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authorMarkus Armbruster <armbru@redhat.com>2018-08-23 18:40:05 +0200
committerMarkus Armbruster <armbru@redhat.com>2018-08-24 20:26:37 +0200
commit2cbd15aa6f4d4694376dd0d231d56e572ac870c1 (patch)
tree80bffd7131ee398510fb7961dfc0cb2982bed852 /qobject/json-lexer.c
parent61030280ca2d67bd63cb068250aee55849cd38ca (diff)
json: Treat unwanted interpolation as lexical error
The JSON parser optionally supports interpolation. The lexer recognizes interpolation tokens unconditionally. The parser rejects them when interpolation is disabled, in parse_interpolation(). However, it neglects to set an error then, which can make json_parser_parse() fail without setting an error. Move the check for unwanted interpolation from the parser's parse_interpolation() into the lexer's finite state machine. When interpolation is disabled, '%' is now handled like any other unexpected character. The next commit will improve how such lexical errors are handled. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-Id: <20180823164025.12553-39-armbru@redhat.com>
Diffstat (limited to 'qobject/json-lexer.c')
-rw-r--r--qobject/json-lexer.c30
1 files changed, 18 insertions, 12 deletions
diff --git a/qobject/json-lexer.c b/qobject/json-lexer.c
index 5436809be6..96fe13621d 100644
--- a/qobject/json-lexer.c
+++ b/qobject/json-lexer.c
@@ -92,7 +92,7 @@
* Like double-quoted strings, except they're delimited by %x27
* (apostrophe) instead of %x22 (quotation mark), and can't contain
* unescaped apostrophe, but can contain unescaped quotation mark.
- * - Interpolation:
+ * - Interpolation, if enabled:
* interpolation = %((l|ll|I64)[du]|[ipsf])
*
* Note:
@@ -123,9 +123,11 @@ enum json_lexer_state {
IN_INTERP_I64,
IN_WHITESPACE,
IN_START,
+ IN_START_INTERP, /* must be IN_START + 1 */
};
-QEMU_BUILD_BUG_ON((int)JSON_MIN <= (int)IN_START);
+QEMU_BUILD_BUG_ON((int)JSON_MIN <= (int)IN_START_INTERP);
+QEMU_BUILD_BUG_ON(IN_START_INTERP != IN_START + 1);
#define TERMINAL(state) [0 ... 0x7F] = (state)
@@ -257,8 +259,12 @@ static const uint8_t json_lexer[][256] = {
['I'] = IN_INTERP_I,
},
- /* top level rule */
- [IN_START] = {
+ /*
+ * Two start states:
+ * - IN_START recognizes JSON tokens with our string extensions
+ * - IN_START_INTERP additionally recognizes interpolation.
+ */
+ [IN_START ... IN_START_INTERP] = {
['"'] = IN_DQ_STRING,
['\''] = IN_SQ_STRING,
['0'] = IN_ZERO,
@@ -271,17 +277,18 @@ static const uint8_t json_lexer[][256] = {
[','] = JSON_COMMA,
[':'] = JSON_COLON,
['a' ... 'z'] = IN_KEYWORD,
- ['%'] = IN_INTERP,
[' '] = IN_WHITESPACE,
['\t'] = IN_WHITESPACE,
['\r'] = IN_WHITESPACE,
['\n'] = IN_WHITESPACE,
},
+ [IN_START_INTERP]['%'] = IN_INTERP,
};
-void json_lexer_init(JSONLexer *lexer)
+void json_lexer_init(JSONLexer *lexer, bool enable_interpolation)
{
- lexer->state = IN_START;
+ lexer->start_state = lexer->state = enable_interpolation
+ ? IN_START_INTERP : IN_START;
lexer->token = g_string_sized_new(3);
lexer->x = lexer->y = 0;
}
@@ -321,7 +328,7 @@ static void json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush)
/* fall through */
case JSON_SKIP:
g_string_truncate(lexer->token, 0);
- new_state = IN_START;
+ new_state = lexer->start_state;
break;
case IN_ERROR:
/* XXX: To avoid having previous bad input leaving the parser in an
@@ -340,8 +347,7 @@ static void json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush)
json_message_process_token(lexer, lexer->token, JSON_ERROR,
lexer->x, lexer->y);
g_string_truncate(lexer->token, 0);
- new_state = IN_START;
- lexer->state = new_state;
+ lexer->state = lexer->start_state;
return;
default:
break;
@@ -356,7 +362,7 @@ static void json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush)
json_message_process_token(lexer, lexer->token, lexer->state,
lexer->x, lexer->y);
g_string_truncate(lexer->token, 0);
- lexer->state = IN_START;
+ lexer->state = lexer->start_state;
}
}
@@ -371,7 +377,7 @@ void json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size)
void json_lexer_flush(JSONLexer *lexer)
{
- if (lexer->state != IN_START) {
+ if (lexer->state != lexer->start_state) {
json_lexer_feed_char(lexer, 0, true);
}
}