Configuring CORS

Prerequisites

Static website hosting has been configured. For details, see Configuring Static Website Hosting.

Creating a CORS Rule

1. In the navigation pane of OBS Console, choose Object Storage.
2. In the bucket list, click the bucket you want to operate to go to the Objects page.
3. In the navigation pane, choose Overview.
4. In the Basic Configurations area, click CORS Rules. The CORS Rules page is displayed.
   Figure 1 Overview > Basic Configurations > CORS Rules
   

   Alternatively, you can choose Permissions > CORS Rules in the navigation pane.

   Figure 2 Permissions > CORS Rules
   

5. Click Create. The Create CORS Rule dialog box is displayed. See Figure 3 for details.
   

   A bucket can have a maximum of 100 CORS rules configured.

   Figure 3 Creating a CORS rule
   

6. In the CORS Rule dialog box, configure Allowed Origin, Allowed Method, Allowed Header, Exposed Header, and Cache Duration (s).
   

   If CDN acceleration is enabled for the bucket, HTTP headers must be configured on CDN. For details, see HTTP Header Settings.

   Table 1 Parameters in CORS rules

   Parameter	Description
   Allowed Origin	Mandatory Specifies the origins from which requests can access the bucket. Multiple matching rules are allowed. One rule occupies one line, and allows one wildcard character (*) at most. An example is given as follows: http://rds.example.com https://*.vbs.example.com
   Allowed Method	Mandatory Specifies the allowed request methods for buckets and objects. The methods include Get, Post, Put, Delete, and Head.
   Allowed Header	Optional Specifies the allowed headers in cross-origin requests. Only CORS requests matching the allowed headers are valid. You can enter multiple allowed headers (one per line) and each line can contain one wildcard character (*) at most. Spaces and special characters including &:< are not allowed.
   Exposed Header	Optional Specifies the exposed headers in CORS responses, providing additional information for clients. By default, a browser can access only headers Content-Length and Content-Type. If the browser wants to access other headers, you need to configure them in this parameter. For the configuration of other headers, see Configuring CORS for a Bucket. You can enter multiple exposed headers (one per line). Spaces and special characters including *&:< are not allowed.
   Cache Duration (s)	Mandatory Specifies the duration that your browser can cache CORS responses, expressed in seconds. The default value is 100.

7. Click OK.

   Message "The CORS rule created successfully." is displayed. The CORS configuration will take effect within two minutes.

   Then, only the addresses specified in Allowed Origin can access the OBS bucket over the methods specified in Allowed Method. Suppose you need to configure a CORS rule for bucket testbucket and you set Allowed Origin to https://www.example.com, Allowed Method to GET, Allowed Header to *, Exposed Header to ETag, and Cache Duration (s) to 100. Then, only GET requests from https://www.example.com are allowed to access bucket testbucket. In addition, there are no limits put on headers in the requests, the ETag value can be returned in the response, and the client where the requests are from can cache the CORS response for 100 seconds.

Replicating CORS Rules

1. In the navigation pane of OBS Console, choose Object Storage.
2. In the bucket list, click the bucket you want to operate to go to the Objects page.
3. In the navigation pane, choose Overview.
4. In the Basic Configurations area, click CORS Rules. The CORS Rules page is displayed.

   Alternatively, you can choose Permissions > CORS Rules in the navigation pane.

5. Click Replicate.
6. Select a replication source, which is the bucket whose CORS rules you want to replicate.
   

   • The CORS rules replicated from a source bucket will not overwrite existing rules in the destination bucket, and any that conflict with the existing ones will not be replicated.
   • The version of both source and destination buckets must be 3.0.
   • You can remove the rules that you do not want to replicate.
   • There can be 100 CORS rules at most in a bucket. If the number of rules you will replicate plus the number of existing rules in the destination bucket exceeds 100, the replication will fail. Before replicating the rules, delete some if necessary.
   Figure 4 Replicating CORS rules
   

7. Click OK to replicate the CORS rules to the destination bucket.