fix(server): resolve High code-review findings (Server-002, Server-009)

Server-002 — AuthorizationGate lax-mode no longer overrides explicit deny.
IsAllowed now switches on the evaluator's AuthorizationVerdict: Allow -> true,
Denied (an authored deny rule matched) -> false in BOTH strict and lax mode,
and only the indeterminate NotGranted case falls through to !_strictMode.
Previously `if (decision.IsAllowed) return true; return !_strictMode;` let lax
mode (the default) nullify authored NodeAcl deny rules for fully-resolved
sessions. The tri-state AuthorizationVerdict.Denied member is now honoured.

Server-009 — LDAP is secure-by-default. LdapOptions.AllowInsecureLdap now
defaults to false (was true) and Program.cs's config fallback reads `?? false`
(was `?? true`), so an LDAP-enabled deployment will not bind credentials over
an unencrypted socket unless an operator explicitly opts in. Program.cs also
logs a startup warning when LDAP is enabled with UseTls=false and
AllowInsecureLdap=true, flagging the clear-text server->LDAP credential hop.

Regression tests: AuthorizationGateTests covers all four verdict x mode
combinations via a fixed-verdict evaluator stub; new LdapOptionsTests asserts
the secure defaults. Both Server and Server.Tests build clean; the 15 targeted
tests pass.

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

code-reviews/Server/findings.md

@@ -7,7 +7,7 @@
 | Review date | 2026-05-22 |
 | Commit reviewed | `76d35d1` |
 | Status | Reviewed |
-| Open findings | 14 |
+| Open findings | 12 |
 
 ## Checklist coverage
 
@@ -46,13 +46,13 @@
 | Severity | High |
 | Category | Correctness & logic bugs |
 | Location | `src/Server/ZB.MOM.WW.OtOpcUa.Server/Security/AuthorizationGate.cs:60-63` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `IsAllowed` does `if (decision.IsAllowed) return true; return !_strictMode;`. When a session carries resolved LDAP groups and the evaluator returns an explicit deny, lax mode (default) overrides it to `true`. The lax fallback is intended only for sessions lacking LDAP groups / missing tries, but here it also nullifies authored `NodeAcl` deny rules for fully-resolved sessions. Per-tag deny ACLs do nothing until `StrictMode` is on.
 
 **Recommendation:** Distinguish "indeterminate / no grant" from "explicit deny." Fall through to `!_strictMode` only when indeterminate; an explicit deny returns `false` regardless of mode. Extend `AuthorizeDecision` with an `IsExplicitDeny` flag if needed.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-22 — `AuthorizationGate.IsAllowed` now switches on the evaluator's `AuthorizationVerdict`: `Allow` returns true, `Denied` (explicit deny rule matched) returns false in both strict and lax mode, and only the indeterminate `NotGranted` case falls through to `!_strictMode`. The existing `AuthorizationVerdict.Denied` tri-state member is now honoured rather than collapsed into the lax fallback. Regression tests `ExplicitDeny_LaxMode_Denies` / `ExplicitDeny_StrictMode_Denies` / `NotGranted_LaxMode_Allows` / `NotGranted_StrictMode_Denies` in `AuthorizationGateTests` cover all four verdict×mode combinations via a fixed-verdict evaluator stub.
 
 ### Server-003
 | Field | Value |
@@ -144,13 +144,13 @@
 | Severity | High |
 | Category | Security |
 | Location | `src/Server/ZB.MOM.WW.OtOpcUa.Server/Security/LdapOptions.cs:44`, `src/Server/ZB.MOM.WW.OtOpcUa.Server/Program.cs:74` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `AllowInsecureLdap` defaults to `true` (and `Program.cs` reads `?? true`); `UseTls` defaults to `false`. Out of the box, usernames and plaintext passwords are bound to LDAP over an unencrypted socket. A production deployment enabling LDAP without explicitly setting `AllowInsecureLdap=false` ships credentials in clear text on the server→LDAP hop.
 
 **Recommendation:** Default `AllowInsecureLdap` to `false` in both the property initializer and the `Program.cs` fallback. Log a startup warning when LDAP is enabled with `UseTls=false && AllowInsecureLdap=true`.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-22 — `LdapOptions.AllowInsecureLdap` now defaults to `false` (secure-by-default) and `Program.cs`'s config fallback reads `?? false`. `Program.cs` logs a startup `Log.Warning` when LDAP is enabled with `UseTls=false && AllowInsecureLdap=true`, flagging the clear-text credential hop. Regression tests in `LdapOptionsTests` assert the new secure defaults.
 
 ### Server-010
 | Field | Value |

src/Server/ZB.MOM.WW.OtOpcUa.Server/Program.cs

@@ -71,13 +71,24 @@ var ldapOptions = new LdapOptions
     Server = ldapSection.GetValue<string>("Server") ?? "localhost",
     Port = ldapSection.GetValue<int?>("Port") ?? 3893,
     UseTls = ldapSection.GetValue<bool?>("UseTls") ?? false,
-    AllowInsecureLdap = ldapSection.GetValue<bool?>("AllowInsecureLdap") ?? true,
+    AllowInsecureLdap = ldapSection.GetValue<bool?>("AllowInsecureLdap") ?? false,
     SearchBase = ldapSection.GetValue<string>("SearchBase") ?? "dc=lmxopcua,dc=local",
     ServiceAccountDn = ldapSection.GetValue<string>("ServiceAccountDn") ?? string.Empty,
     ServiceAccountPassword = ldapSection.GetValue<string>("ServiceAccountPassword") ?? string.Empty,
     GroupToRole = ldapSection.GetSection("GroupToRole").Get<Dictionary<string, string>>() ?? new(StringComparer.OrdinalIgnoreCase),
 };
 
+// Security: an LDAP bind without TLS sends usernames + plaintext passwords in clear
+// text on the server→LDAP hop. AllowInsecureLdap is a dev-only escape hatch; warn
+// loudly when a deployment has enabled LDAP and opted into the insecure path.
+if (ldapOptions.Enabled && !ldapOptions.UseTls && ldapOptions.AllowInsecureLdap)
+{
+    Log.Warning(
+        "LDAP authentication is enabled with UseTls=false and AllowInsecureLdap=true — "
+        + "credentials are sent in clear text on the server→LDAP hop. Set Ldap:UseTls=true "
+        + "(LDAPS) for production deployments.");
+}
+
 var opcUaOptions = new OpcUaServerOptions
 {
     EndpointUrl = opcUaSection.GetValue<string>("EndpointUrl") ?? "opc.tcp://0.0.0.0:4840/OtOpcUa",

src/Server/ZB.MOM.WW.OtOpcUa.Server/Security/AuthorizationGate.cs

@@ -22,6 +22,12 @@ namespace ZB.MOM.WW.OtOpcUa.Server.Security;
 ///     <c>StrictMode = false</c>, missing cluster tries OR sessions without resolved
 ///     LDAP groups get <c>true</c> so existing deployments keep working while ACLs are
 ///     populated. Flip to strict via <c>Authorization:StrictMode = true</c> in production.</para>
+///
+///     <para>The lax-mode fallback only covers the <i>indeterminate</i> case
+///     (<see cref="AuthorizationVerdict.NotGranted"/> — no grant matched). An explicit
+///     <see cref="AuthorizationVerdict.Denied"/> verdict from an authored deny rule is a
+///     definite decision and is honoured in both strict and lax mode — lax mode never
+///     overrides a deny.</para>
 /// </remarks>
 public sealed class AuthorizationGate
 {
@@ -58,9 +64,20 @@ public sealed class AuthorizationGate
         }
 
         var decision = _evaluator.Authorize(session, operation, scope);
-        if (decision.IsAllowed) return true;
+        return decision.Verdict switch
+        {
+            // At least one grant matched — allow regardless of mode.
+            AuthorizationVerdict.Allow => true,
 
-        return !_strictMode;
+            // An authored deny rule matched. This is a definite verdict, not a gap in
+            // the ACLs, so the lax-mode fallback must NOT override it — an explicit
+            // deny denies in both strict and lax mode.
+            AuthorizationVerdict.Denied => false,
+
+            // No grant matched (indeterminate). Strict mode denies; lax mode lets the
+            // dispatch proceed so deployments keep working while ACLs are populated.
+            _ => !_strictMode,
+        };
     }
 
     /// <summary>

src/Server/ZB.MOM.WW.OtOpcUa.Server/Security/LdapOptions.cs

@@ -40,8 +40,12 @@ public sealed class LdapOptions
     public int Port { get; init; } = 3893;
     public bool UseTls { get; init; } = false;
 
-    /// <summary>Dev-only escape hatch — must be false in production.</summary>
+    /// <summary>
-    public bool AllowInsecureLdap { get; init; } = true;
+    ///     Dev-only escape hatch that permits an unencrypted LDAP bind (plaintext credentials on
+    ///     the server→LDAP hop) when <see cref="UseTls"/> is <c>false</c>. Defaults to <c>false</c> —
+    ///     production deployments are secure-by-default and must opt in explicitly to run insecure.
+    /// </summary>
+    public bool AllowInsecureLdap { get; init; } = false;
 
     public string SearchBase { get; init; } = "dc=lmxopcua,dc=local";
     public string ServiceAccountDn { get; init; } = string.Empty;

tests/Server/ZB.MOM.WW.OtOpcUa.Server.Tests/AuthorizationGateTests.cs

@@ -133,4 +133,52 @@ public sealed class AuthorizationGateTests
 
         gate.BuildSessionState(new UserIdentity(), "c1").ShouldBeNull();
     }
+
+    /// <summary>Evaluator stub that always returns a fixed verdict — lets the gate's
+    /// verdict handling be exercised independent of the trie evaluator (which only ever
+    /// produces Allow / NotGranted).</summary>
+    private sealed class FixedVerdictEvaluator(AuthorizationVerdict verdict) : IPermissionEvaluator
+    {
+        public AuthorizationDecision Authorize(UserAuthorizationState session, OpcUaOperation operation, NodeScope scope)
+            => new(verdict, []);
+    }
+
+    // Server-002 regression: an explicit Denied verdict must be honoured in BOTH modes —
+    // the lax-mode fallback covers only the indeterminate (NotGranted) case.
+
+    [Fact]
+    public void ExplicitDeny_LaxMode_Denies()
+    {
+        var gate = new AuthorizationGate(new FixedVerdictEvaluator(AuthorizationVerdict.Denied), strictMode: false);
+        var identity = new FakeIdentity("ops-user", ["cn=ops"]);
+
+        gate.IsAllowed(identity, OpcUaOperation.Read, Scope()).ShouldBeFalse();
+    }
+
+    [Fact]
+    public void ExplicitDeny_StrictMode_Denies()
+    {
+        var gate = new AuthorizationGate(new FixedVerdictEvaluator(AuthorizationVerdict.Denied), strictMode: true);
+        var identity = new FakeIdentity("ops-user", ["cn=ops"]);
+
+        gate.IsAllowed(identity, OpcUaOperation.Read, Scope()).ShouldBeFalse();
+    }
+
+    [Fact]
+    public void NotGranted_LaxMode_Allows()
+    {
+        var gate = new AuthorizationGate(new FixedVerdictEvaluator(AuthorizationVerdict.NotGranted), strictMode: false);
+        var identity = new FakeIdentity("ops-user", ["cn=ops"]);
+
+        gate.IsAllowed(identity, OpcUaOperation.Read, Scope()).ShouldBeTrue();
+    }
+
+    [Fact]
+    public void NotGranted_StrictMode_Denies()
+    {
+        var gate = new AuthorizationGate(new FixedVerdictEvaluator(AuthorizationVerdict.NotGranted), strictMode: true);
+        var identity = new FakeIdentity("ops-user", ["cn=ops"]);
+
+        gate.IsAllowed(identity, OpcUaOperation.Read, Scope()).ShouldBeFalse();
+    }
 }

tests/Server/ZB.MOM.WW.OtOpcUa.Server.Tests/LdapOptionsTests.cs

@@ -0,0 +1,31 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Server.Security;
+
+namespace ZB.MOM.WW.OtOpcUa.Server.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class LdapOptionsTests
+{
+    // Server-009 regression: the out-of-the-box posture must be secure. AllowInsecureLdap
+    // is a dev-only escape hatch — a deployment that enables LDAP without explicitly
+    // opting in must not bind credentials over an unencrypted socket.
+
+    [Fact]
+    public void AllowInsecureLdap_DefaultsToFalse()
+    {
+        new LdapOptions().AllowInsecureLdap.ShouldBeFalse();
+    }
+
+    [Fact]
+    public void UseTls_DefaultsToFalse_SoInsecureBindRequiresExplicitOptIn()
+    {
+        // UseTls=false on its own is fine — without AllowInsecureLdap the bind path
+        // refuses to send plaintext credentials. The two flags together are the only
+        // way to reach the insecure path, and both must be set deliberately.
+        var options = new LdapOptions();
+
+        options.UseTls.ShouldBeFalse();
+        options.AllowInsecureLdap.ShouldBeFalse();
+    }
+}