How Amazon S3 works with IAM
Before you use IAM to manage access to Amazon S3, learn what IAM features are available to use with Amazon S3.
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To get a high-level view of how Amazon S3 and other AWS services work with most IAM features, see AWS services that work with IAM in the IAM User Guide.
For more information about the permissions to S3 API operations by S3 resource types, see Required permissions for Amazon S3 API operations.
Identity-based policies for Amazon S3
Supports identity-based policies: Yes
Identity-based policies are JSON permissions policy documents that you can attach to an identity, such as an IAM user, group of users, or role. These policies control what actions users and roles can perform, on which resources, and under what conditions. To learn how to create an identity-based policy, see Creating IAM policies in the IAM User Guide.
With IAM identity-based policies, you can specify allowed or denied actions and resources as well as the conditions under which actions are allowed or denied. You can't specify the principal in an identity-based policy because it applies to the user or role to which it is attached. To learn about all of the elements that you can use in a JSON policy, see IAM JSON policy elements reference in the IAM User Guide.
Identity-based policy examples for Amazon S3
To view examples of Amazon S3 identity-based policies, see Identity-based policies for Amazon S3.
Resource-based policies within Amazon S3
Supports resource-based policies: Yes
Resource-based policies are JSON policy documents that you attach to a resource. Examples of resource-based policies are IAM role trust policies and Amazon S3 bucket policies. In services that support resource-based policies, service administrators can use them to control access to a specific resource. For the resource where the policy is attached, the policy defines what actions a specified principal can perform on that resource and under what conditions. You must specify a principal in a resource-based policy. Principals can include accounts, users, roles, federated users, or AWS services.
To enable cross-account access, you can specify an entire account or IAM entities in another account as the principal in a resource-based policy. Adding a cross-account principal to a resource-based policy is only half of establishing the trust relationship. When the principal and the resource are in different AWS accounts, an IAM administrator in the trusted account must also grant the principal entity (user or role) permission to access the resource. They grant permission by attaching an identity-based policy to the entity. However, if a resource-based policy grants access to a principal in the same account, no additional identity-based policy is required. For more information, see Cross account resource access in IAM in the IAM User Guide.
The Amazon S3 service supports bucket policies, access points policies, and access grants:
-
Bucket policies are resource-based policies that are attached to an Amazon S3 bucket. A bucket policy defines which principals can perform actions on the bucket.
-
Access point policies are resource-based polices that are evaluated in conjunction with the underlying bucket policy.
-
Access grants are a simplified model for defining access permissions to data in Amazon S3 by prefix, bucket, or object. For information about S3 Access Grants, see Managing access with S3 Access Grants.
Principals for bucket policies
The Principal
element specifies the user, account, service, or other
entity that is either allowed or denied access to a resource.
The following are examples of specifying Principal
. For more
information, see Principal
in the IAM User Guide.
Grant permissions to an AWS account
To grant permissions to an AWS account, identify the account using the following format.
"AWS":"
account-ARN
"
The following are examples.
"Principal":{"AWS":"arn:aws:iam::
AccountIDWithoutHyphens
:root"}
"Principal":{"AWS":["arn:aws:iam::
AccountID1WithoutHyphens
:root","arn:aws:iam::AccountID2WithoutHyphens
:root"]}
Grant permissions to an IAM user
To grant permission to an IAM user within your account, you must provide an
"AWS":"
name-value
pair.user-ARN
"
"Principal":{"AWS":"arn:aws:iam::
account-number-without-hyphens
:user/username
"}
For detailed examples that provide step-by-step instructions, see Example 1: Bucket owner granting its users bucket permissions and Example 3: Bucket owner granting permissions to objects it does not own.
Note
If an IAM identity is deleted after you update your bucket policy, the bucket policy will show a unique identifier in the principal element instead of an ARN. These unique IDs are never reused, so you can safely remove principals with unique identifiers from all of your policy statements. For more information about unique identifiers, see IAM identifiers in the IAM User Guide.
Grant anonymous permissions
Warning
Use caution when granting anonymous access to your Amazon S3 bucket. When you grant anonymous access, anyone in the world can access your bucket. We highly recommend that you never grant any kind of anonymous write access to your S3 bucket.
To grant permission to everyone, also referred as anonymous access, you set
the wildcard ("*"
) as the Principal
value. For
example, if you configure your bucket as a website, you want all the objects in
the bucket to be publicly accessible.
"Principal":"*"
"Principal":{"AWS":"*"}
Using "Principal": "*"
with an Allow
effect in a
resource-based policy allows anyone, even if they’re not signed in to AWS, to
access your resource.
Using "Principal" : { "AWS" : "*" }
with an Allow
effect in a resource-based policy allows any root user, IAM user, assumed-role
session, or federated user in any account in the same partition to access your
resource.
For anonymous users, these two methods are equivalent. For more information, see All principals in the IAM User Guide.
You cannot use a wildcard to match part of a principal name or ARN.
Important
Because anyone can create an AWS account, the security level of these two methods is equivalent, even though they function differently.
Restrict resource permissions
You can also use resource policy to restrict access to resources that would otherwise be available to IAM principals. Use a Deny
statement to prevent access.
The following example blocks access if a secure transport protocol isn’t used:
{"Effect": "Deny", "Principal": "*", "Action": "s3:*", "Resource": <bucket ARN>, "Condition": { "Boolean": { "aws:SecureTransport" : "false"} } }
Using "Principal": "*"
so that this restriction applies to everyone is a best practice for this policy, instead of attempting to deny access only to specific accounts or principals using this method.
Require access through CloudFront URLs
You can require that your users access your Amazon S3 content only by using CloudFront URLs instead of Amazon S3 URLs. To do this, create a CloudFront origin access control (OAC). Then, change the permissions on your S3 data. In your bucket policy, you can set CloudFront as the Principal as follows:
"Principal":{"Service":"cloudfront.amazonaws.com"}
Use a Condition
element in the policy to allow CloudFront to access the bucket only when the request is on behalf of the CloudFront distribution that contains the S3 origin.
"Condition": { "StringEquals": { "AWS:SourceArn": "arn:aws:cloudfront::
111122223333
:distribution/CloudFront-distribution-ID
" } }
For more information about requiring S3 access through CloudFront URLs, see Restricting access to an Amazon Simple Storage Service origin in the Amazon CloudFront Developer Guide. For more information about the security and privacy benefits of using Amazon CloudFront, see Configuring secure access and restricting access to content.
Resource-based policy examples for Amazon S3
To view policy examples for Amazon S3 buckets, see Bucket policies for Amazon S3.
To view policy examples for access points, see Configuring IAM policies for using access points.
Policy actions for Amazon S3
Supports policy actions: Yes
Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.
The Action
element of a JSON policy describes the
actions that you can use to allow or deny access in a policy. Policy
actions usually have the same name as the associated AWS API operation. There are some exceptions, such as permission-only
actions that don't have a matching API operation. There are also some operations that require multiple actions in a policy.
These additional actions are called dependent actions.
Include actions in a policy to grant permissions to perform the associated operation.
The following shows different types of mapping relationship between S3 API operations and the required policy actions.
One-to-one mapping with the same name. For example, to use the
PutBucketPolicy
API operation, thes3:PutBucketPolicy
policy action is required.One-to-one mapping with different names. For example, to use the
ListObjectsV2
API operation, thes3:ListBucket
policy action is required.One-to-many mapping. For example, to use the
HeadObject
API operation, thes3:GetObject
is required. Also, when you use S3 Object Lock and want to get an object's Legal Hold status or retention settings, the correspondings3:GetObjectLegalHold
ors3:GetObjectRetention
policy actions are also required before you can use theHeadObject
API operation.Many-to-one mapping. For example, to use the
ListObjectsV2
orHeadBucket
API operations, thes3:ListBucket
policy action is required.
To see a list of Amazon S3 actions for use in policies, see Actions defined by Amazon S3 in the Service Authorization Reference. For a complete list of Amazon S3 API operations, see Amazon S3 API Actions in the Amazon Simple Storage Service API Reference.
For more information about the permissions to S3 API operations by S3 resource types, see Required permissions for Amazon S3 API operations.
Policy actions in Amazon S3 use the following prefix before the action:
s3
To specify multiple actions in a single statement, separate them with commas.
"Action": [ "s3:
action1
", "s3:action2
" ]
Bucket operations
Bucket operations are S3 API operations that operate on the bucket resource type. For
example, CreateBucket
, ListObjectsV2
, and
PutBucketPolicy
. S3 policy actions for bucket operations
require the Resource
element in bucket policies or IAM
identity-based policies to be the S3 bucket type Amazon Resource Name (ARN) identifier in the following
example format.
"Resource": "arn:aws:s3:::
amzn-s3-demo-bucket
"
The following bucket policy grants the user
with account
Akua
the
12345678901
s3:ListBucket
permission to perform the ListObjectsV2
API operation and list objects in an S3 bucket.
{ "Version": "2012-10-17", "Statement": [ { "Sid": "Allow Akua to list objects in the bucket", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::
12345678901
:user/Akua" }, "Action": [ "s3:ListBucket" ], "Resource": "arn:aws:s3:::amzn-s3-demo-bucket
" } ] }
Bucket operations in access point policies
Permissions granted in an access point policy are effective only if the underlying
bucket allows the same permissions. When you use S3 Access Points, you must
delegate access control from the bucket to the access point or add the same permissions in
the access point policies to the underlying bucket's policy. For more information, see
Configuring IAM policies for using access points. In access point policies, S3 policy actions for bucket operations require you to use
the access point ARN for the Resource
element in the following
format.
"Resource": "arn:aws:s3:
us-west-2
:123456789012
:accesspoint/example-access-point
"
The following access point policy grants the user
with account
Akua
the
12345678901
s3:ListBucket
permission to perform the ListObjectsV2 API operation through the S3 access point named
. This permission
allows example-access-point
to list the objects in the bucket
that's associated with Akua
. example-access-point
{ "Version": "2012-10-17", "Statement": [ { "Sid": "Allow
Akua
to list objects in the bucket through access point", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::12345678901
:user/Akua
" }, "Action": [ "s3:ListBucket" ], "Resource": "arn:aws:s3:us-west-2
:123456789012
:accesspoint/example-access-point
" } ] }
Note
Not all bucket operations are supported by S3 Access Point. For more information, see Access point compatibility with S3 operations.
Object operations
Object operations are S3 API operations that act upon the object resource type. For
example, GetObject
, PutObject
, and
DeleteObject
. S3 policy actions for object operations require
the Resource
element in policies to be the S3 object ARN in the
following example formats.
"Resource": "arn:aws:s3:::
amzn-s3-demo-bucket
/*"
"Resource": "arn:aws:s3:::
amzn-s3-demo-bucket
/prefix
/*"
Note
The object ARN must contain a forward slash after the bucket name, as seen in the previous examples.
The following bucket policy grants the user
with account
Akua
the
12345678901
s3:PutObject
permission. This permission allows
to use the PutObject API operation to upload objects to the S3
bucket named
Akua
.amzn-s3-demo-bucket
{ "Version": "2012-10-17", "Statement": [ { "Sid": "Allow
Akua
to upload objects", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::12345678901
:user/Akua
" }, "Action": [ "s3:PutObject" ], "Resource": "arn:aws:s3:::amzn-s3-demo-bucket
/*" } ] }
Object operations in access point policies
When you use S3 Access Points to control access to object operations, you can
use access point policies. When you use access point policies, S3 policy actions for object
operations require you to use the access point ARN for the Resource
element in the following format:
arn:aws:s3:
.
For object operations that use access points, you must include the
region
:account-id
:accesspoint/access-point-name
/object/resource
/object/
value after the whole access point ARN in the
Resource
element. Here are some examples.
"Resource": "arn:aws:s3:
us-west-2
:123456789012
:accesspoint/example-access-point
/object/*"
"Resource": "arn:aws:s3:
us-west-2
:123456789012
:accesspoint/example-access-point
/object/prefix
/*"
The following access point policy grants the user
with account
Akua
the
12345678901
s3:GetObject
permission. This permission allows
to perform the GetObject API operation through the access point named
Akua
on all objects in
the bucket that's associated with the access point. example-access-point
{ "Version": "2012-10-17", "Statement": [ { "Sid": "Allow
Akua
to get objects through access point", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::12345678901
:user/Akua
" }, "Action": [ "s3:GetObject" ], "Resource": "arn:aws:s3:us-west-2
:123456789012
:accesspoint/example-access-point
/object/*" } ] }
Note
Not all object operations are supported by access points. For more information, see Access point compatibility with S3 operations.
Access point operations
Access point operations are S3 API operations that operate on the
accesspoint
resource type. For example,
CreateAccessPoint
, DeleteAccessPoint
, and
GetAccessPointPolicy
. S3 policy actions for access point operations can only
be used in IAM identity-based policies, not in bucket policies or access point policies.
Access points operations require the Resource
element to be the access
point ARN in the following example format.
"Resource": "arn:aws:s3:
us-west-2
:123456789012
:accesspoint/example-access-point
"
The following IAM identity-based policy grants the
s3:GetAccessPointPolicy
permission to perform the GetAccessPointPolicy API operation on
the S3 access point named
.example-access-point
{ "Version": "2012-10-17", "Statement": [ { "Sid": "Grant permission to retrieve the access point policy of access point
example-access-point
", "Effect": "Allow", "Action": [ "s3:GetAccessPointPolicy" ], "Resource": "arn:aws:s3:*:123456789012
:accesspoint/example-access-point
" } ] }
When you use Access Points, to control access to bucket operations, see Bucket operations in access point policies; to control access to object operations, see Object operations in access point policies. For more information about how to configure access point policies, see Configuring IAM policies for using access points.
Object Lambda Access Point operations
With Amazon S3 Object Lambda, you can add your own code to Amazon S3 GET
, LIST
,
and HEAD
requests to modify and process data as it is returned to an
application. You can make requests through an Object Lambda Access Point, which works the same as making requests through other access points. For more information, see Transforming objects with S3 Object Lambda.
For more information about how to configure policies for Object Lambda Access Point operations, see Configuring IAM policies for Object Lambda Access Points.
Multi-Region Access Point operations
A Multi-Region Access Point provides a global endpoint that applications can use to fulfill requests from S3 buckets that are located in multiple AWS Region. You can use a Multi-Region Access Point to build multi-Region applications with the same architecture that's used in a single Region, and then run those applications anywhere in the world. For more information, see Managing multi-Region traffic with Multi-Region Access Points.
For more information about how to configure policies for Multi-Region Access Point operations, see Multi-Region Access Point policy examples.
Batch job operations
(Batch Operations) job operations are S3 API operations that operate on the job resource type.
For example, DescribeJob
and CreateJob
. S3 policy
actions for job operations can only be used in IAM identity-based policies,
not in bucket policies. Also, job operations require the Resource
element in IAM identity-based policies to be the job
ARN in the
following example format.
"Resource": "arn:aws:s3:*:
123456789012
:job/*"
The following IAM identity-based policy grants the s3:DescribeJob
permission to perform the DescribeJob API operation
on the S3 Batch Operations job named
.example-job
{ "Version": "2012-10-17", "Statement": [ { "Sid": "Allow describing the Batch operation job
example-job
", "Effect": "Allow", "Action": [ "s3:DescribeJob" ], "Resource": "arn:aws:s3:*:123456789012
:job/example-job
" } ] }
S3 Storage Lens configuration operations
For more information about how to configure S3 Storage Lens configuration operations, see Setting Amazon S3 Storage Lens permissions.
Account operations
Account operations are S3 API operations that operate on the account level. For example, GetPublicAccessBlock
(for account). Account isn't a resource type defined by Amazon S3.
S3 policy actions for account operations can only be used in IAM identity-based policies, not in bucket policies. Also, account operations require the Resource
element in IAM identity-based policies to be "*"
.
The following IAM identity-based policy grants the
s3:GetAccountPublicAccessBlock
permission to perform the
account-level GetPublicAccessBlock API operation and retrieve the
account-level Public Access Block settings.
{ "Version":"2012-10-17", "Statement":[ { "Sid":"Allow retrieving the account-level Public Access Block settings", "Effect":"Allow", "Action":[ "s3:GetAccountPublicAccessBlock" ], "Resource":[ "*" ] } ] }
Policy examples for Amazon S3
-
To view examples of Amazon S3 identity-based policies, see Identity-based policies for Amazon S3.
-
To view examples of Amazon S3 resource-based policies, see Bucket policies for Amazon S3 and Configuring IAM policies for using access points.
Policy resources for Amazon S3
Supports policy resources: Yes
Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.
The Resource
JSON policy element specifies the object or objects to which the action applies. Statements must include either a
Resource
or a NotResource
element. As a best practice, specify a resource using its Amazon Resource Name (ARN). You can do this for actions that support a
specific resource type, known as resource-level permissions.
For actions that don't support resource-level permissions, such as listing operations, use a wildcard (*) to indicate that the statement applies to all resources.
"Resource": "*"
Some Amazon S3 API actions support multiple resources. For example,
s3:GetObject
accesses
and
example-resource-1
, so a principal must
have permissions to access both resources. To specify multiple resources in a single
statement, separate the ARNs with commas, as shown in the following example. example-resource-2
"Resource": [ "
example-resource-1
", "example-resource-2
"
Resources in Amazon S3 are buckets, objects, access points, or jobs. In a policy, use the Amazon Resource Name (ARN) of the bucket, object, access point, or job to identify the resource.
To see a complete list of Amazon S3 resource types and their ARNs, see Resources defined by Amazon S3 in the Service Authorization Reference. To learn with which actions you can specify the ARN of each resource, see Actions defined by Amazon S3.
For more information about the permissions to S3 API operations by S3 resource types, see Required permissions for Amazon S3 API operations.
Wildcard characters in resource ARNs
You can use wildcard characters as part of the resource ARN. You can use the
wildcard characters (*
and ?
) within any ARN segment (the
parts separated by colons). An asterisk (*
) represents any combination
of zero or more characters, and a question mark (?
) represents any
single character. You can use multiple *
or ?
characters in
each segment. However, a wildcard character can't span segments.
-
The following ARN uses the
*
wildcard character in therelative-ID
part of the ARN to identify all objects in the
bucket.amzn-s3-demo-bucket
arn:aws:s3:::
amzn-s3-demo-bucket
/* -
The following ARN uses
*
to indicate all S3 buckets and objects.arn:aws:s3:::*
-
The following ARN uses both of the wildcard characters,
*
and?
, in therelative-ID
part. This ARN identifies all objects in buckets such as
,amzn-s3-demo-example1bucket
,amzn-s3-demo-example2bucket
, and so on.amzn-s3-demo-example3bucket
arn:aws:s3:::
amzn-s3-demo-example
?bucket
/*
Policy variables for resource ARNs
You can use policy variables in Amazon S3 ARNs. At policy-evaluation time, these predefined variables are replaced by their corresponding values. Suppose that you organize your bucket as a collection of folders, with one folder for each of your users. The folder name is the same as the username. To grant users permission to their folders, you can specify a policy variable in the resource ARN:
arn:aws:s3:::
bucket_name
/developers
/${aws:username}/
At runtime, when the policy is evaluated, the variable
${aws:username}
in the resource ARN is substituted with the username
of the person who is making the request.
Policy examples for Amazon S3
-
To view examples of Amazon S3 identity-based policies, see Identity-based policies for Amazon S3.
-
To view examples of Amazon S3 resource-based policies, see Bucket policies for Amazon S3 and Configuring IAM policies for using access points.
Policy condition keys for Amazon S3
Supports service-specific policy condition keys: Yes
Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.
The Condition
element (or Condition
block) lets you specify conditions in which a
statement is in effect. The Condition
element is optional. You can create
conditional expressions that use condition
operators, such as equals or less than, to match the condition in the
policy with values in the request.
If you specify multiple Condition
elements in a statement, or
multiple keys in a single Condition
element, AWS evaluates them using
a logical AND
operation. If you specify multiple values for a single
condition key, AWS evaluates the condition using a logical OR
operation. All of the conditions must be met before the statement's permissions are
granted.
You can also use placeholder variables when you specify conditions. For example, you can grant an IAM user permission to access a resource only if it is tagged with their IAM user name. For more information, see IAM policy elements: variables and tags in the IAM User Guide.
AWS supports global condition keys and service-specific condition keys. To see all AWS global condition keys, see AWS global condition context keys in the IAM User Guide.
Each Amazon S3 condition key maps to the same name request header allowed by the API
on which the condition can be set. Amazon S3‐specific condition keys dictate the
behavior of the same name request headers. For example, the condition key
s3:VersionId
used to grant conditional permission for the s3:GetObjectVersion
permission defines behavior of the
versionId
query parameter that you set in a GET Object request.
To see a list of Amazon S3 condition keys, see Condition keys for Amazon S3 in the Service Authorization Reference. To learn with which actions and resources you can use a condition key, see Actions defined by Amazon S3.
Example: Restricting object uploads to objects with a specific storage class
Suppose that Account A, represented by account ID
, owns a bucket. The
Account A administrator wants to restrict
123456789012
, a user in Account A, so that
Dave
can upload objects to the bucket
only if the object is stored in the Dave
STANDARD_IA
storage class. To
restrict object uploads to a specific storage class, the Account A administrator can
use the s3:x-amz-storage-class
condition key, as shown in the following
example bucket policy.
{ "Version": "2012-10-17", "Statement": [ { "Sid": "statement1", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::
123456789012
:user/Dave
" }, "Action": "s3:PutObject", "Resource": "arn:aws:s3:::amzn-s3-demo-bucket1
/*", "Condition": { "StringEquals": { "s3:x-amz-storage-class": [ "STANDARD_IA" ] } } } ] }
In the example, the Condition
block specifies the
StringEquals
condition that is applied to the specified key-value pair,
"s3:x-amz-acl":["public-read"]
. There is a set of predefined keys that
you can use in expressing a condition. The example uses the s3:x-amz-acl
condition key. This condition requires the user to include the x-amz-acl
header with value public-read
in every PutObject
request.
Policy examples for Amazon S3
-
To view examples of Amazon S3 identity-based policies, see Identity-based policies for Amazon S3.
-
To view examples of Amazon S3 resource-based policies, see Bucket policies for Amazon S3 and Configuring IAM policies for using access points.
ACLs in Amazon S3
Supports ACLs: Yes
In Amazon S3, access control lists (ACLs) control which AWS accounts have permissions to access a resource. ACLs are similar to resource-based policies, although they do not use the JSON policy document format.
Important
A majority of modern use cases in Amazon S3 no longer require the use of ACLs.
For information about using ACLs to control access in Amazon S3, see Managing access with ACLs.
ABAC with Amazon S3
Supports ABAC (tags in policies): Partial
Attribute-based access control (ABAC) is an authorization strategy that defines permissions based on attributes. In AWS, these attributes are called tags. You can attach tags to IAM entities (users or roles) and to many AWS resources. Tagging entities and resources is the first step of ABAC. Then you design ABAC policies to allow operations when the principal's tag matches the tag on the resource that they are trying to access.
ABAC is helpful in environments that are growing rapidly and helps with situations where policy management becomes cumbersome.
To control access based on tags, you provide tag information in the condition
element of a policy using the
aws:ResourceTag/
,
key-name
aws:RequestTag/
, or
key-name
aws:TagKeys
condition keys.
If a service supports all three condition keys for every resource type, then the value is Yes for the service. If a service supports all three condition keys for only some resource types, then the value is Partial.
For more information about ABAC, see What is ABAC? in the IAM User Guide. To view a tutorial with steps for setting up ABAC, see Use attribute-based access control (ABAC) in the IAM User Guide.
To view example identity-based policies for limiting access to S3 Batch Operations jobs based on tags, see Controlling permissions for Batch Operations using job tags.
ABAC and object tags
In ABAC policies, objects use s3:
tags instead of aws:
tags. To control access to objects based on object tags, you provide tag information
in the Condition element of a policy using the following
tags:
-
s3:ExistingObjectTag/
tag-key
-
s3:s3:RequestObjectTagKeys
-
s3:RequestObjectTag/
tag-key
For information about using object tags to control access, including example permission policies, see Tagging and access control policies.
Using temporary credentials with Amazon S3
Supports temporary credentials: Yes
Some AWS services don't work when you sign in using temporary credentials. For additional information, including which AWS services work with temporary credentials, see AWS services that work with IAM in the IAM User Guide.
You are using temporary credentials if you sign in to the AWS Management Console using any method except a user name and password. For example, when you access AWS using your company's single sign-on (SSO) link, that process automatically creates temporary credentials. You also automatically create temporary credentials when you sign in to the console as a user and then switch roles. For more information about switching roles, see Switching to a role (console) in the IAM User Guide.
You can manually create temporary credentials using the AWS CLI or AWS API. You can then use those temporary credentials to access AWS. AWS recommends that you dynamically generate temporary credentials instead of using long-term access keys. For more information, see Temporary security credentials in IAM.
Forward access sessions for Amazon S3
Supports forward access sessions (FAS): Yes
When you use an IAM user or role to perform actions in AWS, you are considered a principal. When you use some services, you might perform an action that then initiates another action in a different service. FAS uses the permissions of the principal calling an AWS service, combined with the requesting AWS service to make requests to downstream services. FAS requests are only made when a service receives a request that requires interactions with other AWS services or resources to complete. In this case, you must have permissions to perform both actions. For policy details when making FAS requests, see Forward access sessions.
FAS is used by Amazon S3 to make calls to AWS KMS to decrypt an object when SSE-KMS was used to encrypt it. For more information, see Using server-side encryption with AWS KMS keys (SSE-KMS).
S3 Access Grants also uses FAS. After you create an access grant to your S3 data for a particular identity, the grantee requests a temporary credential from S3 Access Grants. S3 Access Grants obtains a temporary credential for the requester from AWS STS and vends the credential to the requester. For more information, see Request access to Amazon S3 data through S3 Access Grants.
Service roles for Amazon S3
Supports service roles: Yes
A service role is an IAM role that a service assumes to perform actions on your behalf. An IAM administrator can create, modify, and delete a service role from within IAM. For more information, see Creating a role to delegate permissions to an AWS service in the IAM User Guide.
Warning
Changing the permissions for a service role might break Amazon S3 functionality. Edit service roles only when Amazon S3 provides guidance to do so.
Service-linked roles for Amazon S3
Supports service-linked roles: Partial
A service-linked role is a type of service role that is linked to an AWS service. The service can assume the role to perform an action on your behalf. Service-linked roles appear in your AWS account and are owned by the service. An IAM administrator can view, but not edit the permissions for service-linked roles.
Amazon S3 supports service-linked roles for Amazon S3 Storage Lens. For details about creating or managing Amazon S3 service-linked roles, see Using service-linked roles for Amazon S3 Storage Lens.
Amazon S3 Service as a Principal
Service name in the policy | S3 feature | More information |
---|---|---|
|
S3 Replication |
|
|
S3 event notifications |
|
|
S3 Inventory |
|
|
S3 Access Grants |
|
|
S3 Batch Operations |
|
|
S3 Server Access Logging |
|
|
S3 Storage Lens |