C++: add fread and printf alias models

Robert Marsh · Robert Marsh · commit 28fb3d606ad9 · 2019-12-05T12:14:33.000-08:00
diff --git a/cpp/ql/src/semmle/code/cpp/models/Models.qll b/cpp/ql/src/semmle/code/cpp/models/Models.qll
@@ -1,3 +1,4 @@
+private import implementations.Fread
 private import implementations.IdentityFunction
 private import implementations.Inet
 private import implementations.Memcpy
diff --git a/cpp/ql/src/semmle/code/cpp/models/implementations/Fread.qll b/cpp/ql/src/semmle/code/cpp/models/implementations/Fread.qll
@@ -0,0 +1,16 @@
+import semmle.code.cpp.models.interfaces.Alias
+
+class Fread extends AliasFunction {
+  Fread() {
+    this.hasGlobalName("fread")
+  }
+
+  override predicate parameterNeverEscapes(int n) {
+    n = 0 or
+    n = 3
+  }
+
+  override predicate parameterEscapesOnlyViaReturn(int n) { none() }
+
+  override predicate parameterIsAlwaysReturned(int n) { none() }
+}
diff --git a/cpp/ql/src/semmle/code/cpp/models/implementations/Printf.qll b/cpp/ql/src/semmle/code/cpp/models/implementations/Printf.qll
@@ -1,9 +1,10 @@
 import semmle.code.cpp.models.interfaces.FormattingFunction
+import semmle.code.cpp.models.interfaces.Alias
 
 /**
  * The standard functions `printf`, `wprintf` and their glib variants.
  */
-class Printf extends FormattingFunction {
+class Printf extends FormattingFunction, AliasFunction {
   Printf() {
     this instanceof TopLevelFunction and
     (
@@ -22,6 +23,14 @@ class Printf extends FormattingFunction {
     hasGlobalOrStdName("wprintf") or
     hasGlobalName("wprintf_s")
   }
+
+  override predicate parameterNeverEscapes(int n) {
+    n = 0
+  }
+
+  override predicate parameterEscapesOnlyViaReturn(int n) { none() }
+
+  override predicate parameterIsAlwaysReturned(int n) { none() }
 }
 
 /**

Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,4 @@`
	`1`	`+private import implementations.Fread`
`1`	`2`	`private import implementations.IdentityFunction`
`2`	`3`	`private import implementations.Inet`
`3`	`4`	`private import implementations.Memcpy`