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C++: Add taint through fopen #17715

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Oct 10, 2024
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C++: Add taint through fopen #17715

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201842d
C++: Add test with missing flow through 'fopen'.
MathiasVP Oct 9, 2024
338e820
C++: Add a taint model for 'fopen' and accept test changes.
MathiasVP Oct 9, 2024
954235e
C++: Add change note.
MathiasVP Oct 9, 2024
6965cf7
C++: Make ql-for-ql happy.
MathiasVP Oct 9, 2024
acac3a0
C++: Respond to review comments.
MathiasVP Oct 9, 2024
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17 changes: 16 additions & 1 deletion cpp/ql/lib/semmle/code/cpp/models/implementations/Fopen.qll
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Expand Up @@ -7,7 +7,7 @@ import semmle.code.cpp.models.interfaces.Alias
import semmle.code.cpp.models.interfaces.SideEffect

/** The function `fopen` and friends. */
private class Fopen extends Function, AliasFunction, SideEffectFunction {
private class Fopen extends Function, AliasFunction, SideEffectFunction, TaintFunction {
Fopen() {
this.hasGlobalOrStdName(["fopen", "fopen_s", "freopen"])
or
Expand Down Expand Up @@ -47,4 +47,19 @@ private class Fopen extends Function, AliasFunction, SideEffectFunction {
i = 0 and
buffer = true
}

override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
this.hasGlobalOrStdName(["fopen", "freopen", "_wfopen", "_fsopen", "_wfsopen"]) and
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input.isParameterDeref(0) and
output.isReturnValueDeref()
or
// The out parameter is a pointer to a `FILE*`.
this.hasGlobalOrStdName(["fopen_s"]) and
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input.isParameterDeref(1) and
output.isParameterDeref(0, 2)
or
this.hasGlobalName(["_open", "_wopen"]) and
input.isParameterDeref(0) and
output.isReturnValue()
}
}
1 change: 1 addition & 0 deletions cpp/ql/test/library-tests/dataflow/taint-tests/localTaint.expected
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Expand Up @@ -6588,6 +6588,7 @@ WARNING: module 'TaintTracking' has been deprecated and may be removed in future
| taint.cpp:785:23:785:28 | source | taint.cpp:786:18:786:23 | source | |
| taint.cpp:785:23:785:28 | source | taint.cpp:790:15:790:20 | source | |
| taint.cpp:786:12:786:16 | call to fopen | taint.cpp:787:7:787:7 | f | |
| taint.cpp:786:18:786:23 | source | taint.cpp:786:12:786:16 | call to fopen | TAINT |
| taint.cpp:789:8:789:9 | f2 | taint.cpp:790:11:790:12 | f2 | |
| taint.cpp:789:8:789:9 | f2 | taint.cpp:791:7:791:8 | f2 | |
| taint.cpp:790:10:790:12 | ref arg & ... | taint.cpp:790:11:790:12 | f2 [inner post update] | |
Expand Down
4 changes: 2 additions & 2 deletions cpp/ql/test/library-tests/dataflow/taint-tests/taint.cpp
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Expand Up @@ -784,9 +784,9 @@ int fopen_s(FILE** pFile, const char *filename, const char *mode);

void fopen_test(char* source) {
FILE* f = fopen(source, "r");
sink(f); // $ MISSING: ast,ir
sink(f); // $ ast,ir

FILE* f2;
fopen_s(&f2, source, "r");
sink(f2); // $ ast MISSING: ir
sink(f2); // $ ast,ir
}