chore(iast): header source in werkzeug 3.1 (#12213)

IAST taint source Header wouldn't work correctly in `werkzeug>=3.1.0`

We're tainting `EnvironHeaders.__getitem__` due to get method calls to
`__getitem__`

https://github.com/pallets/werkzeug/blob/2.3.8/src/werkzeug/datastructures/headers.py
but now the `__getitem__` and `get` methods of `EnvironHeaders` are
completely differents:

https://github.com/pallets/werkzeug/blob/main/src/werkzeug/datastructures/headers.py

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

ddtrace/appsec/_iast/_handlers.py

@@ -82,23 +82,28 @@ def _on_flask_patch(flask_version):
             "Headers.items",
             functools.partial(if_iast_taint_yield_tuple_for, (OriginType.HEADER_NAME, OriginType.HEADER)),
         )
-        _set_metric_iast_instrumented_source(OriginType.HEADER_NAME)
-        _set_metric_iast_instrumented_source(OriginType.HEADER)
 
         try_wrap_function_wrapper(
             "werkzeug.datastructures",
-            "ImmutableMultiDict.__getitem__",
-            functools.partial(if_iast_taint_returned_object_for, OriginType.PARAMETER),
+            "EnvironHeaders.__getitem__",
+            functools.partial(if_iast_taint_returned_object_for, OriginType.HEADER),
         )
-        _set_metric_iast_instrumented_source(OriginType.PARAMETER)
-
+        # Since werkzeug 3.1.0 get doesn't call to __getitem__
         try_wrap_function_wrapper(
             "werkzeug.datastructures",
-            "EnvironHeaders.__getitem__",
+            "EnvironHeaders.get",
             functools.partial(if_iast_taint_returned_object_for, OriginType.HEADER),
         )
+        _set_metric_iast_instrumented_source(OriginType.HEADER_NAME)
         _set_metric_iast_instrumented_source(OriginType.HEADER)
 
+        try_wrap_function_wrapper(
+            "werkzeug.datastructures",
+            "ImmutableMultiDict.__getitem__",
+            functools.partial(if_iast_taint_returned_object_for, OriginType.PARAMETER),
+        )
+        _set_metric_iast_instrumented_source(OriginType.PARAMETER)
+
         if flask_version >= (2, 0, 0):
             # instance.query_string: raising an error on werkzeug/_internal.py "AttributeError: read only property"
             try_wrap_function_wrapper("werkzeug.wrappers.request", "Request.__init__", _on_request_init)

hatch.toml

@@ -399,6 +399,13 @@ flask = ["~=2.2"]
 python = ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
 flask = ["~=3.0"]
 
+[[envs.appsec_integrations_flask.matrix]]
+# werkzeug 3.1 drops support for py3.8
+python = ["3.11", "3.12", "3.13"]
+flask = ["~=3.1"]
+werkzeug = ["~=3.1"]
+
+## ASM appsec_integrations_fastapi
 
 [envs.appsec_integrations_fastapi]
 template = "appsec_integrations_fastapi"

tests/appsec/integrations/flask_tests/test_iast_flask.py

@@ -166,6 +166,62 @@ def sqli_2(param_str):
             assert vulnerability["location"]["path"] == TEST_FILE_PATH
             assert vulnerability["hash"] == hash_value
 
+    @pytest.mark.skipif(not asm_config._iast_supported, reason="Python version not supported by IAST")
+    def test_flask_iast_enabled_http_request_header_get(self):
+        @self.app.route("/sqli/<string:param_str>/", methods=["GET", "POST"])
+        def sqli_2(param_str):
+            import sqlite3
+
+            from flask import request
+
+            from ddtrace.appsec._iast._taint_tracking.aspects import add_aspect
+
+            con = sqlite3.connect(":memory:")
+            cur = con.cursor()
+            # label test_flask_iast_enabled_http_request_header_get
+            cur.execute(add_aspect("SELECT 1 FROM ", request.headers.get("User-Agent")))
+
+            return "OK", 200
+
+        with override_global_config(
+            dict(
+                _iast_enabled=True,
+                _iast_deduplication_enabled=False,
+            )
+        ):
+            resp = self.client.post(
+                "/sqli/sqlite_master/", data={"name": "test"}, headers={"User-Agent": "sqlite_master"}
+            )
+            assert resp.status_code == 200
+
+            root_span = self.pop_spans()[0]
+            assert root_span.get_metric(IAST.ENABLED) == 1.0
+
+            loaded = json.loads(root_span.get_tag(IAST.JSON))
+            assert loaded["sources"] == [
+                {"origin": "http.request.header", "name": "User-Agent", "value": "sqlite_master"}
+            ]
+
+            line, hash_value = get_line_and_hash(
+                "test_flask_iast_enabled_http_request_header_get",
+                VULN_SQL_INJECTION,
+                filename=TEST_FILE_PATH,
+            )
+            vulnerability = loaded["vulnerabilities"][0]
+
+            assert vulnerability["type"] == VULN_SQL_INJECTION
+            assert vulnerability["evidence"] == {
+                "valueParts": [
+                    {"value": "SELECT "},
+                    {"redacted": True},
+                    {"value": " FROM "},
+                    {"value": "sqlite_master", "source": 0},
+                ]
+            }
+            assert vulnerability["location"]["line"] == line
+            assert vulnerability["location"]["path"] == TEST_FILE_PATH
+            assert vulnerability["hash"] == hash_value
+
     @pytest.mark.skipif(not asm_config._iast_supported, reason="Python version not supported by IAST")
     def test_flask_full_sqli_iast_enabled_http_request_header_name_keys(self):
         @self.app.route("/sqli/<string:param_str>/", methods=["GET", "POST"])