Merge pull request github#3694 from geoffw0/models

C++: Extend the GetsFunction and SystemFunction models.

Author: jbj

cpp/ql/src/semmle/code/cpp/models/implementations/Gets.qll

@@ -48,4 +48,17 @@ class GetsFunction extends DataFlowFunction, TaintFunction, ArrayFunction, Alias
     output.isParameterDeref(0) and
     description = "String read by " + this.getName()
   }
+
+  override predicate hasArrayWithVariableSize(int bufParam, int countParam) {
+    not hasGlobalOrStdName("gets") and
+    bufParam = 0 and
+    countParam = 1
+  }
+
+  override predicate hasArrayWithUnknownSize(int bufParam) {
+    hasGlobalOrStdName("gets") and
+    bufParam = 0
+  }
+
+  override predicate hasArrayOutput(int bufParam) { bufParam = 0 }
 }

cpp/ql/src/semmle/code/cpp/security/CommandExecution.qll

@@ -2,21 +2,44 @@
 
 import cpp
 import semmle.code.cpp.security.FunctionWithWrappers
+import semmle.code.cpp.models.interfaces.SideEffect
 
 /**
  * A function for running a command using a command interpreter.
  */
-class SystemFunction extends FunctionWithWrappers {
+class SystemFunction extends FunctionWithWrappers, ArrayFunction, AliasFunction, SideEffectFunction {
   SystemFunction() {
-    hasGlobalOrStdName("system") or
-    hasGlobalName("popen") or
+    hasGlobalOrStdName("system") or // system(command)
+    hasGlobalName("popen") or // popen(command, mode)
     // Windows variants
-    hasGlobalName("_popen") or
-    hasGlobalName("_wpopen") or
-    hasGlobalName("_wsystem")
+    hasGlobalName("_popen") or // _popen(command, mode)
+    hasGlobalName("_wpopen") or // _wpopen(command, mode)
+    hasGlobalName("_wsystem") // _wsystem(command)
   }
 
   override predicate interestingArg(int arg) { arg = 0 }
+
+  override predicate hasArrayWithNullTerminator(int bufParam) { bufParam = 0 or bufParam = 1 }
+
+  override predicate hasArrayInput(int bufParam) { bufParam = 0 or bufParam = 1 }
+
+  override predicate parameterNeverEscapes(int index) { index = 0 or index = 1 }
+
+  override predicate parameterEscapesOnlyViaReturn(int index) { none() }
+
+  override predicate parameterIsAlwaysReturned(int index) { none() }
+
+  override predicate hasOnlySpecificReadSideEffects() { any() }
+
+  override predicate hasOnlySpecificWriteSideEffects() {
+    hasGlobalOrStdName("system") or
+    hasGlobalName("_wsystem")
+  }
+
+  override predicate hasSpecificReadSideEffect(ParameterIndex i, boolean buffer) {
+    (i = 0 or i = 1) and
+    buffer = true
+  }
 }
 
 /**