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Updated on 2026-03-06 GMT+08:00
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Permissions and Supported Actions

You can use Identity and Access Management (IAM) for fine-grained permissions management of your OBS resources. If your does not need individual IAM users, you can skip this section.

With IAM, you can control access to specific resources from principals. Principals can request operations on resources. They include IAM users, user groups, IAM agencies, and trust agencies. IAM supports role/policy-based authorization and identity policy-based authorization.

The following table describes the differences between these two authorization models.

Table 1 Differences between role/policy-based and identity policy-based authorization

Authorization Model

Core Relationship

Permissions

Authorization Method

Description

Roles/policies

User-permission-authorization scope
  • System-defined roles
  • System-defined policies
  • Custom policies

Assigning roles or policies to principals

To authorize a user, you need to add it to a user group first and then specify the scope of authorization. It is hard to provide fine-grained permissions control using authorization by user groups and a limited number of condition keys. This method is suitable for small and medium enterprises.

Identity policies

User-policy
  • System-defined identity policies
  • Custom identity policies
  • Assigning identity policies to principals
  • Attaching identity policies to principals

You can authorize a user by attaching an identity policy to it. User-specific authorization and a variety of key conditions allow for more fine-grained permissions control. However, this model can be hard to set up. It requires a certain amount of expertise and is suitable for medium and large enterprises.

Assume that you want to grant IAM users the permission needed to create ECSs in CN North-Beijing4 and OBS buckets in CN South-Guangzhou. With role/policy-based authorization, the administrator needs to create two custom policies and assign both to the IAM users, because both regions require authorization. With identity policy-based authorization, the administrator only needs to create one custom identity policy, configure the condition key g:RequestedRegion for the policy, and then attach the policy to the principals or grant the principals access to the specified regions. Identity policy-based authorization is more flexible than role/policy-based authorization.

Policies/identity policies and actions in the two authorization models are not interoperable. You are advised to use the identity policy-based authorization model. For example, if you use identity policy-based authorization to grant permissions to users, the actions, condition keys, and operators in a policy must be those supported by identity policy-based authorization.

If you use IAM users in your account to call an API, the IAM users must be granted the required permissions. The required permissions are determined by the actions supported by the API. Only users with the policies allowing for those actions can call the API successfully.

Assume that an IAM user wants to call an API to delete an OBS bucket. With role/policy-based authorization, the IAM user must be granted the permissions allowing for action obs:bucket:DeleteBucket. With identity policy-based authorization, the IAM user must be granted the permissions allowing for action obs:bucket:deleteBucket.

Parent Topic: Permissions and Supported Actions