mirror of
https://github.com/labstack/echo.git
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212 lines
6.1 KiB
Go
212 lines
6.1 KiB
Go
package middleware
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import (
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"net/http"
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"regexp"
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"strconv"
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"strings"
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"github.com/labstack/echo/v4"
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)
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type (
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// CORSConfig defines the config for CORS middleware.
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CORSConfig struct {
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// Skipper defines a function to skip middleware.
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Skipper Skipper
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// AllowOrigin defines a list of origins that may access the resource.
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// Optional. Default value []string{"*"}.
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AllowOrigins []string `yaml:"allow_origins"`
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// AllowOriginFunc is a custom function to validate the origin. It takes the
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// origin as an argument and returns true if allowed or false otherwise. If
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// an error is returned, it is returned by the handler. If this option is
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// set, AllowOrigins is ignored.
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// Optional.
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AllowOriginFunc func(origin string) (bool, error) `yaml:"allow_origin_func"`
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// AllowMethods defines a list methods allowed when accessing the resource.
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// This is used in response to a preflight request.
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// Optional. Default value DefaultCORSConfig.AllowMethods.
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AllowMethods []string `yaml:"allow_methods"`
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// AllowHeaders defines a list of request headers that can be used when
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// making the actual request. This is in response to a preflight request.
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// Optional. Default value []string{}.
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AllowHeaders []string `yaml:"allow_headers"`
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// AllowCredentials indicates whether or not the response to the request
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// can be exposed when the credentials flag is true. When used as part of
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// a response to a preflight request, this indicates whether or not the
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// actual request can be made using credentials.
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// Optional. Default value false.
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AllowCredentials bool `yaml:"allow_credentials"`
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// ExposeHeaders defines a whitelist headers that clients are allowed to
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// access.
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// Optional. Default value []string{}.
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ExposeHeaders []string `yaml:"expose_headers"`
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// MaxAge indicates how long (in seconds) the results of a preflight request
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// can be cached.
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// Optional. Default value 0.
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MaxAge int `yaml:"max_age"`
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}
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)
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var (
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// DefaultCORSConfig is the default CORS middleware config.
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DefaultCORSConfig = CORSConfig{
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Skipper: DefaultSkipper,
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AllowOrigins: []string{"*"},
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AllowMethods: []string{http.MethodGet, http.MethodHead, http.MethodPut, http.MethodPatch, http.MethodPost, http.MethodDelete},
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}
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)
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// CORS returns a Cross-Origin Resource Sharing (CORS) middleware.
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// See: https://developer.mozilla.org/en/docs/Web/HTTP/Access_control_CORS
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func CORS() echo.MiddlewareFunc {
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return CORSWithConfig(DefaultCORSConfig)
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}
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// CORSWithConfig returns a CORS middleware with config.
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// See: `CORS()`.
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func CORSWithConfig(config CORSConfig) echo.MiddlewareFunc {
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// Defaults
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if config.Skipper == nil {
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config.Skipper = DefaultCORSConfig.Skipper
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}
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if len(config.AllowOrigins) == 0 {
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config.AllowOrigins = DefaultCORSConfig.AllowOrigins
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}
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if len(config.AllowMethods) == 0 {
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config.AllowMethods = DefaultCORSConfig.AllowMethods
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}
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allowOriginPatterns := []string{}
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for _, origin := range config.AllowOrigins {
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pattern := regexp.QuoteMeta(origin)
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pattern = strings.Replace(pattern, "\\*", ".*", -1)
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pattern = strings.Replace(pattern, "\\?", ".", -1)
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pattern = "^" + pattern + "$"
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allowOriginPatterns = append(allowOriginPatterns, pattern)
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}
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allowMethods := strings.Join(config.AllowMethods, ",")
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allowHeaders := strings.Join(config.AllowHeaders, ",")
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exposeHeaders := strings.Join(config.ExposeHeaders, ",")
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maxAge := strconv.Itoa(config.MaxAge)
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return func(next echo.HandlerFunc) echo.HandlerFunc {
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return func(c echo.Context) error {
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if config.Skipper(c) {
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return next(c)
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}
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req := c.Request()
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res := c.Response()
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origin := req.Header.Get(echo.HeaderOrigin)
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allowOrigin := ""
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preflight := req.Method == http.MethodOptions
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res.Header().Add(echo.HeaderVary, echo.HeaderOrigin)
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// No Origin provided
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if origin == "" {
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if !preflight {
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return next(c)
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}
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return c.NoContent(http.StatusNoContent)
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}
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if config.AllowOriginFunc != nil {
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allowed, err := config.AllowOriginFunc(origin)
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if err != nil {
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return err
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}
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if allowed {
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allowOrigin = origin
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}
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} else {
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// Check allowed origins
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for _, o := range config.AllowOrigins {
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if o == "*" && config.AllowCredentials {
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allowOrigin = origin
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break
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}
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if o == "*" || o == origin {
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allowOrigin = o
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break
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}
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if matchSubdomain(origin, o) {
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allowOrigin = origin
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break
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}
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}
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// Check allowed origin patterns
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for _, re := range allowOriginPatterns {
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if allowOrigin == "" {
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didx := strings.Index(origin, "://")
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if didx == -1 {
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continue
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}
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domAuth := origin[didx+3:]
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// to avoid regex cost by invalid long domain
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if len(domAuth) > 253 {
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break
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}
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if match, _ := regexp.MatchString(re, origin); match {
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allowOrigin = origin
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break
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}
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}
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}
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}
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// Origin not allowed
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if allowOrigin == "" {
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if !preflight {
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return next(c)
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}
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return c.NoContent(http.StatusNoContent)
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}
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// Simple request
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if !preflight {
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res.Header().Set(echo.HeaderAccessControlAllowOrigin, allowOrigin)
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if config.AllowCredentials {
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res.Header().Set(echo.HeaderAccessControlAllowCredentials, "true")
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}
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if exposeHeaders != "" {
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res.Header().Set(echo.HeaderAccessControlExposeHeaders, exposeHeaders)
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}
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return next(c)
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}
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// Preflight request
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res.Header().Add(echo.HeaderVary, echo.HeaderAccessControlRequestMethod)
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res.Header().Add(echo.HeaderVary, echo.HeaderAccessControlRequestHeaders)
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res.Header().Set(echo.HeaderAccessControlAllowOrigin, allowOrigin)
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res.Header().Set(echo.HeaderAccessControlAllowMethods, allowMethods)
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if config.AllowCredentials {
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res.Header().Set(echo.HeaderAccessControlAllowCredentials, "true")
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}
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if allowHeaders != "" {
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res.Header().Set(echo.HeaderAccessControlAllowHeaders, allowHeaders)
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} else {
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h := req.Header.Get(echo.HeaderAccessControlRequestHeaders)
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if h != "" {
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res.Header().Set(echo.HeaderAccessControlAllowHeaders, h)
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}
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}
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if config.MaxAge > 0 {
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res.Header().Set(echo.HeaderAccessControlMaxAge, maxAge)
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}
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return c.NoContent(http.StatusNoContent)
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}
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}
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}
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