Repository navigation
fuzzing: add a fuzzer for cJSON_Utils - #1118
Open
0xalpharush wants to merge 3 commits into
Open
0xalpharush wants to merge 3 commits into
0xalpharush wants to merge 3 commits into
Conversation
No fuzzer covered cJSON_Utils. The new target parses two documents and runs the JSON Pointer, JSON Patch and merge patch functions on them. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The second string is also used as a JSON pointer into the first document, and the item it points to is merged into that document, the case of DaveGamble#1060. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Instead of only merging a document with a part of itself, pass the item the pointer selects as the second argument of every utils function that takes two documents, and use it as the target of cJSONUtils_FindPointerFromObjectTo in place of the first child. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
OSS-Fuzz builds only
cjson_read_fuzzer, so nothing fuzzescJSON_Utils.c. This addscjson_utils_fuzzer. Its input is two NUL-terminated strings. The fuzzer parses both, then runs JSON Pointer lookup, applying the second document as a JSON Patch, generating and applying patches, merge patch,FindPointerFromObjectToandSortObject. The second string is also used as a JSON Pointer into the first document. The item it selects is passed as the second argument of every function that takes two documents (merge patch, apply patches, generate patches, generate merge patch, find pointer), so the fuzzer also covers a document combined with part of itself, the case of #1060.ossfuzz.shnow buildscJSON_Utilsand the new target, and reusesjson.dict. OSS-Fuzz runsossfuzz.sh, so it picks up the new target with no change on its side.Tested (clang 18, ASan+UBSan, libFuzzer):
On
fb16e5c^, before theapply_patchtype-confusion fix (Fix: Type Confusion vulnerability in cJSONUtils_ApplyPatches #1006), the fuzzer finds that bug (SEGV incJSONUtils_strdup) in about 276k runs. The crashing input runs clean on current master.On current master it finds the open merge-patch use-after-free bugs, on the first pass over seeds from
tests/json-patch-tests:cJSONUtils_MergePatchvia Recursive Deletion #1092[{"a":1}], pointer/0(the Fix: heap-use-after-free in merge_patch when target is not an object and contains patch (Variant of what #1060 fixed) #1109 case){"foo": 1}, pointer[](the whole document merged into itself)Neither fix covers both cases, and the two do not apply together. So OSS-Fuzz will report this until both cases are fixed.
A sample of 400 of the crashes from a 300 s fork-mode run on master all match these two cases. With the merge-patch call removed, a further 240 s run had no crashes.
Without the in-document calls, 600 s on master: 6.2M runs, no crash or leak.
🤖 Generated with Claude Code