Let’s break down what this script does in detail. The script is named gpg_keygen_script.sh, authored by GJS (homelab-alpha), and its purpose is to generate a GPG key pair for secure communication. The script checks for required software, generates the key pair, and logs the actions. It also provides options for verbose output and specifying the GPG directory.

Here’s a detailed explanation:

Script Metadata

  • Filename: gpg_keygen_script.sh
  • Author: GJS (homelab-alpha)
  • Date: May 18, 2024
  • Version: 1.0.1
  • Description: This script generates a GPG key pair for secure communication. It checks for required software, generates the key pair, and logs the actions. The script also provides options for verbose output and specifying the GPG directory.
  • RAW Script: gpg_keygen_script.sh

Script Header

The script begins with metadata and usage instructions, providing a clear overview of its purpose, options, and examples of how to use it.


Functions

Color and Header Printing

  • print_cyan(): This function prints text in cyan color, enhancing readability.
print_cyan() {
  echo -e "\e[36m$1\e[0m"
}
  • print_section_header(): This function prints section headers in cyan to separate different parts of the script’s output.
print_section_header() {
  echo ""
  echo ""
  echo -e "$(print_cyan "=== $1 ===")"
}

Verbose Information Display

  • display_verbose_info(): If the verbose mode is enabled, this function lists the GPG keys in long format.
display_verbose_info() {
  if [ "$verbose" == "true" ]; then
    print_section_header "GPG Key:"
    gpg --list-keys --keyid-format LONG
  fi
}

Logging

  • log_message(): This function logs messages with a timestamp to a specified log file. It ensures that all actions and errors are recorded.
log_message() {
  local timestamp
  timestamp=$(date +"%Y-%m-%d %H:%M:%S")
  local message="$1"

  echo "${timestamp} - ${message}" | tee -a "$log_file" >&2
}

Usage Instructions

  • display_usage(): This function displays usage instructions and exits the script. It is invoked when the user provides incorrect command-line options.
display_usage() {
  echo "Usage: $0 [-v] [-d /path/to/gpg_directory]"
  echo "Options:"
  echo "  -v, --verbose    Enable verbose mode"
  echo "  -d, --directory  Specify the path to the GPG directory (default is \$HOME/.gnupg)"
  exit 1
}

Software Check

  • check_required_software(): This function checks if GPG is installed. If not, it logs an error and exits the script.
check_required_software() {
  if ! command -v "gpg" >/dev/null 2>&1; then
    log_message "Error: GPG is not installed. Please install GPG before running this script."
    exit 1
  else
    log_message "GPG is installed."
  fi
}

Key Pair Generation

  • generate_key_pair(): This function generates a new GPG key pair using gpg --full-generate-key. It logs the command and prints a section header.
generate_key_pair() {
  log_message "Generating new GPG key pair..."
  print_section_header "Generating new GPG key pair"
  log_message "Executing command: gpg --full-generate-key"
  gpg --full-generate-key
}

Key File Existence Check

  • check_key_file_existence(): This function checks if a GPG key pair already exists in the specified directory. If found, it logs a message and exits to prevent overwriting existing keys.
check_key_file_existence() {
  if [ -f "$gpg_dir/pubring.kbx" ]; then
    log_message "The GPG key pair already exists."
    log_message "=== end of the log ==="
    echo "$(print_cyan "Error:") The GPG key pair already exists."
    exit 1
  fi
}

Command-Line Options Parsing

  • parse_command_line_options(): This function parses the command-line options (-v for verbose mode and -d for specifying the GPG directory). It sets appropriate variables based on user input.
parse_command_line_options() {
  while [[ $# -gt 0 ]]; do
    case "$1" in
    -v | --verbose)
      verbose=true
      shift
      ;;
    -d | --directory)
      shift
      gpg_dir="$1"
      shift
      ;;
    *)
      display_usage
      ;;
    esac
  done
}

Signal Trapping

  • trap_handler: This function is set to handle interrupt signals (like SIGINT and SIGTERM). It ensures that the script handles interruptions gracefully.
trap trap_handler SIGINT SIGTERM

Main Program Execution

  1. Default Values: Sets default values for the GPG directory and log file.
gpg_dir="$HOME/.gnupg"
log_file="$gpg_dir/gpg_keygen_script.log"
  1. Start Logging: Begins logging, marking the start of the log file with a separator.
echo "" >>"$log_file" # Add an empty line after the marker for separation
log_message "=== beginning of the log ==="
log_message "Script execution started"
  1. Check Required Software: Ensures GPG is installed.
check_required_software
  1. Initialize Options: Initializes options, setting verbose mode to false by default.
verbose=false
  1. Parse Command-Line Options: Parses any provided command-line options.
parse_command_line_options "$@"
  1. Directory and Log File Check: Checks if the GPG directory and log file exist. Creates them if they don’t.
if [ ! -d "$gpg_dir" ]; then
  mkdir -p "$gpg_dir" && log_message "Created directory: $gpg_dir"
fi

if [ ! -f "$log_file" ]; then
  touch "$log_file" && log_message "Created log file: $log_file"
fi
  1. Check Key File Existence: Ensures no existing GPG key pair is present to avoid overwriting.
check_key_file_existence
  1. Generate Key Pair: Generates the GPG key pair.
generate_key_pair
  1. Display Verbose Information: If verbose mode is enabled, it displays the generated keys.
display_verbose_info
  1. Complete Logging: Marks the end of the log, indicating script completion.
log_message "Script execution completed."
log_message "=== end of the log ==="

Conclusion

The gpg_keygen_script.sh script is a comprehensive tool for generating GPG key pairs. It ensures necessary software is installed, handles user input gracefully, provides verbose output if needed, logs all actions, and ensures existing keys are not overwritten. This makes it a robust solution for secure communication setup.

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Last updated 01 Sep 2024, 10:22 CEST . history