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ssh_keygen_script.info

This script, automates the creation and conversion of SSH key pairs, supporting both ed25519 and RSA key types. It allows users to specify key type, filename, and SSH directory, while logging all actions and errors for traceability.

info

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Let’s break down what this script does in detail. The script is named ssh_keygen_script.sh, authored by GJS (homelab-alpha), and its purpose is to automate the generation and conversion of SSH key pairs for secure communication. It supports both ed25519 and RSA key types, allowing users to specify the desired key type, filename for the key pair, and SSH directory. Additionally, the script logs all actions and errors to a designated log file for traceability.

Here’s a detailed explanation:

Script Metadata

Filename: ssh_keygen_script.sh
Author: GJS (homelab-alpha)
Date: May 18, 2024
Version: 1.0.1
Description: This script automates the generation and conversion of SSH key pairs for secure communication. It supports both ed25519 and RSA key types, allowing users to specify the desired key type, filename for the key pair, and SSH directory. The script logs all actions and errors to a designated log file for traceability.
RAW Script: ssh_keygen_script.sh

Usage Instructions

Usage: ./ssh_keygen_script.sh [-v] [-d /path/to/ssh_directory]
Options:
- -v, --verbose: Enable verbose mode to display detailed information during execution.
- -d, --directory: Specify the path to the SSH directory. The default directory is $HOME/.ssh.
Examples:
1. Generate and convert an SSH key pair: ./ssh_keygen_script.sh
2. Generate and convert an SSH key pair with verbose output: ./ssh_keygen_script.sh -v
3. Generate and convert an SSH key pair with a custom SSH directory: ./ssh_keygen_script.sh -d /custom/path/to/ssh_directory

Default Values and Configuration

Default SSH Directory: $HOME/.ssh
Default File Extension for Converted Keys: ppk
Log File Path: $ssh_dir/ssh_keygen_script.log

Script Functions

Utility Functions

Print in Cyan Color: The print_cyan function prints text in cyan color for better readability in the terminal.
```
print_cyan() {
  echo -e "\e[36m$1\e[0m"
}
```
Print Section Headers: The print_section_header function prints section headers in cyan color.
```
print_section_header() {
  echo ""
  echo ""
  echo -e "$(print_cyan "=== $1 ===")"
}
```

Display Verbose Information: The display_verbose_info function prints the contents of the generated and converted public keys if verbose mode is enabled.

display_verbose_info() {
  local key_type="$1"
  local key_file="$2"
  local extension="$3"

  if [ "$verbose" == "true" ]; then
    print_cyan "${key_type} public key:"
    cat "${key_file}.pub"
    print_cyan "Converted ${key_type} public key:"
    cat "${key_file}.${extension}"
  fi
}

Log Messages: The log_message function logs actions and errors with a timestamp to the log file.

log_message() {
  local timestamp
  timestamp=$(date +"%Y-%m-%d %H:%M:%S")

  echo "${timestamp} - ${1}" >>"$log_file" 2>&1
}

Main Functionalities

Start Logging: Initializes logging at the start of script execution.

echo "" >>"$log_file"
log_message "=== beginning of the log ==="
log_message "Script execution started"

Display Usage Instructions: Provides usage information for the script.

display_usage() {
  echo "Usage: $0 [-v] [-d /path/to/ssh_directory]"
  echo "Options:"
  echo "  -v, --verbose    Enable verbose mode"
  echo "  -d, --directory  Specify the path to the SSH directory (default is \$HOME/.ssh)"
  exit 1
}

Check Required Software: Ensures required software (ssh-keygen and putty) are installed. Exits with an error if any are missing.

check_required_software() {
  local software_list=("ssh-keygen" "putty")
  local missing_software=()

  for software in "${software_list[@]}"; do
    if ! command -v "$software" >/dev/null 2>&1; then
      missing_software+=("$software")
    fi
  done

  if [ ${#missing_software[@]} -eq 0 ]; then
    log_message "All required software is installed."
  else
    log_message "Error: The following required software is not installed: ${missing_software[*]}"
    log_message "Please install the missing software manually."
    exit 1
  fi
}

Trap Signals: Handles script interruption signals for clean termination.

trap_handler() {
  echo ""
  log_message "Script execution interrupted. Cleaning up..."
  echo "=== end of the log ===" >>"$log_file"
  exit 1
}

Generate Key Pair: Generates an SSH key pair of the specified type.

generate_key_pair() {
  local key_type="$1"
  local file_name="$2"

  log_message "Generating new ${key_type} SSH key pair for server: ${server}, filename: ${file_name}"
  print_section_header "Generating new ${key_type} SSH key pair"
  if ssh-keygen -a 100 -C "${server}" -f "${ssh_dir}/id_${key_type}_${file_name}" -t "${key_type}" >>"$log_file" 2>&1; then
    log_message "Successfully generated ${key_type} SSH key pair for filename: ${file_name}"
  else
    log_message "Failed to generate ${key_type} SSH key pair for filename: ${file_name}"
    log_message "=== end of the log ==="
    exit 1
  fi
}

Convert Key Pair: Converts the generated SSH key pair to a specified format using puttygen.

convert_key_pair() {
  local key_type="$1"
  local file_name="$2"

  log_message "Convert ${key_type} SSH key pair to ${file_name}.${file_extension}"
  print_section_header "Convert ${key_type} SSH key pair to ${file_name}.${file_extension}"
  if puttygen "${ssh_dir}/id_${key_type}_${file_name}" -o "${ssh_dir}/id_${key_type}_${file_name}.${file_extension}" >>"$log_file" 2>&1; then
    log_message "Successfully converted ${key_type} SSH key pair for filename: ${file_name}"
  else
    log_message "Failed to convert ${key_type} SSH key pair for filename: ${file_name}"
    log_message "=== end of the log ==="
    exit 1
  fi
}

Check Key File Existence: Ensures that the specified key file does not already exist to avoid overwriting.

check_key_file_existence() {
  local key_type="$1"
  local file_name="$2"

  if [ -f "${ssh_dir}/id_${key_type}_${file_name}" ]; then
    log_message "The ${key_type} SSH key pair already exists for filename: ${file_name}"
    log_message "=== end of the log ==="
    echo "$(print_cyan "Error:") The ${key_type} SSH key pair already exists for filename: ${file_name}"
    exit 1
  fi
}

Choose Key Type: Prompts the user to select the SSH key type and then generates and converts the key pair.

choose_key_type() {
  echo ""
  print_cyan "Choose the SSH key type:"
  PS3="Enter your choice (1 for ed25519, 2 for RSA): "
  options=("ed25519" "RSA")
  select KEY_TYPE in "${options[@]}"; do
    case $KEY_TYPE in
    "ed25519")
      check_key_file_existence "ed25519" "${file_name}"
      generate_key_pair "ed25519" "${file_name}"
      convert_key_pair "ed25519" "${file_name}"
      display_verbose_info "ed25519" "${ssh_dir}/id_ed25519_${file_name}" "${file_extension}"
      log_message "Ed25519 SSH key pair generated and converted for filename: ${file_name}"
      break
      ;;
    "RSA")
      check_key_file_existence "rsa" "${file_name}"
      generate_key_pair "rsa" "${file_name}"
      convert_key_pair "rsa" "${file_name}"
      display_verbose_info "RSA" "${ssh_dir}/id_rsa_${file_name}" "${file_extension}"
      log_message "RSA SSH key pair generated and converted for filename: ${file_name}"
      break
      ;;
    *)
      echo "Invalid option. Choose 1 for ed25519 or 2 for RSA."
      ;;
    esac
  done
}

Script Execution

Check Required Software: Ensures necessary software is installed.
```
check_required_software
```

Initialize Options: Parses command-line options for verbose mode and custom SSH directory.

verbose=false
while [[ $# -gt 0 ]]; do
  case "$1" in
  -v | --verbose)
    verbose=true
    shift
    ;;
  -d | --directory)
    shift
    ssh_dir="$1"
    shift
    ;;
  *)
    display_usage
    ;;
  esac
done

Trap Interrupts: Sets up handlers for script interruption.
```
trap trap_handler SIGINT SIGTERM
```

Prompt for SSH Key Pair Information: Collects user input for server name and filename.

read -r -p "$(print_cyan "Enter the server name: ")" server
read -r -p "$(print_cyan "Enter the filename for the new SSH key pair: ")" file_name

Check Key File Existence: Ensures the specified key file does not already exist.

check_key_file_existence "ed25519" "${file_name}"
check_key_file_existence "rsa" "${file_name}"

Choose Key Type: Prompts user to select key type and proceeds with generation and conversion.
```
choose_key_type
```

Log Completion: Logs the completion of script execution.

log_message "Script execution completed for filename: ${file_name}"
log_message "=== end of the log ==="

This detailed breakdown provides a comprehensive understanding of the ssh_keygen_script.sh script, covering its purpose, usage, key functionalities, and execution flow.

Conclusion

This script provides a comprehensive solution for generating and converting SSH key pairs with built-in logging, verbose output options, and robust error handling to ensure a smooth and traceable execution process.

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

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ssh_keygen_script.info

Script Metadata link

Usage Instructions link

Default Values and Configuration link

Script Functions link

Utility Functions link

Main Functionalities link

Script Execution link

Conclusion link