Nginx解决跨域问题(CORS)

Posted 2020-11-03 iceman!

前言

CORS(Cross-Origin Resource Sharing) 跨域资源共享,是一种允许当前域（domain）的资源（比如html/js/web service）被其他域（domain）的脚本请求访问的机制，通常由于同域安全策略（the same-origin security policy）浏览器会禁止这种跨域请求。 
如：a.com 请求b.com的资源时，就涉及到了跨域。目前常见的跨域解决方案一般分为如下几类：

• jsonp返回值解决get请求
• iframe解决跨域访问
• Nginx 解决CORS

nginx配置

1 简单配置

server {
        listen       80;
        server_name  b.com;
        location /{
            add_header ‘Access-Control-Allow-Origin‘ ‘http://a.com‘;
            add_header ‘Access-Control-Allow-Credentials‘ ‘true‘;
            add_header ‘Access-Control-Allow-Methods‘ ‘GET‘;
        }
}

• add_header：授权从a.com的请求

• 第二条add_header：当该标志为真时，响应于该请求是否可以被暴露

• 第三条add_header：指定请求的方法，可以是GET，POST，PUT，DELETE，HEAD 
  同样支持通配符，如允许来自任何域的请求:

server {
        listen 80;
        server_name b.com;
        location /{
            Access-Control-Allow-Origin: *
        }
    }

2 高级配置

location / {
     if ($request_method = ‘OPTIONS‘) {
        add_header ‘Access-Control-Allow-Origin‘ ‘*‘;
        add_header ‘Access-Control-Allow-Methods‘ ‘GET, POST, OPTIONS‘;
        #
        # Custom headers and headers various browsers *should* be OK with but aren‘t
        #
        add_header ‘Access-Control-Allow-Headers‘ ‘DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type‘;
        #
        # Tell client that this pre-flight info is valid for 20 days
        #
        add_header ‘Access-Control-Max-Age‘ 1728000;
        add_header ‘Content-Type‘ ‘text/plain charset=UTF-8‘;
        add_header ‘Content-Length‘ 0;
        return 204;
     }
     if ($request_method = ‘POST‘) {
        add_header ‘Access-Control-Allow-Origin‘ ‘*‘;
        add_header ‘Access-Control-Allow-Methods‘ ‘GET, POST, OPTIONS‘;
        add_header ‘Access-Control-Allow-Headers‘ ‘DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type‘;
     }
     if ($request_method = ‘GET‘) {
        add_header ‘Access-Control-Allow-Origin‘ ‘*‘;
        add_header ‘Access-Control-Allow-Methods‘ ‘GET, POST, OPTIONS‘;
        add_header ‘Access-Control-Allow-Headers‘ ‘DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type‘;
     }
}

因为POST跨域请求会先发一次OPTIONS的嗅探请求，所有有的场景涉及到设置OPTIONS。