From 84a56f38b23440cb3127eaffe4e495826a29f18c Mon Sep 17 00:00:00 2001 From: Markus Armbruster Date: Thu, 23 Aug 2018 18:40:06 +0200 Subject: [PATCH] json: Pass lexical errors and limit violations to callback The callback to consume JSON values takes QObject *json, Error *err. If both are null, the callback is supposed to make up an error by itself. This sucks. qjson.c's consume_json() neglects to do so, which makes qobject_from_json() null instead of failing. I consider that a bug. The culprit is json_message_process_token(): it passes two null pointers when it runs into a lexical error or a limit violation. Fix it to pass a proper Error object then. Update the callbacks: * monitor.c's handle_qmp_command(): the code to make up an error is now dead, drop it. * qga/main.c's process_event(): lumps the "both null" case together with the "not a JSON object" case. The former is now gone. The error message "Invalid JSON syntax" is misleading for the latter. Improve it to "Input must be a JSON object". * qobject/qjson.c's consume_json(): no update; check-qjson demonstrates qobject_from_json() now sets an error on lexical errors, but still doesn't on some other errors. * tests/libqtest.c's qmp_response(): the Error object is now reliable, so use it to improve the error message. Signed-off-by: Markus Armbruster Reviewed-by: Eric Blake Message-Id: <20180823164025.12553-40-armbru@redhat.com> --- include/qapi/qmp/qerror.h | 3 --- monitor.c | 5 +---- qga/main.c | 3 ++- qobject/json-lexer.c | 3 +-- qobject/json-streamer.c | 22 ++++++++++++++++------ tests/check-qjson.c | 15 ++++++++------- tests/libqtest.c | 7 +++++-- 7 files changed, 33 insertions(+), 25 deletions(-) diff --git a/include/qapi/qmp/qerror.h b/include/qapi/qmp/qerror.h index c82360f429..145571f618 100644 --- a/include/qapi/qmp/qerror.h +++ b/include/qapi/qmp/qerror.h @@ -61,9 +61,6 @@ #define QERR_IO_ERROR \ "An IO error has occurred" -#define QERR_JSON_PARSING \ - "Invalid JSON syntax" - #define QERR_MIGRATION_ACTIVE \ "There's a migration process in progress" diff --git a/monitor.c b/monitor.c index 08f799a7bb..3dbdcb5190 100644 --- a/monitor.c +++ b/monitor.c @@ -4262,10 +4262,7 @@ static void handle_qmp_command(void *opaque, QObject *req, Error *err) QDict *qdict; QMPRequest *req_obj; - if (!req && !err) { - /* json_parser_parse() sucks: can fail without setting @err */ - error_setg(&err, QERR_JSON_PARSING); - } + assert(!req != !err); qdict = qobject_to(QDict, req); if (qdict) { diff --git a/qga/main.c b/qga/main.c index 2fc49d00d8..b74e1241ef 100644 --- a/qga/main.c +++ b/qga/main.c @@ -603,12 +603,13 @@ static void process_event(void *opaque, QObject *obj, Error *err) int ret; g_debug("process_event: called"); + assert(!obj != !err); if (err) { goto err; } req = qobject_to(QDict, obj); if (!req) { - error_setg(&err, QERR_JSON_PARSING); + error_setg(&err, "Input must be a JSON object"); goto err; } if (!qdict_haskey(req, "execute")) { diff --git a/qobject/json-lexer.c b/qobject/json-lexer.c index 96fe13621d..7c31c2c8ff 100644 --- a/qobject/json-lexer.c +++ b/qobject/json-lexer.c @@ -334,8 +334,7 @@ static void json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush) /* XXX: To avoid having previous bad input leaving the parser in an * unresponsive state where we consume unpredictable amounts of * subsequent "good" input, percolate this error state up to the - * tokenizer/parser by forcing a NULL object to be emitted, then - * reset state. + * parser by emitting a JSON_ERROR token, then reset lexer state. * * Also note that this handling is required for reliable channel * negotiation between QMP and the guest agent, since chr(0xFF) diff --git a/qobject/json-streamer.c b/qobject/json-streamer.c index a373e0114a..e372ecc895 100644 --- a/qobject/json-streamer.c +++ b/qobject/json-streamer.c @@ -13,6 +13,7 @@ #include "qemu/osdep.h" #include "qemu-common.h" +#include "qapi/error.h" #include "qapi/qmp/json-lexer.h" #include "qapi/qmp/json-parser.h" #include "qapi/qmp/json-streamer.h" @@ -57,6 +58,7 @@ void json_message_process_token(JSONLexer *lexer, GString *input, parser->bracket_count--; break; case JSON_ERROR: + error_setg(&err, "JSON parse error, stray '%s'", input->str); goto out_emit; default: break; @@ -82,12 +84,20 @@ void json_message_process_token(JSONLexer *lexer, GString *input, goto out_emit; } - if (parser->token_size > MAX_TOKEN_SIZE || - g_queue_get_length(parser->tokens) > MAX_TOKEN_COUNT || - parser->bracket_count + parser->brace_count > MAX_NESTING) { - /* Security consideration, we limit total memory allocated per object - * and the maximum recursion depth that a message can force. - */ + /* + * Security consideration, we limit total memory allocated per object + * and the maximum recursion depth that a message can force. + */ + if (parser->token_size > MAX_TOKEN_SIZE) { + error_setg(&err, "JSON token size limit exceeded"); + goto out_emit; + } + if (g_queue_get_length(parser->tokens) > MAX_TOKEN_COUNT) { + error_setg(&err, "JSON token count limit exceeded"); + goto out_emit; + } + if (parser->bracket_count + parser->brace_count > MAX_NESTING) { + error_setg(&err, "JSON nesting depth limit exceeded"); goto out_emit; } diff --git a/tests/check-qjson.c b/tests/check-qjson.c index 604886a1a2..d6fda0786f 100644 --- a/tests/check-qjson.c +++ b/tests/check-qjson.c @@ -1021,6 +1021,7 @@ static void interpolation_unknown(void) } g_test_trap_subprocess(NULL, 0, 0); g_test_trap_assert_failed(); + g_test_trap_assert_stderr("*Unexpected error*stray '%x'*"); } static void interpolation_string(void) @@ -1296,11 +1297,11 @@ static void junk_input(void) QObject *obj; obj = qobject_from_json("@", &err); - g_assert(!err); /* BUG */ + error_free_or_abort(&err); g_assert(obj == NULL); obj = qobject_from_json("{\x01", &err); - g_assert(!err); /* BUG */ + error_free_or_abort(&err); g_assert(obj == NULL); obj = qobject_from_json("[0\xFF]", &err); @@ -1308,11 +1309,11 @@ static void junk_input(void) g_assert(obj == NULL); obj = qobject_from_json("00", &err); - g_assert(!err); /* BUG */ + error_free_or_abort(&err); g_assert(obj == NULL); obj = qobject_from_json("[1e", &err); - g_assert(!err); /* BUG */ + error_free_or_abort(&err); g_assert(obj == NULL); obj = qobject_from_json("truer", &err); @@ -1324,7 +1325,7 @@ static void unterminated_string(void) { Error *err = NULL; QObject *obj = qobject_from_json("\"abc", &err); - g_assert(!err); /* BUG */ + error_free_or_abort(&err); g_assert(obj == NULL); } @@ -1332,7 +1333,7 @@ static void unterminated_sq_string(void) { Error *err = NULL; QObject *obj = qobject_from_json("'abc", &err); - g_assert(!err); /* BUG */ + error_free_or_abort(&err); g_assert(obj == NULL); } @@ -1340,7 +1341,7 @@ static void unterminated_escape(void) { Error *err = NULL; QObject *obj = qobject_from_json("\"abc\\\"", &err); - g_assert(!err); /* BUG */ + error_free_or_abort(&err); g_assert(obj == NULL); } diff --git a/tests/libqtest.c b/tests/libqtest.c index 1f3b0cb1b1..5973a67652 100644 --- a/tests/libqtest.c +++ b/tests/libqtest.c @@ -450,8 +450,11 @@ static void qmp_response(void *opaque, QObject *obj, Error *err) { QMPResponseParser *qmp = opaque; - if (!obj) { - fprintf(stderr, "QMP JSON response parsing failed\n"); + assert(!obj != !err); + + if (err) { + error_prepend(&err, "QMP JSON response parsing failed: "); + error_report_err(err); abort(); }