Granting an IAM User the Read Permissions on Specific Objects

Scenario

This topic describes how to grant an IAM user the read permissions on an object or a set of objects in an OBS bucket.

Recommended Configuration

To grant resource-level permissions to an IAM user, use a bucket policy.

Precautions

In this case, the preset template Object Read-Only allows specified IAM users to perform the following actions on specified objects in a bucket:

• GetObject (to obtain object content and metadata)
• GetObjectVersion (to obtain the content and metadata of a specified object version)
• GetObjectVersionAcl (to obtain the ACL of a specified object version)
• GetObjectAcl (to obtain the object ACL)
• RestoreObject (to restore objects from Archive storage)

After configuration, the IAM user can download specific objects using APIs or SDKs. However, if they download an object from OBS Console or OBS Browser+, a message will be displayed, indicating that they do not have required permissions.

This is because when they log in to OBS Console or OBS Browser+, the ListAllMyBuckets API is called to load the bucket list, the ListBucket API is called to load the object list, and some other APIs will also be called on other pages. In such case, the message is displayed.

If you want an IAM user to perform read operations on OBS Console or OBS Browser+, you need to configure custom IAM policies by referring to Follow-up Procedure.

Procedure

1. In the navigation pane of OBS Console, choose Buckets.
2. In the bucket list, click the bucket name you want to go to the Objects page.
3. In the navigation pane, choose Permissions > Bucket Policies.
4. On the Bucket Policies page, click Create.
5. Configure a bucket policy.
   Figure 1 Configuring a bucket policy
   

   Table 1 Parameters for configuring a bucket policy

   Parameter	Description
   Policy view	Select Visual Editor or JSON based on your own habits. Visual Editor is used here.
   Policy Name	Enter a policy name.
   Effect	Select Allow.
   Principal	Select Current account. IAM users: Select an IAM user that you want to grant permissions to.
   Resources	Select Specified objects. Enter an object name prefix for the resource path. NOTE: You can click Add to specify multiple resource paths. You can specify a specific object, an object set, or a directory. * indicates all objects in the bucket. To specify a specific object, enter the object name. To specify a set of objects, enter Object name prefix*, *Object name suffix, or *.
   Actions	Choose Use a template. Select Object Read-Only.

6. Confirm and click Create.

Follow-up Procedure

To perform read operations on OBS Console or OBS Browser+, you must add the obs:bucket:ListAllMyBuckets (for listing buckets) and obs:bucket:ListBucket (for listing objects in a bucket) permissions to the custom IAM policy.

obs:bucket:ListAllMyBuckets applies to all resources, while obs:bucket:ListBucket applies only to the authorized bucket. Therefore, you need to add these two permissions to the policy.

1. Log in to Huawei Cloud and click Console in the upper right corner.
2. On the console, hover over the username in the upper right corner, and choose Identity and Access Management from the drop-down list.
3. In the navigation pane, choose Permissions > Policies/Roles > Create Custom Policy.
4. Configure a custom policy.
   Figure 2 Configuring a custom policy
   

   Table 2 Parameters for configuring a custom policy

   Parameter	Description
   Policy Name	Enter a policy name.
   Policy View	Select one based on your own habits. Visual editor is used here.
   Policy Content	[Permission 1] Select Allow. Select Object Storage Service (OBS). Select obs:bucket:ListAllMyBuckets from the actions. Select All for resources. [Permission 2] Select Allow. Select Object Storage Service (OBS). Select obs:bucket:ListBucket from the actions. Select Specific for Resources and select Specify resource path for Bucket. Click Add Resource Path. Enter the bucket name in the Path text box for applying the policy only to this bucket.
   Scope	Use the default value Global services.

5. Click OK.
6. Create a user group and assign permissions.

   Apply the created custom policy to the user group by following the instructions in the IAM document.

7. Add the IAM user you want to authorize to the created user group.
   

   Due to data caching, it takes about 10 to 15 minutes for a custom policy to take effect.