(Tcl) OAuth2 for a GMail using a JSON Service Account Key

Demonstrates how get an OAuth2 access token for GMail (Google Service Account) using a JSON private key.

After the access token is obtained, it may be used to send email. When the access token expires, a new access token needs to be obtained (using this same procedure).

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

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load ./chilkat.dll

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

# First load the JSON key into a string.
set fac [new_CkFileAccess]

set jsonKey [CkFileAccess_readEntireTextFile $fac "qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json" "utf-8"]
if {[CkFileAccess_get_LastMethodSuccess $fac] != 1} then {
    puts [CkFileAccess_lastErrorText $fac]
    delete_CkFileAccess $fac
    exit
}

# A JSON private key should look like this:

# 	{
# 	  "type": "service_account",
# 	  "project_id": "chilkattest-1350",
# 	  "private_key_id": "fa2e36ee26986eab628b59868af8bec1d1c64c38",
# 	  "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvgIjFa...28N64N2n1E4FYzBZjSdy\n-----END PRIVATE KEY-----\n",
# 	  "client_email": "598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a@developer.gserviceaccount.com",
# 	  "client_id": "598922945226-00rb0ppfg0snd9jo7bhvd4v17jtj2d3a.apps.googleusercontent.com",
# 	  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
# 	  "token_uri": "https://accounts.google.com/o/oauth2/token",
# 	  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
# 	  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a%40developer.gserviceaccount.com"
# 	}

set gAuth [new_CkAuthGoogle]

CkAuthGoogle_put_JsonKey $gAuth $jsonKey

# Choose a scope.
CkAuthGoogle_put_Scope $gAuth "https://mail.google.com/"

# Request an access token that is valid for this many seconds.
CkAuthGoogle_put_ExpireNumSeconds $gAuth 3600

# If the application is requesting delegated access:
# The email address of the user for which the application is requesting delegated access,
# then set the email address here. (Otherwise leave it empty.)
CkAuthGoogle_put_SubEmailAddress $gAuth ""

# Connect to www.googleapis.com using TLS (TLS 1.2 is the default.)
# The Chilkat socket object is used so that the connection can be established
# through proxies or an SSH tunnel if desired.
set tlsSock [new_CkSocket]

set success [CkSocket_Connect $tlsSock "www.googleapis.com" 443 1 5000]
if {$success != 1} then {
    puts [CkSocket_lastErrorText $tlsSock]
    delete_CkFileAccess $fac
    delete_CkAuthGoogle $gAuth
    delete_CkSocket $tlsSock
    exit
}

# Send the request to obtain the access token.
set success [CkAuthGoogle_ObtainAccessToken $gAuth $tlsSock]
if {$success != 1} then {
    puts [CkAuthGoogle_lastErrorText $gAuth]
    delete_CkFileAccess $fac
    delete_CkAuthGoogle $gAuth
    delete_CkSocket $tlsSock
    exit
}

# Examine the access token:
puts "Access Token: [CkAuthGoogle_accessToken $gAuth]"

# Now that we have the access token, it may be used to send email
# while it remains valid.  Once the access token expires, a new access token 
# should be obtained using the same code as above.

# -----------------------------------------------------------------------
set mailman [new_CkMailMan]

# Set the properties for the GMail SMTP server:
CkMailMan_put_SmtpHost $mailman "smtp.gmail.com"
CkMailMan_put_SmtpPort $mailman 587
CkMailMan_put_StartTLS $mailman 1

CkMailMan_put_SmtpUsername $mailman "YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS"
CkMailMan_put_OAuth2AccessToken $mailman [CkAuthGoogle_accessToken $gAuth]

# Create a new email object
set email [new_CkEmail]

CkEmail_put_Subject $email "This is a test"
CkEmail_put_Body $email "This is a test"
CkEmail_put_From $email "YOUR NAME <YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS>"
set success [CkEmail_AddTo $email "Chilkat Admin" "admin@chilkatsoft.com"]
# 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.  
set success [CkMailMan_SendEmail $mailman $email]
if {$success != 1} then {
    puts [CkMailMan_lastErrorText $mailman]
    delete_CkFileAccess $fac
    delete_CkAuthGoogle $gAuth
    delete_CkSocket $tlsSock
    delete_CkMailMan $mailman
    delete_CkEmail $email
    exit
}

# 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).
set success [CkMailMan_CloseSmtpConnection $mailman]
if {$success != 1} then {
    puts "Connection to SMTP server not closed cleanly."
}

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

delete_CkFileAccess $fac
delete_CkAuthGoogle $gAuth
delete_CkSocket $tlsSock
delete_CkMailMan $mailman
delete_CkEmail $email