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C++: Avoid partial chi flow to struct/class #3219

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Merged
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Apr 8, 2020
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C++: Avoid partial chi flow to struct/class #3219

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15 changes: 14 additions & 1 deletion cpp/ql/src/semmle/code/cpp/ir/dataflow/DefaultTaintTracking.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -189,9 +189,22 @@ private predicate instructionTaintStep(Instruction i1, Instruction i2) {
or
i2.(UnaryInstruction).getUnary() = i1
or
i2.(ChiInstruction).getPartial() = i1 and
// Flow out of definition-by-reference
i2.(ChiInstruction).getPartial() = i1.(WriteSideEffectInstruction) and
not i2.isResultConflated()
or
// Flow from an element to an array or union that contains it.
i2.(ChiInstruction).getPartial() = i1 and
not i2.isResultConflated() and
exists(Type t | i2.getResultLanguageType().hasType(t, false) |
t instanceof Union
or
t instanceof ArrayType
or
// Buffers or unknown size
t instanceof UnknownType
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For a struct pointer parameter, I think its chi nodes will have UnknownType. How can we find the struct type?

)
or
exists(BinaryInstruction bin |
bin = i2 and
predictableInstruction(i2.getAnOperand().getDef()) and
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