Add option to enable http redirects. (#925)

Fixes #921

Signed-off-by: Ashutosh Narkar <[email protected]>

docs/book/language-reference.md

@@ -158,7 +158,7 @@ evaluation query will always return the same value.
 ### HTTP
 | Built-in | Inputs | Description |
 | ------- |--------|-------------|
-| <span class="opa-keep-it-together">``http.send(request, output)``</span> | 1 | ``http.send`` executes a HTTP request and returns the response.``request`` is an object containing keys ``method``, ``url`` and  optionally ``body``. For example, ``http.send({"method": "get", "url": "http://www.openpolicyagent.org/"}, output)``. ``output`` is an object containing keys ``status``, ``status_code`` and ``body`` which represent the HTTP status, status code and response body respectively. Sample output, ``{"status": "200 OK", "status_code": 200, "body": null``}|
+| <span class="opa-keep-it-together">``http.send(request, output)``</span> | 1 | ``http.send`` executes a HTTP request and returns the response.``request`` is an object containing keys ``method``, ``url`` and  optionally ``body`` and ``enable_redirect``. For example, ``http.send({"method": "get", "url": "http://www.openpolicyagent.org/"}, output)``. ``output`` is an object containing keys ``status``, ``status_code`` and ``body`` which represent the HTTP status, status code and response body respectively. Sample output, ``{"status": "200 OK", "status_code": 200, "body": null``}. By default, http redirects are not enabled. To enable, set ``enable_redirect`` to ``true``.|
 
 ### Rego
 | Built-in | Inputs | Description |

topdown/http.go

@@ -7,6 +7,8 @@ package topdown
 import (
 	"bytes"
 	"encoding/json"
+	"fmt"
+	"strconv"
 
 	"net/http"
 	"os"
@@ -19,7 +21,7 @@ import (
 
 const defaultHTTPRequestTimeout = time.Second * 5
 
-var allowedKeys = ast.NewSet(ast.StringTerm("method"), ast.StringTerm("url"), ast.StringTerm("body"))
+var allowedKeys = ast.NewSet(ast.StringTerm("method"), ast.StringTerm("url"), ast.StringTerm("body"), ast.StringTerm("enable_redirect"))
 var requiredKeys = ast.NewSet(ast.StringTerm("method"), ast.StringTerm("url"))
 
 var client *http.Client
@@ -50,8 +52,13 @@ func createHTTPClient() {
 	if timeoutDuration != "" {
 		timeout, _ = time.ParseDuration(timeoutDuration)
 	}
+
+	// create a http client with redirects disabled
 	client = &http.Client{
 		Timeout: timeout,
+		CheckRedirect: func(*http.Request, []*http.Request) error {
+			return http.ErrUseLastResponse
+		},
 	}
 }
 
@@ -82,20 +89,27 @@ func executeHTTPRequest(bctx BuiltinContext, obj ast.Object) (ast.Value, error)
 	var url string
 	var method string
 	var body *bytes.Buffer
+	var enableRedirect bool
 	for _, val := range obj.Keys() {
 		key, err := ast.JSON(val.Value)
 		if err != nil {
 			return nil, err
 		}
 		key = key.(string)
 
-		if key == "method" {
+		switch key {
+		case "method":
 			method = obj.Get(val).String()
 			method = strings.Trim(method, "\"")
-		} else if key == "url" {
+		case "url":
 			url = obj.Get(val).String()
 			url = strings.Trim(url, "\"")
-		} else {
+		case "enable_redirect":
+			enableRedirect, err = strconv.ParseBool(obj.Get(val).String())
+			if err != nil {
+				return nil, err
+			}
+		case "body":
 			bodyVal := obj.Get(val).Value
 			bodyValInterface, err := ast.JSON(bodyVal)
 			if err != nil {
@@ -107,9 +121,16 @@ func executeHTTPRequest(bctx BuiltinContext, obj ast.Object) (ast.Value, error)
 				return nil, err
 			}
 			body = bytes.NewBuffer(bodyValBytes)
+		default:
+			return nil, fmt.Errorf("Invalid Key %v", key)
 		}
 	}
 
+	// check if redirects are enabled
+	if enableRedirect {
+		client.CheckRedirect = nil
+	}
+
 	if body == nil {
 		body = bytes.NewBufferString("")
 	}

topdown/http_test.go

@@ -220,3 +220,50 @@ func TestInvalidKeyError(t *testing.T) {
 		runTopDownTestCase(t, data, tc.note, tc.rules, tc.expected)
 	}
 }
+
+// TestHTTPRedirectDisable tests redirects are not enabled by default
+func TestHTTPRedirectDisable(t *testing.T) {
+
+	// expected result
+	expectedResult := make(map[string]interface{})
+	expectedResult["status"] = "301 Moved Permanently"
+	expectedResult["status_code"] = http.StatusMovedPermanently
+	expectedResult["body"] = nil
+
+	resultObj, err := ast.InterfaceToValue(expectedResult)
+	if err != nil {
+		panic(err)
+	}
+
+	var testURL = "http://google.com"
+	data := loadSmallTestData()
+	rule := []string{fmt.Sprintf(
+		`p = x { http.send({"method": "get", "url": "%s"}, x) }`, testURL)}
+
+	// run the test
+	runTopDownTestCase(t, data, "http.send", rule, resultObj.String())
+
+}
+
+// TestHTTPRedirectEnable tests redirects are enabled
+func TestHTTPRedirectEnable(t *testing.T) {
+
+	// expected result
+	expectedResult := make(map[string]interface{})
+	expectedResult["status"] = "200 OK"
+	expectedResult["status_code"] = http.StatusOK
+	expectedResult["body"] = nil
+
+	resultObj, err := ast.InterfaceToValue(expectedResult)
+	if err != nil {
+		panic(err)
+	}
+
+	var testURL = "http://google.com"
+	data := loadSmallTestData()
+	rule := []string{fmt.Sprintf(
+		`p = x { http.send({"method": "get", "url": "%s", "enable_redirect": true}, x) }`, testURL)}
+
+	// run the test
+	runTopDownTestCase(t, data, "http.send", rule, resultObj.String())
+}