cors allow regex pattern

enable cors to use regex pattern for allowed origins

implementation is similar to another popular cors
middleware: https://github.com/astaxie/beego/blob/master/plugins/cors/cors.go#L196-L201

middleware/cors.go

@@ -2,6 +2,7 @@ package middleware
 
 import (
 	"net/http"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -76,6 +77,15 @@ func CORSWithConfig(config CORSConfig) echo.MiddlewareFunc {
 		config.AllowMethods = DefaultCORSConfig.AllowMethods
 	}
 
+	allowOriginPatterns := []string{}
+	for _, origin := range config.AllowOrigins {
+		pattern := regexp.QuoteMeta(origin)
+		pattern = strings.Replace(pattern, "\\*", ".*", -1)
+		pattern = strings.Replace(pattern, "\\?", ".", -1)
+		pattern = "^" + pattern + "$"
+		allowOriginPatterns = append(allowOriginPatterns, pattern)
+	}
+
 	allowMethods := strings.Join(config.AllowMethods, ",")
 	allowHeaders := strings.Join(config.AllowHeaders, ",")
 	exposeHeaders := strings.Join(config.ExposeHeaders, ",")
@@ -108,6 +118,26 @@ func CORSWithConfig(config CORSConfig) echo.MiddlewareFunc {
 				}
 			}
 
+			// Check allowed origin patterns
+			for _, re := range allowOriginPatterns {
+				if allowOrigin == "" {
+					didx := strings.Index(origin, "://")
+					if didx == -1 {
+						continue
+					}
+					domAuth := origin[didx+3:]
+					// to avoid regex cost by invalid long domain
+					if len(domAuth) > 253 {
+						break
+					}
+
+					if match, _ := regexp.MatchString(re, origin); match {
+						allowOrigin = origin
+						break
+					}
+				}
+			}
+
 			// Simple request
 			if req.Method != http.MethodOptions {
 				res.Header().Add(echo.HeaderVary, echo.HeaderOrigin)

middleware/cors_test.go

@@ -83,3 +83,141 @@ func TestCORS(t *testing.T) {
 	h(c)
 	assert.Equal(t, "http://bbb.example.com", rec.Header().Get(echo.HeaderAccessControlAllowOrigin))
 }
+
+func Test_allowOriginScheme(t *testing.T) {
+	tests := []struct {
+		domain, pattern string
+		expected        bool
+	}{
+		{
+			domain:   "http://example.com",
+			pattern:  "http://example.com",
+			expected: true,
+		},
+		{
+			domain:   "https://example.com",
+			pattern:  "https://example.com",
+			expected: true,
+		},
+		{
+			domain:   "http://example.com",
+			pattern:  "https://example.com",
+			expected: false,
+		},
+		{
+			domain:   "https://example.com",
+			pattern:  "http://example.com",
+			expected: false,
+		},
+	}
+
+	e := echo.New()
+	for _, tt := range tests {
+		req := httptest.NewRequest(http.MethodOptions, "/", nil)
+		rec := httptest.NewRecorder()
+		c := e.NewContext(req, rec)
+		req.Header.Set(echo.HeaderOrigin, tt.domain)
+		cors := CORSWithConfig(CORSConfig{
+			AllowOrigins: []string{tt.pattern},
+		})
+		h := cors(echo.NotFoundHandler)
+		h(c)
+
+		if tt.expected {
+			assert.Equal(t, tt.domain, rec.Header().Get(echo.HeaderAccessControlAllowOrigin))
+		} else {
+			assert.Equal(t, "", rec.Header().Get(echo.HeaderAccessControlAllowOrigin))
+		}
+	}
+}
+
+func Test_allowOriginSubdomain(t *testing.T) {
+	tests := []struct {
+		domain, pattern string
+		expected        bool
+	}{
+		{
+			domain:   "http://aaa.example.com",
+			pattern:  "http://*.example.com",
+			expected: true,
+		},
+		{
+			domain:   "http://bbb.aaa.example.com",
+			pattern:  "http://*.example.com",
+			expected: true,
+		},
+		{
+			domain:   "http://bbb.aaa.example.com",
+			pattern:  "http://*.aaa.example.com",
+			expected: true,
+		},
+		{
+			domain:   "http://aaa.example.com:8080",
+			pattern:  "http://*.example.com:8080",
+			expected: true,
+		},
+
+		{
+			domain:   "http://fuga.hoge.com",
+			pattern:  "http://*.example.com",
+			expected: false,
+		},
+		{
+			domain:   "http://ccc.bbb.example.com",
+			pattern:  "http://*.aaa.example.com",
+			expected: false,
+		},
+		{
+			domain: `http://1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890\
+		  .1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890\
+		  .1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890\
+		  .1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.example.com`,
+			pattern:  "http://*.example.com",
+			expected: false,
+		},
+		{
+			domain:   `http://1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.1234567890.example.com`,
+			pattern:  "http://*.example.com",
+			expected: false,
+		},
+		{
+			domain:   "http://ccc.bbb.example.com",
+			pattern:  "http://example.com",
+			expected: false,
+		},
+		{
+			domain:   "https://prod-preview--aaa.bbb.com",
+			pattern:  "https://*--aaa.bbb.com",
+			expected: true,
+		},
+		{
+			domain:   "http://ccc.bbb.example.com",
+			pattern:  "http://*.example.com",
+			expected: true,
+		},
+		{
+			domain:   "http://ccc.bbb.example.com",
+			pattern:  "http://foo.[a-z]*.example.com",
+			expected: false,
+		},
+	}
+
+	e := echo.New()
+	for _, tt := range tests {
+		req := httptest.NewRequest(http.MethodOptions, "/", nil)
+		rec := httptest.NewRecorder()
+		c := e.NewContext(req, rec)
+		req.Header.Set(echo.HeaderOrigin, tt.domain)
+		cors := CORSWithConfig(CORSConfig{
+			AllowOrigins: []string{tt.pattern},
+		})
+		h := cors(echo.NotFoundHandler)
+		h(c)
+
+		if tt.expected {
+			assert.Equal(t, tt.domain, rec.Header().Get(echo.HeaderAccessControlAllowOrigin))
+		} else {
+			assert.Equal(t, "", rec.Header().Get(echo.HeaderAccessControlAllowOrigin))
+		}
+	}
+}