APEREO CASDocumentation

Enterprise Authentication for All Earthlings and Beyond

Identity, Single Sign-On and Access Management
View on GitHub

Google reCAPTCHA

reCAPTCHA is a Google service that protects your CAS deployment from spam and abuse. It uses advanced risk analysis techniques to tell humans and bots apart. CAS supports the reCAPTCHA API v2 and v3.

Support is enabled by including the following module in the WAR Overlay:

Show in CAS Initializr Generate CAS Server WAR Overlay 


1
2
3
4
5



<dependency>
    <groupId>org.apereo.cas</groupId>
    <artifactId>cas-server-support-captcha</artifactId>
    <version>${cas.version}</version>
</dependency>





1



implementation "org.apereo.cas:cas-server-support-captcha:${project.'cas.version'}"





1
2
3
4
5
6
7
8
9



dependencyManagement {
    imports {
        mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
    }
}

dependencies {
    implementation "org.apereo.cas:cas-server-support-captcha"
}





1
2
3
4
5
6
7
8
9
10



dependencies {
    /*
        The following platform references are included automatically and are listed for reference only.

        implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
        implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
        
    */
    implementation "org.apereo.cas:cas-server-support-captcha"
}

The following settings and properties are available from the CAS configuration catalog:

cas.google-recaptcha.enabledWhether reCAPTCHA should be enabled.
true
Required

Whether reCAPTCHA should be enabled.

Type
Boolean
Default
true
Defined by
GoogleRecaptchaProperties
cas.google-recaptcha.scoreGoogle reCAPTCHA v3 returns a score (1.0 is very likely a good interaction, 0.0 is very likely a bot). reCAPTCHA learns by seeing real traffic on your site.
0.5
Required

Google reCAPTCHA v3 returns a score (1.0 is very likely a good interaction, 0.0 is very likely a bot). reCAPTCHA learns by seeing real traffic on your site. For this reason, scores in a staging environment or soon after implementing may differ from production. As reCAPTCHA v3 doesn't ever interrupt the user flow, you can first run reCAPTCHA without taking action and then decide on thresholds by looking at your traffic in the admin console. By default, you can use a threshold of 0.5.

Type
Double
Default
0.5
Defined by
GoogleRecaptchaProperties
cas.google-recaptcha.secretThe reCAPTCHA site secret.
no default
Required

The reCAPTCHA site secret.

Type
String
Default
none
Defined by
GoogleRecaptchaProperties
cas.google-recaptcha.site-keyThe reCAPTCHA site key.
no default
RequiredSpEL

The reCAPTCHA site key.

Type
String
Default
none
Defined by
GoogleRecaptchaProperties
Supports
Spring Expression Language
cas.google-recaptcha.activate-for-ip-address-patternA regular expression pattern to indicate that captcha should be activated when the remote IP address matches this pattern, and otherwise skipped and disabled.
no default
Regex

A regular expression pattern to indicate that captcha should be activated when the remote IP address matches this pattern, and otherwise skipped and disabled.

Type
String
Default
none
Defined by
GoogleRecaptchaProperties
cas.google-recaptcha.headersHeaders, defined as a Map , to include in the request when making the verification call to the recaptcha API.
no default

Headers, defined as a Map, to include in the request when making the verification call to the recaptcha API.

Type
Map<String,String>
Default
none
Defined by
GoogleRecaptchaProperties
cas.google-recaptcha.invisibleWhether google reCAPTCHA invisible should be enabled.
false

Whether google reCAPTCHA invisible should be enabled.

Type
Boolean
Default
false
Defined by
GoogleRecaptchaProperties
cas.google-recaptcha.positionThe google reCAPTCHA badge position (only if invisible is enabled).
bottomright
The google reCAPTCHA badge position (only if invisible is enabled). Accepted values are:
  • bottomright: bottom right corner, default value.
  • bottomleft: bottom left corner
  • inline: allows one to control the CSS.
Type
String
Default
bottomright
Defined by
GoogleRecaptchaProperties
cas.google-recaptcha.verify-urlThe reCAPTCHA endpoint for verification of the reCAPTCHA response.
https://www.google.com/recaptcha/api/siteverify
The reCAPTCHA endpoint for verification of the reCAPTCHA response. The endpoint is specific to the reCAPTCHA provider:
  • For Google reCAPTCHA, the endpoint is https://www.google.com/recaptcha/api/siteverify.
  • For hCaptcha, the endpoint is https://hcaptcha.com/siteverify.
  • For Turnstile, the endpoint is https://challenges.cloudflare.com/turnstile/v0/siteverify.
Type
String
Default
https://www.google.com/recaptcha/api/siteverify
Defined by
GoogleRecaptchaProperties
cas.google-recaptcha.versionIndicate the version of the recaptcha api.
GOOGLE_RECAPTCHA_V2
Indicate the version of the recaptcha api. Available values are as follows:
  • GOOGLE_RECAPTCHA_V2: V2 version of the recaptcha API.
  • GOOGLE_RECAPTCHA_V3: V3 version of the recaptcha API.
  • HCAPTCHA: hCaptcha is an alternative to reCAPTCHA that requires website visitors to label images as part of its business model. The provider is more focused on manual image recognition challenges. It is a image classification task based CAPTCHA provider employing visual challenges like identifying objects.
  • TURNSTILE: Offers a CAPTCHA alternative by Cloudflare that prioritizes user experience and privacy. Turnstile delivers frustration-free, CAPTCHA-free web experiences to website visitors - with just a simple snippet of free code. Moreover, Turnstile stops abuse and confirms visitors are real without the data privacy concerns or awful user experience of CAPTCHAs.
  • FRIENDLY_CAPTCHA: Friendly captcha is a European alternative, accessible and GDPR compliant.
Type
GoogleRecaptchaProperties.RecaptchaVersions
Default
GOOGLE_RECAPTCHA_V2
Defined by
GoogleRecaptchaProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Notes on configuration

Configuration Metadata

The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

Be Selective

This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

YAGNI

Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

Naming Convention

Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc.

:information_source: Note

When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value. The only possible exception to this rule is when naming actuator endpoints; The name of the actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.

Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

Validation

Configuration properties are automatically validated on CAS startup to report issues with configuration binding, especially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

Indexed Settings

CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

:information_source: Use Case

Note that this particular integration applies to login and authentication attempts. Several other CAS modules do also support reCAPTCHA integrations for their own special flows, especially when it comes to reCAPTCHA activation strategies, separate from what is documented and available here.

Internet Explorer

Remember to disable Internet Explorer’s “Compatibility View” mode. reCAPTCHA may not render correctly when that mode is turned on.

reCAPTCHA Per Service

Certain reCAPTCHA settings can be defined on a per-service basis via dedicated properties:



1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17



{
  "@class" : "org.apereo.cas.services.CasRegisteredService",
  "serviceId" : "^https://.+",
  "name" : "sample service",
  "id" : 100,
  "properties" : {
    "@class" : "java.util.HashMap",
    "captchaEnabled" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
      "values" : [ "java.util.HashSet", [ "false" ] ]
    },
    "captchaIPAddressPattern" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
      "values" : [ "java.util.HashSet", [ "pattern1", "pattern2" ] ]
    }
  }
}

The following properties are available and recognized by CAS for various modules and features:

Name Default Value Type Group
captchaIPAddressPattern true SET RECAPTCHA
captchaEnabled true BOOLEAN RECAPTCHA

Activation Strategy

reCAPTCHA activation strategy is generally controlled via CAS settings. It is also possible to design and inject your own activation strategy into CAS using the following @Bean that would be registered in a @AutoConfiguration class:



1
2
3
4



@Bean
public CaptchaActivationStrategy captchaActivationStrategy() {
    return new MyCaptchaActivationStrategy();
}

Your configuration class needs to be registered with CAS. See this guide for better details.