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Email Security Record Check Script

Script Overview

This script checks DMARC, SPF, DKIM, and BIMI records for given domains. It provides color-coded output for easy interpretation of the results.

Functions

  1. check_dmarc

    • Checks for the presence of a DMARC record for a given domain.
    • Verifies if the policy is set to quarantine or reject.

  2. check_spf

    • Checks for the presence of an SPF record for a given domain.
    • Distinguishes between hard fail (-all), soft fail (~all), and no explicit fail condition.

  3. check_dkim

    • Checks for the presence of DKIM records for multiple common selectors.

  4. check_bimi

    • Checks for the presence of a BIMI record for a given domain.

Main Script Logic

  • Accepts two types of inputs: a file containing a list of domains (-f) or a single domain (-d).
  • For each domain, it calls the check_dmarc, check_spf, check_dkim, and check_bimi functions.
  • Displays error messages if the file does not exist or if the domain is not specified.

Usage

  • Check a file containing domains: 
    ./script.sh -f domains.txt


The script relies on a few dependencies and commands that need to be available on the system where it is executed.

Dependencies

bash
    The script is written in bash and requires the Bash shell to be installed on your system.

dig
    dig (Domain Information Groper) is a command-line tool used for querying DNS name servers.
    It is typically part of the bind-utils or dnsutils package, depending on the Linux distribution.

Color Support
    The script uses ANSI escape codes to print colored text in the terminal. This requires a terminal that supports ANSI escape codes.

Installation of Dependencies

Installing dig:
    On Debian-based systems (e.g., Ubuntu):

sudo apt-get update sudo apt-get install dnsutils

On Red Hat-based systems (e.g., CentOS, Fedora):

    sudo yum install bind-utils

Verifying Dependencies

Check if bash is installed:
    This is usually pre-installed on most Unix-like operating systems.
    To check the version of Bash:

    

bash --version

Check if dig is installed:

To verify if dig is installed and accessible:



    dig -v

Additional Notes

The script assumes that the DNS servers are reachable and that the network configuration allows DNS queries.
Ensure your terminal supports ANSI escape codes to see the colored output correctly.

Usage

You can run the script with either a single domain or a file containing a list of domains. Check a Single Domain

To check a single domain, use the -d option followed by the domain name: ./check_email_auth.sh -d example.com

Check Multiple Domains from a File

To check multiple domains, use the -f option followed by the filename. Each line in the file should contain one domain: ./check_email_auth.sh -f domains.txt

The script includes basic error handling to manage exceptions such as missing or invalid files and domains. If an error occurs, it will print an error message and continue execution.

Contributions are welcome! If you have suggestions for improvements or find a bug, please open an issue or submit a pull request.