Provide CA Certificates via cloud-init's ca_certs module

pkg/probes/curl/curl_json.go

@@ -2,7 +2,9 @@ package curl
 
 import (
 	_ "embed"
+	"encoding/base64"
 	"fmt"
+	"gopkg.in/yaml.v3"
 	"os"
 	"strconv"
 	"strings"
@@ -104,17 +106,36 @@ func (clp Probe) GetExpandedUserData(userDataVariables map[string]string) (strin
 		return "", fmt.Errorf("invalid userdata variable DELAY: %w", err)
 	}
 
-	// For compatibility reasons, we expect CACERT to be either empty or a base64-encoded
-	// PEM-formatted CA certicate. When one is provided, we "render" it with a cloud-init
-	// preamble that writes the file to disk, and we tell curl about the cert file via flag
-	if userDataVariables["CACERT"] != "" {
-		cloudInitPreamble := `write_files:
-- path: /proxy.pem
-  permissions: '0755'
-  encoding: b64
-  content: `
-		userDataVariables["CACERT_RENDERED"] = cloudInitPreamble + userDataVariables["CACERT"]
-		userDataVariables["CURLOPT"] += " --cacert /proxy.pem "
+	// We expect CACERT to be either empty or a base64 encoded PEM-formatted CA certificate string.
+	// When a CA certificate is provided, we add it to the system's CA store via cloud-init.
+	// Docs: https://cloudinit.readthedocs.io/en/latest/reference/modules.html#ca-certificates
+	if cacert := userDataVariables["CACERT"]; cacert != "" {
+		type CaCert struct {
+			Trusted []string `yaml:"trusted"`
+		}
+		type CloudConfig struct {
+			CaCerts CaCert `yaml:"ca_certs"`
+		}
+
+		decodedCert, err := base64.StdEncoding.DecodeString(cacert)
+		if err != nil {
+			return "", fmt.Errorf("failed to base64 decode provided CA certificate: %w", err)
+		}
+
+		cloudInit := CloudConfig{
+			CaCerts: CaCert{
+				Trusted: []string{
+					strings.TrimSpace(string(decodedCert)),
+				},
+			},
+		}
+
+		cloudInitYamlBytes, cloudInitMarshalErr := yaml.Marshal(&cloudInit)
+		if cloudInitMarshalErr != nil {
+			return "", fmt.Errorf("unable to create cloud init config: %w", cloudInitMarshalErr)
+		}
+
+		userDataVariables["CACERT_RENDERED"] = strings.TrimSpace(string(cloudInitYamlBytes))
 	}
 
 	// Also for compatibility reasons, we map the NOTLS variable to curl's "insecure" flag

pkg/probes/curl/curl_json_test.go

@@ -57,7 +57,7 @@ func TestCurlJSONProbe_GetExpandedUserData(t *testing.T) {
 				"URLS":    "http://example.com:80 https://example.org:443",
 				"CACERT":  "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",
 			},
-			wantRegex: `#cloud-config[\s\S]*proxy.pem[\s\S]*encoding: b64[\s\S]*LS0tLS1CRUd\w*Cg==\n[\s\S]*https://example.org:443`,
+			wantRegex: `#cloud-config[\s\S]*ca_certs[\s\S]*trusted:[\s\S]*BEGIN CERTIFICATE[\s\S]*END CERTIFICATE`,
 		},
 		{
 			name: "set NOTLS",

pkg/probes/curl/userdata-template.yaml

@@ -6,7 +6,7 @@ runcmd:
   - dmesg -D
   - echo "${USERDATA_BEGIN}" >/dev/ttyS0
   - export http_proxy=${HTTP_PROXY} https_proxy=${HTTPS_PROXY}
-  - curl --retry 3 --retry-connrefused -t B -Z -s -I -m ${TIMEOUT} -w "%{stderr}${LINE_PREFIX}%{json}\n" ${CURLOPT} ${URLS} --proto =http,https,telnet ${TLSDISABLED_URLS_RENDERED} 2>/dev/ttyS0
+  - curl --capath /etc/pki/tls/certs/ --proxy-capath /etc/pki/tls/certs/ --retry 3 --retry-connrefused -t B -Z -s -I -m ${TIMEOUT} -w "%{stderr}${LINE_PREFIX}%{json}\n" ${CURLOPT} ${URLS} --proto =http,https,telnet ${TLSDISABLED_URLS_RENDERED} 2>/dev/ttyS0
   - echo "${USERDATA_END}" >/dev/ttyS0
 power_state:
   delay: ${DELAY}