How to use OAuth access for GMail with libEtPan?

Does anyone have 开发者_开发百科sample code or clear instructions on how to use libEtPan to connect to a GMail account using OAuth? I couldn't find anything.

Details for OAuth in GMail are here: http://code.google.com/apis/gmail/oauth/

libetpan has some documentation in its header files, for IMAP it's in https://github.com/dinhviethoa/libetpan/blob/master/src/low-level/imap/mailimap_oauth2.h

/*
   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);

I haven't tried it out myself yet, but when I get around to implement it I'll post a link of the implementation.

Update March 2021

I finally got around to implement support for Google OAuth 2.0 in my email client nmail now. The commit can be viewed here but essentially I ended up doing steps 2-6 above in a separate external script, as libetpan does not do the token generation/refresh for us. The token handling is fairly straight-forward - see oauth2nmail.py for example.