最近幫看同事串 Sign In with Apple 好像有很多不順的地方，拿自己的 Apple developer 帳號試試 :P 相關文件：
- Sign in with Apple - https://developer.apple.com/sign-in-with-apple/get-started/
- How to use Sign in with Apple - https://support.apple.com/en-us/HT210318
- About Sign in with Apple - https://help.apple.com/developer-account/?lang=en#/devde676e696
- Sign in with Apple JS - https://developer.apple.com/documentation/signinwithapplejs
- Configuring Your Webpage for Sign In with Apple - https://developer.apple.com/documentation/signinwithapplejs/configuring_your_webpage_for_sign_in_with_apple
- Sign in with Apple REST API - https://developer.apple.com/documentation/signinwithapplerestapi
- Generate and validate tokens - https://developer.apple.com/documentation/signinwithapplerestapi/generate_and_validate_tokens
using the Elliptic Curve Digital Signature Algorithm (ECDSA) with the P-256 curve and the SHA-256 hash algorithm. Specify the value ES256 in the algorithm header key. Specify the key identifier in the kid attribute.
Certificates, Identifiers & Profiles -> More -> Sign In with Apple -> Configure
在添加網域進去之前，請記得先設定 SPF DNS Record，不然 Apple 一驗證不合 SPF 時，又得等 DNS Cache 更新等到天荒地老 Orz
在此先添加 Type=TXT 的 DNS Record 吧！
v=spf1 include:amazonses.com -all
接著用 dig 驗一下：
% dig -t txt appid.changyy.org
; <<>> DiG 9.10.6 <<>> -t txt appid.changyy.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47410
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;appid.changyy.org. IN TXT
;; ANSWER SECTION:
appid.changyy.org. 119 IN TXT "v=spf1 include:amazonses.com -all"
;; Query time: 56 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Wed Nov 20 00:48:09 CST 2019
;; MSG SIZE rcvd: 92
添加 appid.changyy.org 網域，按下 Register 時，接著努力驗證通過即可。如果沒有先添加 SPF 就會出現類似訊息：The domain 'appid.changyy.org' is not SPF compliant.
接著再回到 Apple Developer 網站繼續按 Register (不是立刻通過，要等 DNS Cache 過期)，就可以進行後續的認證了，如 https://appid.changyy.org/.well-known/apple-developer-domain-association.txt 配置等。接著又得搞 https 連線，又進入了 免費SSL/TLS憑證 - Let's Encrypt 與 NGINX 的設定 XD 在此不贅述。
終於可以進入 Apple Developer Account 其他設定了，首先要建立 Services IDs 時，會要求有一個 App ID 為 primary App ID ，這件事也代表 Sign In with Apple 的核心還是 App ，此例新建一個 App ID = org.changyy.apple.app-id 為例，並且在下方勾選 Sign In with Apple 且 Enable as a primary App ID。
接著，建立 Services IDs ：
Certificates, Identifiers & Profiles -> Identifiers -> Add -> Services IDs -> 建立一個 org.changyy.sign-in-with-apple 並啟用 Sign In with Apple -> Configure -> Web Domain = appid.changyy.org 而 Return URLs = https://appid.changyy.org/callback.php 並按 Add 和 Save -> 再按 Continue 完成
最後，再來建立一組 Key 用來溝通：
Certificates, Identifiers & Profiles -> Keys -> 添加一組 Key Name = SignInWithAppleKey，記得勾選 Sign In With Apple -> 點擊 Configure 挑選完 App ID 按 Save -> 最後會下載一個 AuthKey_KeyID.p8 檔案，就是後續溝通的項目。
如此一來，在上述的過程中可以得到以下關鍵物：
- Service ID Identifier = org.changyy.sign-in-with-apple (後續是 OAuth 的 Client_ID)
- Key ID = 在 *.p8 的檔名上，或是在 Certificates, Identifiers & Profiles -> Keys -> SignInWithAppleKey 瀏覽可看到
- Team ID = 在 Apple Developer 登入後右上角可看見，或是在 Certificates, Identifiers & Profiles -> Identifiers -> 隨意一組 App ID -> App ID Prefix 就有標記 (Team ID) 資訊
- Return URLs = 在 Service ID 內編輯的，如 https://appid.changyy.org/callback.php
把這些資訊弄個 JSON 紀錄：
$ cat settings.json
{
"CLIENT_ID": "org.changyy.sign-in-with-apple",
"SCOPES": "name email",
"REDIRECT_URI": "https://appid.changyy.org/callback.php",
"STATE": "",
"TEAM_ID": "YourTeamID",
"KID" : "YourKeyID",
"Key_P8_PATH" :"../keystore/AuthKey_YourKeyID.p8",
"" : ""
}
最後把 https://github.com/changyy/sign-in-with-apple-js 拿來用，在根目錄建立 keystore 並擺放 AuthKey_YourKeyID.p8 以及上述 settings.json 擺在 /path/sign-in-with-apple-js/php/settings.json ，在把 https://appid.changyy.org/ Document_Root 設定在此專案的 /path/sign-in-with-apple-js/php 目錄上，如此用 https://appid.changyy.org/ 時，就會有以下畫面：
點擊後就會被引導完成 Apple 登入，登入後會導向到 https://appid.changyy.org/callback.php 並且看到簡單的 OAUTH code 的使用：
網路上滿多人在討論 firebase/jwt 的用法，但其實在 2019/11/20 來看，firebase/jwt 仍就沒有完整 Sign In with Apple 所需的 JWT 編碼格式，我則是靠 Lcobucci/JWT 套件完成打通 Sign In with Apple 的，並且看懂為何 firebase/jwt 還不能打通 :P 拿著 Lcobucci/JWT 內的 MultibyteStringConverter 來小試身手果真就通了。再找個時間貢獻 firebase/jwt 來修正好了，這次為了檢驗 firebase/jwt 失敗問題，大概至少看了 5套 php-jwt 的寫法，結果大多都是從 luciferous/jwt fork 擴充的，這可是 2011 的程式呢。oepnssl = OpenSSL 1.1.1 11 Sep 2018 jwt_header = Array ( [typ] => JWT [alg] => ES256 [kid] => YourKeyID ) jwt_payload = Array ( [iss] => YourTeamID [iat] => 1574184061 [exp] => 1574187661 [aud] => https://appleid.apple.com [sub] => YourServiceID ) apple_public_keys = Array ( [keys] => Array ( [0] => Array ( [kty] => RSA [kid] => AIDOPK1 [use] => sig [alg] => RS256 [n] => lxrwmuYSAsTfn-lUu4goZSXBD9ackM9OJuwUVQHmbZo6GW4Fu_auUdN5zI7Y1dEDfgt7m7QXWbHuMD01HLnD4eRtY-RNwCWdjNfEaY_esUPY3OVMrNDI15Ns13xspWS3q-13kdGv9jHI28P87RvMpjz_JCpQ5IM44oSyRnYtVJO-320SB8E2Bw92pmrenbp67KRUzTEVfGU4-obP5RZ09OxvCr1io4KJvEOjDJuuoClF66AT72WymtoMdwzUmhINjR0XSqK6H0MdWsjw7ysyd_JhmqX5CAaT9Pgi0J8lU_pcl215oANqjy7Ob-VMhug9eGyxAWVfu_1u6QJKePlE-w [e] => AQAB ) ) ) apple_public_key_pem = -----BEGIN PUBLIC KEY----- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAlxrwmuYSAsTfn+lUu4go ZSXBD9ackM9OJuwUVQHmbZo6GW4Fu/auUdN5zI7Y1dEDfgt7m7QXWbHuMD01HLnD 4eRtY+RNwCWdjNfEaY/esUPY3OVMrNDI15Ns13xspWS3q+13kdGv9jHI28P87RvM pjz/JCpQ5IM44oSyRnYtVJO+320SB8E2Bw92pmrenbp67KRUzTEVfGU4+obP5RZ0 9OxvCr1io4KJvEOjDJuuoClF66AT72WymtoMdwzUmhINjR0XSqK6H0MdWsjw7ysy d/JhmqX5CAaT9Pgi0J8lU/pcl215oANqjy7Ob+VMhug9eGyxAWVfu/1u6QJKePlE +wIDAQAB -----END PUBLIC KEY----- apple_public_key_alg = RS256
[Lcobucci\JWT]
request data = Array ( [client_id] => YourServiceID [client_secret] => A.B.C1 [code] => c [grant_type] => authorization_code [redirect_uri] => https://YourServiceIDReturnURL ) response = Array ( [access_token] => a [token_type] => Bearer [expires_in] => 3600 [refresh_token] => r [id_token] => id_token )
[Firebase\JWT]
request data = Array ( [client_id] => YourServiceID [client_secret] => A.B.C2 [code] => c [grant_type] => authorization_code [redirect_uri] => https://YourServiceIDReturnURL ) response = Array ( [error] => invalid_client )
[Firebase\JWT and \Lcobucci\JWT\Signer\Ecdsa\MultibyteStringConverter]
request data = Array ( [client_id] => YourServiceID [client_secret] => A.B.C3 [code] => c [grant_type] => authorization_code [redirect_uri] => https://YourServiceIDReturnURL ) response = Array ( [error] => invalid_grant )
[Firebase\JWT without openssl_pkey_get_private and \Lcobucci\JWT\Signer\Ecdsa\MultibyteStringConverter]
request data = Array ( [client_id] => YourServiceID [client_secret] => A.B.C4 [code] => c [grant_type] => authorization_code [redirect_uri] => https://YourServiceIDReturnURL ) response = Array ( [error] => invalid_grant )
而跟 Apple Auth API 溝通的結果，若本身 JWT 製作踩到演算法等問題只會收到 {"error":"invalid_client"}，但這也包含 OAUTH REDIRECT_URI 不合法等等，如果演算法打通了，而 Code 過期或是被重複使用時，會收到 {"error":"invalid_grant"} 資訊。
