63 lines
3.6 KiB
Markdown
63 lines
3.6 KiB
Markdown
# Network filtering with Squid
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This blueprint shows how to deploy a filtering HTTP proxy to restrict Internet access. Here we show one way to do this using a VPC with two subnets:
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- The `apps` subnet hosts the VMs that will have their Internet access tightly controlled by a non-caching filtering forward proxy.
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- The `proxy` subnet hosts a Cloud NAT instance and a [Squid](http://www.squid-cache.org/) server.
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The VPC is a Shared VPC and all the service projects will be located under a folder enforcing the `compute.vmExternalIpAccess` [organization policy](https://cloud.google.com/resource-manager/docs/organization-policy/org-policy-constraints). This prevents the service projects from having external IPs, thus forcing all outbound Internet connections through the proxy.
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To allow Internet connectivity to the proxy subnet, a Cloud NAT instance is configured to allow usage from [that subnet only](https://cloud.google.com/nat/docs/set-up-manage-network-address-translation#specify_subnet_ranges_for_nat). All other subnets are not allowed to use the Cloud NAT instance.
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To simplify the usage of the proxy, a Cloud DNS private zone is created and the IP address of the proxy is exposed with the FQDN `proxy.internal`.
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You can optionally deploy the Squid server as [Managed Instance Group](https://cloud.google.com/compute/docs/instance-groups) by setting the `mig` option to `true`. This option defaults to `false` which results in a standalone VM.
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<!-- BEGIN TFDOC -->
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## Variables
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| name | description | type | required | default |
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|---|---|:---:|:---:|:---:|
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| [billing_account](variables.tf#L26) | Billing account id used as default for new projects. | <code>string</code> | ✓ | |
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| [prefix](variables.tf#L52) | Prefix used for resource names. | <code>string</code> | ✓ | |
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| [root_node](variables.tf#L67) | Root node for the new hierarchy, either 'organizations/org_id' or 'folders/folder_id'. | <code>string</code> | ✓ | |
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| [allowed_domains](variables.tf#L17) | List of domains allowed by the squid proxy. | <code>list(string)</code> | | <code title="[ ".google.com", ".github.com" ]">[…]</code> |
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| [cidrs](variables.tf#L31) | CIDR ranges for subnets. | <code>map(string)</code> | | <code title="{ apps = "10.0.0.0/24" proxy = "10.0.1.0/28" }">{…}</code> |
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| [mig](variables.tf#L40) | Enables the creation of an autoscaling managed instance group of squid instances. | <code>bool</code> | | <code>false</code> |
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| [nat_logging](variables.tf#L46) | Enables Cloud NAT logging if not null, value is one of 'ERRORS_ONLY', 'TRANSLATIONS_ONLY', 'ALL'. | <code>string</code> | | <code>"ERRORS_ONLY"</code> |
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| [region](variables.tf#L61) | Default region for resources. | <code>string</code> | | <code>"europe-west1"</code> |
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## Outputs
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| name | description | sensitive |
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|---|---|:---:|
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| [squid-address](outputs.tf#L17) | IP address of the Squid proxy. | |
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<!-- END TFDOC -->
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## Test
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```hcl
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module "test1" {
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source = "./fabric/blueprints/networking/filtering-proxy"
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billing_account = "123456-123456-123456"
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mig = true
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prefix = "fabric"
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root_node = "folders/123456789"
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}
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# tftest modules=14 resources=38
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```
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```hcl
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module "test2" {
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source = "./fabric/blueprints/networking/filtering-proxy"
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billing_account = "123456-123456-123456"
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mig = false
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prefix = "fabric"
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root_node = "folders/123456789"
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}
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# tftest modules=12 resources=32
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```
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