From 93316e3431f68735c73a0aa6a8f069da1a58e281 Mon Sep 17 00:00:00 2001
From: Joseph Doherty <dohejw01@gmail.com>
Date: Tue, 26 May 2026 04:35:46 -0400
Subject: [PATCH] feat(security): JwtTokenService with HS256 + 15-min expiry

---
 .../Jwt/JwtOptions.cs                         |  16 +++
 .../Jwt/JwtTokenService.cs                    | 102 ++++++++++++++++++
 2 files changed, 118 insertions(+)
 create mode 100644 src/Server/ZB.MOM.WW.OtOpcUa.Security/Jwt/JwtOptions.cs
 create mode 100644 src/Server/ZB.MOM.WW.OtOpcUa.Security/Jwt/JwtTokenService.cs

diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.Security/Jwt/JwtOptions.cs b/src/Server/ZB.MOM.WW.OtOpcUa.Security/Jwt/JwtOptions.cs
new file mode 100644
index 0000000..9541be8
--- /dev/null
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.Security/Jwt/JwtOptions.cs
@@ -0,0 +1,16 @@
+namespace ZB.MOM.WW.OtOpcUa.Security.Jwt;
+
+public sealed class JwtOptions
+{
+    public const string SectionName = "Security:Jwt";
+    public const int MinSigningKeyBytes = 32;
+
+    /// <summary>HS256 signing key. Must be at least 32 bytes (256 bits) UTF-8.</summary>
+    public string SigningKey { get; set; } = string.Empty;
+
+    public string Issuer { get; set; } = "otopcua";
+    public string Audience { get; set; } = "otopcua";
+
+    /// <summary>Default token expiry. Mirrors ScadaLink (15 min).</summary>
+    public int ExpiryMinutes { get; set; } = 15;
+}
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.Security/Jwt/JwtTokenService.cs b/src/Server/ZB.MOM.WW.OtOpcUa.Security/Jwt/JwtTokenService.cs
new file mode 100644
index 0000000..499046b
--- /dev/null
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.Security/Jwt/JwtTokenService.cs
@@ -0,0 +1,102 @@
+using System.IdentityModel.Tokens.Jwt;
+using System.Security.Claims;
+using System.Text;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using Microsoft.IdentityModel.Tokens;
+
+namespace ZB.MOM.WW.OtOpcUa.Security.Jwt;
+
+public sealed class JwtTokenService
+{
+    public const string DisplayNameClaimType = "DisplayName";
+    public const string UsernameClaimType = "Username";
+    public const string RoleClaimType = "Role";
+
+    private readonly JwtOptions _options;
+    private readonly ILogger<JwtTokenService> _logger;
+
+    public JwtTokenService(IOptions<JwtOptions> options, ILogger<JwtTokenService> logger)
+    {
+        _options = options.Value;
+        _logger = logger;
+
+        var keyByteLength = string.IsNullOrEmpty(_options.SigningKey)
+            ? 0
+            : Encoding.UTF8.GetByteCount(_options.SigningKey);
+        if (keyByteLength < JwtOptions.MinSigningKeyBytes)
+        {
+            throw new InvalidOperationException(
+                $"JwtOptions.SigningKey must be at least {JwtOptions.MinSigningKeyBytes} bytes " +
+                $"(256 bits) for HMAC-SHA256; the configured key is {keyByteLength} byte(s).");
+        }
+    }
+
+    public string Issue(string displayName, string username, IReadOnlyList<string> roles)
+    {
+        var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_options.SigningKey));
+        var credentials = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);
+
+        var claims = new List<Claim>
+        {
+            new(DisplayNameClaimType, displayName),
+            new(UsernameClaimType, username),
+        };
+        foreach (var role in roles)
+            claims.Add(new Claim(RoleClaimType, role));
+
+        var token = new JwtSecurityToken(
+            issuer: _options.Issuer,
+            audience: _options.Audience,
+            claims: claims,
+            expires: DateTime.UtcNow.AddMinutes(_options.ExpiryMinutes),
+            signingCredentials: credentials);
+
+        return new JwtSecurityTokenHandler().WriteToken(token);
+    }
+
+    public bool TryValidate(string token, out ClaimsPrincipal? principal)
+    {
+        principal = null;
+        var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_options.SigningKey));
+        var parameters = new TokenValidationParameters
+        {
+            ValidateIssuer = true,
+            ValidIssuer = _options.Issuer,
+            ValidateAudience = true,
+            ValidAudience = _options.Audience,
+            ValidateLifetime = true,
+            ValidateIssuerSigningKey = true,
+            IssuerSigningKey = key,
+            ClockSkew = TimeSpan.Zero,
+        };
+
+        try
+        {
+            var handler = new JwtSecurityTokenHandler();
+            principal = handler.ValidateToken(token, parameters, out _);
+            return true;
+        }
+        catch (Exception ex) when (ex is SecurityTokenException or ArgumentException)
+        {
+            _logger.LogDebug(ex, "JWT validation failed");
+            return false;
+        }
+    }
+
+    /// <summary>
+    /// Returns the validation parameters that the JwtBearer middleware should use. Centralised
+    /// so the bearer pipeline can't drift from <see cref="TryValidate"/>.
+    /// </summary>
+    public TokenValidationParameters BuildValidationParameters() => new()
+    {
+        ValidateIssuer = true,
+        ValidIssuer = _options.Issuer,
+        ValidateAudience = true,
+        ValidAudience = _options.Audience,
+        ValidateLifetime = true,
+        ValidateIssuerSigningKey = true,
+        IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_options.SigningKey)),
+        ClockSkew = TimeSpan.Zero,
+    };
+}