iothub/device/src/Authentication/ModuleAuthenticationWithSakRefresh.cs

// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System;
using System.Net;
using System.Threading.Tasks;
using Microsoft.Azure.Devices.Client.Extensions;

namespace Microsoft.Azure.Devices.Client
{
    // Implementing SAS Token refresh based on a SharedAccessKey (SAK).
    internal class ModuleAuthenticationWithSakRefresh : ModuleAuthenticationWithTokenRefresh
    {
        private readonly IotHubConnectionString _connectionString;

        public ModuleAuthenticationWithSakRefresh(
            string deviceId,
            string moduleId,
            IotHubConnectionString connectionString)
            : base(deviceId, moduleId)
        {
            _connectionString = connectionString ?? throw new ArgumentNullException(nameof(connectionString));
        }

        internal ModuleAuthenticationWithSakRefresh(
            string deviceId,
            string moduleId,
            IotHubConnectionString connectionString,
            TimeSpan sasTokenTimeToLive,
            int sasTokenRenewalBuffer,
            bool disposeWithClient)
            : base(deviceId, moduleId, (int)sasTokenTimeToLive.TotalSeconds, sasTokenRenewalBuffer, disposeWithClient)
        {
            _connectionString = connectionString ?? throw new ArgumentNullException(nameof(connectionString));
        }

        ///<inheritdoc/>
        protected override Task<string> SafeCreateNewToken(string iotHub, int suggestedTimeToLive)
        {
            var builder = new SharedAccessSignatureBuilder()
            {
                Key = _connectionString.SharedAccessKey,
                TimeToLive = TimeSpan.FromSeconds(suggestedTimeToLive),
            };

            if (_connectionString.SharedAccessKeyName == null)
            {
                builder.Target = "{0}/devices/{1}/modules/{2}".FormatInvariant(
                    iotHub,
                    WebUtility.UrlEncode(DeviceId),
                    WebUtility.UrlEncode(ModuleId));
            }
            else
            {
                builder.KeyName = _connectionString.SharedAccessKeyName;
                builder.Target = _connectionString.Audience;
            }

            return Task.FromResult(builder.ToSignature());
        }
    }
}