraza_debug.log
          SecDebugLogLevel 9
          SecRuleRemoveById 10
        ';
    }
}

coraza_transaction_id

syntax: coraza_transaction_id string

context: http, server, location

default: no

Allows to pass transaction ID from nginx instead of generating it in the library. This can be useful for tracing purposes, e.g. consider this configuration:

log_format extended '$remote_addr - $remote_user [$time_local] '
                    '"$request" $status $body_bytes_sent '
                    '"$http_referer" "$http_user_agent" $request_id';

server {
    server_name host1;
    coraza on;
    coraza_transaction_id "host1-$request_id";
    access_log logs/host1-access.log extended;
    error_log logs/host1-error.log;
    location / {
        ...
    }
}

server {
    server_name host2;
    coraza on;
    coraza_transaction_id "host2-$request_id";
    access_log logs/host2-access.log extended;
    error_log logs/host2-error.log;
    location / {
        ...
    }
}

Using a combination of log_format and coraza_transaction_id you will be able to find correlations between access log and error log entries using the same unique identificator.

String can contain variables.

Configuration merging

Rules defined at a higher-level context (http, server) are automatically inherited by all child contexts (server, location). When a child context defines its own rules, the parent’s rules are prepended — the child rules are applied after the parent rules, allowing you to override or extend behavior per location.

For example, the following configuration sets global rules at the http level and overrides body-inspection behaviour in a specific location:

http {
    coraza on;
    coraza_rules '
        SecRuleEngine On
        SecRequestBodyAccess On
        SecRequestBodyLimit 131072
        SecRule REQUEST_BODY "@rx bad" "id:1,phase:2,deny,status:403"
    ';

    server {
        listen 80;

        location / {
            # inherits the http-level rules above
            proxy_pass http://backend;
        }

        location /upload {
            # parent rules are prepended; this directive extends them
            coraza_rules '
                SecRequestBodyLimit 10485760
            ';
            proxy_pass http://backend;
        }
    }
}

Locations that set coraza off will not process requests through the WAF, regardless of rules inherited from parent contexts.

Contributing

As an open source project we invite (and encourage) anyone from the community to contribute to our project. This may take the form of: new functionality, bug fixes, bug reports, beginners user support, and anything else that you are willing to help with. Thank you.

Providing Patches

We prefer to have your patch within the GitHub infrastructure to facilitate our review work, and our QA integration. GitHub provides an excellent documentation on how to perform “Pull Requests”. More information available here: https://help.github.com/articles/using-pull-requests/

Please respect the coding style in use. Pull requests can include various commits, so provide one fix or one functionality per commit. Do not change anything outside the scope of your target work (e.g. coding style in a function that you have passed by).

Don’t know where to start?

Within our code there are various items marked as TODO or FIXME that may need your attention. Check the list of items by performing a grep:

$ cd /path/to/coraza-nginx
$ egrep -Rin "TODO|FIXME" -R *

You may also take a look at recent bug reports and open issues to get an idea of what kind of help we are looking for.

Testing your patch

Along with the manual testing, we strongly recommend that you use the nginx test utility to make sure that your patch does not adversely affect the behavior or performance of nginx.

The nginx tests are available on: http://hg.nginx.org/nginx-tests/

To use those tests, make sure you have the Perl utility prove (part of Perl 5) and proceed with the following commands:

$ wget http://hg.nginx.org/nginx-tests/archive/tip.tar.gz
$ tar xzf tip.tar.gz
$ cp /path/to/coraza-nginx/t/* nginx-tests-*/
$ cd nginx-tests-*
$ export TEST_NGINX_BINARY=/path/to/your/nginx
$ export TEST_NGINX_GLOBALS='load_module "/path/to/ngx_http_coraza_module.so";'
$ prove coraza*.t

If you are facing problems getting your added functionality to pass all the nginx tests, feel free to contact us or the nginx mailing list at: http://nginx.org/en/support.html

Debugging

We respect the nginx debugging schema. By using the configuration option “–with-debug” during the nginx configuration you will also be enabling the connector’s debug messages. Core dumps and crashes are expected to be debugged in the same fashion that is used to debug nginx. For further information, please check the nginx debugging information: http://wiki.nginx.org/Debugging

Reporting Issues

If you are facing a configuration issue or if something is not working as you expect it to be, please use coraza user’s mailing list. Issues on GitHub are also welcome, but we prefer to have users question on the mailing list first, where you can reach an entire community. Also don’t forget to look for an existing issue before opening a new one.

Lastly, If you are planning to open an issue on GitHub, please don’t forget to tell us the version of your libcoraza and the version of the nginx connector you are running.

Security issue

Please do not publicly report any security issue. Instead, contact us at: security@coraza.io to report the issue. Once the problem is fixed we will provide you with credit for the discovery.

Feature Request

We would love to discuss any ideas that you may have for a new feature. Please keep in mind this is a community driven project so be sure to contact the community via the mailing list to get feedback first. Alternatively, feel free to open GitHub issues requesting for new features. Before opening a new issue, please check if there is an existing feature request for the desired functionality.

Packaging

Having our packages in distros on time is something we highly desire. Let us know if there is anything we can do to facilitate your work as a packager.

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