Python: Add modeling of simplejson PyPI package

I noticed that we don't handle PostUpdateNote very well in the concept tests,
for exmaple for `json.dump(...)` there _should_ have been an `encodeOutput` as
part of the inline expectations.

I'll work on fixing that up in a separate PR, to keep things clean.

docs/codeql/support/reusables/frameworks.rst

@@ -156,6 +156,7 @@ Python built-in support
    Tornado, Web framework
    PyYAML, Serialization
    dill, Serialization
+   simplejson, Serialization
    fabric, Utility library
    invoke, Utility library
    idna, Utility library

python/change-notes/2021-05-10-simplejson-add-modeling.md

@@ -0,0 +1,2 @@
+lgtm,codescanning
+* Added modeling of the PyPI package `simplejson`.

python/ql/src/semmle/python/Frameworks.qll

@@ -16,6 +16,7 @@ private import semmle.python.frameworks.MysqlConnectorPython
 private import semmle.python.frameworks.MySQLdb
 private import semmle.python.frameworks.Psycopg2
 private import semmle.python.frameworks.PyMySQL
+private import semmle.python.frameworks.Simplejson
 private import semmle.python.frameworks.Stdlib
 private import semmle.python.frameworks.Tornado
 private import semmle.python.frameworks.Yaml

python/ql/src/semmle/python/frameworks/Simplejson.qll

@@ -0,0 +1,84 @@
+/**
+ * Provides classes modeling security-relevant aspects of the `simplejson` PyPI package.
+ * See https://simplejson.readthedocs.io/en/latest/.
+ */
+
+private import python
+private import semmle.python.dataflow.new.DataFlow
+private import semmle.python.dataflow.new.TaintTracking
+private import semmle.python.Concepts
+private import semmle.python.ApiGraphs
+
+/**
+ * Provides models for the `simplejson` PyPI package.
+ * See https://simplejson.readthedocs.io/en/latest/.
+ */
+private module SimplejsonModel {
+  /**
+   * A call to `simplejson.dumps`.
+   *
+   * See https://simplejson.readthedocs.io/en/latest/#simplejson.dumps
+   */
+  private class SimplejsonDumpsCall extends Encoding::Range, DataFlow::CallCfgNode {
+    SimplejsonDumpsCall() { this = API::moduleImport("simplejson").getMember("dumps").getACall() }
+
+    override DataFlow::Node getAnInput() { result in [this.getArg(0), this.getArgByName("obj")] }
+
+    override DataFlow::Node getOutput() { result = this }
+
+    override string getFormat() { result = "JSON" }
+  }
+
+  /**
+   * A call to `simplejson.dump`.
+   *
+   * See https://simplejson.readthedocs.io/en/latest/#simplejson.dump
+   */
+  private class SimplejsonDumpCall extends Encoding::Range, DataFlow::CallCfgNode {
+    SimplejsonDumpCall() { this = API::moduleImport("simplejson").getMember("dump").getACall() }
+
+    override DataFlow::Node getAnInput() { result in [this.getArg(0), this.getArgByName("obj")] }
+
+    override DataFlow::Node getOutput() {
+      result.(DataFlow::PostUpdateNode).getPreUpdateNode() in [
+          this.getArg(1), this.getArgByName("fp")
+        ]
+    }
+
+    override string getFormat() { result = "JSON" }
+  }
+
+  /**
+   * A call to `simplejson.loads`.
+   *
+   * See https://simplejson.readthedocs.io/en/latest/#simplejson.loads
+   */
+  private class SimplejsonLoadsCall extends Decoding::Range, DataFlow::CallCfgNode {
+    SimplejsonLoadsCall() { this = API::moduleImport("simplejson").getMember("loads").getACall() }
+
+    override DataFlow::Node getAnInput() { result in [this.getArg(0), this.getArgByName("s")] }
+
+    override DataFlow::Node getOutput() { result = this }
+
+    override string getFormat() { result = "JSON" }
+
+    override predicate mayExecuteInput() { none() }
+  }
+
+  /**
+   * A call to `simplejson.load`.
+   *
+   * See https://simplejson.readthedocs.io/en/latest/#simplejson.load
+   */
+  private class SimplejsonLoadCall extends Decoding::Range, DataFlow::CallCfgNode {
+    SimplejsonLoadCall() { this = API::moduleImport("simplejson").getMember("load").getACall() }
+
+    override DataFlow::Node getAnInput() { result in [this.getArg(0), this.getArgByName("fp")] }
+
+    override DataFlow::Node getOutput() { result = this }
+
+    override string getFormat() { result = "JSON" }
+
+    override predicate mayExecuteInput() { none() }
+  }
+}

python/ql/test/library-tests/frameworks/simplejson/ConceptsTest.ql

@@ -0,0 +1,2 @@
+import python
+import experimental.meta.ConceptsTest

python/ql/test/library-tests/frameworks/simplejson/InlineTaintTest.expected

@@ -0,0 +1,3 @@
+argumentToEnsureNotTaintedNotMarkedAsSpurious
+untaintedArgumentToEnsureTaintedNotMarkedAsMissing
+failures

python/ql/test/library-tests/frameworks/simplejson/InlineTaintTest.ql

@@ -0,0 +1 @@
+import experimental.meta.InlineTaintTest

python/ql/test/library-tests/frameworks/simplejson/taint_test.py

@@ -0,0 +1,46 @@
+import simplejson
+from io import StringIO
+
+def test():
+    ts = TAINTED_STRING
+    tainted_obj = {"foo": ts}
+
+    encoded = simplejson.dumps(tainted_obj) # $ encodeOutput=Attribute() encodeFormat=JSON encodeInput=tainted_obj
+
+    ensure_tainted(
+        encoded, # $ tainted
+        simplejson.dumps(tainted_obj), # $ tainted encodeOutput=Attribute() encodeFormat=JSON encodeInput=tainted_obj
+        simplejson.dumps(obj=tainted_obj), # $ tainted encodeOutput=Attribute() encodeFormat=JSON encodeInput=tainted_obj
+        simplejson.loads(encoded), # $ tainted decodeOutput=Attribute() decodeFormat=JSON decodeInput=encoded
+        simplejson.loads(s=encoded), # $ tainted decodeOutput=Attribute() decodeFormat=JSON decodeInput=encoded
+    )
+
+    # load/dump with file-like
+    tainted_filelike = StringIO()
+    simplejson.dump(tainted_obj, tainted_filelike) # $ encodeFormat=JSON encodeInput=tainted_obj
+
+    tainted_filelike.seek(0)
+    ensure_tainted(
+        tainted_filelike, # $ tainted
+        simplejson.load(tainted_filelike), # $ tainted decodeOutput=Attribute() decodeFormat=JSON decodeInput=tainted_filelike
+    )
+
+    # load/dump with file-like using keyword-args
+    tainted_filelike = StringIO()
+    simplejson.dump(obj=tainted_obj, fp=tainted_filelike) # $ encodeFormat=JSON encodeInput=tainted_obj
+
+    tainted_filelike.seek(0)
+    ensure_tainted(
+        tainted_filelike, # $ tainted
+        simplejson.load(fp=tainted_filelike), # $ tainted decodeOutput=Attribute() decodeFormat=JSON decodeInput=tainted_filelike
+    )
+
+# To make things runable
+
+TAINTED_STRING = "TAINTED_STRING"
+def ensure_tainted(*args):
+    print("- ensure_tainted")
+    for i, arg in enumerate(args):
+        print("arg {}: {!r}".format(i, arg))
+
+test()