AwsSignatureHandler now overrides the synchronous Send() method in .N…

…ET 5. See FantasticFiasco#478.

src/AwsSignatureHandler.cs

@@ -62,5 +62,38 @@ await Signer.SignAsync(
 
             return await base.SendAsync(request, cancellationToken);
         }
+
+#if NET5_0_OR_GREATER
+
+        /// <inheritdoc />
+        protected override HttpResponseMessage Send(
+            HttpRequestMessage request,
+            CancellationToken cancellationToken)
+        {
+            // Given the idempotent nature of message handlers, lets remove request headers that
+            // might have been added by an prior attempt to send the request
+            request.Headers.Remove(HeaderKeys.AuthorizationHeader);
+            request.Headers.Remove(HeaderKeys.XAmzContentSha256Header);
+            request.Headers.Remove(HeaderKeys.XAmzDateHeader);
+            request.Headers.Remove(HeaderKeys.XAmzSecurityTokenHeader);
+
+            var immutableCredentials = settings.Credentials.GetCredentials();
+
+            var signingTask = Signer.SignAsync(
+                request,
+                null,
+                EmptyRequestHeaders,
+                DateTime.UtcNow,
+                settings.RegionName,
+                settings.ServiceName,
+                immutableCredentials,
+                async: false);
+
+            System.Diagnostics.Debug.Assert(signingTask.IsCompletedSuccessfully, "The operation should have completed synchronously.");
+
+            return base.Send(request, cancellationToken);
+        }
+
+#endif
     }
 }

src/AwsSignatureVersion4.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <Description>The buttoned-up and boring, but deeply analyzed, implementation of Signature Version 4 (SigV4) in .NET.</Description>
-    <TargetFrameworks>net45;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>net45;netstandard2.0;net5.0</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <LangVersion>latest</LangVersion>
     <Nullable>enable</Nullable>

src/Private/CanonicalRequest.cs

@@ -54,7 +54,7 @@ public static (string, string) Build(
             // URI-encoded twice (
             // <see href="https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html">
             // except for Amazon S3 which only gets URI-encoded once</see>).
-            var canonicalResourcePath = GetCanonicalResourcePath(serviceName, request.RequestUri);
+            var canonicalResourcePath = GetCanonicalResourcePath(serviceName, request.RequestUri!);
 
             builder.Append($"{canonicalResourcePath}\n");
 
@@ -81,7 +81,7 @@ public static (string, string) Build(
             //    string for parameters that have no value.
             // e. Append the ampersand character (&) after each parameter value, except for the
             //    last value in the list.
-            var parameters = SortQueryParameters(request.RequestUri.Query)
+            var parameters = SortQueryParameters(request.RequestUri!.Query)
                 .SelectMany(
                     parameter => parameter.Value.Select(
                         parameterValue => $"{AWSSDKUtils.UrlEncode(parameter.Key, false)}={AWSSDKUtils.UrlEncode(parameterValue, false)}"));
@@ -166,7 +166,12 @@ public static SortedList<string, List<string>> SortQueryParameters(string query)
                     sortedQueryParameters.Add(parameterName, parameterValues);
                 }
 
-                parameterValues.AddRange(queryParameters.GetValues(parameterName));
+                parameterValues.AddRange(queryParameters.GetValues(parameterName) ??
+#if NET45
+                    new string[0]);
+#else
+                    Array.Empty<string>());
+#endif
             }
 
             // Sort the query parameter values

src/Private/ContentHash.cs

@@ -1,4 +1,5 @@
-using System.Net.Http;
+using System.IO;
+using System.Net.Http;
 using System.Threading.Tasks;
 using Amazon.Runtime.Internal.Auth;
 using Amazon.Util;
@@ -11,7 +12,7 @@ namespace AwsSignatureVersion4.Private
     /// </summary>
     public static class ContentHash
     {
-        public static async Task<string> CalculateAsync(HttpContent content)
+        public static async Task<string> CalculateAsync(HttpContent? content)
         {
             // Use a hash (digest) function like SHA256 to create a hashed value from the payload
             // in the body of the HTTP or HTTPS request.
@@ -28,5 +29,28 @@ public static async Task<string> CalculateAsync(HttpContent content)
             var hash = AWS4Signer.ComputeHash(data);
             return AWSSDKUtils.ToHex(hash, true);
         }
+
+#if NET5_0_OR_GREATER
+
+        public static string Calculate(HttpContent? content)
+        {
+            // Use a hash (digest) function like SHA256 to create a hashed value from the payload
+            // in the body of the HTTP or HTTPS request.
+            //
+            // If the payload is empty, use an empty string as the input to the hash function.
+            if (content == null)
+            {
+                // Per performance reasons, use the pre-computed hash of an empty string from the
+                // AWS SDK
+                return AWS4Signer.EmptyBodySha256;
+            }
+
+            // AWS4Signer.ComputeHash() simply calls CryptoUtilFactory.CryptoInstance.ComputeSHA256Hash(), but omits a Stream-based overload
+            var stream = content.ReadAsStream();
+            var hash = CryptoUtilFactory.CryptoInstance.ComputeSHA256Hash(stream);
+            return AWSSDKUtils.ToHex(hash, true);
+        }
+
+#endif
     }
 }

src/Private/Signer.cs

@@ -16,7 +16,11 @@ public static async Task<Result> SignAsync(
             DateTime now,
             string regionName,
             string serviceName,
-            ImmutableCredentials credentials)
+            ImmutableCredentials credentials
+#if NET5_0_OR_GREATER
+            , bool async = true
+#endif
+            )
         {
             if (request == null) throw new ArgumentNullException(nameof(request));
             if (request.Headers.Contains(HeaderKeys.XAmzDateHeader)) throw new ArgumentException(ErrorMessages.XAmzDateHeaderExists, nameof(request));
@@ -31,14 +35,20 @@ public static async Task<Result> SignAsync(
 
             UpdateRequestUri(request, baseAddress);
 
+#if NET5_0_OR_GREATER
+            var contentHash = async
+                    ? await ContentHash.CalculateAsync(request.Content)
+                    : ContentHash.Calculate(request.Content);
+#else
             var contentHash = await ContentHash.CalculateAsync(request.Content);
+#endif
 
             // Add required headers
             request.AddHeader(HeaderKeys.XAmzDateHeader, now.ToIso8601BasicDateTime());
 
             // Add conditional headers
             request.AddHeaderIf(credentials.UseToken, HeaderKeys.XAmzSecurityTokenHeader, credentials.Token);
-            request.AddHeaderIf(!request.Headers.Contains(HeaderKeys.HostHeader), HeaderKeys.HostHeader, request.RequestUri.Host);
+            request.AddHeaderIf(!request.Headers.Contains(HeaderKeys.HostHeader), HeaderKeys.HostHeader, request.RequestUri!.Host);
             request.AddHeaderIf(serviceName == ServiceName.S3, HeaderKeys.XAmzContentSha256Header, contentHash);
 
             // Build the canonical request