public static WebRequest Build(CacheInvalidationRequestModel request)
{
string hashedRequestPayload = CreateRequestPayload(String.Empty);
string authorization = Sign(request, hashedRequestPayload, "GET", request.AbsolutePath, request.QueryString);
string requestDate = DateTime.UtcNow.ToString(DateTimeFormat);
var webRequest = WebRequest.Create($"https://{request.Host}{request.AbsolutePath}");
webRequest.Method = "GET";
webRequest.ContentType = ContentType;
webRequest.Headers.Add("Cache-Control", "max-age=0");
webRequest.Headers.Add("Host", request.Host);
webRequest.Headers.Add("X-Amz-Date", requestDate);
webRequest.Headers.Add("Authorization", authorization);
return(webRequest);
}
private static string Sign(CacheInvalidationRequestModel request, string hashedRequestPayload, string requestMethod, string canonicalUri, string canonicalQueryString)
{
var currentDateTime = DateTime.UtcNow;
var dateStamp = currentDateTime.ToString(DateFormat);
var requestDate = currentDateTime.ToString(DateTimeFormat);
var credentialScope = $"{dateStamp}/{request.Region}/{ServiceName}/aws4_request";
var headers = new SortedDictionary <string, string> {
{ "cache-control", "max-age=0" },
{ "content-type", ContentType },
{ "host", request.Host },
{ "x-amz-date", requestDate }
};
var canonicalHeaders = string.Join("\n", headers.Select(x => x.Key.ToLowerInvariant() + ":" + x.Value.Trim())) + "\n";
// Task 1: Create a Canonical Request For Signature Version 4
var SignedHeaders = String.Join(';', headers.Select(x => x.Key.ToLowerInvariant()));
var canonicalRequest = $"{requestMethod}\n{canonicalUri}\n{canonicalQueryString}\n{canonicalHeaders}\n{SignedHeaders}\n{hashedRequestPayload}";
var hashedCanonicalRequest = HexEncode(Hash(ToBytes(canonicalRequest)));
// Task 2: Create a String to Sign for Signature Version 4
var stringToSign = $"{Algorithm}\n{requestDate}\n{credentialScope}\n{hashedCanonicalRequest}";
// Task 3: Calculate the AWS Signature Version 4
var signingKey = GetSignatureKey(request.SecretKey, dateStamp, request.Region, ServiceName);
var signature = HexEncode(HmacSha256(stringToSign, signingKey));
// Task 4: Prepare a signed request
// Authorization: algorithm Credential=access key ID/credential scope, SignedHeadaers=SignedHeaders, Signature=signature
var authorization = $"{Algorithm} Credential={request.AccessKey}/{dateStamp}/{request.Region}/{ServiceName}/aws4_request, SignedHeaders={SignedHeaders}, Signature={signature}";
return(authorization);
}