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Antrea supports standard K8s NetworkPolicies to secure traffic between Pods. These NetworkPolicies are written from an application developer's perspective, hence they lack the ability to gain a finer-grained control over the security policies that a cluster administrator would require. This document describes a few new CRDs supported by Antrea to provide the administrator with more control over security within the cluster, and which are meant to co-exist with and complement the K8s NetworkPolicy.
Antrea supports grouping Antrea Policy CRDs together in a tiered fashion
to provide a hierarchy of security policies. This is achieved by setting the
tier field when defining an Antrea Policy CRD (e.g. a ClusterNetworkPolicy
object) to the appropriate tier name. Each tier has a priority associated with
it, which determines its relative order among all tiers.
Note: K8s NetworkPolicies will be enforced once all tiers have been enforced.
Creating Tiers as CRDs allows users the flexibility to create and delete Tiers as per their preference i.e. not be bound to 5 static tiering options as was the case initially.
An example Tier might look like this:
apiVersion: security.antrea.tanzu.vmware.com/v1alpha1 kind: Tier metadata: name: mytier spec: priority: 10 description: "my custom tier"
Tiers have the following characteristics:
tierfield in a Antrea NetworkPolicy CRD spec to the Tier's name.
priorityvalue) Tiers are enforced first.
priorityfield is unsupported.
Antrea release 0.9.x introduced support for 5 static tiers. These static tiers have been removed in favor of Tier CRDs as mentioned in the previous section. On startup, antrea-controller will create 5 Read-Only Tier resources corresponding to the static tiers for default consumption as shown below.
Emergency -> Tier name "emergency" with priority "5" SecurityOps -> Tier name "securityops" with priority "50" NetworkOps -> Tier name "networkops" with priority "100" Platform -> Tier name "platform" with priority "150" Application -> Tier name "application" with priority "250"
Any Antrea policy CRD referencing a static tier in its spec will now internally reference the corresponding Tier resource, thus maintaining the order of enforcement.
Previously, the static tiers created were as follows in the relative order of precedence:
Emergency > SecurityOps > NetworkOps > Platform > Application
Thus, all Antrea Policy resources associated with "Emergency" tier will be
enforced before any other Antrea Policy resource associated with any other
tier, until a match occurs, in which case the policy rule's
action will be
applied. The "Application" tier carries the lowest precedence, and any Antrea
Policy resource without a
tier name set in its spec will be associated with
the "Application" tier. Even though the policies associated with the
"Application" tier carry the lowest precedence amongst all the tiers, they are
still enforced before K8s NetworkPolicies. Thus, admin-created tiered Antrea
Policy CRDs have a higher precedence than developer-created K8s
ClusterNetworkPolicy, one of the two Antrea Policy CRDs introduced, is a specification of how workloads within a cluster communicate with each other and other external endpoints. The ClusterNetworkPolicy is supposed to aid cluster admins to configure the security policy for the cluster, unlike K8s NetworkPolicy, which is aimed towards developers to secure their apps and affects Pods within the Namespace in which the K8s NetworkPolicy is created. Rules belonging to ClusterNetworkPolicies are enforced before any rule belonging to a K8s NetworkPolicy.
Note: ClusterNetworkPolicy is currently in "Alpha" stage. In order to
enable them, edit the Controller and Agent configuration in the
ConfigMap as follows:
antrea-controller.conf: | featureGates: # Enable AntreaPolicy feature to complement K8s NetworkPolicy # for cluster admins to define security policies which apply to the # entire cluster. AntreaPolicy: true
antrea-agent.conf: | featureGates: # Enable AntreaPolicy feature to complement K8s NetworkPolicy # for cluster admins to define security policies which apply to the # entire cluster. AntreaPolicy: true
An example ClusterNetworkPolicy might look like this:
apiVersion: security.antrea.tanzu.vmware.com/v1alpha1 kind: ClusterNetworkPolicy metadata: name: test-cnp spec: priority: 5 tier: securityops appliedTo: - podSelector: matchLabels: role: db - namespaceSelector: matchLabels: env: prod ingress: - action: Allow from: - podSelector: matchLabels: role: frontend - podSelector: matchLabels: role: nondb namespaceSelector: matchLabels: role: db ports: - protocol: TCP port: 8080 egress: - action: Drop to: - ipBlock: cidr: 10.0.10.0/24 ports: - protocol: TCP port: 5978
spec: The ClusterNetworkPolicy
spec has all the information needed to
define a cluster-wide security policy.
appliedTo field specifies the grouping criteria of Pods to
which the policy applies to. Pods can be selected cluster-wide using
podSelector. If set with a
namespaceSelector, all Pods from Namespaces
selected by the namespaceSelector will be selected. Specific Pods from
specific Namespaces can be selected by providing both a
podSelector and a
namespaceSelector in the same
IPBlock cannot be set in the
In the example, the policy applies to Pods, which either match the labels
"role=db" in all the Namespaces, or are from Namespaces which match the
priority field determines the relative priority of the
policy among all ClusterNetworkPolicies in the given cluster. This field is
mandatory. A lower priority value indicates higher precedence. Priority values
can range from 1.0 to 10000.0.
Note: Policies with the same priorities will be enforced
indeterministically. Users should therefore take care to use priorities to
ensure the behavior they expect.
tier field associates a CNP to an existing Tier. The
field can be set with the name of the Tier CRD to which this policy must be
associated with. If not set, the CNP is associated with the lowest priority
default tier i.e. the "application" Tier.
ingress: Each ClusterNetworkPolicy may consist of zero or more ordered
set of ingress rules. Each rule, depending on the
action field of the rule,
allows or drops traffic which matches both the
The example policy contains a single rule, which allows matched traffic on a
single port, from one of two sources: the first specified by a
and the second specified by a combination of a
podSelector and a
Note: The order in which the ingress rules are set matter, i.e. rules will
be enforced in the order in which they are written.
egress: Each ClusterNetworkPolicy may consist of zero or more ordered set
of egress rules. Each rule, depending on the
action field of the rule, allows
or drops traffic which matches both the
ports sections. The example
policy contains a single rule, which drops matched traffic on a single port,
to the 10.0.10.0/24 subnet specified by the
Note: The order in which the egress rules are set matter, i.e. rules will
be enforced in the order in which they are written.
There are four kinds of selectors that can be specified in an ingress
section or egress
podSelector: This selects particular Pods from all Namespaces as "sources",
if set in
ingress section, or as "destinations", if set in
namespaceSelector: This selects particular Namespaces for which all Pods
are grouped as
ingress "sources" or
podSelector and namespaceSelector: A single to/from entry that specifies both namespaceSelector and podSelector selects particular Pods within particular Namespaces.
ipBlock: This selects particular IP CIDR ranges to allow as
egress "destinations". These should be cluster-external IPs,
since Pod IPs are ephemeral and unpredictable.
namespaceSelectorselects Pods from all Namespaces.
actionfield which specifies whether the matched rule allows or drops the traffic.
exceptfield. A higher priority rule can be written to deny the specific CIDR range to simulate the behavior of IPBlock field with
Antrea NetworkPolicy is another Policy CRD, which is similar to the ClusterNetworkPolicy CRD, however its scope is limited to a Namespace. The purpose of introducing this CRD is to allow admins to take advantage of advanced NetworkPolicy features and apply them within a Namespace to complement the K8s NetworkPolicies. Similar to the ClusterNetworkPolicy resource, Antrea NetworkPolicy can also be associated with Tiers.
Note: Antrea NetworkPolicy is currently in "Alpha" stage and is enabled
along with Tiers and ClusterNetworkPolicy as part of the
An example Antrea NetworkPolicy might look like this:
apiVersion: security.antrea.tanzu.vmware.com/v1alpha1 kind: NetworkPolicy metadata: name: test-anp namespace: default spec: priority: 5 tier: securityops appliedTo: - podSelector: matchLabels: role: db ingress: - action: Allow from: - podSelector: matchLabels: role: frontend - podSelector: matchLabels: role: nondb namespaceSelector: matchLabels: role: db ports: - protocol: TCP port: 8080 egress: - action: Drop to: - ipBlock: cidr: 10.0.10.0/24 ports: - protocol: TCP port: 5978
Antrea NetworkPolicy shares it's spec with ClusterNetworkPolicy. However, the following documents some of the key differences between the two Antrea Policy CRDs.
appliedToin a ClusterNetworkPolicy, setting a
appliedTofield is forbidden.
namespaceSelector, set within a NetworkPolicy Peer of any rule, selects Pods from the Namespace in which the Antrea NetworkPolicy is created. This behavior is similar to the K8s NetworkPolicy.
Antrea Policy CRDs are ordered based on priorities set at various levels.
With the introduction of tiers, Antrea Policies, like ClusterNetworkPolicies, are first enforced based on the Tier to which they are associated. i.e. all policies belonging to a high Tier are enforced first, followed by policies belonging to the next Tier and so on, until the "application" Tier policies are enforced.
Within a tier, Antrea Policy CRDs are ordered by the
priority at the policy
level. Thus, the policy with the highest precedence (lowest priority number
value) is enforced first. This ordering is performed solely based on the
priority assigned as opposed to the "Kind" of the resource, i.e. the relative
ordering between a ClusterNetworkPolicy resource and an Antrea NetworkPolicy
resource within a Tier depends only on the
set in each of the two resources.
Within a policy, rules are enforced in the order in which they are set. For example, consider the following:
This translates to the following order: - Ingress rules: ir3.1 > ir3.2 > ir1.1 -> ir1.2 -> ir2.1 -> ir2.2 - Egress rules: er3.1 > er3.2 > er1.1 -> er1.2 -> er2.1 -> er2.2
Once a rule is matched, it is executed based on the action set. If none of the policy rules match, the packet is then enforced for rules created for K8s NP. Hence, Antrea Policy CRDs take precedence over K8s NP.
Antrea Policy CRDs are meant for admins to manage the security of their
cluster. Thus, access to manage these CRDs must be granted to subjects which
have the authority to outline the security policies for the cluster and/or
Namespaces. On cluster initialization, Antrea grants the permissions to edit
these CRDs with
admin and the
edit ClusterRole. In addition to this, Antrea
also grants the permission to view these CRDs with the
Cluster admins can therefore grant these ClusterRoles to any subject who may
be responsible to manage the Antrea Policy CRDs. The admins may also decide to
view ClusterRole to a wider range of subjects to allow them to read
the policies that may affect their workloads.