/// <summary>
/// Deserializes an endpoint from an address book entry and validates that the signatures are correct.
/// </summary>
/// <returns>The deserialized endpoint.</returns>
/// <exception cref="BadAddressBookEntryException">Thrown if the signatures are invalid.</exception>
public Endpoint ExtractEndpoint()
{
var reader = new BinaryReader(new MemoryStream(this.SerializedEndpoint));
Endpoint endpoint;
try
{
endpoint = reader.DeserializeDataContract <Endpoint>();
}
catch (SerializationException ex)
{
throw new BadAddressBookEntryException(ex.Message, ex);
}
try
{
if (!CryptoProviderExtensions.VerifySignatureWithTolerantHashAlgorithm(endpoint.SigningKeyPublicMaterial, this.SerializedEndpoint, this.Signature, this.HashAlgorithmName != null ? (AsymmetricAlgorithm?)CryptoProviderExtensions.GetSignatureProvider(this.HashAlgorithmName) : null))
{
throw new BadAddressBookEntryException(Strings.AddressBookEntrySignatureDoesNotMatch);
}
}
catch (Exception ex)
{ // all those platform-specific exceptions that aren't available to portable libraries.
throw new BadAddressBookEntryException(Strings.AddressBookEntrySignatureDoesNotMatch, ex);
}
return(endpoint);
}
/// <summary>
/// Downloads the endpoint described by the address book entry found at the given URL and verifies the signature.
/// </summary>
/// <param name="entryLocation">The entry location.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>A task whose result is the endpoint described and signed by the address book entry.</returns>
/// <exception cref="BadAddressBookEntryException">Thrown when deserialization or signature verification of the address book entry fails.</exception>
protected async Task <Endpoint> DownloadEndpointAsync(Uri entryLocation, CancellationToken cancellationToken)
{
Requires.NotNull(entryLocation, "entryLocation");
var entry = await this.DownloadAddressBookEntryAsync(entryLocation, cancellationToken).ConfigureAwait(false);
if (entry == null)
{
return(null);
}
var endpoint = entry.ExtractEndpoint();
if (!string.IsNullOrEmpty(entryLocation.Fragment))
{
if (!CryptoProviderExtensions.IsThumbprintMatch(endpoint.SigningKeyPublicMaterial, entryLocation.Fragment.Substring(1)))
{
throw new BadAddressBookEntryException("Fragment thumbprint mismatch.");
}
}
return(endpoint);
}
/// <summary>
/// Downloads a <see cref="PayloadReference"/> that is referenced from an incoming inbox item.
/// </summary>
/// <param name="inboxItem">The inbox item that referenced the <see cref="PayloadReference"/>.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>The task representing the asynchronous operation.</returns>
protected virtual async Task <PayloadReference> DownloadPayloadReferenceAsync(IncomingList.IncomingItem inboxItem, CancellationToken cancellationToken)
{
Requires.NotNull(inboxItem, "inboxItem");
var responseMessage = await this.HttpClient.GetAsync(inboxItem.Location, cancellationToken).ConfigureAwait(false);
if (responseMessage.StatusCode == HttpStatusCode.NotFound)
{
// delete inbox item and move on.
await this.DeletePayloadReferenceAsync(inboxItem.Location, cancellationToken).ConfigureAwait(false);
this.Log("Missing payload reference.", null);
return(null);
}
responseMessage.EnsureSuccessStatusCode();
var responseStream = await responseMessage.Content.ReadAsStreamAsync().ConfigureAwait(false);
var responseStreamCopy = new MemoryStream();
await responseStream.CopyToAsync(responseStreamCopy, 4096, cancellationToken).ConfigureAwait(false);
responseStreamCopy.Position = 0;
var encryptedKey = await responseStreamCopy.ReadSizeAndBufferAsync(cancellationToken).ConfigureAwait(false);
var key = WinRTCrypto.CryptographicEngine.Decrypt(this.Endpoint.EncryptionKey, encryptedKey);
var iv = await responseStreamCopy.ReadSizeAndBufferAsync(cancellationToken).ConfigureAwait(false);
var ciphertextStream = await responseStreamCopy.ReadSizeAndStreamAsync(cancellationToken).ConfigureAwait(false);
var encryptedVariables = new SymmetricEncryptionVariables(key, iv);
var plainTextPayloadStream = new MemoryStream();
await this.CryptoServices.DecryptAsync(ciphertextStream, plainTextPayloadStream, encryptedVariables, cancellationToken).ConfigureAwait(false);
plainTextPayloadStream.Position = 0;
AsymmetricAlgorithm?signingHashAlgorithm = null; //// Encoding.UTF8.GetString(await plainTextPayloadStream.ReadSizeAndBufferAsync(cancellationToken));
byte[] signature = await plainTextPayloadStream.ReadSizeAndBufferAsync(cancellationToken).ConfigureAwait(false);
long payloadStartPosition = plainTextPayloadStream.Position;
var signedBytes = new byte[plainTextPayloadStream.Length - plainTextPayloadStream.Position];
await plainTextPayloadStream.ReadAsync(signedBytes, 0, signedBytes.Length).ConfigureAwait(false);
plainTextPayloadStream.Position = payloadStartPosition;
var plainTextPayloadReader = new BinaryReader(plainTextPayloadStream);
var recipientPublicSigningKeyBuffer = plainTextPayloadReader.ReadSizeAndBuffer();
var creationDateUtc = DateTime.FromBinary(plainTextPayloadReader.ReadInt64());
var notificationAuthor = Utilities.DeserializeDataContract <Endpoint>(plainTextPayloadReader);
var messageReference = Utilities.DeserializeDataContract <PayloadReference>(plainTextPayloadReader);
messageReference.ReferenceLocation = inboxItem.Location;
if (messageReference.HashAlgorithmName == null)
{
messageReference.HashAlgorithmName = Utilities.GuessHashAlgorithmFromLength(messageReference.Hash.Length).GetHashAlgorithmName();
}
if (!CryptoProviderExtensions.VerifySignatureWithTolerantHashAlgorithm(notificationAuthor.SigningKeyPublicMaterial, signedBytes, signature, signingHashAlgorithm))
{
throw new InvalidMessageException();
}
if (!Utilities.AreEquivalent(recipientPublicSigningKeyBuffer, this.Endpoint.PublicEndpoint.SigningKeyPublicMaterial))
{
throw new InvalidMessageException(Strings.MisdirectedMessage);
}
return(messageReference);
}
/// <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);
}
