MeshPassthrough
This policy uses new policy matching algorithm.
This policy enables Kuma to configure traffic to external destinations that is allowed to pass outside the mesh. When using this policy, the passthrough mode flag is ignored.
TargetRef support matrix
targetRef |
Allowed kinds |
---|---|
targetRef.kind |
Mesh , MeshSubset |
To learn more about the information in this table, see the matching docs.
Configuration
This policy doesn’t work with sidecars without transparent-proxy.
The following describes the default configuration settings of the MeshPassthrough
policy:
passthroughMode
: (Optional) Defines behaviour for handling traffic. Allowed values:All
,None
andMatched
. Default:None
All
enables all traffic to pass through.Matched
allows only the traffic defined inappendMatch
.None
disallows all traffic.
appendMatch
: List of destinations that are allowed to pass through. WhenpassthroughMode
isAll
orNone
this list is not used. It only takes effect whenpassthroughMode
isMatched
.type
: Defines what type of destination is allowed. EitherDomain
,IP
orCIDR
.value
: Destination address based on the definedtype
.port
: Port at which external destination is available. When not defined it caches all traffic to the address.protocol
: Defines protocol of the external destination.tcp
: Can’t be used whentype
isDomain
(at TCP level we are not able to distinguish domain, in this case it is going to hijack whole traffic on this port).tls
: Should be used when TLS traffic is originated by the client application.http
http2
grpc
Wildcard DNS matching
MeshPassthrough
policy allows you to create a match for a wildcard subdomain.
Currently, support for partial subdomain matching is not implemented. For example, a match for *w.example.com
will be rejected.
apiVersion: kuma.io/v1alpha1
kind: MeshPassthrough
metadata:
name: wildcard-passthrough
namespace: kuma-system
labels:
kuma.io/mesh: default
spec:
targetRef:
kind: Mesh
proxyTypes:
- Sidecar
default:
passthroughMode: Matched
appendMatch:
- type: Domain
value: "*.cluster-1.kafka.aws.us-east-2.com"
protocol: tls
port: 443
Security
It is advised that the Mesh Operator is responsible for managing the MeshPassthrough
policy.
This policy can introduce traffic outside of the mesh or even the cluster, and the Mesh Operator should be aware of this.
If you want to restrict access to MeshPassthrough
to specific services, you must choose them manually.
If you rely on tags in the top-level targetRef
you might consider securing them by using one of the following techniques:
- Make sure that service owners can’t freely modify them (using something like
kyverno
,OPA
or similar) - Accept the risk of being able to “impersonate” a passthrough label and rely on auditing to figure out any violations.
Limitations
- Due to the nature of some traffic, it is not possible to combine certain protocols on the same port. You can create a
MeshPassthrough
policy that handlestcp
,tls
, and one ofhttp
,http2
, orgrpc
traffic on the same port. Layer 7 protocols cannot be distinguished, which could introduce unexpected behavior. - It is currently not possible to route passthrough traffic through the zone egress. However, this feature will be implemented in the future.
- Gateways are currently not supported.
Examples
Disable passthrough for all sidecars
apiVersion: kuma.io/v1alpha1
kind: MeshPassthrough
metadata:
name: disable-passthrough
namespace: kuma-system
labels:
kuma.io/mesh: default
spec:
targetRef:
kind: Mesh
proxyTypes:
- Sidecar
default:
passthroughMode: None
Enable passthrough for a subset of sidecars
apiVersion: kuma.io/v1alpha1
kind: MeshPassthrough
metadata:
name: enable-passthrough
namespace: kuma-system
labels:
kuma.io/mesh: default
spec:
targetRef:
kind: MeshSubset
proxyTypes:
- Sidecar
tags:
kuma.io/service: demo-app_kuma-demo_svc_5000
default:
passthroughMode: All
Allow a subset of services to communicate with specific external endpoints
apiVersion: kuma.io/v1alpha1
kind: MeshPassthrough
metadata:
name: allow-some-passthrough
namespace: kuma-system
labels:
kuma.io/mesh: default
spec:
targetRef:
kind: MeshSubset
proxyTypes:
- Sidecar
tags:
kuma.io/service: demo-app_kuma-demo_svc_5000
default:
passthroughMode: Matched
appendMatch:
- type: Domain
value: httpbin.org
protocol: tls
port: 443
- type: IP
value: 10.240.15.39
protocol: tcp
port: 8888
- type: CIDR
value: 10.250.0.0/16
protocol: tcp
port: 10000
- type: Domain
value: "*.wikipedia.org"
protocol: tls
port: 443
- type: Domain
value: httpbin.dev
protocol: http
port: 80