auth/internal/middleware/csrf.go

239 lines
6.0 KiB
Go

package middleware
import (
"context"
"crypto/subtle"
"errors"
"net/http"
"time"
"source.toby3d.me/toby3d/auth/internal/common"
"source.toby3d.me/toby3d/auth/internal/random"
)
type (
// CSRFConfig defines the config for CSRF middleware.
CSRFConfig struct {
// Skipper defines a function to skip middleware.
Skipper Skipper
// ErrorHandler defines a function which is executed for returning custom errors.
ErrorHandler CSRFErrorHandler
// TokenLookup is a string in the form of "<source>:<name>" or "<source>:<name>,<source>:<name>" that
// is used to extract token from the request.
// Optional. Default value "header:X-CSRF-Token".
// Possible values:
// - "header:<name>" or "header:<name>:<cut-prefix>"
// - "query:<name>"
// - "form:<name>"
// Multiple sources example:
// - "header:X-CSRF-Token,query:csrf"
TokenLookup string
// Context key to store generated CSRF token into context.
// Optional. Default value "csrf".
ContextKey string
// Name of the CSRF cookie. This cookie will store CSRF token.
// Optional. Default value "csrf".
CookieName string
// Domain of the CSRF cookie.
// Optional. Default value none.
CookieDomain string
// Path of the CSRF cookie.
// Optional. Default value none.
CookiePath string
// Max age (in seconds) of the CSRF cookie.
// Optional. Default value 86400 (24hr).
CookieMaxAge int
// Indicates SameSite mode of the CSRF cookie.
// Optional. Default value SameSiteDefaultMode.
CookieSameSite http.SameSite
// TokenLength is the length of the generated token.
// Optional. Default value 32.
TokenLength uint8
// Indicates if CSRF cookie is secure.
// Optional. Default value false.
CookieSecure bool
// Indicates if CSRF cookie is HTTP only.
// Optional. Default value false.
CookieHTTPOnly bool
}
// CSRFErrorHandler is a function which is executed for creating custom errors.
CSRFErrorHandler func(err error, w http.ResponseWriter, r *http.Request) error
)
// ErrCSRFInvalid is returned when CSRF check fails.
var ErrCSRFInvalid = errors.New("") // echo.NewHTTPError(http.StatusForbidden, "invalid csrf token")
// DefaultCSRFConfig is the default CSRF middleware config.
var DefaultCSRFConfig = CSRFConfig{
Skipper: DefaultSkipper,
TokenLength: 32,
TokenLookup: "header:" + common.HeaderXCSRFToken,
ContextKey: "csrf",
CookieName: "_csrf",
CookieMaxAge: 86400,
CookieSameSite: http.SameSiteDefaultMode,
}
// CSRF returns a Cross-Site Request Forgery (CSRF) middleware.
// See: https://en.wikipedia.org/wiki/Cross-site_request_forgery
func CSRF() Interceptor {
c := DefaultCSRFConfig
return CSRFWithConfig(c)
}
// CSRFWithConfig returns a CSRF middleware with config.
// See `CSRF()`.
func CSRFWithConfig(config CSRFConfig) Interceptor {
// Defaults
if config.Skipper == nil {
config.Skipper = DefaultCSRFConfig.Skipper
}
if config.TokenLength == 0 {
config.TokenLength = DefaultCSRFConfig.TokenLength
}
if config.TokenLookup == "" {
config.TokenLookup = DefaultCSRFConfig.TokenLookup
}
if config.ContextKey == "" {
config.ContextKey = DefaultCSRFConfig.ContextKey
}
if config.CookieName == "" {
config.CookieName = DefaultCSRFConfig.CookieName
}
if config.CookieMaxAge == 0 {
config.CookieMaxAge = DefaultCSRFConfig.CookieMaxAge
}
if config.CookieSameSite == http.SameSiteNoneMode {
config.CookieSecure = true
}
extractors, err := CreateExtractors(config.TokenLookup)
if err != nil {
panic(err)
}
return func(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
if config.Skipper(w, r) {
next(w, r)
return
}
token := ""
if k, err := r.Cookie(config.CookieName); err != nil {
token, _ = random.String(config.TokenLength) // Generate token
} else {
token = k.Value // Reuse token
}
switch r.Method {
case "", http.MethodGet, http.MethodHead, http.MethodOptions, http.MethodTrace:
default:
var lastExtractorErr, lastTokenErr error
outer:
for _, extractor := range extractors {
clientTokens, err := extractor(w, r)
if err != nil {
lastExtractorErr = err
continue
}
for _, clientToken := range clientTokens {
if validateCSRFToken(token, clientToken) {
lastTokenErr = nil
lastExtractorErr = nil
break outer
}
lastTokenErr = ErrCSRFInvalid
}
}
var finalErr error
if lastTokenErr != nil {
finalErr = lastTokenErr
} else if lastExtractorErr != nil {
switch {
case errors.Is(lastExtractorErr, errQueryExtractorValueMissing):
lastExtractorErr = errors.New("missing csrf token in the query string")
case errors.Is(lastExtractorErr, errFormExtractorValueMissing):
lastExtractorErr = errors.New("missing csrf token in the form parameter")
case errors.Is(lastExtractorErr, errHeaderExtractorValueMissing):
lastExtractorErr = errors.New("missing csrf token in request header")
}
finalErr = lastExtractorErr
}
if finalErr != nil {
if config.ErrorHandler != nil {
config.ErrorHandler(finalErr, w, r)
return
}
http.Error(w, finalErr.Error(), http.StatusBadRequest)
return
}
}
// Set CSRF cookie
cookie := new(http.Cookie)
cookie.Name = config.CookieName
cookie.Value = token
if config.CookiePath != "" {
cookie.Path = config.CookiePath
}
if config.CookieDomain != "" {
cookie.Domain = config.CookieDomain
}
if config.CookieSameSite != http.SameSiteDefaultMode {
cookie.SameSite = config.CookieSameSite
}
cookie.Expires = time.Now().Add(time.Duration(config.CookieMaxAge) * time.Second)
cookie.Secure = config.CookieSecure
cookie.HttpOnly = config.CookieHTTPOnly
http.SetCookie(w, cookie)
// Store token in the context
r = r.WithContext(context.WithValue(r.Context(), config.ContextKey, token))
// Protect clients from caching the response
w.Header().Add(common.HeaderVary, common.HeaderCookie)
next(w, r)
}
}
func validateCSRFToken(token, clientToken string) bool {
return subtle.ConstantTimeCompare([]byte(token), []byte(clientToken)) == 1
}