Bucket policy examples using condition keys

You can use access policy language to specify conditions when you grant permissions. You can use the optional Condition element, or Condition block to specify conditions for when a policy is in effect.

For policies that use Amazon S3 condition keys for object and bucket operations, see the following examples. For more information about condition keys, see Policy condition keys for Amazon S3. For a complete list of Amazon S3 actions, condition keys, and resources that you can specify in policies, see Actions, resources, and condition keys for Amazon S3 in the Service Authorization Reference.

Examples — Amazon S3 condition keys for object operations

This section provides examples that show you how you can use Amazon S3‐specific condition keys for object operations. For a complete list of Amazon S3 actions, condition keys, and resources that you can specify in policies, see Actions, resources, and condition keys for Amazon S3 in the Service Authorization Reference.

Several of the example policies show how you can use conditions keys with PUT Object operations. PUT Object operations allow access control list (ACL)–specific headers that you can use to grant ACL-based permissions. Using these keys, the bucket owner can set a condition to require specific access permissions when the user uploads an object. You can also grant ACL–based permissions with the PutObjectAcl operation. For more information, see PutObjectAcl in the Amazon S3 Amazon Simple Storage Service API Reference. For more information about ACLs, see Access control list (ACL) overview.

Example 1: Granting s3:PutObject permission requiring objects stored using server-side encryption

Suppose that Account A owns a bucket. The account administrator wants to grant Jane, a user in Account A, permission to upload objects with a condition that Jane always request server-side encryption so that Amazon S3 saves objects encrypted. The Account A administrator can accomplish using the s3:x-amz-server-side-encryption condition key as shown. The key-value pair in the Condition block specifies the s3:x-amz-server-side-encryption key.

"Condition": {
     "StringNotEquals": {
         "s3:x-amz-server-side-encryption": "AES256"
     }}

When testing the permission using the AWS CLI, you must add the required parameter using the --server-side-encryption parameter.

aws s3api put-object --bucket example1bucket --key HappyFace.jpg --body c:\HappyFace.jpg --server-side-encryption "AES256" --profile AccountBadmin

Example 2: Granting s3:PutObject permission to copy objects with a restriction on the copy source

In the PUT Object request, when you specify a source object, it is a copy operation (see PUT Object - Copy). Accordingly, the bucket owner can grant a user permission to copy objects with restrictions on the source, for example:

The following bucket policy grants user (Dave) s3:PutObject permission. It allows him to copy objects only with a condition that the request include the s3:x-amz-copy-source header and the header value specify the /awsexamplebucket1/public/* key name prefix.

{
    "Version": "2012-10-17",
    "Statement": [
       {
            "Sid": "cross-account permission to user in your own account",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::123456789012:user/Dave"
            },
            "Action": "s3:PutObject",
            "Resource": "arn:aws:s3:::awsexamplebucket1/*"
        },
        {
            "Sid": "Deny your user permission to upload object if copy source is not /bucket/folder",
            "Effect": "Deny",
            "Principal": {
                "AWS": "arn:aws:iam::123456789012:user/Dave"
            },
            "Action": "s3:PutObject",
            "Resource": "arn:aws:s3:::awsexamplebucket1/*",
            "Condition": {
                "StringNotLike": {
                    "s3:x-amz-copy-source": "awsexamplebucket1/public/*"
                }
            }
        }
    ]
}

Test the policy with the AWS CLI

You can test the permission using the AWS CLI copy-object command. You specify the source by adding the --copy-source parameter; the key name prefix must match the prefix allowed in the policy. You need to provide the user Dave credentials using the --profile parameter. For more information about setting up the AWS CLI, see Developing with Amazon S3 using the AWS CLI.

aws s3api copy-object --bucket awsexamplebucket1 --key HappyFace.jpg 
--copy-source examplebucket/public/PublicHappyFace1.jpg --profile AccountADave

Give permission to copy only a specific object

The preceding policy uses the StringNotLike condition. To grant permission to copy only a specific object, you must change the condition from StringNotLike to StringNotEquals and then specify the exact object key as shown.

"Condition": {
       "StringNotEquals": {
           "s3:x-amz-copy-source": "awsexamplebucket1/public/PublicHappyFace1.jpg"
       }
}

Example 3: Granting access to a specific version of an object

Suppose that Account A owns a version-enabled bucket. The bucket has several versions of the HappyFace.jpg object. The account administrator now wants to grant its user Dave permission to get only a specific version of the object. The account administrator can accomplish this by granting Dave s3:GetObjectVersion permission conditionally as shown below. The key-value pair in the Condition block specifies the s3:VersionId condition key. In this case, Dave needs to know the exact object version ID to retrieve the object.

For more information, see GetObject in the Amazon Simple Storage Service API Reference.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "statement1",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::123456789012:user/Dave"
            },
            "Action": "s3:GetObjectVersion",
            "Resource": "arn:aws:s3:::examplebucketversionenabled/HappyFace.jpg"
        },
        {
            "Sid": "statement2",
            "Effect": "Deny",
            "Principal": {
                "AWS": "arn:aws:iam::123456789012:user/Dave"
            },
            "Action": "s3:GetObjectVersion",
            "Resource": "arn:aws:s3:::examplebucketversionenabled/HappyFace.jpg",
            "Condition": {
                "StringNotEquals": {
                    "s3:VersionId": "AaaHbAQitwiL_h47_44lRO2DDfLlBO5e"
                }
            }
        }
    ]
}

Test the policy with the AWS CLI

You can test the permissions using the AWS CLI get-object command with the --version-id parameter identifying the specific object version. The command retrieves the object and saves it to the OutputFile.jpg file.

aws s3api get-object --bucket examplebucketversionenabled --key HappyFace.jpg OutputFile.jpg --version-id AaaHbAQitwiL_h47_44lRO2DDfLlBO5e --profile AccountADave

Example 4: Granting permissions based on object tags

For examples on how to use object tagging condition keys with Amazon S3 operations, see Tagging and access control policies.

Example 5: Restricting access by the AWS account ID of the bucket owner

You can use either the aws:ResourceAccount or s3:ResourceAccount key to write IAM or virtual private cloud (VPC) endpoint policies that restrict user, role, or application access to the Amazon S3 buckets that are owned by a specific AWS account ID. You can use this condition key to restrict clients within your VPC from accessing buckets that you do not own.

However, be aware that some AWS services rely on access to AWS managed buckets. Therefore, using the aws:ResourceAccount or s3:ResourceAccount key in your IAM policy might also affect access to these resources.

For more information and examples, see the following resources:

Example 6: Requiring a minimum TLS version

You can use the s3:TlsVersion condition key to write IAM, Virtual Private Cloud Endpoint (VPCE), or bucket policies that restrict user or application access to Amazon S3 buckets based on the TLS version used by the client. You can use this condition key to write policies that require a minimum TLS version.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Deny",
            "Principal": "*",
            "Action": "s3:PutObject",
            "Resource": [
                "arn:aws:s3:::DOC-EXAMPLE-BUCKET1",
                "arn:aws:s3:::DOC-EXAMPLE-BUCKET1/*"
            ],
            "Condition": {
                "NumericLessThan": {
                    "s3:TlsVersion": 1.2
                }
            }
        }
    ]
}
					

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": "*",
            "Action": "s3:PutObject",
            "Resource": [
                "arn:aws:s3:::DOC-EXAMPLE-BUCKET1",
                "arn:aws:s3:::DOC-EXAMPLE-BUCKET1/*"
            ],
            "Condition": {
                "NumericGreaterThan": {
                    "s3:TlsVersion": 1.1
                }
            }
        }
    ]
}
					

Examples — Amazon S3 condition keys for bucket operations

This section provides example policies that show you how you can use Amazon S3‐specific condition keys for bucket operations.

Example 1: Granting s3:GetObject permission with a condition on an IP address

You can give authenticated users permission to use the s3:GetObject action if the request originates from a specific range of IP addresses (192.0.2.*), unless the IP address is 192.0.2.188. In the condition block, the IpAddress and the NotIpAddress are conditions, and each condition is provided a key-value pair for evaluation. Both the key-value pairs in this example use the aws:SourceIp AWS‐wide key.

{
    "Version": "2012-10-17",
    "Id": "S3PolicyId1",
    "Statement": [
        {
            "Sid": "statement1",
            "Effect": "Allow",
            "Principal": "*",
            "Action":"s3:GetObject",
            "Resource": "arn:aws:s3:::awsexamplebucket1/*",
            "Condition" : {
                "IpAddress" : {
                    "aws:SourceIp": "192.0.2.0/24" 
                },
                "NotIpAddress" : {
                    "aws:SourceIp": "192.0.2.188/32" 
                } 
            } 
        } 
    ]
} 

You can also use other AWS‐wide condition keys in Amazon S3 policies. For example, you can specify the aws:SourceVpce and aws:SourceVpc condition keys in bucket policies for VPC endpoints. For specific examples, see Controlling access from VPC endpoints with bucket policies.

Example 2: Getting a list of objects in a bucket with a specific prefix

You can use the s3:prefix condition key to limit the response of the GET Bucket (ListObjects) API to key names with a specific prefix. If you are the bucket owner, you can restrict a user to list the contents of a specific prefix in the bucket. This condition key is useful if objects in the bucket are organized by key name prefixes. The Amazon S3 console uses key name prefixes to show a folder concept. Only the console supports the concept of folders; the Amazon S3 API supports only buckets and objects. For more information about using prefixes and delimiters to filter access permissions, see Controlling access to a bucket with user policies.

For example, if you have two objects with key names public/object1.jpg and public/object2.jpg, the console shows the objects under the public folder. In the Amazon S3 API, these are objects with prefixes, not objects in folders. However, in the Amazon S3 API, if you organize your object keys using such prefixes, you can grant s3:ListBucket permission with the s3:prefix condition that will allow the user to get a list of key names with those specific prefixes.

In this example, the bucket owner and the parent account to which the user belongs are the same. So the bucket owner can use either a bucket policy or a user policy. For more information about other condition keys that you can use with the GET Bucket (ListObjects) API, see ListObjects.

User policy

The following user policy grants the s3:ListBucket permission (see GET Bucket (List Objects)) with a condition that requires the user to specify the prefix in the request with the value projects.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Sid":"statement1",
         "Effect":"Allow",
         "Action": "s3:ListBucket",
         "Resource":"arn:aws:s3:::awsexamplebucket1",
         "Condition" : {
             "StringEquals" : {
                 "s3:prefix": "projects" 
             }
          } 
       },
      {
         "Sid":"statement2",
         "Effect":"Deny",
         "Action": "s3:ListBucket",
         "Resource": "arn:aws:s3:::awsexamplebucket1",
         "Condition" : {
             "StringNotEquals" : {
                 "s3:prefix": "projects" 
             }
          } 
       }         
    ]
}

The condition restricts the user to listing object keys with the projects prefix. The added explicit deny denies the user request for listing keys with any other prefix no matter what other permissions the user might have. For example, it is possible that the user gets permission to list object keys without any restriction, either by updates to the preceding user policy or via a bucket policy. Because explicit deny always supersedes, the user request to list keys other than the projects prefix is denied.

Bucket policy

If you add the Principal element to the above user policy, identifying the user, you now have a bucket policy as shown.

{
   "Version":"2012-10-17",
   "Statement":[
      {
         "Sid":"statement1",
         "Effect":"Allow",
         "Principal": {
            "AWS": "arn:aws:iam::123456789012:user/bucket-owner"
         },  
         "Action":  "s3:ListBucket",
         "Resource": "arn:aws:s3:::awsexamplebucket1",
         "Condition" : {
             "StringEquals" : {
                 "s3:prefix": "projects" 
             }
          } 
       },
      {
         "Sid":"statement2",
         "Effect":"Deny",
         "Principal": {
            "AWS": "arn:aws:iam::123456789012:user/bucket-owner"
         },  
         "Action": "s3:ListBucket",
         "Resource": "arn:aws:s3:::awsexamplebucket1",
         "Condition" : {
             "StringNotEquals" : {
                 "s3:prefix": "projects"  
             }
          } 
       }         
    ]
}

Test the policy with the AWS CLI

You can test the policy using the following list-object AWS CLI command. In the command, you 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.

aws s3api list-objects --bucket awsexamplebucket1 --prefix examplefolder --profile AccountADave

If the bucket is version-enabled, to list the objects in the bucket, you must grant the s3:ListBucketVersions permission in the preceding policy, instead of s3:ListBucket permission. This permission also supports the s3:prefix condition key.

Example 3: Setting the maximum number of keys

You can use the s3:max-keys condition key to set the maximum number of keys that requester can return in a GET Bucket (ListObjects) or ListObjectVersions request. By default, the API returns up to 1,000 keys. For a list of numeric condition operators that you can use with s3:max-keys and accompanying examples, see Numeric Condition Operators in the IAM User Guide.