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带有代理中间件的Echo-CORS在带有Access-Allow-Origins响应头的情况下导致问题

go-echo cors proxy go

RavenHursT · 技术社区 · 5 年前

其中一个路由需要代理对后端服务的请求和响应。

但我也需要CORS来处理这项服务。

所以我用 middleware.CORSWithConfig 沿w/a middleware.ProxyWithConfig 在我的请求/响应堆栈中。

我看到一些奇怪的东西 Access-Control-Allow-Origins 标头,其中该标头在从代理服务到我的Echo服务器的响应中的值 * ,但一旦通过代理,它将更改为 *, * 当它回到客户端时。在此之后,我开始看到以下与CORS违规相关的浏览器错误:

VM1627:362 Access to XMLHttpRequest at 'http://localhost:6273/' from origin 'http://localhost:8002' has been blocked by CORS policy: The 'Access-Control-Allow-Origin' header contains multiple values '*, *', but only one is allowed.

下面是一些示例代码:

package main

func singleTargetBalancer(url *url.URL) middleware.ProxyBalancer {
    targetURL := []*middleware.ProxyTarget{
        {
            URL: url,
        },
    }
    return middleware.NewRoundRobinBalancer(targetURL)
}

func Noop(ctx echo.Context) (err error) {
    ctx.String(
        http.StatusNotImplemented,
        "No op handler should never be reached!",
    )

    return err
}

func main() {
        e := echo.New()
    e.HideBanner = true
    e.Use(
        middleware.CORSWithConfig(middlewares.CustomCorsConfig),
        middlewares.ThriftMetrics(),
    )

        // Have to use a Noop handler since we're not trying to set up a full-on proxy for the backend service.  We only want this one route to be proxied.
        e.POST(
        "/",
        handlers.Noop,
        middleware.ProxyWithConfig(middleware.ProxyConfig{
             Balancer: singleTargetBalancer("[backend service URL]"),
            })
    )
}

0 回复 | 直到 5 年前

RavenHursT 5 年前

我最终解决了这个问题,在Echo的代理中间件可以将头发送回客户端之前,我编写了一个定制的Echo中间件来连接到响应中。

func setResponseACAOHeaderFromRequest (req http.Request, resp echo.Response) {
    resp.Header().Set(echo.HeaderAccessControlAllowOrigin, 
    req.Header.Get(echo.HeaderOrigin))
}

func ACAOHeaderOverwriteMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
    return func(ctx echo.Context) error {
        ctx.Response().Before(func() {
            setResponseACAOHeaderFromRequest(*ctx.Request(), *ctx.Response())
        })
        return next(ctx)
    }
}

然后把这个中间件放进去 e.Use() 正当在代理中间件之前:

e.POST(
        "/",
        handlers.Noop,
        ACAOHeaderOverwriteMiddleware,
        middleware.ProxyWithConfig(middleware.ProxyConfig{
             Balancer: singleTargetBalancer("[backend service URL]"),
        })
)

Echo的文档 Request::Before() https://echo.labstack.com/guide/response#before-response