Fix charset conversion errors on PHP < 8 for charsets not supported by mbstring (#8252)

3 files changed, 12 insertions, 4 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c3aa2f26a..b0f8038c1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -39,6 +39,7 @@
 - Fix regression in setting of contact listing name (#8260)
 - Fix bug in Larry skin where headers toggle state was reset on full page preview (#8203)
 - Fix bug where \u200b characters were added into the recipient input preventing mail delivery (#8269)
+- Fix charset conversion errors on PHP < 8 for charsets not supported by mbstring (#8252)
 
 ## Release 1.5.0
 
diff --git a/program/lib/Roundcube/rcube_charset.php b/program/lib/Roundcube/rcube_charset.php
index b0b68136e..e0a2db0cd 100644
--- a/program/lib/Roundcube/rcube_charset.php
+++ b/program/lib/Roundcube/rcube_charset.php
@@ -281,7 +281,7 @@ class rcube_charset
         }
 
         $out = false;
-        $error_handler = function() use ($out) { $out = false; };
+        $error_handler = function() { throw new \Exception(); };
 
         // Ignore invalid characters
         $mbstring_sc = mb_substitute_character();
@@ -328,10 +328,14 @@ class rcube_charset
             // If iconv reports an illegal character in input it means that input string
             // has been truncated. It's reported as E_NOTICE.
             // PHP8 will also throw E_WARNING on unsupported encoding.
-            set_error_handler($error_handler, E_NOTICE);
-            set_error_handler($error_handler, E_WARNING);
+            set_error_handler($error_handler, E_NOTICE | E_WARNING);
 
-            $out = iconv($from, $to . $iconv_options, $str);
+            try {
+                $out = iconv($from, $to . $iconv_options, $str);
+            }
+            catch (Throwable $e) {
+                $out = false;
+            }
 
             restore_error_handler();
 
diff --git a/tests/Framework/Charset.php b/tests/Framework/Charset.php
index 1284a2fae..38e217c2e 100644
--- a/tests/Framework/Charset.php
+++ b/tests/Framework/Charset.php
@@ -72,6 +72,9 @@ class Framework_Charset extends PHPUnit\Framework\TestCase
         if (extension_loaded('iconv')) {
             // Windows-1253 is not supported by mbstring, we're testing fallback to iconv
             $data[] = ['ε', chr(hexdec(('E5'))), 'UTF-8', 'WINDOWS-1253'];
+            // Windows-874 is also not supported by mbstring
+            $in = quoted_printable_decode('=B5=CD=BA=A1=C5=D1=BA');
+            $data[] = [$in, 'ตอบกลับ', 'WINDOWS-874', 'UTF-8'];
         }
 
         return $data;