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   1  <?php
   2  
   3  if (class_exists('ParagonIE_Sodium_Core_ChaCha20_Ctx', false)) {
   4      return;
   5  }
   6  
   7  /**
   8   * Class ParagonIE_Sodium_Core_ChaCha20_Ctx
   9   */
  10  class ParagonIE_Sodium_Core_ChaCha20_Ctx extends ParagonIE_Sodium_Core_Util implements ArrayAccess
  11  {
  12      /**
  13       * @var SplFixedArray internally, <int, int>
  14       */
  15      protected $container;
  16  
  17      /**
  18       * ParagonIE_Sodium_Core_ChaCha20_Ctx constructor.
  19       *
  20       * @internal You should not use this directly from another application
  21       *
  22       * @param string $key     ChaCha20 key.
  23       * @param string $iv      Initialization Vector (a.k.a. nonce).
  24       * @param string $counter The initial counter value.
  25       *                        Defaults to 8 0x00 bytes.
  26       * @throws InvalidArgumentException
  27       * @throws TypeError
  28       */
  29      public function __construct($key = '', $iv = '', $counter = '')
  30      {
  31          if (self::strlen($key) !== 32) {
  32              throw new InvalidArgumentException('ChaCha20 expects a 256-bit key.');
  33          }
  34          if (self::strlen($iv) !== 8) {
  35              throw new InvalidArgumentException('ChaCha20 expects a 64-bit nonce.');
  36          }
  37          $this->container = new SplFixedArray(16);
  38  
  39          /* "expand 32-byte k" as per ChaCha20 spec */
  40          $this->container[0]  = 0x61707865;
  41          $this->container[1]  = 0x3320646e;
  42          $this->container[2]  = 0x79622d32;
  43          $this->container[3]  = 0x6b206574;
  44          $this->container[4]  = self::load_4(self::substr($key, 0, 4));
  45          $this->container[5]  = self::load_4(self::substr($key, 4, 4));
  46          $this->container[6]  = self::load_4(self::substr($key, 8, 4));
  47          $this->container[7]  = self::load_4(self::substr($key, 12, 4));
  48          $this->container[8]  = self::load_4(self::substr($key, 16, 4));
  49          $this->container[9]  = self::load_4(self::substr($key, 20, 4));
  50          $this->container[10] = self::load_4(self::substr($key, 24, 4));
  51          $this->container[11] = self::load_4(self::substr($key, 28, 4));
  52  
  53          $counter = $this->initCounter($counter);
  54          $this->container[12] = self::load_4(self::substr($counter, 0, 4));
  55          $this->container[13] = self::load_4(self::substr($counter, 4, 4));
  56          $this->container[14] = self::load_4(self::substr($iv, 0, 4));
  57          $this->container[15] = self::load_4(self::substr($iv, 4, 4));
  58      }
  59  
  60      /**
  61       * @internal You should not use this directly from another application
  62       *
  63       * @param int $offset
  64       * @param int $value
  65       * @return void
  66       * @psalm-suppress MixedArrayOffset
  67       */
  68      #[ReturnTypeWillChange]
  69      public function offsetSet($offset, $value)
  70      {
  71          if (!is_int($offset)) {
  72              throw new InvalidArgumentException('Expected an integer');
  73          }
  74          if (!is_int($value)) {
  75              throw new InvalidArgumentException('Expected an integer');
  76          }
  77          $this->container[$offset] = $value;
  78      }
  79  
  80      /**
  81       * @internal You should not use this directly from another application
  82       *
  83       * @param int $offset
  84       * @return bool
  85       */
  86      #[ReturnTypeWillChange]
  87      public function offsetExists($offset)
  88      {
  89          return isset($this->container[$offset]);
  90      }
  91  
  92      /**
  93       * @internal You should not use this directly from another application
  94       *
  95       * @param int $offset
  96       * @return void
  97       * @psalm-suppress MixedArrayOffset
  98       */
  99      #[ReturnTypeWillChange]
 100      public function offsetUnset($offset)
 101      {
 102          unset($this->container[$offset]);
 103      }
 104  
 105      /**
 106       * @internal You should not use this directly from another application
 107       *
 108       * @param int $offset
 109       * @return mixed|null
 110       * @psalm-suppress MixedArrayOffset
 111       */
 112      #[ReturnTypeWillChange]
 113      public function offsetGet($offset)
 114      {
 115          return isset($this->container[$offset])
 116              ? $this->container[$offset]
 117              : null;
 118      }
 119  
 120      /**
 121       * Initialize (pad) a counter value.
 122       * @throws SodiumException
 123       *
 124       * @param string $ctr
 125       * @return string
 126       */
 127      public function initCounter(
 128          #[SensitiveParameter]
 129          $ctr
 130      ) {
 131          $len = self::strlen($ctr);
 132          if ($len === 0) {
 133              return str_repeat("\0", 8);
 134          }
 135          if ($len < 8) {
 136              return $ctr . str_repeat("\0", 8 - $len);
 137          }
 138          if ($len > 8) {
 139              throw new SodiumException("counter cannot be more than 8 bytes");
 140          }
 141          return $ctr;
 142      }
 143  }