nokogiri-xmlsec

Adds support to Ruby for encrypting, decrypting, signing and validating the signatures of XML documents, according to the XML Encryption Syntax and Processing standard, by wrapping around the xmlsec C library and adding relevant methods to Nokogiri::XML::Document.

Installation

Add this line to your application's Gemfile:

gem 'nokogiri-xmlsec'

And then execute:

$ bundle

Or install it yourself as:

$ gem install nokogiri-xmlsec

Usage

Several methods are added to Nokogiri::XML::Document which expose this gem's functionality.

Signing

The sign! method adds a digital signature to the XML document so that it can later be determined whether the document itself has been tampered with. If the document changes, the signature will be invalid.

Signing a document will add XML nodes directly to the document itself, and then returns itself.

# First, get an XML document
doc = Nokogiri::XML("<doc><greeting>Hello, World!</greeting></doc>")

# Sign the document with a certificate, a key, and a key name
doc.sign! certificate: 'certificate data',
          key: 'private key data',
          name: 'private key name'

You only need one of certificate or key, but you can pass both. If you do, the certificate will be included as part of the signature, so that it can be later verified by certificate instead of by key.

The name is implicitly converted into a string. Thus it is effectively optional, since nil converts to "", and its value only matters if you plan to verify the signature with any of a set of keys, as in the following example:

Signature verification

Verification of signatures always returns true if successful, false otherwise.

# Verify the document's signature to ensure it has not been tampered with
doc.verify_with({
  'key-name-1' => 'public key contents',
  'key-name-2' => 'another public key content'
})

In the above example, the name field from the signing process will be used to determine which key to validate with. If you plan to always verify with the same key, you can do it like so, effectively ignoring the name value:

# Verify the document's signature with a specific key
doc.verify_with key: 'public key contents'

Finally, you can also verify with a certificate:

# Verify the document's signature with a single certificate
doc.verify_with certificate: 'certificate data'

# Verify the document's signature with multiple certificates. Any one match
# will pass verification.
doc.verify_with certificates: [ 'cert1', 'cert2', 'cert3' ]

If the certificate has been installed to your system certificates, then you can verify signatures like so:

# Verify with installed CA certificates
doc.verify_signature

Encryption & Decryption

Encrypted documents can only be decrypted with the private key that corresponds to the public key that was used to encrypt it. Thus, the party that encrypted the document can be sure that the document will only be readable by its intended recipient.

Both encryption and decryption of a document manipulates the XML nodes of the document in-place. Both methods return the original document, after the changes have been made to it.

To encrypt a document, use a public key:

doc.encrypt! key: 'public key content'

To decrypt a document, use a private key:

doc.decrypt! key: 'private key content'

Limitations and Known Issues

Following is a list of limitations and/or issues I know about, but have no immediate plan to resolve. This is probably because I haven't needed the functionality, and no one has sent a pull request. (Hint, hint!)

• Currently, it is not possible to operate on individual XML nodes. The nokogiri-xmlsec operations must be performed on the entire document.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request