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99 lines
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99 lines
4.2 KiB
Text
---
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title: About the aws_s3_bucket_object Resource
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---
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# aws\_s3\_bucket\_object
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Use the `aws_s3_bucket_object` InSpec audit resource to test properties of a single AWS bucket object.
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Each S3 Object has a 'key' which can be thought of as the name of the S3 Object which uniquely identifies it.
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<br>
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## Limitations
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S3 object security is a complex matter. For details on how AWS evaluates requests for access, please see [the AWS documentation](https://docs.aws.amazon.com/AmazonS3/latest/dev/how-s3-evaluates-access-control.html). S3 buckets and the objects they contain support three different types of access control: bucket ACLs, bucket policies, and object ACLs.
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As of January 2018, this resource supports evaluating S3 Object ACLs. In particular, users of the `be_public` matcher should carefully examine the conditions under which the matcher will detect an insecure bucket. See the `be_public` section under the Matchers section below.
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## Availability
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### Installation
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This resource is distributed along with InSpec itself. You can use it automatically.
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### Version
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This resource first became available in v2.1.10 of InSpec.
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## Syntax
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An `aws_s3_bucket_object` resource block declares a bucket and an object key by name, and then lists tests to be performed.
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describe aws_s3_bucket_object(bucket_name: 'test_bucket', key: 'test_object_key') do
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it { should exist }
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it { should_not be_public }
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end
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<br>
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## Examples
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The following examples show how to use this InSpec audit resource.
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### Test a object's object-level ACL
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describe aws_s3_bucket_object(bucket_name: 'test_bucket', key: 'test_key') do
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its('object_acl.count') { should eq 1 }
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end
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### Check to see if a object appears to be exposed to the public
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# See Limitations section above
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describe aws_s3_bucket_object(bucket_name: 'test_bucket', key: 'test_key') do
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it { should_not be_public }
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end
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<br>
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## Unsupported Properties
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### object\_acl
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The `object_acl` property is a low-level property that lists the individual Object ACL grants that are in effect on the object. Other higher-level properties, such as be\_public, are more concise and easier to use. You can use the `object_acl` property to investigate which grants are in effect, causing be\_public to fail.
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The value of object_acl is an Array of simple objects. Each object has a `permission` property and a `grantee` property. The `permission` property will be a string such as 'READ', 'WRITE' etc (See the [AWS documentation](https://docs.aws.amazon.com/sdkforruby/api/Aws/S3/Client.html#get_bucket_acl-instance_method) for a full list). The `grantee` property contains sub-properties, such as `type` and `uri`.
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object_acl = aws_s3_bucket_object(bucket_name: 'my_bucket', key: 'object_key')
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# Look for grants to "AllUsers" (that is, the public)
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all_users_grants = object_acl.select do |g|
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g.grantee.type == 'Group' && g.grantee.uri =~ /AllUsers/
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end
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# Look for grants to "AuthenticatedUsers" (that is, any authenticated AWS user - nearly public)
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auth_grants = object_acl.select do |g|
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g.grantee.type == 'Group' && g.grantee.uri =~ /AuthenticatedUsers/
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end
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## Matchers
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This InSpec audit resource has the following special matchers. For a full list of available matchers (such as `exist`) please visit our [matchers page](https://www.inspec.io/docs/reference/matchers/).
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### be\_public
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The `be_public` matcher tests if the object has potentially insecure access controls. This high-level matcher detects several insecure conditions, which may be enhanced in the future. Currently, the matcher reports an insecure object if any of the following conditions are met:
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1. A object ACL grant exists for the 'AllUsers' group
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2. A object ACL grant exists for the 'AuthenticatedUsers' group
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Note: This resource does not detect insecure bucket ACLs.
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it { should_not be_public }
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## AWS Permissions
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Your [Principal](https://docs.aws.amazon.com/IAM/latest/UserGuide/intro-structure.html#intro-structure-principal) will need the `s3:GetObject`, and `s3:GetObjectAcl` actions set to allow.
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You can find detailed documentation at [Actions, Resources, and Condition Keys for Amazon S3](https://docs.aws.amazon.com/IAM/latest/UserGuide/list_amazons3.html).
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