force query strings to be case sensitive

In order to maximise cache-hits on a reverse proxy e.g. CloudFront, we want to normalize all urls. However, aspnet core inexplicably treats query string keys as case-insensitive - ?d=b is the same as ?D=b.

Author: thefringeninja

src/SqlStreamStore.HAL/CaseSensitiveQueryCollection.cs

@@ -0,0 +1,64 @@
+namespace SqlStreamStore.HAL
+{
+    using System;
+    using System.Collections;
+    using System.Collections.Generic;
+    using Microsoft.AspNetCore.Http;
+    using Microsoft.AspNetCore.Http.Features;
+    using Microsoft.Extensions.Primitives;
+
+    internal class CaseSensitiveQueryFeature : IQueryFeature
+    {
+        private readonly IFeatureCollection _features;
+
+        public CaseSensitiveQueryFeature(IFeatureCollection features)
+        {
+            if(features == null)
+                throw new ArgumentNullException(nameof(features));
+            _features = features;
+        }
+
+        public IQueryCollection Query
+        {
+            get;
+            set;
+        }
+    }
+
+    internal class CaseSensitiveQueryCollection : IQueryCollection
+    {
+        private readonly QueryString _queryString;
+
+        private Dictionary<string, StringValues> _state;
+
+        public CaseSensitiveQueryCollection(QueryString queryString)
+        {
+            _queryString = queryString;
+        }
+
+        private Dictionary<string, StringValues> GetState()
+            => _state
+               ?? (_state = QueryStringHelper.ParseQueryString(_queryString));
+
+        public IEnumerator<KeyValuePair<string, StringValues>> GetEnumerator()
+            => GetState().GetEnumerator();
+
+        IEnumerator IEnumerable.GetEnumerator()
+            => GetEnumerator();
+
+        public bool ContainsKey(string key)
+            => GetState().ContainsKey(key);
+
+        public bool TryGetValue(string key, out StringValues value)
+            => GetState().TryGetValue(key, out value);
+
+        public int Count
+            => GetState().Count;
+
+        public ICollection<string> Keys
+            => GetState().Keys;
+
+        public StringValues this[string key]
+            => GetState()[key];
+    }
+}

src/SqlStreamStore.HAL/QueryCollectionExtensions.cs

@@ -0,0 +1,23 @@
+namespace SqlStreamStore.HAL
+{
+    using System;
+    using Microsoft.AspNetCore.Http;
+    using Microsoft.Extensions.Primitives;
+
+    internal static class QueryCollectionExtensions
+    {
+        public static bool TryGetValueCaseInsensitive(this IQueryCollection query, char key, out StringValues values)
+        {
+            if(query == null)
+            {
+                throw new ArgumentNullException(nameof(query));
+            }
+
+            return char.IsUpper(key)
+                ? query.TryGetValue(key.ToString(), out values)
+                  || query.TryGetValue(char.ToLower(key).ToString(), out values)
+                : query.TryGetValue(key.ToString(), out values)
+                  || query.TryGetValue(char.ToUpper(key).ToString(), out values);
+        }
+    }
+}

src/SqlStreamStore.HAL/QueryStringHelper.cs

@@ -0,0 +1,51 @@
+namespace SqlStreamStore.HAL
+{
+    using System;
+    using System.Collections.Generic;
+    using Microsoft.AspNetCore.Http;
+    using Microsoft.Extensions.Primitives;
+
+    internal static class QueryStringHelper
+    {
+        private static readonly char[] s_delimiter = { '=' };
+        private static readonly QueryString s_almostEmpty = new QueryString("?");
+
+        public static Dictionary<string, StringValues> ParseQueryString(QueryString queryString)
+        {
+            var state = new Dictionary<string, StringValues>();
+
+            if(queryString == QueryString.Empty || queryString == s_almostEmpty)
+            {
+                return state;
+            }
+
+            var qs = queryString.Value;
+
+            if(qs[0] == '?')
+            {
+                qs = qs.Substring(1);
+            }
+
+            foreach(var pair in qs.Split('&'))
+            {
+                var parts = pair.Split(s_delimiter, 2);
+                var key = Uri.UnescapeDataString(parts[0].Replace('+', ' '));
+
+                state.TryGetValue(key, out var values);
+
+                if(parts.Length == 1)
+                {
+                    state[key] = values;
+                }
+                else
+                {
+                    var value = Uri.UnescapeDataString(parts[1].Replace('+', ' '));
+
+                    state[key] = StringValues.Concat(value, values);
+                }
+            }
+
+            return state;
+        }
+    }
+}

src/SqlStreamStore.HAL/Resources/ReadAllStreamOperation.cs

@@ -12,21 +12,32 @@ internal class ReadAllStreamOperation : IStreamStoreOperation<ReadAllPage>
 
         public ReadAllStreamOperation(HttpRequest request)
         {
-            EmbedPayload = request.Query.TryGetValue("e", out _);
+            EmbedPayload = request.Query.TryGetValueCaseInsensitive('e', out _);
 
-            ReadDirection = request.Query["d"] == "f"
+            ReadDirection = request.Query.TryGetValueCaseInsensitive('d', out var readDirection)
+                            && readDirection == "f" || readDirection == "F"
                 ? Constants.ReadDirection.Forwards
                 : Constants.ReadDirection.Backwards;
 
-            if(!long.TryParse(request.Query["p"], out _fromPositionInclusive))
-            {
-                _fromPositionInclusive = ReadDirection > 0 ? Position.Start : Position.End;
-            }
+            _fromPositionInclusive = request.Query.TryGetValueCaseInsensitive('p', out var position)
+                ? (long.TryParse(position, out _fromPositionInclusive)
+                    ? (_fromPositionInclusive < Position.End
+                        ? Position.End
+                        : _fromPositionInclusive)
+                    : (ReadDirection == Constants.ReadDirection.Forwards
+                        ? Position.Start
+                        : Position.End))
+                : (ReadDirection == Constants.ReadDirection.Forwards
+                    ? Position.Start
+                    : Position.End);
 
-            if(!int.TryParse(request.Query["m"], out _maxCount))
-            {
-                _maxCount = Constants.MaxCount;
-            }
+            _maxCount = request.Query.TryGetValueCaseInsensitive('m', out var maxCount)
+                ? (int.TryParse(maxCount, out _maxCount)
+                    ? (_maxCount <= 0
+                        ? Constants.MaxCount
+                        : _maxCount)
+                    : Constants.MaxCount)
+                : Constants.MaxCount;
 
             Self = ReadDirection == Constants.ReadDirection.Forwards
                 ? LinkFormatter.FormatForwardLink(

src/SqlStreamStore.HAL/Resources/ReadStreamOperation.cs

@@ -14,23 +14,36 @@ public ReadStreamOperation(HttpRequest request)
         {
             StreamId = request.Path.Value.Remove(0, 1);
 
-            EmbedPayload = request.Query.TryGetValue("e", out _);
+            EmbedPayload = request.Query.TryGetValueCaseInsensitive('e', out _);
 
-            ReadDirection = request.Query["d"] == "f"
+            ReadDirection = request.Query.TryGetValueCaseInsensitive('d', out var readDirection)
+                            && readDirection == "f" || readDirection == "F"
                 ? Constants.ReadDirection.Forwards
                 : Constants.ReadDirection.Backwards;
 
-            if(!int.TryParse(request.Query["p"], out _fromVersionInclusive))
-            {
-                _fromVersionInclusive = ReadDirection == Constants.ReadDirection.Forwards
+            _fromVersionInclusive = request.Query.TryGetValueCaseInsensitive('p', out var position)
+                ? (int.TryParse(position, out _fromVersionInclusive)
+                    ? (ReadDirection == Constants.ReadDirection.Forwards
+                        ? (_fromVersionInclusive < StreamVersion.Start
+                            ? StreamVersion.Start
+                            : _fromVersionInclusive)
+                        : (_fromVersionInclusive < StreamVersion.End
+                            ? StreamVersion.End
+                            : _fromVersionInclusive))
+                    : (ReadDirection == Constants.ReadDirection.Forwards
+                        ? StreamVersion.Start
+                        : StreamVersion.End))
+                : (ReadDirection == Constants.ReadDirection.Forwards
                     ? StreamVersion.Start
-                    : StreamVersion.End;
-            }
+                    : StreamVersion.End);
 
-            if(!int.TryParse(request.Query["m"], out _maxCount))
-            {
-                _maxCount = Constants.MaxCount;
-            }
+            _maxCount = request.Query.TryGetValueCaseInsensitive('m', out var maxCount)
+                ? (int.TryParse(maxCount, out _maxCount)
+                    ? (_maxCount <= 0 
+                        ? Constants.MaxCount 
+                        : _maxCount)
+                    : Constants.MaxCount)
+                : Constants.MaxCount;
 
             Self = ReadDirection == Constants.ReadDirection.Forwards
                 ? LinkFormatter.FormatForwardLink(StreamId, MaxCount, FromVersionInclusive, EmbedPayload)

src/SqlStreamStore.HAL/SqlStreamStoreHalMiddleware.cs

@@ -14,6 +14,21 @@
 
     public static class SqlStreamStoreHalMiddleware
     {
+        private static MidFunc CaseSensitiveQueryStrings => (context, next) =>
+        {
+            if(context.Request.QueryString != QueryString.Empty)
+            {
+                var queryString = context.Request.QueryString;
+                context.Request.Query = new CaseSensitiveQueryCollection(queryString);
+                // Setting context.Request.Query mutates context.Request.QueryString.
+                // This has the unfortunate side effect of turning ?a=1&b into ?a=1&b=.
+                // so, replace with original context.Request.QueryString and call it a day.
+                context.Request.QueryString = queryString;
+            }
+
+            return next();
+        };
+
         private static MidFunc MethodsNotAllowed(params string[] methods) => (context, next) =>
         {
             if(!methods.Contains(context.Request.Method))
@@ -68,6 +83,7 @@ public static IApplicationBuilder UseSqlStreamStoreHal(
 
             return builder
                 .Use(ExceptionHandlingMiddleware.HandleExceptions)
+                .Use(CaseSensitiveQueryStrings)
                 .Use(AcceptHalJson)
                 .Use(Index)
                 .Map("/stream", UseAllStream(streamStore))