# Role-Based Security (OPC UA Part 18)

## Contents

- [Overview](#overview)
- [Server side](#server-side)
  - [`IRoleManager`](#irolemanager)
  - [Authoring an identity-mapping rule with claims](#authoring-an-identity-mapping-rule-with-claims)
  - [`RoleConfigurationChanged` event](#roleconfigurationchanged-event)
  - [Typed-proxy address-space binding](#typed-proxy-address-space-binding)
  - [Default impersonation flow](#default-impersonation-flow)
  - [User Management](#user-management-part-18-5)
  - [User name / password storage](#user-name--password-storage)
- [Client side](#client-side)
- [GDS](#gds)
- [Known limitations](#known-limitations)
- [References](#references)

## Overview

The OPC UA .NET Standard Stack implements the role-based security model from
[OPC UA Part 18: Role-Based Security (v1.05.06)](https://reference.opcfoundation.org/Core/Part18/v105/docs/)
together with the well-known roles defined in
[OPC UA Part 3 4.9.2](https://reference.opcfoundation.org/Core/Part3/v105/docs/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`:

```csharp
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](IdentityProviders.md)) 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:

```csharp
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.BindAsync(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.

Queued removal retains the exact binding generation and node reference it owns.
Re-adding a role advances that generation, even when the same well-known NodeId
and RoleState are reused. Cleanup rechecks the role manager and conditionally
claims the removed generation before deleting the node. A failed AddRole that
never acquired a binding cannot delete the foreign node that caused its collision.

### 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. Built-in
`LinqUserDatabase` and `JsonUserDatabase` also persist the per-user
`UserConfigurationMask` and description:

```csharp
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);
```

`IUserDatabase` commits credentials and metadata together, so disabled and
`MustChangePassword` decisions survive a restart. A custom database implements
`CreateUser`, `ResetPassword` and `UpdateUserMetadata` alongside the credential
members; each mutation must be one transaction, and a rejected or failed write
must leave the live and persisted records unchanged.

`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.
Authentication reads committed credential and role records without waiting
for snapshot I/O; the pending replacement is visible only to snapshot
persistence until the write succeeds. A failed write never publishes its
candidate credentials.

Self-service password changes verify the captured credential and derive the
replacement outside the credential-store and metadata-reader locks, retaining
100,000-iteration PBKDF2-SHA512. The store commits only if the user's identity
and captured verifier still match, so a concurrent password reset or change
cannot be overwritten by stale verification. The password and cleared
`MustChangePassword` flag remain one atomic persisted update, preserving the
latest other metadata. Management mutations remain serialized separately from
authentication reads; self-service hashing and snapshot I/O do not hold the
metadata write lock. Administrative mutations retain their existing metadata
publication semantics.

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:

```csharp
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);
```

`ListRolesAsync` includes both `RoleType` instances and instances of its
subtypes, resolving derived types through the session's node cache. Other
object types under the RoleSet are excluded.

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`.

### Bounded role snapshots

Use `new RoleManagementClient(session, maxMappingEntries: 1000)` to limit a role
snapshot. The limit applies separately to identity, application and endpoint
mapping collections, before client-side decoded-array/list copies. Zero and the
existing one-argument constructor preserve legacy behavior. This does not bound
the separate `ListRolesAsync` traversal.

When a target check and subsequent role calls must use the same server session,
capture a [`SessionRequestContext`](Sessions.md#generation-bound-client-requests)
first. Resolve the target through `context.Session` and use
`new RoleManagementClient(context.Session, maxMappingEntries: 1000)` until the
operation is finished. Recovery then refuses later calls instead of silently
moving the operation to a replacement session.

## GDS

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

- `DiscoveryAdmin`
- `SecurityAdmin`
- `CertificateAuthorityAdmin`
- `RegistrationAuthorityAdmin`
- `ApplicationSelfAdmin`

See [GdsRole.cs](https://github.com/OPCFoundation/UA-.NETStandard/blob/main/src/Opc.Ua.Gds.Server/RoleBasedUserManagement/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](https://reference.opcfoundation.org/Core/Part18/v105/docs/)
- [OPC UA Part 3 4.9 - Well-Known Roles](https://reference.opcfoundation.org/Core/Part3/v105/docs/4.9)
- `src/Opc.Ua.Server/RoleBasedUserManagement/`
- `src/Opc.Ua.Client/Roles/`
- `tests/Opc.Ua.Server.Tests/RoleManagerTests.cs`