Tcl Requires Chilkat v11.0.0+

Verify a JWT Created by the Amazon Cognito Service

See more JSON Web Token (JWT) Examples

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

load ./chilkat.dll

set success 0

#  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:

set http [new_CkHttp]

set sbJsonKeys [new_CkStringBuilder]

set success [CkHttp_QuickGetSb $http "https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json" $sbJsonKeys]
if {$success == 0} then {
    puts [CkHttp_lastErrorText $http]
    delete_CkHttp $http
    delete_CkStringBuilder $sbJsonKeys
    exit
}

set jsonKeys [new_CkJsonObject]

CkJsonObject_LoadSb $jsonKeys $sbJsonKeys
CkJsonObject_put_EmitCompact $jsonKeys 0
puts [CkJsonObject_emit $jsonKeys]

#  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.
set jsonKey1 [new_CkJsonObject]

CkJsonObject_ObjectOf2 $jsonKeys "keys[0]" $jsonKey1

set pubKey1 [new_CkPublicKey]

set success [CkPublicKey_LoadFromString $pubKey1 [CkJsonObject_emit $jsonKey1]]
if {$success == 0} then {
    puts [CkPublicKey_lastErrorText $pubKey1]
    delete_CkHttp $http
    delete_CkStringBuilder $sbJsonKeys
    delete_CkJsonObject $jsonKeys
    delete_CkJsonObject $jsonKey1
    delete_CkPublicKey $pubKey1
    exit
}

puts "Success"

set jwt [new_CkJwt]

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

#  First verify the signature.
set sigVerified [CkJwt_VerifyJwtPk $jwt $token $pubKey1]
puts "verified: $sigVerified"

#  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.
set leeway 60
set bTimeValid [CkJwt_IsTimeValid $jwt $token $leeway]
puts "time constraints valid: $bTimeValid"

#  Now let's recover the original claims JSON (the payload).
set payload [CkJwt_getPayload $jwt $token]
#  The payload will likely be in compact form:
puts "$payload"

#  We can format for human viewing by loading it into Chilkat's JSON object
#  and emit.
set json [new_CkJsonObject]

set success [CkJsonObject_Load $json $payload]
CkJsonObject_put_EmitCompact $json 0
puts [CkJsonObject_emit $json]

#  We can recover the original JOSE header in the same way:
set joseHeader [CkJwt_getHeader $jwt $token]
#  The payload will likely be in compact form:
puts "$joseHeader"

#  We can format for human viewing by loading it into Chilkat's JSON object
#  and emit.
set success [CkJsonObject_Load $json $joseHeader]
CkJsonObject_put_EmitCompact $json 0
puts [CkJsonObject_emit $json]

delete_CkHttp $http
delete_CkStringBuilder $sbJsonKeys
delete_CkJsonObject $jsonKeys
delete_CkJsonObject $jsonKey1
delete_CkPublicKey $pubKey1
delete_CkJwt $jwt
delete_CkJsonObject $json