Let’s break down what this script does in detail. The script is named encrypt_and_decrypt.sh, authored by GJS (homelab-alpha), and its purpose is to provide functions to encrypt and decrypt files or directories using the AES-256 encryption algorithm with OpenSSL.

Here’s a detailed explanation:

Script Metadata

  • Filename: encrypt_and_decrypt.sh
  • Author: GJS (homelab-alpha)
  • Date: May 26, 2024
  • Version: 1.0.1
  • Description: This script provides functions for encrypting and decrypting files or directories using AES-256 encryption with OpenSSL.
  • RAW Script: encrypt_and_decrypt.sh

Script Overview

The script defines two main functions:

  1. file-encrypt: Encrypts a given file or directory.
  2. file-decrypt: Decrypts a previously encrypted file or directory.

Function: file-encrypt

Purpose

The file-encrypt function encrypts files or directories using the AES-256 encryption algorithm with OpenSSL.


Usage 

file-encrypt <input_file_or_directory>
  • <input_file_or_directory>: The file or directory to be encrypted.

Code Breakdown 

function file-encrypt() {
    if [ -z "$1" ]; then
        echo "Usage: file-encrypt <input_file_or_directory>"
        return 1
    fi

    local input="$1"
    local output="${input}.aes256"

    if [ -e "$output" ]; then
        echo "Error: Output file already exists. Please choose a different name."
        return 1
    fi

    openssl enc -aes-256-ctr -pbkdf2 -salt -in "$input" -out "$output"
    if openssl_exit_code=$? && [ $openssl_exit_code -eq 0 ]; then
        echo ""
        echo "${input} has been successfully encrypted as ${output}."
        chmod 644 "$output"
    else
        echo "Encryption failed."
    fi
}

  1. Parameter Check: The function first checks if the user provided an input file or directory. If not, it prints the usage message and exits with a status of 1.
  2. Variables:
    • input: Stores the input file or directory name.
    • output: Stores the name of the output encrypted file, which is the input name appended with .aes256.
  3. Output File Check: Checks if a file with the output name already exists. If it does, it prints an error message and exits.
  4. Encryption: Uses the OpenSSL command to encrypt the input file with AES-256 in CTR mode, using PBKDF2 for key derivation and adding a salt.
  5. Success Message: If the encryption is successful, it prints a success message and sets the permissions of the output file to 644. If the encryption fails, it prints an error message.

Function: file-decrypt

Purpose

The file-decrypt function decrypts files or directories that were encrypted using the AES-256 encryption algorithm with OpenSSL.


Usage 

file-decrypt <input_file>
  • <input_file>: The file to be decrypted.

Code Breakdown 

function file-decrypt() {
    if [ -z "$1" ]; then
        echo "Usage: file-decrypt <input_file>"
        return 1
    fi

    local input="$1"
    local output="${input%.aes256}"

    if [ -e "$output" ]; then
        echo "Error: Output file already exists. Please choose a different name."
        return 1
    fi

    openssl enc -aes-256-ctr -pbkdf2 -d -salt -in "$input" -out "$output"
    if openssl_exit_code=$? && [ $openssl_exit_code -eq 0 ]; then
        echo ""
        echo "${input} has been successfully decrypted as ${output}."
        chmod 644 "$output"
    else
        echo "Decryption failed."
    fi
}

  1. Parameter Check: Similar to file-encrypt, it checks if an input file is provided. If not, it prints the usage message and exits with a status of 1.
  2. Variables:
    • input: Stores the input filename.
    • output: Stores the name of the output decrypted file by removing the .aes256 extension from the input name.
  3. Output File Check: Checks if a file with the output name already exists. If it does, it prints an error message and exits.
  4. Decryption: Uses the OpenSSL command to decrypt the input file with AES-256 in CTR mode, using PBKDF2 for key derivation and adding a salt.
  5. Success Message: If the decryption is successful, it prints a success message and sets the permissions of the output file to 644. If the decryption fails, it prints an error message.

Conclusion

By following these steps, the script ensures secure encryption and decryption of files and directories, making it useful for protecting sensitive data.

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Last updated 22 Sep 2024, 12:15 CEST . history