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[C++] fix bounds checking on integer parsing (#4250)

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* fix bounds checking on integer parsing

the previous code was allowing 255 for int8_t, similar for int16_t
and int32_t, and even negative values for unsignd types.

this patch fixes bounds checking for 8-bit, 16-bit and 32-bit types.
testing for both acceptable values and unacceptable values at the
boundaries are also improved.

bounds checking on 64-bit types isn't addressed by this patch.

* fix 'unary minus operator applied to unsigned type, result still unsigned'

* fix & placement
This commit is contained in:
Jason Stubbs
2017-04-18 04:19:43 +10:00
committed by Wouter van Oortmerssen
parent b90d4e049d
commit a07f0d428d
3 changed files with 47 additions and 24 deletions
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2
include/flatbuffers/idl.h
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@@ -530,7 +530,7 @@ class Parser : public ParserState {
// of the schema provided. Returns non-empty error on any problems. // of the schema provided. Returns non-empty error on any problems.
std::string ConformTo(const Parser &base); std::string ConformTo(const Parser &base);
FLATBUFFERS_CHECKED_ERROR CheckBitsFit(int64_t val, size_t bits); FLATBUFFERS_CHECKED_ERROR CheckInRange(int64_t val, int64_t min, int64_t max);
private: private:
FLATBUFFERS_CHECKED_ERROR Error(const std::string &msg); FLATBUFFERS_CHECKED_ERROR Error(const std::string &msg);

29
src/idl_parser.cpp
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@@ -86,26 +86,29 @@ CheckedError Parser::Error(const std::string &msg) {
inline CheckedError NoError() { return CheckedError(false); } inline CheckedError NoError() { return CheckedError(false); }
inline std::string OutOfRangeErrorMsg(int64_t val, const std::string &op,
int64_t limit) {
const std::string cause = NumToString(val) + op + NumToString(limit);
return "constant does not fit (" + cause + ")";
}
// Ensure that integer values we parse fit inside the declared integer type. // Ensure that integer values we parse fit inside the declared integer type.
CheckedError Parser::CheckBitsFit(int64_t val, size_t bits) { CheckedError Parser::CheckInRange(int64_t val, int64_t min, int64_t max) {
// Left-shifting a 64-bit value by 64 bits or more is undefined if (val < min)
// behavior (C99 6.5.7), so check *before* we shift. return Error(OutOfRangeErrorMsg(val, " < ", min));
if (bits < 64) { else if (val > max)
// Bits we allow to be used. return Error(OutOfRangeErrorMsg(val, " > ", max));
auto mask = static_cast<int64_t>((1ull << bits) - 1); else
if ((val & ~mask) != 0 && // Positive or unsigned. return NoError();
(val | mask) != -1) // Negative.
return Error("constant does not fit in a " + NumToString(bits) +
"-bit field");
}
return NoError();
} }
// atot: templated version of atoi/atof: convert a string to an instance of T. // atot: templated version of atoi/atof: convert a string to an instance of T.
template<typename T> inline CheckedError atot(const char *s, Parser &parser, template<typename T> inline CheckedError atot(const char *s, Parser &parser,
T *val) { T *val) {
int64_t i = StringToInt(s); int64_t i = StringToInt(s);
ECHECK(parser.CheckBitsFit(i, sizeof(T) * 8)); const int64_t min = std::numeric_limits<T>::min();
const int64_t max = std::numeric_limits<T>::max();
ECHECK(parser.CheckInRange(i, min, max));
*val = (T)i; *val = (T)i;
return NoError(); return NoError();
} }

40
tests/test.cpp
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@@ -981,7 +981,7 @@ void TestError(const char *src, const char *error_substr,
// Also useful for coverage, making sure these paths are run. // Also useful for coverage, making sure these paths are run.
void ErrorTest() { void ErrorTest() {
// In order they appear in idl_parser.cpp // In order they appear in idl_parser.cpp
TestError("table X { Y:byte; } root_type X; { Y: 999 }", "bit field"); TestError("table X { Y:byte; } root_type X; { Y: 999 }", "does not fit");
TestError(".0", "floating point"); TestError(".0", "floating point");
TestError("\"\0", "illegal"); TestError("\"\0", "illegal");
TestError("\"\\q", "escape code"); TestError("\"\\q", "escape code");
@@ -1069,32 +1069,51 @@ void EnumStringsTest() {
} }
void IntegerOutOfRangeTest() { void IntegerOutOfRangeTest() {
TestError("table T { F:byte; } root_type T; { F:256 }", TestError("table T { F:byte; } root_type T; { F:128 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:byte; } root_type T; { F:-257 }", TestError("table T { F:byte; } root_type T; { F:-129 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:ubyte; } root_type T; { F:256 }", TestError("table T { F:ubyte; } root_type T; { F:256 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:ubyte; } root_type T; { F:-257 }", TestError("table T { F:ubyte; } root_type T; { F:-1 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:short; } root_type T; { F:65536 }", TestError("table T { F:short; } root_type T; { F:32768 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:short; } root_type T; { F:-65537 }", TestError("table T { F:short; } root_type T; { F:-32769 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:ushort; } root_type T; { F:65536 }", TestError("table T { F:ushort; } root_type T; { F:65536 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:ushort; } root_type T; { F:-65537 }", TestError("table T { F:ushort; } root_type T; { F:-1 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:int; } root_type T; { F:4294967296 }", TestError("table T { F:int; } root_type T; { F:2147483648 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:int; } root_type T; { F:-4294967297 }", TestError("table T { F:int; } root_type T; { F:-2147483649 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:uint; } root_type T; { F:4294967296 }", TestError("table T { F:uint; } root_type T; { F:4294967296 }",
"constant does not fit"); "constant does not fit");
TestError("table T { F:uint; } root_type T; { F:-4294967297 }", TestError("table T { F:uint; } root_type T; { F:-1 }",
"constant does not fit"); "constant does not fit");
} }
void IntegerBoundaryTest() {
TEST_EQ(TestValue<int8_t>("{ Y:127 }","byte"), 127);
TEST_EQ(TestValue<int8_t>("{ Y:-128 }","byte"), -128);
TEST_EQ(TestValue<uint8_t>("{ Y:255 }","ubyte"), 255);
TEST_EQ(TestValue<uint8_t>("{ Y:0 }","ubyte"), 0);
TEST_EQ(TestValue<int16_t>("{ Y:32767 }","short"), 32767);
TEST_EQ(TestValue<int16_t>("{ Y:-32768 }","short"), -32768);
TEST_EQ(TestValue<uint16_t>("{ Y:65535 }","ushort"), 65535);
TEST_EQ(TestValue<uint16_t>("{ Y:0 }","ushort"), 0);
TEST_EQ(TestValue<int32_t>("{ Y:2147483647 }","int"), 2147483647);
TEST_EQ(TestValue<int32_t>("{ Y:-2147483648 }","int"), (-2147483647 - 1));
TEST_EQ(TestValue<uint32_t>("{ Y:4294967295 }","uint"), 4294967295);
TEST_EQ(TestValue<uint32_t>("{ Y:0 }","uint"), 0);
TEST_EQ(TestValue<int64_t>("{ Y:9223372036854775807 }","long"), 9223372036854775807);
TEST_EQ(TestValue<int64_t>("{ Y:-9223372036854775808 }","long"), (-9223372036854775807 - 1));
TEST_EQ(TestValue<uint64_t>("{ Y:18446744073709551615 }","ulong"), 18446744073709551615U);
TEST_EQ(TestValue<uint64_t>("{ Y:0 }","ulong"), 0);
}
void UnicodeTest() { void UnicodeTest() {
flatbuffers::Parser parser; flatbuffers::Parser parser;
// Without setting allow_non_utf8 = true, we treat \x sequences as byte sequences // Without setting allow_non_utf8 = true, we treat \x sequences as byte sequences
@@ -1515,6 +1534,7 @@ int main(int /*argc*/, const char * /*argv*/[]) {
ValueTest(); ValueTest();
EnumStringsTest(); EnumStringsTest();
IntegerOutOfRangeTest(); IntegerOutOfRangeTest();
IntegerBoundaryTest();
UnicodeTest(); UnicodeTest();
UnicodeTestAllowNonUTF8(); UnicodeTestAllowNonUTF8();
UnicodeTestGenerateTextFailsOnNonUTF8(); UnicodeTestGenerateTextFailsOnNonUTF8();