218 lines
8.0 KiB
PHP
218 lines
8.0 KiB
PHP
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<?php
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/*
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* This file is part of the Symfony package.
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*
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* (c) Fabien Potencier <fabien@symfony.com>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Symfony\Component\Mime\Crypto;
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use Symfony\Component\Mime\Exception\InvalidArgumentException;
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use Symfony\Component\Mime\Exception\RuntimeException;
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use Symfony\Component\Mime\Header\UnstructuredHeader;
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use Symfony\Component\Mime\Message;
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use Symfony\Component\Mime\Part\AbstractPart;
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/**
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* @author Fabien Potencier <fabien@symfony.com>
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*
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* RFC 6376 and 8301
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*/
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final class DkimSigner
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{
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public const CANON_SIMPLE = 'simple';
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public const CANON_RELAXED = 'relaxed';
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public const ALGO_SHA256 = 'rsa-sha256';
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public const ALGO_ED25519 = 'ed25519-sha256'; // RFC 8463
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private \OpenSSLAsymmetricKey $key;
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private string $domainName;
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private string $selector;
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private array $defaultOptions;
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/**
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* @param string $pk The private key as a string or the path to the file containing the private key, should be prefixed with file:// (in PEM format)
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* @param string $passphrase A passphrase of the private key (if any)
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*/
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public function __construct(string $pk, string $domainName, string $selector, array $defaultOptions = [], string $passphrase = '')
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{
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if (!\extension_loaded('openssl')) {
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throw new \LogicException('PHP extension "openssl" is required to use DKIM.');
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}
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$this->key = openssl_pkey_get_private($pk, $passphrase) ?: throw new InvalidArgumentException('Unable to load DKIM private key: '.openssl_error_string());
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$this->domainName = $domainName;
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$this->selector = $selector;
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$this->defaultOptions = $defaultOptions + [
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'algorithm' => self::ALGO_SHA256,
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'signature_expiration_delay' => 0,
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'body_max_length' => \PHP_INT_MAX,
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'body_show_length' => false,
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'header_canon' => self::CANON_RELAXED,
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'body_canon' => self::CANON_RELAXED,
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'headers_to_ignore' => [],
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];
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}
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public function sign(Message $message, array $options = []): Message
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{
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$options += $this->defaultOptions;
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if (!\in_array($options['algorithm'], [self::ALGO_SHA256, self::ALGO_ED25519], true)) {
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throw new InvalidArgumentException(sprintf('Invalid DKIM signing algorithm "%s".', $options['algorithm']));
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}
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$headersToIgnore['return-path'] = true;
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$headersToIgnore['x-transport'] = true;
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foreach ($options['headers_to_ignore'] as $name) {
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$headersToIgnore[strtolower($name)] = true;
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}
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unset($headersToIgnore['from']);
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$signedHeaderNames = [];
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$headerCanonData = '';
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$headers = $message->getPreparedHeaders();
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foreach ($headers->getNames() as $name) {
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foreach ($headers->all($name) as $header) {
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if (isset($headersToIgnore[strtolower($header->getName())])) {
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continue;
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}
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if ('' !== $header->getBodyAsString()) {
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$headerCanonData .= $this->canonicalizeHeader($header->toString(), $options['header_canon']);
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$signedHeaderNames[] = $header->getName();
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}
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}
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}
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[$bodyHash, $bodyLength] = $this->hashBody($message->getBody(), $options['body_canon'], $options['body_max_length']);
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$params = [
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'v' => '1',
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'q' => 'dns/txt',
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'a' => $options['algorithm'],
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'bh' => base64_encode($bodyHash),
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'd' => $this->domainName,
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'h' => implode(': ', $signedHeaderNames),
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'i' => '@'.$this->domainName,
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's' => $this->selector,
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't' => time(),
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'c' => $options['header_canon'].'/'.$options['body_canon'],
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];
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if ($options['body_show_length']) {
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$params['l'] = $bodyLength;
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}
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if ($options['signature_expiration_delay']) {
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$params['x'] = $params['t'] + $options['signature_expiration_delay'];
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}
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$value = '';
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foreach ($params as $k => $v) {
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$value .= $k.'='.$v.'; ';
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}
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$value = trim($value);
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$header = new UnstructuredHeader('DKIM-Signature', $value);
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$headerCanonData .= rtrim($this->canonicalizeHeader($header->toString()."\r\n b=", $options['header_canon']));
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if (self::ALGO_SHA256 === $options['algorithm']) {
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if (!openssl_sign($headerCanonData, $signature, $this->key, \OPENSSL_ALGO_SHA256)) {
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throw new RuntimeException('Unable to sign DKIM hash: '.openssl_error_string());
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}
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} else {
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throw new \RuntimeException(sprintf('The "%s" DKIM signing algorithm is not supported yet.', self::ALGO_ED25519));
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}
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$header->setValue($value.' b='.trim(chunk_split(base64_encode($signature), 73, ' ')));
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$headers->add($header);
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return new Message($headers, $message->getBody());
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}
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private function canonicalizeHeader(string $header, string $headerCanon): string
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{
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if (self::CANON_RELAXED !== $headerCanon) {
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return $header."\r\n";
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}
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$exploded = explode(':', $header, 2);
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$name = strtolower(trim($exploded[0]));
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$value = str_replace("\r\n", '', $exploded[1]);
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$value = trim(preg_replace("/[ \t][ \t]+/", ' ', $value));
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return $name.':'.$value."\r\n";
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}
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private function hashBody(AbstractPart $body, string $bodyCanon, int $maxLength): array
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{
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$hash = hash_init('sha256');
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$relaxed = self::CANON_RELAXED === $bodyCanon;
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$currentLine = '';
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$emptyCounter = 0;
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$isSpaceSequence = false;
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$length = 0;
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foreach ($body->bodyToIterable() as $chunk) {
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$canon = '';
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for ($i = 0, $len = \strlen($chunk); $i < $len; ++$i) {
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switch ($chunk[$i]) {
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case "\r":
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break;
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case "\n":
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// previous char is always \r
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if ($relaxed) {
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$isSpaceSequence = false;
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}
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if ('' === $currentLine) {
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++$emptyCounter;
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} else {
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$currentLine = '';
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$canon .= "\r\n";
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}
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break;
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case ' ':
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case "\t":
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if ($relaxed) {
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$isSpaceSequence = true;
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break;
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}
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// no break
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default:
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if ($emptyCounter > 0) {
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$canon .= str_repeat("\r\n", $emptyCounter);
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$emptyCounter = 0;
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}
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if ($isSpaceSequence) {
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$currentLine .= ' ';
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$canon .= ' ';
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$isSpaceSequence = false;
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}
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$currentLine .= $chunk[$i];
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$canon .= $chunk[$i];
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}
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}
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if ($length + \strlen($canon) >= $maxLength) {
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$canon = substr($canon, 0, $maxLength - $length);
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$length += \strlen($canon);
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hash_update($hash, $canon);
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break;
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}
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$length += \strlen($canon);
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hash_update($hash, $canon);
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}
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// Add trailing Line return if last line is non empty
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if ('' !== $currentLine) {
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hash_update($hash, "\r\n");
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$length += \strlen("\r\n");
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}
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if (!$relaxed && 0 === $length) {
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hash_update($hash, "\r\n");
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$length = 2;
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}
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return [hash_final($hash, true), $length];
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}
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}
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