json-streamer: limit the maximum recursion depth and maximum token count

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

json-streamer.c

@@ -18,6 +18,9 @@
 #include "json-lexer.h"
 #include "json-streamer.h"
 
+#define MAX_TOKEN_SIZE (64ULL << 20)
+#define MAX_NESTING (1ULL << 10)
+
 static void json_message_process_token(JSONLexer *lexer, QString *token, JSONTokenType type, int x, int y)
 {
     JSONMessageParser *parser = container_of(lexer, JSONMessageParser, lexer);
@@ -49,6 +52,8 @@ static void json_message_process_token(JSONLexer *lexer, QString *token, JSONTok
     qdict_put(dict, "x", qint_from_int(x));
     qdict_put(dict, "y", qint_from_int(y));
 
+    parser->token_size += token->length;
+
     qlist_append(parser->tokens, dict);
 
     if (parser->brace_count < 0 ||
@@ -60,6 +65,17 @@ static void json_message_process_token(JSONLexer *lexer, QString *token, JSONTok
         parser->emit(parser, parser->tokens);
         QDECREF(parser->tokens);
         parser->tokens = qlist_new();
+    } else if (parser->token_size > MAX_TOKEN_SIZE ||
+               parser->bracket_count > MAX_NESTING ||
+               parser->brace_count > MAX_NESTING) {
+        /* Security consideration, we limit total memory allocated per object
+         * and the maximum recursion depth that a message can force.
+         */
+        parser->brace_count = 0;
+        parser->bracket_count = 0;
+        parser->emit(parser, parser->tokens);
+        QDECREF(parser->tokens);
+        parser->tokens = qlist_new();
     }
 }
 
@@ -70,6 +86,7 @@ void json_message_parser_init(JSONMessageParser *parser,
     parser->brace_count = 0;
     parser->bracket_count = 0;
     parser->tokens = qlist_new();
+    parser->token_size = 0;
 
     json_lexer_init(&parser->lexer, json_message_process_token);
 }