Allow to use regular expressions for AccessControlAllowOriginList

docs/content/middlewares/headers.md

@@ -306,7 +306,7 @@ The `accessControlAllowOriginList` indicates whether a resource can be shared by
 A wildcard origin `*` can also be configured, and will match all requests.
 If this value is set by a backend server, it will be overwritten by Traefik
 
-This value can contains a list of allowed origins.
+This value can contain a list of allowed origins.
 
 More information including how to use the settings can be found on:
 
@@ -316,6 +316,14 @@ More information including how to use the settings can be found on:
 
 Traefik no longer supports the null value, as it is [no longer recommended as a return value](https://w3c.github.io/webappsec-cors-for-developers/#avoid-returning-access-control-allow-origin-null).
 
+### `accessControlAllowOriginListRegex`
+
+The `accessControlAllowOriginListRegex` option is the counterpart of the `accessControlAllowOriginList` option with regular expressions instead of origin values.
+It will allow all origin that contains any match of a regular expression in the `accessControlAllowOriginList`.
+
+!!! tip
+    Regular expressions can be tested using online tools such as [Go Playground](https://play.golang.org/p/mWU9p-wk2ru) or the [Regex101](https://regex101.com/r/58sIgx/2).
+
 ### `accessControlExposeHeaders`
 
 The `accessControlExposeHeaders` indicates which headers are safe to expose to the api of a CORS API specification.

docs/content/reference/dynamic-configuration/docker-labels.yml

@@ -36,6 +36,7 @@
 - "traefik.http.middlewares.middleware10.headers.accesscontrolallowmethods=foobar, foobar"
 - "traefik.http.middlewares.middleware10.headers.accesscontrolalloworigin=foobar"
 - "traefik.http.middlewares.middleware10.headers.accesscontrolalloworiginlist=foobar, foobar"
+- "traefik.http.middlewares.middleware10.headers.accesscontrolalloworiginlistregex=foobar, foobar"
 - "traefik.http.middlewares.middleware10.headers.accesscontrolexposeheaders=foobar, foobar"
 - "traefik.http.middlewares.middleware10.headers.accesscontrolmaxage=42"
 - "traefik.http.middlewares.middleware10.headers.addvaryheader=true"

docs/content/reference/dynamic-configuration/file.toml

@@ -153,6 +153,7 @@
         accessControlAllowMethods = ["foobar", "foobar"]
         accessControlAllowOrigin = "foobar"
         accessControlAllowOriginList = ["foobar", "foobar"]
+        accessControlAllowOriginListRegex = ["foobar", "foobar"]
         accessControlExposeHeaders = ["foobar", "foobar"]
         accessControlMaxAge = 42
         addVaryHeader = true

docs/content/reference/dynamic-configuration/file.yaml

@@ -180,6 +180,9 @@ http:
         accessControlAllowOriginList:
         - foobar
         - foobar
+        accessControlAllowOriginListRegex:
+        - foobar
+        - foobar
         accessControlExposeHeaders:
         - foobar
         - foobar

docs/content/reference/dynamic-configuration/kv-ref.md

@@ -45,6 +45,8 @@
 | `traefik/http/middlewares/Middleware10/headers/accessControlAllowOrigin` | `foobar` |
 | `traefik/http/middlewares/Middleware10/headers/accessControlAllowOriginList/0` | `foobar` |
 | `traefik/http/middlewares/Middleware10/headers/accessControlAllowOriginList/1` | `foobar` |
+| `traefik/http/middlewares/Middleware10/headers/accessControlAllowOriginListRegex/0` | `foobar` |
+| `traefik/http/middlewares/Middleware10/headers/accessControlAllowOriginListRegex/1` | `foobar` |
 | `traefik/http/middlewares/Middleware10/headers/accessControlExposeHeaders/0` | `foobar` |
 | `traefik/http/middlewares/Middleware10/headers/accessControlExposeHeaders/1` | `foobar` |
 | `traefik/http/middlewares/Middleware10/headers/accessControlMaxAge` | `42` |

pkg/config/dynamic/middlewares.go

@@ -164,6 +164,8 @@ type Headers struct {
 	AccessControlAllowOrigin string `json:"accessControlAllowOrigin,omitempty" toml:"accessControlAllowOrigin,omitempty" yaml:"accessControlAllowOrigin,omitempty"` // Deprecated
 	// AccessControlAllowOriginList is a list of allowable origins. Can also be a wildcard origin "*".
 	AccessControlAllowOriginList []string `json:"accessControlAllowOriginList,omitempty" toml:"accessControlAllowOriginList,omitempty" yaml:"accessControlAllowOriginList,omitempty"`
+	// AccessControlAllowOriginListRegex is a list of allowable origins written following the Regular Expression syntax (https://golang.org/pkg/regexp/).
+	AccessControlAllowOriginListRegex []string `json:"accessControlAllowOriginListRegex,omitempty" toml:"accessControlAllowOriginListRegex,omitempty" yaml:"accessControlAllowOriginListRegex,omitempty"`
 	// AccessControlExposeHeaders sets valid headers for the response.
 	AccessControlExposeHeaders []string `json:"accessControlExposeHeaders,omitempty" toml:"accessControlExposeHeaders,omitempty" yaml:"accessControlExposeHeaders,omitempty"`
 	// AccessControlMaxAge sets the time that a preflight request may be cached.
@@ -206,6 +208,7 @@ func (h *Headers) HasCorsHeadersDefined() bool {
 		len(h.AccessControlAllowHeaders) != 0 ||
 		len(h.AccessControlAllowMethods) != 0 ||
 		len(h.AccessControlAllowOriginList) != 0 ||
+		len(h.AccessControlAllowOriginListRegex) != 0 ||
 		len(h.AccessControlExposeHeaders) != 0 ||
 		h.AccessControlMaxAge != 0 ||
 		h.AddVaryHeader)

pkg/config/label/label_test.go

@@ -49,6 +49,7 @@ func TestDecodeConfiguration(t *testing.T) {
 		"traefik.http.middlewares.Middleware8.headers.accesscontrolallowmethods":                   "GET, PUT",
 		"traefik.http.middlewares.Middleware8.headers.accesscontrolalloworigin":                    "foobar",
 		"traefik.http.middlewares.Middleware8.headers.accesscontrolalloworiginList":                "foobar, fiibar",
+		"traefik.http.middlewares.Middleware8.headers.accesscontrolalloworiginListRegex":           "foobar, fiibar",
 		"traefik.http.middlewares.Middleware8.headers.accesscontrolexposeheaders":                  "X-foobar, X-fiibar",
 		"traefik.http.middlewares.Middleware8.headers.accesscontrolmaxage":                         "200",
 		"traefik.http.middlewares.Middleware8.headers.addvaryheader":                               "true",
@@ -527,6 +528,10 @@ func TestDecodeConfiguration(t *testing.T) {
 							"foobar",
 							"fiibar",
 						},
+						AccessControlAllowOriginListRegex: []string{
+							"foobar",
+							"fiibar",
+						},
 						AccessControlExposeHeaders: []string{
 							"X-foobar",
 							"X-fiibar",
@@ -999,6 +1004,10 @@ func TestEncodeConfiguration(t *testing.T) {
 							"foobar",
 							"fiibar",
 						},
+						AccessControlAllowOriginListRegex: []string{
+							"foobar",
+							"fiibar",
+						},
 						AccessControlExposeHeaders: []string{
 							"X-foobar",
 							"X-fiibar",
@@ -1155,6 +1164,7 @@ func TestEncodeConfiguration(t *testing.T) {
 		"traefik.HTTP.Middlewares.Middleware8.Headers.AccessControlAllowMethods":                   "GET, PUT",
 		"traefik.HTTP.Middlewares.Middleware8.Headers.AccessControlAllowOrigin":                    "foobar",
 		"traefik.HTTP.Middlewares.Middleware8.Headers.AccessControlAllowOriginList":                "foobar, fiibar",
+		"traefik.HTTP.Middlewares.Middleware8.Headers.AccessControlAllowOriginListRegex":           "foobar, fiibar",
 		"traefik.HTTP.Middlewares.Middleware8.Headers.AccessControlExposeHeaders":                  "X-foobar, X-fiibar",
 		"traefik.HTTP.Middlewares.Middleware8.Headers.AccessControlMaxAge":                         "200",
 		"traefik.HTTP.Middlewares.Middleware8.Headers.AddVaryHeader":                               "true",

pkg/middlewares/headers/header.go

@@ -2,7 +2,9 @@ package headers
 
 import (
 	"context"
+	"fmt"
 	"net/http"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -18,22 +20,33 @@ type Header struct {
 	hasCustomHeaders   bool
 	hasCorsHeaders     bool
 	headers            *dynamic.Headers
+	allowOriginRegexes []*regexp.Regexp
 }
 
 // NewHeader constructs a new header instance from supplied frontend header struct.
-func NewHeader(next http.Handler, cfg dynamic.Headers) *Header {
+func NewHeader(next http.Handler, cfg dynamic.Headers) (*Header, error) {
 	hasCustomHeaders := cfg.HasCustomHeadersDefined()
 	hasCorsHeaders := cfg.HasCorsHeadersDefined()
 
 	ctx := log.With(context.Background(), log.Str(log.MiddlewareType, typeName))
 	handleDeprecation(ctx, &cfg)
 
+	regexes := make([]*regexp.Regexp, len(cfg.AccessControlAllowOriginListRegex))
+	for i, str := range cfg.AccessControlAllowOriginListRegex {
+		reg, err := regexp.Compile(str)
+		if err != nil {
+			return nil, fmt.Errorf("error occurred during origin parsing: %w", err)
+		}
+		regexes[i] = reg
+	}
+
 	return &Header{
 		next:               next,
 		headers:            &cfg,
 		hasCustomHeaders:   hasCustomHeaders,
 		hasCorsHeaders:     hasCorsHeaders,
-	}
+		allowOriginRegexes: regexes,
+	}, nil
 }
 
 func (s *Header) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
@@ -166,5 +179,11 @@ func (s *Header) isOriginAllowed(origin string) (bool, string) {
 		}
 	}
 
+	for _, regex := range s.allowOriginRegexes {
+		if regex.MatchString(origin) {
+			return true, origin
+		}
+	}
+
 	return false, ""
 }

pkg/middlewares/headers/header_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 	"github.com/traefik/traefik/v2/pkg/config/dynamic"
 )
 
@@ -52,7 +53,8 @@ func TestNewHeader_customRequestHeader(t *testing.T) {
 		t.Run(test.desc, func(t *testing.T) {
 			t.Parallel()
 
-			mid := NewHeader(emptyHandler, test.cfg)
+			mid, err := NewHeader(emptyHandler, test.cfg)
+			require.NoError(t, err)
 
 			req := httptest.NewRequest(http.MethodGet, "/foo", nil)
 			req.Header.Set("Foo", "bar")
@@ -94,7 +96,8 @@ func TestNewHeader_customRequestHeader_Host(t *testing.T) {
 
 	for _, test := range testCases {
 		t.Run(test.desc, func(t *testing.T) {
-			mid := NewHeader(emptyHandler, dynamic.Headers{CustomRequestHeaders: test.customHeaders})
+			mid, err := NewHeader(emptyHandler, dynamic.Headers{CustomRequestHeaders: test.customHeaders})
+			require.NoError(t, err)
 
 			req := httptest.NewRequest(http.MethodGet, "http://example.org/foo", nil)
 
@@ -217,7 +220,8 @@ func TestNewHeader_CORSPreflights(t *testing.T) {
 
 	for _, test := range testCases {
 		t.Run(test.desc, func(t *testing.T) {
-			mid := NewHeader(emptyHandler, test.cfg)
+			mid, err := NewHeader(emptyHandler, test.cfg)
+			require.NoError(t, err)
 
 			req := httptest.NewRequest(http.MethodOptions, "/foo", nil)
 			req.Header = test.requestHeaders
@@ -240,6 +244,7 @@ func TestNewHeader_CORSResponses(t *testing.T) {
 		cfg            dynamic.Headers
 		requestHeaders http.Header
 		expected       http.Header
+		expectedError  bool
 	}{
 		{
 			desc: "Test Simple Request",
@@ -267,6 +272,54 @@ func TestNewHeader_CORSResponses(t *testing.T) {
 				"Access-Control-Allow-Origin": {"*"},
 			},
 		},
+		{
+			desc: "Regexp Origin Request",
+			next: emptyHandler,
+			cfg: dynamic.Headers{
+				AccessControlAllowOriginListRegex: []string{"^https?://([a-z]+)\\.bar\\.org$"},
+			},
+			requestHeaders: map[string][]string{
+				"Origin": {"https://foo.bar.org"},
+			},
+			expected: map[string][]string{
+				"Access-Control-Allow-Origin": {"https://foo.bar.org"},
+			},
+		},
+		{
+			desc: "Partial Regexp Origin Request",
+			next: emptyHandler,
+			cfg: dynamic.Headers{
+				AccessControlAllowOriginListRegex: []string{"([a-z]+)\\.bar"},
+			},
+			requestHeaders: map[string][]string{
+				"Origin": {"https://foo.bar.org"},
+			},
+			expected: map[string][]string{
+				"Access-Control-Allow-Origin": {"https://foo.bar.org"},
+			},
+		},
+		{
+			desc: "Regexp Malformed Origin Request",
+			next: emptyHandler,
+			cfg: dynamic.Headers{
+				AccessControlAllowOriginListRegex: []string{"a(b"},
+			},
+			requestHeaders: map[string][]string{
+				"Origin": {"https://foo.bar.org"},
+			},
+			expectedError: true,
+		},
+		{
+			desc: "Regexp Origin Request without matching",
+			next: emptyHandler,
+			cfg: dynamic.Headers{
+				AccessControlAllowOriginListRegex: []string{"([a-z]+)\\.bar\\.org"},
+			},
+			requestHeaders: map[string][]string{
+				"Origin": {"https://bar.org"},
+			},
+			expected: map[string][]string{},
+		},
 		{
 			desc: "Empty origin Request",
 			next: emptyHandler,
@@ -416,7 +469,12 @@ func TestNewHeader_CORSResponses(t *testing.T) {
 
 	for _, test := range testCases {
 		t.Run(test.desc, func(t *testing.T) {
-			mid := NewHeader(test.next, test.cfg)
+			mid, err := NewHeader(test.next, test.cfg)
+			if test.expectedError {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
 
 			req := httptest.NewRequest(http.MethodGet, "/foo", nil)
 			req.Header = test.requestHeaders
@@ -478,7 +536,8 @@ func TestNewHeader_customResponseHeaders(t *testing.T) {
 
 	for _, test := range testCases {
 		t.Run(test.desc, func(t *testing.T) {
-			mid := NewHeader(emptyHandler, dynamic.Headers{CustomResponseHeaders: test.config})
+			mid, err := NewHeader(emptyHandler, dynamic.Headers{CustomResponseHeaders: test.config})
+			require.NoError(t, err)
 
 			req := httptest.NewRequest(http.MethodGet, "/foo", nil)
 

pkg/middlewares/headers/headers.go

@@ -58,7 +58,11 @@ func New(ctx context.Context, next http.Handler, cfg dynamic.Headers, name strin
 
 	if hasCustomHeaders || hasCorsHeaders {
 		logger.Debugf("Setting up customHeaders/Cors from %v", cfg)
-		handler = NewHeader(nextHandler, cfg)
+		var err error
+		handler, err = NewHeader(nextHandler, cfg)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	return &headers{

pkg/provider/kv/kv_test.go

@@ -100,6 +100,8 @@ func Test_buildConfiguration(t *testing.T) {
 		"traefik/http/middlewares/Middleware09/headers/accessControlAllowOrigin":                     "foobar",
 		"traefik/http/middlewares/Middleware09/headers/accessControlAllowOriginList/0":               "foobar",
 		"traefik/http/middlewares/Middleware09/headers/accessControlAllowOriginList/1":               "foobar",
+		"traefik/http/middlewares/Middleware09/headers/accessControlAllowOriginListRegex/0":          "foobar",
+		"traefik/http/middlewares/Middleware09/headers/accessControlAllowOriginListRegex/1":          "foobar",
 		"traefik/http/middlewares/Middleware09/headers/contentTypeNosniff":                           "true",
 		"traefik/http/middlewares/Middleware09/headers/accessControlAllowCredentials":                "true",
 		"traefik/http/middlewares/Middleware09/headers/featurePolicy":                                "foobar",
@@ -557,6 +559,10 @@ func Test_buildConfiguration(t *testing.T) {
 							"foobar",
 							"foobar",
 						},
+						AccessControlAllowOriginListRegex: []string{
+							"foobar",
+							"foobar",
+						},
 						AccessControlExposeHeaders: []string{
 							"foobar",
 							"foobar",