Add additional tags for x509 Input Plugin

plugins/inputs/x509_cert/README.md

@@ -33,6 +33,12 @@ file or network connection.
     - province
     - locality
     - verification
+    - serial_number
+    - signature_algorithm
+    - public_key_algorithm
+    - issuer_common_name
+    - issuer_serial_number
+    - san
   - fields:
     - verification_code (int)
     - verification_error (string)

plugins/inputs/x509_cert/x509_cert.go

@@ -4,7 +4,6 @@ package x509_cert
 import (
 	"crypto/tls"
 	"crypto/x509"
-	"crypto/x509/pkix"
 	"encoding/pem"
 	"fmt"
 	"io/ioutil"
@@ -129,28 +128,43 @@ func getFields(cert *x509.Certificate, now time.Time) map[string]interface{} {
 	return fields
 }
 
-func getTags(subject pkix.Name, location string) map[string]string {
+func getTags(cert *x509.Certificate, location string) map[string]string {
 	tags := map[string]string{
-		"source":      location,
-		"common_name": subject.CommonName,
+		"source":               location,
+		"common_name":          cert.Subject.CommonName,
+		"serial_number":        cert.SerialNumber.Text(16),
+		"signature_algorithm":  cert.SignatureAlgorithm.String(),
+		"public_key_algorithm": cert.PublicKeyAlgorithm.String(),
 	}
 
-	if len(subject.Organization) > 0 {
-		tags["organization"] = subject.Organization[0]
+	if len(cert.Subject.Organization) > 0 {
+		tags["organization"] = cert.Subject.Organization[0]
 	}
-	if len(subject.OrganizationalUnit) > 0 {
-		tags["organizational_unit"] = subject.OrganizationalUnit[0]
+	if len(cert.Subject.OrganizationalUnit) > 0 {
+		tags["organizational_unit"] = cert.Subject.OrganizationalUnit[0]
 	}
-	if len(subject.Country) > 0 {
-		tags["country"] = subject.Country[0]
+	if len(cert.Subject.Country) > 0 {
+		tags["country"] = cert.Subject.Country[0]
 	}
-	if len(subject.Province) > 0 {
-		tags["province"] = subject.Province[0]
+	if len(cert.Subject.Province) > 0 {
+		tags["province"] = cert.Subject.Province[0]
 	}
-	if len(subject.Locality) > 0 {
-		tags["locality"] = subject.Locality[0]
+	if len(cert.Subject.Locality) > 0 {
+		tags["locality"] = cert.Subject.Locality[0]
 	}
 
+	tags["issuer_common_name"] = cert.Issuer.CommonName
+	tags["issuer_serial_number"] = cert.Issuer.SerialNumber
+
+	san := append(cert.DNSNames, cert.EmailAddresses...)
+	for _, ip := range cert.IPAddresses {
+		san = append(san, ip.String())
+	}
+	for _, uri := range cert.URIs {
+		san = append(san, uri.String())
+	}
+	tags["san"] = strings.Join(san, ",")
+
 	return tags
 }
 
@@ -172,7 +186,7 @@ func (c *X509Cert) Gather(acc telegraf.Accumulator) error {
 
 		for i, cert := range certs {
 			fields := getFields(cert, now)
-			tags := getTags(cert.Subject, location)
+			tags := getTags(cert, location)
 
 			// The first certificate is the leaf/end-entity certificate which needs DNS
 			// name validation against the URL hostname.

plugins/inputs/x509_cert/x509_cert_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/base64"
 	"fmt"
 	"io/ioutil"
+	"math/big"
 	"os"
 	"testing"
 	"time"
@@ -187,6 +188,61 @@ func TestGatherLocal(t *testing.T) {
 	}
 }
 
+func TestTags(t *testing.T) {
+	cert := fmt.Sprintf("%s\n%s", pki.ReadServerCert(), pki.ReadCACert())
+
+	f, err := ioutil.TempFile("", "x509_cert")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = f.Write([]byte(cert))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = f.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer os.Remove(f.Name())
+
+	sc := X509Cert{
+		Sources: []string{f.Name()},
+	}
+	sc.Init()
+
+	acc := testutil.Accumulator{}
+	err = sc.Gather(&acc)
+	require.NoError(t, err)
+
+	assert.True(t, acc.HasMeasurement("x509_cert"))
+
+	assert.True(t, acc.HasTag("x509_cert", "common_name"))
+	assert.Equal(t, "server.localdomain", acc.TagValue("x509_cert", "common_name"))
+
+	assert.True(t, acc.HasTag("x509_cert", "signature_algorithm"))
+	assert.Equal(t, "SHA256-RSA", acc.TagValue("x509_cert", "signature_algorithm"))
+
+	assert.True(t, acc.HasTag("x509_cert", "public_key_algorithm"))
+	assert.Equal(t, "RSA", acc.TagValue("x509_cert", "public_key_algorithm"))
+
+	assert.True(t, acc.HasTag("x509_cert", "issuer_common_name"))
+	assert.Equal(t, "Telegraf Test CA", acc.TagValue("x509_cert", "issuer_common_name"))
+
+	assert.True(t, acc.HasTag("x509_cert", "san"))
+	assert.Equal(t, "localhost,127.0.0.1", acc.TagValue("x509_cert", "san"))
+
+	assert.True(t, acc.HasTag("x509_cert", "serial_number"))
+	serialNumber := new(big.Int)
+	_, validSerialNumber := serialNumber.SetString(acc.TagValue("x509_cert", "serial_number"), 16)
+	if !validSerialNumber {
+		t.Errorf("Expected a valid Hex serial number but got %s", acc.TagValue("x509_cert", "serial_number"))
+	}
+	assert.Equal(t, big.NewInt(1), serialNumber)
+}
+
 func TestGatherChain(t *testing.T) {
 	cert := fmt.Sprintf("%s\n%s", pki.ReadServerCert(), pki.ReadCACert())