Added support for multiple valid token issuers

src/IdentityServer/Configuration/DependencyInjection/Options/IdentityServerOptions.cs

@@ -22,6 +22,15 @@ public class IdentityServerOptions
     /// </value>
     public string? IssuerUri { get; set; }
 
+    /// <summary>
+    /// Gets or sets the list of valid issuers, e.g. https://myissuer.com.
+    /// If not set, the issuer name is inferred from the request
+    /// </summary>
+    /// <value>
+    /// List of valid issuers, e.g. https://myissuer.com
+    /// </value>
+    public string[]? ValidIssuers { get; set; }
+
     /// <summary>
     /// Set to false to preserve the original casing of the IssuerUri. Defaults to true.
     /// </summary>

src/IdentityServer/Services/Default/DefaultIssuerNameService.cs

@@ -3,6 +3,7 @@
 
 
 using System;
+using System.Linq;
 using System.Threading.Tasks;
 using Duende.IdentityServer.Configuration;
 using Duende.IdentityServer.Extensions;
@@ -31,7 +32,7 @@ public DefaultIssuerNameService(IdentityServerOptions options, IServerUrls urls,
         _urls = urls;
         _httpContextAccessor = httpContextAccessor;
     }
-        
+
     /// <inheritdoc />
     public Task<string> GetCurrentAsync()
     {
@@ -75,4 +76,25 @@ public Task<string> GetCurrentAsync()
 
         return Task.FromResult(issuer);
     }
+
+    /// <inheritdoc />
+    public Task<string[]> GetListAsync()
+    {
+        // if they've explicitly configured a URI then use it,
+        // otherwise dynamically calculate it
+        var issuers = _options.ValidIssuers;
+
+        if (issuers == null || issuers.Length < 1)
+        {
+            issuers = [GetCurrentAsync().Result];
+
+        }
+        else if (_options.LowerCaseIssuerUri)
+        {
+            issuers = issuers.Select(x => x.ToLowerInvariant()).ToArray();
+        }
+
+
+        return Task.FromResult(issuers);
+    }
 }

src/IdentityServer/Services/IIssuerNameService.cs

@@ -18,4 +18,10 @@ public interface IIssuerNameService
     /// </summary>
     /// <returns></returns>
     Task<string> GetCurrentAsync();
+
+    /// <summary>
+    /// Returns the list of valid issuers
+    /// </summary>
+    /// <returns></returns>
+    Task<string[]> GetListAsync();
 }

src/IdentityServer/Validation/Default/TokenValidator.cs

@@ -281,6 +281,7 @@ private async Task<TokenValidationResult> ValidateJwtAsync(string jwtString,
         var parameters = new TokenValidationParameters
         {
             ValidIssuer = await _issuerNameService.GetCurrentAsync(),
+            ValidIssuers = await _issuerNameService.GetListAsync(),
             IssuerSigningKeys = validationKeys.Select(k => k.Key),
             ValidateLifetime = validateLifetime
         };