Browse Source

Avoid possibility of overflow in DateTime parsing functions

* This is strictly undefined behavior so let's avoid it
* As a side-effect it is now possible to omit the separators in
  DateTime::fromIsoString()
master
Martchus 6 months ago
parent
commit
a116c9e790
  1. 40
      chrono/datetime.cpp
  2. 6
      tests/chronotests.cpp

40
chrono/datetime.cpp

@ -91,8 +91,7 @@ DateTime DateTime::fromString(const char *str)
miliSeconds += (c - '0') * miliSecondsFact;
miliSecondsFact /= 10;
} else {
*valueIndex *= 10;
*valueIndex += c - '0';
Detail::raiseAndAdd(*valueIndex, 10, c);
}
} else if ((c == '-' || c == ':' || c == '/') || (c == '.' && (valueIndex == secondsIndex)) || (c == ' ' && (valueIndex == dayIndex))) {
if (++valueIndex == valuesEnd) {
@ -101,7 +100,7 @@ DateTime DateTime::fromString(const char *str)
} else if (c == '\0') {
break;
} else {
throw ConversionException(argsToString("unexpected ", c));
throw ConversionException(argsToString("Unexpected character \"", c, '\"'));
}
}
return DateTime::fromDateAndTime(values[0], values[1], *dayIndex, values[3], values[4], *secondsIndex, miliSeconds);
@ -110,10 +109,11 @@ DateTime DateTime::fromString(const char *str)
/*!
* \brief Parses the specified ISO date time denotation provided as C-style string.
* \returns Returns a pair where the first value is the parsed date time and the second value
* a time span which can be subtracted from the first value to get the UTC time.
* \remarks Not all variants allowed by ISO 8601 are supported right now, eg. delimiters can not
* be omitted.
* The common form (something like "2016-08-29T21:32:31.588539814+02:00") is supported of course.
* the time zone designator (a time span which can be subtracted from the first value to get the UTC time).
* \remarks
* - Parsing durations and time intervals is *not* supported.
* - Truncated representations are *not* supported.
* - Standardised extensions (ISO 8601-2:2019) are *not* supported.
* \sa https://en.wikipedia.org/wiki/ISO_8601
*/
std::pair<DateTime, TimeSpan> DateTime::fromIsoString(const char *str)
@ -126,7 +126,9 @@ std::pair<DateTime, TimeSpan> DateTime::fromIsoString(const char *str)
int *const secondsIndex = values + 5;
int *const miliSecondsIndex = values + 6;
int *const deltaHourIndex = values + 7;
int *const valuesEnd = values + 9;
int *valueIndex = values;
unsigned int remainingDigits = 4;
bool deltaNegative = false;
double miliSecondsFact = 100.0, miliSeconds = 0.0;
for (const char *strIndex = str;; ++strIndex) {
@ -136,13 +138,21 @@ std::pair<DateTime, TimeSpan> DateTime::fromIsoString(const char *str)
miliSeconds += (c - '0') * miliSecondsFact;
miliSecondsFact /= 10;
} else {
if (!remainingDigits) {
if (++valueIndex == miliSecondsIndex || valueIndex >= valuesEnd) {
throw ConversionException("Max. number of digits exceeded");
}
remainingDigits = 2;
}
*valueIndex *= 10;
*valueIndex += c - '0';
remainingDigits -= 1;
}
} else if (c == 'T') {
if (++valueIndex != hourIndex) {
throw ConversionException("\"T\" expected before hour");
}
remainingDigits = 2;
} else if (c == '-') {
if (valueIndex < dayIndex) {
++valueIndex;
@ -150,34 +160,38 @@ std::pair<DateTime, TimeSpan> DateTime::fromIsoString(const char *str)
valueIndex = deltaHourIndex;
deltaNegative = true;
} else {
throw ConversionException("unexpected \"-\" after day");
throw ConversionException("Unexpected \"-\" after day");
}
remainingDigits = 2;
} else if (c == '.') {
if (valueIndex != secondsIndex) {
throw ConversionException("unexpected \".\"");
throw ConversionException("Unexpected \".\"");
} else {
++valueIndex;
}
} else if (c == ':') {
if (valueIndex < hourIndex) {
throw ConversionException("unexpected \":\" before hour");
throw ConversionException("Unexpected \":\" before hour");
} else if (valueIndex == secondsIndex) {
throw ConversionException("unexpected \":\" after second");
throw ConversionException("Unexpected \":\" after second");
} else {
++valueIndex;
}
remainingDigits = 2;
} else if ((c == '+') && (++valueIndex >= secondsIndex)) {
valueIndex = deltaHourIndex;
deltaNegative = false;
remainingDigits = 2;
} else if ((c == 'Z') && (++valueIndex >= secondsIndex)) {
valueIndex = deltaHourIndex + 2;
remainingDigits = 2;
} else if (c == '\0') {
break;
} else {
throw ConversionException(argsToString("unexpected \"", c, '\"'));
throw ConversionException(argsToString("Unexpected \"", c, '\"'));
}
}
auto delta(TimeSpan::fromMinutes(*deltaHourIndex * 60 + values[8]));
auto delta = TimeSpan::fromMinutes(*deltaHourIndex * 60 + values[8]);
if (deltaNegative) {
delta = TimeSpan(-delta.totalTicks());
}

6
tests/chronotests.cpp

@ -182,6 +182,12 @@ void ChronoTests::testDateTime()
const auto test7 = DateTime::fromIsoString("2021-05-20T23:02:45-04:00");
CPPUNIT_ASSERT_EQUAL_MESSAGE("no seconds fraction (negative timezone offset, 1)", DateTime::fromDateAndTime(2021, 5, 20, 23, 2, 45), test7.first);
CPPUNIT_ASSERT_EQUAL_MESSAGE("no seconds fraction (negative timezone offset, 2)", TimeSpan::fromHours(-4.0), test7.second);
// implied separators / too many digits
CPPUNIT_ASSERT_EQUAL_MESSAGE("no separators", test5.first - test5.second, DateTime::fromIsoStringGmt("20170823T194015.985077682-0230"));
CPPUNIT_ASSERT_EQUAL_MESSAGE(
"not even T separator", DateTime::fromDateAndTime(2017, 8, 23, 19, 40, 15), DateTime::fromIsoStringGmt("20170823194015"));
CPPUNIT_ASSERT_THROW_MESSAGE("too many digits after seconds", DateTime::fromIsoString("2017082319401516"), ConversionException);
CPPUNIT_ASSERT_THROW_MESSAGE("too many digits after timezone offset", DateTime::fromIsoString("20170823194015.16+02300"), ConversionException);
// test invalid characters
CPPUNIT_ASSERT_THROW_MESSAGE("digits after Z", DateTime::fromIsoString("2017-O8-23T19:40:15.985077682Z02:00"), ConversionException);
CPPUNIT_ASSERT_THROW_MESSAGE("invalid letter", DateTime::fromIsoString("2017-O8-23T19:40:15.985077682:+02:00"), ConversionException);

Loading…
Cancel
Save