Merge pull request #15513 from microsoft/50-model-gettext-family-of-string-operations

Added model for gettext variants.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/models/Models.qll

@@ -3,6 +3,7 @@ private import implementations.Deallocation
 private import implementations.Fread
 private import implementations.Getenv
 private import implementations.Gets
+private import implementations.GetText
 private import implementations.IdentityFunction
 private import implementations.Inet
 private import implementations.Iterator

cpp/ql/lib/semmle/code/cpp/models/implementations/GetText.qll

@@ -0,0 +1,33 @@
+import semmle.code.cpp.models.interfaces.DataFlow
+
+/**
+ * Returns the transated text index for a given gettext function `f`
+ */
+private int getTextArg(Function f) {
+  // basic variations of gettext
+  f.hasGlobalOrStdName("gettext") and result = 0
+  or
+  f.hasGlobalOrStdName("dgettext") and result = 1
+  or
+  f.hasGlobalOrStdName("dcgettext") and result = 1
+  or
+  // plural variations of gettext that take one format string for singular and another for plural form
+  f.hasGlobalOrStdName("ngettext") and
+  (result = 0 or result = 1)
+  or
+  f.hasGlobalOrStdName("dngettext") and
+  (result = 1 or result = 2)
+  or
+  f.hasGlobalOrStdName("dcngettext") and
+  (result = 1 or result = 2)
+}
+
+class GetTextFunction extends DataFlowFunction {
+  int argInd;
+
+  GetTextFunction() { argInd = getTextArg(this) }
+
+  override predicate hasDataFlow(FunctionInput input, FunctionOutput output) {
+    input.isParameterDeref(argInd) and output.isReturnValueDeref()
+  }
+}

cpp/ql/src/Likely Bugs/Format/NonConstantFormat.ql

@@ -16,6 +16,7 @@
  */
 
 import semmle.code.cpp.ir.dataflow.TaintTracking
+import semmle.code.cpp.models.implementations.GetText
 import semmle.code.cpp.commons.Printf
 
 // For the following `...gettext` functions, we assume that
@@ -26,30 +27,21 @@ predicate whitelistFunction(Function f, int arg) {
   // basic variations of gettext
   f.getName() = "_" and arg = 0
   or
-  f.getName() = "gettext" and arg = 0
-  or
-  f.getName() = "dgettext" and arg = 1
-  or
-  f.getName() = "dcgettext" and arg = 1
-  or
-  // plural variations of gettext that take one format string for singular and another for plural form
-  f.getName() = "ngettext" and
-  (arg = 0 or arg = 1)
-  or
-  f.getName() = "dngettext" and
-  (arg = 1 or arg = 2)
-  or
-  f.getName() = "dcngettext" and
-  (arg = 1 or arg = 2)
+  exists(FunctionInput input |
+    f.(GetTextFunction).hasDataFlow(input, _) and
+    input.isParameterDeref(arg)
+  )
 }
 
-// we assume that ALL uses of the `_` macro
+// we assume that ALL uses of the `_` macro (and calls to `gettext`)
 // return constant string literals
 predicate underscoreMacro(Expr e) {
   exists(MacroInvocation mi |
     mi.getMacroName() = "_" and
     mi.getExpr() = e
   )
+  or
+  e = any(GetTextFunction gettext).getACallToThisFunction()
 }
 
 /**

cpp/ql/src/change-notes/2024-02-05-gettext-dataflows.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Added dataflow models for the `gettext` function variants. 

cpp/ql/test/library-tests/dataflow/dataflow-tests/test-source-sink.expected

@@ -303,6 +303,12 @@ irFlow
 | test.cpp:914:46:914:53 | source | test.cpp:919:10:919:30 | global_pointer_static |
 | test.cpp:915:57:915:76 | *indirect_source(1) | test.cpp:921:19:921:50 | *global_pointer_static_indirect_1 |
 | test.cpp:932:23:932:28 | call to source | test.cpp:937:10:937:24 | * ... |
+| test.cpp:958:18:958:32 | *call to indirect_source | test.cpp:961:19:961:28 | *translated |
+| test.cpp:973:18:973:32 | *call to indirect_source | test.cpp:977:19:977:28 | *translated |
+| test.cpp:994:18:994:32 | *call to indirect_source | test.cpp:999:19:999:28 | *translated |
+| test.cpp:994:18:994:32 | *call to indirect_source | test.cpp:1003:19:1003:28 | *translated |
+| test.cpp:1021:18:1021:32 | *call to indirect_source | test.cpp:1027:19:1027:28 | *translated |
+| test.cpp:1021:18:1021:32 | *call to indirect_source | test.cpp:1031:19:1031:28 | *translated |
 | true_upon_entry.cpp:9:11:9:16 | call to source | true_upon_entry.cpp:13:8:13:8 | x |
 | true_upon_entry.cpp:17:11:17:16 | call to source | true_upon_entry.cpp:21:8:21:8 | x |
 | true_upon_entry.cpp:27:9:27:14 | call to source | true_upon_entry.cpp:29:8:29:8 | x |

cpp/ql/test/library-tests/dataflow/dataflow-tests/test.cpp

@@ -936,4 +936,105 @@ namespace global_variable_conflation_test {
     sink(global_pointer); // clean
     sink(*global_pointer); // $ ir MISSING: ast
   }
+}
+
+char* gettext(const char*);
+char* dgettext(const char*, const char*);
+char* ngettext(const char*, const char*, unsigned long int);
+char* dngettext (const char*, const char *, const char *, unsigned long int);
+
+namespace test_gettext {
+  char* source();
+  char* indirect_source();
+
+  void test_gettext() {
+    char* data = source();
+    char* translated = gettext(data);
+    sink(translated); // clean 
+    indirect_sink(translated); // clean
+  }
+
+  void indirect_test_dgettext() {
+    char* data = indirect_source();
+    char* translated = gettext(data);
+    sink(translated); // clean
+    indirect_sink(translated); // $ ir MISSING: ast
+  }
+
+  void test_dgettext() {
+    char* data = source();
+    char* domain = source(); // Should not trace from this source
+    char* translated = dgettext(domain, data);
+    sink(translated); // clean 
+    indirect_sink(translated); // clean
+  }
+
+  void indirect_test_gettext() {
+    char* data = indirect_source();
+    char* domain = indirect_source(); // Should not trace from this source
+    char* translated = dgettext(domain, data);
+    sink(translated); // clean
+    indirect_sink(translated); // $ ir MISSING: ast
+  }
+
+  void test_ngettext() {
+    char* data = source();
+    char* np = nullptr; // Don't coun't as a source
+    
+    char* translated = ngettext(data, np, 0);
+    sink(translated); // clean 
+    indirect_sink(translated); // clean
+
+    translated = ngettext(np, data, 0);
+    sink(translated); // clean 
+    indirect_sink(translated); // clean
+  }
+
+  void indirect_test_ngettext() {
+    char* data = indirect_source();
+    char* np = nullptr; // Don't coun't as a source
+    
+    char* translated = ngettext(data, np, 0);
+    sink(translated); // clean 
+    indirect_sink(translated); // $ ir MISSING: ast
+
+    translated = ngettext(np, data, 0);
+    sink(translated); // clean 
+    indirect_sink(translated); // $ ir MISSING: ast
+  }
+
+  void test_dngettext() {
+    char* data = source();
+    char* np = nullptr; // Don't coun't as a source
+    char* domain = source(); // Should not trace from this source
+    
+    char* translated = dngettext(domain, data, np, 0);
+    sink(translated); // clean 
+    indirect_sink(translated); // clean
+
+    translated = dngettext(domain, np, data, 0);
+    sink(translated); // clean 
+    indirect_sink(translated); // clean
+  }
+
+  void indirect_test_dngettext() {
+    char* data = indirect_source();
+    char* np = nullptr; // Don't coun't as a source
+    char* domain = indirect_source(); // Should not trace from this source
+    
+    char* translated = dngettext(domain, data, np, 0);
+    sink(translated); // clean 
+    indirect_sink(translated); // $ ir MISSING: ast
+
+    translated = dngettext(domain, np, data, 0);
+    sink(translated); // clean 
+    indirect_sink(translated); // $ ir MISSING: ast
+  }
+
+  void indirect_test_gettext_no_flow_from_domain() {
+    char* domain = source(); // Should not trace from this source
+    char* translated = dgettext(domain, nullptr);
+    sink(translated); // clean 
+    indirect_sink(translated); // clean
+  }
 }