Message-ID: <CAFf+5zgmy9p3vLHKY6qeTKJO=RQa8z0H8dNs8BfqDr9D-1GC9g@mail.gmail.com>
Date: Thu, 5 Jun 2025 10:23:42 +0530
From: Amit <amitchoudhary0523@...il.com>
To: linux-kernel@...r.kernel.org
Subject: Encrypt decrypt file using password as key (simple algorithm) (File: encrypt_decrypt_file.php).

Encrypt decrypt file using password as key (simple algorithm) (File:
encrypt_decrypt_file.php).

---------------------------------
encrypt_decrypt_file.php
---------------------------------

<?php

$e_option_present = FALSE;
$d_option_present = FALSE;
$op = "";
$op_str = "";
$input_file = "";
$output_file = "";
$in_handle = NULL;
$out_handle = NULL;
$password = "";
$max_password_len = 20;
$actual_password_len = 0;
$help_msg = "Please see how to use this program/script by using the --help" .
            " option (encrypt_decrypt_file --help).";
$buf_size = 8192;

// error handler function
function custom_error_handler($errno, $errstr, $errfile, $errline)
{
    //echo "Got error/notice/warning, etc.\n";
    //echo $errno . "\n";
    //echo $errtsr . "\n";
    //echo $errfile . "\n";
    //echo $errline . "\n";
    return true;
} // end of custom_error_handler
// set to the user defined error handler
$old_error_handler = set_error_handler("custom_error_handler");

function print_usage()
{
    echo ("Usage:\n\n" .
          "  Syntax:\n\n" .
          "    encrypt_decrypt_file OPTION INPUT_FILE\n\n" .
          "  Description:\n\n" .
          "    encrypt_decrypt_file will encrypt or decrypt INPUT_FILE\n" .
          "    according to the option given by the user.\n" .
          "    \n" .
          "    encrypt_decrypt_file will ask the user for a password and\n" .
          "    then use this password to encrypt or decrypt the INPUT_FILE\n" .
          "    (according to the option given by the user).\n" .
          "    \n" .
          "    The password for decrypting the input file should be the\n" .
          "    same as the password given for encrypting the original input\n" .
          "    file.\n" .
          "    \n" .
          "    The name of the output file will be\n" .
          "    input_file_name.[encrypted|decrypted] and it will be created\n" .
          "    in the same directory in which the INPUT_FILE is present.\n" .
          "    \n" .
          "    In case, the directory already has a file with the same name\n" .
          "    as the output file name, then this script will exit without\n" .
          "    doing anything and print an appropriate error message.\n" .
          "    \n" .
          "    Basically, this can be considered as protecting a file with\n" .
          "    a password.\n" .
          "    \n" .
          "  Options:\n\n" .
          "     -e\n" .
          "        Encrypt the INPUT_FILE.\n\n" .
          "     -d\n" .
          "        Decrypt the INPUT_FILE.\n\n" .
          "    --help\n".
          "        Print this usage/help and exit.\n\n");
} // end of print_usage

// print debug info
function print_debug_info()
{
    global $argc, $argv, $input_file, $output_file;
    echo "DEBUG_INFO_START:\n\n";
    echo "Number of arguments = " . ($argc - 1) . "\n\n";
    for ($i = 1; $i < $argc; $i++) {
        $arg = trim($argv[$i]);
        echo "Argument " . $i . ": " . $arg . "\n";
    }
    echo "\n";
    echo "input_file: '$input_file'\n";
    echo "output_file: '$output_file'\n";
    echo "\nDEBUG_INFO_END\n\n";
} // end of print_debug_info

function close_file_handles()
{
    global $in_handle, $out_handle;
    fclose($in_handle);
    fclose($out_handle);
} // end of close_file_handles

function delete_output_file()
{
    if (unlink($output_file) == FALSE) {
        echo "Error: Failed to delete output file. Please delete it" .
             " manually. Exiting..\n";
    }
} // end of delete_output_file

echo "\n";

//---- trim all elements of argv[] (including argv[0]) and store in an arg_list
//      so that I don't have to trim argv[] everywhere.

//---- check testing from here.

//---- check correctness of program.

// check for --help option first
for ($i = 1; $i < $argc; $i++) {
    $arg = trim($argv[$i]);
    if ($arg === '--help') {
        print_usage();
        exit(0);
    }
}

if ($argc != 3) {
    echo "Error: (Only) two arguments are required: -e|-d and an input file" .
         " name. Exiting..\n";
    echo "\n";
    echo "Number of arguments given = " . ($argc - 1) . "\n";
    echo "\n";
    echo "Arguments given are: ";
    if ($argc > 1) {
        echo "\n";
        for ($i = 1; $i < $argc; $i++) {
            $arg = trim($argv[$i]);
            echo "    Argument " . $i . ": " . $arg . "\n";
        }
    } else {
        echo "None\n";
    }
    echo "\n";
    echo $help_msg;
    echo "\n\n";
    exit(1);
}

for ($i = 1; $i < $argc; $i++) {
    $arg = trim($argv[$i]);
    if ($arg === "-e") {
        $e_option_present = TRUE;
        $op = "encrypt";
    } else if ($arg === "-d") {
        $d_option_present = TRUE;
        $op = "decrypt";
    } else {
        $input_file = $arg;
    }
} // end of for loop

if (($e_option_present == FALSE) && ($d_option_present == FALSE)) {
    echo "Error: Neither '-e' option nor '-d' option is given." .
         " This is invalid. One of the options should be given. Exiting..\n";
    echo "\n";
    echo $help_msg;
    echo "\n\n";
    exit(1);
}

if (($e_option_present == TRUE) && ($d_option_present == TRUE)) {
    echo "Error: Both '-e' option and '-d' option are given." .
         " This is invalid. Only one option should be given. Exiting..\n";
    echo "\n";
    echo $help_msg;
    echo "\n\n";
    exit(1);
}

if (strlen($input_file) == 0) {
    echo "Error: Input file name is empty. Exiting..\n";
    echo "\n";
    echo $help_msg;
    echo "\n\n";
    exit(1);
}

// set output file name
$op_str = $op . "ed";
$output_file = $input_file . "." . $op_str;

//print_debug_info();

// print names of input file and output file
echo "Input file: $input_file\n";
echo "Output file (to be created): $output_file\n\n";

// check if output file already exists by trying to read it
$op_str = $op . "ion";
$op_str = ucfirst($op_str);
if (($out_handle = fopen($output_file, "r")) != FALSE) { // output file exists
    fclose($out_handle);
    echo "\n";
    echo "Error: Output file already exists. $op_str was not done." .
         " Exiting..\n\n";
    exit(1);
}

// open input file for reading
if (($in_handle = fopen($input_file, "rb")) == FALSE) {
    echo "\n";
    echo "Error: Failed to open input file for reading. $op_str was not done." .
         " Exiting..\n\n";
    exit(1);
}

// get password from user
$op_str = $op . "ing";
while (strlen($password) == 0) {

    echo "Please enter password for $op_str input file" .
         " (max. $max_password_len characters): ";

    if (($password = fread(STDIN, $max_password_len)) == FALSE) {
        echo "Error: Failed to read password entered by the user on standard" .
             " input (STDIN). Exiting..\n\n";
        fclose($in_handle);
        exit(1);
    }

    // remove \r and \n from password
    $password = str_replace("\r", "", $password);
    $password = str_replace("\n", "", $password);
    $actual_password_len = strlen($password);
    //var_dump($password);

} // end of while strlen password

// open output file for writing
if (($out_handle = fopen($output_file, "wb")) == FALSE) {
    echo "\n";
    echo "Error: Failed to open output file for writing. $op_str was not" .
         " done. Exiting..\n\n";
    fclose($in_handle);
    exit(1);
}

while (!feof($in_handle)) {

//testing
//echo "Press enter to resume testing: ";
//fread(STDIN, 20);

    if (($buf = fread($in_handle, $buf_size)) == FALSE) {
        echo "\n";
        echo "Error: Failed to read input file. $op_str was not done." .
             " Exiting..\n\n";
        close_file_handles();
        delete_output_file();
        echo "\n";
        exit(1);
    }

    $buf_len = strlen($buf);

    for ($bi = 0, $pi = 0;
         $bi < $buf_len;
         $bi++, $pi = (($pi + 1) % $actual_password_len)) {
            //echo "$buf[$bi], ";
            //echo "$password[$pi], ";
            $buf[$bi] = ($buf[$bi] ^ $password[$pi]) ^ chr(0x80);
            //echo "$buf[$bi]\n";
            //print_r(unpack("H*", $buf[$bi]));
        } // end of for loop

//testing
//echo "Press enter to resume testing: ";
//fread(STDIN, 20);

    if (($num_bytes_written = fwrite($out_handle, $buf, $buf_len)) == FALSE) {
        echo "\n";
        echo "Error: Failed to write to output file. $op_str was not done." .
             " Exiting..\n\n";
        close_file_handles();
        delete_output_file();
        echo "\n";
        exit(1);
    }

//testing
//$num_bytes_written = 1234;
//echo "Press enter to resume testing: ";
//fread(STDIN, 20);

    if ($num_bytes_written != $buf_len) {
        echo "\n";
        echo "Error: Number of bytes read from the input file are not equal" .
             " to the number of bytes written to the output file. Output file" .
             " is corrupted. Deleting output file and exiting..\n";
        close_file_handles();
        delete_output_file();
        echo "\n";
        exit(1);
    }

} // end of while !feof

$op_str = $op . "ed";
echo "\n";
echo "Input file was $op_str successfully.\n\n";

echo "Output file was created successfully and is ready.\n\n";

close_file_handles()

?>

----

Powered by blists - more mailing lists