Permissions

If you need to assign different permissions to personnel in your enterprise to access your BMSs, Identity and Access Management (IAM) is a good choice for fine-grained permissions management. IAM provides identity authentication, permissions management, and access control, helping you securely access your Huawei Cloud resources. If your Huawei Cloud account does not require IAM for permissions management, you can skip this section.

IAM is a free service. You only pay for the resources in your account.

With IAM, you can control access to specific Huawei Cloud resources. For example, if you want some software developers in your enterprise to use BMSs but do not want them to delete BMSs or perform any other high-risk operations, you can grant permission to use BMSs but not permission to delete them.

IAM supports role/policy-based authorization and identity policy-based authorization.

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

**Table 1** Differences between role/policy-based and identity policy-based authorization
Authorization Model	Core Relationship	Permissions	Authorization Method	Description
Role/Policy	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 provides a limited number of condition keys and cannot meet the requirements of fine-grained permissions control. This method is suitable for small- and medium-sized enterprises.
Identity policy	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-sized enterprises.

Assume that you want to grant IAM users permission 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. With identity policy-based authorization, the administrator only needs to create one custom identity policy and configure the condition key g:RequestedRegion for the policy, and then attach the policy to the users or grant the users the access permissions 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 details about system-defined permissions in the two authorization models, see System-defined Permissions in Role/Policy-based Authorization and System-defined Permissions in Identity Policy-based Authorization.

For more information about IAM, see IAM Service Overview.

System-defined Permissions in Role/Policy-based Authorization

BMS supports authorization with roles and policies. New IAM users do not have any permissions assigned by default. You need to first add them to one or more groups and attach policies or roles to these groups. The users then inherit permissions from the groups and can perform specified operations on cloud services based on the permissions they have been assigned.

BMS is a project-level service deployed for specific regions. When you set Scope to Region-specific projects and select the specified projects (for example, ap-southeast-2) in the specified regions (for example, AP-Bangkok), the users only have permissions for BMSs in the selected projects. If you set Scope to All resources, users have permissions for BMSs in all region-specific projects. When accessing BMSs, the users need to switch to the authorized region.

Table 2 lists all the system-defined permissions for BMS. System-defined policies in role/policy-based authorization are not interoperable with those in identity policy-based authorization.

**Table 2** System-defined permissions for BMS
Role/Policy Name	Description	Type	Dependencies
BMS FullAccess	Administrator permissions for BMS. Users with these permissions can perform all operations on BMSs.	System-defined policy	None
BMS CommonOperations	Common user permissions for BMS. Users with these permissions can start, stop, restart, and query BMSs.	System-defined policy	None
BMS ReadOnlyAccess	Read-only permissions for BMS. Users with these permissions can only view BMS data.	System-defined policy	None

Table 3 lists the common operations supported by system-defined permissions for BMS.

**Table 3** Common operations supported by system-defined permissions
Operation	BMS FullAccess	BMS CommonOperations	BMS ReadOnlyAccess
Creating BMSs	√	x	x
Querying BMSs	√	√	√
Querying BMS details	√	√	√
Changing the name of a BMS	√	x	x
Starting a BMS	√	√	x
Stopping a BMS	√	√	x
Restarting a BMS	√	√	x
Attaching a data disk to a BMS	√	√	x
Detaching a data disk from a BMS	√	√	x
Reinstalling a BMS OS	√	x	x
Resetting a BMS password with a few clicks	√	x	x

System-defined Permissions in Identity Policy-based Authorization

BMS supports authorization with identity policies. Table 4 lists all the system-defined identity policies for BMS. System-defined policies in identity policy-based authorization are not interoperable with those in role/policy-based authorization.

**Table 4** System-defined identity policies for BMS
Identity Policy Name	Description	Type
BMSFullPolicy	Administrator permissions for BMS. Users with these permissions can perform all operations on BMSs.	System-defined identity policy
BMSCommonOperationsPolicy	Common user permissions for BMS. Users with these permissions can start, stop, restart, and query BMSs.	System-defined identity policy
BMSReadOnlyPolicy	Read-only permissions for BMS. Users with these permissions can only view BMS data.	System-defined identity policy

Table 5 lists the common operations supported by system-defined identity policies for BMS.

**Table 5** Common operations supported by system-defined identity policies
Operation	BMSFullPolicy	BMSCommonOperationsPolicy	BMSReadOnlyPolicy
Creating BMSs	√	x	x
Querying BMSs	√	√	√
Querying BMS details	√	√	√
Changing the name of a BMS	√	x	x
Starting a BMS	√	√	x
Stopping a BMS	√	√	x
Restarting a BMS	√	√	x
Attaching a data disk to a BMS	√	√	x
Detaching a data disk from a BMS	√	√	x
Reinstalling a BMS OS	√	x	x
Resetting a BMS password with a few clicks	√	x	x