(Tcl) Create XML Signature with External XML Reference

Demonstrates how to create an XML digital signature where the referenced data is external. In this case, the data is an XML file located at the following URL: https://www.chilkatsoft.com/data/helloWorld.xml

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load ./chilkat.dll

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

# This example inserts an XML signature in the following XML:

# <?xml version="1.0" encoding="UTF-8" standalone="no"?>
# <abc>
#   <xyz>
# 	<name>helloWorld.xml</name>
# 	<url>https://www.chilkatsoft.com/data/helloWorld.xml</url>
#   </xyz>
# </abc>

# Build the above XML to be signed.
set xml [new_CkXml]

CkXml_put_Tag $xml "abc"
CkXml_UpdateChildContent $xml "xyz|name" "helloWorld.xml"
CkXml_UpdateChildContent $xml "xyz|url" "https://www.chilkatsoft.com/data/helloWorld.xml"

set cert [new_CkCert]

set success [CkCert_LoadPfxFile $cert "qa_data/pfx/test_secret.pfx" "secret"]
if {$success == 0} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkXml $xml
    delete_CkCert $cert
    exit
}

set gen [new_CkXmlDSigGen]

# Indicate the location within the XML the Signature will be inserted.
CkXmlDSigGen_put_SigLocation $gen "abc|xyz"

# Get the content of the XML data to be referenced.
set http [new_CkHttp]

set sbExternalXml [new_CkStringBuilder]

set success [CkHttp_QuickGetSb $http "https://www.chilkatsoft.com/data/helloWorld.xml" $sbExternalXml]
if {$success == 0} then {
    puts [CkHttp_lastErrorText $http]
    delete_CkXml $xml
    delete_CkCert $cert
    delete_CkXmlDSigGen $gen
    delete_CkHttp $http
    delete_CkStringBuilder $sbExternalXml
    exit
}

set success [CkXmlDSigGen_AddExternalXmlRef $gen "https://www.chilkatsoft.com/data/helloWorld.xml" $sbExternalXml "sha256" "EXCL_C14N" ""]
if {$success == 0} then {
    puts [CkXmlDSigGen_lastErrorText $gen]
    delete_CkXml $xml
    delete_CkCert $cert
    delete_CkXmlDSigGen $gen
    delete_CkHttp $http
    delete_CkStringBuilder $sbExternalXml
    exit
}

# Provide the private key for signing via the certificate, and indicate that
# we want the base64 of the certificate embedded in the KeyInfo.
CkXmlDSigGen_put_KeyInfoType $gen "X509Data"
CkXmlDSigGen_put_X509Type $gen "Certificate"

set bUsePrivateKey 1
set success [CkXmlDSigGen_SetX509Cert $gen $cert $bUsePrivateKey]
if {$success != 1} then {
    puts [CkXmlDSigGen_lastErrorText $gen]
    delete_CkXml $xml
    delete_CkCert $cert
    delete_CkXmlDSigGen $gen
    delete_CkHttp $http
    delete_CkStringBuilder $sbExternalXml
    exit
}

# Indicate we want an indented signature for readability.
# This can be removed after debugging is finished..
CkXmlDSigGen_put_Behaviors $gen "IndentedSignature"

# Now create and insert the Signature
set sbXml [new_CkStringBuilder]

CkXml_GetXmlSb $xml $sbXml
set success [CkXmlDSigGen_CreateXmlDSigSb $gen $sbXml]
if {$success != 1} then {
    puts [CkXmlDSigGen_lastErrorText $gen]
    delete_CkXml $xml
    delete_CkCert $cert
    delete_CkXmlDSigGen $gen
    delete_CkHttp $http
    delete_CkStringBuilder $sbExternalXml
    delete_CkStringBuilder $sbXml
    exit
}

# Examine the XML with the digital signature inserted
puts [CkStringBuilder_getAsString $sbXml]

# Here is the output:

# <?xml version="1.0" encoding="utf-8"?>
# <abc>
#     <xyz>
#         <name>helloWorld.xml</name>
#         <url>https://www.chilkatsoft.com/data/helloWorld.xml</url>
#     <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
#   <ds:SignedInfo>
#     <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
#     <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/>
#     <ds:Reference URI="https://www.chilkatsoft.com/data/helloWorld.xml">
#       <ds:Transforms>
#         <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
#       </ds:Transforms>
#       <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
#       <ds:DigestValue>H/s775OZhel6wdBhe02l4LK6m0lkplOisKxAbVwWxp0=</ds:DigestValue>
#     </ds:Reference>
#   </ds:SignedInfo>
#   <ds:SignatureValue>UruwnBqh..Ll4IzUA==</ds:SignatureValue>
#   <ds:KeyInfo>
#     <ds:X509Data>
#       <ds:X509Certificate>MIIHAz...nUZWCaDE=</ds:X509Certificate>
#     </ds:X509Data>
#   </ds:KeyInfo>
# </ds:Signature></xyz>
# </abc>

# Let's verify the signature...
set verifier [new_CkXmlDSig]

set success [CkXmlDSig_LoadSignatureSb $verifier $sbXml]
if {$success != 1} then {
    puts [CkXmlDSig_lastErrorText $verifier]
    delete_CkXml $xml
    delete_CkCert $cert
    delete_CkXmlDSigGen $gen
    delete_CkHttp $http
    delete_CkStringBuilder $sbExternalXml
    delete_CkStringBuilder $sbXml
    delete_CkXmlDSig $verifier
    exit
}

# Let's examine the external references, and fetch the data for each..
set sbExternalData [new_CkStringBuilder]

set numRefs [CkXmlDSig_get_NumReferences $verifier]
set i 0
while {$i < $numRefs} {
    set bExternal [CkXmlDSig_IsReferenceExternal $verifier $i]
    if {$bExternal == 1} then {
        set uri [CkXmlDSig_referenceUri $verifier $i]

        # We're assuming the URI is an https:// or http:// URL...
        # Let's also assume we know that the referenced data is text and we want the utf-8 byte representation.
        CkStringBuilder_Clear $sbExternalData
        set success [CkHttp_QuickGetSb $http $uri $sbExternalData]
        if {$success == 0} then {
            puts [CkHttp_lastErrorText $http]
            delete_CkXml $xml
            delete_CkCert $cert
            delete_CkXmlDSigGen $gen
            delete_CkHttp $http
            delete_CkStringBuilder $sbExternalXml
            delete_CkStringBuilder $sbXml
            delete_CkXmlDSig $verifier
            delete_CkStringBuilder $sbExternalData
            exit
        }

        # Because the referenced external data was explicitly XML, it was the canonicalized XML that was digested.
        # We need to canonicalize the XML in the same way as when signed.
        set canonXml [CkXmlDSig_canonicalizeXml $verifier [CkStringBuilder_getAsString $sbExternalData] "EXCL_C14N" 0]
        CkStringBuilder_SetString $sbExternalData $canonXml

        set success [CkXmlDSig_SetRefDataSb $verifier $i $sbExternalData "utf-8"]
        if {$success == 0} then {
            puts [CkXmlDSig_lastErrorText $verifier]
            delete_CkXml $xml
            delete_CkCert $cert
            delete_CkXmlDSigGen $gen
            delete_CkHttp $http
            delete_CkStringBuilder $sbExternalXml
            delete_CkStringBuilder $sbXml
            delete_CkXmlDSig $verifier
            delete_CkStringBuilder $sbExternalData
            exit
        }

    }

    set i [expr $i + 1]
}

# Now that we have the external data available, we can verify the reference digest(s) and the signature.
set bVerified [CkXmlDSig_VerifySignature $verifier 1]
if {$bVerified != 1} then {
    puts [CkXmlDSig_lastErrorText $verifier]
    delete_CkXml $xml
    delete_CkCert $cert
    delete_CkXmlDSigGen $gen
    delete_CkHttp $http
    delete_CkStringBuilder $sbExternalXml
    delete_CkStringBuilder $sbXml
    delete_CkXmlDSig $verifier
    delete_CkStringBuilder $sbExternalData
    exit
}

puts "Signature verified!"

delete_CkXml $xml
delete_CkCert $cert
delete_CkXmlDSigGen $gen
delete_CkHttp $http
delete_CkStringBuilder $sbExternalXml
delete_CkStringBuilder $sbXml
delete_CkXmlDSig $verifier
delete_CkStringBuilder $sbExternalData