(Tcl) Create JWS Using Private Key on a Smart Card

See more JSON Web Signatures (JWS) Examples

Creates and validates a JSON Web Signature (JWS) using the private key associated with a certificate on a smart card.

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load ./chilkat.dll

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

# Load the certificate from a smart card.
set cert [new_CkCert]

set success [CkCert_LoadFromSmartcard $cert ""]
if {$success == 0} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkCert $cert
    exit
}

# Note: Chilkat provides many different ways to load a certificate from a smartcard or USB token,
# such as selecting a certificate if the card contains multiple certificates with private keys,
# or working with lower-level PKCS11 or ScMinidriver API's (both of which Chilkat provides).

# If the associated private key was present on the smartcard, then you can simply
# get it from the Chilkat cert object:
# privKey is a CkPrivateKey
set privKey [CkCert_ExportPrivateKey $cert]
if {[CkCert_get_LastMethodSuccess $cert] == 0} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkCert $cert
    exit
}

# You can check the key type to make sure it's RSA.
# This will output "rsa" if the key is RSA.
puts "Key type = [CkPrivateKey_keyType $privKey]"

# Create the JWS Protected Header
set jwsProtHdr [new_CkJsonObject]

CkJsonObject_AppendString $jwsProtHdr "alg" "RS256"

set jws [new_CkJws]

# Set the protected header:
set signatureIndex 0
CkJws_SetProtectedHeader $jws $signatureIndex $jwsProtHdr

# Set the RSA key:
CkJws_SetPrivateKey $jws $signatureIndex $privKey

# Set the payload.
set bIncludeBom 0
set payloadStr "In our village, folks say God crumbles up the old moon into stars."
CkJws_SetPayload $jws $payloadStr "utf-8" $bIncludeBom

# Create the JWS
# By default, the compact serialization is used.
set jwsCompact [CkJws_createJws $jws]
if {[CkJws_get_LastMethodSuccess $jws] != 1} then {
    puts [CkJws_lastErrorText $jws]
    delete_CkPrivateKey $privKey

    delete_CkCert $cert
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    exit
}

puts "JWS: $jwsCompact"

# sample output:
# JWS: eyJhbGciOiJQUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.TRWhwRo5dMv9-8OzrInfJTwmUGYgjLfHk8lqF072ND-FmLWEBnUTOpY8oJXp8FdWw2SalbdOeNlrtlJjwk4XK8Ql2iJ_2qMCtxsvLPhKBOqFoAF4aBvTOEDVJDxf0DaBSiydEEtfTVV2iwBcjWabu5J2XieR5y7QZQtuHsn7T3qKBvCcCejN3Y2oqAT3qMHvu1fTms1r_91wBn_K7Wjd9UkZ1n02qQcUHJznR_OF2BgN7_KWIDAF9ZS9keoju2NPpPelO4yxa2XUPnehY3G7dHKoCxUEQR4d2Xc5voqDASTVCDqQS4PVOZdvT3Ein6-SanAlCwbWBbkvT8g6-5PImQ

# Now load the JWS, validate, and recover the original text.
set jws2 [new_CkJws]

# Load the JWS.
set success [CkJws_LoadJws $jws2 $jwsCompact]

# rsaPubKey is a CkPublicKey
set rsaPubKey [CkPrivateKey_GetPublicKey $privKey]
delete_CkPrivateKey $privKey

# Set the RSA public key used for validation.
set signatureIndex 0
CkJws_SetPublicKey $jws2 $signatureIndex $rsaPubKey
delete_CkPublicKey $rsaPubKey

# Validate the 1st (and only) signature at index 0..
set v [CkJws_Validate $jws2 $signatureIndex]
if {$v < 0} then {
    # Perhaps Chilkat was not unlocked or the trial expired..
    puts "Method call failed for some other reason."
    puts [CkJws_lastErrorText $jws2]
    delete_CkCert $cert
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

if {$v == 0} then {
    puts "Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both."
    delete_CkCert $cert
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

# If we get here, the signature was validated..
puts "Signature validated."

# Recover the original content:
puts [CkJws_getPayload $jws2 utf-8]

# Examine the protected header:
# joseHeader is a CkJsonObject
set joseHeader [CkJws_GetProtectedHeader $jws2 $signatureIndex]
if {[CkJws_get_LastMethodSuccess $jws2] != 1} then {
    puts "No protected header found at the given index."
    delete_CkCert $cert
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

CkJsonObject_put_EmitCompact $joseHeader 0

puts "Protected (JOSE) header:"
puts [CkJsonObject_emit $joseHeader]
delete_CkJsonObject $joseHeader

# Output:

# 	Signature validated.
# 	In our village, folks say God crumbles up the old moon into stars.
# 	Protected (JOSE) header:
# 	{ 
# 	  "alg": "RS256"
# 	}

delete_CkCert $cert
delete_CkJsonObject $jwsProtHdr
delete_CkJws $jws
delete_CkJws $jws2