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UBJSON/BJData reader: reject a container count equal to SIZE_MAX

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The reader marks a container whose count is not known by npos, which
is SIZE_MAX. A count of exactly that value was stored unchanged and
then read as "no count", so the BJData input

    [ # M ff ff ff ff ff ff ff ff i 01 ]

parsed as [1] instead of throwing out_of_range.408 as a count of
2^64-2 does. Where size_t is 32 bits, the same holds for 'm' and 'L'
counts of 2^32-1, in UBJSON too.

The counts of 'm', 'M' and the signed types now go through
store_ubjson_count(), which rejects npos with "integer value overflow"
(the message a count beyond size_t already gets), as the CBOR reader
does in get_cbor_container_size(). An ND-array dimension of 2^64-1 gets
the same message now, where it was "excessive ndarray size caused
overflow" (the product check) on 64-bit platforms.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann committed 2026-11-02 07:01:16 +01:00
1 parent b2674a4a2f
commit db73a6044f
4 files changed
+84 -16
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tests/src/unit-bjdata.cpp
+24 -4
View File
@@ -3211,14 +3211,34 @@ TEST_CASE("BJData")
#endif
CHECK(json::from_bjdata(vM, true, false).is_discarded());
#if SIZE_MAX != 0xffffffff
CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vMX), "[json.exception.out_of_range.408] syntax error while parsing BJData size: excessive ndarray size caused overflow", json::out_of_range&);
#else
// the first dimension is 2^64-1, which is rejected as a count (see below)
CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vMX), "[json.exception.out_of_range.408] syntax error while parsing BJData size: integer value overflow", json::out_of_range&);
#endif
CHECK(json::from_bjdata(vMX, true, false).is_discarded());
}
SECTION("optimized array: count equal to SIZE_MAX")
{
// the reader marks a container without a count by SIZE_MAX, so
// a count of that value must not be read as "no count"
// (it used to parse as [1])
json _;
#if SIZE_MAX != 0xffffffff
std::vector<uint8_t> const vM = {'[', '#', 'M', 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 'i', 0x01, ']'};
CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vM), "[json.exception.out_of_range.408] syntax error while parsing BJData size: integer value overflow", json::out_of_range&);
CHECK(json::from_bjdata(vM, true, false).is_discarded());
// one less is an ordinary excessive count
std::vector<uint8_t> const vM1 = {'[', '#', 'M', 0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 'i', 0x01, ']'};
CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vM1), "[json.exception.out_of_range.408] excessive array size: 18446744073709551614", json::out_of_range&);
#else
std::vector<uint8_t> const vm = {'[', '#', 'm', 0xFF, 0xFF, 0xFF, 0xFF, 'i', 0x01, ']'};
CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vm), "[json.exception.out_of_range.408] syntax error while parsing BJData size: integer value overflow", json::out_of_range&);
CHECK(json::from_bjdata(vm, true, false).is_discarded());
std::vector<uint8_t> const vL = {'[', '#', 'L', 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 'i', 0x01, ']'};
CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vL), "[json.exception.out_of_range.408] syntax error while parsing BJData size: integer value overflow", json::out_of_range&);
CHECK(json::from_bjdata(vL, true, false).is_discarded());
#endif
}
SECTION("optimized array: integer value overflow")
{
#if SIZE_MAX == 0xffffffff