shell script to retrieve ssl certificate by using openssl s_client

 shell script to retrieve ssl certificate by using openssl client

#!/bin/bash

# Function to retrieve certificate for a given hostname and port

function get_cert {

  HOSTNAME="$1"

  PORT="$2"

  # Retrieve the certificate and extract the end-entity certificate

  CERT=$(echo | openssl s_client -showcerts -servername "$HOSTNAME" -connect "$HOSTNAME":"$PORT" 2>/dev/null | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | sed -n '1,/END CERTIFICATE/p')

  # Save the certificate in PEM format to a file

  echo "$CERT" > site_cert.pem

  echo "Certificate for $HOSTNAME:$PORT saved to site_cert.pem"

}

# Array of sites and corresponding ports

SITES=(

  "example.com:443"

  "google.com:443"

  "yahoo.com:443"

  "github.com:443"

  "reddit.com:443"

  "twitter.com:443"

  "linkedin.com:443"

  "stackoverflow.com:443"

)

# Print the list of sites as options

printf "Select one or more options by number:\n"

for i in "${!SITES[@]}"; do

  printf "%s) %s\n" "$((i+1))" "${SITES[$i]}"

done

# Prompt the user to enter options

printf "Enter one or more options (e.g. 1 3 5): "

read OPTIONS

# Loop through the options and call get_cert for each corresponding hostname and port

for OPT in $OPTIONS; do

  INDEX=$(( $OPT - 1 ))

  if [ $INDEX -ge 0 ] && [ $INDEX -lt ${#SITES[@]} ]; then

    HOSTNAME=$(echo "${SITES[$INDEX]}" | cut -d':' -f1)

    PORT=$(echo "${SITES[$INDEX]}" | cut -d':' -f2)

    get_cert "$HOSTNAME" "$PORT"

  else

    printf "Invalid option: %s\n" "$OPT"

  fi

done