60 lines
2.8 KiB
Diff
60 lines
2.8 KiB
Diff
From 8269bc2bc289e9d343bae51cdf6d23ef0950e001 Mon Sep 17 00:00:00 2001
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From: Florin Malita <fmalita@gmail.com>
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Date: Tue, 15 May 2018 22:48:07 -0400
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Subject: [PATCH] Prevent int underflow when parsing exponents
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When parsing negative exponents, the current implementation takes
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precautions for |exp| to not underflow int.
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But that is not sufficient: later on [1], |exp + expFrac| is also
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stored to an int - so we must ensure that the sum stays within int
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representable values.
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Update the exp clamping logic to take expFrac into account.
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[1] https://github.com/Tencent/rapidjson/blob/master/include/rapidjson/reader.h#L1690
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---
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include/rapidjson/reader.h | 11 ++++++++++-
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test/unittest/readertest.cpp | 1 +
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2 files changed, 11 insertions(+), 1 deletion(-)
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diff --git a/include/rapidjson/reader.h b/include/rapidjson/reader.h
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index 7441eda4..f95aef42 100644
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--- a/include/rapidjson/reader.h
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+++ b/include/rapidjson/reader.h
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@@ -1632,9 +1632,18 @@ private:
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if (RAPIDJSON_LIKELY(s.Peek() >= '0' && s.Peek() <= '9')) {
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exp = static_cast<int>(s.Take() - '0');
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if (expMinus) {
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+ // (exp + expFrac) must not underflow int => we're detecting when -exp gets
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+ // dangerously close to INT_MIN (a pessimistic next digit 9 would push it into
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+ // underflow territory):
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+ //
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+ // -(exp * 10 + 9) + expFrac >= INT_MIN
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+ // <=> exp <= (expFrac - INT_MIN - 9) / 10
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+ RAPIDJSON_ASSERT(expFrac <= 0);
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+ int maxExp = (expFrac + 2147483639) / 10;
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+
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while (RAPIDJSON_LIKELY(s.Peek() >= '0' && s.Peek() <= '9')) {
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exp = exp * 10 + static_cast<int>(s.Take() - '0');
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- if (exp >= 214748364) { // Issue #313: prevent overflow exponent
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+ if (RAPIDJSON_UNLIKELY(exp > maxExp)) {
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while (RAPIDJSON_UNLIKELY(s.Peek() >= '0' && s.Peek() <= '9')) // Consume the rest of exponent
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s.Take();
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}
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diff --git a/test/unittest/readertest.cpp b/test/unittest/readertest.cpp
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index e5308019..c4800b93 100644
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--- a/test/unittest/readertest.cpp
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+++ b/test/unittest/readertest.cpp
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@@ -242,6 +242,7 @@ static void TestParseDouble() {
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TEST_DOUBLE(fullPrecision, "1e-214748363", 0.0); // Maximum supported negative exponent
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TEST_DOUBLE(fullPrecision, "1e-214748364", 0.0);
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TEST_DOUBLE(fullPrecision, "1e-21474836311", 0.0);
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+ TEST_DOUBLE(fullPrecision, "1.00000000001e-2147483638", 0.0);
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TEST_DOUBLE(fullPrecision, "0.017976931348623157e+310", 1.7976931348623157e+308); // Max double in another form
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// Since
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--
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2.20.1
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