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json: reject trailing garbage

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Yajl 2 has a nice feature that it can be configured whether to
allow multiple JSON objects parsed from a single stream, defaulting
to off.  And yajl 1.0.12 at least provided a way to tell if all
input bytes were parsed, or if trailing bytes remained after a
valid JSON object was parsed.  But we target RHEL 6 yajl 1.0.7,
which has neither of these.  So fake it by always parsing '[...]'
instead, so that trailing garbage either trips up the array parse,
or is easily detected when unwrapping the result.

* src/util/virjson.c (virJSONValueFromString): With older json,
wrap text to avoid trailing garbage.
* tests/jsontest.c (mymain): Add tests for this.

Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Eric Blake 2015-06-22 14:18:34 -06:00 committed by Michal Privoznik
parent 54dbba5bc3
commit 7cd991b74c
2 changed files with 30 additions and 1 deletions
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29
src/util/virjson.c
View File

@ -1597,6 +1597,7 @@ virJSONValueFromString(const char *jsonstring)
size_t len = strlen(jsonstring);
# ifndef WITH_YAJL2
yajl_parser_config cfg = { 0, 1 };
virJSONValuePtr tmp;
# endif
VIR_DEBUG("string=%s", jsonstring);
@ -1616,7 +1617,21 @@ virJSONValueFromString(const char *jsonstring)
goto cleanup;
}
/* Yajl 2 is nice enough to default to rejecting trailing garbage.
* Yajl 1.0.12 has yajl_get_bytes_consumed to make that detection
* simpler. But we're stuck with yajl 1.0.7 on RHEL 6, which
* happily quits parsing at the end of a valid JSON construct,
* with no visibility into how much more input remains. Wrapping
* things in an array forces yajl to confess the truth. */
# ifdef WITH_YAJL2
rc = yajl_parse(hand, (const unsigned char *)jsonstring, len);
# else
rc = yajl_parse(hand, (const unsigned char *)"[", 1);
if (VIR_YAJL_STATUS_OK(rc))
rc = yajl_parse(hand, (const unsigned char *)jsonstring, len);
if (VIR_YAJL_STATUS_OK(rc))
rc = yajl_parse(hand, (const unsigned char *)"]", 1);
# endif
if (!VIR_YAJL_STATUS_OK(rc) ||
yajl_complete_parse(hand) != yajl_status_ok) {
unsigned char *errstr = yajl_get_error(hand, 1,
@ -1638,6 +1653,18 @@ virJSONValueFromString(const char *jsonstring)
virJSONValueFree(parser.head);
} else {
ret = parser.head;
# ifndef WITH_YAJL2
/* Undo the array wrapping above */
tmp = ret;
ret = NULL;
if (virJSONValueArraySize(tmp) > 1)
virReportError(VIR_ERR_INTERNAL_ERROR,
_("cannot parse json %s: too many items present"),
jsonstring);
else
ret = virJSONValueArraySteal(tmp, 0);
virJSONValueFree(tmp);
# endif
}
cleanup:
@ -1650,7 +1677,7 @@ virJSONValueFromString(const char *jsonstring)
VIR_FREE(parser.state);
}
VIR_DEBUG("result=%p", parser.head);
VIR_DEBUG("result=%p", ret);
return ret;
}

2
tests/jsontest.c
View File

@ -419,6 +419,8 @@ mymain(void)
DO_TEST_PARSE_FAIL("overdone keyword", "[ truest ]");
DO_TEST_PARSE_FAIL("unknown keyword", "huh");
DO_TEST_PARSE_FAIL("comments", "[ /* nope */\n1 // not this either\n]");
DO_TEST_PARSE_FAIL("trailing garbage", "[] []");
DO_TEST_PARSE_FAIL("list without array", "1, 1");
DO_TEST_PARSE_FAIL("object with numeric keys", "{ 1:1, 2:1, 3:2 }");
DO_TEST_PARSE_FAIL("unterminated object", "{ \"1\":1, \"2\":1, \"3\":2");