Pyhton: Extract vulnerable hostnames into own predicate

Which makes the code a bit cleaner (and made testing out back-tracking easier).

Author: RasmusWL

python/ql/src/Security/CVE-2018-1281/BindToAllInterfaces.ql

@@ -14,47 +14,50 @@ import python
 import semmle.python.dataflow.new.DataFlow
 import semmle.python.ApiGraphs
 
+/** Gets a hostname that can be used to bind to all interfaces. */
+private string vulnerableHostname() {
+  result in [
+      // IPv4
+      "0.0.0.0", "",
+      // IPv6
+      "::", "::0"
+    ]
+}
+
 /** Gets a reference to a hostname that can be used to bind to all interfaces. */
-private DataFlow::LocalSourceNode vulnerableHostname(DataFlow::TypeTracker t, string hostname) {
+private DataFlow::LocalSourceNode vulnerableHostnameRef(DataFlow::TypeTracker t, string hostname) {
   t.start() and
-  exists(StrConst allInterfacesStrConst |
-    hostname in [
-        // IPv4
-        "0.0.0.0", "",
-        // IPv6
-        "::", "::0"
-      ]
-  |
+  exists(StrConst allInterfacesStrConst | hostname = vulnerableHostname() |
     allInterfacesStrConst.getText() = hostname and
     result.asExpr() = allInterfacesStrConst
   )
   or
-  // Due to bad performance when using normal setup with `vulnerableHostname(t2, hostname).track(t2, t)`
+  // Due to bad performance when using normal setup with `vulnerableHostnameRef(t2, hostname).track(t2, t)`
   // we have inlined that code and forced a join
   exists(DataFlow::TypeTracker t2 |
     exists(DataFlow::StepSummary summary |
-      vulnerableHostname_first_join(t2, hostname, result, summary) and
+      vulnerableHostnameRef_first_join(t2, hostname, result, summary) and
       t = t2.append(summary)
     )
   )
 }
 
 pragma[nomagic]
-private predicate vulnerableHostname_first_join(
+private predicate vulnerableHostnameRef_first_join(
   DataFlow::TypeTracker t2, string hostname, DataFlow::Node res, DataFlow::StepSummary summary
 ) {
-  DataFlow::StepSummary::step(vulnerableHostname(t2, hostname), res, summary)
+  DataFlow::StepSummary::step(vulnerableHostnameRef(t2, hostname), res, summary)
 }
 
 /** Gets a reference to a hostname that can be used to bind to all interfaces. */
-DataFlow::Node vulnerableHostname(string hostname) {
-  vulnerableHostname(DataFlow::TypeTracker::end(), hostname).flowsTo(result)
+DataFlow::Node vulnerableHostnameRef(string hostname) {
+  vulnerableHostnameRef(DataFlow::TypeTracker::end(), hostname).flowsTo(result)
 }
 
 /** Gets a reference to tuple containing a hostname as the first element, that can be used to bind to all interfaces. */
 private DataFlow::LocalSourceNode vulnerableAddressTuple(DataFlow::TypeTracker t, string hostname) {
   t.start() and
-  result.asExpr() = any(Tuple tup | tup.getElt(0) = vulnerableHostname(hostname).asExpr())
+  result.asExpr() = any(Tuple tup | tup.getElt(0) = vulnerableHostnameRef(hostname).asExpr())
   or
   // Due to bad performance when using normal setup with `vulnerableAddressTuple(t2, hostname).track(t2, t)`
   // we have inlined that code and forced a join