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>
This commit is contained in:
Markus Armbruster 2018-08-23 18:40:05 +02:00
parent 61030280ca
commit 2cbd15aa6f
5 changed files with 25 additions and 19 deletions

View file

@ -33,12 +33,12 @@ typedef enum json_token_type {
} JSONTokenType;
typedef struct JSONLexer {
int state;
int start_state, state;
GString *token;
int x, y;
} JSONLexer;
void json_lexer_init(JSONLexer *lexer);
void json_lexer_init(JSONLexer *lexer, bool enable_interpolation);
void json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size);

View file

@ -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);
}
}

View file

@ -427,10 +427,6 @@ static QObject *parse_interpolation(JSONParserContext *ctxt, va_list *ap)
{
JSONToken *token;
if (ap == NULL) {
return NULL;
}
token = parser_context_pop_token(ctxt);
assert(token && token->type == JSON_INTERP);

View file

@ -115,7 +115,7 @@ void json_message_parser_init(JSONMessageParser *parser,
parser->tokens = g_queue_new();
parser->token_size = 0;
json_lexer_init(&parser->lexer);
json_lexer_init(&parser->lexer, !!ap);
}
void json_message_parser_feed(JSONMessageParser *parser,

View file

@ -94,6 +94,10 @@ static void test_malformed(QTestState *qts)
/* lexical error: interpolation */
qtest_qmp_send_raw(qts, "%%p\n");
/* two errors, one for "%", one for "p" */
resp = qtest_qmp_receive(qts);
g_assert_cmpstr(get_error_class(resp), ==, "GenericError");
qobject_unref(resp);
resp = qtest_qmp_receive(qts);
g_assert_cmpstr(get_error_class(resp), ==, "GenericError");
qobject_unref(resp);