C++: Remove pointer/pointee conflation from models of "pure" functions #18556
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,5 +1,6 @@ | ||
| import semmle.code.cpp.models.interfaces.ArrayFunction | ||
| import semmle.code.cpp.models.interfaces.Taint | ||
| import semmle.code.cpp.models.interfaces.DataFlow | ||
| import semmle.code.cpp.models.interfaces.Alias | ||
| import semmle.code.cpp.models.interfaces.SideEffect | ||
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@@ -8,7 +9,7 @@ import semmle.code.cpp.models.interfaces.SideEffect | |
| * guaranteed to be side-effect free. | ||
| */ | ||
| private class PureStrFunction extends AliasFunction, ArrayFunction, TaintFunction, | ||
| SideEffectFunction, DataFlowFunction | ||
| { | ||
| PureStrFunction() { | ||
| this.hasGlobalOrStdOrBslName([ | ||
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@@ -26,22 +27,43 @@ private class PureStrFunction extends AliasFunction, ArrayFunction, TaintFunctio | |
| } | ||
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| override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) { | ||
| exists(ParameterIndex i | exists(this.getParameter(i)) | | ||
| // For these functions we add taint flow according to the following rules: | ||
| // 1. If the parameter is of a pointer type then there is taint from the | ||
| // indirection of the parameter. Otherwise, there is taint from the | ||
| // parameter. | ||
| // 2. If the return value is of a pointer type then there is taint to the | ||
| // indirection of the return. Otherwise, there is taint to the return. | ||
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There was a problem hiding this comment. Does it make sense to move this comment up before the There was a problem hiding this comment. Sure. Fixed in 67e3b69 |
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| ( | ||
| if this.getParameter(i).getUnspecifiedType() instanceof PointerType | ||
| then input.isParameterDeref(i) | ||
| else input.isParameter(i) | ||
| ) and | ||
| // Functions that end with _l also take a locale argument (always as the last argument), | ||
| // and we don't want taint from those arguments. | ||
| (not this.getName().matches("%\\_l") or exists(this.getParameter(i + 1))) | ||
| ) and | ||
| ( | ||
| if this.getUnspecifiedType() instanceof PointerType | ||
| then output.isReturnValueDeref() | ||
| else output.isReturnValue() | ||
| ) | ||
| or | ||
| // If there is taint flow from *input to *output then there is also taint | ||
| // flow from input to output. | ||
| this.hasTaintFlow(input.getIndirectionInput(), output.getIndirectionOutput()) and | ||
| // no need to add taint-flow if we already have dataflow | ||
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| not this.hasDataFlow(input, output) | ||
| } | ||
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| override predicate hasDataFlow(FunctionInput input, FunctionOutput output) { | ||
| exists(int i | | ||
| input.isParameter(i) and | ||
| // see the comment in `hasTaintFlow` for an explanation | ||
| (not this.getName().matches("%\\_l") or exists(this.getParameter(i + 1))) and | ||
| // These functions always return the same pointer as they are given | ||
| this.hasGlobalOrStdOrBslName([strrev(), strlwr(), strupr()]) and | ||
| this.getParameter(i).getUnspecifiedType() instanceof PointerType and | ||
| output.isReturnValue() | ||
| ) | ||
| } | ||
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We could add a helper predicate for the locale argument check?
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Good idea! Fixed in 7792839