CORS 策略：對預檢請求的回應未通過存取控制檢查：無“Access-Control-Allow-Origin”

問題內容

我在後端使用 golang 和 gin-gonic/gin web 框架，在前端使用 react axios。我已經嘗試解決它兩天了，但我仍然遇到以下相同的錯誤：

cors policy: response to preflight request doesn't pass access control check: no 'access-control-allow-origin' header is present on the requested resource.

僅當我嘗試發送 patch 請求時才會發生此錯誤，因此該請求需要預檢 options 請求，但 get 和 post 一切都按預期工作，它們不運行任何預檢檢查。

這是我的路由器設定的程式碼：

package main

import (
    "book_renting/api"
    "log"
    "net/http"

    "github.com/gin-contrib/sessions"
    "github.com/gin-contrib/sessions/cookie"
    "github.com/gin-gonic/contrib/cors"
    "github.com/gin-gonic/gin"
    _ "github.com/lib/pq"
)

func main() {

    router := gin.default()
    store := cookie.newstore([]byte("your-secret-key"))
    store.options(sessions.options{maxage: 60 * 60 * 24})

    router.use(cors.default())
    router.use(sessions.sessions("sessions", store))

    router.use(func(c *gin.context) {
        host := c.request.header.get("origin")
        c.writer.header().set("access-control-allow-origin", host)
        c.writer.header().set("access-control-allow-credentials", "true")
        c.writer.header().set("access-control-allow-headers", "content-type, authorization")
        c.writer.header().set("access-control-allow-methods", "get, post, put, delete, patch, options")
        if c.request.method == "options" {
            log.println("handling options request")
            c.abortwithstatus(http.statusnocontent)
            return
        }
        log.println("executing cors middleware")
        c.next()
    })

    router.post("/login", api.handlelogin)
    router.get("/logout", api.handlelogout)
    router.post("/register", api.handleregister)
    router.get("/getcookie", api.getcookiesession)

    router.get("/books", api.getbooksapi)
    router.get("/books/:id", api.bookbyidapi)
    router.patch("/rent/:id", api.rentbookapi)
    router.patch("/return/:id", api.returnbookapi)
    router.run("localhost:3000")
}

這是前端：

import axios from 'axios'

const url = 'http://localhost:3000'

export const loginuser = async (credentials) => await axios.post(`${url}/login`, credentials, {withcredentials: true})
export const logoutuser = async () => await axios.get(`${url}/logout`, {withcredentials: true})
export const registeruser = () => axios.post(`${url}/register`)
export const fetchbooks = () => axios.get(`${url}/books`, { withcredentials: true })
export const fetchbookbyid = (book_id) => axios.get(`${url}/books/${book_id}`, { withcredentials: true })
export const rentbook = (book_id) => axios.patch(`${url}/rent/${book_id}`, { withcredentials: true })
export const returnbook = (book_id) => axios.patch(`${url}/return/${book_id}`, { withcredentials: true })

我非常確定我正確設定了後端，它應該會傳回所有必要的標頭。

例如，對於 get 請求，回應標頭如下所示：

http/1.1 200 ok
access-control-allow-credentials: true
access-control-allow-headers: content-type, authorization
access-control-allow-methods: get, post, put, delete, patch, options
access-control-allow-origin: http://localhost:3001
content-type: application/json; charset=utf-8
date: sat, 10 jun 2023 22:12:11 gmt
content-length: 495

雖然對於 patch 請求嘗試，我沒有任何回應（毫不奇怪），並且預檢回應標頭是：

http/1.1 200 ok
date: sat, 10 jun 2023 22:12:12 gmt
content-length: 0

您對可能出現的問題有什麼建議嗎？經過這兩天我已經毫無頭緒了。預先感謝您！

我還嘗試新增標題：

c.writer.header().set("access-control-allow-origin", host)
        c.writer.header().set("access-control-allow-credentials", "true")
        c.writer.header().set("access-control-allow-headers", "content-type, authorization")
        c.writer.header().set("access-control-allow-methods", "get, post, put, delete, patch, options")

...再次在 if 語句中：

if c.request.method == "options" {
    log.println("handling options request")
    c.abortwithstatus(http.statusnocontent)
    return
    }

但這根本沒有幫助。事實上，這個if語句在執行預檢時並沒有執行，我從控制台知道伺服器正在執行options請求。

[gin] 2023/06/11 - 00:12:13 | 200 |       7.708µs |       127.0.0.1 | options  "/rent/2"

編輯：

這是發送 patch 請求的 curl 命令（因此實際上這是預檢 options 請求）：

curl 'http://localhost:3000/return/2' \
  -x 'options' \
  -h 'accept: */*' \
  -h 'accept-language: en-us,en;q=0.9,pl-pl;q=0.8,pl;q=0.7' \
  -h 'access-control-request-headers: content-type' \
  -h 'access-control-request-method: patch' \
  -h 'cache-control: no-cache' \
  -h 'connection: keep-alive' \
  -h 'origin: http://localhost:3001' \
  -h 'pragma: no-cache' \
  -h 'referer: http://localhost:3001/' \
  -h 'sec-fetch-dest: empty' \
  -h 'sec-fetch-mode: cors' \
  -h 'sec-fetch-site: same-site' \
  -h 'user-agent: mozilla/5.0 (macintosh; intel mac os x 10_15_7) applewebkit/537.36 (khtml, like gecko) chrome/114.0.0.0 safari/537.36' \
  --compressed

對此請求的回應：

HTTP/1.1 200 OK
Date: Sun, 11 Jun 2023 01:22:57 GMT
Content-Length: 0

正確答案

事實證明，您正在使用已棄用的軟體包github.com/gin-gonic/contrib/cors 。您應該使用 github.com/gin-contrib/cors 代替。這是使用 github.com/gin-contrib/cors 的示範設定：

package main

import (
    "github.com/gin-contrib/cors"
    "github.com/gin-contrib/sessions"
    "github.com/gin-contrib/sessions/cookie"
    "github.com/gin-gonic/gin"
)

func main() {
    router := gin.default()

    config := cors.defaultconfig()
    config.addallowheaders("authorization")
    config.allowcredentials = true
    config.allowallorigins = false
    // i think you should whitelist a limited origins instead:
    //  config.allowallorigins = []{"xxxx", "xxxx"}
    config.alloworiginfunc = func(origin string) bool {
        return true
    }
    router.use(cors.new(config))

    store := cookie.newstore([]byte("your-secret-key"))
    store.options(sessions.options{maxage: 60 * 60 * 24})
    router.use(sessions.sessions("sessions", store))

    // routes below

    router.run("localhost:3000")
}

由於某種原因，patch 請求標頭缺少「cookie」標頭，儘管我使用了 withcredentials 參數。

axios.patch(`${url}/rent/${book_id}`, { withcredentials: true })

這裡 { withcredentials: true } 被視為數據，並且沒有配置。如果你沒有資料發送到伺服器，你應該這樣寫：

axios.patch(`${url}/rent/${book_id}`, null, { withCredentials: true })

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