JS: Add Knex model

Author: asgerf

javascript/ql/src/javascript.qll

@@ -95,6 +95,7 @@ import semmle.javascript.frameworks.JWT
 import semmle.javascript.frameworks.Handlebars
 import semmle.javascript.frameworks.History
 import semmle.javascript.frameworks.Immutable
+import semmle.javascript.frameworks.Knex
 import semmle.javascript.frameworks.LazyCache
 import semmle.javascript.frameworks.LodashUnderscore
 import semmle.javascript.frameworks.Logging

javascript/ql/src/semmle/javascript/frameworks/Knex.qll

@@ -0,0 +1,62 @@
+/**
+ * Provides classes and predicates for working with [knex](https://knexjs.org).
+ */
+
+private import javascript
+
+/**
+ * Provides classes and predicates for working with [knex](https://knexjs.org).
+ */
+module Knex {
+  /** Gets an API node referring to the `knex` library. */
+  API::Node knexLibrary() { result = API::moduleImport("knex") }
+
+  /** Gets a method name on Knex objects which return a Knex object. */
+  bindingset[result]
+  private string chainableKnexMethod() {
+    not result in [
+        "toString", "valueOf", "then", "catch", "finally", "toSQL", "asCallback", "stream"
+      ]
+  }
+
+  /** Gets an API node referring to a `knex` object, such as `knex.from('foo')`. */
+  API::Node knexObject() {
+    result = knexLibrary().getReturn()
+    or
+    result = knexObject().getReturn()
+    or
+    result = knexObject().getMember("schema")
+    or
+    result = knexObject().getMember(chainableKnexMethod()).getReturn()
+    or
+    // callback for building inner queries, such as `knex.join(function() { this.on('blah') })`
+    result = knexObject().getMember(chainableKnexMethod()).getParameter(0).getReceiver()
+    or
+    // knex.transaction(trx => { ... })
+    result = knexObject().getMember("transaction").getParameter(0).getParameter(0)
+  }
+
+  /** A call to a Knex method that takes a raw SQL string as input. */
+  class RawKnexCall extends DataFlow::CallNode {
+    RawKnexCall() { this = knexObject().getMember(["raw", any(string s) + "Raw"]).getACall() }
+  }
+
+  /** A SQL string passed to a raw Knex method. */
+  private class RawKnexSqlString extends SQL::SqlString {
+    RawKnexSqlString() { this = any(RawKnexCall call).getArgument(0).asExpr() }
+  }
+
+  /** A call that triggers a SQL query submission. */
+  private class KnexDatabaseAccess extends DatabaseAccess {
+    KnexDatabaseAccess() {
+      this = knexObject().getMember(["then", "stream", "asCallback"]).getACall()
+      or
+      exists(AwaitExpr await |
+        this = await.flow() and
+        await.getOperand() = knexObject().getAUse().asExpr()
+      )
+    }
+
+    override DataFlow::Node getAQueryArgument() { none() }
+  }
+}