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129 lines
5.4 KiB
Markdown
129 lines
5.4 KiB
Markdown
---
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title: About the aws_s3_bucket Resource
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---
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# aws_s3_bucket
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Use the `aws_s3_bucket` InSpec audit resource to test properties of a single AWS bucket.
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To test properties of a multiple S3 buckets, use the `aws_s3_buckets` resource.
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<br>
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## Limitations
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S3 bucket 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 bucket ACLs and bucket policies. We do not support evaluating object ACLs because it introduces scalability concerns in the AWS API; we recommend using AWS mechanisms such as CloudTrail and Config to detect insecure object ACLs.
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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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## Syntax
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An `aws_s3_bucket` resource block declares a bucket by name, and then lists tests to be performed.
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describe aws_s3_bucket(bucket_name: 'test_bucket') 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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describe aws_s3_bucket('test_bucket') do
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it { should exist }
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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 bucket's bucket-level ACL
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describe aws_s3_bucket('test_bucket') do
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its('bucket_acl.count') { should eq 1 }
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end
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### Check to see if a bucket has a bucket policy
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describe aws_s3_bucket('test_bucket') do
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its('bucket_policy') { should be_empty }
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end
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### Check to see if a bucket appears to be exposed to the public
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# See Limitations section above
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describe aws_s3_bucket('test_bucket') do
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it { should_not be_public }
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end
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<br>
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## Supported Properties
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### region
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The `region` property identifies the AWS Region in which the S3 bucket is located.
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describe aws_s3_bucket('test_bucket') do
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# Check if the correct region is set
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its('region') { should eq 'us-east-1' }
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end
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## Unsupported Properties
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### bucket_acl
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The `bucket_acl` property is a low-level property that lists the individual Bucket ACL grants that are in effect on the bucket. Other higher-level properties, such as be\_public, are more concise and easier to use. You can use the `bucket_acl` property to investigate which grants are in effect, causing be\_public to fail.
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The value of bucket_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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bucket_acl = aws_s3_bucket('my-bucket')
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# Look for grants to "AllUsers" (that is, the public)
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all_users_grants = bucket_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 = bucket_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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### bucket_policy
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The `bucket_policy` is a low-level property that describes the IAM policy document controlling access to the bucket. The `bucket_policy` property returns a Ruby structure that you can probe to check for particular statements. We recommend using a higher-level property, such as `be_public`, which is concise and easier to implement in your policy files.
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The `bucket_policy` property returns an Array of simple objects, each object being an IAM Policy Statement. See the [AWS documentation](https://docs.aws.amazon.com/AmazonS3/latest/dev/example-bucket-policies.html#example-bucket-policies-use-case-2) for details about the structure of this data.
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If there is no bucket policy, this property will return an empty Array.
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bucket_policy = aws_s3_bucket('my-bucket')
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# Look for statements that allow the general public to do things
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# This may be a false positive; it's possible these statements
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# could be protected by conditions, such as IP restrictions.
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public_statements = bucket_policy.select do |s|
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s.effect == 'Allow' && s.principal == '*'
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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 bucket 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 bucket if any of the following conditions are met:
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1. A bucket ACL grant exists for the 'AllUsers' group
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2. A bucket ACL grant exists for the 'AuthenticatedUsers' group
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3. A bucket policy has an effect 'Allow' and principal '*'
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Note: This resource does not detect insecure object ACLs.
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it { should_not be_public }
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### have_access_logging_enabled
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The `have_access_logging_enabled` matcher tests if access logging is enabled for the s3 bucket.
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it { should have_access_logging_enabled }
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