ParagonIE_Sodium_File::secretbox_decrypt_core32() protected WP 1.0

Decrypt a file (32-bit)

{} It's a method of the class: ParagonIE_Sodium_File{}

No Hooks.

Return

true|false.

Usage

$result = ParagonIE_Sodium_File::secretbox_decrypt_core32( $ifp, $ofp, $mlen, $nonce, $key );

$ifp(resource) (required)

-

$ofp(resource) (required)

-

$mlen(int) (required)

-

$nonce(string) (required)

-

$key(string) (required)

-

Code of ParagonIE_Sodium_File::secretbox_decrypt_core32() ParagonIE Sodium File::secretbox decrypt core32 ^{WP 5.8.2}

protected static function secretbox_decrypt_core32($ifp, $ofp, $mlen, $nonce, $key)
{
    $tag = fread($ifp, 16);
    if (!is_string($tag)) {
        throw new SodiumException('Could not read input file');
    }

    /** @var string $subkey */
    $subkey = ParagonIE_Sodium_Core32_HSalsa20::hsalsa20($nonce, $key);

    /** @var string $realNonce */
    $realNonce = ParagonIE_Sodium_Core32_Util::substr($nonce, 16, 8);

    /** @var string $block0 */
    $block0 = ParagonIE_Sodium_Core32_Salsa20::salsa20(
        64,
        ParagonIE_Sodium_Core32_Util::substr($nonce, 16, 8),
        $subkey
    );

    /* Verify the Poly1305 MAC -before- attempting to decrypt! */
    $state = new ParagonIE_Sodium_Core32_Poly1305_State(self::substr($block0, 0, 32));
    if (!self::onetimeauth_verify_core32($state, $ifp, $tag, $mlen)) {
        throw new SodiumException('Invalid MAC');
    }

    /*
     * Set the cursor to the end of the first half-block. All future bytes will
     * generated from salsa20_xor_ic, starting from 1 (second block).
     */
    $first32 = fread($ifp, 32);
    if (!is_string($first32)) {
        throw new SodiumException('Could not read input file');
    }
    $first32len = self::strlen($first32);
    fwrite(
        $ofp,
        self::xorStrings(
            self::substr($block0, 32, $first32len),
            self::substr($first32, 0, $first32len)
        )
    );
    $mlen -= 32;

    /** @var int $iter */
    $iter = 1;

    /** @var int $incr */
    $incr = self::BUFFER_SIZE >> 6;

    /* Decrypts ciphertext, writes to output file. */
    while ($mlen > 0) {
        $blockSize = $mlen > self::BUFFER_SIZE
            ? self::BUFFER_SIZE
            : $mlen;
        $ciphertext = fread($ifp, $blockSize);
        if (!is_string($ciphertext)) {
            throw new SodiumException('Could not read input file');
        }
        $pBlock = ParagonIE_Sodium_Core32_Salsa20::salsa20_xor_ic(
            $ciphertext,
            $realNonce,
            $iter,
            $subkey
        );
        fwrite($ofp, $pBlock, $blockSize);
        $mlen -= $blockSize;
        $iter += $incr;
    }
    return true;
}