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Merge pull request #1261 from fmalita/exponent-underflow

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Prevent int underflow when parsing exponents
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Milo Yip 2018-05-20 13:42:13 +08:00 committed by GitHub
commit af223d44f4
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2 changed files with 11 additions and 1 deletions
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11
include/rapidjson/reader.h
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@ -1632,9 +1632,18 @@ private:
if (RAPIDJSON_LIKELY(s.Peek() >= '0' && s.Peek() <= '9')) { if (RAPIDJSON_LIKELY(s.Peek() >= '0' && s.Peek() <= '9')) {
exp = static_cast<int>(s.Take() - '0'); exp = static_cast<int>(s.Take() - '0');
if (expMinus) { if (expMinus) {
// (exp + expFrac) must not underflow int => we're detecting when -exp gets
// dangerously close to INT_MIN (a pessimistic next digit 9 would push it into
// underflow territory):
//
// -(exp * 10 + 9) + expFrac >= INT_MIN
// <=> exp <= (expFrac - INT_MIN - 9) / 10
RAPIDJSON_ASSERT(expFrac <= 0);
int maxExp = (expFrac + 2147483639) / 10;
while (RAPIDJSON_LIKELY(s.Peek() >= '0' && s.Peek() <= '9')) { while (RAPIDJSON_LIKELY(s.Peek() >= '0' && s.Peek() <= '9')) {
exp = exp * 10 + static_cast<int>(s.Take() - '0'); exp = exp * 10 + static_cast<int>(s.Take() - '0');
if (exp >= 214748364) { // Issue #313: prevent overflow exponent if (RAPIDJSON_UNLIKELY(exp > maxExp)) {
while (RAPIDJSON_UNLIKELY(s.Peek() >= '0' && s.Peek() <= '9')) // Consume the rest of exponent while (RAPIDJSON_UNLIKELY(s.Peek() >= '0' && s.Peek() <= '9')) // Consume the rest of exponent
s.Take(); s.Take();
} }

1
test/unittest/readertest.cpp
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@ -242,6 +242,7 @@ static void TestParseDouble() {
TEST_DOUBLE(fullPrecision, "1e-214748363", 0.0); // Maximum supported negative exponent TEST_DOUBLE(fullPrecision, "1e-214748363", 0.0); // Maximum supported negative exponent
TEST_DOUBLE(fullPrecision, "1e-214748364", 0.0); TEST_DOUBLE(fullPrecision, "1e-214748364", 0.0);
TEST_DOUBLE(fullPrecision, "1e-21474836311", 0.0); TEST_DOUBLE(fullPrecision, "1e-21474836311", 0.0);
TEST_DOUBLE(fullPrecision, "1.00000000001e-2147483638", 0.0);
TEST_DOUBLE(fullPrecision, "0.017976931348623157e+310", 1.7976931348623157e+308); // Max double in another form TEST_DOUBLE(fullPrecision, "0.017976931348623157e+310", 1.7976931348623157e+308); // Max double in another form
// Since // Since