请求标头字段访问控制 - 允许标头本身在预检响应中不允许 [英] Request header field Access-Control-Allow-Headers is not allowed by itself in preflight response

问题描述

我已经碰到CORS问题多次，通常可以解决它，但我想真正理解从一个MEAN堆栈模式看到这一点。

I have come across CORS issues multiple times and can usually fix it but I want to really understand by seeing this from a MEAN stack paradigm.

在我的简单服务器中添加中间件来捕获这些东西之前，但是看起来像是有一些预钩子，这是错误的我的请求。

Before I simply added middleware in my express server to catch these things, but it looks like there is some kind of pre-hook that is erring out my requests.

Request header field Access-Control-Allow-Headers is not allowed by
    Access-Control-Allow-Headers in preflight response

我假设我可以这样做：

I assumed that I could do this:

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Headers","*")
})

修理它。我也当然尝试了

or the equivalent but this doesn't seem to fix it. I also of course tried

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Headers","Access-Control-Allow-Headers")
})

仍然没有运气。

推荐答案

你会得到一个CORS预检。这是一个使用HTTP OPTIONS 动词的请求，并包含多个标头，其中之一是 Access-Control-Request-Headers 列出客户希望包含在请求中的标头。

When you start playing around with custom request headers you will get a CORS preflight. This is a request that uses the HTTP OPTIONS verb and includes several headers, one of which being Access-Control-Request-Headers listing the headers the client wants to include in the request.

您需要使用适当的CORS标头来回复CORS预检，以使其工作。其中之一确实是 Access-Control-Allow-Headers 。该标头需要包含 Access-Control-Request-Headers 标头包含的（或更多）相同的值。

You need to reply to that CORS preflight with the appropriate CORS headers to make this work. One of which is indeed Access-Control-Allow-Headers. That header needs to contain the same values the Access-Control-Request-Headers header contained (or more).

https://fetch.spec.whatwg.org/#http-cors-protocol 说明此设置更详细。

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