public async Task EnvelopeAsync(byte[] unencryptedBytes, int symmetricKeySizeBits, int symmetricInitializationVectorSizeBits, Stream encryptedOutputStream, CancellationToken cancellationToken)
{
try
{
AmazonS3Credentials kmsCredentials = await GetCredentialsAsync();
if (symmetricKeySizeBits != 256)
{
throw new ArgumentOutOfRangeException(nameof(symmetricKeySizeBits), "Invalid value " + symmetricKeySizeBits + ". Only 256-bit keys are supported.");
}
if (symmetricInitializationVectorSizeBits != 128)
{
throw new ArgumentOutOfRangeException(nameof(symmetricInitializationVectorSizeBits), "Invalid value " + symmetricInitializationVectorSizeBits + ". Only 128-bit initialization vectors are supported.");
}
AmazonKeyManagementServiceClient kmsClient = new AmazonKeyManagementServiceClient(kmsCredentials.AccessKeyId, kmsCredentials.SecretAccessKey, kmsCredentials.SessionToken, kmsCredentials.RegionEndpoint);
// generate a symmetric data key
GenerateDataKeyResponse dataKeyResponse = await kmsClient.GenerateDataKeyAsync(new GenerateDataKeyRequest
{
KeyId = kmsCredentials.CustomerMasterKey,
KeySpec = DataKeySpec.AES_256
}, cancellationToken);
// write encrypted payload
// write encrypted data key length and bytes
byte[] encryptedDataKeyBytes = dataKeyResponse.CiphertextBlob.ToArray();
byte[] encryptedDataKeyBytesLength = BitConverter.GetBytes(encryptedDataKeyBytes.Length);
encryptedOutputStream.Write(encryptedDataKeyBytesLength, 0, encryptedDataKeyBytesLength.Length);
encryptedOutputStream.Write(encryptedDataKeyBytes, 0, encryptedDataKeyBytes.Length);
// write encrypted random initialization vector length and bytes
Random random = new Random();
byte[] initializationVectorBytes = new byte[16];
random.NextBytes(initializationVectorBytes);
byte[] encryptedInitializationVectorBytes = (await kmsClient.EncryptAsync(new EncryptRequest
{
KeyId = kmsCredentials.CustomerMasterKey,
Plaintext = new MemoryStream(initializationVectorBytes)
}, cancellationToken)).CiphertextBlob.ToArray();
byte[] encryptedInitializationVectorBytesLength = BitConverter.GetBytes(encryptedInitializationVectorBytes.Length);
encryptedOutputStream.Write(encryptedInitializationVectorBytesLength, 0, encryptedInitializationVectorBytesLength.Length);
encryptedOutputStream.Write(encryptedInitializationVectorBytes, 0, encryptedInitializationVectorBytes.Length);
// write symmetrically encrypted bytes
byte[] dataKeyBytes = dataKeyResponse.Plaintext.ToArray();
SymmetricEncryption symmetricEncryption = new SymmetricEncryption(dataKeyBytes, initializationVectorBytes);
byte[] encryptedBytes = symmetricEncryption.Encrypt(unencryptedBytes);
encryptedOutputStream.Write(encryptedBytes, 0, encryptedBytes.Length);
}
// the following catch statements attempt to filter out expected exceptions (e.g., due to naturally lacking internet connections)
// from those that are fixable errors within the app. expected exceptions are logged but not reported to the app center, whereas
// all others are reported to the app center. our approach is to whitelist excepted exceptions as we see them appear in the app
// center, in order to ensure that we don't miss any fixable errors.
catch (HttpRequestException ex)
{
bool logged = false;
if (ex.InnerException is WebException)
{
WebException webException = ex.InnerException as WebException;
if (IGNORED_WEB_EXCEPTION_STATUSES.Contains(webException.Status))
{
LogKmsEnvelopeException(ex);
logged = true;
}
}
if (!logged)
{
ReportKmsEnvelopeException(ex);
}
throw ex;
}
catch (WebException webException)
{
if (IGNORED_WEB_EXCEPTION_STATUSES.Contains(webException.Status))
{
LogKmsEnvelopeException(webException);
}
else
{
ReportKmsEnvelopeException(webException);
}
throw webException;
}
catch (OperationCanceledException ex)
{
LogKmsEnvelopeException(ex);
throw ex;
}
catch (Exception ex)
{
ReportKmsEnvelopeException(ex);
throw ex;
}
}
public Task <AmazonS3Credentials> GetCredentialsAsync()
{
lock (_getCredentialsTaskLocker)
{
// if the get credentials task is in a state from which we wouldn't expect to return a presently
// valid set of credentials, then start a new task to check/refresh the credentials.
if (_getCredentialsTask == null ||
_getCredentialsTask.Status == TaskStatus.Canceled ||
_getCredentialsTask.Status == TaskStatus.Faulted ||
_getCredentialsTask.Status == TaskStatus.RanToCompletion)
{
_getCredentialsTask = Task.Run(async() =>
{
// if the credentials we currently hold will be valid for a while, then simply return them.
if (AmazonS3Credentials?.WillBeValidFor(TimeSpan.FromHours(1)) ?? false)
{
return(AmazonS3Credentials);
}
else
{
AmazonS3Credentials = null;
}
// we should always have an account
if (Account == null)
{
Exception noAccountException = new Exception("Tried to get credentials without an account.");
SensusException.Report(noAccountException);
throw noAccountException;
}
string credentialsJSON = await new Uri(string.Format(_getCredentialsURL, Account.ParticipantId, Account.Password, SensusServiceHelper.Get().DeviceId)).DownloadStringAsync();
// deserialize credentials
try
{
AmazonS3Credentials = credentialsJSON.DeserializeJson <AmazonS3Credentials>();
}
catch (Exception ex)
{
SensusException.Report("Exception while deserializing AWS S3 credentials.", ex);
throw ex;
}
// check properties. trim while we're at it.
if (string.IsNullOrWhiteSpace(AmazonS3Credentials.AccessKeyId = AmazonS3Credentials.AccessKeyId?.Trim()))
{
SensusException.Report("Empty " + nameof(AmazonS3Credentials.AccessKeyId) + " returned by authentication service for participant " + (Account.ParticipantId ?? "[null]."));
}
if (string.IsNullOrWhiteSpace(AmazonS3Credentials.CustomerMasterKey = AmazonS3Credentials.CustomerMasterKey?.Trim()))
{
SensusException.Report("Empty " + nameof(AmazonS3Credentials.CustomerMasterKey) + " returned by authentication service for participant " + (Account.ParticipantId ?? "[null]."));
}
if (string.IsNullOrWhiteSpace(AmazonS3Credentials.ExpirationUnixTimeMilliseconds = AmazonS3Credentials.ExpirationUnixTimeMilliseconds?.Trim()))
{
SensusException.Report("Empty " + nameof(AmazonS3Credentials.ExpirationUnixTimeMilliseconds) + " returned by authentication service for participant " + (Account.ParticipantId ?? "[null]."));
}
if (string.IsNullOrWhiteSpace(AmazonS3Credentials.ProtocolId = AmazonS3Credentials.ProtocolId?.Trim()))
{
SensusException.Report("Empty " + nameof(AmazonS3Credentials.ProtocolId) + " returned by authentication service for participant " + (Account.ParticipantId ?? "[null]."));
}
if (string.IsNullOrWhiteSpace(AmazonS3Credentials.ProtocolURL = AmazonS3Credentials.ProtocolURL?.Trim()))
{
SensusException.Report("Empty " + nameof(AmazonS3Credentials.ProtocolURL) + " returned by authentication service for participant " + (Account.ParticipantId ?? "[null]."));
}
if (string.IsNullOrWhiteSpace(AmazonS3Credentials.Region = AmazonS3Credentials.Region?.Trim()))
{
SensusException.Report("Empty " + nameof(AmazonS3Credentials.Region) + " returned by authentication service for participant " + (Account.ParticipantId ?? "[null]."));
}
if (string.IsNullOrWhiteSpace(AmazonS3Credentials.SecretAccessKey = AmazonS3Credentials.SecretAccessKey?.Trim()))
{
SensusException.Report("Empty " + nameof(AmazonS3Credentials.SecretAccessKey) + " returned by authentication service for participant " + (Account.ParticipantId ?? "[null]."));
}
if (string.IsNullOrWhiteSpace(AmazonS3Credentials.SessionToken = AmazonS3Credentials.SessionToken?.Trim()))
{
SensusException.Report("Empty " + nameof(AmazonS3Credentials.SessionToken) + " returned by authentication service for participant " + (Account.ParticipantId ?? "[null]."));
}
// save the app state to hang on to the credentials
await SensusServiceHelper.Get().SaveAsync();
return(AmazonS3Credentials);
});
}
return(_getCredentialsTask);
}
}