Identity-based policy examples for Amazon S3

This section shows several example AWS Identity and Access Management (IAM) identity-based policies for controlling access to Amazon S3. For example bucket policies (resource-based policies), see Bucket policies for Amazon S3. For information about IAM policy language, see Policies and permissions in Amazon S3.

The following example policies will work if you use them programmatically. However, to use them with the Amazon S3 console, you must grant additional permissions that are required by the console. For information about using policies such as these with the Amazon S3 console, see Controlling access to a bucket with user policies.

For more information about the permissions to S3 API operations by S3 resource types, see Required permissions for Amazon S3 API operations.

Allowing an IAM user access to one of your buckets

In this example, you want to grant an IAM user in your AWS account access to one of your buckets, amzn-s3-demo-bucket1, and allow the user to add, update, and delete objects.

In addition to granting the s3:PutObject, s3:GetObject, and s3:DeleteObject permissions to the user, the policy also grants the s3:ListAllMyBuckets, s3:GetBucketLocation, and s3:ListBucket permissions. These are the additional permissions required by the console. Also, the s3:PutObjectAcl and the s3:GetObjectAcl actions are required to be able to copy, cut, and paste objects in the console. For an example walkthrough that grants permissions to users and tests them using the console, see Controlling access to a bucket with user policies.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Effect":"Allow",
         "Action": "s3:ListAllMyBuckets",
         "Resource":"*"
      },
      {
         "Effect":"Allow",
         "Action":["s3:ListBucket","s3:GetBucketLocation"],
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1"
      },
      {
         "Effect":"Allow",
         "Action":[
            "s3:PutObject",
            "s3:PutObjectAcl",
            "s3:GetObject",
            "s3:GetObjectAcl",
            "s3:DeleteObject"
         ],
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1/*"
      }
   ]
}

Allowing each IAM user access to a folder in a bucket

In this example, you want two IAM users, Mary and Carlos, to have access to your bucket, amzn-s3-demo-bucket1, so that they can add, update, and delete objects. However, you want to restrict each user's access to a single prefix (folder) in the bucket. You might create folders with names that match their usernames.

amzn-s3-demo-bucket1
   Mary/
   Carlos/

To grant each user access only to their folder, you can write a policy for each user and attach it individually. For example, you can attach the following policy to the user Mary to allow her specific Amazon S3 permissions on the amzn-s3-demo-bucket1/Mary folder.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Effect":"Allow",
         "Action":[
            "s3:PutObject",
            "s3:GetObject",
            "s3:GetObjectVersion",
            "s3:DeleteObject",
            "s3:DeleteObjectVersion"
         ],
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1/Mary/*"
      }
   ]
}

You can then attach a similar policy to the user Carlos, specifying the folder Carlos in the Resource value.

Instead of attaching policies to individual users, you can write a single policy that uses a policy variable and then attach the policy to a group. First, you must create a group and add both Mary and Carlos to the group. The following example policy allows a set of Amazon S3 permissions in the amzn-s3-demo-bucket1/${aws:username} folder. When the policy is evaluated, the policy variable ${aws:username} is replaced by the requester's username. For example, if Mary sends a request to put an object, the operation is allowed only if Mary is uploading the object to the amzn-s3-demo-bucket1/Mary folder.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Effect":"Allow",
         "Action":[
            "s3:PutObject",
            "s3:GetObject",
            "s3:GetObjectVersion",
            "s3:DeleteObject",
            "s3:DeleteObjectVersion"
         ],
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1/${aws:username}/*"
      }
   ]
}

If you want to test the preceding policy on the Amazon S3 console, the console requires additional permissions, as shown in the following policy. For information about how the console uses these permissions, see Controlling access to a bucket with user policies.

{
 "Version":"2012-10-17",
  "Statement": [
    {
      "Sid": "AllowGroupToSeeBucketListInTheConsole",
      "Action": [ 
      	"s3:ListAllMyBuckets", 
      	"s3:GetBucketLocation" 
      ],
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::*"  
    },
    {
      "Sid": "AllowRootLevelListingOfTheBucket",
      "Action": "s3:ListBucket",
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::amzn-s3-demo-bucket1",
      "Condition":{ 
            "StringEquals":{
                    "s3:prefix":[""], "s3:delimiter":["/"]
                           }
                 }
    },
    {
      "Sid": "AllowListBucketOfASpecificUserPrefix",
      "Action": "s3:ListBucket",
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::amzn-s3-demo-bucket1",
      "Condition":{  "StringLike":{"s3:prefix":["${aws:username}/*"] }
       }
    },
      {
     "Sid": "AllowUserSpecificActionsOnlyInTheSpecificUserPrefix",
         "Effect":"Allow",
         "Action":[
            "s3:PutObject",
            "s3:GetObject",
            "s3:GetObjectVersion",
            "s3:DeleteObject",
            "s3:DeleteObjectVersion"
         ],
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1/${aws:username}/*"
      }
  ]
} 

Although IAM user names are friendly, human-readable identifiers, they aren't required to be globally unique. For example, if the user Carlos leaves the organization and another Carlos joins, then the new Carlos could access the old Carlos's information.

Instead of using usernames, you could create folders based on IAM user IDs. Each IAM user ID is unique. In this case, you must modify the preceding policy to use the ${aws:userid} policy variable. For more information about user identifiers, see IAM Identifiers in the IAM User Guide.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Effect":"Allow",
         "Action":[
            "s3:PutObject",
            "s3:GetObject",
            "s3:GetObjectVersion",
            "s3:DeleteObject",
            "s3:DeleteObjectVersion"
         ],
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1/home/${aws:userid}/*"
      }
   ]
}

Allowing non-IAM users (mobile app users) access to folders in a bucket

Suppose that you want to develop a mobile app, a game that stores users' data in an S3 bucket. For each app user, you want to create a folder in your bucket. You also want to limit each user's access to their own folder. But you can't create folders before someone downloads your app and starts playing the game, because you don't have their user ID.

In this case, you can require users to sign in to your app by using public identity providers such as Login with Amazon, Facebook, or Google. After users have signed in to your app through one of these providers, they have a user ID that you can use to create user-specific folders at runtime.

You can then use web identity federation in AWS Security Token Service to integrate information from the identity provider with your app and to get temporary security credentials for each user. You can then create IAM policies that allow the app to access your bucket and perform such operations as creating user-specific folders and uploading data. For more information about web identity federation, see About web identity Federation in the IAM User Guide.

Allowing a group to have a shared folder in Amazon S3

Attaching the following policy to the group grants everybody in the group access to the following folder in Amazon S3: amzn-s3-demo-bucket1/share/marketing. Group members are allowed to access only the specific Amazon S3 permissions shown in the policy and only for objects in the specified folder.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Effect":"Allow",
         "Action":[
            "s3:PutObject",
            "s3:GetObject",
            "s3:GetObjectVersion",
            "s3:DeleteObject",
            "s3:DeleteObjectVersion"
         ],
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1/share/marketing/*"
      }
   ]
}

Allowing all your users to read objects in a portion of a bucket

In this example, you create a group named AllUsers, which contains all the IAM users that are owned by the AWS account. You then attach a policy that gives the group access to GetObject and GetObjectVersion, but only for objects in the amzn-s3-demo-bucket1/readonly folder.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Effect":"Allow",
         "Action":[
            "s3:GetObject",
            "s3:GetObjectVersion"
         ],
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1/readonly/*"
      }
   ]
}

Allowing a partner to drop files into a specific portion of a bucket

In this example, you create a group called AnyCompany that represents a partner company. You create an IAM user for the specific person or application at the partner company that needs access, and then you put the user in the group.

You then attach a policy that gives the group PutObject access to the following folder in a bucket:

amzn-s3-demo-bucket1/uploads/anycompany

You want to prevent the AnyCompany group from doing anything else with the bucket, so you add a statement that explicitly denies permission to any Amazon S3 actions except PutObject on any Amazon S3 resource in the AWS account.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Effect":"Allow",
         "Action":"s3:PutObject",
         "Resource":"arn:aws:s3:::amzn-s3-demo-bucket1/uploads/anycompany/*"
      },
      {
         "Effect":"Deny",
         "Action":"s3:*",
         "NotResource":"arn:aws:s3:::amzn-s3-demo-bucket1/uploads/anycompany/*"
      }
   ]
}

Restricting access to Amazon S3 buckets within a specific AWS account

If you want to ensure that your Amazon S3 principals are accessing only the resources that are inside of a trusted AWS account, you can restrict access. For example, this identity-based IAM policy uses a Deny effect to block access to Amazon S3 actions, unless the Amazon S3 resource that's being accessed is in account 222222222222. To prevent an IAM principal in an AWS account from accessing Amazon S3 objects outside of the account, attach the following IAM policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "DenyS3AccessOutsideMyBoundary",
      "Effect": "Deny",
      "Action": [
        "s3:*"
      ],
      "Resource": "*",
      "Condition": {
        "StringNotEquals": {
          "aws:ResourceAccount": [
            "222222222222"
          ]
        }
      }
    }
  ]
}

Make sure to replace account ID 222222222222 in the policy with your own AWS account. To apply a policy to multiple accounts while still maintaining this restriction, replace the account ID with the aws:PrincipalAccount condition key. This condition requires that the principal and the resource must be in the same account.

Restricting access to Amazon S3 buckets within your organizational unit

If you have an organizational unit (OU) set up in AWS Organizations, you might want to restrict Amazon S3 bucket access to a specific part of your organization. In this example, we'll use the aws:ResourceOrgPaths key to restrict Amazon S3 bucket access to an OU in your organization. For this example, the OU ID is ou-acroot-exampleou. Make sure to replace this value in your own policy with your own OU IDs.

{
   "Version": "2012-10-17",
   "Statement": [
     {
       "Sid": "AllowS3AccessOutsideMyBoundary",
       "Effect": "Allow",
       "Action": [
         "s3:*"
       ],
       "Resource": "*",
       "Condition": {
         "ForAllValues:StringNotLike": {
           "aws:ResourceOrgPaths": [
             "o-acorg/r-acroot/ou-acroot-exampleou/"
           ] 
         }
       }
     }
   ]
 }

The policy denies access to Amazon S3 actions unless the Amazon S3 object that's being accessed is in the ou-acroot-exampleou OU in your organization. The IAM policy condition requires aws:ResourceOrgPaths, a multivalued condition key, to contain any of the listed OU paths. The policy uses the ForAllValues:StringNotLike operator to compare the values of aws:ResourceOrgPaths to the listed OUs without case-sensitive matching.

Restricting access to Amazon S3 buckets within your organization

To restrict access to Amazon S3 objects within your organization, attach an IAM policy to the root of the organization, applying it to all accounts in your organization. To require your IAM principals to follow this rule, use a service-control policy (SCP). If you choose to use an SCP, make sure to thoroughly test the SCP before attaching the policy to the root of the organization.

In the following example policy, access is denied to Amazon S3 actions unless the Amazon S3 object that's being accessed is in the same organization as the IAM principal that is accessing it:

{
   "Version": "2012-10-17",
   "Statement": [
     {
       "Sid": "DenyS3AccessOutsideMyBoundary",
       "Effect": "Deny",
       "Action": [
         "s3:*"
       ],
       "Resource": "arn:aws:s3:::*/*",
       "Condition": {
         "StringNotEquals": {
           "aws:ResourceOrgID": "${aws:PrincipalOrgID}"
         }
       }
     }
   ]
 }

The IAM policy condition in this example requires aws:ResourceOrgID and aws:PrincipalOrgID to be equal to each other. With this requirement, the principal making the request and the resource being accessed must be in the same organization.

Granting permission to retrieve the PublicAccessBlock configuration for an AWS account

The following example identity-based policy grants the s3:GetAccountPublicAccessBlock permission to a user. For these permissions, you set the Resource value to "*". For information about resource ARNs, see Policy resources for Amazon S3.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Sid":"statement1",
         "Effect":"Allow",
         "Action":[
            "s3:GetAccountPublicAccessBlock" 
         ],
         "Resource":[
            "*"
         ]
       }
    ]
}

Restricting bucket creation to one Region

Suppose that an AWS account administrator wants to grant its user (Dave) permission to create a bucket in the South America (São Paulo) Region only. The account administrator can attach the following user policy granting the s3:CreateBucket permission with a condition as shown. The key-value pair in the Condition block specifies the s3:LocationConstraint key and the sa-east-1 Region as its value.

For a list of Amazon S3 Regions, see Regions and Endpoints in the AWS General Reference.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Sid":"statement1",
         "Effect":"Allow",
         "Action": "s3:CreateBucket",
         "Resource": "arn:aws:s3:::*",
         "Condition": {
             "StringLike": {
                 "s3:LocationConstraint": "sa-east-1"
             }
         }
       }
    ]
}

Add explicit deny

The preceding policy restricts the user from creating a bucket in any other Region except sa-east-1. However, some other policy might grant this user permission to create buckets in another Region. For example, if the user belongs to a group, the group might have a policy attached to it that allows all users in the group permission to create buckets in another Region. To ensure that the user doesn't get permission to create buckets in any other Region, you can add an explicit deny statement in the above policy.

The Deny statement uses the StringNotLike condition. That is, a create bucket request is denied if the location constraint is not sa-east-1. The explicit deny doesn't allow the user to create a bucket in any other Region, no matter what other permission the user gets. The following policy includes an explicit deny statement.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Sid":"statement1",
         "Effect":"Allow",
         "Action": "s3:CreateBucket",
         "Resource": "arn:aws:s3:::*",
         "Condition": {
             "StringLike": {
                 "s3:LocationConstraint": "sa-east-1"
             }
         }
       },
      {
         "Sid":"statement2",
         "Effect":"Deny",
         "Action": "s3:CreateBucket",
         "Resource": "arn:aws:s3:::*",
         "Condition": {
             "StringNotLike": {
                 "s3:LocationConstraint": "sa-east-1"
             }
         }
       }
    ]
}

Test the policy with the AWS CLI

You can test the policy using the following create-bucket AWS CLI command. This example uses the bucketconfig.txt file to specify the location constraint. Note the Windows file path. You need to update the bucket name and path as appropriate. You must provide user credentials using the --profile parameter. For more information about setting up and using the AWS CLI, see Developing with Amazon S3 using the AWS CLI in the Amazon S3 API Reference.

aws s3api create-bucket --bucket examplebucket --profile AccountADave --create-bucket-configuration file://c:/Users/someUser/bucketconfig.txt

The bucketconfig.txt file specifies the configuration as follows.

{"LocationConstraint": "sa-east-1"}