From 1e4640f84485ac09922d8f751e47b1c59a6cc6dc Mon Sep 17 00:00:00 2001
From: Chris Kim <oats87g@gmail.com>
Date: Thu, 20 Jun 2024 21:57:55 +0000
Subject: [PATCH] Add support for CATTLE_AGENT_STRICT_VERIFY|STRICT_VERIFY
 environment variables to ensure kubeconfig CA data is valid

Signed-off-by: Chris Kim <oats87g@gmail.com>
---
 install.sh             | 10 ++++++++++
 main.go                | 15 +++++++++++----
 pkg/k8splan/watcher.go | 12 ++++++++----
 3 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/install.sh b/install.sh
index 98e20b29..750b9198 100755
--- a/install.sh
+++ b/install.sh
@@ -43,6 +43,7 @@ fi
 #   - CATTLE_AGENT_BINARY_LOCAL_LOCATION (default: )
 #   - CATTLE_AGENT_UNINSTALL_LOCAL (default: false)
 #   - CATTLE_AGENT_UNINSTALL_LOCAL_LOCATION (default: )
+#   - CATTLE_AGENT_STRICT_VERIFY | STRICT_VERIFY (default: false)
 
 FALLBACK=v0.2.9
 CACERTS_PATH=cacerts
@@ -390,6 +391,14 @@ setup_env() {
         fi
     fi
 
+    if [ -z "${CATTLE_AGENT_STRICT_VERIFY}" ]; then
+      CATTLE_AGENT_STRICT_VERIFY=false
+      if [ -n "${STRICT_VERIFY}" ]; then
+        CATTLE_AGENT_STRICT_VERIFY=${STRICT_VERIFY}
+      fi
+      info "Strict verification is set to ${CATTLE_AGENT_STRICT_VERIFY}"
+    fi
+
     if [ -z "${CATTLE_AGENT_CONFIG_DIR}" ]; then
         CATTLE_AGENT_CONFIG_DIR=/etc/rancher/agent
         info "Using default agent configuration directory ${CATTLE_AGENT_CONFIG_DIR}"
@@ -563,6 +572,7 @@ Restart=always
 RestartSec=5s
 Environment=CATTLE_LOGLEVEL=${CATTLE_AGENT_LOGLEVEL}
 Environment=CATTLE_AGENT_CONFIG=${CATTLE_AGENT_CONFIG_DIR}/config.yaml
+Environment=CATTLE_AGENT_STRICT_VERIFY=${CATTLE_AGENT_STRICT_VERIFY}
 ExecStart=${CATTLE_AGENT_BIN_PREFIX}/bin/rancher-system-agent sentinel
 EOF
 }
diff --git a/main.go b/main.go
index 48a080b7..7bea145b 100644
--- a/main.go
+++ b/main.go
@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os"
+	"strings"
 
 	"github.com/mattn/go-colorable"
 	"github.com/rancher/system-agent/pkg/applyinator"
@@ -17,9 +18,10 @@ import (
 )
 
 const (
-	cattleLogLevelEnv    = "CATTLE_LOGLEVEL"
-	cattleAgentConfigEnv = "CATTLE_AGENT_CONFIG"
-	defaultConfigFile    = "/etc/rancher/agent/config.yaml"
+	cattleLogLevelEnv          = "CATTLE_LOGLEVEL"
+	cattleAgentConfigEnv       = "CATTLE_AGENT_CONFIG"
+	cattleAgentStrictVerifyEnv = "CATTLE_AGENT_STRICT_VERIFY"
+	defaultConfigFile          = "/etc/rancher/agent/config.yaml"
 )
 
 func main() {
@@ -92,7 +94,12 @@ func run(c *cli.Context) error {
 			return fmt.Errorf("unable to parse connection info file: %w", err)
 		}
 
-		k8splan.Watch(topContext, *applyinator, connInfo)
+		var strictVerify bool // When strictVerify is set to true, the kubeconfig validator will not discard CA data if it is invalid
+		if strings.ToLower(os.Getenv(cattleAgentStrictVerifyEnv)) == "true" {
+			strictVerify = true
+		}
+
+		k8splan.Watch(topContext, *applyinator, connInfo, strictVerify)
 	}
 
 	if cf.LocalEnabled {
diff --git a/pkg/k8splan/watcher.go b/pkg/k8splan/watcher.go
index 1f22b74f..cd86ee54 100644
--- a/pkg/k8splan/watcher.go
+++ b/pkg/k8splan/watcher.go
@@ -54,13 +54,13 @@ const (
 	cooldownTimerDuration    = "30s"
 )
 
-func Watch(ctx context.Context, applyinator applyinator.Applyinator, connInfo config.ConnectionInfo) {
+func Watch(ctx context.Context, applyinator applyinator.Applyinator, connInfo config.ConnectionInfo, strictVerify bool) {
 	w := &watcher{
 		connInfo:    connInfo,
 		applyinator: applyinator,
 	}
 
-	go w.start(ctx)
+	go w.start(ctx, strictVerify)
 }
 
 type watcher struct {
@@ -86,14 +86,18 @@ func incrementCount(count []byte) []byte {
 	return []byte("1")
 }
 
-func (w *watcher) start(ctx context.Context) {
+func (w *watcher) start(ctx context.Context, strictVerify bool) {
 	kc, err := clientcmd.RESTConfigFromKubeConfig([]byte(w.connInfo.KubeConfig))
 	if err != nil {
 		panic(err)
 	}
 
+	if strictVerify && len(kc.CAData) == 0 {
+		logrus.Fatal("CA Data in provided kubeconfig was empty while strict verify was enabled. Aborting startup.")
+	}
+
 	if err := validateKC(ctx, kc); err != nil {
-		if strings.Contains(err.Error(), "x509: certificate signed by unknown authority") && len(kc.CAData) != 0 {
+		if strings.Contains(err.Error(), "x509: certificate signed by unknown authority") && len(kc.CAData) != 0 && !strictVerify {
 			logrus.Infof("Initial connection to Kubernetes cluster failed with error %v, removing CA data and trying again", err)
 			kc.CAData = nil // nullify the provided CA data
 			if err := validateKC(ctx, kc); err != nil {