qobject/json-streamer.c

   1 /*
   2  * JSON streaming support
   3  *
   4  * Copyright IBM, Corp. 2009
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu/osdep.h"
  15 #include "qemu-common.h"
  16 #include "qapi/error.h"
  17 #include "qapi/qmp/json-lexer.h"
  18 #include "qapi/qmp/json-parser.h"
  19 #include "qapi/qmp/json-streamer.h"
  20
  21 #define MAX_TOKEN_SIZE (64ULL << 20)
  22 #define MAX_TOKEN_COUNT (2ULL << 20)
  23 #define MAX_NESTING (1 << 10)
  24
  25 static void json_message_free_tokens(JSONMessageParser *parser)
  26 {
  27     JSONToken *token;
  28
  29     while ((token = g_queue_pop_head(&parser->tokens))) {
  30         g_free(token);
  31     }
  32 }
  33
  34 void json_message_process_token(JSONLexer *lexer, GString *input,
  35                                 JSONTokenType type, int x, int y)
  36 {
  37     JSONMessageParser *parser = container_of(lexer, JSONMessageParser, lexer);
  38     QObject *json = NULL;
  39     Error *err = NULL;
  40     JSONToken *token;
  41
  42     switch (type) {
  43     case JSON_LCURLY:
  44         parser->brace_count++;
  45         break;
  46     case JSON_RCURLY:
  47         parser->brace_count--;
  48         break;
  49     case JSON_LSQUARE:
  50         parser->bracket_count++;
  51         break;
  52     case JSON_RSQUARE:
  53         parser->bracket_count--;
  54         break;
  55     case JSON_ERROR:
  56         error_setg(&err, "JSON parse error, stray '%s'", input->str);
  57         goto out_emit;
  58     case JSON_END_OF_INPUT:
  59         if (g_queue_is_empty(&parser->tokens)) {
  60             return;
  61         }
  62         json = json_parser_parse(&parser->tokens, parser->ap, &err);
  63         goto out_emit;
  64     default:
  65         break;
  66     }
  67
  68     /*
  69      * Security consideration, we limit total memory allocated per object
  70      * and the maximum recursion depth that a message can force.
  71      */
  72     if (parser->token_size + input->len + 1 > MAX_TOKEN_SIZE) {
  73         error_setg(&err, "JSON token size limit exceeded");
  74         goto out_emit;
  75     }
  76     if (g_queue_get_length(&parser->tokens) + 1 > MAX_TOKEN_COUNT) {
  77         error_setg(&err, "JSON token count limit exceeded");
  78         goto out_emit;
  79     }
  80     if (parser->bracket_count + parser->brace_count > MAX_NESTING) {
  81         error_setg(&err, "JSON nesting depth limit exceeded");
  82         goto out_emit;
  83     }
  84
  85     token = json_token(type, x, y, input);
  86     parser->token_size += input->len;
  87
  88     g_queue_push_tail(&parser->tokens, token);
  89
  90     if ((parser->brace_count > 0 || parser->bracket_count > 0)
  91         && parser->bracket_count >= 0 && parser->bracket_count >= 0) {
  92         return;
  93     }
  94
  95     json = json_parser_parse(&parser->tokens, parser->ap, &err);
  96
  97 out_emit:
  98     parser->brace_count = 0;
  99     parser->bracket_count = 0;
 100     json_message_free_tokens(parser);
 101     parser->token_size = 0;
 102     parser->emit(parser->opaque, json, err);
 103 }
 104
 105 void json_message_parser_init(JSONMessageParser *parser,
 106                               void (*emit)(void *opaque, QObject *json,
 107                                            Error *err),
 108                               void *opaque, va_list *ap)
 109 {
 110     parser->emit = emit;
 111     parser->opaque = opaque;
 112     parser->ap = ap;
 113     parser->brace_count = 0;
 114     parser->bracket_count = 0;
 115     g_queue_init(&parser->tokens);
 116     parser->token_size = 0;
 117
 118     json_lexer_init(&parser->lexer, !!ap);
 119 }
 120
 121 void json_message_parser_feed(JSONMessageParser *parser,
 122                              const char *buffer, size_t size)
 123 {
 124     json_lexer_feed(&parser->lexer, buffer, size);
 125 }
 126
 127 void json_message_parser_flush(JSONMessageParser *parser)
 128 {
 129     json_lexer_flush(&parser->lexer);
 130     assert(g_queue_is_empty(&parser->tokens));
 131 }
 132
 133 void json_message_parser_destroy(JSONMessageParser *parser)
 134 {
 135     json_lexer_destroy(&parser->lexer);
 136     json_message_free_tokens(parser);
 137 }