[3006.x] Fix content-type backwards compatability

changelog/66127.fixed.md

@@ -0,0 +1 @@
+Fix content type backwards compatablity with http proxy post requests in the http utils module.

salt/utils/http.py

@@ -353,6 +353,19 @@ def query(
         agent = f"{agent} http.query()"
     header_dict["User-agent"] = agent
 
+    if (
+        proxy_host
+        and proxy_port
+        and method == "POST"
+        and "Content-Type" not in header_dict
+    ):
+        log.debug(
+            "Content-Type not provided for POST request, assuming application/x-www-form-urlencoded"
+        )
+        header_dict["Content-Type"] = "application/x-www-form-urlencoded"
+        if "Content-Length" not in header_dict:
+            header_dict["Content-Length"] = f"{len(data)}"
+
     if backend == "requests":
         sess = requests.Session()
         sess.auth = auth

tests/pytests/unit/utils/test_http.py

@@ -1,3 +1,5 @@
+import urllib
+
 import pytest
 import requests
 from pytestshellutils.utils import ports
@@ -309,3 +311,27 @@ def test_backends_decode_body_true(httpserver, backend):
     )
     body = ret.get("body", "")
     assert isinstance(body, str)
+
+
+def test_requests_post_content_type(httpserver):
+    url = httpserver.url_for("/post-content-type")
+    data = urllib.parse.urlencode({"payload": "test"})
+    opts = {
+        "proxy_host": "127.0.0.1",
+        "proxy_port": 88,
+    }
+    with patch("requests.Session") as mock_session:
+        sess = MagicMock()
+        sess.headers = {}
+        mock_session.return_value = sess
+        ret = http.query(
+            url,
+            method="POST",
+            data=data,
+            backend="tornado",
+            opts=opts,
+        )
+        assert "Content-Type" in sess.headers
+        assert sess.headers["Content-Type"] == "application/x-www-form-urlencoded"
+        assert "Content-Length" in sess.headers
+        assert sess.headers["Content-Length"] == "12"