cose-ruby

Ruby implementation of RFC 8152 CBOR Object Signing and Encryption (COSE)

Gem Travis

Installation

Add this line to your application's Gemfile:

gem 'cose'

And then execute:

$ bundle

Or install it yourself as:

$ gem install cose

Usage

Key Objects

Deserialization (from CBOR to Ruby objects)

cbor_data = "..."

key = COSE::Key.deserialize(cbor_data)

Once you have a COSE::Key instance you can either access key parameters directly and/or convert it to an OpenSSL::PKey::PKey instance (if supported for the key type) for operating with it (encrypting/decrypting, signing/verifying, etc).

# Convert to an OpenSSL::PKey::PKey
if key.respond_to?(:to_pkey)
  openssl_pkey = key.to_pkey
end

# Access COSE key parameters
case key
when COSE::Key::OKP
  key.crv
  key.x
  key.d
when COSE::Key::EC2
  key.crv
  key.x
  key.y
  key.d
when COSE::Key::RSA
  key.n
  key.e
  key.d
  key.p
  key.q
  key.dp
  key.dq
  key.qinv
when COSE::Key::Symmetric
  key.k
end

If you already know which COSE key type is encoded in the CBOR data, then:

okp_key_cbor = "..."

cose_okp_key = COSE::Key::OKP.deserialize(okp_key_cbor)

cose_okp_key.crv
cose_okp_key.x
cose_okp_key.d
ec2_key_cbor = "..."

cose_ec2_key = COSE::Key::EC2.deserialize(ec2_key_cbor)

cose_ec2_key.crv
cose_ec2_key.x
cose_ec2_key.y
cose_ec2_key.d

# or

ec_pkey = cose_ec2_key.to_pkey # Instance of an OpenSSL::PKey::EC
symmetric_key_cbor = "..."

cose_symmetric_key = COSE::Key::Symmetric.deserialize(symmetric_key_cbor)

cose_symmetric_key.k
rsa_key_cbor = "..."

cose_rsa_key = COSE::Key::RSA.deserialize(rsa_key_cbor)

cose_rsa_key.n
cose_rsa_key.e
cose_rsa_key.d
cose_rsa_key.p
cose_rsa_key.q
cose_rsa_key.dp
cose_rsa_key.dq
cose_rsa_key.qinv

# or

rsa_pkey = cose_rsa_key.to_pkey # Instance of an OpenSSL::PKey::RSA

Serialization (from Ruby objects to CBOR)

ec_pkey = OpenSSL::PKey::EC.new("prime256v1").generate_key

cose_ec2_key_cbor = COSE::Key.serialize(ec_pkey)
rsa_pkey = OpenSSL::PKey::RSA.new(2048)

cose_rsa_key_cbor = COSE::Key.serialize(rsa_pkey)

Signing Objects

COSE_Sign

cbor_data = "..."

sign = COSE::Sign.deserialize(cbor_data)

# Verify by doing (key should be a COSE::Key):
sign.verify(key)

# or, if externally supplied authenticated data exists:
sign.verify(key, external_aad)

# Then access payload
sign.payload

COSE_Sign1

cbor_data = "..."

sign1 = COSE::Sign1.deserialize(cbor_data)

# Verify by doing (key should be a COSE::Key):
sign1.verify(key)

# or, if externally supplied authenticated data exists:
sign1.verify(key, external_aad)

# Then access payload
sign1.payload

MAC Objects

COSE_Mac

cbor_data = "..."

mac = COSE::Mac.deserialize(cbor_data)

# Verify by doing (key should be a COSE::Key::Symmetric):
mac.verify(key)

# or, if externally supplied authenticated data exists:
mac.verify(key, external_aad)

# Then access payload
mac.payload

COSE_Mac0

cbor_data = "..."

mac0 = COSE::Mac0.deserialize(cbor_data)

# Verify by doing (key should be a COSE::Key::Symmetric):
mac0.verify(key)

# or, if externally supplied authenticated data exists:
mac0.verify(key, external_aad)

# Then access payload
mac0.payload

Encryption Objects

COSE_Encrypt

cbor_data = "..."

encrypt = COSE::Encrypt.deserialize(cbor_data)

encrypt.protected_headers
encrypt.unprotected_headers
encrypt.ciphertext

encrypt.recipients.each do |recipient|
  recipient.protected_headers
  recipient.unprotected_headers
  recipient.ciphertext

  if recipient.recipients
    recipient.recipients.each do |recipient|
      recipient.protected_headers
      recipient.unprotected_headers
      recipient.ciphertext
    end
  end
end

COSE_Encrypt0

cbor_data = "..."

encrypt0 = COSE::Encrypt0.deserialize(cbor_data)

encrypt0.protected_headers
encrypt0.unprotected_headers
encrypt0.ciphertext

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/cedarcode/cose-ruby.

License

The gem is available as open source under the terms of the MIT License.