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authelia/internal/middlewares/cors.go
James Elliott 4ebd8fdf4e
feat(oidc): provide cors config including options handlers ()
This adjusts the CORS headers appropriately for OpenID Connect. This includes responding to OPTIONS requests appropriately. Currently this is only configured to operate when the Origin scheme is HTTPS; but can easily be expanded in the future to include additional Origins.
2022-04-07 10:58:51 +10:00

348 lines
10 KiB
Go

package middlewares
import (
"bytes"
"net/url"
"strconv"
"strings"
"github.com/valyala/fasthttp"
"github.com/authelia/authelia/v4/internal/utils"
)
// NewCORSPolicyBuilder returns a new CORSPolicyBuilder which is used to build a CORSPolicy which adds the Vary header
// with a value reflecting that the Origin header will Vary this response, then if the Origin header has a https scheme
// it makes the following additional adjustments: copies the Origin header to the Access-Control-Allow-Origin header
// effectively allowing all origins, sets the Access-Control-Allow-Credentials header to false which disallows CORS
// requests from sending cookies etc, sets the Access-Control-Allow-Headers header to the value specified by
// Access-Control-Request-Headers in the request excluding the Cookie/Authorization/Proxy-Authorization and special *
// values, sets Access-Control-Allow-Methods to the value specified by the Access-Control-Request-Method header, sets
// the Access-Control-Max-Age header to 100.
//
// These behaviours can be overridden by the With methods on the returned policy.
func NewCORSPolicyBuilder() (policy *CORSPolicyBuilder) {
return &CORSPolicyBuilder{
enabled: true,
maxAge: 100,
}
}
// CORSPolicyBuilder is a special middleware which provides CORS headers via handlers and middleware methods which can be
// configured. It aims to simplify CORS configurations.
type CORSPolicyBuilder struct {
enabled bool
varyOnly bool
varySet bool
methods []string
headers []string
origins []string
credentials bool
vary []string
maxAge int
}
// Build reads the CORSPolicyBuilder configuration and generates a CORSPolicy.
func (b *CORSPolicyBuilder) Build() (policy *CORSPolicy) {
policy = &CORSPolicy{
enabled: b.enabled,
varyOnly: b.varyOnly,
credentials: []byte(strconv.FormatBool(b.credentials)),
origins: b.buildOrigins(),
headers: b.buildHeaders(),
vary: b.buildVary(),
}
if len(b.methods) != 0 {
policy.methods = []byte(strings.Join(b.methods, ", "))
}
if b.maxAge <= 0 {
policy.maxAge = headerValueMaxAge
} else {
policy.maxAge = []byte(strconv.Itoa(b.maxAge))
}
return policy
}
func (b CORSPolicyBuilder) buildOrigins() (origins [][]byte) {
if len(b.origins) != 0 {
if len(b.origins) == 1 && b.origins[0] == "*" {
origins = append(origins, []byte(b.origins[0]))
} else {
for _, origin := range b.origins {
origins = append(origins, []byte(origin))
}
}
}
return origins
}
func (b CORSPolicyBuilder) buildHeaders() (headers []byte) {
if len(b.headers) != 0 {
h := b.headers
if b.credentials {
if !utils.IsStringInSliceFold(fasthttp.HeaderCookie, h) {
h = append(h, fasthttp.HeaderCookie)
}
if !utils.IsStringInSliceFold(fasthttp.HeaderAuthorization, h) {
h = append(h, fasthttp.HeaderAuthorization)
}
if !utils.IsStringInSliceFold(fasthttp.HeaderProxyAuthorization, h) {
h = append(h, fasthttp.HeaderProxyAuthorization)
}
}
headers = utils.JoinAndCanonicalizeHeaders(headerSeparator, h...)
}
return headers
}
func (b CORSPolicyBuilder) buildVary() (vary []byte) {
if b.varySet {
if len(b.vary) != 0 {
vary = utils.JoinAndCanonicalizeHeaders(headerSeparator, b.vary...)
}
} else {
if len(b.origins) == 1 && b.origins[0] == "*" {
vary = headerValueVaryWildcard
} else {
vary = headerValueVary
}
}
return vary
}
// WithEnabled changes the enabled state of the middleware. If the middleware is initialized with NewCORSPolicyBuilder this
// value will be true but this function can override the value. Setting it to false prevents the middleware from adding
// any CORS headers. The only effect this middleware has after disabling this is the HandleOPTIONS and HandleOnlyOPTIONS
// handlers still function to return a HTTP 204 No Content, with the Allow header communicating the available HTTP
// method verbs. The main benefit of this option is that you don't have to implement complex logic to add/remove the
// middleware, you can just add it with the Middleware method, and adjust it using the WithEnabled method.
func (b *CORSPolicyBuilder) WithEnabled(enabled bool) (policy *CORSPolicyBuilder) {
b.enabled = enabled
return b
}
// WithAllowedMethods takes a list or HTTP methods and adjusts the Access-Control-Allow-Methods header to respond with
// that value.
func (b *CORSPolicyBuilder) WithAllowedMethods(methods ...string) (policy *CORSPolicyBuilder) {
b.methods = methods
return b
}
// WithAllowedOrigins takes a list of origin strings and only applies the CORS policy if the origin matches one of these.
func (b *CORSPolicyBuilder) WithAllowedOrigins(origins ...string) (policy *CORSPolicyBuilder) {
b.origins = origins
return b
}
// WithAllowedHeaders takes a list of header strings and alters the default Access-Control-Allow-Headers header.
func (b *CORSPolicyBuilder) WithAllowedHeaders(headers ...string) (policy *CORSPolicyBuilder) {
b.headers = headers
return b
}
// WithAllowCredentials takes bool and alters the default Access-Control-Allow-Credentials header.
func (b *CORSPolicyBuilder) WithAllowCredentials(allow bool) (policy *CORSPolicyBuilder) {
b.credentials = allow
return b
}
// WithVary takes a list of header strings and alters the default Vary header.
func (b *CORSPolicyBuilder) WithVary(headers ...string) (policy *CORSPolicyBuilder) {
b.vary = headers
b.varySet = true
return b
}
// WithVaryOnly just adds the Vary header.
func (b *CORSPolicyBuilder) WithVaryOnly(varyOnly bool) (policy *CORSPolicyBuilder) {
b.varyOnly = varyOnly
return b
}
// WithMaxAge takes an integer and alters the default Access-Control-Max-Age header.
func (b *CORSPolicyBuilder) WithMaxAge(age int) (policy *CORSPolicyBuilder) {
b.maxAge = age
return b
}
// CORSPolicy is a middleware that handles adding CORS headers.
type CORSPolicy struct {
enabled bool
varyOnly bool
methods []byte
headers []byte
origins [][]byte
credentials []byte
vary []byte
maxAge []byte
}
// HandleOPTIONS is an OPTIONS handler that just adds CORS headers, the Allow header, and sets the status code to 204
// without a body. This handler should generally not be used without using WithAllowedMethods.
func (p CORSPolicy) HandleOPTIONS(ctx *fasthttp.RequestCtx) {
p.handleOPTIONS(ctx)
p.handle(ctx)
}
// HandleOnlyOPTIONS is an OPTIONS handler that just handles the Allow header, and sets the status code to 204
// without a body. This handler should generally not be used without using WithAllowedMethods.
func (p CORSPolicy) HandleOnlyOPTIONS(ctx *fasthttp.RequestCtx) {
p.handleOPTIONS(ctx)
}
// Middleware provides a middleware that adds the appropriate CORS headers for this CORSPolicyBuilder.
func (p CORSPolicy) Middleware(next fasthttp.RequestHandler) (handler fasthttp.RequestHandler) {
return func(ctx *fasthttp.RequestCtx) {
p.handle(ctx)
next(ctx)
}
}
func (p CORSPolicy) handle(ctx *fasthttp.RequestCtx) {
if !p.enabled {
return
}
p.handleVary(ctx)
if !p.varyOnly {
p.handleCORS(ctx)
}
}
func (p CORSPolicy) handleOPTIONS(ctx *fasthttp.RequestCtx) {
ctx.Response.ResetBody()
/* The OPTIONS method should not return a 204 as per the following specifications when read together:
RFC7231 (https://www.rfc-editor.org/rfc/rfc7231#section-4.3.7):
A server MUST generate a Content-Length field with a value of "0" if no payload body is to be sent in
the response.
RFC7230 (https://www.rfc-editor.org/rfc/rfc7230#section-3.3.2):
A server MUST NOT send a Content-Length header field in any response with a status code of 1xx (Informational)
or 204 (No Content).
*/
ctx.SetStatusCode(fasthttp.StatusOK)
ctx.Response.Header.SetBytesKV(headerContentLength, headerValueZero)
if len(p.methods) != 0 {
ctx.Response.Header.SetBytesKV(headerAllow, p.methods)
}
}
func (p CORSPolicy) handleVary(ctx *fasthttp.RequestCtx) {
if len(p.vary) != 0 {
ctx.Response.Header.SetBytesKV(headerVary, p.vary)
}
}
func (p CORSPolicy) handleCORS(ctx *fasthttp.RequestCtx) {
var (
originURL *url.URL
err error
)
origin := ctx.Request.Header.PeekBytes(headerOrigin)
// Skip processing of any `https` scheme URL that has not expressly been configured.
if originURL, err = url.Parse(string(origin)); err != nil || (originURL.Scheme != "https" && p.origins == nil) {
return
}
var allowedOrigin []byte
switch len(p.origins) {
case 0:
allowedOrigin = origin
default:
for i := 0; i < len(p.origins); i++ {
if bytes.Equal(p.origins[i], headerValueOriginWildcard) {
allowedOrigin = headerValueOriginWildcard
} else if bytes.Equal(p.origins[i], origin) {
allowedOrigin = origin
}
}
if len(allowedOrigin) == 0 {
return
}
}
ctx.Response.Header.SetBytesKV(headerAccessControlAllowOrigin, allowedOrigin)
if len(p.credentials) != 0 {
ctx.Response.Header.SetBytesKV(headerAccessControlAllowCredentials, p.credentials)
}
if len(p.maxAge) != 0 {
ctx.Response.Header.SetBytesKV(headerAccessControlMaxAge, p.maxAge)
}
p.handleAllowedHeaders(ctx)
p.handleAllowedMethods(ctx)
}
func (p CORSPolicy) handleAllowedMethods(ctx *fasthttp.RequestCtx) {
switch len(p.methods) {
case 0:
// TODO: It may be beneficial to be able to control this automatic behaviour.
if requestMethods := ctx.Request.Header.PeekBytes(headerAccessControlRequestMethod); requestMethods != nil {
ctx.Response.Header.SetBytesKV(headerAccessControlAllowMethods, requestMethods)
}
default:
ctx.Response.Header.SetBytesKV(headerAccessControlAllowMethods, p.methods)
}
}
func (p CORSPolicy) handleAllowedHeaders(ctx *fasthttp.RequestCtx) {
switch len(p.headers) {
case 0:
// TODO: It may be beneficial to be able to control this automatic behaviour.
if headers := ctx.Request.Header.PeekBytes(headerAccessControlRequestHeaders); headers != nil {
requestedHeaders := strings.Split(string(headers), ",")
allowHeaders := make([]string, 0, len(requestedHeaders))
for i := 0; i < len(requestedHeaders); i++ {
headerTrimmed := strings.Trim(requestedHeaders[i], " ")
if headerTrimmed == "*" {
continue
}
if bytes.Equal(p.credentials, headerValueTrue) ||
(!strings.EqualFold(fasthttp.HeaderCookie, headerTrimmed) &&
!strings.EqualFold(fasthttp.HeaderAuthorization, headerTrimmed) &&
!strings.EqualFold(fasthttp.HeaderProxyAuthorization, headerTrimmed)) {
allowHeaders = append(allowHeaders, headerTrimmed)
}
}
if len(allowHeaders) != 0 {
ctx.Response.Header.SetBytesKV(headerAccessControlAllowHeaders, []byte(strings.Join(allowHeaders, ", ")))
}
}
default:
ctx.Response.Header.SetBytesKV(headerAccessControlAllowHeaders, p.headers)
}
}