(Perl) Get GMail SMTP OAuth2 Access Token for Desktop App

See more OAuth2 Examples

Note: This example requires Chilkat v10.1.2 or greater.

Chilkat Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux

use chilkat();

# To further clarify, see OAuth 2.0 Authorization Flow

$oauth2 = chilkat::CkOAuth2->new();

# For Google OAuth2, set the listen port equal to the port used
# in the Authorized Redirect URL for the Client ID.
# For example, in this case the Authorized Redirect URL would be http://localhost:55568/
# Your app should choose a port not likely not used by any other application.
$oauth2->put_ListenPort(55568);

$oauth2->put_AuthorizationEndpoint("https://accounts.google.com/o/oauth2/v2/auth");
$oauth2->put_TokenEndpoint("https://www.googleapis.com/oauth2/v4/token");

# Replace these with actual values.
$oauth2->put_ClientId("GOOGLE-CLIENT-ID");
$oauth2->put_ClientSecret("GOOGLE-CLIENT-SECRET");

# To use Gmail's OAuth2 for sending emails via the SMTP protocol, you need to request the https://mail.google.com/ scope. 
# See About GMail SMTP OAuth2 Scopes
$oauth2->put_Scope("https://mail.google.com/");

# Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
$url = $oauth2->startAuth();
if ($oauth2->get_LastMethodSuccess() != 1) {
    print $oauth2->lastErrorText() . "\r\n";
    exit;
}

# Launch the default browser on the system and navigate to the url.
# The LaunchBrowser method was added in Chilkat v10.1.2.
$success = $oauth2->LaunchBrowser($url);
if ($success == 0) {
    print $oauth2->lastErrorText() . "\r\n";
    exit;
}

# Wait for the user to approve or deny authorization in the browser.
$numMsWaited = 0;
while (($numMsWaited < 90000) and ($oauth2->get_AuthFlowState() < 3)) {
    $oauth2->SleepMs(100);
    $numMsWaited = $numMsWaited + 100;
}

# If the browser does not respond within the specified time, AuthFlowState will be:
# 
# 1: Waiting for Redirect – The OAuth2 background thread is waiting for the browser's redirect request.
# 2: Waiting for Final Response – The thread is awaiting the final access token response.
# In either case, cancel the background task initiated by StartAuth.

if ($oauth2->get_AuthFlowState() < 3) {
    $oauth2->Cancel();
    print "No response from the browser!" . "\r\n";
    exit;
}

# Check AuthFlowState to determine if authorization was granted, denied, or failed:
# 
# 3: Success – OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
# 4: Access Denied – OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
# 5: Failure – OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

if ($oauth2->get_AuthFlowState() == 5) {
    print "OAuth2 failed to complete." . "\r\n";
    print $oauth2->failureInfo() . "\r\n";
    exit;
}

if ($oauth2->get_AuthFlowState() == 4) {
    print "OAuth2 authorization was denied." . "\r\n";
    print $oauth2->accessTokenResponse() . "\r\n";
    exit;
}

if ($oauth2->get_AuthFlowState() != 3) {
    print "Unexpected AuthFlowState:" . $oauth2->get_AuthFlowState() . "\r\n";
    exit;
}

# Save the full JSON access token response to a file.
$sbJson = chilkat::CkStringBuilder->new();
$sbJson->Append($oauth2->accessTokenResponse());
$sbJson->WriteFile("qa_data/tokens/_gmailSmtp.json","utf-8",0);

# The saved JSON response looks like this:

# 	{
# 	 "access_token": "ya39.Ci-XA_C5bGgRDC3UaD-h0_NeL-DVIQnI2gHtBBBHkZzrwlARkwX6R3O0PCDEzRlfaQ",
# 	 "token_type": "Bearer",
# 	 "expires_in": 3600,
# 	 "refresh_token": "1/r_2c_7jddspcdfesrrfKqfXtqo08D6Q-gUU0DsdfVMsx0c"
# 	}
# 
print "OAuth2 authorization granted!" . "\r\n";
print "Access Token = " . $oauth2->accessToken() . "\r\n";