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Cross-Site Request Forgery Prevention

Cross-Site Request Forgery (CSRF) is an attack that forces an end user to execute unwanted actions on a web application in which they are currently authenticated.

Quarkus Security provides a CSRF prevention feature which consists of a RESTEasy Reactive server filter which creates and verifies CSRF tokens in application/x-www-form-urlencoded and multipart/form-data forms and a Qute HTML form parameter provider which supports the injection of CSRF tokens in Qute templates.

Creating the Project

First, we need a new project. Create a new project with the following command:

CLI
quarkus create app org.acme:security-csrf-prevention \
    --extension='csrf-reactive' \
    --no-code
cd security-csrf-prevention

To create a Gradle project, add the --gradle or --gradle-kotlin-dsl option.

For more information about how to install the Quarkus CLI and use it, please refer to the Quarkus CLI guide.

Maven
mvn io.quarkus.platform:quarkus-maven-plugin:2.16.0.Final:create \
    -DprojectGroupId=org.acme \
    -DprojectArtifactId=security-csrf-prevention \
    -Dextensions='csrf-reactive' \
    -DnoCode
cd security-csrf-prevention

To create a Gradle project, add the -DbuildTool=gradle or -DbuildTool=gradle-kotlin-dsl option.

This command generates a project which imports the csrf-reactive extension.

If you already have your Quarkus project configured, you can add the csrf-reactive extension to your project by running the following command in your project base directory:

CLI
quarkus extension add 'csrf-reactive'
Maven
./mvnw quarkus:add-extension -Dextensions='csrf-reactive'
Gradle
./gradlew addExtension --extensions='csrf-reactive'

This will add the following to your build file:

pom.xml
<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-csrf-reactive</artifactId>
</dependency>
build.gradle
implementation("io.quarkus:quarkus-csrf-reactive")

Next, let’s add a csrfToken.html Qute template producing an HTML form in the src/main/resources/templates folder:

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>User Name Input</title>
</head>
<body>
    <h1>User Name Input</h1>

    <form action="/service/csrfTokenForm" method="post">
    	<input type="hidden" name="{inject:csrf.parameterName}" value="{inject:csrf.token}" />  (1)

    	<p>Your Name: <input type="text" name="name" /></p>
    	<p><input type="submit" name="submit"/></p>
    </form>
</body>
</html>
1 This expression is used to inject a CSRF token into a hidden form field. This token will be verified by the CSRF filter against a CSRF cookie.

Now let’s create a resource class which returns an HTML form and handles form POST requests:

package io.quarkus.it.csrf;

import javax.inject.Inject;
import javax.ws.rs.Consumes;
import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import io.quarkus.qute.Template;
import io.quarkus.qute.TemplateInstance;

@Path("/service")
public class UserNameResource {

    @Inject
    Template csrfToken; (1)

    @GET
    @Path("/csrfTokenForm")
    @Produces(MediaType.TEXT_HTML)
    public TemplateInstance getCsrfTokenForm() {
        return csrfToken.instance(); (2)
    }

    @POST
    @Path("/csrfTokenForm")
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    @Produces(MediaType.TEXT_PLAIN)
    public String postCsrfTokenForm(@FormParam("name") String userName) {
        return userName; (3)
    }
}
1 Inject the csrfToken.html as a Template.
2 Return the HTML form with a hidden form field containing a CSRF token created by the CSRF filter.
3 Handle the POST form request, this method can only be invoked if the CSRF filter has successfully verified the token.

The form POST request will fail with HTTP status 400 if the filter finds the hidden CSRF form field is missing, the CSRF cookie is missing, or if the CSRF form field and CSRF cookie values do not match.

At this stage no additional configuration is needed - by default the CSRF form field and cookie name will be set to csrf_token, and the filter will verify the token. But you can change these names if you would like:

quarkus.csrf-reactive.form-field-name=csrftoken
quarkus.csrf-reactive.cookie-name=csrftoken

Sign CSRF token

You can get HMAC signatures created for the generated CSRF tokens and have these HMAC values stored as CSRF token cookies if you would like to avoid the risk of the attackers recreating the CSRF cookie token. All you need to do is to configure a token signature secret which must be at least 32 characters long:

quarkus.csrf-reactive.token-signature-key=AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow

Restrict CSRF token verification

Your JAX-RS endpoint may accept not only HTTP POST requests with application/x-www-form-urlencoded or multipart/form-data payloads but also payloads with other media types, either on the same or different URL paths, and therefore you would like to avoid verifying the CSRF token in such cases, for example:

package io.quarkus.it.csrf;

import javax.inject.Inject;
import javax.ws.rs.BadRequestException;
import javax.ws.rs.Consumes;
import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import io.quarkus.qute.Template;
import io.quarkus.qute.TemplateInstance;

@Path("/service")
public class UserNameResource {

    @Inject
    Template csrfToken;

    @GET
    @Path("/user")
    @Produces(MediaType.TEXT_HTML)
    public TemplateInstance getCsrfTokenForm() {
        return csrfToken.instance();
    }

    (1)
    @POST
    @Path("/user")
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    @Produces(MediaType.TEXT_PLAIN)
    public String postCsrfTokenForm(@FormParam("name") String userName) {
        return userName;
    }

    (2)
    @POST
    @Path("/user")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.TEXT_PLAIN)
    public String postJson(User user) {
        return user.name;
    }

    (3)
    @POST
    @Path("/users")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.TEXT_PLAIN)
    public String postJson(User user) {
        return user.name;
    }

    public static class User {
        private String name;
        public String getName() {
            return this.name;
        }
        public void setName(String name) {
            this.name = name;
        }
    }
}
1 POST form request to /user, CSRF token verification is enforced by the CSRF filter
2 POST json request to /user, CSRF token verification is not needed
3 POST json request to /users, CSRF token verification is not needed

As you can see a CSRF token verification will be required at the /service/user path accepting the application/x-www-form-urlencoded payload, but User JSON representation posted to both /service/user and /service/users method will have no CSRF token and therefore the token verification has to be skipped in these cases by restricting it to the specific /service/user request path but also allowing not only application/x-www-form-urlencoded on this path:

# Verify CSRF token only for the `/service/user` path, ignore other paths such as `/service/users`
quarkus.csrf-reactive.create-token-path=/service/user

# If `/service/user` path accepts not only `application/x-www-form-urlencoded` payloads but also other ones such as JSON then allow them
quarkus.csrf-reactive.require-form-url-encoded=false

Verify CSRF token in the application code

If you prefer to compare the CSRF form field and cookie values in the application code then you can do it as follows:

package io.quarkus.it.csrf;

import javax.inject.Inject;
import javax.ws.rs.BadRequestException;
import javax.ws.rs.Consumes;
import javax.ws.rs.CookieParam;
import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import io.quarkus.qute.Template;
import io.quarkus.qute.TemplateInstance;

@Path("/service")
public class UserNameResource {

    @Inject
    Template csrfToken;

    @GET
    @Path("/csrfTokenForm")
    @Produces(MediaType.TEXT_HTML)
    public TemplateInstance getCsrfTokenForm() {
        return csrfToken.instance();
    }

    @POST
    @Path("/csrfTokenForm")
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    @Produces(MediaType.TEXT_PLAIN)
    public String postCsrfTokenForm(@CookieParam("csrf-token") csrfCookie, @FormParam("csrf-token") String formCsrfToken, @FormParam("name") String userName) {
        if (!csrfCookie.getValue().equals(formCsrfToken)) { (1)
            throw new BadRequestException();
        }
        return userName;
    }
}
1 Compare the CSRF form field and cookie values and fail with HTTP status 400 if they don’t match.

Also disable the token verification in the filter:

quarkus.csrf-reactive.verify-token=false

Configuration Reference

Configuration property fixed at build time - All other configuration properties are overridable at runtime

Configuration property

Type

Default

If filter is enabled.

Environment variable: QUARKUS_CSRF_REACTIVE_ENABLED

boolean

true

Form field name which keeps a CSRF token.

Environment variable: QUARKUS_CSRF_REACTIVE_FORM_FIELD_NAME

string

csrf-token

CSRF cookie name.

Environment variable: QUARKUS_CSRF_REACTIVE_COOKIE_NAME

string

csrf-token

CSRF cookie max age.

Environment variable: QUARKUS_CSRF_REACTIVE_COOKIE_MAX_AGE

Duration

10M

CSRF cookie path.

Environment variable: QUARKUS_CSRF_REACTIVE_COOKIE_PATH

string

/

CSRF cookie domain.

Environment variable: QUARKUS_CSRF_REACTIVE_COOKIE_DOMAIN

string

If enabled the CSRF cookie will have its 'secure' parameter set to 'true' when HTTP is used. It may be necessary when running behind an SSL terminating reverse proxy. The cookie will always be secure if HTTPS is used even if this property is set to false.

Environment variable: QUARKUS_CSRF_REACTIVE_COOKIE_FORCE_SECURE

boolean

false

Create CSRF token only if the HTTP GET relative request path matches one of the paths configured with this property. Use a comma to separate multiple path values.

Environment variable: QUARKUS_CSRF_REACTIVE_CREATE_TOKEN_PATH

list of string

Random CSRF token size in bytes.

Environment variable: QUARKUS_CSRF_REACTIVE_TOKEN_SIZE

int

16

CSRF token HMAC signature key, if this key is set then it must be at least 32 characters long.

Environment variable: QUARKUS_CSRF_REACTIVE_TOKEN_SIGNATURE_KEY

string

Verify CSRF token in the CSRF filter. If this property is enabled then the input stream will be read and cached by the CSRF filter to verify the token. If you prefer then you can disable this property and compare CSRF form and cookie parameters in the application code using JAX-RS javax.ws.rs.FormParam which refers to the form-field-name form property and javax.ws.rs.CookieParam which refers to the CsrfReactiveConfig#cookieName cookie. Note that even if the CSRF token verification in the CSRF filter is disabled, the filter will still perform checks to ensure the token is available, has the correct token-size in bytes and that the Content-Type HTTP header is either 'application/x-www-form-urlencoded' or 'multipart/form-data'.

Environment variable: QUARKUS_CSRF_REACTIVE_VERIFY_TOKEN

boolean

true

Require that only 'application/x-www-form-urlencoded' or 'multipart/form-data' body is accepted for the token verification to proceed. Disable this property for the CSRF filter to avoid verifying the token for POST requests with other content types. This property is only effective if verify-token property is enabled.

Environment variable: QUARKUS_CSRF_REACTIVE_REQUIRE_FORM_URL_ENCODED

boolean

true

About the Duration format

The format for durations uses the standard java.time.Duration format. You can learn more about it in the Duration#parse() javadoc.

You can also provide duration values starting with a number. In this case, if the value consists only of a number, the converter treats the value as seconds. Otherwise, PT is implicitly prepended to the value to obtain a standard java.time.Duration format.