check_certs.sh

#!/bin/sh
#
# BSD 2-Clause License
# 
# Copyright (c) 2019-2022, cs@brnfck.at and gerhard@tinned-software.net
# All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
# 
# 1. Redistributions of source code must retain the above copyright notice, this
#    list of conditions and the following disclaimer.
# 
# 2. Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
# 
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
VERSION=0.1.3
#


function usage
{
  echo "Usage: `basename $0` [-h|--help] [--tls protocol] <destination|filename> [openssl-options]"
  echo ""
  echo "Options:"
  echo "  -h, --help       Print this usage and exit"
  echo "  -v  --version           Print version information and exit"
  echo "  --tls protocol   The starttls protocol used by s_client --starttls"
  echo "                   'smtp', 'pop3', 'imap', 'ldap', ... see all in the s_client(1) man page"
  echo "  destination      Connect string used by openssl s_client to connect to."
  echo "  filename         Filename to read certificates from."
  echo "  openssl-options  Openssl x509 options to show required details for the certificates."
  echo "                   Default: -subject -issuer -email -dates -fingerprint -noout"
  echo ""
}

function version
{
  echo 
  echo "`basename $0` Version $VERSION"
  echo
  echo "Copyright (c) 2019-2022 cs@brnfck.at and gerhard@tinned-software.net"
  echo "BSD 2-Clause License <https://opensource.org/licenses/BSD-2-Clause>"
  echo 
}

if [ $# -lt 1 ]; then
  echo "ERROR: at least one argument (destination or local filename) required."
  usage
  exit 1
fi

if [ "$1" == "--version" ] || [ "$1" == "-v" ]; then
  version
  exit 0;
fi

if [ "$1" == "--help" ] || [ "$1" == "-h" ]; then
  usage
  exit 0;
fi
if [ "$1" == "--tls" ]; then
  CCMD_OPTION="-starttls $2"
  shift 2
fi
if [ -r "$1" ]; then
  CCMD=$(cat "$1")
else
  CCMD=$(echo | openssl s_client -connect $1 -showcerts ${CCMD_OPTION})
fi

shift
if [ ! -z "$*" ]; then
  SSLOPTS=$*
else
  SSLOPTS="-subject -issuer -email -dates -fingerprint -noout"
fi

FILETMP=$(mktemp)

echo -e "${CCMD}" | \
    awk -v SSLOPTS="${SSLOPTS}" -v FILETMP="${FILETMP}" '
        /-----BEGIN CERTIFICATE-----/,/-----END CERTIFICATE-----/ \
            {
                print >>FILETMP
            }
        /-----END CERTIFICATE-----/ \
            { 
                printf("\nCertificate details\n===================\n")
                system("cat "FILETMP" | openssl x509 "SSLOPTS" ; echo >"FILETMP)
            }
        END \
            { 
                print "----------------------------" ;
                system("rm "FILETMP)
            }'