public AuthenticationHeaderValue CalculateAuthorizationHeaderValue(HttpMethod httpMethod, string url, DateTime date, IDictionary <string, string> httpHeaders)
{
string signedHeaders;
var canonicalRequestHash = CalculateCanonicalRequestHash(httpMethod, url, httpHeaders, out signedHeaders);
var signingKey = CalculateSigningKey(date, ServiceName);
using (var hash = new HMACSHA256(signingKey))
{
var scope = $"{date:yyyyMMdd}/{AwsRegion}/{ServiceName}/aws4_request";
var stringToHash = $"AWS4-HMAC-SHA256\n{RavenAwsHelper.ConvertToString(date)}\n{scope}\n{canonicalRequestHash}";
var hashedString = hash.ComputeHash(Encoding.UTF8.GetBytes(stringToHash));
var signature = RavenAwsHelper.ConvertToHex(hashedString);
var credentials = $"{_awsAccessKey}/{date:yyyyMMdd}/{AwsRegion}/{ServiceName}/aws4_request";
return(new AuthenticationHeaderValue("AWS4-HMAC-SHA256", $"Credential={credentials},SignedHeaders={signedHeaders},Signature={signature}"));
}
}
private static string CalculateCanonicalRequestHash(HttpMethod httpMethod, string url, IDictionary <string, string> httpHeaders, out string signedHeaders)
{
var isGet = httpMethod == HttpMethods.Get;
var uri = new Uri(url);
var canonicalUri = uri.AbsolutePath;
var query = QueryHelpers.ParseQuery(uri.Query);
var canonicalQueryString = query
.OrderBy(parameter => parameter.Key)
.Select(parameter => parameter.Value.Aggregate((current, value) => current + $"{parameter.Key}={value.Trim()}&"))
.Aggregate(string.Empty, (current, parameter) => current + parameter);
if (canonicalQueryString.EndsWith("&"))
{
canonicalQueryString = canonicalQueryString.Substring(0, canonicalQueryString.Length - 1);
}
var headers = httpHeaders
.Where(x => isGet == false || x.Key.StartsWith("Date", StringComparison.OrdinalIgnoreCase) == false)
.OrderBy(x => x.Key);
var canonicalHeaders = headers
.Aggregate(string.Empty, (current, parameter) => current + $"{parameter.Key.ToLower()}:{parameter.Value.Trim()}\n");
signedHeaders = headers
.Aggregate(string.Empty, (current, parameter) => current + parameter.Key.ToLower() + ";");
if (signedHeaders.EndsWith(";"))
{
signedHeaders = signedHeaders.Substring(0, signedHeaders.Length - 1);
}
using (var hash = SHA256.Create())
{
var hashedPayload = httpHeaders["x-amz-content-sha256"];
var canonicalRequest = $"{httpMethod}\n{canonicalUri}\n{canonicalQueryString}\n{canonicalHeaders}\n{signedHeaders}\n{hashedPayload}";
return(RavenAwsHelper.ConvertToHex(hash.ComputeHash(Encoding.UTF8.GetBytes(canonicalRequest))));
}
}
