@@ -0,0 +1,185 @@
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Globalization;
using System.Linq;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
namespace AwsV4SignatureCalculator
{
public class AwsV4SignatureCalculator
{
public const string Iso8601DateTimeFormat = "yyyyMMddTHHmmssZ";
public const string Iso8601DateFormat = "yyyyMMdd";
private readonly string _awsSecretKey;
private readonly string _service;
private readonly string _region;
public AwsV4SignatureCalculator(string awsSecretKey, string service, string region = null)
{
_awsSecretKey = awsSecretKey;
_service = service;
_region = region ?? "us-east-1";
}
/// <summary>
/// Calculates request signature string using Signature Version 4.
/// http://docs.aws.amazon.com/general/latest/gr/sigv4_signing.html
/// </summary>
/// <param name="request">Request</param>
/// <param name="signedHeaders">Canonical headers that are a part of a signing process</param>
/// <param name="requestDate">Date and time when request takes place</param>
/// <returns>Signature</returns>
public string CalculateSignature(HttpRequestMessage request, string[] signedHeaders, DateTime requestDate)
{
signedHeaders = signedHeaders.Select(x => x.Trim().ToLowerInvariant()).OrderBy(x => x).ToArray();
var canonicalRequest = GetCanonicalRequest(request, signedHeaders);
var stringToSign = GetStringToSign(requestDate, canonicalRequest);
return GetSignature(requestDate, stringToSign);
}
// http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
private static string GetCanonicalRequest(HttpRequestMessage request, string[] signedHeaders)
{
var canonicalRequest = new StringBuilder();
canonicalRequest.AppendFormat("{0}\n", request.Method.Method);
canonicalRequest.AppendFormat("{0}\n", request.RequestUri.AbsolutePath);
canonicalRequest.AppendFormat("{0}\n", GetCanonicalQueryParameters(request.RequestUri.ParseQueryString()));
canonicalRequest.AppendFormat("{0}\n", GetCanonicalHeaders(request, signedHeaders));
canonicalRequest.AppendFormat("{0}\n", String.Join(";", signedHeaders));
canonicalRequest.Append(GetPayloadHash(request));
return canonicalRequest.ToString();
}
private static string GetCanonicalQueryParameters(NameValueCollection queryParameters)
{
StringBuilder canonicalQueryParameters = new StringBuilder();
foreach (string key in queryParameters)
{
canonicalQueryParameters.AppendFormat("{0}={1}&", Utils.UrlEncode(key),
Utils.UrlEncode(queryParameters[key]));
}
// remove trailing '&'
if (canonicalQueryParameters.Length > 0)
canonicalQueryParameters.Remove(canonicalQueryParameters.Length - 1, 1);
return canonicalQueryParameters.ToString();
}
private static string GetCanonicalHeaders(HttpRequestMessage request, IEnumerable<string> signedHeaders)
{
var headers = request.Headers.ToDictionary(x => x.Key.Trim().ToLowerInvariant(),
x => String.Join(" ", x.Value).Trim());
if (request.Content != null)
{
var contentHeaders = request.Content.Headers.ToDictionary(x => x.Key.Trim().ToLowerInvariant(),
x => String.Join(" ", x.Value).Trim());
foreach (var contentHeader in contentHeaders)
{
headers.Add(contentHeader.Key, contentHeader.Value);
}
}
var sortedHeaders = new SortedDictionary<string, string>(headers);
StringBuilder canonicalHeaders = new StringBuilder();
foreach (var header in sortedHeaders.Where(header => signedHeaders.Contains(header.Key)))
{
canonicalHeaders.AppendFormat("{0}:{1}\n", header.Key, header.Value);
}
return canonicalHeaders.ToString();
}
private static string GetPayloadHash(HttpRequestMessage request)
{
var payload = request.Content != null ? request.Content.ReadAsStringAsync().Result : "";
return Utils.ToHex(Utils.Hash(payload));
}
// http://docs.aws.amazon.com/general/latest/gr/sigv4-create-string-to-sign.html
private string GetStringToSign(DateTime requestDate, string canonicalRequest)
{
var dateStamp = requestDate.ToString(Iso8601DateFormat, CultureInfo.InvariantCulture);
var scope = string.Format("{0}/{1}/{2}/{3}", dateStamp, _region, _service, "aws4_request");
var stringToSign = new StringBuilder();
stringToSign.AppendFormat("AWS4-HMAC-SHA256\n{0}\n{1}\n",
requestDate.ToString(Iso8601DateTimeFormat, CultureInfo.InvariantCulture),
scope);
stringToSign.Append(Utils.ToHex(Utils.Hash(canonicalRequest)));
return stringToSign.ToString();
}
// http://docs.aws.amazon.com/general/latest/gr/sigv4-calculate-signature.html
private string GetSignature(DateTime requestDate, string stringToSign)
{
var kSigning = GetSigningKey(requestDate);
return Utils.ToHex(Utils.GetKeyedHash(kSigning, stringToSign));
}
private byte[] GetSigningKey(DateTime requestDate)
{
var dateStamp = requestDate.ToString(Iso8601DateFormat, CultureInfo.InvariantCulture);
var kDate = Utils.GetKeyedHash("AWS4" + _awsSecretKey, dateStamp);
var kRegion = Utils.GetKeyedHash(kDate, _region);
var kService = Utils.GetKeyedHash(kRegion, _service);
return Utils.GetKeyedHash(kService, "aws4_request");
}
private static class Utils
{
private const string ValidUrlCharacters =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.~";
public static string UrlEncode(string data)
{
StringBuilder encoded = new StringBuilder();
foreach (char symbol in Encoding.UTF8.GetBytes(data))
{
if (ValidUrlCharacters.IndexOf(symbol) != -1)
{
encoded.Append(symbol);
}
else
{
encoded.Append("%").Append(string.Format(CultureInfo.InvariantCulture, "{0:X2}", (int) symbol));
}
}
return encoded.ToString();
}
public static byte[] Hash(string value)
{
return new SHA256CryptoServiceProvider().ComputeHash(Encoding.UTF8.GetBytes(value));
}
public static byte[] GetKeyedHash(string key, string value)
{
return GetKeyedHash(Encoding.UTF8.GetBytes(key), value);
}
public static byte[] GetKeyedHash(byte[] key, string value)
{
KeyedHashAlgorithm mac = new HMACSHA256(key);
mac.Initialize();
return mac.ComputeHash(Encoding.UTF8.GetBytes(value));
}
public static string ToHex(byte[] data)
{
StringBuilder sb = new StringBuilder();
for (int i = 0; i < data.Length; i++)
{
sb.Append(data[i].ToString("x2", CultureInfo.InvariantCulture));
}
return sb.ToString();
}
}
}
}
yvanin revised this gist