在golang中执行echo和openssl命令

Question

I'm trying to read remote website ssl cert with this cli command openssl s_client -connect www.yahoo.no:443 2> /dev/null | openssl x509 -noout -enddate | cut -d = -f 2.

This works fine in cli, but when I execute it in golang:

package main

import (
    "bytes"
    "log"
    "os/exec"
    "time"
)

func main() {
    cmd := exec.Command("echo", "| openssl s_client -connect www.yahoo.com:443 2> /dev/null | openssl x509 -noout -enddate | cut -d = -f 2")
    var out bytes.Buffer
    cmd.Stdout = &out
    err := cmd.Run()

    log.Println(out.String())
}

I get nothing in return. How can I run this command in go?

UPDATE:

this is what I've tried but no success

func command() {

    cmd1 := exec.Command("openssl", "s_client", "-connect", "www.yahoo.no:443", "2>", "/dev/null")
    cmd2 := exec.Command("openssl", "x509", "-noout", "-enddate")

    var out bytes.Buffer

    reader, writer := io.Pipe()
    cmd1.Stdout = writer
    cmd2.Stdin = reader

    cmd2.Stdout = &out

    cmd1.Start()
    cmd2.Start()

    cmd1.Wait()
    writer.Close()

    cmd2.Wait()
    reader.Close()

    io.Copy(&out, reader)
    log.Println(out.String())

}

I get empty response.

Answer 1

Go's standard library contains a perfectly capable TLS implementation, so there is really no reason to launch two hefty openssl processes:

package main

import (
    "crypto/tls"
    "fmt"
    "log"
    "net"
    "time"
)

func main() {
    conn, err := net.Dial("tcp", "example.com:443")
    if err != nil {
            log.Fatal(err)
    }

    client := tls.Client(conn, &tls.Config{
            ServerName: "example.com",
    })
    defer client.Close()

    if err := client.Handshake(); err != nil {
            log.Fatal(err)
    }

    cert := client.ConnectionState().PeerCertificates[0]
    fmt.Println(cert.NotAfter.Format(time.RFC3339)) // Output: 2020-12-02T12:00:00Z
}