Support for Active Directory multidomain forest

In AD forest samAccountName (or uid) may not be unique in the
entire forest and userPrincipalName contains "@" symbol
disallowed in Matrix User Identifiers.

This commit reflects changes in ldap_auth_provider that adds
mxid generation logic for Active Directory.

Signed-off-by: Yuri Konotopov <ykonotopov@gnome.org>

ma1sd.example.yaml

@@ -165,6 +165,8 @@ threepid:
 # ldap:
 #   enabled: true
 #   lookup: true # hash lookup
+#   activeDirectory: false
+#   defaultDomain: ''
 #   connection:
 #     host: 'ldap.domain.tld'
 #     port: 389

src/main/java/io/kamax/mxisd/backend/ldap/LdapBackend.java

@@ -20,6 +20,7 @@
 
 package io.kamax.mxisd.backend.ldap;
 
+import io.kamax.matrix.MatrixID;
 import io.kamax.matrix._MatrixID;
 import io.kamax.mxisd.config.MatrixConfig;
 import io.kamax.mxisd.config.ldap.LdapConfig;
@@ -116,10 +117,16 @@ public abstract class LdapBackend {
 
     public String buildMatrixIdFromUid(String uid) {
         String uidType = getCfg().getAttribute().getUid().getType();
+        String localpart = uid;
+
         if (StringUtils.equals(UID, uidType)) {
-            return "@" + uid + ":" + mxCfg.getDomain();
+            if(getCfg().isActiveDirectory()) {
+                localpart  = new UPN(uid).getMXID();
+            }
+
+            return "@" + localpart + ":" + mxCfg.getDomain();
         } else if (StringUtils.equals(MATRIX_ID, uidType)) {
-            return uid;
+            return localpart;
         } else {
             throw new IllegalArgumentException("Bind type " + uidType + " is not supported");
         }
@@ -128,6 +135,10 @@ public abstract class LdapBackend {
     public String buildUidFromMatrixId(_MatrixID mxId) {
         String uidType = getCfg().getAttribute().getUid().getType();
         if (StringUtils.equals(UID, uidType)) {
+            if(getCfg().isActiveDirectory()) {
+                return new UPN(mxId).getUPN();
+            }
+
             return mxId.getLocalPart();
         } else if (StringUtils.equals(MATRIX_ID, uidType)) {
             return mxId.getId();
@@ -169,4 +180,58 @@ public abstract class LdapBackend {
         return values;
     }
 
+    private class UPN {
+        private String login;
+        private String domain;
+
+        public UPN(String userPrincipalName) {
+            String[] uidParts = userPrincipalName.split("@");
+
+            if (uidParts.length != 2) {
+                throw new IllegalArgumentException(String.format("Wrong userPrincipalName provided: %s", userPrincipalName));
+            }
+
+            this.login = uidParts[0];
+            this.domain = uidParts[1];
+        }
+
+        public UPN(_MatrixID mxid) {
+            String[] idParts = mxid.getLocalPart().split("/");
+
+            if (idParts.length != 2) {
+                if(idParts.length == 1 && !StringUtils.isEmpty(getCfg().getDefaultDomain())) {
+                    throw new IllegalArgumentException(String.format(
+                        "Local part of mxid %s does not contains domain separator and default domain is not configured",
+                        mxid.getLocalPart()
+                    ));
+                }
+
+                this.domain = getCfg().getDefaultDomain();
+            } else {
+                this.domain = idParts[1];
+            }
+
+            this.login = idParts[0];
+        }
+
+        public String getLogin() {
+            return login;
+        }
+
+        public String getDomain() {
+            return domain;
+        }
+
+        public String getMXID() {
+            if(StringUtils.equalsIgnoreCase(getCfg().getDefaultDomain(), this.domain)) {
+                return this.login;
+            }
+
+            return new StringBuilder(this.login).append("/").append(this.domain).toString();
+        }
+
+        public String getUPN() {
+            return new StringBuilder(this.login).append("@").append(this.domain).toString();
+        }
+    }
 }

src/main/java/io/kamax/mxisd/config/ldap/LdapConfig.java

@@ -291,6 +291,9 @@ public abstract class LdapConfig {
     private boolean enabled;
     private String filter;
 
+    private boolean activeDirectory;
+    private String defaultDomain;
+
     private Connection connection = new Connection();
     private Attribute attribute = new Attribute();
     private Auth auth = new Auth();
@@ -316,6 +319,22 @@ public abstract class LdapConfig {
         this.filter = filter;
     }
 
+    public boolean isActiveDirectory() {
+        return activeDirectory;
+    }
+
+    public void setActiveDirectory(boolean activeDirectory) {
+        this.activeDirectory = activeDirectory;
+    }
+
+    public String getDefaultDomain() {
+        return defaultDomain;
+    }
+
+    public void setDefaultDomain(String defaultDomain) {
+        this.defaultDomain = defaultDomain;
+    }
+
     public Connection getConnection() {
         return connection;
     }
@@ -407,6 +426,15 @@ public abstract class LdapConfig {
             throw new ConfigurationException("ldap.identity.token");
         }
 
+        if(isActiveDirectory()) {
+            if(!StringUtils.equals(LdapBackend.UID, uidType)) {
+                throw new IllegalArgumentException(String.format(
+                    "Attribute UID type should be set to %s in Active Directory mode",
+                    LdapBackend.UID
+                ));
+            }
+        }
+
         // Build queries
         attribute.getThreepid().forEach((k, v) -> {
             if (StringUtils.isBlank(identity.getMedium().get(k))) {