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fd044ee117
* Enable bootstrap token authentication on kube-apiserver * Generate the bootstrap.kubernetes.io/token Secret that may be used as a bootstrap token * Generate a bootstrap kubeconfig (with a bootstrap token) to be securely distributed to nodes. Each Kubelet will use the bootstrap kubeconfig to authenticate to kube-apiserver as `system:bootstrappers` and send a node-unique CSR for kube-controller-manager to automatically approve to issue a Kubelet certificate and kubeconfig (expires in 72 hours) * Add ClusterRoleBinding for bootstrap token subjects (`system:bootstrappers`) to have the `system:node-bootstrapper` ClusterRole * Add ClusterRoleBinding for bootstrap token subjects (`system:bootstrappers`) to have the csr nodeclient ClusterRole * Add ClusterRoleBinding for bootstrap token subjects (`system:bootstrappers`) to have the csr selfnodeclient ClusterRole * Enable NodeRestriction admission controller to limit the scope of Node or Pod objects a Kubelet can modify to those of the node itself * Ability for a Kubelet to delete its Node object is retained as preemptible nodes or those in auto-scaling instance groups need to be able to remove themselves on shutdown. This need continues to have precedence over any risk of a node deleting itself maliciously Security notes: 1. Issued Kubelet certificates authenticate as user `system:node:NAME` and group `system:nodes` and are limited in their authorization to perform API operations by Node authorization and NodeRestriction admission. Previously, a Kubelet's authorization was broader. This is the primary security motivation. 2. The bootstrap kubeconfig credential has the same sensitivity as the previous generated TLS client-certificate kubeconfig. It must be distributed securely to nodes. Its compromise still allows an attacker to obtain a Kubelet kubeconfig 3. Bootstrapping Kubelet kubeconfig's with a limited lifetime offers a slight security improvement. * An attacker who obtains the kubeconfig can likely obtain the bootstrap kubeconfig as well, to obtain the ability to renew their access * A compromised bootstrap kubeconfig could plausibly be handled by replacing the bootstrap token Secret, distributing the token to new nodes, and expiration. Whereas a compromised TLS-client certificate kubeconfig can't be revoked (no CRL). However, replacing a bootstrap token can be impractical in real cluster environments, so the limited lifetime is mostly a theoretical benefit. * Cluster CSR objects are visible via kubectl which is nice 4. Bootstrapping node-unique Kubelet kubeconfigs means Kubelet clients have more identity information, which can improve the utility of audits and future features Rel: https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping/ Rel: https://github.com/poseidon/terraform-render-bootstrap/pull/185
24 lines
853 B
HCL
24 lines
853 B
HCL
# Kubernetes assets (kubeconfig, manifests)
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module "bootstrap" {
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source = "git::https://github.com/poseidon/terraform-render-bootstrap.git?ref=924beb4b0cb3ca076c29c85983070d0f66dddc5c"
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cluster_name = var.cluster_name
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api_servers = [format("%s.%s", var.cluster_name, var.dns_zone)]
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etcd_servers = formatlist("%s.%s", azurerm_dns_a_record.etcds.*.name, var.dns_zone)
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asset_dir = var.asset_dir
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networking = var.networking
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# only effective with Calico networking
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# we should be able to use 1450 MTU, but in practice, 1410 was needed
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network_encapsulation = "vxlan"
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network_mtu = "1410"
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pod_cidr = var.pod_cidr
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service_cidr = var.service_cidr
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cluster_domain_suffix = var.cluster_domain_suffix
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enable_reporting = var.enable_reporting
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enable_aggregation = var.enable_aggregation
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}
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