TLS client: Simplify cert's verification code (#5656)

Fixes https://github.com/XTLS/Xray-core/issues/5655

main/commands/all/tls/hash.go

@@ -0,0 +1,78 @@
+package tls
+
+import (
+	"bytes"
+	"crypto/x509"
+	"encoding/pem"
+	"flag"
+	"fmt"
+	"os"
+	"text/tabwriter"
+
+	"github.com/xtls/xray-core/main/commands/base"
+	. "github.com/xtls/xray-core/transport/internet/tls"
+)
+
+var cmdHash = &base.Command{
+	UsageLine: "{{.Exec}} tls hash",
+	Short:     "Calculate TLS certificate hash.",
+	Long: `
+	xray tls hash --cert <cert.pem>
+	Calculate TLS certificate hash.
+	`,
+}
+
+func init() {
+	cmdHash.Run = executeHash // break init loop
+}
+
+var input = cmdHash.Flag.String("cert", "fullchain.pem", "The file path of the certificate")
+
+func executeHash(cmd *base.Command, args []string) {
+	fs := flag.NewFlagSet("hash", flag.ContinueOnError)
+	if err := fs.Parse(args); err != nil {
+		fmt.Println(err)
+		return
+	}
+	certContent, err := os.ReadFile(*input)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	var certs []*x509.Certificate
+	if bytes.Contains(certContent, []byte("BEGIN")) {
+		for {
+			block, remain := pem.Decode(certContent)
+			if block == nil {
+				break
+			}
+			cert, err := x509.ParseCertificate(block.Bytes)
+			if err != nil {
+				fmt.Println("Unable to decode certificate:", err)
+				return
+			}
+			certs = append(certs, cert)
+			certContent = remain
+		}
+	} else {
+		certs, err = x509.ParseCertificates(certContent)
+		if err != nil {
+			fmt.Println("Unable to parse certificates:", err)
+			return
+		}
+	}
+	if len(certs) == 0 {
+		fmt.Println("No certificates found")
+		return
+	}
+	tabWriter := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
+	for i, cert := range certs {
+		hash := GenerateCertHashHex(cert)
+		if i == 0 {
+			fmt.Fprintf(tabWriter, "Leaf SHA256:\t%s\n", hash)
+		} else {
+			fmt.Fprintf(tabWriter, "CA <%s> SHA256:\t%s\n", cert.Subject.CommonName, hash)
+		}
+	}
+	tabWriter.Flush()
+}