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csrf.go
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csrf.go
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package csrf
import (
"crypto/sha1"
"encoding/base64"
"errors"
"io"
"github.com/dchest/uniuri"
"github.com/gin-contrib/sessions"
"github.com/gin-gonic/gin"
)
const (
csrfSecret = "csrfSecret"
csrfSalt = "csrfSalt"
csrfToken = "csrfToken"
)
var defaultIgnoreMethods = []string{"GET", "HEAD", "OPTIONS"}
var defaultErrorFunc = func(c *gin.Context) {
panic(errors.New("CSRF token mismatch"))
}
var defaultTokenGetter = func(c *gin.Context) string {
r := c.Request
if t := r.FormValue("_csrf"); len(t) > 0 {
return t
} else if t := r.URL.Query().Get("_csrf"); len(t) > 0 {
return t
} else if t := r.Header.Get("X-CSRF-TOKEN"); len(t) > 0 {
return t
} else if t := r.Header.Get("X-XSRF-TOKEN"); len(t) > 0 {
return t
}
return ""
}
// Options stores configurations for a CSRF middleware.
type Options struct {
Secret string
IgnoreMethods []string
ErrorFunc gin.HandlerFunc
TokenGetter func(c *gin.Context) string
}
func tokenize(secret, salt string) string {
h := sha1.New()
io.WriteString(h, salt+"-"+secret)
hash := base64.URLEncoding.EncodeToString(h.Sum(nil))
return hash
}
func inArray(arr []string, value string) bool {
inarr := false
for _, v := range arr {
if v == value {
inarr = true
break
}
}
return inarr
}
// Middleware validates CSRF token.
func Middleware(options Options) gin.HandlerFunc {
ignoreMethods := options.IgnoreMethods
errorFunc := options.ErrorFunc
tokenGetter := options.TokenGetter
if ignoreMethods == nil {
ignoreMethods = defaultIgnoreMethods
}
if errorFunc == nil {
errorFunc = defaultErrorFunc
}
if tokenGetter == nil {
tokenGetter = defaultTokenGetter
}
return func(c *gin.Context) {
session := sessions.Default(c)
c.Set(csrfSecret, options.Secret)
if inArray(ignoreMethods, c.Request.Method) {
c.Next()
return
}
salt, ok := session.Get(csrfSalt).(string)
if !ok || len(salt) == 0 {
errorFunc(c)
return
}
token := tokenGetter(c)
if tokenize(options.Secret, salt) != token {
errorFunc(c)
return
}
c.Next()
}
}
// GetToken returns a CSRF token.
func GetToken(c *gin.Context) string {
session := sessions.Default(c)
secret := c.MustGet(csrfSecret).(string)
if t, ok := c.Get(csrfToken); ok {
return t.(string)
}
salt, ok := session.Get(csrfSalt).(string)
if !ok {
salt = uniuri.New()
session.Set(csrfSalt, salt)
session.Save()
}
token := tokenize(secret, salt)
c.Set(csrfToken, token)
return token
}