(Tcl) POP3 Auto-Refresh Office365 Access Token

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Demonstrates how to automatically recover from an expired OAuth2 access token when OAuth2 authentication fails in the POP3 protocol. If the server responds with "-ERR Authentication failure: unknown user name or bad password.", then we refresh the access token and retry.

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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.

set mailman [new_CkMailMan]

CkMailMan_put_MailHost $mailman "outlook.office365.com"
CkMailMan_put_MailPort $mailman 995
CkMailMan_put_PopSsl $mailman 1

# Use your O365 email address here.
CkMailMan_put_PopUsername $mailman "OFFICE365_EMAIL_ADDRESS"

# When using OAuth2 authentication, leave the password empty.
CkMailMan_put_PopPassword $mailman ""

# Load our previously obtained OAuth2 access token.
set jsonToken [new_CkJsonObject]

set success [CkJsonObject_LoadFile $jsonToken "qa_data/tokens/office365.json"]
if {$success == 0} then {
    puts [CkJsonObject_lastErrorText $jsonToken]
    delete_CkMailMan $mailman
    delete_CkJsonObject $jsonToken
    exit
}

CkMailMan_put_OAuth2AccessToken $mailman [CkJsonObject_stringOf $jsonToken "access_token"]

# Make the TLS connection to the outlook.office365.com POP3 server.
set success [CkMailMan_Pop3Connect $mailman]
if {$success != 1} then {
    puts [CkMailMan_lastErrorText $mailman]
    delete_CkMailMan $mailman
    delete_CkJsonObject $jsonToken
    exit
}

# Authenticate using XOAUTH2
set success [CkMailMan_Pop3Authenticate $mailman]
if {$success != 1} then {
    # If we're still connected to the mail server, then it means the server sent a non-success response,
    # Such as:  -ERR Authentication failure: unknown user name or bad password.
    if {[CkMailMan_get_IsPop3Connected $mailman] == 1} then {

        # Refresh the OAuth2 access token, and if successful, save the new (refreshed) access token and try authenticating again.
        set oauth2 [new_CkOAuth2]

        # Use your actual Directory (tenant) ID instead of "112d7ed6-71bf-4eba-a866-738364321bfc"
        CkOAuth2_put_TokenEndpoint $oauth2 "https://login.microsoftonline.com/112d7ed6-71bf-4eba-a866-738364321bfc/oauth2/v2.0/token"

        # Replace these with your Azure App Registration's actual values.
        CkOAuth2_put_ClientId $oauth2 "CLIENT_ID"
        CkOAuth2_put_ClientSecret $oauth2 "CLIENT_SECRET"

        # Get the "refresh_token"
        CkOAuth2_put_RefreshToken $oauth2 [CkJsonObject_stringOf $jsonToken "refresh_token"]

        # Send the HTTP POST to refresh the access token..
        set success [CkOAuth2_RefreshAccessToken $oauth2]
        if {$success != 1} then {
            puts [CkOAuth2_lastErrorText $oauth2]
            delete_CkMailMan $mailman
            delete_CkJsonObject $jsonToken
            delete_CkOAuth2 $oauth2
            exit
        }

        puts "New access token: [CkOAuth2_accessToken $oauth2]"
        puts "New refresh token: [CkOAuth2_refreshToken $oauth2]"

        # Update the JSON with the new tokens.
        CkJsonObject_UpdateString $jsonToken "access_token" [CkOAuth2_accessToken $oauth2]
        CkJsonObject_UpdateString $jsonToken "refresh_token" [CkOAuth2_refreshToken $oauth2]

        # Save the new JSON access token response to a file.
        set sbJson [new_CkStringBuilder]

        CkJsonObject_put_EmitCompact $jsonToken 0
        CkJsonObject_EmitSb $jsonToken $sbJson
        CkStringBuilder_WriteFile $sbJson "qa_data/tokens/office365.json" "utf-8" 0

        puts "New Access Token = [CkOAuth2_accessToken $oauth2]"

        # Update the mailman with the new access token.
        CkMailMan_put_OAuth2AccessToken $mailman [CkOAuth2_accessToken $oauth2]

        # Retry the authentication.
        set success [CkMailMan_Pop3Authenticate $mailman]
        if {$success == 0} then {
            puts [CkMailMan_lastErrorText $mailman]
            delete_CkMailMan $mailman
            delete_CkJsonObject $jsonToken
            delete_CkOAuth2 $oauth2
            delete_CkStringBuilder $sbJson
            exit
        }

    }     else {
        puts [CkMailMan_lastErrorText $mailman]
        delete_CkMailMan $mailman
        delete_CkJsonObject $jsonToken
        delete_CkOAuth2 $oauth2
        delete_CkStringBuilder $sbJson
        exit
    }

}

# Find out how many emails are on the server..
set numEmails [CkMailMan_CheckMail $mailman]
if {$numEmails < 0} then {
    puts [CkMailMan_lastErrorText $mailman]
    delete_CkMailMan $mailman
    delete_CkJsonObject $jsonToken
    delete_CkOAuth2 $oauth2
    delete_CkStringBuilder $sbJson
    exit
}

# Examine the POP3 session log:
puts [CkMailMan_pop3SessionLog $mailman]

# The POP3 session log will look something like this:

# **** Connected to outlook.office365.com:995
# < +OK The Microsoft Exchange POP3 service is ready. [QwBIADIAUABSADEANgBDAEEAMAAwADEAMgAuAG4AYQBtAHAAcgBkADEANgAuAHAAcgBvAGQALgBvAHUAdABsAG8AbwBrAC4AYwBvAG0A]
# > AUTH XOAUTH2
# < + 
# > <base64 string in XOAUTH2 format>
# < -ERR Authentication failure: unknown user name or bad password.
# > AUTH XOAUTH2
# < + 
# > <base64 string in XOAUTH2 format>
# < +OK User successfully authenticated.
# > STAT
# < +OK 248 46637086

# End the POP3 session and close the connection to the GMail server.
set success [CkMailMan_Pop3EndSession $mailman]
if {$success != 1} then {
    puts [CkMailMan_lastErrorText $mailman]
    delete_CkMailMan $mailman
    delete_CkJsonObject $jsonToken
    delete_CkOAuth2 $oauth2
    delete_CkStringBuilder $sbJson
    exit
}

puts "Finished."

delete_CkMailMan $mailman
delete_CkJsonObject $jsonToken
delete_CkOAuth2 $oauth2
delete_CkStringBuilder $sbJson