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package middleware
import (
"context"
"encoding/base64"
"net/http"
"os"
"time"
"github.com/haturatu/xsrftoken"
)
const (
xsrfHeaderName = "X-XSRF-Token"
xsrfFormField = "xsrf_token"
)
type xsrfContextKey string
const xsrfTokenKey = xsrfContextKey("xsrfToken")
// XSRF is a middleware that provides Cross-Site Request Forgery protection.
func XSRF(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
xsrfSecretBase64 := os.Getenv("XSRF_SECRET_KEY")
xsrfSecret, err := base64.StdEncoding.DecodeString(xsrfSecretBase64)
if err != nil {
http.Error(w, "XSRF configuration error: invalid base64 key", http.StatusInternalServerError)
return
}
if len(xsrfSecret) != 32 {
http.Error(w, "XSRF configuration error: key must be 32 bytes", http.StatusInternalServerError)
return
}
sessionID := getSessionID(r)
if r.Method == http.MethodPost || r.Method == http.MethodPut || r.Method == http.MethodDelete {
clientToken := r.Header.Get(xsrfHeaderName)
if clientToken == "" {
clientToken = r.FormValue(xsrfFormField)
}
if !xsrftoken.ValidFor(clientToken, string(xsrfSecret), sessionID, r.URL.Path, 15*time.Minute) {
http.Error(w, "Invalid XSRF token", http.StatusForbidden)
return
}
}
token := xsrftoken.Generate(string(xsrfSecret), sessionID, r.URL.Path)
ctx := context.WithValue(r.Context(), xsrfTokenKey, token)
r = r.WithContext(ctx)
next.ServeHTTP(w, r)
})
}
// GetXSRFToken retrieves the XSRF token from the request context.
func GetXSRFToken(r *http.Request) string {
if token, ok := r.Context().Value(xsrfTokenKey).(string); ok {
return token
}
return ""
}
func getSessionID(r *http.Request) string {
cookie, err := r.Cookie("auth_token")
if err != nil {
return ""
}
return cookie.Value
}
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