Amazon Web service - signature - amazon-web-services

Question

I've been receiving an error from Amazon web service - InvalidParameterValue
Either Action or Operation query parameter must be present.
I believe it is most likely due to the signature being incorrect as the XML document and Header matches that of a test I did in their scratchpad.
Does anything stand out as being incorrect?
Thanks,
Clare
private static string ConstructCanonicalQueryString(SortedDictionary<string, string> sortedParameters)
{
var builder = new StringBuilder();
if (sortedParameters.Count == 0)
{
builder.Append(string.Empty);
return builder.ToString();
}
foreach (var kvp in sortedParameters)
{
builder.Append(PercentEncodeRfc3986(kvp.Key));
builder.Append("=");
builder.Append(PercentEncodeRfc3986(kvp.Value));
builder.Append("&");
}
var canonicalString = builder.ToString();
return canonicalString.Substring(0, canonicalString.Length - 1);
}
private static string PercentEncodeRfc3986(string value)
{
value = HttpUtility.UrlEncode(string.IsNullOrEmpty(value) ? string.Empty : value, Encoding.UTF8);
if (string.IsNullOrEmpty(value))
{
return string.Empty;
}
value = value.Replace("'", "%27")
.Replace("(", "%28")
.Replace(")", "%29")
.Replace("*", "%2A")
.Replace("!", "%21")
.Replace("%7e", "~")
.Replace("+", "%20")
.Replace(":", "%3A");
var sbuilder = new StringBuilder(value);
for (var i = 0; i < sbuilder.Length; i++)
{
if (sbuilder[i] != '%')
{
continue;
}
if (!char.IsLetter(sbuilder[i + 1]) && !char.IsLetter(sbuilder[i + 2]))
{
continue;
}
sbuilder[i + 1] = char.ToUpper(sbuilder[i + 1]);
sbuilder[i + 2] = char.ToUpper(sbuilder[i + 2]);
}
return sbuilder.ToString();
}
public string SignRequest(Dictionary<string, string> parametersUrl, Dictionary<string, string>
parametersSignture)
{
var secret = Encoding.UTF8.GetBytes(parametersSignture["Secret"]);
var signer = new HMACSHA256(secret);
var pc = new ParamComparer();
var sortedParameters = new SortedDictionary<string, string>(parametersUrl, pc);
var orderedParameters = ConstructCanonicalQueryString(sortedParameters);
var builder = new StringBuilder();
builder.Append(parametersSignture["RequestMethod"])
.Append(" \n")
.Append(parametersSignture["EndPoint"])
.Append("\n")
.Append("/\n")
.Append(orderedParameters);
var stringToSign = builder.ToString();
var toSign = Encoding.UTF8.GetBytes(stringToSign);
var sigBytes = signer.ComputeHash(toSign);
var signature = Convert.ToBase64String(sigBytes);
return signature.Replace("=", "%3D").Replace("/", "%2F").Replace("+", "%2B");
}
public class ParamComparer : IComparer<string>
{
public int Compare(string p1, string p2)
{
return string.CompareOrdinal(p1, p2);
}
}

Answer 1

The issue was that the Action wasn't included correctly into the Request