Fix #296 (Cyberghost implementation) (#297)

* Reads the client key from /gluetun/client.key
* Read the client certificate from /gluetun/client.crt
* Additional checks for client key and client certificate validity
* Fix client key file parsing if environment variable isn't present

internal/params/cyberghost.go

@@ -1,6 +1,8 @@
 package params
 
 import (
+	"encoding/pem"
+	"fmt"
 	"strings"
 
 	"github.com/qdm12/gluetun/internal/constants"
@@ -22,7 +24,7 @@ func (p *reader) GetCyberghostRegions() (regions []string, err error) {
 }
 
 // GetCyberghostClientKey obtains the one line client key to use for openvpn from the
-// environment variable CLIENT_KEY.
+// environment variable CLIENT_KEY or from the file at /gluetun/client.key.
 func (p *reader) GetCyberghostClientKey() (clientKey string, err error) {
 	clientKey, err = p.envParams.GetEnv("CLIENT_KEY", libparams.CaseSensitiveValue())
 	if err != nil {
@@ -30,12 +32,45 @@ func (p *reader) GetCyberghostClientKey() (clientKey string, err error) {
 	} else if len(clientKey) > 0 {
 		return clientKey, nil
 	}
-	content, err := p.fileManager.ReadFile("/files/client.key")
+	content, err := p.fileManager.ReadFile(string(constants.ClientKey))
 	if err != nil {
 		return "", err
 	}
-	s := string(content)
+	return extractClientKey(content)
+}
+
+func extractClientKey(b []byte) (key string, err error) {
+	pemBlock, _ := pem.Decode(b)
+	if pemBlock == nil {
+		return "", fmt.Errorf("cannot decode PEM block from client key")
+	}
+	parsedBytes := pem.EncodeToMemory(pemBlock)
+	s := string(parsedBytes)
 	s = strings.ReplaceAll(s, "\n", "")
-	s = strings.ReplaceAll(s, "\r", "")
+	s = strings.TrimPrefix(s, "-----BEGIN PRIVATE KEY-----")
+	s = strings.TrimSuffix(s, "-----END PRIVATE KEY-----")
+	return s, nil
+}
+
+// GetCyberghostClientCertificate obtains the client certificate to use for openvpn from the
+// file at /gluetun/client.crt.
+func (p *reader) GetCyberghostClientCertificate() (clientCertificate string, err error) {
+	content, err := p.fileManager.ReadFile(string(constants.ClientCertificate))
+	if err != nil {
+		return "", err
+	}
+	return extractClientCertificate(content)
+}
+
+func extractClientCertificate(b []byte) (certificate string, err error) {
+	pemBlock, _ := pem.Decode(b)
+	if pemBlock == nil {
+		return "", fmt.Errorf("cannot decode PEM block from client certificate")
+	}
+	parsedBytes := pem.EncodeToMemory(pemBlock)
+	s := string(parsedBytes)
+	s = strings.ReplaceAll(s, "\n", "")
+	s = strings.TrimPrefix(s, "-----BEGIN CERTIFICATE-----")
+	s = strings.TrimSuffix(s, "-----END CERTIFICATE-----")
 	return s, nil
 }