Digest Authentication
Digest authentication is one of the agreed-upon methods CAS can use to negotiate credentials with a user’s web browser. This can be used to confirm the identity of a user before sending sensitive information. It applies a hash function to the username and password before sending them over the network. Technically, digest authentication is an application of MD5 cryptographic hashing with usage of nonce values to prevent replay attacks. It uses the HTTP protocol.
This feature is deprecated and is scheduled to be removed in the future.
Support is enabled by including the following dependency in the WAR overlay:
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<dependency>
<groupId>org.apereo.cas</groupId>
<artifactId>cas-server-support-digest-authentication</artifactId>
<version>${cas.version}</version>
</dependency>
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implementation "org.apereo.cas:cas-server-support-digest-authentication:${project.'cas.version'}"
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dependencyManagement {
imports {
mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
}
}
dependencies {
implementation "org.apereo.cas:cas-server-support-digest-authentication"
}
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dependencies {
/*
The following platform references should be included automatically and are listed here for reference only.
implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
*/
implementation "org.apereo.cas:cas-server-support-digest-authentication"
}
For additional information on how digest authentication works, please review this guide.
Configuration
The following settings and properties are available from the CAS configuration catalog:
cas.authn.digest.authentication-method=auth
Authentication method used when creating digest header.
Deprecation status is |
cas.authn.digest.name=
Name of the authentication handler.
Deprecation status is |
cas.authn.digest.order=
Order of the authentication handler in the chain.
Deprecation status is |
cas.authn.digest.realm=CAS
The digest realm to use.
Deprecation status is |
cas.authn.digest.users=
Static/stub list of username and passwords to accept if no other account store is defined.
Deprecation status is |
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.
Credential Management
By default, CAS attempts to cross-check computed hash values against what the client reports in the authentication request. In order for this to succeed, CAS will need access to the data store where MD5 representations of credentials are kept. The store needs to keep the hash value at a minimum of course.
By default, CAS uses its properties file to house the hashed credentials. Real production-level deployments of this module will need to provide their own data store that provides a collection of hashed values as authenticating accounts.
Client Requests
The following snippets demonstrate how a given Java client may use CAS digest authentication, via Apache’s HttpClient library:
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var target = new HttpHost("localhost", 8080, "http");
var credsProvider = new BasicCredentialsProvider();
credsProvider.setCredentials(
new AuthScope(target.getHostName(), target.getPort()),
new UsernamePasswordCredentials("casuser", "Mellon"));
var httpclient = HttpClients.custom()
.setDefaultCredentialsProvider(credsProvider)
.build();
try {
var httpget = new HttpGet("http://localhost:8080/cas/login");
// Create AuthCache instance
var authCache = new BasicAuthCache();
// Generate DIGEST scheme object, initialize it and add it to the local auth cache
var digestAuth = new DigestScheme();
digestAuth.overrideParamter("realm", "CAS");
authCache.put(target, digestAuth);
// Add AuthCache to the execution context
var localContext = HttpClientContext.create();
localContext.setAuthCache(authCache);
System.out.println("Executing request " + httpget.getRequestLine() + " to " + target);
try (var response = httpclient.execute(target, httpget, localContext)) {
System.out.println(response.getStatusLine());
System.out.println(EntityUtils.toString(response.getEntity()));
}
} finally {
httpclient.close();
}