Prints SSL certificate info from a given URL. Including the encoded public key and cert itself

cert_info.go

package main

import (
  "fmt"
  "os"
  "bytes"
  "encoding/pem"
  "crypto/tls"
  "crypto/x509"
)

func main() {
  conn, err := tls.Dial("tcp", os.Args[1] + ":443", &tls.Config{
      InsecureSkipVerify: true,
  })
  if err != nil {
      fmt.Println(err)
      return
  }

  var encodedCert bytes.Buffer
  err = pem.Encode(&encodedCert, &pem.Block{
    Type: "CERTIFICATE",
    Bytes: conn.ConnectionState().PeerCertificates[0].Raw,
  })
  if err != nil {
    fmt.Println(err)
    return
  }

  p, err := x509.MarshalPKIXPublicKey(conn.ConnectionState().PeerCertificates[0].PublicKey)
  if err != nil {
    fmt.Println(err)
    return
  }
  publicKey := string(pem.EncodeToMemory(&pem.Block{
    Type:  "PUBLIC KEY",
    Bytes: p,
  }))

  fmt.Print("Issuer: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].Issuer)
  fmt.Print("\nSubject: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].Subject)
  fmt.Print("\nSerial Number: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].SerialNumber)
  fmt.Print("\nVersion: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].Version)
  fmt.Print("\nNot Before: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].NotBefore)
  fmt.Print("\nNot After: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].NotAfter)
  fmt.Print("\nEmail Addresses: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].EmailAddresses)
  fmt.Print("\nIP Addresses: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].IPAddresses)
  fmt.Print("\nPermitted DNS Domains: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].PermittedDNSDomains)
  fmt.Print("\nExcluded DNS Domains: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].ExcludedDNSDomains)
  fmt.Print("\nPermitted IP Ranges: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].PermittedIPRanges)
  fmt.Print("\nEXcluded IP Ranges: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].ExcludedIPRanges)
  fmt.Print("\nPermitted Email Addresses: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].PermittedEmailAddresses)
  fmt.Print("\nExcluded Email Addresses: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].ExcludedEmailAddresses)
  fmt.Print("\nPermitted URI Domains: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].PermittedURIDomains)
  fmt.Print("\nExlucded URI Domains: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].ExcludedURIDomains)
  fmt.Print("\nOCSP Server: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].OCSPServer)
  fmt.Print("\nIssuing Certificate URL Server: ")
  fmt.Print(conn.ConnectionState().PeerCertificates[0].IssuingCertificateURL)
  fmt.Print("\nDNS Names: ")
  fmt.Println(conn.ConnectionState().PeerCertificates[0].DNSNames)
  fmt.Println("\nPublic Key: ")
  fmt.Println(publicKey)
  fmt.Println("Cert: ")
  fmt.Println(encodedCert.String())
}