Set allowed headers via API instead of defaulting to wildcard.

http/cors.go

@@ -9,11 +9,6 @@ import (
 	"github.com/hashicorp/vault/vault"
 )
 
-var preflightHeaders = map[string]string{
-	"Access-Control-Allow-Headers": "*",
-	"Access-Control-Max-Age":       "300",
-}
-
 var allowedMethods = []string{
 	http.MethodDelete,
 	http.MethodGet,
@@ -38,8 +33,7 @@ func wrapCORSHandler(h http.Handler, core *vault.Core) http.Handler {
 			return
 		}
 
-		// Return a 403 if the origin is not
-		// allowed to make cross-origin requests.
+		// Return a 403 if the origin is not allowed to make cross-origin requests.
 		if !corsConf.IsValidOrigin(origin) {
 			respondError(w, http.StatusForbidden, fmt.Errorf("origin not allowed"))
 			return
@@ -56,10 +50,9 @@ func wrapCORSHandler(h http.Handler, core *vault.Core) http.Handler {
 		// apply headers for preflight requests
 		if req.Method == http.MethodOptions {
 			w.Header().Set("Access-Control-Allow-Methods", strings.Join(allowedMethods, ","))
+			w.Header().Set("Access-Control-Allow-Headers", strings.Join(corsConf.AllowedHeaders, ","))
+			w.Header().Set("Access-Control-Max-Age", "300")
 
-			for k, v := range preflightHeaders {
-				w.Header().Set(k, v)
-			}
 			return
 		}
 

http/handler_test.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/hashicorp/go-cleanhttp"
@@ -21,7 +22,7 @@ func TestHandler_cors(t *testing.T) {
 
 	// Enable CORS and allow from any origin for testing.
 	corsConfig := core.CORSConfig()
-	err := corsConfig.Enable([]string{addr})
+	err := corsConfig.Enable([]string{addr}, nil)
 	if err != nil {
 		t.Fatalf("Error enabling CORS: %s", err)
 	}
@@ -78,7 +79,7 @@ func TestHandler_cors(t *testing.T) {
 	//
 	expHeaders := map[string]string{
 		"Access-Control-Allow-Origin":  addr,
-		"Access-Control-Allow-Headers": "*",
+		"Access-Control-Allow-Headers": strings.Join(stdAllowedHeaders, ","),
 		"Access-Control-Max-Age":       "300",
 		"Vary": "Origin",
 	}

http/sys_config_cors_test.go

@@ -0,0 +1,78 @@
+package http
+
+import (
+	"encoding/json"
+	"net/http"
+	"reflect"
+	"testing"
+
+	"github.com/hashicorp/vault/vault"
+)
+
+func TestSysConfigCors(t *testing.T) {
+	var resp *http.Response
+
+	core, _, token := vault.TestCoreUnsealed(t)
+	ln, addr := TestServer(t, core)
+	defer ln.Close()
+	TestServerAuth(t, addr, token)
+
+	corsConf := core.CORSConfig()
+
+	// Try to enable CORS without providing a value for allowed_origins
+	resp = testHttpPut(t, token, addr+"/v1/sys/config/cors", map[string]interface{}{
+		"allowed_headers": "X-Custom-Header",
+	})
+
+	testResponseStatus(t, resp, 500)
+
+	// Enable CORS, but provide an origin this time.
+	resp = testHttpPut(t, token, addr+"/v1/sys/config/cors", map[string]interface{}{
+		"allowed_origins": addr,
+		"allowed_headers": "X-Custom-Header",
+	})
+
+	testResponseStatus(t, resp, 204)
+
+	// Read the CORS configuration
+	resp = testHttpGet(t, token, addr+"/v1/sys/config/cors")
+	testResponseStatus(t, resp, 200)
+
+	var actual map[string]interface{}
+	var expected map[string]interface{}
+
+	lenStdHeaders := len(corsConf.AllowedHeaders)
+
+	expectedHeaders := make([]interface{}, lenStdHeaders)
+
+	for i := range corsConf.AllowedHeaders {
+		expectedHeaders[i] = corsConf.AllowedHeaders[i]
+	}
+
+	expected = map[string]interface{}{
+		"lease_id":       "",
+		"renewable":      false,
+		"lease_duration": json.Number("0"),
+		"wrap_info":      nil,
+		"warnings":       nil,
+		"auth":           nil,
+		"data": map[string]interface{}{
+			"enabled":         true,
+			"allowed_origins": []interface{}{addr},
+			"allowed_headers": expectedHeaders,
+		},
+		"enabled":         true,
+		"allowed_origins": []interface{}{addr},
+		"allowed_headers": expectedHeaders,
+	}
+
+	testResponseStatus(t, resp, 200)
+
+	testResponseBody(t, resp, &actual)
+	expected["request_id"] = actual["request_id"]
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("bad: expected: %#v\nactual: %#v", expected, actual)
+	}
+
+}

vault/core.go

@@ -459,8 +459,8 @@ func NewCore(conf *CoreConfig) (*Core, error) {
 		enableMlock:                      !conf.DisableMlock,
 	}
 
-	// Load CORS config and provide core
 	c.corsConfig = &CORSConfig{core: c}
+	// Load CORS config and provide a value for the core field.
 
 	// Wrap the physical backend in a cache layer if enabled and not already wrapped
 	if _, isCache := conf.Physical.(*physical.Cache); !conf.DisableCache && !isCache {

vault/cors.go

@@ -15,12 +15,24 @@ const (
 	CORSEnabled
 )
 
+var stdAllowedHeaders = []string{
+	"Content-Type",
+	"X-Requested-With",
+	"X-Vault-AWS-IAM-Server-ID",
+	"X-Vault-MFA",
+	"X-Vault-No-Request-Forwarding",
+	"X-Vault-Token",
+	"X-Vault-Wrap-Format",
+	"X-Vault-Wrap-TTL",
+}
+
 // CORSConfig stores the state of the CORS configuration.
 type CORSConfig struct {
 	sync.RWMutex   `json:"-"`
 	core           *Core
 	Enabled        uint32   `json:"enabled"`
 	AllowedOrigins []string `json:"allowed_origins,omitempty"`
+	AllowedHeaders []string `json:"allowed_headers,omitempty"`
 }
 
 func (c *Core) saveCORSConfig() error {
@@ -31,6 +43,7 @@ func (c *Core) saveCORSConfig() error {
 	}
 	c.corsConfig.RLock()
 	localConfig.AllowedOrigins = c.corsConfig.AllowedOrigins
+	localConfig.AllowedHeaders = c.corsConfig.AllowedHeaders
 	c.corsConfig.RUnlock()
 
 	entry, err := logical.StorageEntryJSON("cors", localConfig)
@@ -72,9 +85,9 @@ func (c *Core) loadCORSConfig() error {
 
 // Enable takes either a '*' or a comma-seprated list of URLs that can make
 // cross-origin requests to Vault.
-func (c *CORSConfig) Enable(urls []string) error {
+func (c *CORSConfig) Enable(urls []string, headers []string) error {
 	if len(urls) == 0 {
-		return errors.New("the list of allowed origins cannot be empty")
+		return errors.New("at least one origin or the wildcard must be provided.")
 	}
 
 	if strutil.StrListContains(urls, "*") && len(urls) > 1 {
@@ -83,6 +96,15 @@ func (c *CORSConfig) Enable(urls []string) error {
 
 	c.Lock()
 	c.AllowedOrigins = urls
+
+	// Start with the standard headers to Vault accepts.
+	c.AllowedHeaders = append(c.AllowedHeaders, stdAllowedHeaders...)
+
+	// Allow the user to add additional headers to the list of
+	// headers allowed on cross-origin requests.
+	if len(headers) > 0 {
+		c.AllowedHeaders = append(c.AllowedHeaders, headers...)
+	}
 	c.Unlock()
 
 	atomic.StoreUint32(&c.Enabled, CORSEnabled)
@@ -95,12 +117,16 @@ func (c *CORSConfig) IsEnabled() bool {
 	return atomic.LoadUint32(&c.Enabled) == CORSEnabled
 }
 
-// Disable sets CORS to disabled and clears the allowed origins
+// Disable sets CORS to disabled and clears the allowed origins & headers.
 func (c *CORSConfig) Disable() error {
 	atomic.StoreUint32(&c.Enabled, CORSDisabled)
 	c.Lock()
-	c.AllowedOrigins = []string(nil)
+
+	c.AllowedOrigins = nil
+	c.AllowedHeaders = nil
+
 	c.Unlock()
+
 	return c.core.saveCORSConfig()
 }
 

vault/logical_system.go

@@ -115,6 +115,10 @@ func NewSystemBackend(core *Core) *SystemBackend {
 						Type:        framework.TypeCommaStringSlice,
 						Description: "A comma-separated string or array of strings indicating origins that may make cross-origin requests.",
 					},
+					"allowed_headers": &framework.FieldSchema{
+						Type:        framework.TypeCommaStringSlice,
+						Description: "A comma-separated string or array of strings indicating headers that are allowed on cross-origin requests.",
+					},
 				},
 
 				Callbacks: map[logical.Operation]framework.OperationFunc{
@@ -854,6 +858,7 @@ func (b *SystemBackend) handleCORSRead(req *logical.Request, d *framework.FieldD
 	if enabled {
 		corsConf.RLock()
 		resp.Data["allowed_origins"] = corsConf.AllowedOrigins
+		resp.Data["allowed_headers"] = corsConf.AllowedHeaders
 		corsConf.RUnlock()
 	}
 
@@ -864,12 +869,13 @@ func (b *SystemBackend) handleCORSRead(req *logical.Request, d *framework.FieldD
 // cross-origin requests and sets the CORS enabled flag to true
 func (b *SystemBackend) handleCORSUpdate(req *logical.Request, d *framework.FieldData) (*logical.Response, error) {
 	origins := d.Get("allowed_origins").([]string)
+	headers := d.Get("allowed_headers").([]string)
 
-	return nil, b.Core.corsConfig.Enable(origins)
+	return nil, b.Core.corsConfig.Enable(origins, headers)
 }
 
-// handleCORSDelete clears the allowed origins and sets the CORS enabled flag
-// to false
+// handleCORSDelete sets the CORS enabled flag to false and clears the list of
+// allowed origins & headers.
 func (b *SystemBackend) handleCORSDelete(req *logical.Request, d *framework.FieldData) (*logical.Response, error) {
 	return nil, b.Core.corsConfig.Disable()
 }

vault/logical_system_test.go

@@ -56,6 +56,7 @@ func TestSystemConfigCORS(t *testing.T) {
 
 	req := logical.TestRequest(t, logical.UpdateOperation, "config/cors")
 	req.Data["allowed_origins"] = "http://www.example.com"
+	req.Data["allowed_headers"] = "X-Custom-Header"
 	_, err := b.HandleRequest(req)
 	if err != nil {
 		t.Fatal(err)
@@ -65,6 +66,7 @@ func TestSystemConfigCORS(t *testing.T) {
 		Data: map[string]interface{}{
 			"enabled":         true,
 			"allowed_origins": []string{"http://www.example.com"},
+			"allowed_headers": append(stdAllowedHeaders, "X-Custom-Header"),
 		},
 	}
 

website/source/api/system/config-cors.html.md

@@ -34,28 +34,40 @@ $ curl \
 ```json
 {
   "enabled": true,
-  "allowed_origins": "http://www.example.com"
+  "allowed_origins": ["http://www.example.com"],
+  "allowed_headers": [
+    "Content-Type",
+    "X-Requested-With",
+    "X-Vault-AWS-IAM-Server-ID",
+    "X-Vault-No-Request-Forwarding",
+    "X-Vault-Token",
+    "X-Vault-Wrap-Format",
+    "X-Vault-Wrap-TTL",
+  ]
 }
 ```
 
 ## Configure CORS Settings
 
 This endpoint allows configuring the origins that are permitted to make
-cross-origin requests.
+cross-origin requests, as well as headers that are allowed on cross-origin requests.
 
 | Method   | Path                         | Produces               |
 | :------- | :--------------------------- | :--------------------- |
 | `PUT`    | `/sys/config/cors` | `204 (empty body)` |
 
 ### Parameters
 
-- `allowed_origins` `(string or string array: "" or [])` – A wildcard (`*`), comma-delimited string, or array of strings specifying the origins that are permitted to make cross-origin requests.
+- `allowed_origins` `(string or string array: <required>)` – A wildcard (`*`), comma-delimited string, or array of strings specifying the origins that are permitted to make cross-origin requests.
+
+- `allowed_headers` `(string or string array: "" or [])` – A comma-delimited string or array of strings specifying headers that are permitted to be on cross-origin requests. Headers set via this parameter will be appended to the list of headers that Vault allows by default.
 
 ### Sample Payload
 
 ```json
 {
-  "allowed_origins": "*"
+  "allowed_origins": "*",
+  "allowed_headers": "X-Custom-Header"
 }
 ```