GUACAMOLE-793: Add abstract mechanism for parsing CAS group names.

extensions/guacamole-auth-cas/pom.xml

@@ -183,6 +183,26 @@
             <scope>provided</scope>
         </dependency>
 
+        <!-- JUnit -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <version>5.6.0</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <version>5.6.0</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>5.6.0</version>
+            <scope>test</scope>
+        </dependency>
+
     </dependencies>
 
 </project>

extensions/guacamole-auth-cas/src/main/java/org/apache/guacamole/auth/cas/group/GroupFormat.java

@@ -0,0 +1,41 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.guacamole.auth.cas.group;
+
+import org.apache.guacamole.properties.EnumGuacamoleProperty.PropertyValue;
+
+/**
+ * Possible formats of group names received from CAS.
+ */
+public enum GroupFormat {
+
+    /**
+     * Simple, plain-text group names.
+     */
+    @PropertyValue("plain")
+    PLAIN,
+
+    /**
+     * Group names formatted as LDAP DNs.
+     */
+    @PropertyValue("ldap")
+    LDAP
+
+}

extensions/guacamole-auth-cas/src/main/java/org/apache/guacamole/auth/cas/group/GroupParser.java

@@ -0,0 +1,44 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.guacamole.auth.cas.group;
+
+/**
+ * Parser which converts the group names returned by CAS into names usable by
+ * Guacamole. The format of a CAS group name may vary by the underlying
+ * authentication backend. For example, a CAS deployment backed by LDAP may
+ * provide group names as LDAP DNs, which must be transformed into normal group
+ * names to be usable within Guacamole.
+ *
+ * @see LDAPGroupParser
+ */
+public interface GroupParser {
+
+    /**
+     * Parses the given CAS group name into a group name usable by Guacamole.
+     *
+     * @param casGroup
+     *     The group name retrieved from CAS.
+     *
+     * @return
+     *     A group name usable by Guacamole, or null if the group is not valid.
+     */
+    String parse(String casGroup);
+
+}

extensions/guacamole-auth-cas/src/main/java/org/apache/guacamole/auth/cas/group/LDAPGroupParser.java

@@ -0,0 +1,106 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.guacamole.auth.cas.group;
+
+import javax.naming.InvalidNameException;
+import javax.naming.ldap.LdapName;
+import javax.naming.ldap.Rdn;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * GroupParser that converts group names from LDAP DNs into normal group names,
+ * using the last (leftmost) attribute of the DN as the name. Groups may
+ * optionally be restricted to only those beneath a specific base DN, or only
+ * those using a specific attribute as their last (leftmost) attribute.
+ */
+public class LDAPGroupParser implements GroupParser {
+
+    /**
+     * Logger for this class.
+     */
+    private static final Logger logger = LoggerFactory.getLogger(LDAPGroupParser.class);
+
+    /**
+     * The LDAP attribute to require for all accepted group names. If null, any
+     * LDAP attribute will be allowed.
+     */
+    private final String nameAttribute;
+
+    /**
+     * The base DN to require for all accepted group names. If null, ancestor
+     * tree structure will not be considered in accepting/rejecting a group.
+     */
+    private final LdapName baseDn;
+
+    /**
+     * Creates a new LDAPGroupParser which applies the given restrictions on
+     * any provided group names.
+     *
+     * @param nameAttribute
+     *     The LDAP attribute to require for all accepted group names. This
+     *     restriction applies to the last (leftmost) attribute only, which is
+     *     always used to determine the name of the group. If null, any LDAP
+     *     attribute will be allowed in the last (leftmost) position.
+     *
+     * @param baseDn
+     *     The base DN to require for all accepted group names. If null,
+     *     ancestor tree structure will not be considered in
+     *     accepting/rejecting a group.
+     */
+    public LDAPGroupParser(String nameAttribute, LdapName baseDn) {
+        this.nameAttribute = nameAttribute;
+        this.baseDn = baseDn;
+    }
+
+    @Override
+    public String parse(String casGroup) {
+
+        // Reject null/empty group names
+        if (casGroup == null || casGroup.isEmpty())
+            return null;
+
+        // Parse group as an LDAP DN
+        LdapName group;
+        try {
+            group = new LdapName(casGroup);
+        }
+        catch (InvalidNameException e) {
+            logger.debug("CAS group \"{}\" has been rejected as it is not a "
+                    + "valid LDAP DN.", casGroup, e);
+            return null;
+        }
+
+        // Reject any group that is not beneath the base DN
+        if (baseDn != null && !group.startsWith(baseDn))
+            return null;
+
+        // If a specific name attribute is defined, restrict to groups that
+        // use that attribute to distinguish themselves
+        Rdn last = group.getRdn(group.size() - 1);
+        if (nameAttribute != null && !nameAttribute.equalsIgnoreCase(last.getType()))
+            return null;
+
+        // The group name is the string value of the final attribute in the DN
+        return last.getValue().toString();
+
+    }
+
+}

extensions/guacamole-auth-cas/src/main/java/org/apache/guacamole/auth/cas/group/PlainGroupParser.java

@@ -0,0 +1,32 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.guacamole.auth.cas.group;
+
+/**
+ * GroupParser which simply passes through all CAS group names untouched.
+ */
+public class PlainGroupParser implements GroupParser {
+
+    @Override
+    public String parse(String casGroup) {
+        return casGroup;
+    }
+
+}