Question/bug: Deal with objects with byte arrays

Hi,

We’ve got a bug with an object that has a JsonWebKey property.

The JsonWebKey payload returned from the external service seems to show byte arrays as strings (check the payload example). Autorest tries to deserialize the property with the Window.atob method and we get the following deserialization error:

Error: Error InvalidCharacterError: Failed to execute 'atob' on 'Window': 
The string to be decoded is not correctly encoded. occurred in deserializing the responseBody

We could mitigate the problem by nullyfing the key itself since we don’t need in the service that consumes the object. At this point, we have the following constraints:

• We can’t modify the JsonWebKey (C#) itself since it comes from a MS library;
• Maybe we’re missing something in our Swagger document;
• Maybe there is a special switch that we are not aware of for the code generation with Autorest;

Thanks in advance for your help 😄

JsonWebKey payload example:

{"kty":"RSA","n":"3Ab3gTAExSETjhzhcqKI8vxaQguel5ICr-MQA_AlwxfoOd_tgpGbI9WEG3A7b9txjlNDrYD-5_GW9Y_ls5e2X-XUvrg9Bhn91j3kX7lqUssE4Ht0yk8Ua4i4fkNrPuPg9_RhBK4je4NetPChG9potyMMGDTMDfzimseZ6r-xuvMDwMmlvOtEH_vQBckLag3Tf11_wruVA697ZYqskfYPFG-zIQzmQRR6_-qBPmU6033xSWRgyZ6FeOB6lCW16O6UvLVOZnMwkS3IO6_q7RHLXT0_ucM1xIWs18X9S9-3bVg8inFKRNrUEbFRbt6O2rzzPZw8sRHiCcMBAj7SteqWOQ","e":"AQAB"}

Swagger definition (swagger.json)

JsonWebKey interface (Typescript)

**
 * @interface
 * An interface representing JsonWebKey.
 */
export interface JsonWebKey {
  /**
   * @member {string} [kid]
   */
  kid?: string;
  /**
   * @member {string} kty
   */
  kty: string;
  /**
   * @member {string[]} [keyOps]
   */
  keyOps?: string[];
  /**
   * @member {Uint8Array} [n]
   */
  n?: Uint8Array;
  /**
   * @member {Uint8Array} [e]
   */
  e?: Uint8Array;
  /**
   * @member {Uint8Array} [d]
   */
  d?: Uint8Array;
  /**
   * @member {Uint8Array} [dp]
   */
  dp?: Uint8Array;
  /**
   * @member {Uint8Array} [dq]
   */
  dq?: Uint8Array;
  /**
   * @member {Uint8Array} [qi]
   */
  qi?: Uint8Array;
  /**
   * @member {Uint8Array} [p]
   */
  p?: Uint8Array;
  /**
   * @member {Uint8Array} [q]
   */
  q?: Uint8Array;
  /**
   * @member {Uint8Array} [k]
   */
  k?: Uint8Array;
  /**
   * @member {Uint8Array} [keyHsm]
   */
  keyHsm?: Uint8Array;
}

JsonWebKey mapper (Typescript)

export const JsonWebKey = {
  serializedName: "JsonWebKey",
  type: {
    name: "Composite",
    className: "JsonWebKey",
    modelProperties: {
      kid: {
        serializedName: "kid",
        type: {
          name: "String"
        }
      },
      kty: {
        required: true,
        serializedName: "kty",
        type: {
          name: "String"
        }
      },
      keyOps: {
        serializedName: "key_ops",
        type: {
          name: "Sequence",
          element: {
            serializedName: "stringElementType",
            type: {
              name: "String"
            }
          }
        }
      },
      n: {
        serializedName: "n",
        type: {
          name: "ByteArray"
        }
      },
      e: {
        serializedName: "e",
        type: {
          name: "ByteArray"
        }
      },
      d: {
        serializedName: "d",
        type: {
          name: "ByteArray"
        }
      },
      dp: {
        serializedName: "dp",
        type: {
          name: "ByteArray"
        }
      },
      dq: {
        serializedName: "dq",
        type: {
          name: "ByteArray"
        }
      },
      qi: {
        serializedName: "qi",
        type: {
          name: "ByteArray"
        }
      },
      p: {
        serializedName: "p",
        type: {
          name: "ByteArray"
        }
      },
      q: {
        serializedName: "q",
        type: {
          name: "ByteArray"
        }
      },
      k: {
        serializedName: "k",
        type: {
          name: "ByteArray"
        }
      },
      keyHsm: {
        serializedName: "key_hsm",
        type: {
          name: "ByteArray"
        }
      }
    }
  }
};

[Eric-Bonneau]

If anyone encounters this issue using Swashbuckle in the future, you can introduce an ISchemaFilter for JsonWebKey. That way you can apply a format to the properties with base64 URL encoding after Swashbuckle has already generated the schema.

Something like this (note I’m using Swashbuckle.AspNetCore v3.0.0 and the API may be different in a later version):

public class JsonWebKeyFilter : ISchemaFilter
{
    public void Apply(Schema schema, SchemaFilterContext context)
    {
        if (context.SystemType == typeof(JsonWebKey))
        {
            schema.Properties["n"].Format = "base64url";
            // do the same thing for the other properties
        }
    }
}

The problem is that the JsonWebKey class has custom JSON converters for several properties and AutoRest doesn’t know about them. So if you introduce a filter like above, you can override the schema generated by Swashbuckle so that way AutoRest knows how to (de)serialize those properties.

[ffMathy]

@RikkiGibson this is still an issue.