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205 lines
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205 lines
9.0 KiB
Markdown
---
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layout: "docs"
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page_title: "Connect in Production"
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sidebar_current: "docs-guides-connect-production"
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description: |-
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This guide describes best practices for running Consul Connect in production.
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---
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# Running Connect in Production
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Consul Connect can secure all inter-service communication via mutual TLS. It's
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designed to work with [minimal configuration out of the
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box](https://learn.hashicorp.com/consul/getting-started/connect), but completing the [security
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checklist](/docs/connect/security.html) and understanding the [Consul security
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model](/docs/internals/security.html) are prerequisites for production
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deployments.
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This guide aims to walk through the steps required to ensure the security
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guarantees hold.
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We assume a cluster is already running with an appropriate number of servers and
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clients and that other reference material like the
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[deployment](/docs/guides/deployment.html) and
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[performance](/docs/guides/performance.html) guides have been followed.
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In practical deployments it may be necessary to incrementally adopt Connect
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service-by-service. In this case some or all of the advice below may not apply
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during the transition but should give a good understanding on which security
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properties have been sacrificed in the interim. The final deployment goal should
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be to end up compliant with all the advice below.
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The steps we need to get to a secure Connect cluster are:
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1. [Configure ACLs](#configure-acls)
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1. [Configure Agent Transport Encryption](#configure-agent-transport-encryption)
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1. [Bootstrap Certificate Authority](#bootstrap-certificate-authority)
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1. [Setup Host Firewall](#setup-host-firewall)
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1. [Configure Service Instances](#configure-service-instances)
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## Configure ACLs
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Consul Connect's security is based on service identity. In practice the identity
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of the service is only enforcible with sufficiently restrictive ACLs.
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This section will not replace reading the full [ACL
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guide](/docs/guides/acl.html) but will highlight the specific requirements
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Connect relies on to ensure it's security properties.
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A service's identity, in the form of an x.509 certificate, will only be issued
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to an API client that has `service:write` permission for that service. In other
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words, any client that has permission to _register_ an instance of a service
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will be able to identify as that service and access all of the resources that that
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service is allowed to access.
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A secure ACL setup must meet these criteria:
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1. **[ACL default
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policy](/docs/agent/options.html#acl_default_policy)
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must be `deny`.** It is technically sufficient to keep the default policy of
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`allow` but add an explicit ACL denying anonymous `service:write`. Note
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however that in this case the Connect intention graph will also default to
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`allow` and explicit `deny` intentions will be needed to restrict service
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access. Also note that explicit rules to limit who can manage intentions are
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necessary in this case. It is assumed for the remainder of this guide that
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ACL policy defaults to `deny`.
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2. **Each service must have a distinct ACL token** that is restricted to
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`service:write` only for the named service. Current Consul ACLs only support
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prefix matching but in a near-future release we will allow exact name
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matching. It is possible for all instances of the service to share the same
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token although best practices is for each instance to get a unique token as
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described below.
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### Fine Grained Enforcement
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Connect intentions manage access based only on service identity so it is
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sufficient for ACL tokens to only be unique per _service_ and shared between
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instances.
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It is much better though if ACL tokens are unique per service _instance_ because
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it limits the blast radius of a compromise.
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A future release of Connect will support revoking specific certificates that
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have been issued. For example if a single node in a datacenter has been
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compromised, it will be possible to find all certificates issued to the agent on
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that node and revoke them. This will block all access to the intruder without
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taking instances of the service(s) on other nodes offline too.
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While this will work with service-unique tokens, there is nothing stopping an
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attacker from obtaining certificates while spoofing the agent ID or other
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identifier – these certificates will not appear to have been issued to the
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compromised agent and so will not be revoked.
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If every service instance has a unique token however, it will be possible to
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revoke all certificates that were requested under that token. Assuming the
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attacker can only access the tokens present on the compromised host, this
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guarantees that any certificate they might have access to or requested directly
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will be revoked.
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In practice, managing per-instance tokens requires automated ACL provisioning,
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for example using [HashiCorp's
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Vault](https://www.vaultproject.io/docs/secrets/consul/index.html).
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## Configure Agent Transport Encryption
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Consul's gossip (UDP) and RPC (TCP) communications need to be encrypted
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otherwise attackers may be able to see ACL tokens while in flight
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between the server and client agents (RPC) or between client agent and
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application (HTTP). Certificate private keys never leave the host they
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are used on but are delivered to the application or proxy over local
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HTTP so local agent traffic should be encrypted where potentially
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untrusted parties might be able to observe localhost agent API traffic.
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Follow the [encryption documentation](/docs/agent/encryption.html) to ensure
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both gossip encryption and RPC/HTTP TLS are configured securely.
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For now client and server TLS certificates are still managed by manual
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configuration. In the future we plan to automate more of that with the same
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mechanisms Connect offers to user applications.
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## Bootstrap Certificate Authority
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Consul Connect comes with a built in Certificate Authority (CA) that will
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bootstrap by default when you first enable Connect on your servers.
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To use the built-in CA, enable it in the server's configuration.
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```text
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connect {
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enabled = true
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}
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```
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This config change requires a restart which you can perform one server at a time
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to maintain availability in an existing cluster.
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As soon as a server that has Connect enabled becomes the leader, it will
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bootstrap a new CA and generate it's own private key which is written to the
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Raft state.
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Alternatively, an external private key can be provided via the [CA
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configuration](/docs/connect/ca.html#specifying-a-private-key-and-root-certificate).
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### External CAs
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Connect has been designed with a pluggable CA component so external CAs can be
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integrated. We will expand the external CA systems that are supported in the
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future and will allow seamless online migration to a different CA or
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bootstrapping with an external CA.
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For production workloads we recommend using [Vault or another external
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CA](/docs/connect/ca.html#external-ca-certificate-authority-providers) once
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available such that the root key is not stored within Consul state at all.
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## Setup Host Firewall
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In order to enable inbound connections to connect proxies, you may need to
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configure host or network firewalls to allow incoming connections to proxy
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ports.
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In addition to Consul agent's [communication
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ports](/docs/agent/options.html#ports) any
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[proxies](/docs/connect/proxies.html) will need to have
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ports open to accept incoming connections.
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If using [sidecar service
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registration](/docs/connect/proxies/sidecar-service.html) Consul will by default
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assign ports from [a configurable
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range](/docs/agent/options.html#sidecar_min_port) the default range is 21000 -
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21255. If this feature is used, the agent assumes all ports in that range are
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both free to use (no other processes listening on them) and are exposed in the
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firewall to accept connections from other service hosts.
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It is possible to prevent automated port selection by [configuring
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`sidecar_min_port` and
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`sidecar_max_port`](/docs/agent/options.html#sidecar_min_port) to both be `0`,
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forcing any sidecar service registrations to need an explicit port configured.
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It then becomes the same problem as opening ports necessary for any other
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application and might be managed by configuration management or a scheduler.
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## Configure Service Instances
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With [necessary ACL tokens](#configure-acls) in place, all service registrations
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need to have an appropriate ACL token present.
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For on-disk configuration the `token` parameter of the service definition must
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be set.
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For registration via the API [the token is passed in the request
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header](/api/index.html#acls) or by using the [Go
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client configuration](https://godoc.org/github.com/hashicorp/consul/api#Config).
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For examples of proxy service definitions see the [proxy
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documentation](/docs/connect/proxies.html).
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To avoid the overhead of a proxy, applications may [natively
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integrate](/docs/connect/native.html) with connect.
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### Protect Application Listener
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If using any kind of proxy for connect, the application must ensure no untrusted
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connections can be made to it's unprotected listening port. This is typically
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done by binding to `localhost` and only allowing loopback traffic, but may also
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be achieved using firewall rules or network namespacing.
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