Ruby

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. Ruby

require 'chilkat'

success = false

# 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.
fac = Chilkat::CkFileAccess.new()
jsonKey = fac.readEntireTextFile("qa_data/googleApi/chilkat25-b4214220e565.json","utf-8")
if (fac.get_LastMethodSuccess() != true)
    print fac.lastErrorText() + "\n";
    exit
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"
# }

gAuth = Chilkat::CkAuthGoogle.new()
gAuth.put_JsonKey(jsonKey)

# Specify a scope.
gAuth.put_Scope("https://mail.google.com/")

# Request an access token that is valid for this many seconds.
gAuth.put_ExpireNumSeconds(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.
gAuth.put_SubEmailAddress("info@chilkat.xyz")

# Connect to www.googleapis.com using TLS
tlsSock = Chilkat::CkSocket.new()
success = tlsSock.Connect("www.googleapis.com",443,true,5000)
if (success != true)
    print tlsSock.lastErrorText() + "\n";
    exit
end

# Send the request to obtain the access token.
success = gAuth.ObtainAccessToken(tlsSock)
if (success != true)
    print gAuth.lastErrorText() + "\n";
    exit
end

# Examine the access token:
accessToken = gAuth.accessToken()
print "Access Token: " + accessToken + "\n";

# 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.

# -----------------------------------------------------------------------
mailman = Chilkat::CkMailMan.new()

# Set the properties for the GMail SMTP server:
mailman.put_SmtpHost("smtp.gmail.com")
mailman.put_SmtpPort(587)
mailman.put_StartTLS(true)

mailman.put_SmtpUsername("info@chilkat.xyz")
mailman.put_OAuth2AccessToken(accessToken)

# Create a new email object
email = Chilkat::CkEmail.new()

email.put_Subject("This is a test")
email.put_Body("This is a test")
email.put_From("Chilkat Test <info@chilkat.xyz>")
success = email.AddTo("Chilkat Software","info@chilkatsoft.com")
# To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

success = mailman.SendEmail(email)
if (success != true)
    print mailman.lastErrorText() + "\n";
    exit
end

success = mailman.CloseSmtpConnection()
if (success != true)
    print "Connection to SMTP server not closed cleanly." + "\n";
end

print "Successfully sent email using Gmail with a service account key." + "\n";