traefik/pkg/middlewares/headers/header.go

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package headers
import (
"context"
"net/http"
"strconv"
"strings"
"github.com/containous/traefik/v2/pkg/config/dynamic"
"github.com/containous/traefik/v2/pkg/log"
)
// Header is a middleware that helps setup a few basic security features.
// A single headerOptions struct can be provided to configure which features should be enabled,
// and the ability to override a few of the default values.
type Header struct {
next http.Handler
hasCustomHeaders bool
hasCorsHeaders bool
headers *dynamic.Headers
}
// NewHeader constructs a new header instance from supplied frontend header struct.
func NewHeader(next http.Handler, cfg dynamic.Headers) *Header {
hasCustomHeaders := cfg.HasCustomHeadersDefined()
hasCorsHeaders := cfg.HasCorsHeadersDefined()
ctx := log.With(context.Background(), log.Str(log.MiddlewareType, typeName))
handleDeprecation(ctx, &cfg)
return &Header{
next: next,
headers: &cfg,
hasCustomHeaders: hasCustomHeaders,
hasCorsHeaders: hasCorsHeaders,
}
}
func (s *Header) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
// Handle Cors headers and preflight if configured.
if isPreflight := s.processCorsHeaders(rw, req); isPreflight {
return
}
if s.hasCustomHeaders {
s.modifyCustomRequestHeaders(req)
}
// If there is a next, call it.
if s.next != nil {
s.next.ServeHTTP(newResponseModifier(rw, req, s.PostRequestModifyResponseHeaders), req)
}
}
// modifyCustomRequestHeaders sets or deletes custom request headers.
func (s *Header) modifyCustomRequestHeaders(req *http.Request) {
// Loop through Custom request headers
for header, value := range s.headers.CustomRequestHeaders {
switch {
case value == "":
req.Header.Del(header)
case strings.EqualFold(header, "Host"):
req.Host = value
default:
req.Header.Set(header, value)
}
}
}
// PostRequestModifyResponseHeaders set or delete response headers.
// This method is called AFTER the response is generated from the backend
// and can merge/override headers from the backend response.
func (s *Header) PostRequestModifyResponseHeaders(res *http.Response) error {
// Loop through Custom response headers
for header, value := range s.headers.CustomResponseHeaders {
if value == "" {
res.Header.Del(header)
} else {
res.Header.Set(header, value)
}
}
if res != nil && res.Request != nil {
originHeader := res.Request.Header.Get("Origin")
allowed, match := s.isOriginAllowed(originHeader)
if allowed {
res.Header.Set("Access-Control-Allow-Origin", match)
}
}
if s.headers.AccessControlAllowCredentials {
res.Header.Set("Access-Control-Allow-Credentials", "true")
}
if len(s.headers.AccessControlExposeHeaders) > 0 {
exposeHeaders := strings.Join(s.headers.AccessControlExposeHeaders, ",")
res.Header.Set("Access-Control-Expose-Headers", exposeHeaders)
}
if !s.headers.AddVaryHeader {
return nil
}
varyHeader := res.Header.Get("Vary")
if varyHeader == "Origin" {
return nil
}
if varyHeader != "" {
varyHeader += ","
}
varyHeader += "Origin"
res.Header.Set("Vary", varyHeader)
return nil
}
// processCorsHeaders processes the incoming request,
// and returns if it is a preflight request.
// If not a preflight, it handles the preRequestModifyCorsResponseHeaders.
func (s *Header) processCorsHeaders(rw http.ResponseWriter, req *http.Request) bool {
if !s.hasCorsHeaders {
return false
}
reqAcMethod := req.Header.Get("Access-Control-Request-Method")
originHeader := req.Header.Get("Origin")
if reqAcMethod != "" && originHeader != "" && req.Method == http.MethodOptions {
// If the request is an OPTIONS request with an Access-Control-Request-Method header,
// and Origin headers, then it is a CORS preflight request,
// and we need to build a custom response: https://www.w3.org/TR/cors/#preflight-request
if s.headers.AccessControlAllowCredentials {
rw.Header().Set("Access-Control-Allow-Credentials", "true")
}
allowHeaders := strings.Join(s.headers.AccessControlAllowHeaders, ",")
if allowHeaders != "" {
rw.Header().Set("Access-Control-Allow-Headers", allowHeaders)
}
allowMethods := strings.Join(s.headers.AccessControlAllowMethods, ",")
if allowMethods != "" {
rw.Header().Set("Access-Control-Allow-Methods", allowMethods)
}
allowed, match := s.isOriginAllowed(originHeader)
if allowed {
rw.Header().Set("Access-Control-Allow-Origin", match)
}
rw.Header().Set("Access-Control-Max-Age", strconv.Itoa(int(s.headers.AccessControlMaxAge)))
return true
}
return false
}
func (s *Header) isOriginAllowed(origin string) (bool, string) {
for _, item := range s.headers.AccessControlAllowOriginList {
if item == "*" || item == origin {
return true, item
}
}
return false, ""
}