(Ruby) Verify a JWT Created by the Amazon Cognito Service

Demonstrates how to verify a JWT created by the Amazon Cognito Service.

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.

# The public keys for this example are at https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json
# Let's get them:

http = Chilkat::CkHttp.new()
sbJsonKeys = Chilkat::CkStringBuilder.new()
success = http.QuickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json",sbJsonKeys)
if (success == false)
    print http.lastErrorText() + "\n";
    exit
end

jsonKeys = Chilkat::CkJsonObject.new()
jsonKeys.LoadSb(sbJsonKeys)
jsonKeys.put_EmitCompact(false)
print jsonKeys.emit() + "\n";

# Here are the keys:

# {
#   "keys": [
#     {
#       "alg": "RS256",
#       "e": "AQAB",
#       "kid": "1A/L5Fsb2EsEwxy5E0cmCMS1BnMe6Jl6NXiMig4iNwU=",
#       "kty": "RSA",
#       "n": "y0w7BJrIJYi ... jKG27z2P3OKw",
#       "use": "sig"
#     },
#     {
#       "alg": "RS256",
#       "e": "AQAB",
#       "kid": "mos6VTJnvDwurY3ghJg6IAPUq+dMwl6CL/iThzJOkzg=",
#       "kty": "RSA",
#       "n": "qbIEH-7tg6yrT ... 3Fj94ooTd0w",
#       "use": "sig"
#     }
#   ]
# }

# Try the 1st key.
# jsonKey1 is a CkJsonObject
jsonKey1 = jsonKeys.ObjectOf("keys[0]")
if (jsonKeys.get_LastMethodSuccess() == false)
    print "Did not get the 1st JSON public key." + "\n";
    exit
end

pubKey1 = Chilkat::CkPublicKey.new()
success = pubKey1.LoadFromString(jsonKey1.emit())
if (success == false)
    print pubKey1.lastErrorText() + "\n";
    exit
end

print "Success" + "\n";

jwt = Chilkat::CkJwt.new()

# I did not include the an actual AWS Cognito token here because our test sample used customer-provided data..
token = "eyJ..asXg"

# First verify the signature.
sigVerified = jwt.VerifyJwtPk(token,pubKey1)
print "verified: " + sigVerified.to_s() + "\n";

# Let's see if the time constraints, if any, are valid.
# The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
# If the current system time is before the "nbf" time, or after the "exp" time,
# then IsTimeValid will return false/0.
# Also, we'll allow a leeway of 60 seconds to account for any clock skew.
# Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
leeway = 60
bTimeValid = jwt.IsTimeValid(token,leeway)
print "time constraints valid: " + bTimeValid.to_s() + "\n";

# Now let's recover the original claims JSON (the payload).
payload = jwt.getPayload(token)
# The payload will likely be in compact form:
print payload + "\n";

# We can format for human viewing by loading it into Chilkat's JSON object
# and emit.
json = Chilkat::CkJsonObject.new()
success = json.Load(payload)
json.put_EmitCompact(false)
print json.emit() + "\n";

# We can recover the original JOSE header in the same way:
joseHeader = jwt.getHeader(token)
# The payload will likely be in compact form:
print joseHeader + "\n";

# We can format for human viewing by loading it into Chilkat's JSON object
# and emit.
success = json.Load(joseHeader)
json.put_EmitCompact(false)
print json.emit() + "\n";