(DataFlex) OAuth2 for a GMail using a Service Account Key

Demonstrates how to use GMail with OAuth2 for a Google Service Account. The 1st step is to obtain a temporary access token from the Google OAuth 2.0 Authorization Server. This can be accomplished using Chilkat HTTP.

Once the access token is obtained, it may be used to send email. The access token may be used while it remains valid to send as many emails as desired. Once it expires, a new access token needs to be obtained (using the same procedure).

Note: This is for OAuth2 using Google Service account keys.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoHttp
    Variant vCert
    Handle hoCert
    Boolean iSuccess
    String sIss
    String sScope
    String sOauth_sub
    Integer iNumSec
    String sAccessToken
    Handle hoMailman
    Variant vEmail
    Handle hoEmail
    String sTemp1
    Boolean bTemp1

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // --------------------------------------------------------------------
    // Important:  In most cases, this example is not what you are looking for.
    // This example is for OAuth2 using a Google Service Account Key.
    // 
    // It is more likely that the example you actually need is here:
    // Get GMail SMTP Access Token 
    // --------------------------------------------------------------------

    Get Create (RefClass(cComChilkatHttp)) To hoHttp
    If (Not(IsComObjectCreated(hoHttp))) Begin
        Send CreateComObject of hoHttp
    End

    // When a service account (Client ID) is created at https://code.google.com/apis/console/
    // Google will generate a P12 key.  This is a PKCS12 (PFX) file that you will download
    // and save.  The password to access the contents of this file is "notasecret".
    // NOTE: The Chilkat Pfx API provides the ability to load a PFX/P12 and re-save
    // with a different password.

    // Begin by loading the downloaded .p12 into a Chilkat certificate object:
    Get Create (RefClass(cComChilkatCert)) To hoCert
    If (Not(IsComObjectCreated(hoCert))) Begin
        Send CreateComObject of hoCert
    End
    Get ComLoadPfxFile Of hoCert "/myDir/API Project-1c43a291e2a1-notasecret.p12" "notasecret" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoCert To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // The next (and final) step is to request the access token.  Chilkat internally
    // does all the work of forming the JWT header and JWT claim set, encoding and
    // signing the JWT, and sending the access token request.
    // The application need only provide the inputs: The iss, scope(s), sub, and the
    // desired duration with a max of 3600 seconds (1 hour).
    // 
    // Each of these inputs is defined as follows 
    // (see https://developers.google.com/accounts/docs/OAuth2ServiceAccount
    // iss: The email address of the service account.
    // scope: A space-delimited list of the permissions that the application requests.
    // sub: The email address of the user for which the application is requesting delegated access.
    //       the "sub" may be empty if no delegation exists.
    // numSec: The number of seconds for which the access token will be valid (max 3600).

    Move "761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com" To sIss
    Move "https://mail.google.com/" To sScope
    // The sub should be your Google Apps user email address (not a gmail.com address)
    Move "YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS" To sOauth_sub
    Move 3600 To iNumSec

    Get pvComObject of hoCert to vCert
    Get ComG_SvcOauthAccessToken Of hoHttp sIss sScope sOauth_sub iNumSec vCert To sAccessToken
    Get ComLastMethodSuccess Of hoHttp To bTemp1
    If (bTemp1 <> True) Begin
        Get ComLastErrorText Of hoHttp To sTemp1
        Showln sTemp1
        Procedure_Return
    End
    Else Begin
        Showln "access token: " sAccessToken
    End

    // Now that we have the access token, it may be used to send as many emails as desired
    // while it remains valid.  Once the access token expires, a new access token should be
    // retrieved and used.

    // -----------------------------------------------------------------------
    Get Create (RefClass(cComChilkatMailMan)) To hoMailman
    If (Not(IsComObjectCreated(hoMailman))) Begin
        Send CreateComObject of hoMailman
    End

    // Set the properties for the GMail SMTP server:
    Set ComSmtpHost Of hoMailman To "smtp.gmail.com"
    Set ComSmtpPort Of hoMailman To 587
    Set ComStartTLS Of hoMailman To True

    Set ComSmtpUsername Of hoMailman To "YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS"
    Set ComOAuth2AccessToken Of hoMailman To sAccessToken

    // Create a new email object
    Get Create (RefClass(cComChilkatEmail)) To hoEmail
    If (Not(IsComObjectCreated(hoEmail))) Begin
        Send CreateComObject of hoEmail
    End

    Set ComSubject Of hoEmail To "This is a test"
    Set ComBody Of hoEmail To "This is a test"
    Set ComFrom Of hoEmail To "YOUR NAME <YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS>"
    Get ComAddTo Of hoEmail "Chilkat Admin" "admin@chilkatsoft.com" To iSuccess
    // To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

    // Call SendEmail to connect to the SMTP server and send.
    // The connection (i.e. session) to the SMTP server remains
    // open so that subsequent SendEmail calls may use the
    // same connection.  
    Get pvComObject of hoEmail to vEmail
    Get ComSendEmail Of hoMailman vEmail To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoMailman To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // You may close the connection here.  If the connection is kept open, 
    // the next call to mailman.SendEmail will continue using the already-established connection
    // (and automatically re-connect if needed).
    Get ComCloseSmtpConnection Of hoMailman To iSuccess
    If (iSuccess <> True) Begin
        Showln "Connection to SMTP server not closed cleanly."
    End

    Showln "Email Sent via GMail using an OAuth2 Service Account Key."


End_Procedure