(CkPython) Create XML Digital Signature using Certificate on Smart Card

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Demonstrates how to load a certificate located on a smart card or USB token and then use it for creating an XML digital signature such that the cryptographic signing happens on the smart card.

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

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

scmd = chilkat.CkScMinidriver()

# Reader names (smart card readers or USB tokens) can be discovered
# via List Readers or Find Smart Cards
readerName = "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0"
success = scmd.AcquireContext(readerName)
if (success == False):
    print(scmd.lastErrorText())
    sys.exit()

# If successful, the name of the currently inserted smart card is available:
print("Card name: " + scmd.cardName())

# If desired, perform regular PIN authentication with the smartcard.
# For more details about smart card PIN authentication, see the Smart Card PIN Authentication Example
retval = scmd.PinAuthenticate("user","000000")
if (retval != 0):
    print("PIN Authentication failed.")

# You can find a cerficate using any of the following certificate parts:
# "subjectDN" -- The full distinguished name of the cert.
# "subjectDN_withTags" -- Same as above, but in a format that includes the subject part tags, such as the "CN=" in "CN=something"
# "subjectCN" -- The common name part (CN) of the certificate's subject.
# "serial" -- The certificate serial number.
# "serial:issuerCN" -- The certificate serial number + the issuer's common name, delimited with a colon char.
# These are the same certificate parts that can be retrieved by listing certificates on the smart card (or USB token).
# See List Certificates on Smart Card Example
certPart = "subjectCN"
partValue = "PIVKey E42D60A759D39147A26E0AF2FB1183C5"

# If the certificate is found, it is loaded into the cert object.
cert = chilkat.CkCert()
success = scmd.FindCert(certPart,partValue,cert)
if (success == False):
    print("Failed to find the certificate.")
    scmd.DeleteContext()
    sys.exit()

print("Successfully loaded the cert object from the smart card / USB token.")

# Note: When successful, the cert object is internally linked to the ScMinidriver object's authenticated session.
# The cert object can now be used to sign or do other cryptographic operations that occur on the smart card / USB token.
# If your application calls PinDeauthenticate or DeleteContext, the cert will no longer be able to sign on the smart card
# because the smart card ScMinidriver session will no longer be authenticated or deleted.

# ------------------------------------------------------------------------------------------------------------
# We have the certificate.  Now let's do the XML digital signature..

# Create the following XML to be signed:

# <?xml version="1.0" encoding="UTF-8" standalone="no" ?>
# <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
#     <SOAP-ENV:Header>
#         <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" SOAP-ENV:mustUnderstand="1"></wsse:Security>
#     </SOAP-ENV:Header>
#     <SOAP-ENV:Body xmlns:SOAP-SEC="http://schemas.xmlsoap.org/soap/security/2000-12" SOAP-SEC:id="Body">
#         <z:FooBar xmlns:z="http://example.com" />
#     </SOAP-ENV:Body>
# </SOAP-ENV:Envelope>

xml = chilkat.CkXml()
xml.put_Tag("SOAP-ENV:Envelope")
xml.AddAttribute("xmlns:SOAP-ENV","http://schemas.xmlsoap.org/soap/envelope/")
xml.UpdateAttrAt("SOAP-ENV:Header|wsse:Security",True,"xmlns:wsse","http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd")
xml.UpdateAttrAt("SOAP-ENV:Header|wsse:Security",True,"SOAP-ENV:mustUnderstand","1")
xml.UpdateAttrAt("SOAP-ENV:Body",True,"xmlns:SOAP-SEC","http://schemas.xmlsoap.org/soap/security/2000-12")
xml.UpdateAttrAt("SOAP-ENV:Body",True,"SOAP-SEC:id","Body")
xml.UpdateAttrAt("SOAP-ENV:Body|z:FooBar",True,"xmlns:z","http://example.com")

# Prepare for signing...
gen = chilkat.CkXmlDSigGen()

# Indicate where the Signature will be inserted.
gen.put_SigLocation("SOAP-ENV:Envelope|SOAP-ENV:Header|wsse:Security")

# Add a reference to the fragment of the XML to be signed.

# Note: "Body" refers to the XML element having an "id" equal to "Body", where "id" is case insensitive
# and where any namespace might qualify the attribute.  In this case, the SOAP-ENV:Body fragment is signed
# NOT because the tag = "Body", but because it has SOAP-SEC:id="Body"
gen.AddSameDocRef("Body","sha1","EXCL_C14N","","")

# (You can read about the SignedInfoPrefixList in the online reference documentation.  It's optional..)
gen.put_SignedInfoPrefixList("wsse SOAP-ENV")

# Provide the private key for signing via the certificate, and indicate that
# we want the base64 of the certificate embedded in the KeyInfo.
gen.put_KeyInfoType("X509Data")
gen.put_X509Type("Certificate")

# Note: Our certificate was loaded from the smartcard and is internally linked to the authenticated ScMinidriver session.
# The signing will occur on the smart card using the chosen certificate.
bUsePrivateKey = True
success = gen.SetX509Cert(cert,bUsePrivateKey)
if (success != True):
    print(gen.lastErrorText())
    sys.exit()

# Everything's specified.  Now create and insert the Signature
sbXml = chilkat.CkStringBuilder()
xml.GetXmlSb(sbXml)
success = gen.CreateXmlDSigSb(sbXml)
if (success != True):
    print(gen.lastErrorText())
    sys.exit()

# Examine the XML with the digital signature inserted
print(sbXml.getAsString())

# ------------------------------------------------------------------------------------------------------------
# Cleanup our ScMinidriver session...

# When finished with operations that required authentication, you may if you wish, deauthenticate the session.
success = scmd.PinDeauthenticate("user")
if (success == False):
    print(scmd.lastErrorText())

# Delete the context when finished with the card.
success = scmd.DeleteContext()
if (success == False):
    print(scmd.lastErrorText())