Set JWT.alg to PS256 with PssPadding. (#3789)

Author: TingluoHuang

src/Sdk/WebApi/WebApi/Jwt/JsonWebToken.cs

@@ -25,7 +25,10 @@ public enum JWTAlgorithm
         HS256,
 
         [EnumMember]
-        RS256
+        RS256,
+
+        [EnumMember]
+        PS256,
     }
 
     //JsonWebToken is marked as DataContract so
@@ -286,6 +289,7 @@ private static byte[] GetSignature(JWTHeader header, JWTPayload payload, JWTAlgo
             {
                 case JWTAlgorithm.HS256:
                 case JWTAlgorithm.RS256:
+                case JWTAlgorithm.PS256:
                     return signingCredentials.SignData(bytes);
 
                 default:

src/Sdk/WebApi/WebApi/VssSigningCredentials.cs

@@ -166,6 +166,21 @@ public override Int32 KeySize
                 }
             }
 
+            public override JWTAlgorithm SignatureAlgorithm
+            {
+                get
+                {
+                    if (m_signaturePadding == RSASignaturePadding.Pss)
+                    {
+                        return JWTAlgorithm.PS256;
+                    }
+                    else
+                    {
+                        return base.SignatureAlgorithm;
+                    }
+                }
+            }
+
             protected override Byte[] GetSignature(Byte[] input)
             {
                 using (var rsa = m_factory())