/// <summary>
/// Downloads the message payload referred to by the specified <see cref="PayloadReference"/>.
/// </summary>
/// <param name="notification">The payload reference.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>The task representing the asynchronous operation.</returns>
public virtual async Task <Payload> DownloadPayloadAsync(PayloadReference notification, CancellationToken cancellationToken = default(CancellationToken))
{
Requires.NotNull(notification, "notification");
byte[] messageBuffer = null;
const int MaxAttempts = 2;
int retry;
Exception exceptionLeadingToRetry = null;
for (retry = 0; retry < MaxAttempts; retry++)
{
exceptionLeadingToRetry = null;
try
{
var responseMessage = await this.HttpClient.GetAsync(notification.Location, cancellationToken).ConfigureAwait(false);
messageBuffer = await responseMessage.Content.ReadAsByteArrayAsync().ConfigureAwait(false);
// Calculate hash of downloaded message and check that it matches the referenced message hash.
if (!this.CryptoServices.IsHashMatchWithTolerantHashAlgorithm(messageBuffer, notification.Hash, CryptoProviderExtensions.ParseHashAlgorithmName(notification.HashAlgorithmName)))
{
// Sometimes when the hash mismatches, it's because the download was truncated
// (from switching out the application and then switching back, for example).
// Check for that before throwing.
if (responseMessage.Content.Headers.ContentLength.HasValue && responseMessage.Content.Headers.ContentLength.Value > messageBuffer.Length)
{
// It looks like the message was truncated. Retry.
exceptionLeadingToRetry = new InvalidMessageException();
continue;
}
throw new InvalidMessageException();
}
// Stop retrying. We got something that worked!
break;
}
catch (HttpRequestException ex)
{
exceptionLeadingToRetry = ex;
continue;
}
}
if (exceptionLeadingToRetry != null)
{
if (exceptionLeadingToRetry.StackTrace != null)
{
ExceptionDispatchInfo.Capture(exceptionLeadingToRetry).Throw();
}
else
{
throw exceptionLeadingToRetry;
}
}
var encryptionVariables = new SymmetricEncryptionVariables(notification.Key, notification.IV);
var cipherStream = new MemoryStream(messageBuffer);
var plainTextStream = new MemoryStream();
await this.CryptoServices.DecryptAsync(cipherStream, plainTextStream, encryptionVariables, cancellationToken).ConfigureAwait(false);
plainTextStream.Position = 0;
var plainTextReader = new BinaryReader(plainTextStream);
var message = Utilities.DeserializeDataContract <Payload>(plainTextReader);
message.PayloadReferenceUri = notification.ReferenceLocation;
return(message);
}
/// <summary>
/// Downloads the message payload referred to by the specified <see cref="PayloadReference"/>.
/// </summary>
/// <param name="notification">The payload reference.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>The task representing the asynchronous operation.</returns>
public virtual async Task<Payload> DownloadPayloadAsync(PayloadReference notification, CancellationToken cancellationToken = default(CancellationToken))
{
Requires.NotNull(notification, "notification");
byte[] messageBuffer = null;
const int MaxAttempts = 2;
int retry;
Exception exceptionLeadingToRetry = null;
for (retry = 0; retry < MaxAttempts; retry++)
{
exceptionLeadingToRetry = null;
try
{
var responseMessage = await this.HttpClient.GetAsync(notification.Location, cancellationToken).ConfigureAwait(false);
messageBuffer = await responseMessage.Content.ReadAsByteArrayAsync().ConfigureAwait(false);
// Calculate hash of downloaded message and check that it matches the referenced message hash.
if (!this.CryptoServices.IsHashMatchWithTolerantHashAlgorithm(messageBuffer, notification.Hash, CryptoProviderExtensions.ParseHashAlgorithmName(notification.HashAlgorithmName)))
{
// Sometimes when the hash mismatches, it's because the download was truncated
// (from switching out the application and then switching back, for example).
// Check for that before throwing.
if (responseMessage.Content.Headers.ContentLength.HasValue && responseMessage.Content.Headers.ContentLength.Value > messageBuffer.Length)
{
// It looks like the message was truncated. Retry.
exceptionLeadingToRetry = new InvalidMessageException();
continue;
}
throw new InvalidMessageException();
}
// Stop retrying. We got something that worked!
break;
}
catch (HttpRequestException ex)
{
exceptionLeadingToRetry = ex;
continue;
}
}
if (exceptionLeadingToRetry != null)
{
if (exceptionLeadingToRetry.StackTrace != null)
{
ExceptionDispatchInfo.Capture(exceptionLeadingToRetry).Throw();
}
else
{
throw exceptionLeadingToRetry;
}
}
var encryptionVariables = new SymmetricEncryptionVariables(notification.Key, notification.IV);
var cipherStream = new MemoryStream(messageBuffer);
var plainTextStream = new MemoryStream();
await this.CryptoServices.DecryptAsync(cipherStream, plainTextStream, encryptionVariables, cancellationToken).ConfigureAwait(false);
plainTextStream.Position = 0;
var plainTextReader = new BinaryReader(plainTextStream);
var message = Utilities.DeserializeDataContract<Payload>(plainTextReader);
message.PayloadReferenceUri = notification.ReferenceLocation;
return message;
}
