QR Code Authentication

QR Code authentication is a strategy that allows the user to scan a QR code, generated by the CAS server, using a mobile device and subsequently login after having successfully validated it.

The QR code contains a special identifier embedded within that allows the mobile device to establish a communication channel using web sockets to the CAS server. Once established, the mobile device may collect credentials from the user and submit those to CAS for verification. The return result, expected as a JWT that is generated by CAS, is then passed along to the web socket channel for verification and successful login. Subsequent login attempts can allow for a completely passwordless scenario such that the mobile device can continue to re-use the JWT for authentication attempts, allowing the end user to scan and proceed.

Support is enabled by including the following dependency in the WAR overlay:

1
2
3
4
5

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

1

implementation "org.apereo.cas:cas-server-support-qr-authentication:${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-qr-authentication"
}

1
2
3
4
5
6
7
8
9
10

dependencies {
    /*
    The following platform references should be included automatically and are listed here 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-qr-authentication"
}

Actuator Endpoints

The following endpoints are provided by CAS:

 Remove authorized device using the device id.

 Get registered and authorized devices for the principal.

 Register device using the principal id and device id.


Configuration

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.

  • cas.authn.qr.json.location=

    • The location of the resource. Resources can be URLS, or files found either on the classpath or outside somewhere in the file system.

    In the event the configured resource is a Groovy script, specially if the script set to reload on changes, you may need to adjust the total number of inotify instances. On Linux, you may need to add the following line to /etc/sysctl.conf: fs.inotify.max_user_instances = 256.

    You can check the current value via cat /proc/sys/fs/inotify/max_user_instances.

    org.apereo.cas.configuration.model.support.qr.JsonQRAuthenticationProperties.

    How can I configure this property?

    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.qr.allowed-origins=

    • Configure allowed Origin header values. This check is mostly designed for browser clients. There is nothing preventing other types of client to modify the Origin header value.

    When SockJS is enabled and origins are restricted, transport types that do not allow to check request origin (Iframe based transports) are disabled. As a consequence, IE 6 to 9 are not supported when origins are restricted.

    Each provided allowed origin must start by "http://", "https://" or be "*" (means that all origins are allowed). By default, only same origin requests are allowed (empty list).

    org.apereo.cas.configuration.model.support.qr.QRAuthenticationProperties.

    How can I configure this property?

    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.

    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, 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.

    Web Socket Communication

    The process of connecting to a web socket connection certainly varies for each mobile app framework. At a high level, mobile devices should establish a web socket connection to the CAS server via the /cas/qr-websocket endpoint. The payload must then be sent to the /qr/accept path as a map and must contain a token field that carries the pre-authenticated JWT. The payload header must point to the channel id obtained from the QR code under the header name QR_AUTHENTICATION_CHANNEL_ID as well as the authorized device identifier under QR_AUTHENTICATION_DEVICE_ID.

    The following code snippet demonstrates this process as an example:

    1
2
3
4
5
6
7
8
9

    let socket = new SockJS('https://sso.example.org/cas/qr-websocket');
let stompClient = Stomp.over(socket);
let payload = JSON.stringify({'token': '...'});   
let channelId = "...";      
let deviceId = "...";
stompClient.send("/qr/accept", 
    {'QR_AUTHENTICATION_CHANNEL_ID': channelId, 
     'QR_AUTHENTICATION_DEVICE_ID': deviceId}, 
    payload);

    The following code snippet demonstrates this process for the Android platform based on StompProtocolAndroid:

    1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

    import ua.naiksoftware.stomp.*;
import ua.naiksoftware.stomp.dto.*;

var jwt = "...";
var jsonWebToken = new JSONStringer().object()
  .key("token").value(jwt).endObject();

var channel = "...";      
var deviceId = "...";
var headers = new ArrayList<>();
headers.add(new StompHeader("QR_AUTHENTICATION_CHANNEL_ID", channel));
headers.add(new StompHeader("QR_AUTHENTICATION_DEVICE_ID", deviceId));
headers.add(new StompHeader(StompHeader.DESTINATION, "/qr/accept"));

// wss://10.0.2.2 for ssl and localhost
var client = Stomp.over(Stomp.ConnectionProvider.OKHTTP, 
  "wss://10.0.2.2:8443/cas/qr-websocket/websocket", null, httpClient);

client.connect();
var stompMessage = 
  new StompMessage(StompCommand.SEND, headers, jsonWebToken.toString());
client.send(stompMessage).subscribe();

    Obtaining JWT

    The mobile device should ask for and then submit user credentials to the CAS server using the REST protocol to obtain a JWT. The JWT request must also contain an additional request parameter QR_AUTHENTICATION_DEVICE_ID which indicates the authorized device identifier for the user.

    Once the JWT is received, the device may cache the JWT and establish a session for code reuse later. The JWT should be sent to the CAS server’s web socket channel for validation and login as demonstrated above. The generated JWT is automatically signed and encrypted by CAS and can only be decoded by the CAS server.

    Web Socket Channel

    The QR code contains a special identifier embedded within that allows the mobile device to establish a communication channel using web sockets to the CAS server. The mobile device must be able to scan the QR code to extract the channel id in order to establish a communication route between CAS and the device.

    Mobile Device Authorization

    Registered devices are authorized and accepted by CAS using a dedicated QR device repository, that is able to track and link device identifiers to user ids. Such devices must be registered with CAS using an external registration mechanism or via available CAS-provided APIs.

    By default, all devices can authenticate using the QR code. Different device repository implementations can be supplied using one of the strategies outlined below.

    JSON

    Authorized devices can be managed and tracked inside a single JSON resource, whose path is taught to CAS via settings.

    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.

  • cas.authn.qr.json.location=

    • The location of the resource. Resources can be URLS, or files found either on the classpath or outside somewhere in the file system.

    In the event the configured resource is a Groovy script, specially if the script set to reload on changes, you may need to adjust the total number of inotify instances. On Linux, you may need to add the following line to /etc/sysctl.conf: fs.inotify.max_user_instances = 256.

    You can check the current value via cat /proc/sys/fs/inotify/max_user_instances.

    org.apereo.cas.configuration.model.support.qr.JsonQRAuthenticationProperties.

    How can I configure this property?

    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.

    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.

    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, 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.

    Custom

    Provide the appropriate bean implementation below to define a custom strategy for managing registered devices.

    1
2
3
4

    @Bean
public QRAuthenticationDeviceRepository qrAuthenticationDeviceRepository() {
    return ...
}