Fix #80933: SplFileObject::DROP_NEW_LINE is broken for NUL and CR

`buf` may contain NUL bytes, so we must not use `strcspn()` but rather
a binary safe variant.  However, we also must not detect a stray CR as
line ending, and since we only need to check line endings at the end
of the buffer, we can nicely optimize.

Co-authored-by: Nikita Popov <nikita.ppv@gmail.com>

Closes GH-6836.

Author: cmb69

NEWS

@@ -2,7 +2,9 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 7.4.19
 
-
+- SPL:
+  . Fixed bug #80933 (SplFileObject::DROP_NEW_LINE is broken for NUL and CR).
+    (cmb, Nikita)
 
 29 Apr 2021, PHP 7.4.18
 

ext/spl/spl_directory.c

@@ -2046,8 +2046,13 @@ static int spl_filesystem_file_read(spl_filesystem_object *intern, int silent) /
 		intern->u.file.current_line_len = 0;
 	} else {
 		if (SPL_HAS_FLAG(intern->flags, SPL_FILE_OBJECT_DROP_NEW_LINE)) {
-			line_len = strcspn(buf, "\r\n");
-			buf[line_len] = '\0';
+			if (line_len > 0 && buf[line_len - 1] == '\n') {
+				line_len--;
+				if (line_len > 0 && buf[line_len - 1] == '\r') {
+					line_len--;
+				}
+				buf[line_len] = '\0';
+			}
 		}
 
 		intern->u.file.current_line = buf;

ext/spl/tests/bug80933.phpt

@@ -0,0 +1,27 @@
+--TEST--
+Bug #80933 (SplFileObject::DROP_NEW_LINE is broken for NUL and CR)
+--FILE--
+<?php
+$lines = [
+    "Lorem ipsum \0 dolor sit amet", // string with NUL
+    "Lorem ipsum \r dolor sit amet", // string with CR
+];
+foreach ($lines as $line) {
+    $temp = new SplTempFileObject();
+    $temp->fwrite($line);
+
+    $temp->rewind();
+    $read = $temp->fgets();
+    var_dump($line === $read);
+
+    $temp->rewind();
+    $temp->setFlags(SplFileObject::DROP_NEW_LINE);
+    $read = $temp->fgets();
+    var_dump($line === $read);
+}
+?>
+--EXPECT--
+bool(true)
+bool(true)
+bool(true)
+bool(true)