JS: Update query17 from intro tutorial

docs/codeql/codeql-language-guides/codeql-library-for-javascript.rst

@@ -700,19 +700,16 @@ The data flow graph-based analyses described so far are all intraprocedural: the
 
 We distinguish here between data flow proper, and *taint tracking*: the latter not only considers value-preserving flow (such as from variable definitions to uses), but also cases where one value influences ("taints") another without determining it entirely. For example, in the assignment ``s2 = s1.substring(i)``, the value of ``s1`` influences the value of ``s2``, because ``s2`` is assigned a substring of ``s1``. In general, ``s2`` will not be assigned ``s1`` itself, so there is no data flow from ``s1`` to ``s2``, but ``s1`` still taints ``s2``.
 
-It is a common pattern that we wish to specify data flow or taint analysis in terms of its *sources* (where flow starts), *sinks* (where it should be tracked), and *barriers* or *sanitizers* (where flow is interrupted). Sanitizers they are very common in security analyses: for example, an analysis that tracks the flow of untrusted user input into, say, a SQL query has to keep track of code that validates the input, thereby making it safe to use. Such a validation step is an example of a sanitizer.
+It is a common pattern that we wish to specify data flow or taint analysis in terms of its *sources* (where flow starts), *sinks* (where it should be tracked), and *barriers* (also called *sanitizers*) where flow is interrupted. Sanitizers they are very common in security analyses: for example, an analysis that tracks the flow of untrusted user input into, say, a SQL query has to keep track of code that validates the input, thereby making it safe to use. Such a validation step is an example of a sanitizer.
 
-The classes ``DataFlow::Configuration`` and ``TaintTracking::Configuration`` allow specifying a data flow or taint analysis, respectively, by overriding the following predicates:
+A module implementing the signature `DataFlow::ConfigSig` may specify a data flow or taint analysis by implementing the following predicates:
 
 -  ``isSource(DataFlow::Node nd)`` selects all nodes ``nd`` from where flow tracking starts.
 -  ``isSink(DataFlow::Node nd)`` selects all nodes ``nd`` to which the flow is tracked.
--  ``isBarrier(DataFlow::Node nd)`` selects all nodes ``nd`` that act as a barrier for data flow; ``isSanitizer`` is the corresponding predicate for taint tracking configurations.
--  ``isBarrierEdge(DataFlow::Node src, DataFlow::Node trg)`` is a variant of ``isBarrier(nd)`` that allows specifying barrier *edges* in addition to barrier nodes; again, ``isSanitizerEdge`` is the corresponding predicate for taint tracking;
+-  ``isBarrier(DataFlow::Node nd)`` selects all nodes ``nd`` that act as a barrier/sanitizer for data flow.
 -  ``isAdditionalFlowStep(DataFlow::Node src, DataFlow::Node trg)`` allows specifying custom additional flow steps for this analysis; ``isAdditionalTaintStep`` is the corresponding predicate for taint tracking configurations.
 
-Since for technical reasons both ``Configuration`` classes are subtypes of ``string``, you have to choose a unique name for each flow configuration and equate ``this`` with it in the characteristic predicate (as in the example below).
-
-The predicate ``Configuration.hasFlow`` performs the actual flow tracking, starting at a source and looking for flow to a sink that does not pass through a barrier node or edge.
+Such a module can be passed to ``DataFlow::Global<...>``. This will produce a module with a ``flow`` predicate that performs the actual flow tracking, starting at a source and looking for flow to a sink that does not pass through a barrier node.
 
 For example, suppose that we are developing an analysis to find hard-coded passwords. We might write a simple query that looks for string constants flowing into variables named ``"password"``.
 
@@ -720,35 +717,27 @@ For example, suppose that we are developing an analysis to find hard-coded passw
 
    import javascript
 
-   class PasswordTracker extends DataFlow::Configuration {
-       PasswordTracker() {
-           // unique identifier for this configuration
-           this = "PasswordTracker"
-       }
+   module PasswordConfig implements DataFlow::ConfigSig {
+       predicate isSource(DataFlow::Node nd) { nd.asExpr() instanceof StringLiteral }
 
-       override predicate isSource(DataFlow::Node nd) {
-           nd.asExpr() instanceof StringLiteral
-       }
-
-       override predicate isSink(DataFlow::Node nd) {
-           passwordVarAssign(_, nd)
-       }
-
-       predicate passwordVarAssign(Variable v, DataFlow::Node nd) {
-          v.getAnAssignedExpr() = nd.asExpr() and
-          v.getName().toLowerCase() = "password"
-       }
+       predicate isSink(DataFlow::Node nd) { passwordVarAssign(_, nd) }
    }
 
-Now we can rephrase our query to use ``Configuration.hasFlow``:
+   predicate passwordVarAssign(Variable v, DataFlow::Node nd) {
+       v.getAnAssignedExpr() = nd.asExpr() and
+       v.getName().toLowerCase() = "password"
+   }
+
+   module PasswordFlow = DataFlow::Global<PasswordConfig>;
+
+Now we can rephrase our query to use ``PasswordFlow::flow``:
 
 .. code-block:: ql
 
-   from PasswordTracker pt, DataFlow::Node source, DataFlow::Node sink, Variable v
-   where pt.hasFlow(source, sink) and pt.passwordVarAssign(v, sink)
+   from DataFlow::Node source, DataFlow::Node sink, Variable v
+   where PasswordFlow::flow(_, sink) and passwordVarAssign(v, sink)
    select sink, "Password variable " + v + " is assigned a constant string."
 
-
 Syntax errors
 ~~~~~~~~~~~~~
 

javascript/ql/test/tutorials/Introducing the JavaScript libraries/query17.qll

@@ -1,23 +1,20 @@
 import javascript
 
-class PasswordTracker extends DataFlow::Configuration {
-  PasswordTracker() {
-    // unique identifier for this configuration
-    this = "PasswordTracker"
-  }
+module PasswordConfig implements DataFlow::ConfigSig {
+  predicate isSource(DataFlow::Node nd) { nd.asExpr() instanceof StringLiteral }
 
-  override predicate isSource(DataFlow::Node nd) { nd.asExpr() instanceof StringLiteral }
-
-  override predicate isSink(DataFlow::Node nd) { this.passwordVarAssign(_, nd) }
-
-  predicate passwordVarAssign(Variable v, DataFlow::Node nd) {
-    v.getAnAssignedExpr() = nd.asExpr() and
-    v.getName().toLowerCase() = "password"
-  }
+  predicate isSink(DataFlow::Node nd) { passwordVarAssign(_, nd) }
 }
 
+predicate passwordVarAssign(Variable v, DataFlow::Node nd) {
+  v.getAnAssignedExpr() = nd.asExpr() and
+  v.getName().toLowerCase() = "password"
+}
+
+module PasswordFlow = DataFlow::Global<PasswordConfig>;
+
 query predicate test_query17(DataFlow::Node sink, string res) {
-  exists(PasswordTracker pt, Variable v | pt.hasFlow(_, sink) and pt.passwordVarAssign(v, sink) |
+  exists(Variable v | PasswordFlow::flow(_, sink) and passwordVarAssign(v, sink) |
     res = "Password variable " + v.toString() + " is assigned a constant string."
   )
 }