Merge branch '33360-generate-kubeconfig' into 'master'

Generate KUBECONFIG in KubernetesService#predefined_variables

Closes #33360

See merge request !12223

8 files changed, 150 insertions, 16 deletions

diff --git a/app/models/project_services/kubernetes_service.rb b/app/models/project_services/kubernetes_service.rb
index 48e7802c557..62f7c057c5b 100644
--- a/app/models/project_services/kubernetes_service.rb
+++ b/app/models/project_services/kubernetes_service.rb
@@ -96,10 +96,13 @@ class KubernetesService < DeploymentService
   end
 
   def predefined_variables
+    config = YAML.dump(kubeconfig)
+
     variables = [
       { key: 'KUBE_URL', value: api_url, public: true },
       { key: 'KUBE_TOKEN', value: token, public: false },
-      { key: 'KUBE_NAMESPACE', value: actual_namespace, public: true }
+      { key: 'KUBE_NAMESPACE', value: actual_namespace, public: true },
+      { key: 'KUBECONFIG', value: config, public: false, file: true }
     ]
 
     if ca_pem.present?
@@ -135,6 +138,14 @@ class KubernetesService < DeploymentService
 
   private
 
+  def kubeconfig
+    to_kubeconfig(
+      url: api_url,
+      namespace: actual_namespace,
+      token: token,
+      ca_pem: ca_pem)
+  end
+
   def namespace_placeholder
     default_namespace || TEMPLATE_PLACEHOLDER
   end
diff --git a/changelogs/unreleased/33360-generate-kubeconfig.yml b/changelogs/unreleased/33360-generate-kubeconfig.yml
new file mode 100644
index 00000000000..96f0b1bc93f
--- /dev/null
+++ b/changelogs/unreleased/33360-generate-kubeconfig.yml
@@ -0,0 +1,4 @@
+---
+title: Provide KUBECONFIG from KubernetesService for runners
+merge_request: 12223
+author:
diff --git a/doc/user/project/integrations/kubernetes.md b/doc/user/project/integrations/kubernetes.md
index 73fa83d72a8..bfe2672e098 100644
--- a/doc/user/project/integrations/kubernetes.md
+++ b/doc/user/project/integrations/kubernetes.md
@@ -55,6 +55,7 @@ GitLab CI build environment:
 - `KUBE_CA_PEM_FILE` - only present if a custom CA bundle was specified. Path
   to a file containing PEM data.
 - `KUBE_CA_PEM` (deprecated)- only if a custom CA bundle was specified. Raw PEM data.
+- `KUBECONFIG` - Path to a file containing kubeconfig for this deployment. CA bundle would be embedded if specified.
 
 ## Web terminals
 
diff --git a/lib/gitlab/kubernetes.rb b/lib/gitlab/kubernetes.rb
index c56c1a4322f..cdbdfa10d0e 100644
--- a/lib/gitlab/kubernetes.rb
+++ b/lib/gitlab/kubernetes.rb
@@ -76,5 +76,44 @@ module Gitlab
 
       url.to_s
     end
+
+    def to_kubeconfig(url:, namespace:, token:, ca_pem: nil)
+      config = {
+        apiVersion: 'v1',
+        clusters: [
+          name: 'gitlab-deploy',
+          cluster: {
+            server: url
+          }
+        ],
+        contexts: [
+          name: 'gitlab-deploy',
+          context: {
+            cluster: 'gitlab-deploy',
+            namespace: namespace,
+            user: 'gitlab-deploy'
+          }
+        ],
+        'current-context': 'gitlab-deploy',
+        kind: 'Config',
+        users: [
+          {
+            name: 'gitlab-deploy',
+            user: { token: token }
+          }
+        ]
+      }
+
+      kubeconfig_embed_ca_pem(config, ca_pem) if ca_pem
+
+      config.deep_stringify_keys
+    end
+
+    private
+
+    def kubeconfig_embed_ca_pem(config, ca_pem)
+      cluster = config.dig(:clusters, 0, :cluster)
+      cluster[:'certificate-authority-data'] = Base64.encode64(ca_pem)
+    end
   end
 end
diff --git a/spec/fixtures/config/kubeconfig-without-ca.yml b/spec/fixtures/config/kubeconfig-without-ca.yml
new file mode 100644
index 00000000000..b2cb989d548
--- /dev/null
+++ b/spec/fixtures/config/kubeconfig-without-ca.yml
@@ -0,0 +1,18 @@
+---
+apiVersion: v1
+clusters:
+- name: gitlab-deploy
+  cluster:
+    server: https://kube.domain.com
+contexts:
+- name: gitlab-deploy
+  context:
+    cluster: gitlab-deploy
+    namespace: NAMESPACE
+    user: gitlab-deploy
+current-context: gitlab-deploy
+kind: Config
+users:
+- name: gitlab-deploy
+  user:
+    token: TOKEN
diff --git a/spec/fixtures/config/kubeconfig.yml b/spec/fixtures/config/kubeconfig.yml
new file mode 100644
index 00000000000..c4e8e573c32
--- /dev/null
+++ b/spec/fixtures/config/kubeconfig.yml
@@ -0,0 +1,19 @@
+---
+apiVersion: v1
+clusters:
+- name: gitlab-deploy
+  cluster:
+    server: https://kube.domain.com
+    certificate-authority-data: "UEVN\n"
+contexts:
+- name: gitlab-deploy
+  context:
+    cluster: gitlab-deploy
+    namespace: NAMESPACE
+    user: gitlab-deploy
+current-context: gitlab-deploy
+kind: Config
+users:
+- name: gitlab-deploy
+  user:
+    token: TOKEN
diff --git a/spec/lib/gitlab/kubernetes_spec.rb b/spec/lib/gitlab/kubernetes_spec.rb
index e8c599a95ee..34b33772578 100644
--- a/spec/lib/gitlab/kubernetes_spec.rb
+++ b/spec/lib/gitlab/kubernetes_spec.rb
@@ -46,4 +46,28 @@ describe Gitlab::Kubernetes do
       expect(filter_by_label(items, app: 'foo')).to eq(matching_items)
     end
   end
+
+  describe '#to_kubeconfig' do
+    subject do
+      to_kubeconfig(
+        url: 'https://kube.domain.com',
+        namespace: 'NAMESPACE',
+        token: 'TOKEN',
+        ca_pem: ca_pem)
+    end
+
+    context 'when CA PEM is provided' do
+      let(:ca_pem) { 'PEM' }
+      let(:path) { expand_fixture_path('config/kubeconfig.yml') }
+
+      it { is_expected.to eq(YAML.load_file(path)) }
+    end
+
+    context 'when CA PEM is not provided' do
+      let(:ca_pem) { nil }
+      let(:path) { expand_fixture_path('config/kubeconfig-without-ca.yml') }
+
+      it { is_expected.to eq(YAML.load_file(path)) }
+    end
+  end
 end
diff --git a/spec/models/project_services/kubernetes_service_spec.rb b/spec/models/project_services/kubernetes_service_spec.rb
index 858ad595dbf..5ba523a478a 100644
--- a/spec/models/project_services/kubernetes_service_spec.rb
+++ b/spec/models/project_services/kubernetes_service_spec.rb
@@ -129,7 +129,7 @@ describe KubernetesService, models: true, caching: true do
     it "returns the default namespace" do
       is_expected.to eq(service.send(:default_namespace))
     end
-    
+
     context 'when namespace is specified' do
       before do
         service.namespace = 'my-namespace'
@@ -201,6 +201,22 @@ describe KubernetesService, models: true, caching: true do
   end
 
   describe '#predefined_variables' do
+    let(:kubeconfig) do
+      config =
+        YAML.load(File.read(expand_fixture_path('config/kubeconfig.yml')))
+
+      config.dig('users', 0, 'user')['token'] =
+        'token'
+
+      config.dig('clusters', 0, 'cluster')['certificate-authority-data'] =
+        Base64.encode64('CA PEM DATA')
+
+      config.dig('contexts', 0, 'context')['namespace'] =
+        namespace
+
+      YAML.dump(config)
+    end
+
     before do
       subject.api_url = 'https://kube.domain.com'
       subject.token = 'token'
@@ -208,32 +224,34 @@ describe KubernetesService, models: true, caching: true do
       subject.project = project
     end
 
-    context 'namespace is provided' do
-      before do
-        subject.namespace = 'my-project'
-      end
-
+    shared_examples 'setting variables' do
       it 'sets the variables' do
         expect(subject.predefined_variables).to include(
           { key: 'KUBE_URL', value: 'https://kube.domain.com', public: true },
           { key: 'KUBE_TOKEN', value: 'token', public: false },
-          { key: 'KUBE_NAMESPACE', value: 'my-project', public: true },
+          { key: 'KUBE_NAMESPACE', value: namespace, public: true },
+          { key: 'KUBECONFIG', value: kubeconfig, public: false, file: true },
           { key: 'KUBE_CA_PEM', value: 'CA PEM DATA', public: true },
           { key: 'KUBE_CA_PEM_FILE', value: 'CA PEM DATA', public: true, file: true }
         )
       end
     end
 
-    context 'no namespace provided' do
-      it 'sets the variables' do
-        expect(subject.predefined_variables).to include(
-          { key: 'KUBE_URL', value: 'https://kube.domain.com', public: true },
-          { key: 'KUBE_TOKEN', value: 'token', public: false },
-          { key: 'KUBE_CA_PEM', value: 'CA PEM DATA', public: true },
-          { key: 'KUBE_CA_PEM_FILE', value: 'CA PEM DATA', public: true, file: true }
-        )
+    context 'namespace is provided' do
+      let(:namespace) { 'my-project' }
+
+      before do
+        subject.namespace = namespace
       end
 
+      it_behaves_like 'setting variables'
+    end
+
+    context 'no namespace provided' do
+      let(:namespace) { subject.actual_namespace }
+
+      it_behaves_like 'setting variables'
+
       it 'sets the KUBE_NAMESPACE' do
         kube_namespace = subject.predefined_variables.find { |h| h[:key] == 'KUBE_NAMESPACE' }