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Fix UBSAN failure caused by left-shift of negative number #1921
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90434bb
Regression test for: https://github.com/Exiv2/exiv2/issues/1920
kevinbackhouse a71bb64
Credit to OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detai…
kevinbackhouse fc07f18
Add CodeQL query to detect variants of issue #1920.
kevinbackhouse 83b9944
We only need to extract one byte.
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,24 @@ | ||
/** | ||
* @name Signed shift | ||
* @description Shifting a negative number is undefined behavior, | ||
* so it is risky to shift a signed number. | ||
* @kind problem | ||
* @problem.severity warning | ||
* @id cpp/signed-shift | ||
* @tags security | ||
* external/cwe/cwe-758 | ||
*/ | ||
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// See the "Bitwise shift operators" section here: | ||
// https://en.cppreference.com/w/cpp/language/operator_arithmetic | ||
import cpp | ||
import semmle.code.cpp.rangeanalysis.SimpleRangeAnalysis | ||
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from BinaryBitwiseOperation shift, Expr lhs | ||
where | ||
(shift instanceof LShiftExpr or shift instanceof RShiftExpr) and | ||
lhs = shift.getLeftOperand().getFullyConverted() and | ||
lowerBound(lhs) < 0 | ||
select shift, | ||
"This signed shift could cause undefined behavior if the value is negative. Type of lhs: " + | ||
lhs.getType().toString() |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,17 @@ | ||
# -*- coding: utf-8 -*- | ||
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from system_tests import CaseMeta, path, check_no_ASAN_UBSAN_errors | ||
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class PentaxMakerNotePrintTimeSignedLeftShift(metaclass=CaseMeta): | ||
""" | ||
Regression test for the bug described in: | ||
https://github.com/Exiv2/exiv2/issues/1920 | ||
""" | ||
url = "https://github.com/Exiv2/exiv2/issues/1920" | ||
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filename = path("$data_path/issue_1920_poc.tiff") | ||
commands = ["$exiv2 -q -Pt $filename"] | ||
stderr = [""] | ||
retval = [0] | ||
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compare_stdout = check_no_ASAN_UBSAN_errors |
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uint32_t doesn't cut it here?
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Actually
uint16_t
is probably sufficient for the intended purpose here. I think this is probably a similar scenario to #1706. The value is supposed to be a byte, but there's no validation on that, so a malicious file can contain along
instead. For the valid cases, we only need to extract the byte.I'll change it.