fix(security): resolve Security-004..007 — configurable user-id attribute, DN escaping, JWT issuer/audience validation, idle-timeout preservation

src/ScadaLink.Security/LdapAuthService.cs

@@ -71,7 +71,7 @@ public class LdapAuthService
 
             try
             {
-                var searchFilter = $"(uid={EscapeLdapFilter(username)})";
+                var searchFilter = $"({_options.LdapUserIdAttribute}={EscapeLdapFilter(username)})";
                 var searchResults = await Task.Run(() =>
                     connection.Search(
                         _options.LdapSearchBase,
@@ -133,17 +133,13 @@ public class LdapAuthService
     /// </summary>
     private async Task<string> ResolveUserDnAsync(LdapConnection connection, string username, CancellationToken ct)
     {
-        // If username already looks like a DN, use it as-is
-        if (username.Contains('='))
-            return username;
-
         // If a service account is configured, search for the user's actual DN
         if (!string.IsNullOrWhiteSpace(_options.LdapServiceAccountDn))
         {
             await Task.Run(() =>
                 connection.Bind(_options.LdapServiceAccountDn, _options.LdapServiceAccountPassword), ct);
 
-            var searchFilter = $"(uid={EscapeLdapFilter(username)})";
+            var searchFilter = $"({_options.LdapUserIdAttribute}={EscapeLdapFilter(username)})";
             var searchResults = await Task.Run(() =>
                 connection.Search(
                     _options.LdapSearchBase,
@@ -158,13 +154,68 @@ public class LdapAuthService
                 return entry.Dn;
             }
 
-            throw new LdapException("User not found", LdapException.NoSuchObject, $"No entry found for uid={username}");
+            throw new LdapException("User not found", LdapException.NoSuchObject,
+                $"No entry found for {_options.LdapUserIdAttribute}={username}");
         }
 
-        // Fallback: construct DN directly
-        return string.IsNullOrWhiteSpace(_options.LdapSearchBase)
-            ? $"cn={username}"
-            : $"cn={username},{_options.LdapSearchBase}";
+        // Fallback: construct the bind DN directly from the configured user-id
+        // attribute. The username is RFC 4514 DN-escaped so it cannot alter the
+        // DN structure (Security-005). The previous Contains('=') shortcut that
+        // accepted a raw caller-supplied DN has been removed — accepting an
+        // arbitrary DN from untrusted input let a client choose the bind identity.
+        return BuildFallbackUserDn(username, _options.LdapSearchBase, _options.LdapUserIdAttribute);
+    }
+
+    /// <summary>
+    /// Builds the no-service-account fallback bind DN as
+    /// <c>{userIdAttribute}={escaped-username}[,{searchBase}]</c>. The username is
+    /// escaped per RFC 4514 so DN metacharacters in untrusted input cannot inject
+    /// additional RDN components or change the bind identity.
+    /// </summary>
+    public static string BuildFallbackUserDn(string username, string searchBase, string userIdAttribute)
+    {
+        var rdn = $"{userIdAttribute}={EscapeLdapDn(username)}";
+        return string.IsNullOrWhiteSpace(searchBase) ? rdn : $"{rdn},{searchBase}";
+    }
+
+    /// <summary>
+    /// Escapes a string for use as an RFC 4514 DN attribute value: the special
+    /// characters <c>, + " \ &lt; &gt; ;</c> are backslash-escaped, as are a leading
+    /// or trailing space and a leading <c>#</c>.
+    /// </summary>
+    public static string EscapeLdapDn(string input)
+    {
+        if (string.IsNullOrEmpty(input))
+            return input;
+
+        var sb = new System.Text.StringBuilder(input.Length + 8);
+        for (var i = 0; i < input.Length; i++)
+        {
+            var c = input[i];
+            var isEdgeSpace = c == ' ' && (i == 0 || i == input.Length - 1);
+            var isLeadingHash = c == '#' && i == 0;
+            switch (c)
+            {
+                case ',':
+                case '+':
+                case '"':
+                case '\\':
+                case '<':
+                case '>':
+                case ';':
+                    sb.Append('\\').Append(c);
+                    break;
+                case '\0':
+                    sb.Append("\\00");
+                    break;
+                default:
+                    if (isEdgeSpace || isLeadingHash)
+                        sb.Append('\\');
+                    sb.Append(c);
+                    break;
+            }
+        }
+        return sb.ToString();
     }
 
     private static string EscapeLdapFilter(string input)