(SQL Server) OAuth2 for 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 in IMAP XOAUTH2 authentication. 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

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- 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 IMAP OAuth2 Access Token 
    -- --------------------------------------------------------------------

    -- 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:
    DECLARE @cert int
    -- Use "Chilkat_9_5_0.Cert" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Cert', @cert OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    DECLARE @success int
    EXEC sp_OAMethod @cert, 'LoadPfxFile', @success OUT, '/myDir/API Project-1c43a291e2a1-notasecret.p12', 'notasecret'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @cert, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @cert
        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 there is no delegation. (This is typical.)
    -- numSec: The number of seconds for which the access token will be valid (max 3600).

    DECLARE @iss nvarchar(4000)
    SELECT @iss = '761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com'
    DECLARE @scope nvarchar(4000)
    SELECT @scope = 'https://mail.google.com/'
    DECLARE @sub nvarchar(4000)
    SELECT @sub = ''
    DECLARE @numSec int
    SELECT @numSec = 3600

    DECLARE @http int
    -- Use "Chilkat_9_5_0.Http" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Http', @http OUT

    DECLARE @accessToken nvarchar(4000)
    EXEC sp_OAMethod @http, 'G_SvcOauthAccessToken', @accessToken OUT, @iss, @scope, @sub, @numSec, @cert
    EXEC sp_OAGetProperty @http, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 <> 1
      BEGIN
        EXEC sp_OAGetProperty @http, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @cert
        EXEC @hr = sp_OADestroy @http
        RETURN
      END
    ELSE
      BEGIN

        PRINT 'access token: ' + @accessToken
      END

    -- Now that we have the access token, it may be used to authenticate via XOAUTH2 with GMail:

    DECLARE @imap int
    -- Use "Chilkat_9_5_0.Imap" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Imap', @imap OUT

    -- GMail's IMAP service uses SSL and port 993.
    EXEC sp_OASetProperty @imap, 'Ssl', 1
    EXEC sp_OASetProperty @imap, 'Port', 993

    -- Connect to the GMail IMAP server.
    EXEC sp_OAMethod @imap, 'Connect', @success OUT, 'imap.gmail.com'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @imap, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @cert
        EXEC @hr = sp_OADestroy @http
        EXEC @hr = sp_OADestroy @imap
        RETURN
      END

    -- Indicate that XOAUTH2 authentication is to be used:
    EXEC sp_OASetProperty @imap, 'AuthMethod', 'XOAUTH2'

    -- Login
    -- The username must be the email address used for the "sub" argument when getting
    -- the access token.  Instead of using a password, pass the access token in the 2nd argument:
    EXEC sp_OAMethod @imap, 'Login', @success OUT, 'user@your-domain.com', @accessToken
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @imap, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
      END
    ELSE
      BEGIN

        PRINT 'Successfully authenticate with GMail IMAP using XOAUTH2!'
      END

    EXEC @hr = sp_OADestroy @cert
    EXEC @hr = sp_OADestroy @http
    EXEC @hr = sp_OADestroy @imap


END
GO