bash script, depends on openssl and perl, to show cert chain subject and issuer for a host. Runs on OS X

showcertssubjectandissuer

#!/bin/bash

# uncomment to debug
# set -x

usage() {
  printf "%s: display subject and issuer of certificates in the chain that a host presents\n" $0
  printf "usage:\n"
  printf "   %s HOSTNAME\n" $0
  printf "      show cert subject and issuer\n\n"
  exit 0
}

showcertinfo() {
  local servername=$1
  local foundSni=$(echo -n | openssl s_client -connect ${servername}:443 -servername ${servername} 2>&1 | openssl x509 -noout -text | grep ${servername})

  local opensslcmd
  if [[ -z "$foundSni" ]] ; then
    opensslcmd="openssl s_client -showcerts -connect ${servername}:443"
  else
    opensslcmd="openssl s_client -showcerts -connect ${servername}:443 -servername ${servername}"
  fi

  $opensslcmd < /dev/null 2> /dev/null | perl -e 'while(<>) {
   if($_ =~ /^ +i:.+$/) {
      $issuer = $_;
      chop $issuer;
   }
   if($_ =~ /^ [0-9] s:.+$/) {
      $subject = $_;
      chop $subject;
   }
   if($_ =~ /^\-\-\-\-\-END CERTIFICATE\-+$/) {
      print " $subject\n";
      print " $issuer\n\n";
   }
}'
}


if [[ $# -lt 1 ]]
then
  usage
fi

while test $# -gt 0
do
  case $1 in
    # -h|--help|usage|show this usage
    -h|--help)
      usage
      exit 1
      ;;
    *)
     showcertinfo "$1"
  esac
  shift
done