A role is a virtual identity with a set of permissions provided by Tencent Cloud Cloud Access Management (CAM). Roles can be associated with policies to grant access permissions on services, actions (operations), and resources in Tencent Cloud to role entities. After these permissions are added to a role, the role can be assigned to Tencent Cloud services, allowing the services to perform operations on authorized resources on your behalf. SCF offers configuration roles and execution roles. You can use a configuration role to enable SCF to access user resources in the configuration process. You can also use an execution role to enable SCF to apply for temporary authorization for executing the code, so that the code can implement permission and resource access through the role authorization mechanism.
Policies
A policy is a syntax rule used to define and describe one or more permissions. CAM supports two types of policies: preset policies and custom policies. The former is some common permission sets created and managed by Tencent Cloud, such as super admin and cloud resource admin, which are read-only and cannot be written. The latter is user-defined permission sets that describe resource management in a more refined way. The former cannot specifically describe individual resources and has a coarse granularity, while the latter can flexibly meet differentiated permission management needs.
Permissions
A permission describes whether to allow or refuse the execution of certain operations to access certain resources under certain conditions. By default, a root account is the resource owner and has full access to all resources under it, while a sub-account does not have access to any resources. A resource creator does not automatically possess the access to the created resource and should be authorized by the resource owner instead.
Overview
When creating an SCF function, you may manipulate certain Tencent Cloud services other than SCF. Different operations may require different permissions, such as COS permissions to create and delete COS triggers, API Gateway permissions to create and delete API Gateway triggers, and COS permissions to read zipped code packages, which can be granted by configuring and selecting roles.
Configuration Roles
A configuration role is used to grant the SCF configuration the permissions to connect with other Tencent Cloud resources to access such resources within the scope of the permissions in the associated policies, including but not limited to code file access and trigger configuration. The preset policy of the configuration role supports the basic operations of function execution and covers the basic permissions required in common SCF scenarios.
Role details
The default configuration role of SCF is SCF_QcsRole, as detailed below:
Role name: SCF_QcsRole
Role entity: service-scf.qcloud.com
Role description: SCF default configuration role. This service role is used to grant SCF the permissions to configure and connect with other resources in the cloud, including but not limited to code file access and trigger configuration. The preset policy of the configuration role can support the basic operations of function execution.
Associated policies: This role is associated with the QcloudAccessForScfRole policy, which can:
Write trigger configuration information to the bucket configuration when a COS trigger is configured.
Read the trigger configuration information from the COS bucket.
Read the code zip package from the bucket when the code is updated through COS.
Create API Gateway services and APIs and publish services when an API Gateway trigger is configured.
Perform operations such as configuring and using CLS read/write access.
Perform operations such as configuring and using CMQ read/write access.
Perform operations such as configuring and using CKafka creation and lists.
Note
You can log in to the CAM console to view and modify the policies associated with the current configuration role SCF_QcsRole. However, modifying the associated policies may cause SCF to fail. Therefore, we do not recommend modifying the associated policies.
Service authorization
1. If you are using SCF for the first time, you will be prompted for service authorization when you open the SCF console, as shown below:
2. Click go to CAM to go to the “Role Management” page, and click Grant to confirm the authorization, as shown below:
3. After the authorization is confirmed, the role SCF_QcsRole will be automatically created, which can be viewed in Roles, as shown below:
Execution Roles
An execution role is used for user code, and the role entity is service-scf.qcloud.com. After you add the corresponding execution role to the function, SCF will apply for the temporary authorization for your code to run within the scope of the permissions in the policies associated with the execution role, so that the code can get the required permissions and access other Tencent Cloud resources through the role authorization mechanism.
Take SCF_QcsRole as an example. You can also select SCF_QcsRole as the function execution role to grant the corresponding permissions of the policies associated with the SCF_QcsRole to SCF, so that SCF can get the permission to apply for access to other Tencent Cloud resources for your code.
Creating execution roles
1. Log in to the SCF console and click Functions in the left sidebar.
2. On the Functions page, click the name of the target function to go to the function configuration page.
3. Click Edit in the upper-right corner of the Function configuration page.
4. Select Enable for Execution Role and click Create execution role, as shown below:
5. In the Enter Role Entity Info step, select Serverless Cloud Function (scf) and click Next.
6. In the Configure role policy step, select all the policies required by the function and click Next as shown below:
Note
In this example, QcloudCOSFullAccess (full access permissions of COS) is selected. Please select the policies as needed.
7. Specify Role name in the Review step and click Complete. This document uses the role name scf_cos_full_access as an example.
8. Return to the Function configuration page, click
on the right of "Execution Role", and then select the execution role created just now from the drop-down list, as shown below:
Note
When adding policies to an execution role, in addition to preset policies, you can also select custom policies to configure permissions in a more refined manner. SCF policy syntax follows the syntax structure and resource description method of CAM, and is based on the JSON format. For more information, see SCF Policy Syntax.
Getting the temporary key information of an execution role
When a function is running, the SCF service will use the selected execution role to apply for the temporary SecretId, SecretKey, and SesstionToken.
For functions not created based on an image:
They are passed in to the runtime environment in the form of environment variable as shown below:
Take Python as an example. You can run the following code to pass in the above information to the function runtime environment and get it in the form of environment variables:
For functions created based on an image:
They are passed in to the input parameter context in the form of an HTTP header. For more information, see Feature Description.
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