1<?php
  2
  3if (class_exists('ParagonIE_Sodium_Core_ChaCha20_Ctx', false)) {
  4    return;
  5}
  6
  7/**
  8 * Class ParagonIE_Sodium_Core32_ChaCha20_Ctx
  9 */
 10class ParagonIE_Sodium_Core32_ChaCha20_Ctx extends ParagonIE_Sodium_Core32_Util implements ArrayAccess
 11{
 12    /**
 13     * @var SplFixedArray internally, <int, ParagonIE_Sodium_Core32_Int32>
 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 $counter The initial counter value.
 25     *                        Defaults to 8 0x00 bytes.
 26     * @throws InvalidArgumentException
 27     * @throws SodiumException
 28     * @throws TypeError
 29     */
 30    public function __construct($key = '', $iv = '', $counter = '')
 31    {
 32        if (self::strlen($key) !== 32) {
 33            throw new InvalidArgumentException('ChaCha20 expects a 256-bit key.');
 34        }
 35        if (self::strlen($iv) !== 8) {
 36            throw new InvalidArgumentException('ChaCha20 expects a 64-bit nonce.');
 37        }
 38        $this->container = new SplFixedArray(16);
 39
 40        /* "expand 32-byte k" as per ChaCha20 spec */
 41        $this->container[0]  = new ParagonIE_Sodium_Core32_Int32(array(0x6170, 0x7865));
 42        $this->container[1]  = new ParagonIE_Sodium_Core32_Int32(array(0x3320, 0x646e));
 43        $this->container[2]  = new ParagonIE_Sodium_Core32_Int32(array(0x7962, 0x2d32));
 44        $this->container[3]  = new ParagonIE_Sodium_Core32_Int32(array(0x6b20, 0x6574));
 45
 46        $this->container[4]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 0, 4));
 47        $this->container[5]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 4, 4));
 48        $this->container[6]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 8, 4));
 49        $this->container[7]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 12, 4));
 50        $this->container[8]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 16, 4));
 51        $this->container[9]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 20, 4));
 52        $this->container[10] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 24, 4));
 53        $this->container[11] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 28, 4));
 54
 55        if (empty($counter)) {
 56            $this->container[12] = new ParagonIE_Sodium_Core32_Int32();
 57            $this->container[13] = new ParagonIE_Sodium_Core32_Int32();
 58        } else {
 59            $this->container[12] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($counter, 0, 4));
 60            $this->container[13] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($counter, 4, 4));
 61        }
 62        $this->container[14] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($iv, 0, 4));
 63        $this->container[15] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($iv, 4, 4));
 64    }
 65
 66    /**
 67     * @internal You should not use this directly from another application
 68     *
 69     * @param int $offset
 70     * @param int|ParagonIE_Sodium_Core32_Int32 $value
 71     * @return void
 72     */
 73    #[ReturnTypeWillChange]
 74    public function offsetSet($offset, $value)
 75    {
 76        if (!is_int($offset)) {
 77            throw new InvalidArgumentException('Expected an integer');
 78        }
 79        if ($value instanceof ParagonIE_Sodium_Core32_Int32) {
 80            /*
 81        } elseif (is_int($value)) {
 82            $value = ParagonIE_Sodium_Core32_Int32::fromInt($value);
 83            */
 84        } else {
 85            throw new InvalidArgumentException('Expected an integer');
 86        }
 87        $this->container[$offset] = $value;
 88    }
 89
 90    /**
 91     * @internal You should not use this directly from another application
 92     *
 93     * @param int $offset
 94     * @return bool
 95     * @psalm-suppress MixedArrayOffset
 96     */
 97    #[ReturnTypeWillChange]
 98    public function offsetExists($offset)
 99    {
100        return isset($this->container[$offset]);
101    }
102
103    /**
104     * @internal You should not use this directly from another application
105     *
106     * @param int $offset
107     * @return void
108     * @psalm-suppress MixedArrayOffset
109     */
110    #[ReturnTypeWillChange]
111    public function offsetUnset($offset)
112    {
113        unset($this->container[$offset]);
114    }
115
116    /**
117     * @internal You should not use this directly from another application
118     *
119     * @param int $offset
120     * @return mixed|null
121     * @psalm-suppress MixedArrayOffset
122     */
123    #[ReturnTypeWillChange]
124    public function offsetGet($offset)
125    {
126        return isset($this->container[$offset])
127            ? $this->container[$offset]
128            : null;
129    }
130}
131