Simple Multifactor Authentication - Rate Limiting

CAS is able to support rate-limiting for token requests based on the token-bucket algorithm, via the Bucket4j project. This means that token requests that reach a certain configurable capacity within a time window may either be blocked or throttled to slow down. This is done to protect the system from overloading, allowing you to introduce a scenario to allow CAS 120 token requests per minute with a refill rate of 10 requests per second that would continually increase in the capacity bucket. Please note that the bucket allocation strategy is specific to the client IP address.

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

_{The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.}

_{The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This
flag indicates that the presence of the setting
is not immediately necessary in the end-user CAS configuration, because a default value is assigned or
the activation of the feature is not conditionally controlled by the setting value. You should only include this field in your
configuration if you need to modify the default value.}

cas.authn.mfa.simple.bucket4j.bandwidth[0].capacity=120

Number of tokens/requests that can be used within the time window.

org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

: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.

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.bandwidth[0].capacity=120

This is the most common form of property configuration that is recognized by CAS, regardless of the actual property source, which might in fact be managed separately outside the CAS environment, by another system or cloud framework.

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          bandwidth[0]: 
            capacity: "120"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.bandwidth[0].capacity="120" -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory. Note the placement of the system property which must be specified before the CAS web application is launched.

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_BANDWIDTH[0]_CAPACITY="120"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.bandwidth[0].capacity="120"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.authn.mfa.simple.bucket4j.bandwidth[0].duration=PT60S

Time window in which capacity can be allowed.

This settings supports the java.time.Duration syntax ^[?].

org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

:information_source: Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.bandwidth[0].duration=PT60S

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          bandwidth[0]: 
            duration: "PT60S"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.bandwidth[0].duration="PT60S" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_BANDWIDTH[0]_DURATION="PT60S"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.bandwidth[0].duration="PT60S"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.authn.mfa.simple.bucket4j.bandwidth[0].initial-tokens=

By default initial size of bucket equals to capacity. But sometimes, you may want to have lesser initial size, for example for case of cold start in order to prevent denial of service.

org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

:information_source: Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.bandwidth[0].initial-tokens=...

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          bandwidth[0]: 
            initial-tokens: "..."

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.bandwidth[0].initial-tokens="..." -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_BANDWIDTH[0]_INITIAL_TOKENS="..."

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.bandwidth[0].initial-tokens="..."

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-count=10

The number of tokens that should be used to refill the bucket given the specified refill duration.

org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

:information_source: Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-count=10

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          bandwidth[0]: 
            refill-count: "10"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.bandwidth[0].refill-count="10" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_BANDWIDTH[0]_REFILL_COUNT="10"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-count="10"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-duration=PT30S

Duration to use to refill the bucket.

This settings supports the java.time.Duration syntax ^[?].

org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

:information_source: Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-duration=PT30S

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          bandwidth[0]: 
            refill-duration: "PT30S"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.bandwidth[0].refill-duration="PT30S" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_BANDWIDTH[0]_REFILL_DURATION="PT30S"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-duration="PT30S"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-strategy=GREEDY

Describes how the bucket should be refilled. Specifies the speed of tokens regeneration. Available values are as follows:

GREEDY: This type of refill regenerates tokens in a greedy manner; it tries to add the tokens to bucket as soon as possible. For example refill "10 tokens per 1 second" adds 1 token per each 100 millisecond; in other words refill will not wait 1 second to regenerate 10 tokens.
INTERVALLY: This type of refill regenerates tokens in intervally manner. "Intervally" in opposite to "greedy" will wait until whole period would be elapsed before regenerating tokens.

org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

:information_source: Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-strategy=GREEDY

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          bandwidth[0]: 
            refill-strategy: "GREEDY"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.bandwidth[0].refill-strategy="GREEDY" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_BANDWIDTH[0]_REFILL_STRATEGY="GREEDY"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-strategy="GREEDY"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.authn.mfa.simple.bucket4j.bandwidth=

Describe the available bandwidth and the overall limitations. Multiple bandwidths allow for different policies per unit of measure. (i.e. allows 1000 tokens per 1 minute, but not often then 50 tokens per 1 second).

org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationBucket4jProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

:information_source: Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.bandwidth=...

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          bandwidth: "..."

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.bandwidth="..." -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_BANDWIDTH="..."

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.bandwidth="..."

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.authn.mfa.simple.bucket4j.blocking=true

Whether the request should block until capacity becomes available. Consume a token from the token bucket. If a token is not available this will block until the refill adds one to the bucket.

org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationBucket4jProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

:information_source: Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.blocking=true

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          blocking: "true"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.blocking="true" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_BLOCKING="true"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.blocking="true"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.authn.mfa.simple.bucket4j.enabled=true

Decide whether bucket4j functionality should be enabled.

org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationBucket4jProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

:information_source: Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.mfa.simple.bucket4j.enabled=true

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    mfa: 
      simple: 
        bucket4j: 
          enabled: "true"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.mfa.simple.bucket4j.enabled="true" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_MFA_SIMPLE_BUCKET4J_ENABLED="true"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.mfa.simple.bucket4j.enabled="true"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

# Number of tokens/requests that can be used within the time window.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].capacity=120

# Time window in which capacity can be allowed.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].duration=PT60S

# By default initial size of bucket equals to capacity.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].initial-tokens=

# The number of tokens that should be used to refill the bucket given the specified refill duration.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-count=10

# Duration to use to refill the bucket.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-duration=PT30S

# Describes how the bucket should be refilled.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-strategy=GREEDY

# Describe the available bandwidth and the overall limitations.
# cas.authn.mfa.simple.bucket4j.bandwidth=

# Whether the request should block until capacity becomes available.
# cas.authn.mfa.simple.bucket4j.blocking=true

# Decide whether bucket4j functionality should be enabled.
# cas.authn.mfa.simple.bucket4j.enabled=true

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.

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, specially if defined CAS settings cannot be recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. 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.