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