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Add JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE to set the UBJSON whole-input budget (#6083)

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* Add JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE to set the UBJSON whole-input budget

The whole-input budget for the elements of optimized UBJSON arrays of
type Z, T and F (1048576 plus 4 per byte read) rejects files written by
3.12.0 that have long arrays of these types, such as 1100 rows of 1000
nulls with a `$Z` annotation, and there was no way to read them. The
per-byte rate is now the macro JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE.

Semantics:
- default 4, so the default build is unchanged (the generated code of
  from_ubjson is identical at -O2 up to source line numbers);
- the value must be a positive integer: 0, negative, non-integral, bool,
  character and wider-than-uintmax_t values fail to compile with a
  static_assert that names the macro;
- a value that does not fit into std::size_t is the largest size_t, so
  one spelling works for 32- and 64-bit targets;
- the limit base + rate * bytes_read saturates at the largest size_t
  instead of wrapping around, for any rate and input size; a rate of
  131072 (2^20 / 8) or more cannot be exceeded by any input (the
  shortest header of an array of more than 32767 elements is 8 bytes),
  which switches the whole-input budget off;
- the limit of one array (1048576) and the base (1048576) stay fixed
  constants, so the writer fallback still follows the base only and a
  reader with any rate reads everything the writer produces;
- the macro is not part of the ABI tag and must have the same value in
  every translation unit; it is documented that way.

The memory the arrays can take in a DOM is about 20 bytes per rate and
byte of input (measured, macOS, containers of 9 * rate elements:
25 bytes per input byte at rate 1, 81 at 4, 312 at 16, 1226 at 64, 5493
at 256) plus about 33 MB for the base. A 3.12.0 row of N values has a
header of b bytes (5 up to 255, 6 up to 32767, 8 above), so a table is
read completely if N <= rate * b, and otherwise up to
(1048576 + h * rate, h = outer header: 6, 7 or 9 bytes) / (N - rate * b) rows; 1100 rows of 1000 nulls need
a rate of 8. The new page of the macro documents the formulas, the
measurements, and two examples that are run by the documentation checks.

The tests of the budget move to tests/src/unit-ubjson_valueless.cpp, which
derives every boundary from the macro and is built with the rates 1,
1000000 and 0xFFFFFFFFFFFFFFFF in addition to the default (the last two
check that nothing is refused and that the limit does not wrap around);
they fail with the unchanged header for rate 1, 1000000 and the maximum.

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

* Refuse char8_t for JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE and clarify its documentation

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann authored and GitHub committed 2026-11-11 22:37:35 +01:00
1 parent 8001ed67b9
commit 73aea7ce54
22 files changed
+1062 -278
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tests/CMakeLists.txt
+28
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@@ -410,6 +410,34 @@ json_test_add_test_for(src/unit-stream-bulk-scan.cpp
MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
)
# test the budget for the elements of UBJSON containers of a valueless type again
# with other values of JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE: 1 (the smallest),
# 1000000 (so large that the budget cannot be reached), and the largest value of
# a 64-bit integer (which saturates the limit already at the first byte, and is
# clamped to the largest std::size_t where that has 32 bits). The file does not
# mention JSON_HAS_CPP_<n>, so only C++11 is built unless the standards are forced
json_test_set_test_options(test-ubjson_valueless_rate_1
COMPILE_DEFINITIONS JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE=1
)
json_test_add_test_for(src/unit-ubjson_valueless.cpp
NAME test-ubjson_valueless_rate_1
MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
)
json_test_set_test_options(test-ubjson_valueless_rate_1000000
COMPILE_DEFINITIONS JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE=1000000
)
json_test_add_test_for(src/unit-ubjson_valueless.cpp
NAME test-ubjson_valueless_rate_1000000
MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
)
json_test_set_test_options(test-ubjson_valueless_rate_max
COMPILE_DEFINITIONS JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE=0xFFFFFFFFFFFFFFFFu
)
json_test_add_test_for(src/unit-ubjson_valueless.cpp
NAME test-ubjson_valueless_rate_max
MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
)
# test reading from a FILE* again with the locking stdio functions
json_test_set_test_options(test-file_input_unlocked_io_disabled
COMPILE_DEFINITIONS JSON_DISABLE_UNLOCKED_FILE_IO=1
tests/src/ubjson_valueless.hpp
+125
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@@ -0,0 +1,125 @@
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++ (supporting code)
// | | |__ | | | | | | version 3.12.0
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
//
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT
#pragma once
#include <cstddef> // size_t
#include <cstdint> // uint8_t, uint32_t
#include <limits> // numeric_limits
#include <string> // string
#include <vector> // vector
#include <nlohmann/json.hpp>
// helpers of the tests of the budget for the elements of UBJSON containers of
// a valueless type (unit-ubjson.cpp and unit-ubjson_valueless.cpp)
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wweak-vtables"
#endif
namespace utils
{
/// SAX consumer that counts the values and keeps the id of a parse error
struct ValuelessEventCounter : public nlohmann::json_sax<nlohmann::json>
{
bool null() override
{
return ++values < stop_after;
}
bool boolean(bool /*val*/) override
{
return ++values < stop_after;
}
bool number_integer(nlohmann::json::number_integer_t /*val*/) override
{
++values;
return true;
}
bool number_unsigned(nlohmann::json::number_unsigned_t /*val*/) override
{
++values;
return true;
}
bool number_float(nlohmann::json::number_float_t /*val*/, const std::string& /*s*/) override
{
++values;
return true;
}
bool string(std::string& /*val*/) override
{
++values;
return true;
}
bool binary(nlohmann::json::binary_t& /*val*/) override
{
++values;
return true;
}
bool start_object(std::size_t /*elements*/) override
{
return true;
}
bool key(std::string& /*val*/) override
{
return true;
}
bool end_object() override
{
return true;
}
bool start_array(std::size_t /*elements*/) override
{
return true;
}
bool end_array() override
{
return true;
}
bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const nlohmann::json::exception& ex) override
{
error_id = ex.id;
return false;
}
/// the handler refuses the value that makes this many
std::size_t stop_after = (std::numeric_limits<std::size_t>::max)();
std::size_t values = 0;
int error_id = 0;
};
/// appends `[$<marker>#l<count>` (nine bytes) to @a v
inline void append_valueless_array(std::vector<std::uint8_t>& v, const char marker, const std::uint32_t count)
{
v.push_back('[');
v.push_back('$');
v.push_back(static_cast<std::uint8_t>(marker));
v.push_back('#');
v.push_back('l');
v.push_back(static_cast<std::uint8_t>(count >> 24));
v.push_back(static_cast<std::uint8_t>(count >> 16));
v.push_back(static_cast<std::uint8_t>(count >> 8));
v.push_back(static_cast<std::uint8_t>(count));
}
/// `[` followed by one `[$<marker>#l<count>` per entry of @a counts and `]`
inline std::vector<std::uint8_t> valueless_arrays(const char marker, const std::vector<std::uint32_t>& counts)
{
std::vector<std::uint8_t> v = {'['};
for (const auto count : counts)
{
append_valueless_array(v, marker, count);
}
v.push_back(']');
return v;
}
} // namespace utils
#if defined(__clang__)
#pragma clang diagnostic pop
#endif
tests/src/unit-ubjson.cpp
+12 -201
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@@ -19,12 +19,8 @@
#include <nlohmann/json.hpp>
using nlohmann::json;
#include <cstdio>
#include <iostream>
#include <sstream>
#include <utility>
#include <fstream>
#include <limits>
#include <list>
#include <set>
#include "make_test_data_available.hpp"
@@ -33,6 +29,7 @@ using nlohmann::json;
#include "sax_countdown.hpp"
#include "allocation_counter.hpp"
#include "sax_event_loggers.hpp"
#include "ubjson_valueless.hpp"
using utils::SaxCountdown;
using utils::SaxEventLogger;
@@ -2441,208 +2438,22 @@ TEST_CASE("UBJSON optimized arrays of a valueless type are bounded")
}
}
namespace
TEST_CASE("UBJSON the writer keeps the valueless elements of an input within the base")
{
/// SAX consumer that counts the values and keeps the id of a parse error
struct ValuelessEventCounter : public nlohmann::json_sax<json>
{
bool null() override
{
return ++values < stop_after;
}
bool boolean(bool /*val*/) override
{
return ++values < stop_after;
}
bool number_integer(json::number_integer_t /*val*/) override
{
++values;
return true;
}
bool number_unsigned(json::number_unsigned_t /*val*/) override
{
++values;
return true;
}
bool number_float(json::number_float_t /*val*/, const std::string& /*s*/) override
{
++values;
return true;
}
bool string(std::string& /*val*/) override
{
++values;
return true;
}
bool binary(json::binary_t& /*val*/) override
{
++values;
return true;
}
bool start_object(std::size_t /*elements*/) override
{
return true;
}
bool key(std::string& /*val*/) override
{
return true;
}
bool end_object() override
{
return true;
}
bool start_array(std::size_t /*elements*/) override
{
return true;
}
bool end_array() override
{
return true;
}
bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const json::exception& ex) override
{
error_id = ex.id;
return false;
}
/// the handler refuses the value that makes this many
std::size_t stop_after = (std::numeric_limits<std::size_t>::max)();
std::size_t values = 0;
int error_id = 0;
};
/// appends `[$<marker>#l<count>` (nine bytes) to @a v
void append_valueless_array(std::vector<std::uint8_t>& v, const char marker, const std::uint32_t count)
{
v.push_back('[');
v.push_back('$');
v.push_back(static_cast<std::uint8_t>(marker));
v.push_back('#');
v.push_back('l');
v.push_back(static_cast<std::uint8_t>(count >> 24));
v.push_back(static_cast<std::uint8_t>(count >> 16));
v.push_back(static_cast<std::uint8_t>(count >> 8));
v.push_back(static_cast<std::uint8_t>(count));
}
/// `[` followed by one `[$<marker>#l<count>` per entry of @a counts and `]`
std::vector<std::uint8_t> valueless_arrays(const char marker, const std::vector<std::uint32_t>& counts)
{
std::vector<std::uint8_t> v = {'['};
for (const auto count : counts)
{
append_valueless_array(v, marker, count);
}
v.push_back(']');
return v;
}
} // namespace
TEST_CASE("UBJSON the valueless elements of a whole input are bounded")
{
// The per-container limit alone let nine bytes (`[$Z#l` and a count of
// 1048576) announce a million values, and every further nine bytes another
// million. The elements of all containers of type 'Z', 'T' or 'F' in one
// input are now added up: they may not exceed 1048576 plus 4 for every
// byte read when the container's header has been read.
//
// The tests count events with a SAX handler where they can: building and
// comparing values of a million elements is what makes them slow under
// Valgrind, so there is one rejection and one round trip with a DOM.
// The budget of the reader is 1048576 plus a rate per byte read, see
// unit-ubjson_valueless.cpp, which tests it for several values of the rate.
// The writer does not use the rate and stays within the base
json _;
const char* const budget_message = "[json.exception.out_of_range.408] syntax error while parsing UBJSON size: excessive number of elements without payload";
// two arrays that exceed the limit: the second one, with its header read
// at byte 19, may hold 4 * 19 = 76 values on top of the base of 1048576
const std::uint32_t over_first = 524288;
const std::uint32_t over_second = 1048576 + 76 - over_first + 1;
SECTION("the input of the original report is rejected")
{
// 362 bytes (40 arrays of 1048576 values) used to allocate 661 MB; the
// second array is the one that is refused
const auto input = valueless_arrays('Z', {over_first, over_second});
CHECK_THROWS_WITH_AS(_ = json::from_ubjson(input), budget_message, json::out_of_range&);
}
SECTION("every input adapter applies the budget")
{
const auto input = valueless_arrays('Z', {over_first, over_second});
// stream; not strict, which does not matter
std::stringstream stream;
stream.write(reinterpret_cast<const char*>(input.data()), static_cast<std::streamsize>(input.size()));
ValuelessEventCounter from_stream;
CHECK(!json::sax_parse(stream, &from_stream, json::input_format_t::ubjson, false));
CHECK(from_stream.error_id == 408);
// a container that is not contiguous; the counts of arrays of
// different types are added up
std::vector<std::uint8_t> mixed = {'['};
append_valueless_array(mixed, 'T', over_first);
append_valueless_array(mixed, 'F', over_second);
mixed.push_back(']');
const std::list<std::uint8_t> as_list(mixed.begin(), mixed.end());
ValuelessEventCounter from_list;
CHECK(!json::sax_parse(as_list.begin(), as_list.end(), &from_list, json::input_format_t::ubjson));
CHECK(from_list.error_id == 408);
CHECK(from_list.values == over_first);
// FILE*
FILE* const file = std::tmpfile(); // NOLINT(cppcoreguidelines-owning-memory)
REQUIRE(file != nullptr);
CHECK(std::fwrite(input.data(), 1, input.size(), file) == input.size());
std::rewind(file);
ValuelessEventCounter from_file;
CHECK(!json::sax_parse(file, &from_file, json::input_format_t::ubjson));
CHECK(from_file.error_id == 408);
std::fclose(file); // NOLINT(cert-err33-c,cppcoreguidelines-owning-memory)
}
SECTION("the limit is exact and the bytes read raise it")
{
// [ [$Z#l 524288] [$U#l 4096 + 4096 bytes] [$Z#l count] ]: chars_read
// is 1 + 9 + (9 + 4096) + 9 = 4124 when the last header has been read,
// so the last array may hold 4 * 4124 = 16496 values on top of the
// base of 1048576 less the 524288 of the first array
const std::uint32_t last_allowed = 1048576 + 16496 - 524288;
for (const std::uint32_t count :
{
last_allowed, last_allowed + 1
})
{
CAPTURE(count)
std::vector<std::uint8_t> input = {'['};
append_valueless_array(input, 'Z', 524288);
input.insert(input.end(), {'[', '$', 'U', '#', 'l', 0x00, 0x00, 0x10, 0x00});
input.insert(input.end(), 4096, 0x01);
append_valueless_array(input, 'Z', count);
input.push_back(']');
ValuelessEventCounter sax;
const bool accepted = count == last_allowed;
CHECK(json::sax_parse(input, &sax, json::input_format_t::ubjson) == accepted);
CHECK(sax.error_id == (accepted ? 0 : 408));
CHECK(sax.values == 524288u + 4096u + (accepted ? count : 0u));
}
// an array of 1048576 values on its own is accepted as before
const std::vector<std::uint8_t> single = {'[', '$', 'Z', '#', 'l', 0x00, 0x10, 0x00, 0x00};
// (the handler ends the parse at the first value, so that the million
// values are not read)
ValuelessEventCounter sax;
sax.stop_after = 1;
CHECK(!json::sax_parse(single, &sax, json::input_format_t::ubjson));
CHECK(sax.error_id == 0);
CHECK(sax.values == 1);
}
SECTION("to_ubjson writes the typed form up to the base only")
{
// 1048 rows of 1000 values fit under the base of 1048576, the 1049th
// would not: its elements are written one by one. Written all typed,
// 1100 rows of 6 bytes would be refused by a reader (1075 rows are the
// most it accepts). The rows hold null, true or false, and the
// fallback does not depend on which
// 1100 rows of 6 bytes would be refused by a reader with the default
// rate of the macro JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE (1074 rows
// are the most it accepts); the writer does not follow the macro, since
// the limit of a reader is never below the base. The rows hold null,
// true or false, and the fallback does not depend on which
std::vector<std::uint8_t> encoded;
{
json table = json::array();
@@ -2658,7 +2469,7 @@ TEST_CASE("UBJSON the valueless elements of a whole input are bounded")
CHECK(encoded.size() == 7 + (1048 * 6) + (52 * (4 + 1000)));
// the output is read back
ValuelessEventCounter sax;
utils::ValuelessEventCounter sax;
CHECK(json::sax_parse(encoded, &sax, json::input_format_t::ubjson));
CHECK(sax.error_id == 0);
CHECK(sax.values == 1100u * 1000u);
@@ -2685,7 +2496,7 @@ TEST_CASE("UBJSON the valueless elements of a whole input are bounded")
// an object member costs a key, so the count is bounded by the input
// and is not charged to the budget
const std::vector<std::uint8_t> input = {'{', '$', 'Z', '#', 'l', 0x00, 0x10, 0x00, 0x00};
ValuelessEventCounter sax;
utils::ValuelessEventCounter sax;
CHECK(!json::sax_parse(input, &sax, json::input_format_t::ubjson));
CHECK(sax.error_id == 110);
CHECK(sax.values == 0);
tests/src/unit-ubjson_valueless.cpp
+324
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@@ -0,0 +1,324 @@
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++ (supporting code)
// | | |__ | | | | | | version 3.12.0
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
//
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT
// The budget for the elements of the UBJSON containers of a valueless type
// ('Z', 'T', 'F') of a whole input: 1048576 plus
// JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE for every byte read (see
// docs/mkdocs/docs/api/macros/json_ubjson_valueless_elements_per_byte.md).
//
// The file is built several times, with the macro defined to other values (see
// tests/CMakeLists.txt), and every boundary below is computed from the macro.
// What it can test depends on the value: with a rate of at most 10000 the
// budget can be reached with the few bytes of a test, so the tests exceed it
// at the exact byte; with a rate of 131072 or more the budget cannot be reached
// by an input of any size (see the macro's page: 2^20 / 8 = 131072 elements per
// byte is what the shortest header of a container of the largest size allows), and
// the tests check that nothing is refused, in particular that the limit does
// not wrap around for a rate near the largest integer. The input is read with
// a SAX handler that counts the values, because a DOM of a million values is
// what makes such a test slow under Valgrind.
#include "doctest_compatibility.h"
#include <nlohmann/json.hpp>
using nlohmann::json;
#include <cstddef> // size_t
#include <cstdio> // FILE, tmpfile, fwrite, fseek, fclose
#include <cstdint> // uint8_t, uint32_t
#include <list>
#include <sstream>
#include <vector>
#include "ubjson_valueless.hpp"
using utils::ValuelessEventCounter;
using utils::valueless_arrays;
#ifndef JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE
#error "this test needs the macro: compile it with JSON_TEST_KEEP_MACROS (see tests/CMakeLists.txt)"
#endif
namespace
{
/// the base of the budget and the limit of a single container: both 2^20
constexpr std::uint32_t budget_base = 1048576;
#if JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE <= 10000 || JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE >= 131072
/// what version 3.12.0 wrote for a table of @a rows (at most 32767) rows of
/// @a width nulls with to_ubjson(table, true, true): `[$[#I` and the count of
/// the rows (7 bytes), then a row as `$Z#` and its count (`U` and 1 byte up to
/// 255, `I` and 2 bytes up to 32767, `l` and 4 bytes above): 5, 6 or 8 bytes
std::vector<std::uint8_t> rows_3_12_0(const std::uint32_t rows, const std::uint32_t width)
{
std::vector<std::uint8_t> v = {'[', '$', '[', '#', 'I', static_cast<std::uint8_t>(rows >> 8), static_cast<std::uint8_t>(rows)};
for (std::uint32_t row = 0; row < rows; ++row)
{
v.push_back('$');
v.push_back('Z');
v.push_back('#');
if (width <= 255)
{
v.push_back('U');
}
else if (width <= 32767)
{
v.push_back('I');
v.push_back(static_cast<std::uint8_t>(width >> 8));
}
else
{
v.push_back('l');
v.push_back(static_cast<std::uint8_t>(width >> 24));
v.push_back(static_cast<std::uint8_t>(width >> 16));
v.push_back(static_cast<std::uint8_t>(width >> 8));
}
v.push_back(static_cast<std::uint8_t>(width));
}
return v;
}
#endif
} // namespace
// the macro must not be a character or bool: every character type is refused
static_assert(nlohmann::detail::valueless_elements_rate_is_char_or_bool<bool>::value, "bool is refused");
static_assert(nlohmann::detail::valueless_elements_rate_is_char_or_bool<char>::value, "char is refused");
static_assert(nlohmann::detail::valueless_elements_rate_is_char_or_bool<signed char>::value, "signed char is refused");
static_assert(nlohmann::detail::valueless_elements_rate_is_char_or_bool<unsigned char>::value, "unsigned char is refused");
static_assert(nlohmann::detail::valueless_elements_rate_is_char_or_bool<wchar_t>::value, "wchar_t is refused");
static_assert(nlohmann::detail::valueless_elements_rate_is_char_or_bool<char16_t>::value, "char16_t is refused");
static_assert(nlohmann::detail::valueless_elements_rate_is_char_or_bool<char32_t>::value, "char32_t is refused");
#if defined(__cpp_char8_t)
static_assert(nlohmann::detail::valueless_elements_rate_is_char_or_bool<char8_t>::value, "char8_t is refused");
#endif
static_assert(!nlohmann::detail::valueless_elements_rate_is_char_or_bool<int>::value, "int is accepted");
static_assert(!nlohmann::detail::valueless_elements_rate_is_char_or_bool<unsigned long long>::value, "unsigned long long is accepted");
TEST_CASE("UBJSON the limit of a single container does not depend on the macro")
{
#if !defined(JSON_NOEXCEPTION)
json _;
SECTION("a container of more than 1048576 elements is refused")
{
// the first check of every container; its message differs from that of
// the budget, so that it is clear which limit was exceeded
for (const char marker :
{'Z', 'T', 'F'
})
{
const auto input = valueless_arrays(marker, {budget_base + 1});
CHECK_THROWS_WITH_AS(_ = json::from_ubjson(input), "[json.exception.out_of_range.408] syntax error while parsing UBJSON size: excessive array size", json::out_of_range&);
}
}
#endif
SECTION("a container of 1048576 elements is accepted at the start of an input")
{
// whatever the rate: the base is the per-container limit. The handler
// ends the parse at the first value, so that the million values are
// not read
const std::vector<std::uint8_t> single = {'[', '$', 'Z', '#', 'l', 0x00, 0x10, 0x00, 0x00};
ValuelessEventCounter sax;
sax.stop_after = 1;
CHECK(!json::sax_parse(single, &sax, json::input_format_t::ubjson));
CHECK(sax.error_id == 0);
CHECK(sax.values == 1);
}
}
#if JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE <= 10000
namespace
{
/// the rate of the build; at most 10000 here, which the boundaries rely on
constexpr std::uint32_t rate = JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE;
/// elements of the first of two containers; the second one is then refused at
/// its header, which is read at byte 1 + 9 + 9 = 19
constexpr std::uint32_t first_count = 524288;
/// the largest count the second container may have at byte 19: base plus rate
/// for each of the 19 bytes, less what the first one used. For a rate of at
/// most 27594, the largest that keeps this within the limit of one container
constexpr std::uint32_t second_allowed = budget_base - first_count + (19 * rate);
} // namespace
TEST_CASE("UBJSON the valueless elements of a whole input are bounded")
{
// The per-container limit alone let nine bytes (`[$Z#l` and a count of
// 1048576) announce a million values, and every further nine bytes another
// million. The elements of all containers of type 'Z', 'T' or 'F' in one
// input are added up: they may not exceed 1048576 plus
// JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE for every byte read when the
// container's header has been read.
#if !defined(JSON_NOEXCEPTION)
json _;
const char* const budget_message = "[json.exception.out_of_range.408] syntax error while parsing UBJSON size: excessive number of elements without payload";
#endif
SECTION("the input of the original report is rejected")
{
// the second array is the first one that is refused, by one element
#if !defined(JSON_NOEXCEPTION)
CHECK_THROWS_WITH_AS(_ = json::from_ubjson(valueless_arrays('Z', {first_count, second_allowed + 1})), budget_message, json::out_of_range&);
#endif
// and is accepted with one element less
ValuelessEventCounter sax;
CHECK(json::sax_parse(valueless_arrays('Z', {first_count, second_allowed}), &sax, json::input_format_t::ubjson));
CHECK(sax.values == first_count + second_allowed);
}
SECTION("every input adapter applies the budget")
{
const auto input = valueless_arrays('Z', {first_count, second_allowed + 1});
// stream; not strict, which does not matter
std::stringstream stream;
stream.write(reinterpret_cast<const char*>(input.data()), static_cast<std::streamsize>(input.size()));
ValuelessEventCounter from_stream;
CHECK(!json::sax_parse(stream, &from_stream, json::input_format_t::ubjson, false));
CHECK(from_stream.error_id == 408);
// a container that is not contiguous; the counts of arrays of
// different types are added up
std::vector<std::uint8_t> mixed = {'['};
utils::append_valueless_array(mixed, 'T', first_count);
utils::append_valueless_array(mixed, 'F', second_allowed + 1);
mixed.push_back(']');
const std::list<std::uint8_t> as_list(mixed.begin(), mixed.end());
ValuelessEventCounter from_list;
CHECK(!json::sax_parse(as_list.begin(), as_list.end(), &from_list, json::input_format_t::ubjson));
CHECK(from_list.error_id == 408);
CHECK(from_list.values == first_count);
// FILE*
FILE* const file = std::tmpfile(); // NOLINT(cppcoreguidelines-owning-memory)
REQUIRE(file != nullptr);
CHECK(std::fwrite(input.data(), 1, input.size(), file) == input.size());
CHECK(std::fseek(file, 0, SEEK_SET) == 0);
ValuelessEventCounter from_file;
CHECK(!json::sax_parse(file, &from_file, json::input_format_t::ubjson));
CHECK(from_file.error_id == 408);
std::fclose(file); // NOLINT(cert-err33-c,cppcoreguidelines-owning-memory)
}
SECTION("the limit is exact and the bytes read raise it")
{
// [ [$Z#l first_count] [$U#l payload + payload bytes] [$Z#l count] ]:
// chars_read is 1 + 9 + (9 + payload) + 9 = 28 + payload when the last
// header has been read, so the last array may hold
// rate * (28 + payload) values on top of the base less the
// first_count of the first array. The payload is as large as the
// limit of one container allows, but at most 4096
constexpr std::uint32_t payload_limit = (524288 / rate) - 40;
constexpr std::uint32_t payload = payload_limit < 4096 ? payload_limit : 4096;
constexpr std::uint32_t last_allowed = budget_base - first_count + (rate * (28 + payload));
static_assert(last_allowed < budget_base, "the count must be accepted by the limit of one container");
for (const std::uint32_t count :
{
last_allowed, last_allowed + 1
})
{
CAPTURE(count)
std::vector<std::uint8_t> input = {'['};
utils::append_valueless_array(input, 'Z', first_count);
input.insert(input.end(), {'[', '$', 'U', '#', 'l',
static_cast<std::uint8_t>(payload >> 24), static_cast<std::uint8_t>(payload >> 16),
static_cast<std::uint8_t>(payload >> 8), static_cast<std::uint8_t>(payload)
});
input.insert(input.end(), payload, 0x01);
utils::append_valueless_array(input, 'Z', count);
input.push_back(']');
ValuelessEventCounter sax;
const bool accepted = count == last_allowed;
CHECK(json::sax_parse(input, &sax, json::input_format_t::ubjson) == accepted);
CHECK(sax.error_id == (accepted ? 0 : 408));
CHECK(sax.values == first_count + payload + (accepted ? count : 0u));
}
}
SECTION("a table written by 3.12.0")
{
// Version 3.12.0 wrote a table of rows of nulls with one `$Z#` header
// per row (see the macro's page). A row of `width` elements has a
// header of 6 bytes up to 32767 elements (5 up to 255), so the budget
// grows by 6 * rate per row, and the row brings `width`. The 7 bytes
// of the outer header are read first. Row r is accepted while
// r * width <= 1048576 + rate * (7 + 6 * r),
// which is r <= (1048576 + 7 * rate) / (width - 6 * rate) for a width
// above 6 * rate, and always true otherwise.
constexpr std::uint32_t width = 1000;
constexpr std::uint32_t rows = 1200;
constexpr std::uint32_t credit = 6 * rate;
constexpr std::uint32_t accepted_rows = width > credit ? (budget_base + (7 * rate)) / (width - credit) : rows;
constexpr std::uint32_t read_rows = accepted_rows < rows ? accepted_rows : rows;
ValuelessEventCounter sax;
CHECK(json::sax_parse(rows_3_12_0(rows, width), &sax, json::input_format_t::ubjson) == (accepted_rows >= rows));
CHECK(sax.error_id == (accepted_rows >= rows ? 0 : 408));
CHECK(sax.values == static_cast<std::size_t>(read_rows) * width);
}
}
#elif JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE >= 131072
TEST_CASE("UBJSON a rate that cannot be reached switches the budget off")
{
// The rate is so large (2^20 / 8 = 131072 elements per byte or more)
// that no input can exceed the budget: the shortest header of a container
// of the largest size is 8 bytes (`$Z#l` and a count of 4 bytes, in an
// array of arrays). The limit is base + rate * bytes read, which wraps
// around for a rate near the largest integer in 64 and in 32
// bits already at the first byte, unless it saturates: a wrapped limit
// would refuse the second container below (at byte 19 or at byte 10, where
// a limit of 2^20 + 10 * rate wraps for a 32-bit rate of 0x7FFFFFFF).
#if !defined(JSON_NOEXCEPTION)
json _;
#endif
SECTION("containers of the largest size are accepted one after the other")
{
// the first container is accepted by the base alone, the second one is
// not: it needs the rate. The handler ends the parse at its first
// value, so that the second million values are not read
const auto input = valueless_arrays('Z', {budget_base, budget_base});
ValuelessEventCounter sax;
sax.stop_after = static_cast<std::size_t>(budget_base) + 1;
CHECK(!json::sax_parse(input, &sax, json::input_format_t::ubjson));
CHECK(sax.error_id == 0);
CHECK(sax.values == static_cast<std::size_t>(budget_base) + 1);
}
SECTION("the limit of a single container still applies")
{
const auto input = valueless_arrays('T', {budget_base, budget_base + 1});
ValuelessEventCounter sax;
CHECK(!json::sax_parse(input, &sax, json::input_format_t::ubjson));
CHECK(sax.error_id == 408);
CHECK(sax.values == budget_base);
#if !defined(JSON_NOEXCEPTION)
CHECK_THROWS_WITH_AS(_ = json::from_ubjson(valueless_arrays('F', {budget_base + 1})), "[json.exception.out_of_range.408] syntax error while parsing UBJSON size: excessive array size", json::out_of_range&);
#endif
}
SECTION("a table written by 3.12.0 is read completely")
{
// 1200 rows of 1000 values are refused after 1074 rows at the default
// rate and are accepted with every rate of 167 and more
ValuelessEventCounter sax;
CHECK(json::sax_parse(rows_3_12_0(1200, 1000), &sax, json::input_format_t::ubjson));
CHECK(sax.error_id == 0);
CHECK(sax.values == 1200u * 1000u);
}
}
// (rates from 10001 to 131071 can be reached, but not with the few bytes of a
// test: there is nothing to test for them here)
#endif