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|
package middleware
import (
"net/http"
"strconv"
"strings"
"github.com/labstack/echo"
)
type (
// CORSConfig defines the config for CORS middleware.
CORSConfig struct {
// Skipper defines a function to skip middleware.
Skipper Skipper
// AllowOrigin defines a list of origins that may access the resource.
// Optional. Default value []string{"*"}.
AllowOrigins []string `yaml:"allow_origins"`
// AllowMethods defines a list methods allowed when accessing the resource.
// This is used in response to a preflight request.
// Optional. Default value DefaultCORSConfig.AllowMethods.
AllowMethods []string `yaml:"allow_methods"`
// AllowHeaders defines a list of request headers that can be used when
// making the actual request. This in response to a preflight request.
// Optional. Default value []string{}.
AllowHeaders []string `yaml:"allow_headers"`
// AllowCredentials indicates whether or not the response to the request
// can be exposed when the credentials flag is true. When used as part of
// a response to a preflight request, this indicates whether or not the
// actual request can be made using credentials.
// Optional. Default value false.
AllowCredentials bool `yaml:"allow_credentials"`
// ExposeHeaders defines a whitelist headers that clients are allowed to
// access.
// Optional. Default value []string{}.
ExposeHeaders []string `yaml:"expose_headers"`
// MaxAge indicates how long (in seconds) the results of a preflight request
// can be cached.
// Optional. Default value 0.
MaxAge int `yaml:"max_age"`
}
)
var (
// DefaultCORSConfig is the default CORS middleware config.
DefaultCORSConfig = CORSConfig{
Skipper: DefaultSkipper,
AllowOrigins: []string{"*"},
AllowMethods: []string{echo.GET, echo.HEAD, echo.PUT, echo.PATCH, echo.POST, echo.DELETE},
}
)
// CORS returns a Cross-Origin Resource Sharing (CORS) middleware.
// See: https://developer.mozilla.org/en/docs/Web/HTTP/Access_control_CORS
func CORS() echo.MiddlewareFunc {
return CORSWithConfig(DefaultCORSConfig)
}
// CORSWithConfig returns a CORS middleware with config.
// See: `CORS()`.
func CORSWithConfig(config CORSConfig) echo.MiddlewareFunc {
// Defaults
if config.Skipper == nil {
config.Skipper = DefaultCORSConfig.Skipper
}
if len(config.AllowOrigins) == 0 {
config.AllowOrigins = DefaultCORSConfig.AllowOrigins
}
if len(config.AllowMethods) == 0 {
config.AllowMethods = DefaultCORSConfig.AllowMethods
}
allowMethods := strings.Join(config.AllowMethods, ",")
allowHeaders := strings.Join(config.AllowHeaders, ",")
exposeHeaders := strings.Join(config.ExposeHeaders, ",")
maxAge := strconv.Itoa(config.MaxAge)
return func(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) error {
if config.Skipper(c) {
return next(c)
}
req := c.Request()
res := c.Response()
origin := req.Header.Get(echo.HeaderOrigin)
allowOrigin := ""
// Check allowed origins
for _, o := range config.AllowOrigins {
if o == "*" || o == origin {
allowOrigin = o
break
}
}
// Simple request
if req.Method != echo.OPTIONS {
res.Header().Add(echo.HeaderVary, echo.HeaderOrigin)
res.Header().Set(echo.HeaderAccessControlAllowOrigin, allowOrigin)
if config.AllowCredentials {
res.Header().Set(echo.HeaderAccessControlAllowCredentials, "true")
}
if exposeHeaders != "" {
res.Header().Set(echo.HeaderAccessControlExposeHeaders, exposeHeaders)
}
return next(c)
}
// Preflight request
res.Header().Add(echo.HeaderVary, echo.HeaderOrigin)
res.Header().Add(echo.HeaderVary, echo.HeaderAccessControlRequestMethod)
res.Header().Add(echo.HeaderVary, echo.HeaderAccessControlRequestHeaders)
res.Header().Set(echo.HeaderAccessControlAllowOrigin, allowOrigin)
res.Header().Set(echo.HeaderAccessControlAllowMethods, allowMethods)
if config.AllowCredentials {
res.Header().Set(echo.HeaderAccessControlAllowCredentials, "true")
}
if allowHeaders != "" {
res.Header().Set(echo.HeaderAccessControlAllowHeaders, allowHeaders)
} else {
h := req.Header.Get(echo.HeaderAccessControlRequestHeaders)
if h != "" {
res.Header().Set(echo.HeaderAccessControlAllowHeaders, h)
}
}
if config.MaxAge > 0 {
res.Header().Set(echo.HeaderAccessControlMaxAge, maxAge)
}
return c.NoContent(http.StatusNoContent)
}
}
}
|
