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// Copyright 2013 Martini Authors
// Copyright 2014 The Macaron Authors
// Copyright 2021 The Gitea Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
// SPDX-License-Identifier: Apache-2.0
// a middleware that generates and validates CSRF tokens.
package context
import (
"html/template"
"net/http"
"strconv"
"time"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/util"
)
const (
CsrfHeaderName = "X-Csrf-Token"
CsrfFormName = "_csrf"
CsrfErrorString = "Invalid CSRF token."
)
// CSRFProtector represents a CSRF protector and is used to get the current token and validate the token.
type CSRFProtector interface {
// PrepareForSessionUser prepares the csrf protector for the current session user.
PrepareForSessionUser(ctx *Context)
// Validate validates the csrf token in http context.
Validate(ctx *Context)
// DeleteCookie deletes the csrf cookie
DeleteCookie(ctx *Context)
}
type csrfProtector struct {
opt CsrfOptions
// id must be unique per user.
id string
// token is the valid one which wil be used by end user and passed via header, cookie, or hidden form value.
token string
}
// CsrfOptions maintains options to manage behavior of Generate.
type CsrfOptions struct {
// The global secret value used to generate Tokens.
Secret string
// Cookie value used to set and get token.
Cookie string
// Cookie domain.
CookieDomain string
// Cookie path.
CookiePath string
CookieHTTPOnly bool
// SameSite set the cookie SameSite type
SameSite http.SameSite
// Set the Secure flag to true on the cookie.
Secure bool
// sessionKey is the key used for getting the unique ID per user.
sessionKey string
// oldSessionKey saves old value corresponding to sessionKey.
oldSessionKey string
}
func newCsrfCookie(opt *CsrfOptions, value string) *http.Cookie {
return &http.Cookie{
Name: opt.Cookie,
Value: value,
Path: opt.CookiePath,
Domain: opt.CookieDomain,
MaxAge: int(CsrfTokenTimeout.Seconds()),
Secure: opt.Secure,
HttpOnly: opt.CookieHTTPOnly,
SameSite: opt.SameSite,
}
}
func NewCSRFProtector(opt CsrfOptions) CSRFProtector {
if opt.Secret == "" {
panic("CSRF secret is empty but it must be set") // it shouldn't happen because it is always set in code
}
opt.Cookie = util.IfZero(opt.Cookie, "_csrf")
opt.CookiePath = util.IfZero(opt.CookiePath, "/")
opt.sessionKey = "uid"
opt.oldSessionKey = "_old_" + opt.sessionKey
return &csrfProtector{opt: opt}
}
func (c *csrfProtector) PrepareForSessionUser(ctx *Context) {
c.id = "0"
if uidAny := ctx.Session.Get(c.opt.sessionKey); uidAny != nil {
switch uidVal := uidAny.(type) {
case string:
c.id = uidVal
case int64:
c.id = strconv.FormatInt(uidVal, 10)
default:
log.Error("invalid uid type in session: %T", uidAny)
}
}
oldUID := ctx.Session.Get(c.opt.oldSessionKey)
uidChanged := oldUID == nil || oldUID.(string) != c.id
cookieToken := ctx.GetSiteCookie(c.opt.Cookie)
needsNew := true
if uidChanged {
_ = ctx.Session.Set(c.opt.oldSessionKey, c.id)
} else if cookieToken != "" {
// If cookie token presents, reuse existing unexpired token, else generate a new one.
if issueTime, ok := ParseCsrfToken(cookieToken); ok {
dur := time.Since(issueTime) // issueTime is not a monotonic-clock, the server time may change a lot to an early time.
if dur >= -CsrfTokenRegenerationInterval && dur <= CsrfTokenRegenerationInterval {
c.token = cookieToken
needsNew = false
}
}
}
if needsNew {
// FIXME: actionId.
c.token = GenerateCsrfToken(c.opt.Secret, c.id, "POST", time.Now())
cookie := newCsrfCookie(&c.opt, c.token)
ctx.Resp.Header().Add("Set-Cookie", cookie.String())
}
ctx.Data["CsrfToken"] = c.token
ctx.Data["CsrfTokenHtml"] = template.HTML(`<input type="hidden" name="_csrf" value="` + template.HTMLEscapeString(c.token) + `">`)
}
func (c *csrfProtector) validateToken(ctx *Context, token string) {
if !ValidCsrfToken(token, c.opt.Secret, c.id, "POST", time.Now()) {
c.DeleteCookie(ctx)
// currently, there should be no access to the APIPath with CSRF token. because templates shouldn't use the `/api/` endpoints.
// FIXME: distinguish what the response is for: HTML (web page) or JSON (fetch)
http.Error(ctx.Resp, CsrfErrorString, http.StatusBadRequest)
}
}
// Validate should be used as a per route middleware. It attempts to get a token from an "X-Csrf-Token"
// HTTP header and then a "_csrf" form value. If one of these is found, the token will be validated.
// If this validation fails, http.StatusBadRequest is sent.
func (c *csrfProtector) Validate(ctx *Context) {
if token := ctx.Req.Header.Get(CsrfHeaderName); token != "" {
c.validateToken(ctx, token)
return
}
if token := ctx.Req.FormValue(CsrfFormName); token != "" {
c.validateToken(ctx, token)
return
}
c.validateToken(ctx, "") // no csrf token, use an empty token to respond error
}
func (c *csrfProtector) DeleteCookie(ctx *Context) {
cookie := newCsrfCookie(&c.opt, "")
cookie.MaxAge = -1
ctx.Resp.Header().Add("Set-Cookie", cookie.String())
}
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