81 lines
5.0 KiB
Markdown
81 lines
5.0 KiB
Markdown
# Containerized Squid on Container Optimized OS
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This module manages a `cloud-config` configuration that starts a containerized [Squid](http://www.squid-cache.org/) proxy on Container Optimized OS. The default configuration creates a filtering proxy that only allows connection to a whitelisted set of domains.
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The resulting `cloud-config` can be customized in a number of ways:
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- a custom squid.conf configuration can be set using the `squid_config` variable
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- additional files (e.g. additional acls) can be passed in via the `files` variable
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- a completely custom `cloud-config` can be passed in via the `cloud_config` variable, and additional template variables can be passed in via `config_variables`
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The default instance configuration inserts iptables rules to allow traffic on TCP port 3128. With the default `squid.conf`, deny rules take precedence over allow rules.
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Logging and monitoring are enabled via the [Google Cloud Logging driver](https://docs.docker.com/config/containers/logging/gcplogs/) configured for the Squid container, and the [Node Problem Detector](https://cloud.google.com/container-optimized-os/docs/how-to/monitoring) service started by default on boot.
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The module renders the generated cloud config in the `cloud_config` output, to be used in instances or instance templates via the `user-data` metadata.
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For convenience during development or for simple use cases, the module can optionally manage a single instance via the `test_instance` variable. If the instance is not needed the `instance*tf` files can be safely removed. Refer to the [top-level README](../README.md) for more details on the included instance.
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## Examples
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### Default Squid configuration
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This example will create a `cloud-config` that allows any client in the 10.0.0.0/8 CIDR to use the proxy to connect github.com or any subdomain of github.com.
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```hcl
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module "cos-squid" {
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source = "./modules/cloud-config-container/squid"
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whitelist = [".github.com"]
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clients = ["10.0.0.0/8"]
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}
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# use it as metadata in a compute instance or template
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resource "google_compute_instance" "default" {
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metadata = {
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user-data = module.cos-squid.cloud_config
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}
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```
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### Test Squid instance
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This example shows how to create the single instance optionally managed by the module, providing all required attributes in the `test_instance` variable. The instance is purposefully kept simple and should only be used in development, or when designing infrastructures.
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```hcl
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module "cos-squid" {
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source = "./modules/cloud-config-container/squid"
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whitelist = ["github.com"]
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clients = ["10.0.0.0/8"]
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test_instance = {
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project_id = "my-project"
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zone = "europe-west1-b"
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name = "cos-squid"
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type = "f1-micro"
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network = "default"
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subnetwork = "https://www.googleapis.com/compute/v1/projects/my-project/regions/europe-west1/subnetworks/my-subnet"
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}
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}
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```
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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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| [allow](variables.tf#L57) | List of domains Squid will allow connections to. | <code>list(string)</code> | | <code>[]</code> |
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| [clients](variables.tf#L69) | List of CIDR ranges from which Squid will allow connections. | <code>list(string)</code> | | <code>[]</code> |
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| [cloud_config](variables.tf#L17) | Cloud config template path. If null default will be used. | <code>string</code> | | <code>null</code> |
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| [config_variables](variables.tf#L23) | Additional variables used to render the cloud-config and Squid templates. | <code>map(any)</code> | | <code>{}</code> |
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| [default_action](variables.tf#L75) | Default action for domains not matching neither the allow or deny lists | <code>string</code> | | <code>"deny"</code> |
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| [deny](variables.tf#L63) | List of domains Squid will deny connections to. | <code>list(string)</code> | | <code>[]</code> |
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| [file_defaults](variables.tf#L35) | Default owner and permissions for files. | <code title="object({ owner = string permissions = string })">object({…})</code> | | <code title="{ owner = "root" permissions = "0644" }">{…}</code> |
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| [files](variables.tf#L47) | Map of extra files to create on the instance, path as key. Owner and permissions will use defaults if null. | <code title="map(object({ content = string owner = string permissions = string }))">map(object({…}))</code> | | <code>{}</code> |
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| [squid_config](variables.tf#L29) | Squid configuration path, if null default will be used. | <code>string</code> | | <code>null</code> |
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## Outputs
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| name | description | sensitive |
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|---|---|:---:|
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| [cloud_config](outputs.tf#L17) | Rendered cloud-config file to be passed as user-data instance metadata. | |
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<!-- END TFDOC -->
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