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[ticket/16912] Rewrite email headers encoding method

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Based on symfony/polyfill-iconv implementations.

PHPBB3-16912
This commit is contained in:
rxu 2021-11-23 15:12:43 +07:00
parent 6e34e3c24e
commit 0537365cac
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GPG Key ID: 14C89C9F50DA21E6
1 changed files with 58 additions and 40 deletions
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98
phpBB/includes/functions_messenger.php
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@ -1840,66 +1840,84 @@ class smtp_class
}
/**
* Encodes the given string for proper display in UTF-8.
*
* This version is using base64 encoded data. The downside of this
* is if the mail client does not understand this encoding the user
* is basically doomed with an unreadable subject.
*
* Please note that this version fully supports RFC 2045 section 6.8.
*
* @param string $str
* @param string $eol End of line we are using (optional to be backwards compatible)
*/
* Encodes the given string for proper display in UTF-8 or US-ASCII.
*
* This version is based on iconv_mime_encode() implementation
* from symfomy/polyfill-iconv
* https://github.com/symfony/polyfill-iconv/blob/fd324208ec59a39ebe776e6e9ec5540ad4f40aaa/Iconv.php#L355
*
* @param string $str
* @param string $eol End of line we are using (optional to be backwards compatible)
*
* @return string
*/
function mail_encode($str, $eol = "\r\n")
{
// Check if string contains ASCII only characters
$is_ascii = strlen($str) === utf8_strlen($str);
// Define start delimimter, end delimiter and spacer
$scheme = $is_ascii ? "Q" : "B";
// Define start delimimter, end delimiter
// Use the Quoted-Printable encoding for ASCII strings to avoid unnecessary encoding in Base64
$start = $is_ascii ? "=?US-ASCII?Q?" : "=?UTF-8?B?";
$start = $is_ascii ? "=?US-ASCII?$scheme?" : "=?UTF-8?$scheme?";
$end = "?=";
$delimiter = "$eol ";
// Maximum encoded-word length is 75 as per RFC 2047 section 2.
// $split_length *must* be a multiple of 4, but <= 75 - strlen($start . $delimiter . $end)!!!
$split_length = 75 - strlen($start . $delimiter . $end);
$split_length = 75 - strlen($start . $eol . $end);
$split_length = $split_length - $split_length % 4;
// Use the Quoted-Printable encoding for ASCII strings to avoid unnecessary encoding in Base64
// quoted_printable_encode() splits lines at length of 75 characters with =\r\n delimiter, amend this feature
$encoded_str = $is_ascii ? str_replace("=\r\n", '', quoted_printable_encode($str)) : base64_encode($str);
$line_length = \strlen($start) + \strlen($end);
$line_offset = \strlen($start) + 1;
$line_data = '';
// If encoded string meets the limits, we just return with the correct data.
if (strlen($encoded_str) <= $split_length)
$is_quoted_printable = 'Q' === $scheme;
preg_match_all('/./us', $str, $chars);
$chars = $chars[0] ?? [];
$str = [];
foreach ($chars as $char)
{
return $start . $encoded_str . $end;
}
$encoded_char = $is_quoted_printable
? $char = preg_replace_callback(
'/[=_\?\x20\x00-\x1F\x80-\xFF]/',
function ($matches)
{
$hex = dechex(\ord($matches[0]));
$hex = strlen($hex) == 1 ? "0$hex" : $hex;
return '=' . strtoupper($hex);
},
$char
)
: base64_encode($line_data . $char);
// If there is only ASCII data, we just return what we want, correctly splitting the lines.
if ($is_ascii)
{
return $start . implode($end . $delimiter . $start, str_split($encoded_str, $split_length)) . $end;
}
// UTF-8 data, compose encoded lines
$array = utf8_str_split($str);
$str = '';
while (count($array))
{
$text = '';
while (count($array) && intval((strlen($text . $array[0]) + 2) / 3) << 2 <= $split_length)
if (isset($encoded_char[$split_length - $line_length]))
{
$text .= array_shift($array);
if (!$is_quoted_printable)
{
$line_data = base64_encode($line_data);
}
$str[] = $start . $line_data . $end;
$line_length = $line_offset;
$line_data = '';
}
$str .= $start . base64_encode($text) . $end . $delimiter;
$line_data .= $char;
$is_quoted_printable && $line_length += \strlen($char);
}
return substr($str, 0, -strlen($delimiter));
if ('' !== $line_data)
{
if (!$is_quoted_printable)
{
$line_data = base64_encode($line_data);
}
$str[] = $start . $line_data . $end;
}
return implode($eol . ' ', $str);
}
/**