Fixes Oss-Fuzz issue: 21916 (open-source-parsers#1180)

kabeer27 · web-flow · commit 6aba23f4a862 · 2020-05-29T21:50:26.000+08:00
* Fix heap-buffer-overflow in json_reader
diff --git a/src/lib_json/json_reader.cpp b/src/lib_json/json_reader.cpp
@@ -1270,7 +1270,7 @@ void OurReader::skipSpaces() {
 void OurReader::skipBom(bool skipBom) {
   // The default behavior is to skip BOM.
   if (skipBom) {
-    if (strncmp(begin_, "\xEF\xBB\xBF", 3) == 0) {
+    if ((end_ - begin_) >= 3 && strncmp(begin_, "\xEF\xBB\xBF", 3) == 0) {
       begin_ += 3;
       current_ = begin_;
     }

Original file line number	Diff line number	Diff line change
`@@ -1270,7 +1270,7 @@ void OurReader::skipSpaces() {`
`1270`	`1270`	`void OurReader::skipBom(bool skipBom) {`
`1271`	`1271`	`// The default behavior is to skip BOM.`
`1272`	`1272`	`if (skipBom) {`
`1273`		`- if (strncmp(begin_, "\xEF\xBB\xBF", 3) == 0) {`
	`1273`	`+ if ((end_ - begin_) >= 3 && strncmp(begin_, "\xEF\xBB\xBF", 3) == 0) {`
`1274`	`1274`	`begin_ += 3;`
`1275`	`1275`	`current_ = begin_;`
`1276`	`1276`	`}`