59 lines
1.5 KiB
PHP
59 lines
1.5 KiB
PHP
<?php
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namespace PhpOffice\PhpSpreadsheet\Reader\Xls;
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class RC4
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{
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/** @var int[] */
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protected array $s = []; // Context
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protected int $i = 0;
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protected int $j = 0;
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/**
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* RC4 stream decryption/encryption constrcutor.
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*
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* @param string $key Encryption key/passphrase
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*/
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public function __construct(string $key)
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{
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$len = strlen($key);
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for ($this->i = 0; $this->i < 256; ++$this->i) {
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$this->s[$this->i] = $this->i;
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}
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$this->j = 0;
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for ($this->i = 0; $this->i < 256; ++$this->i) {
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$this->j = ($this->j + $this->s[$this->i] + ord($key[$this->i % $len])) % 256;
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$t = $this->s[$this->i];
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$this->s[$this->i] = $this->s[$this->j];
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$this->s[$this->j] = $t;
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}
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$this->i = $this->j = 0;
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}
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/**
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* Symmetric decryption/encryption function.
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*
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* @param string $data Data to encrypt/decrypt
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*/
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public function RC4(string $data): string
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{
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$len = strlen($data);
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for ($c = 0; $c < $len; ++$c) {
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$this->i = ($this->i + 1) % 256;
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$this->j = ($this->j + $this->s[$this->i]) % 256;
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$t = $this->s[$this->i];
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$this->s[$this->i] = $this->s[$this->j];
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$this->s[$this->j] = $t;
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$t = ($this->s[$this->i] + $this->s[$this->j]) % 256;
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$data[$c] = chr(ord($data[$c]) ^ $this->s[$t]);
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}
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return $data;
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}
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}
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