如何通过 libEtPan 对 GMail 使用 OAuth 访问？

Question

有没有人有关于如何使用 libEtPan 通过 OAuth 连接到 GMail 帐户的示例代码或明确说明？我找不到任何东西。

GMail 中 OAuth 的详细信息在这里：http://code.google.com/apis/gmail/oauth/

Answer 1

libetpan 在其头文件中有一些文档，对于 IMAP，它在 https://github.com/dinhviethoa/libetpan/blob/master/src/low-level/imap/mailimap_oauth2.h 中

/*
   mailimap_oauth2_authenticate()
   Authenticates the client using using an oauth2 token.
   To gather a deeper understanding of the OAuth2 aunthentication
   process refer to: https://developers.google.com/gmail/xoauth2_protocol
   For a quick start you may follow this brief set of steps:
   1. Set up a profile for your app in the Google 
      API Console: https://code.google.com/apis/console
   2. With your recently obtained client_id and secret 
      load the following URL (everything goes ina single line):
      https://accounts.google.com/o/oauth2/auth?client_id=[YOUR_CLIENT_ID]&
          redirect_uri=urn%3Aietf%3Awg%3Aoauth%3A2.0%3Aoob&
          response_type=code&scope=https%3A%2F%2Fmail.google.com%2F%20email&
          &access_type=offline
   3. The user most follow instructions to authorize application access
      to Gmail.
   4. After the user hits the "Accept" button it will be redirected to another
      page where the access token will be issued.
   5. Now from the app we need and authorization token, to get one we issue a POST request
      the following URL: https://accounts.google.com/o/oauth2/token using these parameters:
      client_id: This is the client id we got from step 1
      client_secret: Client secret as we got it from step 1
      code: This is the code we received in step 4
      redirect_uri: This is a redirect URI where the access token will be sent, for non 
       web applications this is usually urn:ietf:wg:oauth:2.0:oob (as we got from step 1)
      grant_type: Always use the authorization_code parameter to retrieve an access and refresh tokens
   6. After step 5 completes we receive a JSON object similar to:
       {
         "access_token":"1/fFAGRNJru1FTz70BzhT3Zg",
         "refresh_token":"1/fFAGRNJrufoiWEGIWEFJFJF",
         "expires_in":3920,
         "token_type":"Bearer"
       }
      The above output gives us the access_token, now we need to also retrieve the user's e-mail, 
      to do that we need to perform an HTTP GET request to Google's UserInfo API using this URL:
       https://www.googleapis.com/oauth2/v1/userinfo?access_token=[YOUR_ACCESS_TOKEN]
      this will return the following JSON output:
       {
        "id": "00000000000002222220000000",
        "email": "email@example.com",
        "verified_email": true
       }
   @param session       IMAP session
   @param auth_user     Authentication user (tipically an e-mail address, depends on server)
   @param access_token  OAuth2 access token
   @return the return code is one of MAILIMAP_ERROR_XXX or
   MAILIMAP_NO_ERROR codes
  */

LIBETPAN_EXPORT
int mailimap_oauth2_authenticate(mailimap * session, const char * auth_user,
    const char * access_token);

LIBETPAN_EXPORT
int mailimap_has_xoauth2(mailimap * session);

我自己还没有尝试过，但是当我开始实施它时，我会发布一个实施链接。

2021 年 3 月更新

我现在终于开始在我的电子邮件客户端 nmail 中实现对 Google OAuth 2.0 的支持。提交可以查看here，但基本上我最终在一个单独的外部脚本中执行了上面的步骤 2-6，因为 libetpan 不会为我们生成令牌/刷新。令牌处理相当简单——例如参见oauth2nmail.py。