Java: Bugfix for flow through methods with taint step and upcast. #1616
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yh-semmle
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Jul 24, 2019
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LGTM. Would anyone from @Semmle/cpp-analysis or @Semmle/cs like to take a look as well before I merge?
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C++ and C# are not yet using the type-pruning capabilities of the dataflow library, so they should be unaffected by this change. |
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Flow through a method involving a taint (aka additional) step followed by an upcast was accidentally pruned due to the types not matching in the forward and backward pruning sweeps inside the summarized method. This meant that although the nodes in the final path were preserved, the nodes inside the method were not, which in turn meant that the summarization could not be reconstructed in the final flow calculation. The fix is to preserve the final tracked type from a summarized method and use that instead of resetting the tracked type at the call site. Note that this type should not usually depend on the tracked type at method entry since it will be reset at least once when the flow through the method takes the necessary taint step.