From 1b504e26abc895d54d79a1437fd9694fd2c13b4b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Afonso=20Janu=C3=A1rio?= Date: Fri, 25 Sep 2026 23:52:49 +0100 Subject: [PATCH] json_patch: fix move/copy false rejection between sibling keys sharing a prefix json_patch_apply_move_copy() checks that "from" is not a proper prefix of "path" per RFC 6902 section 4.4 (a location cannot be moved into one of its own children), but it did so with a plain strncmp() over the raw pointer strings, without checking that the shared run of characters actually ends on a JSON Pointer reference-token boundary in "path". As a result, moving or copying between two sibling object keys where one name is a textual prefix of the other, e.g. "/aa" to "/aab", was rejected with "Invalid attempt to move parent under a child" even though "/aa" is not an ancestor pointer of "/aab" at all, just an unrelated key that happens to share a few leading characters. The fix requires that the character in "path" right after the shared "from" prefix be either the end of the string (equal paths, a no-op) or a '/' (a genuine nested reference token), before treating it as an attempt to move a location under its own descendant. Added two cases to json_patch_tests.json covering the move and copy operations between such sibling keys, and refreshed the corresponding golden test_json_patch.expected output. --- json_patch.c | 14 ++++++++++++-- tests/json_patch_tests.json | 10 ++++++++++ tests/test_json_patch.expected | 2 ++ 3 files changed, 24 insertions(+), 2 deletions(-) diff --git a/json_patch.c b/json_patch.c index 90e9d19..8fb7f08 100644 --- a/json_patch.c +++ b/json_patch.c @@ -215,7 +215,17 @@ static int json_patch_apply_move_copy(struct json_object **res, } from_s_len = strlen(from_s); - if (strncmp(from_s, path, from_s_len) == 0) { + /** + * "from" is only a (possibly improper) prefix of "path" when the + * shared run of characters ends on a reference-token boundary in + * "path", i.e. the next character is '/' or the strings end there. + * Without the boundary check, "from" being a plain string prefix of + * "path" (e.g. "/aa" and "/aab") was mistaken for "from" being an + * ancestor pointer of "path", rejecting moves/copies between mere + * sibling keys that happen to share a name prefix. + */ + if (strncmp(from_s, path, from_s_len) == 0 && + (path[from_s_len] == '\0' || path[from_s_len] == '/')) { /** * If lengths match, it's a noop, if they don't, * then we're trying to move a parent under a child @@ -223,7 +233,7 @@ static int json_patch_apply_move_copy(struct json_object **res, * The "from" location MUST NOT be a proper prefix of the "path" * location; i.e., a location cannot be moved into one of its children. */ - if (from_s_len == strlen(path)) + if (path[from_s_len] == '\0') return 0; _set_err(EINVAL, "Invalid attempt to move parent under a child"); return -1; diff --git a/tests/json_patch_tests.json b/tests/json_patch_tests.json index 80103c0..9a0ecea 100644 --- a/tests/json_patch_tests.json +++ b/tests/json_patch_tests.json @@ -370,6 +370,16 @@ "patch": [{"op": "move", "from": "/foo", "path": "/foo"}], "expected": {"foo": 1} }, + { "comment": "Move between sibling keys sharing a name prefix is not a parent/child move", + "doc": {"aa": 1, "aab": 2}, + "patch": [{"op": "move", "from": "/aa", "path": "/aab"}], + "expected": {"aab": 1} }, + + { "comment": "Copy between sibling keys sharing a name prefix is not a parent/child move", + "doc": {"aa": 1, "aab": 2}, + "patch": [{"op": "copy", "from": "/aa", "path": "/aab"}], + "expected": {"aa": 1, "aab": 1} }, + { "doc": {"foo": 1, "baz": [{"qux": "hello"}]}, "patch": [{"op": "move", "from": "/foo", "path": "/bar"}], "expected": {"baz": [{"qux": "hello"}], "bar": 1} }, diff --git a/tests/test_json_patch.expected b/tests/test_json_patch.expected index 8882779..bf9ffab 100644 --- a/tests/test_json_patch.expected +++ b/tests/test_json_patch.expected @@ -100,6 +100,8 @@ Testing 'Test the whole document, no match', doc '{ "foo": 1 }' patch '[ { "op": Testing 'Empty-string element', doc '{ "": 1 }' patch '[ { "op": "test", "path": "\/", "value": 1 } ]' : OK Testing '(null)', doc '{ "foo": [ "bar", "baz" ], "": 0, "a\/b": 1, "c%d": 2, "e^f": 3, "g|h": 4, "i\\j": 5, "k\"l": 6, " ": 7, "m~n": 8 }' patch '[ { "op": "test", "path": "\/foo", "value": [ "bar", "baz" ] }, { "op": "test", "path": "\/foo\/0", "value": "bar" }, { "op": "test", "path": "\/", "value": 0 }, { "op": "test", "path": "\/a~1b", "value": 1 }, { "op": "test", "path": "\/c%d", "value": 2 }, { "op": "test", "path": "\/e^f", "value": 3 }, { "op": "test", "path": "\/g|h", "value": 4 }, { "op": "test", "path": "\/i\\j", "value": 5 }, { "op": "test", "path": "\/k\"l", "value": 6 }, { "op": "test", "path": "\/ ", "value": 7 }, { "op": "test", "path": "\/m~0n", "value": 8 } ]' : OK Testing 'Move to same location has no effect', doc '{ "foo": 1 }' patch '[ { "op": "move", "from": "\/foo", "path": "\/foo" } ]' : OK +Testing 'Move between sibling keys sharing a name prefix is not a parent/child move', doc '{ "aa": 1, "aab": 2 }' patch '[ { "op": "move", "from": "\/aa", "path": "\/aab" } ]' : OK +Testing 'Copy between sibling keys sharing a name prefix is not a parent/child move', doc '{ "aa": 1, "aab": 2 }' patch '[ { "op": "copy", "from": "\/aa", "path": "\/aab" } ]' : OK Testing '(null)', doc '{ "foo": 1, "baz": [ { "qux": "hello" } ] }' patch '[ { "op": "move", "from": "\/foo", "path": "\/bar" } ]' : OK Testing '(null)', doc '{ "baz": [ { "qux": "hello" } ], "bar": 1 }' patch '[ { "op": "move", "from": "\/baz\/0\/qux", "path": "\/baz\/1" } ]' : OK Testing '(null)', doc '{ "baz": [ { "qux": "hello" } ], "bar": 1 }' patch '[ { "op": "copy", "from": "\/baz\/0", "path": "\/boo" } ]' : OK