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How to sign XML documents using XMLDSig (XML Signature)

Tagged xml, signature, xmldsig, wtf, hl7fi, kanta, xmlsec1  Languages bash, xml

Install xmlsec1

sudo apt-get install xmlsec1

Create document

<?xml version="1.0" encoding="UTF-8"?>
  <hello>All XML is doomed to fail.</hello>
  <!-- Signature contains the signature definition -->
  <Signature xmlns="">
      <CanonicalizationMethod Algorithm=""/>
      <SignatureMethod Algorithm=""/>
          <Transform Algorithm=""/>
          <Transform Algorithm=""/>
        <DigestMethod Algorithm=""/>
        <DigestValue />
    <SignatureValue />
      <X509Data />

Sign document

xmlsec1 --sign --privkey-pem, --output signed.xml tosign.xml

This example uses test certificates issued by VRK.

Verify document

xmlsec1 --verify --trusted-pem vrkthsp.pem --trusted-pem vrktestc.pem signed.xml

Note that a concatenated PEM file, i.e. cat vrkthsp.pem vrktestc.pem > concat.pem, does not work with xmlsec1.

How to specify which elements to sign with ds:Reference

Add one or more ds:Reference elements to specify which elements should be signed. Each element should have a unique ID in the URI attribute. The ID should be prefixed with a hash, e.g., #your-id:

<ds:Reference URI="#secret-xml-sauce">

Make sure your document contains an element having the exact ID without the hash prefix:

<Dog ID="secret-xml-sauce" name="Christian" />

Next, use the “—id-attr” switch to specify the element and attribute name:

xmlsec1 --sign --privkey-pem signing.key,signing.pem --id-attr:ID Dog --id-attr:ID structuredBody --output signed.xml tosign.xml

Note that “id” is the default attribute name. You only need —id-attr switch if you have the ID in an attribute having a different name.

How to sign multiple elements

Just add another “—id-attr: ” switch:

xmlsec1 --sign --privkey-pem signing.key,signing.pem --id-attr:ID signatureTimestamp --id-attr:ID structuredBody --output signed.xml tosign.xml

Then add another element having the given ID.


  • This error means you don’t have the correct trusted pem
certificate issuer check failed:err=2;msg=unable to get issuer certificate;issuer=/C=FI/ST=Finland/O=Vaestorekisterikeskus TEST/OU=Certification Authority Services/OU=Varmennepalvelut/CN=VRK TEST Root CA

To fix the error, take a hard look at the Issuer and Subject of all certificates in the certificate chain. For example:

openssl x509 -inform DER -in vrktestc.crt -text | grep "Issuer\|Subject"
  • xmlsec1 fails to find element containing ID
func=xmlSecXPathDataExecute:file=xpath.c:line=273:obj=unknown:subj=xmlXPtrEval:error=5:libxml2 library function failed:expr=xpointer(id('ID_OF_ELEMENT_TO_SIGN'))

Note that the XPATH queries are case sensitive. This means you might have to specify both the name of the element and the name of the ID attribute like this:

xmlsec1 sign --id-attr:ID elementThatYouWantToSign ...

For more solutions to issues, see