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author | Chris Cannam |
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date | Wed, 28 Aug 2019 13:14:47 +0100 |
parents | 129ea1e6d783 |
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<?php namespace Drupal\Component\Utility; /** * Provides helpers to ensure emails are compliant with RFCs. * * @ingroup utility */ class Mail { /** * RFC-2822 "specials" characters. */ const RFC_2822_SPECIALS = '()<>[]:;@\,."'; /** * Return a RFC-2822 compliant "display-name" component. * * The "display-name" component is used in mail header "Originator" fields * (From, Sender, Reply-to) to give a human-friendly description of the * address, i.e. From: My Display Name <xyz@example.org>. RFC-822 and * RFC-2822 define its syntax and rules. This method gets as input a string * to be used as "display-name" and formats it to be RFC compliant. * * @param string $string * A string to be used as "display-name". * * @return string * A RFC compliant version of the string, ready to be used as * "display-name" in mail originator header fields. */ public static function formatDisplayName($string) { // Make sure we don't process html-encoded characters. They may create // unneeded trouble if left encoded, besides they will be correctly // processed if decoded. $string = Html::decodeEntities($string); // If string contains non-ASCII characters it must be (short) encoded // according to RFC-2047. The output of a "B" (Base64) encoded-word is // always safe to be used as display-name. $safe_display_name = Unicode::mimeHeaderEncode($string, TRUE); // Encoded-words are always safe to be used as display-name because don't // contain any RFC 2822 "specials" characters. However // Unicode::mimeHeaderEncode() encodes a string only if it contains any // non-ASCII characters, and leaves its value untouched (un-encoded) if // ASCII only. For this reason in order to produce a valid display-name we // still need to make sure there are no "specials" characters left. if (preg_match('/[' . preg_quote(Mail::RFC_2822_SPECIALS) . ']/', $safe_display_name)) { // If string is already quoted, it may or may not be escaped properly, so // don't trust it and reset. if (preg_match('/^"(.+)"$/', $safe_display_name, $matches)) { $safe_display_name = str_replace(['\\\\', '\\"'], ['\\', '"'], $matches[1]); } // Transform the string in a RFC-2822 "quoted-string" by wrapping it in // double-quotes. Also make sure '"' and '\' occurrences are escaped. $safe_display_name = '"' . str_replace(['\\', '"'], ['\\\\', '\\"'], $safe_display_name) . '"'; } return $safe_display_name; } }