topdown: Return response headers with http.send

Previously we left them off the returned AST object, this will now
just massage them into valid types and pass them along into the
return value.

Fixes: #2238
Signed-off-by: Patrick East <east.patrick@gmail.com>

docs/content/policy-reference.md

@@ -593,6 +593,7 @@ The `response` object parameter will contain the following fields:
 | `status_code` | `number` | HTTP status code (e.g., `200`). |
 | `body` | `any` | Any JSON value. If the HTTP response message body was not deserialized from JSON, this field is set to `null`. |
 | `raw_body` | `string` | The entire raw HTTP response message body represented as a string. |
+| `headers` | `object` | An object containing the response headers. The values will be an array of strings, repeated headers are grouped under the same keys with all values in the array. |
 
 The table below shows examples of calling `http.send`:
 

topdown/http.go

@@ -397,11 +397,21 @@ func executeHTTPRequest(bctx BuiltinContext, obj ast.Object) (ast.Value, error)
 		json.NewDecoder(&buf).Decode(&resultBody)
 	}
 
+	respHeaders := map[string]interface{}{}
+	for headerName, values := range resp.Header {
+		var respValues []interface{}
+		for _, v := range values {
+			respValues = append(respValues, v)
+		}
+		respHeaders[headerName] = respValues
+	}
+
 	result := make(map[string]interface{})
 	result["status"] = resp.Status
 	result["status_code"] = resp.StatusCode
 	result["body"] = resultBody
 	result["raw_body"] = string(resultRawBody)
+	result["headers"] = respHeaders
 
 	resultObj, err := ast.InterfaceToValue(result)
 	if err != nil {