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Honor allow_exceptions=false for excessive array/object size (out_of_range.408) (#5467)

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* Honor allow_exceptions=false for excessive array/object size (out_of_range.408)

The SAX DOM parsers' start_object()/start_array() threw out_of_range.408
directly via JSON_THROW when a binary format (CBOR/UBJSON/BJData) declared
a container size exceeding max_size(), bypassing the allow_exceptions flag
that every other malformed-input error path in these classes honors via
parse_error(). This meant that json::from_cbor(data, true, false) etc.
could still throw (or abort under JSON_NOEXCEPTION) instead of returning a
discarded value, contrary to the allow_exceptions=false contract.

Route all four call sites (two in json_sax_dom_parser, two in
json_sax_dom_callback_parser) through parse_error() instead, matching the
existing error-handling pattern used elsewhere in this file. Behavior is
unchanged when allow_exceptions is true (the default); the exception
message and type are identical.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Drop a non-portable exact exception message check in the 408 test

The allow_exceptions=false regression test checked the exact message
text produced when allow_exceptions=true (the default). On platforms
where std::size_t is 32-bit (e.g. mingw x86, MSVC Win32 builds), a
declared CBOR length of 2^63 is intercepted earlier, by
get_cbor_container_size()'s own (pre-existing, already correct)
length-narrowing check, with different wording than this fix's
start_array()/start_object() size check -- same error code, same
"still throws when allow_exceptions=true" guarantee, different text.

CHECK_THROWS_AS already verifies the behavior this test cares about
(still throws json::out_of_range, unchanged); drop the exact-message
assertion since it isn't portable across size_t widths and doesn't
add coverage of this fix specifically.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix -Werror=unused-result on json::from_cbor() in the 408 regression test

from_cbor() is [[nodiscard]]; CHECK_THROWS_AS() otherwise discards its
result, which GCC flags under -Werror. Assign to a throwaway json, as
the rest of the suite already does for from_cbor()/from_msgpack().

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-22 21:52:31 +02:00
committed by GitHub
parent e485441123
commit a2b19d6158
3 changed files with 39 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/nlohmann/detail/input/json_sax.hpp
+4 -4
View File
@@ -278,7 +278,7 @@ class json_sax_dom_parser
if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
{
JSON_THROW(out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
}
return true;
@@ -327,7 +327,7 @@ class json_sax_dom_parser
if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
{
JSON_THROW(out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
}
if (len != detail::unknown_size())
@@ -611,7 +611,7 @@ class json_sax_dom_callback_parser
// check object limit
if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
{
JSON_THROW(out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
}
}
return true;
@@ -730,7 +730,7 @@ class json_sax_dom_callback_parser
// check array limit
if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
{
JSON_THROW(out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
}
if (len != detail::unknown_size())
single_include/nlohmann/json.hpp
+4 -4
View File
@@ -11051,7 +11051,7 @@ class json_sax_dom_parser
if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
{
JSON_THROW(out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
}
return true;
@@ -11100,7 +11100,7 @@ class json_sax_dom_parser
if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
{
JSON_THROW(out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
}
if (len != detail::unknown_size())
@@ -11384,7 +11384,7 @@ class json_sax_dom_callback_parser
// check object limit
if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
{
JSON_THROW(out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
}
}
return true;
@@ -11503,7 +11503,7 @@ class json_sax_dom_callback_parser
// check array limit
if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
{
JSON_THROW(out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
}
if (len != detail::unknown_size())
tests/src/unit-regression2.cpp
+31
View File
@@ -834,4 +834,35 @@ TEST_CASE("regression test - parser callback must not lose a duplicate key's pri
}
}
TEST_CASE("regression test - excessive binary container size honors allow_exceptions=false")
{
// CBOR array with declared length 2^63
const std::vector<std::uint8_t> cbor = {0x9b, 0x80, 0, 0, 0, 0, 0, 0, 0};
// CBOR map with declared length 2^63
const std::vector<std::uint8_t> cbor_m = {0xbb, 0x80, 0, 0, 0, 0, 0, 0, 0};
// UBJSON array with declared length 2^63-1
const std::vector<std::uint8_t> ubj = {'[', '#', 'L', 0x7f, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
// BJData array with declared length 2^63-1 (little endian)
const std::vector<std::uint8_t> bjd = {'[', '#', 'L', 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f};
// allow_exceptions=false must report failure instead of throwing/aborting
CHECK(json::from_cbor(cbor, true, false).is_discarded());
CHECK(json::from_cbor(cbor_m, true, false).is_discarded());
CHECK(json::from_ubjson(ubj, true, false).is_discarded());
CHECK(json::from_bjdata(bjd, true, false).is_discarded());
// allow_exceptions=true (the default) must still throw exactly as before.
// The exact message text is not checked here: on platforms where
// std::size_t is 32-bit, the CBOR reader's own length-narrowing check
// (get_cbor_container_size(), unrelated to this fix) intercepts a
// declared length of 2^63 before it ever reaches the check this test
// targets, with different (but equally valid, and already correct)
// wording -- see unit-cbor.cpp for coverage of that message.
json _;
CHECK_THROWS_AS(_ = json::from_cbor(cbor), json::out_of_range);
// regression guard: a genuinely truncated CBOR input must remain discarded
CHECK(json::from_cbor(std::vector<std::uint8_t> {0x9b, 0, 0, 0, 0, 0, 0, 0, 0x02}, true, false).is_discarded());
}
DOCTEST_CLANG_SUPPRESS_WARNING_POP