Remove quotes from MultipartReader boundary

[aclark09]

Remove quotes from MultipartReader boundary

Description

When a request is submitted by HttpClient via MultipartFormDataContent, the boundary value in multipart/formdata request header is enclosed with double quotes. In this case, when using MediaTypeHeaderValue.TryParse to parse the header, the MediaTypeHeaderValue will include those double quotes as boundary when parsing the header. This leads to an exception being thrown.

The solution for now is to remove quotes from the boundary passed in to the MultipartReader constructor. I also added a unit test that checks to see if a boundary with double quotes works.

Fixes #41237

[Tratcher]

Organization: Move this down to where _boundary is being initialized.

[aclark09]

So just put it right above that line? Yeah I can do that.

[davidfowl]

Does this allocate when there's nothing to do?

[aclark09]

Are you talking about that fact that RemoveQuotes is called before all of the null checks? I just pushed up a change so that it's now being called right before the boundary variable is actually used, so it shouldn't be allocated unless it's used now.

[Tratcher]

It doesn't allocate.

aspnetcore/src/Http/Headers/src/HeaderUtilities.cs

Lines 570 to 574 in bcdb13d

	if (IsQuoted(input))
	{
	input = input.Subsegment(1, input.Length - 2);
	}
	return input;

[rpnetcoder]

Have you checked if there is no string allocation when calling ToString() when double quotes are not present in an input boundary? What about checking if there are double quotes first and only after that to remove them and call ToString()?

[Tratcher]

I checked, there's no allocation since this ends up returning the whole original string.
https://github.com/dotnet/runtime/blob/2ea67f1f42e8170676c9e9591a974e39513390db/src/libraries/Microsoft.Extensions.Primitives/src/StringSegment.cs#L661
https://github.com/dotnet/runtime/blob/2ea67f1f42e8170676c9e9591a974e39513390db/src/libraries/Microsoft.Extensions.Primitives/src/StringSegment.cs#L81
https://github.com/dotnet/runtime/blob/215b39abf947da7a40b0cb137eab4bceb24ad3e3/src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs#L1831-L1834

[rpnetcoder]

Thanks for the clarification

[Tratcher]

Thanks @aclark09