(Ruby) Create XML Digital Signature using a DSA Key

Demonstrates how to create an XML digital signature using a DSA key.

This example requires Chilkat v9.5.0.69 or greater.

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install from rubygems.org
gem install chilkat
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require 'chilkat'

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

# The XML to be signed in this example contains the following:

# <?xml version="1.0" encoding="UTF-8" standalone="no"?>
# <Envelope>
#   <Header>
#     <Security>
#     </Security>
#   </Header>
#   <Body Id="abc">
#     <z:FooBar xmlns:z="https://www.example-code.com"/>
#   </Body>
# </Envelope>

# The above XML is available at https://www.chilkatsoft.com/exampleData/xmlToSign.xml
# Fetch the XML and then sign it..

url = "https://www.chilkatsoft.com/exampleData/xmlToSign.xml"
http = Chilkat::CkHttp.new()
sbXml = Chilkat::CkStringBuilder.new()
success = http.QuickGetSb(url,sbXml)
if (success != true)
    print http.lastErrorText() + "\n";
    exit
end

# This example uses a DSA private key for signing.  
# There are many ways of getting an DSA private key using Chilkat.  This example
# will load it from an encrypted PEM file.

# In case you would like to use it, I put the DSA private key PEM file here:
# https://www.chilkatsoft.com/exampleData/dsa1024_secret.zip
# The password is "secret".
dsaKey = Chilkat::CkPrivateKey.new()
success = dsaKey.LoadEncryptedPemFile("qa_data/dsa/dsa1024_secret.pem","secret")
if (success != true)
    print dsaKey.lastErrorText() + "\n";
    exit
end

# To create the XML digital signature (i.e. embed the signature within
# the XML), first specify what is desired, then call the method to 
# create the XML signature.
# 
# For example, the application must provide the following:
#     - Where to put the signature.
#     - What to sign.
#     - The algorithms to be used.
#     - The key to be used for signing.
# 

xmlSigGen = Chilkat::CkXmlDSigGen.new()

# In this example, we're going to put the signature within the Security element.
# To specify the location, set the SigLocation property to the XML path to this element,
# using vertical bar characters to separate tags.
xmlSigGen.put_SigLocation("Envelope|Header|Security")

# An XML digital signature contains one or more references.  These can be references to the parts
# of the XML document to be signed (a same document reference), or can be external references.
# This example will add a single same-document reference.  We'll add a reference to the XML fragment
# at Body, which is indicated by providing the value of the "ID" attribute (where "ID" is case
# insensitive).  In this case, we specify "abc" because Body has an Id="abc".
# This causes the <Body> ... </Body> XML fragment to be signed.
# 
# For each same-document reference, we must also indicate the hash algorithm and XML canonicalization
# algorithm to be used.  For this example we'll choose SHA1 and Exclusive XML Canonicalization.
xmlSigGen.AddSameDocRef("abc","sha1","EXCL_C14N","","")

# Provide the DSA key to be used for signing:
xmlSigGen.SetPrivateKey(dsaKey)

# We're leaving the following properties at their default values:
# 
#    - SigNamespacePrefix (default is "ds")
#    - SignedInfoCanonAlg  (default is EXCL_C14N)
#    - KeyInfoType (default is "KeyValue", where the DSA public key is included in the Signature)

# Note: Each Reference has it's own specified algorithms for XML canonicalization and hashing,
# and the actual signature part (the SignedInfo) has it's own hash/canonicalization algorithm.
# They may or may not be the same.  In this example, we use Exclusive XML Canonicalization and SHA1 throughout.

# The default SignedInfoDigestMethod is sha256, which is a good choice.  This example will
# change it to sha1.
xmlSigGen.put_SignedInfoDigestMethod("sha1")

# OK, everything's specified, so let's create the XML digital signature:
# This in-place signs the XML.  If successful, sbXml will contain the 
# XML with the digital signature at the specified location.
success = xmlSigGen.CreateXmlDSigSb(sbXml)
if (success != true)
    print xmlSigGen.lastErrorText() + "\n";
    exit
end

# Examine the signed XML:
print sbXml.getAsString() + "\n";

# Below is the signed XML that is produced.
# Chilkat emits the Signature in compact form on a single line.  Whitespace in XML signatures
# matters.  Chilkat's opinion is that writing the Signature without whitespace minimizes the chance
# for problems with whatever software might be verifying the signature.

# <?xml version="1.0" encoding="UTF-8" standalone="no"?>
# <Envelope>
#   <Header>
#     <Security>
#     <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/2000/09/xmldsig#dsa-sha1"/><ds:Reference URI="#abc"><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/><ds:DigestValue>77X3L6odxTBow1W1dIiqZW1foow=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>Ci/KiAqoQLvNyK94n8TJwdJ6dVpIIy8tJg+9s8utmB92cW8lTd+U7g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:DSAKeyValue><ds:P>AN+Af9FvnqYl84Own8m/MHza9vVFEbpySOiWyeIM8diDjaES9i+UykaX9BGc0oaRJHtrHhe+gboMBGHfP+gYcgbqzeyVCi2kHghRD/TK7uI4jN8Yv8tfM6AO0QrDFfxFq4IV+qTZbSoCkbWaopQ+kEOY6B4btFxJ1YuE48mExMZ3</ds:P><ds:Q>AOCv5pwf4kvMW37Yzt0iH6URKOlD</ds:Q><ds:G>FO3eoDcpuU9Z25OQGFtC+M2ifczcKyRkFwTauGR3mIw0wePPiu3Ocr7A81SA8GQ9x3hWO5jyP//jL3jxYy8fgBg2RXwiic3nwT2rZfu50g6tPUpz1stKz/+Mxjulo6XuaMSOWwjU021IxVMzxQ1/L8QiwiIrwxvfQOaMY8HJgvw=</ds:G><ds:Y>JJmZQvWtrZ+Nb2YV47SfGAave8uOIedGlmg+CseoqKZC2aFcWM6kR0giUwQx834dhxQScRhqzxFxQPk/x+5hyG8LQbXW+BELmT1BiyodobYUAet4rSIt4EU4KU0iYw1drpcWT1jqI07l5xNi28heYSfSF5Odv2qwXxVKDSEeEkM=</ds:Y></ds:DSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></Security>
#   </Header>
#   <Body Id="abc">
#     <z:FooBar xmlns:z="https://www.example-code.com"/>
#   </Body>
# </Envelope>

# The above signed XML contains the DSA public key in the DSAKeyValue fragment (within the ds:KeyInfo).
# The signature can easily be verified like this:

verifier = Chilkat::CkXmlDSig.new()

# First load the XML containing the signature(s) to be verified.
success = verifier.LoadSignatureSb(sbXml)
if (success != true)
    print verifier.lastErrorText() + "\n";
    exit
end

bVerified = verifier.VerifySignature(true)
if (bVerified != true)
    print verifier.lastErrorText() + "\n";
end

print "Signature verified = " + bVerified.to_s() + "\n";