sqs-dg-2009-02-01

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Amazon Simple Queue Service Developer Guide Shared Queues Shared Queues Topics • Simple API for Shared Queues (p. 29) • Advanced API for Shared Queues (p. 29) • Understanding Permissions (p. 29) • Granting Anonymous Access to a Queue (p. 30) Amazon SQS includes methods to share your queues so others can use them, using permissions set in an access control policy. A permission gives access to another person to use your queue in some particular way. A policy is the actual document that contains the permissions you've granted. Amazon SQS offers two methods for setting a policy: a simple API and an advanced API. In the simple API, SQS generates an access control policy for you. In the advanced API, you create the access control policy. Simple API for Shared Queues The simple API for sharing a queue has two operations: • AddPermission • RemovePermission With the Simple API, Amazon SQS writes the policy in the required language for you based on the information you include in the AddPermission operation. However, the policy that Amazon SQS generates is limited in scope. You can grant permissions to principals, but you can't specify restrictions. Advanced API for Shared Queues With the advanced API, you write the policy yourself directly in the access policy language and upload the policy with the SetQueueAttributes operation. The advanced API allows you to deny access or to apply finer access restrictions (for example, based on time or based on IP address). If you choose to write your own policies, you need to understand how policies are structured. For complete reference information about policies, see Using The Access Policy Language (p. 32). For examples of policies, see Amazon SQS Policy Examples (p. 57). Understanding Permissions A permission is the type of access you give to a principal (the user receiving the permission). You give each permission a label that identifies that permission. If you want to delete that permission in the future, you use that label to identify the permission. If you want to see what permissions are on a queue, use the GetQueueAttributes operation. Amazon SQS returns the entire policy (containing all the permissions). Amazon SQS supports the permission types shown in the following table. Permission * ReceiveMessage Description This permission type grants the following actions to a principal on a shared queue: receive messages, send messages, delete messages, change a message's visibility, get a queue's attributes. This grants permission to receive messages in the queue. API Version 2009-02-01 29
Amazon Simple Queue Service Developer Guide Granting Anonymous Access to a Queue Permission SendMessage DeleteMessage ChangeMessageVisibility GetQueueAttributes Description This grants permission to send messages to the queue. This grants permission to delete messages from the queue. This grants permission to extend or terminate the read lock timeout of a specified message. For more information about visibility timeout, see Visibility Timeout (p. 8). For more information about this permission type, see the ChangeMessageVisibility operation. This grants permission to receive all of the queue attributes except the policy, which can only be accessed by the queue's owner. For more information, see the GetQueueAttributes operation.. Permissions for each of the different permission types are considered separate permissions by Amazon SQS, even though * includes the access provided by the other permission types. For example, it is possible to grant both * and SendMessage permissions to a user, even though a * includes the access provided by SendMessage. This concept applies when you remove a permission. If a principal has only a * permission, requesting to remove a SendMessage permission does not leave the principal with an "everything but" permission. Instead, the request does nothing, because the principal did not previously possess an explicit SendMessage permission. If you want to remove * and leave the principal with just the ReceiveMessage permission, first add the ReceiveMessage permission, then remove the * permission. Tip You give each permission a label that identifies that permission. If you want to delete that permission in the future, you use that label to identify the permission. Note If you want to see what permissions are on a queue, use the GetQueueAttributes operation. The entire policy (containing all the permissions) is returned. Granting Anonymous Access to a Queue You can allow shared queue access to anonymous users. Such access requires no signature or Access Key ID. To allow anonymous access you must write your own policy, setting the Principal to *. For information about writing your own policies, see Using The Access Policy Language (p. 32). Caution Keep in mind that the queue owner is responsible for all costs related to the queue. Therefore you probably want to limit anonymous access in some other way (by time or IP address, for example). API Version 2009-02-01 30
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