DataFlex

OAuth2 for a GMail using a JSON Service Account Key

See more GMail SMTP/IMAP/POP Examples

This example shows how to obtain an OAuth2 access token for Gmail using a Google Service Account and a JSON private key. Once acquired, the access token can be used to send emails. Remember, upon token expiration, this process needs to be repeated to obtain a new token. Note: This procedure is specific to OAuth2 with Google Service Account keys. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoFac
    String sJsonKey
    Handle hoGAuth
    Variant vTlsSock
    Handle hoTlsSock
    String sAccessToken
    Handle hoMailman
    Variant vEmail
    Handle hoEmail
    String sTemp1
    Boolean bTemp1

    Move False To iSuccess

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

    // --------------------------------------------------------------------------------
    // For a step-by-step guide for setting up your Google Workspace service account,
    // see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
    // --------------------------------------------------------------------------------

    // First load the JSON key into a string.
    Get Create (RefClass(cComCkFileAccess)) To hoFac
    If (Not(IsComObjectCreated(hoFac))) Begin
        Send CreateComObject of hoFac
    End
    Get ComReadEntireTextFile Of hoFac "qa_data/googleApi/chilkat25-b4214220e565.json" "utf-8" To sJsonKey
    Get ComLastMethodSuccess Of hoFac To bTemp1
    If (bTemp1 <> True) Begin
        Get ComLastErrorText Of hoFac To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // A Google service account JSON private key looks like this:

    // {
    //   "type": "service_account",
    //   "project_id": "chilkat25",
    //   "private_key_id": "b4214220f565881e19eeb97c2699bf5a0d1e3e0b",
    //   "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvQ...NXcM=\n-----END PRIVATE KEY-----\n",
    //   "client_email": "chilkatsvc@chilkat25.iam.gserviceaccount.com",
    //   "client_id": "109122032928932715958",
    //   "auth_uri": "https://accounts.google.com/o/oauth2/auth",
    //   "token_uri": "https://oauth2.googleapis.com/token",
    //   "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
    //   "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/chilkatsvc%40chilkat25.iam.gserviceaccount.com",
    //   "universe_domain": "googleapis.com"
    // }

    Get Create (RefClass(cComChilkatAuthGoogle)) To hoGAuth
    If (Not(IsComObjectCreated(hoGAuth))) Begin
        Send CreateComObject of hoGAuth
    End
    Set ComJsonKey Of hoGAuth To sJsonKey

    // Specify a scope.
    Set ComScope Of hoGAuth To "https://mail.google.com/"

    // Request an access token that is valid for this many seconds.
    Set ComExpireNumSeconds Of hoGAuth To 3600

    // When using a Google Workspace account with Gmail APIs, a service account can impersonate a user 
    // via a process called domain-wide delegation � and the "sub" claim in the JWT is what enables this.
    // Domain-wide delegation allows a Google Workspace administrator to authorize a service account to 
    // act on behalf of any user in the domain, without user interaction.

    // This is required for server-to-server access to user data � such as reading/sending Gmail from a background service.
    // This is your company email address.
    Set ComSubEmailAddress Of hoGAuth To "info@chilkat.xyz"

    // Connect to www.googleapis.com using TLS
    Get Create (RefClass(cComChilkatSocket)) To hoTlsSock
    If (Not(IsComObjectCreated(hoTlsSock))) Begin
        Send CreateComObject of hoTlsSock
    End
    Get ComConnect Of hoTlsSock "www.googleapis.com" 443 True 5000 To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoTlsSock To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Send the request to obtain the access token.
    Get pvComObject of hoTlsSock to vTlsSock
    Get ComObtainAccessToken Of hoGAuth vTlsSock To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoGAuth To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Examine the access token:
    Get ComAccessToken Of hoGAuth To sAccessToken
    Showln "Access Token: " sAccessToken

    // Sample output:
    // ya29.a0AW4XtxjGTD67Z8 .... IRw0218

    // The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.

    // -----------------------------------------------------------------------
    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 "info@chilkat.xyz"
    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 "Chilkat Test <info@chilkat.xyz>"
    Get ComAddTo Of hoEmail "Chilkat Software" "info@chilkatsoft.com" To iSuccess
    // To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

    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

    Get ComCloseSmtpConnection Of hoMailman To iSuccess
    If (iSuccess <> True) Begin
        Showln "Connection to SMTP server not closed cleanly."
    End

    Showln "Successfully sent email using Gmail with a service account key."


End_Procedure