/// <inheritDoc/>
protected override Task <HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
{
// Add custom username header if it doesn't exist already.
if (!request.Headers.Contains(HmacApiAuthConfiguration.UsernameHeader))
{
request.Headers.Add(HmacApiAuthConfiguration.UsernameHeader, Username);
}
// Set the Date field in the header.
request.Headers.Date = DateTimeOffset.Now;
// Build out the string representation of the request.
var representation = _representationBuilder.BuildRequestRepresentation(request);
// Retrieve the user secret key from the secrets repository.
var secret = _secretRepository.GetSecretForUser(Username);
// Calculate the digital signature.
string signature = _signatureCalculator.Signature(secret, representation);
// Add signature to the header of the request message.
var header = new AuthenticationHeaderValue(HmacApiAuthConfiguration.AuthenticationScheme, signature);
request.Headers.Authorization = header;
// Call inner message handler for response.
return(base.SendAsync(request, cancellationToken));
}
/// <summary>
/// Validates the HMAC digital signature of the API request.
/// </summary>
/// <param name="requestMessage">The API request message to be validated for authenticity.</param>
/// <returns><c>true</c> if authenticated successfully, <c>false</c> otherwise.</returns>
protected async Task <bool> IsAuthenticated(HttpRequestMessage requestMessage)
{
// No username, no authentication.
if (!requestMessage.Headers.Contains(HmacApiAuthConfiguration.UsernameHeader))
{
return(false);
}
// No date, no authentication.
if (!IsDateValid(requestMessage))
{
return(false);
}
// No Authorization header or wrong type, no authentication.
if (requestMessage.Headers.Authorization == null ||
requestMessage.Headers.Authorization.Scheme != HmacApiAuthConfiguration.AuthenticationScheme)
{
return(false);
}
// No ContentMD5 header yet there is Content available, no authentication.
// No match between ContentMD5 header and actual Content MD5 hash, no authentication.
if (!await IsMd5Valid(requestMessage))
{
return(false);
}
// Using the user's key we will now calculate what the HMAC signature should be based on the provided request message.
// After building our own copy of the signature we will compare it to the signature provided in the API request.
// Retrieve the username and validate user has a registered key.
string username = requestMessage.Headers.GetValues(HmacApiAuthConfiguration.UsernameHeader).First();
var secret = _secretRepository.GetSecretForUser(username);
if (secret == null)
{
return(false);
}
// Build string representation of request. The client should have built their request the same way.
var representation = _representationBuilder.BuildRequestRepresentation(requestMessage);
if (representation == null)
{
return(false);
}
// Calculate our version of the HMAC signature and compare it to the request message signature to validate authentication.
var signature = _signatureCalculator.Signature(secret, representation);
var result = requestMessage.Headers.Authorization.Parameter == signature;
return(result);
}
protected override async Task <HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
string reqSignature = "";
HttpResponseMessage response = null;
// Get digital signature if available.
if (request.Headers?.Authorization != null && request.Headers?.Authorization.Scheme == HmacApiAuthConfiguration.AuthenticationScheme)
{
reqSignature = request.Headers.Authorization.Parameter;
}
else
{
// We should just return here if there is no signature.
return(request.CreateErrorResponse(HttpStatusCode.Unauthorized, "Unauthorized request : Missing or invalid signature"));
}
// TODO : Check to see if signature is currently in cache. If so return now.
// TODO : Cache signature in memory for the validity period (5 mins) to ensure no request gets replayed.
try
{
// Call the base authentication handler.
response = await base.SendAsync(request, cancellationToken);
}
catch (Exception exception)
{
// Catch any authentication error messages and provide custom error message response.
response = request.CreateErrorResponse(HttpStatusCode.InternalServerError, "Error authenticating");
var respMsg = new StringBuilder();
respMsg.AppendLine("Error authenticating...");
respMsg.AppendLine("StatusCode : " + response.StatusCode);
respMsg.AppendLine("ReasonPhrase : " + response.ReasonPhrase);
respMsg.AppendLine("WwwAuthenticate : " + response.Headers.WwwAuthenticate.FirstOrDefault().ToString());
respMsg.AppendLine("RequestDate : " + request.Headers.Date.GetValueOrDefault().UtcDateTime.ToString(CultureInfo.InvariantCulture));
respMsg.AppendLine("ServerDate : " + (DateTimeOffset.Now));
respMsg.AppendLine();
respMsg.AppendLine("ExceptionMessage : " + exception.Message);
respMsg.AppendLine("ExceptionSource : " + exception.Source);
respMsg.AppendLine("ExceptionInnerMessage : " + exception.InnerException?.Message);
respMsg.AppendLine("ExceptionStackTrace : " + exception.StackTrace);
response.Content = new StringContent(respMsg.ToString());
}
// Catch any authentication failure message and provide custom error message response.
if (response != null && response.StatusCode == HttpStatusCode.Unauthorized)
{
var serverDate = DateTimeOffset.Now;
var respMsg = new StringBuilder();
respMsg.AppendLine("Authentication failed");
respMsg.AppendLine();
respMsg.AppendLine("Basic Details\n");
respMsg.AppendLine("URL : " + request.RequestUri.AbsoluteUri.ToLower());
respMsg.AppendLine("StatusCode : " + response.StatusCode);
respMsg.AppendLine("ReasonPhrase : " + response.ReasonPhrase);
//respMsg.AppendLine("WwwAuthenticate : " + response.Headers.WwwAuthenticate.FirstOrDefault().ToString());
respMsg.AppendLine("RequestDate : " + request.Headers.Date.GetValueOrDefault().ToString("r"));
respMsg.AppendLine("ServerDate : " + serverDate.ToString("r"));
respMsg.AppendLine("DateDifference : " + (serverDate - request.Headers.Date.GetValueOrDefault()));
respMsg.AppendLine();
string username = "";
if (request.Headers.Contains(HmacApiAuthConfiguration.UsernameHeader))
{
username = request.Headers.GetValues(HmacApiAuthConfiguration.UsernameHeader).First();
}
string signature = "";
if (request.Headers.Authorization != null && request.Headers.Authorization.Scheme == HmacApiAuthConfiguration.AuthenticationScheme)
{
signature = request.Headers.Authorization.Parameter;
}
string md5 = "";
string serverMd5 = "";
long? contentLength = 0;
if (request.Content != null)
{
contentLength = request.Content.Headers.ContentLength;
serverMd5 = Convert.ToBase64String(await MD5Helper.ComputeHash(request.Content)) == "1B2M2Y8AsgTpgAmY7PhCfg==" ? "" : Convert.ToBase64String(await MD5Helper.ComputeHash(request.Content));
if (request.Content.Headers.ContentMD5 != null && request.Content.Headers.ContentMD5.Length > 0)
{
md5 = Convert.ToBase64String(request.Content.Headers.ContentMD5);
}
}
bool validRequest = IsRequestValid(request);
string msgSigRep = _representBuilder.BuildRequestRepresentation(request);
string serverSignature = _sigCalc.Signature(_secretRepo.GetSecretForUser(username), msgSigRep);
respMsg.AppendLine("Auth Details\n");
respMsg.AppendLine("RequestValid : " + validRequest.ToString());
respMsg.AppendLine("Username : "******"ApiKey : " + _secretRepo.GetSecretForUser(username));
respMsg.AppendLine("Signature : " + signature);
respMsg.AppendLine("ServerSignature : " + serverSignature);
respMsg.AppendLine();
respMsg.AppendLine("Content Details\n");
respMsg.AppendLine("ContentMd5 : " + md5);
respMsg.AppendLine("ServerContentMd5 : " + serverMd5);
respMsg.AppendLine("CannonicalRep :\n" + msgSigRep);
respMsg.AppendLine("ContentLength : " + contentLength);
respMsg.AppendLine("ContentType : " + request.Content.Headers.ContentType);
respMsg.AppendLine("ContentMediaType : " + request.Content.Headers.ContentType.MediaType.ToLower());
respMsg.AppendLine("Content : \"" + await request.Content.ReadAsStringAsync() + "\"");
response.Content = new StringContent(respMsg.ToString());
}
return(response);
}
