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Make GetKnownHttpScheme "safe" #21204

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merged 3 commits into from
Apr 28, 2020
Merged

Make GetKnownHttpScheme "safe" #21204

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31add2b
Make GetKnownHttpScheme "safe"
benaadams Apr 25, 2020
6fb46d5
Use Try method
benaadams Apr 25, 2020
cd36d89
Change back to extension method
benaadams Apr 25, 2020
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15 changes: 3 additions & 12 deletions src/Servers/Kestrel/Core/src/Internal/Infrastructure/HttpUtilities.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -430,20 +430,11 @@ internal static HttpVersion GetKnownVersionAndConfirmCR(this ReadOnlySpan<byte>
/// <param name="knownScheme">A reference to the known scheme, if the input matches any</param>
/// <returns>True when memory starts with known http or https schema</returns>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static unsafe bool GetKnownHttpScheme(this Span<byte> span, out HttpScheme knownScheme)
public static bool GetKnownHttpScheme(this Span<byte> span, out HttpScheme knownScheme)
{
fixed (byte* data = span)
if (span.Length >= sizeof(ulong))
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The JIT isn't always smart enough to match this manual check to the call to BinaryPrimitives below, so it could end up duplicating the bounds check. Suggest using BinaryPrimitives.TryReadUInt64LittleEndian instead, which guarantees that the bounds check will be emitted a maximum of once.

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Raised issue for it dotnet/runtime#35348; will try the the Try version as you suggest

{
return GetKnownHttpScheme(data, span.Length, out knownScheme);
}
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static unsafe bool GetKnownHttpScheme(byte* location, int length, out HttpScheme knownScheme)
{
if (length >= sizeof(ulong))
{
var scheme = *(ulong*)location;
var scheme = BinaryPrimitives.ReadUInt64LittleEndian(span);
if ((scheme & _mask7Chars) == _httpSchemeLong)
{
knownScheme = HttpScheme.Http;
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