Support HS256 signed keys

src/IIIFAuth2/IIIFAuth2.API.Tests/Infrastructure/Auth/RoleProvisioning/Oidc/Auth0ClientTests.cs

@@ -153,8 +153,7 @@ public async Task GetDlcsRolesForCode_PassesIdTokenToTokenHandler()
 
         // Assert
         A.CallTo(() => jwtTokenHandler.GetClaimsFromToken(idToken, jwksUri, "https://dlcs-dev.uk.auth0.com/", "test-id",
-                A<CancellationToken>._))
-            .MustHaveHappened();
+            "test-secret", A<CancellationToken>._)).MustHaveHappened();
     }
 
     [Fact]
@@ -172,7 +171,7 @@ public async Task GetDlcsRolesForCode_ReturnsEmptyRoles_IfNoMappedClaims()
             ClaimType = claimType,
         };
         A.CallTo(() => jwtTokenHandler.GetClaimsFromToken(idToken, A<Uri>._, A<string>._, A<string>._,
-                A<CancellationToken>._))
+                A<string>._, A<CancellationToken>._))
             .Returns(new ClaimsPrincipal(new ClaimsIdentity()));
 
         var httpResponseMessage = new HttpResponseMessage(HttpStatusCode.OK);
@@ -207,7 +206,7 @@ public async Task GetDlcsRolesForCode_ReturnsMappedClaims()
             }
         };
         A.CallTo(() => jwtTokenHandler.GetClaimsFromToken(idToken, A<Uri>._, A<string>._, A<string>._,
-                A<CancellationToken>._))
+                A<string>._, A<CancellationToken>._))
             .Returns(new ClaimsPrincipal(new ClaimsIdentity(new []{new Claim(claimType, "foobar")})));
 
         var httpResponseMessage = new HttpResponseMessage(HttpStatusCode.OK);

src/IIIFAuth2/IIIFAuth2.API/Infrastructure/Auth/RoleProvisioning/Oidc/Auth0Client.cs

@@ -87,7 +87,7 @@ public async Task<IReadOnlyCollection<string>> GetDlcsRolesForCode(OidcConfigura
 
         var claimsPrincipal =
             await jwtTokenHandler.GetClaimsFromToken(auth0Token.IdToken, GetJwksUri(oidcConfiguration),
-                issuer, audience, cancellationToken);
+                issuer, audience, oidcConfiguration.ClientSecret, cancellationToken);
         if (claimsPrincipal == null) return Array.Empty<string>();
 
         var dlcsRoles = claimsConverter.GetDlcsRolesFromClaims(claimsPrincipal, oidcConfiguration);

src/IIIFAuth2/IIIFAuth2.API/Infrastructure/Auth/RoleProvisioning/Oidc/JwtTokenParser.cs

@@ -1,5 +1,6 @@
 using System.IdentityModel.Tokens.Jwt;
 using System.Security.Claims;
+using System.Text;
 using IIIFAuth2.API.Settings;
 using LazyCache;
 using Microsoft.Extensions.Caching.Memory;
@@ -17,10 +18,11 @@ public interface IJwtTokenHandler
     /// <param name="jwksUri">Path where jwks can be found</param>
     /// <param name="issuer">Valid "iss" value</param>
     /// <param name="audience">Valid "aud" value</param>
+    /// <param name="clientSecret">ClientSecret, if known. Used for symmetric validation</param>
     /// <param name="cancellationToken">Current cancellation token</param>
     /// <returns><see cref="ClaimsPrincipal"/> if jwt is valid, else null</returns>
     Task<ClaimsPrincipal?> GetClaimsFromToken(string jwtToken, Uri jwksUri, string issuer, string audience,
-        CancellationToken cancellationToken);
+        string? clientSecret, CancellationToken cancellationToken);
 }
 
 public class JwtTokenHandler : IJwtTokenHandler
@@ -41,17 +43,16 @@ public JwtTokenHandler(HttpClient httpClient, IAppCache appCache, IOptions<AuthS
 
     /// <inheritdoc />
     public async Task<ClaimsPrincipal?> GetClaimsFromToken(string jwtToken, Uri jwksUri, string issuer,
-        string audience, CancellationToken cancellationToken)
+        string audience, string? clientSecret, CancellationToken cancellationToken)
     {
         try
         {
-            var jwks = await GetWebKeySetForDomain(jwksUri, cancellationToken);
-
+            var issuerSigningKeys = await GetSigningKeys(jwksUri, clientSecret, cancellationToken); 
             var tokenHandler = new JwtSecurityTokenHandler();
             var tokenValidationParameters = new TokenValidationParameters
             {
                 ValidateIssuerSigningKey = true,
-                IssuerSigningKeys = jwks.GetSigningKeys(),
+                IssuerSigningKeys = issuerSigningKeys,
                 ValidateIssuer = true,
                 ValidIssuer = issuer,
                 ValidateAudience = true,
@@ -75,6 +76,22 @@ public JwtTokenHandler(HttpClient httpClient, IAppCache appCache, IOptions<AuthS
         return null;
     }
 
+    private async Task<IList<SecurityKey>> GetSigningKeys(Uri jwksUri, string? clientSecret, CancellationToken 
+        cancellationToken)
+    {
+        // jwks used for "alg": "RS256"
+        var jwks = await GetWebKeySetForDomain(jwksUri, cancellationToken);
+        var issuerSigningKeys = jwks.GetSigningKeys();
+
+        if (!string.IsNullOrWhiteSpace(clientSecret))
+        {
+            // client-secret for "alg": "HS256"
+            issuerSigningKeys.Add(new SymmetricSecurityKey(Encoding.ASCII.GetBytes(clientSecret)));
+        }
+
+        return issuerSigningKeys;
+    }
+
     private async Task<JsonWebKeySet> GetWebKeySetForDomain(Uri jwksPath, CancellationToken cancellationToken)
     {
         var cacheKey = $"{jwksPath}:jwks";

src/IIIFAuth2/IIIFAuth2.API/Infrastructure/Auth/RoleProvisioning/Oidc/OidcRoleProviderHandler.cs

@@ -105,6 +105,12 @@ private async Task EnsureSecrets(OidcConfiguration configuration, Guid accessSer
                 var secretsJson = await secretsManagerCache.GetSecretString(secretName);
                 var secret = JsonSerializer.Deserialize<Secrets>(secretsJson, Options);
                 configuration.ClientSecret = secret?.ClientSecret ?? string.Empty;
+
+                if (string.IsNullOrWhiteSpace(configuration.ClientSecret))
+                {
+                    logger.LogWarning("Fetched secretsmanager secret {SecretName} for {AccessService} but got no value",
+                        secretName, accessServiceId);
+                }
             }
             catch (Exception ex)
             {