UA-.NETStandard/docs/RoleBasedUserManagement.md

Role-Based Security (OPC UA Part 18)

Overview

The OPC UA .NET Standard Stack implements the role-based security model from OPC UA Part 18: Role-Based Security (v1.05.06) together with the well-known roles defined in OPC UA Part 3 4.9.2.

The nine well-known roles are pre-registered at server start:

Role	NodeId	Reserved?	Default identities
Anonymous	i=15644	Yes	Anonymous, AuthenticatedUser
AuthenticatedUser	i=15656	Yes	AuthenticatedUser
TrustedApplication	i=18625	Yes	TrustedApplication
Observer	i=15668	No	(empty)
Operator	i=15680	No	(empty)
Engineer	i=16036	No	(empty)
Supervisor	i=15692	No	(empty)
ConfigureAdmin	i=15716	No	(empty)
SecurityAdmin	i=15704	No	(empty)

Reserved roles cannot be modified or removed per Part 18 4.3 - any attempt to call AddIdentity, AddApplication, AddEndpoint, RemoveIdentity, RemoveApplication, RemoveEndpoint, or RemoveRole on them returns Bad_RequestNotAllowed.

See src/Opc.Ua.Server/RoleBasedUserManagement/ for the source.

Server side

IRoleManager

The IRoleManager interface (Opc.Ua.Server.IRoleManager) is the server-side extensibility surface. The default implementation Opc.Ua.Server.RoleManager is fully in-memory; integrators that need persistence implement IRoleManager directly and inject the instance via IServerInternal.SetRoleManager before the server starts.

Every mutator returns a ServiceResult that mirrors the spec-defined status codes:

• AddIdentity (4.4.5) - Good or Bad_InvalidArgument / Bad_AlreadyExists / Bad_RequestNotAllowed / Bad_NodeIdUnknown.
• RemoveIdentity (4.4.6) - Good or Bad_NotFound / Bad_RequestNotAllowed / Bad_NodeIdUnknown.
• AddApplication (4.4.7) - Good or Bad_InvalidArgument / Bad_AlreadyExists / Bad_RequestNotAllowed / Bad_NodeIdUnknown.
• RemoveApplication (4.4.8) - Good or Bad_NotFound / Bad_RequestNotAllowed / Bad_NodeIdUnknown.
• AddEndpoint (4.4.9) - Good or Bad_InvalidArgument / Bad_AlreadyExists / Bad_RequestNotAllowed / Bad_NodeIdUnknown.
• RemoveEndpoint (4.4.10) - Good or Bad_NotFound / Bad_RequestNotAllowed / Bad_NodeIdUnknown.
• AddRole (4.2.2) - Good or Bad_InvalidArgument / Bad_AlreadyExists.
• RemoveRole (4.2.3) - Good or Bad_NodeIdUnknown / Bad_RequestNotAllowed.
• SetApplicationsExclude / SetEndpointsExclude / SetCustomConfiguration - Good or Bad_RequestNotAllowed / Bad_NodeIdUnknown.

IdentityMappingRuleType is validated per Part 18 4.4.3 before storage:

• Anonymous, AuthenticatedUser, TrustedApplication - criteria must be empty.
• Thumbprint - upper-case hexadecimal, no spaces.
• X509Subject - Name=Value(/Name=Value)* grammar with names from Part 18 Table 10.

EndpointType comparisons in identity resolution honour Part 18 4.4.2: fields set to their default value on the rule side act as wildcards. A rule may therefore constrain any subset of endpoint fields by assigning non-default values to those fields. For example, this rule applies to every endpoint URL that uses SignAndEncrypt:

IRoleManager roles = server.CurrentInstance.RoleManager;

roles.AddEndpoint(
    ObjectIds.WellKnownRole_Engineer,
    new EndpointType
    {
        SecurityMode = MessageSecurityMode.SignAndEncrypt
    });

At least one field must be non-default; AddEndpoint returns Bad_InvalidArgument for a null or completely default EndpointType.

Identity-claim criteria support:

• IdentityCriteriaType.GroupId probes the returned IUserIdentity for Opc.Ua.Identity.IIdentityClaims (see Identity Providers) and matches IIdentityClaims.Groups.
• IdentityCriteriaType.Role matches roles asserted inside the access token via IIdentityClaims.Roles, optionally prefixed by the issuer URI as iss/roleName, per Part 18 4.4.4.

Authoring an identity-mapping rule with claims

JWT authenticators that return an identity implementing IIdentityClaims allow Part 18 rules to match Entra-style claims. The in-box RoleManager treats entries in a role's Identities collection as OR criteria, per the standard IdentityMappingRuleType[] shape. Add one entry for each accepted claim value:

IRoleManager roles = server.CurrentInstance.RoleManager;

roles.AddIdentity(
    ObjectIds.WellKnownRole_Engineer,
    new IdentityMappingRuleType
    {
        CriteriaType = IdentityCriteriaType.Role,
        Criteria = "https://login.microsoftonline.com/{tenant}/v2.0/OpcUa.Engineer"
    });

roles.AddIdentity(
    ObjectIds.WellKnownRole_Engineer,
    new IdentityMappingRuleType
    {
        CriteriaType = IdentityCriteriaType.GroupId,
        Criteria = "00000000-1111-2222-3333-444444444444"
    });

The first rule matches an access-token role claim OpcUa.Engineer only when IIdentityClaims.Issuer is the Entra issuer. The second matches a groups claim containing the Entra group object id. If your policy must require both a role and a group simultaneously, implement a custom IRoleManager (or a custom authorization layer) because the shipped RoleConfigurationOptions DTO does not define an AND-rule collection.

RoleConfigurationChanged event

IRoleManager.RoleConfigurationChanged fires after every successful mutation with the role NodeId and a RoleConfigurationChangeKind. Integrators can subscribe to:

• materialize dynamic-role address-space nodes when RoleAdded fires (the default in-memory RoleManager does not create address-space nodes for AddRole - the well-known roles are already in the standard nodeset);
• re-evaluate active sessions per Part 18 4.4.1 ("If the configuration of a Role is changed, the Role assignment to active Session shall be re-evaluated and applied");
• emit audit events beyond the spec-defined RoleMappingRuleChangedAuditEvent.

Typed-proxy address-space binding

RoleStateBinding.Bind(diagnosticsNodeManager, roleManager, auditServer) uses the source-generated typed proxies (RoleSetState, RoleState, AddIdentityMethodState, AddRoleMethodState, ...). Each typed OnCallAsync delegate:

1. Enforces RoleAuthorizationGate.CheckAdmin (SecurityAdmin role over a SignAndEncrypt channel) - returns Bad_SecurityModeInsufficient or Bad_UserAccessDenied otherwise (Part 18 4.2 / 4.4).
2. Delegates to IRoleManager.
3. Reports a RoleMappingRuleChangedAuditEvent (Part 18 4.5).
4. Keeps the typed Identities, Applications, Endpoints, ApplicationsExclude, EndpointsExclude and CustomConfiguration property values in sync with the manager via the RoleConfigurationChanged event.

DiagnosticsNodeManager.AddBehaviourToPredefinedNodeAsync upgrades passive BaseObjectState instances of RoleSetType and RoleType to the typed RoleSetState and RoleState proxies at predefined-node load time.

Default impersonation flow

Per Part 3 4.9 and Part 18 4.3 the default RoleManager rules already grant:

• Anonymous for sessions without authentication;
• AuthenticatedUser for any session with a non-anonymous token;
• TrustedApplication when the session was authenticated with a trusted ApplicationInstance certificate over a signed channel.

Any nonempty Applications filter requires a signed channel and an application certificate, including when ApplicationsExclude is true. The Thumbprint and X509Subject identity criteria evaluate the authenticated user certificate, not the application's channel certificate. Application and TrustedApplication criteria continue to evaluate application identity.

Additional identity-mapping rules are evaluated by IRoleManager.ResolveGrantedRoles after authentication. New integrations should expose claims through IIdentityClaims and add IdentityMappingRuleType entries to the role manager.

User Management (Part 18 §5)

The Part 18 §5 UserManagementType is bound to the standard Server.ServerConfiguration.UserManagement object (NodeId i=24290). Integrators inject an IUserManagement instance via IServerInternal.SetUserManagement before the configuration node manager binds the address space; the default UserManagement implementation wraps an existing IUserDatabase for credential persistence and stores the per-user UserConfigurationMask and description in memory:

using Opc.Ua.Server.UserDatabase;
using Opc.Ua.Server.UserManagement;

var users = new LinqUserDatabase();
users.CreateUser("alice", "secret"u8, [Role.AuthenticatedUser]);

var userManagement = new UserManagement(
    users,
    passwordLength: new Range { Low = 8, High = 256 },
    passwordOptions:
        PasswordOptionsMask.SupportDisableUser
        | PasswordOptionsMask.SupportInitialPasswordChange
        | PasswordOptionsMask.RequiresDigitCharacters);

serverInternal.SetUserManagement(userManagement);

UserManagementBinding.Bind (called automatically by ConfigurationNodeManager.CreateServerConfiguration when an IUserManagement is injected) wires the typed AddUser, ModifyUser, RemoveUser and ChangePassword method-state proxies, enforces RoleAuthorizationGate.CheckAdmin on the admin methods (SecurityAdmin + SignAndEncrypt) and RoleAuthorizationGate.CheckSelfUserName on ChangePassword, and closes a deactivated user's sessions and subscriptions through the server's coordinated teardown. ModifyUser and RemoveUser wait for that teardown and return the user-change result. A session-close failure is logged; it does not turn a committed user change into a failed method result. The binding resolves the server's session manager when needed because the diagnostics address space is created before the session manager. External deactivation notifications are tracked; DisposeAsync drains accepted work. The master drains configuration shutdown work before acquiring the address-space teardown gate, so pending session-close notifications can complete without deadlocking shutdown.

Spec result codes honoured:

Operation	Failure codes
AddUser (§5.2.5)	Bad_AlreadyExists, Bad_OutOfRange, Bad_NotSupported, Bad_ConfigurationError, Bad_UserAccessDenied, Bad_SecurityModeInsufficient, Bad_ResourceUnavailable
ModifyUser (§5.2.6)	Bad_NotFound, Bad_OutOfRange, Bad_NotSupported, Bad_ConfigurationError, Bad_UserAccessDenied, Bad_SecurityModeInsufficient, Bad_InvalidSelfReference
RemoveUser (§5.2.7)	Bad_NotFound, Bad_UserAccessDenied, Bad_NotSupported (NoDelete), Bad_SecurityModeInsufficient, Bad_InvalidSelfReference
ChangePassword (§5.2.8)	Bad_IdentityTokenInvalid, Bad_OutOfRange, Bad_InvalidState, Bad_NotSupported (NoChangeByUser), Bad_SecurityModeInsufficient, Bad_AlreadyExists (new == old)

User name / password storage

The IUserDatabase interface (Opc.Ua.Server.UserDatabase.IUserDatabase) remains the extension point for username/password storage. The shipped implementations are:

• LinqUserDatabase - in-memory.
• JsonUserDatabase - JSON file backed.

The JSON testing/sample database publishes a complete temporary snapshot through atomic file replacement. Failed writes leave the previous file intact, and saves are serialized per database instance. Missing files initialize an empty database; malformed or inaccessible files are logged and reported as errors instead of silently becoming empty databases.

Password verification uses the shared fixed-time comparison with the expected derived-key width and clears working key/password buffers on every exit. Unknown users perform bounded dummy-key verification, and inactive users still perform credential verification before access is denied. This equalizes the expensive verification work; it is not a claim that all surrounding application behavior has constant execution time.

External implementations may be provided by integrators (e.g. backed by SQL, LDAP, or a vendor-specific store).

Client side

Opc.Ua.Client.Roles.RoleManagementClient is a strongly-typed async client over the standard Server.ServerCapabilities.RoleSet object:

using Opc.Ua.Client.Roles;

RoleManagementClient client = session.OpenRoleManagementClient();

// List every role exposed by the server.
IReadOnlyList<RoleInfo> roles = await client.ListRolesAsync();

// Add a UserName identity rule to the Observer role.
await client.AddIdentityAsync(
    Opc.Ua.ObjectIds.WellKnownRole_Observer,
    new IdentityMappingRuleType
    {
        CriteriaType = IdentityCriteriaType.UserName,
        Criteria = "alice"
    });

// Toggle the ApplicationsExclude flag on the Operator role.
await client.SetApplicationsExcludeAsync(
    Opc.Ua.ObjectIds.WellKnownRole_Operator, value: false);

// Add a custom role under a vendor namespace.
NodeId newRoleId = await client.AddRoleAsync(
    "OpsLead",
    namespaceUri: "urn:example:roles");

// Remove a dynamic role.
await client.RemoveRoleAsync(newRoleId);

All mutator methods require the calling session to hold the SecurityAdmin role and use a SignAndEncrypt secure channel; otherwise the server returns Bad_UserAccessDenied / Bad_SecurityModeInsufficient which surfaces as a ServiceResultException.

GDS

The GDS adds the following roles in addition to the standard well-known set:

• DiscoveryAdmin
• SecurityAdmin
• CertificateAuthorityAdmin
• RegistrationAuthorityAdmin
• ApplicationSelfAdmin

See GdsRole.cs.

Known limitations

• Integration tests for end-to-end RoleSet / UserManagement scenarios (e.g. AddRole over the wire followed by browse + AddIdentity + activated session under the new grant) are tracked as a follow-up.

References

• OPC UA Part 18 v1.05.06 - Role-Based Security
• OPC UA Part 3 4.9 - Well-Known Roles
• src/Opc.Ua.Server/RoleBasedUserManagement/
• src/Opc.Ua.Client/Roles/
• tests/Opc.Ua.Server.Tests/RoleManagerTests.cs