(PureBasic) Get Firebase Access Token from JSON Service Account Private Key

Demonstrates how to get a Firebase access token using a JSON service account private key. Your Firebase service account can be used to authenticate multiple Firebase features, such as Database, Storage and Auth, programmatically.

A Firebase JSON service account private key can be created in the Firebase settings/admin portion of the console.firebase.google.com site as shown here:

Scroll down to see the example code...

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkSocket.pb"
IncludeFile "CkAuthGoogle.pb"
IncludeFile "CkFileAccess.pb"

Procedure ChilkatExample()

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

    ; First load the Firebase JSON private key into a string.
    fac.i = CkFileAccess::ckCreate()
    If fac.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    jsonKey.s = CkFileAccess::ckReadEntireTextFile(fac,"qa_data/firebase/firebase-chilkat-firebase-adminsdk-n28n4-1b664ee163.json","utf-8")
    If CkFileAccess::ckLastMethodSuccess(fac) <> 1
        Debug CkFileAccess::ckLastErrorText(fac)
        CkFileAccess::ckDispose(fac)
        ProcedureReturn
    EndIf

    ; A Firebase JSON private key should look something like this:

    ; { 
    ;   "type": "service_account",
    ;   "project_id": "firebase-chilkat",
    ;   "private_key_id": "1c664ee164907413c91ddefcf5b765ecba8779e2",
    ;   "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvQIBA ... Ya2UZii/lXn73/ZOK8=\n-----END PRIVATE KEY-----\n",
    ;   "client_email": "firebase-adminsdk-n28n4@firebase-chilkat.iam.gserviceaccount.com",
    ;   "client_id": "134846322329335418431",
    ;   "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/firebase-adminsdk-n28n4%40firebase-chilkat.iam.gserviceaccount.com"
    ; } 
    ; 

    gAuth.i = CkAuthGoogle::ckCreate()
    If gAuth.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkAuthGoogle::setCkJsonKey(gAuth, jsonKey)

    ; Choose a scope.
    ; The scope could be "https://www.googleapis.com/auth/firebase.database"
    ; or a space-delimited list of scopes:
    ; "https://www.googleapis.com/auth/firebase.database https://www.googleapis.com/auth/userinfo.email"

    CkAuthGoogle::setCkScope(gAuth, "https://www.googleapis.com/auth/firebase.database https://www.googleapis.com/auth/userinfo.email")

    ; Request an access token that is valid for this many seconds.
    CkAuthGoogle::setCkExpireNumSeconds(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::setCkSubEmailAddress(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.
    tlsSock.i = CkSocket::ckCreate()
    If tlsSock.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkSocket::ckConnect(tlsSock,"www.googleapis.com",443,1,5000)
    If success <> 1
        Debug CkSocket::ckLastErrorText(tlsSock)
        CkFileAccess::ckDispose(fac)
        CkAuthGoogle::ckDispose(gAuth)
        CkSocket::ckDispose(tlsSock)
        ProcedureReturn
    EndIf

    ; Send the request to obtain the access token.
    success = CkAuthGoogle::ckObtainAccessToken(gAuth,tlsSock)
    If success <> 1
        Debug CkAuthGoogle::ckLastErrorText(gAuth)
        CkFileAccess::ckDispose(fac)
        CkAuthGoogle::ckDispose(gAuth)
        CkSocket::ckDispose(tlsSock)
        ProcedureReturn
    EndIf

    ; Examine the access token:
    Debug "Firebase Access Token: " + CkAuthGoogle::ckAccessToken(gAuth)

    ; Save the token to a file (or wherever desired).  This token is valid for 1 hour.
    CkFileAccess::ckWriteEntireTextFile(fac,"qa_data/tokens/firebaseToken.txt",CkAuthGoogle::ckAccessToken(gAuth),"utf-8",0)


    CkFileAccess::ckDispose(fac)
    CkAuthGoogle::ckDispose(gAuth)
    CkSocket::ckDispose(tlsSock)


    ProcedureReturn
EndProcedure