(Ruby) 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 Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# 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 = Chilkat::CkFileAccess.new()
jsonKey = fac.readEntireTextFile("qa_data/firebase/firebase-chilkat-firebase-adminsdk-n28n4-1b664ee163.json","utf-8")
if (fac.get_LastMethodSuccess() != true)
    print fac.lastErrorText() + "\n";
    exit
end

# 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 = Chilkat::CkAuthGoogle.new()
gAuth.put_JsonKey(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"

gAuth.put_Scope("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.
gAuth.put_ExpireNumSeconds(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.)
gAuth.put_SubEmailAddress("")

# 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 = 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:
print "Firebase Access Token: " + gAuth.accessToken() + "\n";

# Save the token to a file (or wherever desired).  This token is valid for 1 hour.
fac.WriteEntireTextFile("qa_data/tokens/firebaseToken.txt",gAuth.accessToken(),"utf-8",false)