Phase 3 PR 19 — LDAP user identity + Basic256Sha256 security profile. Replaces the anonymous-only endpoint with a configurable security profile and an LDAP-backed UserName token validator. New IUserAuthenticator abstraction in Backend/Security/: LdapUserAuthenticator binds to the configured directory (reuses the pattern from Admin.Security.LdapAuthService without the cross-app dependency — Novell.Directory.Ldap.NETStandard 3.6.0 package ref added to Server alongside the existing OPCFoundation packages) and maps group membership to OPC UA roles via LdapOptions.GroupToRole (case-insensitive). DenyAllUserAuthenticator is the default when Ldap.Enabled=false so UserName token attempts return a clean BadUserAccessDenied rather than hanging on a localhost:3893 bind attempt. OpcUaSecurityProfile enum + LdapOptions nested record on OpcUaServerOptions. Profile=None keeps the PR 17 shape (SecurityPolicies.None + Anonymous token only) so existing integration tests stay green; Profile=Basic256Sha256SignAndEncrypt adds a second ServerSecurityPolicy (Basic256Sha256 + SignAndEncrypt) to the collection and, when Ldap.Enabled=true, adds a UserName token policy scoped to SecurityPolicies.Basic256Sha256 only — passwords must ride an encrypted channel, the stack rejects UserName over None. OtOpcUaServer.OnServerStarted hooks SessionManager.ImpersonateUser: AnonymousIdentityToken passes through; UserNameIdentityToken delegates to IUserAuthenticator.AuthenticateAsync — rejected identities throw ServiceResultException(BadUserAccessDenied); accepted identities get a RoleBasedIdentity that carries the resolved roles through session.Identity so future PRs can gate writes by role. OpcUaApplicationHost + OtOpcUaServer constructors take IUserAuthenticator as a dependency. Program.cs binds the new OpcUaServer:Ldap section from appsettings (Enabled defaults false, GroupToRole parsed as Dictionary<string,string>), registers IUserAuthenticator as LdapUserAuthenticator when enabled or DenyAllUserAuthenticator otherwise. PR 17 integration test updated to pass DenyAllUserAuthenticator so it keeps exercising the anonymous-only path unchanged. Tests — SecurityConfigurationTests (new, 13 cases): DenyAllAuthenticator rejects every credential; LdapAuthenticator rejects blank creds without hitting the server; rejects when Enabled=false; rejects plaintext when both UseTls=false AND AllowInsecureLdap=false (safety guard matching the Admin service); EscapeLdapFilter theory (4 rows: plain passthrough, parens/asterisk/backslash → hex escape) — regression guard against LDAP injection; ExtractOuSegment theory (3 rows: finds ou=, returns null when absent, handles multiple ou segments by returning first); ExtractFirstRdnValue theory (3 rows: strips cn= prefix, handles single-segment DN, returns plain string unchanged when no =). OpcUaServerOptions_default_is_anonymous_only asserts the default posture preserves PR 17 behavior. InternalsVisibleTo('ZB.MOM.WW.OtOpcUa.Server.Tests') added to Server csproj so ExtractOuSegment and siblings are reachable from the tests. Full solution: 0 errors, 180 tests pass (8 Core + 14 Proxy + 24 Configuration + 6 Shared + 91 Galaxy.Host + 19 Server (17 unit + 2 integration) + 18 Admin). Live-LDAP integration test (connect via Basic256Sha256 endpoint with a real user from GLAuth, assert the session.Identity carries the mapped role) is deferred to a follow-up — it requires the GLAuth dev instance to be running at localhost:3893 which is dev-machine-specific, and the test harness for that also needs a fresh client-side certificate provisioned by the live server's trusted store.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Server/OpcUa/OpcUaApplicationHost.cs

@@ -3,6 +3,7 @@ using Opc.Ua;
 using Opc.Ua.Configuration;
 using ZB.MOM.WW.OtOpcUa.Core.Hosting;
 using ZB.MOM.WW.OtOpcUa.Core.OpcUa;
+using ZB.MOM.WW.OtOpcUa.Server.Security;
 
 namespace ZB.MOM.WW.OtOpcUa.Server.OpcUa;
 
@@ -18,6 +19,7 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
 {
     private readonly OpcUaServerOptions _options;
     private readonly DriverHost _driverHost;
+    private readonly IUserAuthenticator _authenticator;
     private readonly ILoggerFactory _loggerFactory;
     private readonly ILogger<OpcUaApplicationHost> _logger;
     private ApplicationInstance? _application;
@@ -25,10 +27,11 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
     private bool _disposed;
 
     public OpcUaApplicationHost(OpcUaServerOptions options, DriverHost driverHost,
-        ILoggerFactory loggerFactory, ILogger<OpcUaApplicationHost> logger)
+        IUserAuthenticator authenticator, ILoggerFactory loggerFactory, ILogger<OpcUaApplicationHost> logger)
     {
         _options = options;
         _driverHost = driverHost;
+        _authenticator = authenticator;
         _loggerFactory = loggerFactory;
         _logger = logger;
     }
@@ -55,7 +58,7 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
             throw new InvalidOperationException(
                 $"OPC UA application certificate could not be validated or created in {_options.PkiStoreRoot}");
 
-        _server = new OtOpcUaServer(_driverHost, _loggerFactory);
+        _server = new OtOpcUaServer(_driverHost, _authenticator, _loggerFactory);
         await _application.Start(_server).ConfigureAwait(false);
 
         _logger.LogInformation("OPC UA server started — endpoint={Endpoint} driverCount={Count}",
@@ -126,22 +129,8 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
             ServerConfiguration = new ServerConfiguration
             {
                 BaseAddresses = new StringCollection { _options.EndpointUrl },
-                SecurityPolicies = new ServerSecurityPolicyCollection
-                {
-                    new ServerSecurityPolicy
-                    {
-                        SecurityMode = MessageSecurityMode.None,
-                        SecurityPolicyUri = SecurityPolicies.None,
-                    },
-                },
-                UserTokenPolicies = new UserTokenPolicyCollection
-                {
-                    new UserTokenPolicy(UserTokenType.Anonymous)
-                    {
-                        PolicyId = "Anonymous",
-                        SecurityPolicyUri = SecurityPolicies.None,
-                    },
-                },
+                SecurityPolicies = BuildSecurityPolicies(),
+                UserTokenPolicies = BuildUserTokenPolicies(),
                 MinRequestThreadCount = 5,
                 MaxRequestThreadCount = 100,
                 MaxQueuedRequestCount = 200,
@@ -164,6 +153,58 @@ public sealed class OpcUaApplicationHost : IAsyncDisposable
         return cfg;
     }
 
+    private ServerSecurityPolicyCollection BuildSecurityPolicies()
+    {
+        var policies = new ServerSecurityPolicyCollection
+        {
+            // Keep the None policy present so legacy clients can discover + browse. Locked-down
+            // deployments remove this by setting Ldap.Enabled=true + dropping None here; left in
+            // for PR 19 so the PR 17 test harness continues to pass unchanged.
+            new ServerSecurityPolicy
+            {
+                SecurityMode = MessageSecurityMode.None,
+                SecurityPolicyUri = SecurityPolicies.None,
+            },
+        };
+
+        if (_options.SecurityProfile == OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt)
+        {
+            policies.Add(new ServerSecurityPolicy
+            {
+                SecurityMode = MessageSecurityMode.SignAndEncrypt,
+                SecurityPolicyUri = SecurityPolicies.Basic256Sha256,
+            });
+        }
+
+        return policies;
+    }
+
+    private UserTokenPolicyCollection BuildUserTokenPolicies()
+    {
+        var tokens = new UserTokenPolicyCollection
+        {
+            new UserTokenPolicy(UserTokenType.Anonymous)
+            {
+                PolicyId = "Anonymous",
+                SecurityPolicyUri = SecurityPolicies.None,
+            },
+        };
+
+        if (_options.SecurityProfile == OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt
+            && _options.Ldap.Enabled)
+        {
+            tokens.Add(new UserTokenPolicy(UserTokenType.UserName)
+            {
+                PolicyId = "UserName",
+                // Passwords must ride an encrypted channel — scope this token to Basic256Sha256
+                // so the stack rejects any attempt to send UserName over the None endpoint.
+                SecurityPolicyUri = SecurityPolicies.Basic256Sha256,
+            });
+        }
+
+        return tokens;
+    }
+
     public async ValueTask DisposeAsync()
     {
         if (_disposed) return;