Fix GH-19480: error_log php.ini cannot be unset when open_basedir is configured

Since the ini message handlers already check for basedir, we need to
drop the basedir check from ini_set. Then we also fix the exceptional
case for the empty string: it should bypass the basedir check.
Furthermore, there was a regression introduced with the error_log
"syslog" check in ddfe269 (inverted check), so we fix that as well.

Author: nielsdos

ext/standard/basic_functions.c

@@ -2037,10 +2037,8 @@ PHP_FUNCTION(ini_set)
 #define _CHECK_PATH(var, var_len, ini) php_ini_check_path(var, var_len, ini, sizeof(ini))
 	/* open basedir check */
 	if (PG(open_basedir)) {
-		if (_CHECK_PATH(ZSTR_VAL(varname), ZSTR_LEN(varname), "error_log") ||
-			_CHECK_PATH(ZSTR_VAL(varname), ZSTR_LEN(varname), "java.class.path") ||
+		if (_CHECK_PATH(ZSTR_VAL(varname), ZSTR_LEN(varname), "java.class.path") ||
 			_CHECK_PATH(ZSTR_VAL(varname), ZSTR_LEN(varname), "java.home") ||
-			_CHECK_PATH(ZSTR_VAL(varname), ZSTR_LEN(varname), "mail.log") ||
 			_CHECK_PATH(ZSTR_VAL(varname), ZSTR_LEN(varname), "java.library.path") ||
 			_CHECK_PATH(ZSTR_VAL(varname), ZSTR_LEN(varname), "vpopmail.directory")) {
 			if (php_check_open_basedir(ZSTR_VAL(new_value_str))) {

main/main.c

@@ -625,26 +625,28 @@ static PHP_INI_MH(OnUpdateErrorLog)
 {
 	/* Only do the safemode/open_basedir check at runtime */
 	if ((stage == PHP_INI_STAGE_RUNTIME || stage == PHP_INI_STAGE_HTACCESS) &&
-			new_value && zend_string_equals_literal(new_value, "syslog")) {
+			new_value && !zend_string_equals_literal(new_value, "syslog") && ZSTR_LEN(new_value) > 0) {
 		if (PG(open_basedir) && php_check_open_basedir(ZSTR_VAL(new_value))) {
 			return FAILURE;
 		}
 	}
-	OnUpdateString(entry, new_value, mh_arg1, mh_arg2, mh_arg3, stage);
+	char **p = (char **) ZEND_INI_GET_ADDR();
+	*p = new_value && ZSTR_LEN(new_value) > 0 ? ZSTR_VAL(new_value) : NULL;
 	return SUCCESS;
 }
 /* }}} */
 
 /* {{{ PHP_INI_MH */
 static PHP_INI_MH(OnUpdateMailLog)
 {
-	/* Only do the safemode/open_basedir check at runtime */
-	if ((stage == PHP_INI_STAGE_RUNTIME || stage == PHP_INI_STAGE_HTACCESS) && new_value) {
+	/* Only do the open_basedir check at runtime */
+	if ((stage == PHP_INI_STAGE_RUNTIME || stage == PHP_INI_STAGE_HTACCESS) && new_value && ZSTR_LEN(new_value) > 0) {
 		if (PG(open_basedir) && php_check_open_basedir(ZSTR_VAL(new_value))) {
 			return FAILURE;
 		}
 	}
-	OnUpdateString(entry, new_value, mh_arg1, mh_arg2, mh_arg3, stage);
+	char **p = (char **) ZEND_INI_GET_ADDR();
+	*p = new_value && ZSTR_LEN(new_value) > 0 ? ZSTR_VAL(new_value) : NULL;
 	return SUCCESS;
 }
 /* }}} */

tests/security/error_log_special_values.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Setting error_log to special values with open_basedir enabled
+--INI--
+open_basedir=foo
+error_log=
+--FILE--
+<?php
+var_dump(ini_set("error_log", "syslog"));
+var_dump(ini_set("error_log", ""));
+?>
+--EXPECT--
+string(0) ""
+string(6) "syslog"