Verify peer cert function for better man in the middle prevention (#746)

* verify peer cert function for better man in the middle prevention

* publish cert chain hash generation algorithm

* added calculation of certificate hash as separate command and tlsping, use base64 to represent fingerprint to align with jsonPb

* apply coding style

* added test case for pinned certificates

* refactored cert pin

* pinned cert test

* added json loading of the PinnedPeerCertificateChainSha256

* removed tool to prepare for v5

* Add server cert pinning for Xtls

Change command "xray tls certChainHash" to xray style

Co-authored-by: Shelikhoo <xiaokangwang@outlook.com>

main/commands/all/tls/certchainhash.go

@@ -0,0 +1,41 @@
+package tls
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+
+	"github.com/xtls/xray-core/main/commands/base"
+	"github.com/xtls/xray-core/transport/internet/tls"
+)
+
+var cmdCertChainHash = &base.Command{
+	UsageLine: "{{.Exec}} certChainHash",
+	Short:     "Calculate TLS certificates hash.",
+	Long: `
+	xray tls certChainHash --cert <cert.pem>
+	Calculate TLS certificate chain hash.
+	`,
+}
+
+func init() {
+	cmdCertChainHash.Run = executeCertChainHash // break init loop
+}
+
+var input = cmdCertChainHash.Flag.String("cert", "fullchain.pem", "The file path of the certificates chain")
+
+func executeCertChainHash(cmd *base.Command, args []string) {
+	fs := flag.NewFlagSet("certChainHash", flag.ContinueOnError)
+	if err := fs.Parse(args); err != nil {
+		fmt.Println(err)
+		return
+	}
+	certContent, err := ioutil.ReadFile(*input)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	certChainHashB64 := tls.CalculatePEMCertChainSHA256Hash(certContent)
+	fmt.Println(certChainHashB64)
+	return
+}