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reject unpaired UTF-16 surrogates in wide-string input (#5276)

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Angadi56
2026-07-19 22:03:42 +05:30
committed by GitHub
parent a03e65420c
commit 1c5a953de5
3 changed files with 75 additions and 17 deletions
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include/nlohmann/detail/input/input_adapters.hpp
+21 -8
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@@ -395,17 +395,30 @@ struct wide_string_input_helper<BaseInputAdapter, 2>
}
else
{
if (JSON_HEDLEY_UNLIKELY(!input.empty()))
// A supplementary code point is a high surrogate (0xD800..0xDBFF)
// followed by a low surrogate (0xDC00..0xDFFF). A lone low
// surrogate, a high surrogate at the end of the input, or a high
// surrogate followed by any other unit is malformed UTF-16. In
// that case the offending unit is passed through unchanged so the
// UTF-8 decoder rejects it, matching how \uXXXX surrogate escapes
// are handled in the lexer.
bool valid_pair = false;
if (wc <= 0xDBFF && JSON_HEDLEY_UNLIKELY(!input.empty()))
{
const auto wc2 = static_cast<unsigned int>(input.get_character());
const auto charcode = 0x10000u + (((static_cast<unsigned int>(wc) & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | (charcode >> 18u));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 12u) & 0x3Fu));
utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 6u) & 0x3Fu));
utf8_bytes[3] = static_cast<std::char_traits<char>::int_type>(0x80u | (charcode & 0x3Fu));
utf8_bytes_filled = 4;
if (0xDC00 <= wc2 && wc2 <= 0xDFFF)
{
const auto charcode = 0x10000u + (((static_cast<unsigned int>(wc) & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | (charcode >> 18u));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 12u) & 0x3Fu));
utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 6u) & 0x3Fu));
utf8_bytes[3] = static_cast<std::char_traits<char>::int_type>(0x80u | (charcode & 0x3Fu));
utf8_bytes_filled = 4;
valid_pair = true;
}
}
else
if (!valid_pair)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(wc);
utf8_bytes_filled = 1;
single_include/nlohmann/json.hpp
+21 -8
View File
@@ -7382,17 +7382,30 @@ struct wide_string_input_helper<BaseInputAdapter, 2>
}
else
{
if (JSON_HEDLEY_UNLIKELY(!input.empty()))
// A supplementary code point is a high surrogate (0xD800..0xDBFF)
// followed by a low surrogate (0xDC00..0xDFFF). A lone low
// surrogate, a high surrogate at the end of the input, or a high
// surrogate followed by any other unit is malformed UTF-16. In
// that case the offending unit is passed through unchanged so the
// UTF-8 decoder rejects it, matching how \uXXXX surrogate escapes
// are handled in the lexer.
bool valid_pair = false;
if (wc <= 0xDBFF && JSON_HEDLEY_UNLIKELY(!input.empty()))
{
const auto wc2 = static_cast<unsigned int>(input.get_character());
const auto charcode = 0x10000u + (((static_cast<unsigned int>(wc) & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | (charcode >> 18u));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 12u) & 0x3Fu));
utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 6u) & 0x3Fu));
utf8_bytes[3] = static_cast<std::char_traits<char>::int_type>(0x80u | (charcode & 0x3Fu));
utf8_bytes_filled = 4;
if (0xDC00 <= wc2 && wc2 <= 0xDFFF)
{
const auto charcode = 0x10000u + (((static_cast<unsigned int>(wc) & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | (charcode >> 18u));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 12u) & 0x3Fu));
utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 6u) & 0x3Fu));
utf8_bytes[3] = static_cast<std::char_traits<char>::int_type>(0x80u | (charcode & 0x3Fu));
utf8_bytes_filled = 4;
valid_pair = true;
}
}
else
if (!valid_pair)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(wc);
utf8_bytes_filled = 1;
tests/src/unit-wstring.cpp
+33 -1
View File
@@ -53,6 +53,27 @@ TEST_CASE("wide strings")
std::wstring const w = L"\"\xDBFF";
json _;
CHECK_THROWS_AS(_ = json::parse(w), json::parse_error&);
// the exact message depends on the width of wchar_t: a 16-bit
// wchar_t passes the lone surrogate to the UTF-8 decoder unchanged
// (rejected as a single ill-formed byte at column 2), while a
// 32-bit wchar_t first encodes it as an ill-formed three-byte
// sequence (rejected one byte later, at column 3)
const char* const error_low_surrogate = sizeof(wchar_t) == 2
? "[json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '\"<U+0000>'"
: "[json.exception.parse_error.101] parse error at line 1, column 3: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '\"\xED\xB0'";
const char* const error_high_surrogate = sizeof(wchar_t) == 2
? "[json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '\"<U+0000>'"
: "[json.exception.parse_error.101] parse error at line 1, column 3: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '\"\xED\xA0'";
// a lone low surrogate cannot start a pair
CHECK_THROWS_WITH_AS(_ = json::parse(std::wstring{L'"', static_cast<wchar_t>(0xDC00), L'"'}), error_low_surrogate, json::parse_error&);
// a high surrogate followed by a non-low-surrogate unit is invalid
CHECK_THROWS_WITH_AS(_ = json::parse(std::wstring{L'"', static_cast<wchar_t>(0xD800), L'a', L'"'}), error_high_surrogate, json::parse_error&);
// a lone low surrogate must not swallow the following unit: pairing
// it with any second unit would produce valid UTF-8, so the error
// has to report an ill-formed byte at the surrogate's own position
CHECK_THROWS_WITH_AS(_ = json::parse(std::wstring{L'"', static_cast<wchar_t>(0xDC00), L'a', L'"'}), error_low_surrogate, json::parse_error&);
}
}
@@ -68,11 +89,22 @@ TEST_CASE("wide strings")
SECTION("invalid std::u16string")
{
if (wstring_is_utf16())
if (u16string_is_utf16())
{
std::u16string const w = u"\"\xDBFF";
json _;
CHECK_THROWS_AS(_ = json::parse(w), json::parse_error&);
// a lone low surrogate cannot start a pair
CHECK_THROWS_WITH_AS(_ = json::parse(std::u16string{u'"', 0xDC00, u'"'}), "[json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '\"<U+0000>'", json::parse_error&);
// a high surrogate followed by a non-low-surrogate unit is invalid
CHECK_THROWS_WITH_AS(_ = json::parse(std::u16string{u'"', 0xD800, u'a', u'"'}), "[json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '\"<U+0000>'", json::parse_error&);
// a lone low surrogate must not swallow the following unit: pairing
// it with any second unit would produce valid UTF-8, so the error
// has to report an ill-formed byte at the surrogate's own position
CHECK_THROWS_WITH_AS(_ = json::parse(std::u16string{u'"', 0xDC00, u'a', u'"'}), "[json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '\"<U+0000>'", json::parse_error&);
// a valid surrogate pair is still decoded (U+1F600)
CHECK(json::parse(std::u16string{u'"', 0xD83D, 0xDE00, u'"'}).get<std::string>() == "\xF0\x9F\x98\x80");
}
}