NGINX 反向代理和访问控制允许来源问题

我正在配置一个NGINX Reverse Proxy.

在浏览器上我转到：
客户端网址： https://www.hollywood.com

那么上面的网页需要执行以下请求：
服务器网址： https://server.hollywood.com/api/auth/login

这是对应的配置：server.hollywood.com:

server {
    listen 443 ssl;
    server_name             server.hollywood.com;
    # add_header 'Access-Control-Allow-Origin' "https://www.hollywood.com" always;
    add_header 'Access-Control-Allow-Credentials' 'true' always;
    add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS' always;
    add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With' always;
    ssl_certificate         ../ssl/lets-encrypt/hollywood.com.crt;
    ssl_certificate_key     ../ssl/lets-encrypt/hollywood.com.key;
    location /
    {
        proxy_pass http://localhost:9201;
        include "../proxy_params.conf";
    }
}

实验一：

随着Access-Control-Allow-Origin当我访问时，行被注释掉：
客户端网址： https://www.hollywood.com

我在浏览器控制台上收到以下错误（在我的例子中为 Chrome）：

POST https://server.hollywood.com/api/auth/login/local 502 (Bad Gateway)
(index):1 Failed to load https://server.hollywood.com/api/auth/login/local: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://www.hollywood.com' is therefore not allowed access. The response had HTTP status code 502.

实验2：

如果我启用Access-Control-Allow-Origin上面一行，然后我进入浏览器终端：

Failed to load https://server.hollywood.com/api/auth/login/local: Response to preflight request doesn't pass access control check: The 'Access-Control-Allow-Origin' header contains multiple values '*, https://www.hollywood.com', but only one is allowed. Origin 'https://www.hollywood.com' is therefore not allowed access.

我不知道为什么在该标头不存在之前会出现多个？？？

实验3：

另一方面，如果我直接在浏览器上访问：
服务器网址： https://server.hollywood.com/api/auth/login与Access-Control-Allow-Origin行注释掉，我得到以下内容（在网络部分）：

Response Headers:

Access-Control-Allow-Credentials: true
Access-Control-Allow-Headers: Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With
Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
Access-Control-Allow-Origin: *
Connection: keep-alive
Content-Length: 139
Content-Security-Policy: default-src 'self'
Content-Type: text/html; charset=utf-8
Date: Sat, 09 Jun 2018 06:34:00 GMT
Server: nginx/1.13.12
X-Content-Type-Options: nosniff

在我得到：“请求的资源上不存在‘Access-Control-Allow-Origin’标头。”但现在我在上面看到该字段位于响应标头中。

实验4：

如果我再次启用Access-Control-Allow-Origin上面的行，然后我得到以下内容（在网络部分）：

Response Headers:

Access-Control-Allow-Credentials: true
Access-Control-Allow-Headers: Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With
Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
Access-Control-Allow-Origin: https://www.hollywood.com
Access-Control-Allow-Origin: *
Connection: keep-alive
Content-Length: 139
Content-Security-Policy: default-src 'self'
Content-Type: text/html; charset=utf-8
Date: Sat, 09 Jun 2018 06:34:58 GMT
Server: nginx/1.13.12
X-Content-Type-Options: nosniff

现在我得到两倍的字段：Access-Control-Allow-Origin.

您是否知道为什么我的前两个实验未能获得与以下相关的错误：Access-Control-Allow-Origin?

Thanks!

可能是您的 proxy_pass 后面的服务器正在设置Access-Control-Allow-Origin标题也是如此。

对于未来遇到类似问题的读者来说，这是值得的，我发现我的 Node.js 服务器正在传递一个Access-Control-Allow-Origin: '*'由于某种原因，我设置了 header，以及我在 node.js 中设置的实际 header 以限制 CORS。当注释掉我的node.js cors中间件时，Access-Control-Allow-Origin: '*'标题仍然保留。

为了解决这个问题，我使用了 nginxproxy_hide_header指令删除来自 node.js 的标头并按应有的方式手动添加它：

# proxying the
map $http_upgrade $connection_upgrade {
    default upgrade;
    '' close;
}

# local node.js server
upstream websocket {
    server 127.0.0.1:3000;
}

server {
    server_name ...;
    # ...;

    # add the header here
    add_header Access-Control-Allow-Origin https://www.hollywood.com;

    # Websockets config
    location /socket.io/ {
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;

        # do not pass the CORS header from the response of the proxied server to the
        # client
        proxy_hide_header 'Access-Control-Allow-Origin';

        proxy_pass http://websocket;
        proxy_http_version 1.1;
    }

    location / {
        # ...
        try_files $uri /index.html;
    }
}

谷歌搜索这个问题非常困难，因为大多数人都试图通过开放访问控制来修复 CORS！这是另一个有类似问题的问题：

https://serverfault.com/questions/751678/how-can-i-replace-access-control-allow-origin-header-in-proxy-response-with-ngin