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process the CORS options only once (as opposed to every time the CORS middleware is applied to a handler) #263

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process the CORS options only once (as opposed to every time the CORS middleware is applied to a handler) #263

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143 changes: 70 additions & 73 deletions cors.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,6 @@ import (
type CORSOption func(*cors) error

type cors struct {
h http.Handler
allowedHeaders []string
allowedMethods []string
allowedOrigins []string
Expand Down Expand Up @@ -47,93 +46,95 @@ const (
corsOriginMatchAll string = "*"
)

func (ch *cors) ServeHTTP(w http.ResponseWriter, r *http.Request) {
origin := r.Header.Get(corsOriginHeader)
if !ch.isOriginAllowed(origin) {
if r.Method != corsOptionMethod || ch.ignoreOptions {
ch.h.ServeHTTP(w, r)
}

return
}

if r.Method == corsOptionMethod {
if ch.ignoreOptions {
ch.h.ServeHTTP(w, r)
return
}
func (ch *cors) wrap(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
origin := r.Header.Get(corsOriginHeader)
if !ch.isOriginAllowed(origin) {
if r.Method != corsOptionMethod || ch.ignoreOptions {
h.ServeHTTP(w, r)
}

if _, ok := r.Header[corsRequestMethodHeader]; !ok {
w.WriteHeader(http.StatusBadRequest)
return
}

method := r.Header.Get(corsRequestMethodHeader)
if !ch.isMatch(method, ch.allowedMethods) {
w.WriteHeader(http.StatusMethodNotAllowed)
return
}
if r.Method == corsOptionMethod {
if ch.ignoreOptions {
h.ServeHTTP(w, r)
return
}

requestHeaders := strings.Split(r.Header.Get(corsRequestHeadersHeader), ",")
allowedHeaders := []string{}
for _, v := range requestHeaders {
canonicalHeader := http.CanonicalHeaderKey(strings.TrimSpace(v))
if canonicalHeader == "" || ch.isMatch(canonicalHeader, defaultCorsHeaders) {
continue
if _, ok := r.Header[corsRequestMethodHeader]; !ok {
w.WriteHeader(http.StatusBadRequest)
return
}

if !ch.isMatch(canonicalHeader, ch.allowedHeaders) {
w.WriteHeader(http.StatusForbidden)
method := r.Header.Get(corsRequestMethodHeader)
if !ch.isMatch(method, ch.allowedMethods) {
w.WriteHeader(http.StatusMethodNotAllowed)
return
}

allowedHeaders = append(allowedHeaders, canonicalHeader)
}
requestHeaders := strings.Split(r.Header.Get(corsRequestHeadersHeader), ",")
allowedHeaders := []string{}
for _, v := range requestHeaders {
canonicalHeader := http.CanonicalHeaderKey(strings.TrimSpace(v))
if canonicalHeader == "" || ch.isMatch(canonicalHeader, defaultCorsHeaders) {
continue
}

if len(allowedHeaders) > 0 {
w.Header().Set(corsAllowHeadersHeader, strings.Join(allowedHeaders, ","))
}
if !ch.isMatch(canonicalHeader, ch.allowedHeaders) {
w.WriteHeader(http.StatusForbidden)
return
}

if ch.maxAge > 0 {
w.Header().Set(corsMaxAgeHeader, strconv.Itoa(ch.maxAge))
}
allowedHeaders = append(allowedHeaders, canonicalHeader)
}

if len(allowedHeaders) > 0 {
w.Header().Set(corsAllowHeadersHeader, strings.Join(allowedHeaders, ","))
}

if ch.maxAge > 0 {
w.Header().Set(corsMaxAgeHeader, strconv.Itoa(ch.maxAge))
}

if !ch.isMatch(method, defaultCorsMethods) {
w.Header().Set(corsAllowMethodsHeader, method)
if !ch.isMatch(method, defaultCorsMethods) {
w.Header().Set(corsAllowMethodsHeader, method)
}
} else if len(ch.exposedHeaders) > 0 {
w.Header().Set(corsExposeHeadersHeader, strings.Join(ch.exposedHeaders, ","))
}
} else if len(ch.exposedHeaders) > 0 {
w.Header().Set(corsExposeHeadersHeader, strings.Join(ch.exposedHeaders, ","))
}

if ch.allowCredentials {
w.Header().Set(corsAllowCredentialsHeader, "true")
}
if ch.allowCredentials {
w.Header().Set(corsAllowCredentialsHeader, "true")
}

if len(ch.allowedOrigins) > 1 {
w.Header().Set(corsVaryHeader, corsOriginHeader)
}
if len(ch.allowedOrigins) > 1 {
w.Header().Set(corsVaryHeader, corsOriginHeader)
}

returnOrigin := origin
if ch.allowedOriginValidator == nil && len(ch.allowedOrigins) == 0 {
returnOrigin = "*"
} else {
for _, o := range ch.allowedOrigins {
// A configuration of * is different than explicitly setting an allowed
// origin. Returning arbitrary origin headers in an access control allow
// origin header is unsafe and is not required by any use case.
if o == corsOriginMatchAll {
returnOrigin = "*"
break
returnOrigin := origin
if ch.allowedOriginValidator == nil && len(ch.allowedOrigins) == 0 {
returnOrigin = "*"
} else {
for _, o := range ch.allowedOrigins {
// A configuration of * is different than explicitly setting an allowed
// origin. Returning arbitrary origin headers in an access control allow
// origin header is unsafe and is not required by any use case.
if o == corsOriginMatchAll {
returnOrigin = "*"
break
}
}
}
}
w.Header().Set(corsAllowOriginHeader, returnOrigin)
w.Header().Set(corsAllowOriginHeader, returnOrigin)

if r.Method == corsOptionMethod {
w.WriteHeader(ch.optionStatusCode)
return
}
ch.h.ServeHTTP(w, r)
if r.Method == corsOptionMethod {
w.WriteHeader(ch.optionStatusCode)
return
}
h.ServeHTTP(w, r)
})
}

// CORS provides Cross-Origin Resource Sharing middleware.
Expand All @@ -155,11 +156,7 @@ func (ch *cors) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// http.ListenAndServe(":8000", handlers.CORS()(r))
// }
func CORS(opts ...CORSOption) func(http.Handler) http.Handler {
return func(h http.Handler) http.Handler {
ch := parseCORSOptions(opts...)
ch.h = h
return ch
}
return parseCORSOptions(opts...).wrap
}

func parseCORSOptions(opts ...CORSOption) *cors {
Expand Down